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authorTravis Ralston <travpc@gmail.com>2021-02-02 07:26:36 -0700
committerTravis Ralston <travpc@gmail.com>2021-02-02 07:26:36 -0700
commit6ec034411cdad6f9f77f7dab7749d426ffd5744b (patch)
treed7935121ad99051eddf5769993bef674e618379e
parentAppease the linters (diff)
parentUpdate changelog (diff)
downloadsynapse-6ec034411cdad6f9f77f7dab7749d426ffd5744b.tar.xz
Merge branch 'develop' into travis/fosdem/admin-api-groups travis/fosdem/admin-api-groups
-rwxr-xr-x.buildkite/scripts/test_old_deps.sh3
-rw-r--r--CHANGES.md190
-rw-r--r--README.rst2
-rw-r--r--UPGRADE.rst104
-rw-r--r--changelog.d/8868.misc1
-rw-r--r--changelog.d/8932.feature1
-rw-r--r--changelog.d/8939.misc1
-rw-r--r--changelog.d/8948.feature1
-rw-r--r--changelog.d/8984.feature1
-rw-r--r--changelog.d/8997.doc1
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-rw-r--r--changelog.d/9018.misc1
-rw-r--r--changelog.d/9023.bugfix1
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-rw-r--r--changelog.d/9025.misc1
-rw-r--r--changelog.d/9028.bugfix1
-rw-r--r--changelog.d/9029.misc1
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-rw-r--r--changelog.d/9036.feature1
-rw-r--r--changelog.d/9038.misc1
-rw-r--r--changelog.d/9039.removal1
-rw-r--r--changelog.d/9040.doc1
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-rw-r--r--changelog.d/9043.feature1
-rw-r--r--changelog.d/9044.feature1
-rw-r--r--changelog.d/9051.bugfix1
-rw-r--r--changelog.d/9053.bugfix1
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-rw-r--r--changelog.d/9055.misc1
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-rw-r--r--changelog.d/9058.misc1
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-rw-r--r--changelog.d/9063.misc1
-rw-r--r--changelog.d/9067.feature1
-rw-r--r--changelog.d/9068.feature1
-rw-r--r--changelog.d/9069.misc1
-rw-r--r--changelog.d/9070.bugfix1
-rw-r--r--changelog.d/9071.bugfix1
-rw-r--r--changelog.d/9080.misc1
-rw-r--r--changelog.d/9081.feature1
-rw-r--r--changelog.d/9082.feature1
-rw-r--r--changelog.d/9086.feature1
-rw-r--r--changelog.d/9091.feature1
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-rw-r--r--changelog.d/9093.misc1
-rw-r--r--changelog.d/9098.misc1
-rw-r--r--changelog.d/9104.feature1
-rw-r--r--changelog.d/9105.feature1
-rw-r--r--changelog.d/9106.misc1
-rw-r--r--changelog.d/9107.feature1
-rw-r--r--changelog.d/9108.bugfix1
-rw-r--r--changelog.d/9109.feature1
-rw-r--r--changelog.d/9110.feature1
-rw-r--r--changelog.d/9112.misc1
-rw-r--r--changelog.d/9114.bugfix1
-rw-r--r--changelog.d/9115.misc1
-rw-r--r--changelog.d/9116.bugfix1
-rw-r--r--changelog.d/9117.bugfix1
-rw-r--r--changelog.d/9118.misc1
-rw-r--r--changelog.d/9124.misc1
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-rw-r--r--changelog.d/9130.feature1
-rw-r--r--changelog.d/9144.misc1
-rw-r--r--changelog.d/9145.bugfix1
-rw-r--r--changelog.d/9146.misc1
-rw-r--r--changelog.d/9151.doc1
-rw-r--r--changelog.d/9153.feature1
-rw-r--r--changelog.d/9157.misc1
-rw-r--r--changelog.d/9161.bugfix1
-rwxr-xr-xdebian/build_virtualenv4
-rw-r--r--debian/changelog14
-rw-r--r--docker/Dockerfile-dhvirtualenv1
-rw-r--r--docs/admin_api/rooms.md83
-rw-r--r--docs/admin_api/user_admin_api.rst30
-rw-r--r--docs/openid.md107
-rw-r--r--docs/sample_config.yaml173
-rw-r--r--docs/turn-howto.md6
-rw-r--r--docs/workers.md26
-rw-r--r--mypy.ini41
-rwxr-xr-xscripts-dev/lint.sh3
-rwxr-xr-xsetup.py3
-rw-r--r--stubs/txredisapi.pyi25
-rw-r--r--synapse/__init__.py2
-rw-r--r--synapse/api/urls.py2
-rw-r--r--synapse/app/_base.py3
-rw-r--r--synapse/app/generic_worker.py11
-rw-r--r--synapse/app/homeserver.py16
-rw-r--r--synapse/app/phone_stats_home.py9
-rw-r--r--synapse/config/_base.py90
-rw-r--r--synapse/config/_base.pyi6
-rw-r--r--synapse/config/captcha.py4
-rw-r--r--synapse/config/cas.py12
-rw-r--r--synapse/config/consent_config.py2
-rw-r--r--synapse/config/emailconfig.py8
-rw-r--r--synapse/config/experimental.py29
-rw-r--r--synapse/config/homeserver.py2
-rw-r--r--synapse/config/oidc_config.py108
-rw-r--r--synapse/config/ratelimiting.py32
-rw-r--r--synapse/config/registration.py25
-rw-r--r--synapse/config/saml2_config.py10
-rw-r--r--synapse/config/server.py26
-rw-r--r--synapse/config/sso.py97
-rw-r--r--synapse/crypto/context_factory.py13
-rw-r--r--synapse/federation/federation_client.py127
-rw-r--r--synapse/federation/federation_server.py2
-rw-r--r--synapse/federation/sender/__init__.py50
-rw-r--r--synapse/federation/transport/server.py2
-rw-r--r--synapse/handlers/acme.py12
-rw-r--r--synapse/handlers/acme_issuing_service.py27
-rw-r--r--synapse/handlers/auth.py38
-rw-r--r--synapse/handlers/cas_handler.py11
-rw-r--r--synapse/handlers/device.py12
-rw-r--r--synapse/handlers/e2e_keys.py223
-rw-r--r--synapse/handlers/e2e_room_keys.py91
-rw-r--r--synapse/handlers/federation.py9
-rw-r--r--synapse/handlers/groups_local.py83
-rw-r--r--synapse/handlers/identity.py30
-rw-r--r--synapse/handlers/message.py44
-rw-r--r--synapse/handlers/oidc_handler.py66
-rw-r--r--synapse/handlers/register.py7
-rw-r--r--synapse/handlers/room.py9
-rw-r--r--synapse/handlers/room_member.py25
-rw-r--r--synapse/handlers/saml_handler.py7
-rw-r--r--synapse/handlers/search.py38
-rw-r--r--synapse/handlers/set_password.py10
-rw-r--r--synapse/handlers/sso.py220
-rw-r--r--synapse/handlers/state_deltas.py14
-rw-r--r--synapse/handlers/stats.py39
-rw-r--r--synapse/handlers/typing.py69
-rw-r--r--synapse/handlers/user_directory.py9
-rw-r--r--synapse/http/endpoint.py79
-rw-r--r--synapse/http/server.py51
-rw-r--r--synapse/logging/opentracing.py2
-rw-r--r--synapse/module_api/__init__.py10
-rw-r--r--synapse/push/mailer.py313
-rw-r--r--synapse/push/presentable_names.py26
-rw-r--r--synapse/python_dependencies.py4
-rw-r--r--synapse/replication/tcp/external_cache.py105
-rw-r--r--synapse/replication/tcp/handler.py21
-rw-r--r--synapse/replication/tcp/redis.py143
-rw-r--r--synapse/res/templates/sso.css88
-rw-r--r--synapse/res/templates/sso_account_deactivated.html26
-rw-r--r--synapse/res/templates/sso_auth_account_details.html138
-rw-r--r--synapse/res/templates/sso_auth_account_details.js76
-rw-r--r--synapse/res/templates/sso_auth_bad_user.html27
-rw-r--r--synapse/res/templates/sso_auth_confirm.html32
-rw-r--r--synapse/res/templates/sso_auth_success.html39
-rw-r--r--synapse/res/templates/sso_error.html101
-rw-r--r--synapse/res/templates/sso_login_idp_picker.html13
-rw-r--r--synapse/res/templates/sso_new_user_consent.html39
-rw-r--r--synapse/res/templates/sso_redirect_confirm.html34
-rw-r--r--synapse/res/username_picker/index.html19
-rw-r--r--synapse/res/username_picker/script.js95
-rw-r--r--synapse/res/username_picker/style.css27
-rw-r--r--synapse/rest/admin/__init__.py8
-rw-r--r--synapse/rest/admin/rooms.py110
-rw-r--r--synapse/rest/admin/users.py57
-rw-r--r--synapse/rest/client/v1/login.py57
-rw-r--r--synapse/rest/client/v1/room.py3
-rw-r--r--synapse/rest/client/v2_alpha/account.py12
-rw-r--r--synapse/rest/client/v2_alpha/register.py6
-rw-r--r--synapse/rest/consent/consent_resource.py1
-rw-r--r--synapse/rest/media/v1/_base.py3
-rw-r--r--synapse/rest/media/v1/preview_url_resource.py44
-rw-r--r--synapse/rest/media/v1/thumbnail_resource.py236
-rw-r--r--synapse/rest/synapse/client/__init__.py54
-rw-r--r--synapse/rest/synapse/client/new_user_consent.py97
-rw-r--r--synapse/rest/synapse/client/oidc/__init__.py (renamed from synapse/rest/oidc/__init__.py)6
-rw-r--r--synapse/rest/synapse/client/oidc/callback_resource.py (renamed from synapse/rest/oidc/callback_resource.py)0
-rw-r--r--synapse/rest/synapse/client/pick_username.py101
-rw-r--r--synapse/rest/synapse/client/saml2/__init__.py (renamed from synapse/rest/saml2/__init__.py)8
-rw-r--r--synapse/rest/synapse/client/saml2/metadata_resource.py (renamed from synapse/rest/saml2/metadata_resource.py)0
-rw-r--r--synapse/rest/synapse/client/saml2/response_resource.py (renamed from synapse/rest/saml2/response_resource.py)0
-rw-r--r--synapse/rest/synapse/client/sso_register.py50
-rw-r--r--synapse/rest/well_known.py4
-rw-r--r--synapse/server.py30
-rw-r--r--synapse/server_notices/resource_limits_server_notices.py3
-rw-r--r--synapse/server_notices/server_notices_manager.py3
-rw-r--r--synapse/state/__init__.py11
-rw-r--r--synapse/storage/database.py11
-rw-r--r--synapse/storage/databases/main/__init__.py4
-rw-r--r--synapse/storage/databases/main/account_data.py2
-rw-r--r--synapse/storage/databases/main/devices.py4
-rw-r--r--synapse/storage/databases/main/end_to_end_keys.py4
-rw-r--r--synapse/storage/databases/main/event_push_actions.py4
-rw-r--r--synapse/storage/databases/main/events.py217
-rw-r--r--synapse/storage/databases/main/events_bg_updates.py12
-rw-r--r--synapse/storage/databases/main/events_forward_extremities.py101
-rw-r--r--synapse/storage/databases/main/media_repository.py10
-rw-r--r--synapse/storage/databases/main/metrics.py56
-rw-r--r--synapse/storage/databases/main/purge_events.py2
-rw-r--r--synapse/storage/databases/main/pusher.py4
-rw-r--r--synapse/storage/databases/main/receipts.py4
-rw-r--r--synapse/storage/databases/main/registration.py71
-rw-r--r--synapse/storage/databases/main/room.py6
-rw-r--r--synapse/storage/databases/main/roommember.py6
-rw-r--r--synapse/storage/databases/main/schema/delta/59/01ignored_user.py2
-rw-r--r--synapse/storage/databases/main/schema/delta/59/07shard_account_data_fix.sql18
-rw-r--r--synapse/storage/databases/main/search.py7
-rw-r--r--synapse/storage/databases/main/stats.py22
-rw-r--r--synapse/storage/databases/main/user_directory.py2
-rw-r--r--synapse/storage/databases/state/store.py4
-rw-r--r--synapse/storage/util/id_generators.py27
-rw-r--r--synapse/storage/util/sequence.py72
-rw-r--r--synapse/types.py2
-rw-r--r--synapse/util/iterutils.py2
-rw-r--r--synapse/util/module_loader.py3
-rw-r--r--synapse/util/stringutils.py92
-rw-r--r--synapse/util/templates.py106
-rw-r--r--tests/handlers/test_cas.py8
-rw-r--r--tests/handlers/test_federation.py93
-rw-r--r--tests/handlers/test_oidc.py39
-rw-r--r--tests/handlers/test_saml.py8
-rw-r--r--tests/http/test_endpoint.py2
-rw-r--r--tests/push/test_email.py30
-rw-r--r--tests/push/test_presentable_names.py229
-rw-r--r--tests/push/test_push_rule_evaluator.py2
-rw-r--r--tests/replication/_base.py41
-rw-r--r--tests/rest/admin/test_room.py15
-rw-r--r--tests/rest/admin/test_user.py287
-rw-r--r--tests/rest/client/test_shadow_banned.py8
-rw-r--r--tests/rest/client/v1/test_login.py124
-rw-r--r--tests/rest/client/v1/test_rooms.py35
-rw-r--r--tests/rest/client/v2_alpha/test_account.py90
-rw-r--r--tests/rest/client/v2_alpha/test_auth.py6
-rw-r--r--tests/rest/media/v1/test_media_storage.py25
-rw-r--r--tests/rest/test_well_known.py9
-rw-r--r--tests/server.py9
-rw-r--r--tests/test_preview.py29
-rw-r--r--tests/unittest.py5
-rw-r--r--tests/util/test_itertools.py12
-rw-r--r--tests/utils.py5
-rw-r--r--tox.ini20
241 files changed, 5364 insertions, 1725 deletions
diff --git a/.buildkite/scripts/test_old_deps.sh b/.buildkite/scripts/test_old_deps.sh
index 9905c4bc4f..28e6694b5d 100755
--- a/.buildkite/scripts/test_old_deps.sh
+++ b/.buildkite/scripts/test_old_deps.sh
@@ -10,4 +10,7 @@ apt-get install -y python3.5 python3.5-dev python3-pip libxml2-dev libxslt-dev x
 
 export LANG="C.UTF-8"
 
+# Prevent virtualenv from auto-updating pip to an incompatible version
+export VIRTUALENV_NO_DOWNLOAD=1
+
 exec tox -e py35-old,combine
diff --git a/CHANGES.md b/CHANGES.md
index db11de0e85..16c11ff0cb 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,193 @@
+Synapse 1.27.0rc1 (2021-02-02)
+==============================
+
+Note that this release includes a change in Synapse to use Redis as a cache ─ as well as a pub/sub mechanism ─ if Redis support is enabled. No action is needed by server administrators, and we do not expect resource usage of the Redis instance to change dramatically.
+
+This release also changes the callback URI for OpenID Connect (OIDC) identity providers. If your server is configured to use single sign-on via an OIDC/OAuth2 IdP, you may need to make configuration changes. Please review [UPGRADE.rst](UPGRADE.rst) for more details on these changes.
+
+This release also changes escaping of variables in the HTML templates for SSO or email notifications. If you have customised these templates, please review [UPGRADE.rst](UPGRADE.rst) for more details on these changes.
+
+
+Features
+--------
+
+- Add an admin API for getting and deleting forward extremities for a room. ([\#9062](https://github.com/matrix-org/synapse/issues/9062))
+- Add an admin API for retrieving the current room state of a room. ([\#9168](https://github.com/matrix-org/synapse/issues/9168))
+- Add experimental support for allowing clients to pick an SSO Identity Provider ([MSC2858](https://github.com/matrix-org/matrix-doc/pull/2858)). ([\#9183](https://github.com/matrix-org/synapse/issues/9183), [\#9242](https://github.com/matrix-org/synapse/issues/9242))
+- Add an admin API endpoint for shadow-banning users. ([\#9209](https://github.com/matrix-org/synapse/issues/9209))
+- Add ratelimits to the 3PID `/requestToken` APIs. ([\#9238](https://github.com/matrix-org/synapse/issues/9238))
+- Add support to the OpenID Connect integration for adding the user's email address. ([\#9245](https://github.com/matrix-org/synapse/issues/9245))
+- Add ratelimits to invites in rooms and to specific users. ([\#9258](https://github.com/matrix-org/synapse/issues/9258))
+- Improve the user experience of setting up an account via single-sign on. ([\#9262](https://github.com/matrix-org/synapse/issues/9262), [\#9272](https://github.com/matrix-org/synapse/issues/9272), [\#9275](https://github.com/matrix-org/synapse/issues/9275), [\#9276](https://github.com/matrix-org/synapse/issues/9276), [\#9277](https://github.com/matrix-org/synapse/issues/9277), [\#9286](https://github.com/matrix-org/synapse/issues/9286), [\#9287](https://github.com/matrix-org/synapse/issues/9287))
+- Add phone home stats for encrypted messages. ([\#9283](https://github.com/matrix-org/synapse/issues/9283))
+- Update the redirect URI for OIDC authentication. ([\#9288](https://github.com/matrix-org/synapse/issues/9288))
+
+
+Bugfixes
+--------
+
+- Fix spurious errors in logs when deleting a non-existant pusher. ([\#9121](https://github.com/matrix-org/synapse/issues/9121))
+- Fix a long-standing bug where Synapse would return a 500 error when a thumbnail did not exist (and auto-generation of thumbnails was not enabled). ([\#9163](https://github.com/matrix-org/synapse/issues/9163))
+- Fix a long-standing bug where an internal server error was raised when attempting to preview an HTML document in an unknown character encoding. ([\#9164](https://github.com/matrix-org/synapse/issues/9164))
+- Fix a long-standing bug where invalid data could cause errors when calculating the presentable room name for push. ([\#9165](https://github.com/matrix-org/synapse/issues/9165))
+- Fix bug where we sometimes didn't detect that Redis connections had died, causing workers to not see new data. ([\#9218](https://github.com/matrix-org/synapse/issues/9218))
+- Fix a bug where `None` was passed to Synapse modules instead of an empty dictionary if an empty module `config` block was provided in the homeserver config. ([\#9229](https://github.com/matrix-org/synapse/issues/9229))
+- Fix a bug in the `make_room_admin` admin API where it failed if the admin with the greatest power level was not in the room. Contributed by Pankaj Yadav. ([\#9235](https://github.com/matrix-org/synapse/issues/9235))
+- Prevent password hashes from getting dropped if a client failed threepid validation during a User Interactive Auth stage. Removes a workaround for an ancient bug in Riot Web <v0.7.4. ([\#9265](https://github.com/matrix-org/synapse/issues/9265))
+- Fix single-sign-on when the endpoints are routed to synapse workers. ([\#9271](https://github.com/matrix-org/synapse/issues/9271))
+
+
+Improved Documentation
+----------------------
+
+- Add docs for using Gitea as OpenID provider. ([\#9134](https://github.com/matrix-org/synapse/issues/9134))
+- Add link to Matrix VoIP tester for turn-howto. ([\#9135](https://github.com/matrix-org/synapse/issues/9135))
+- Add notes on integrating with Facebook for SSO login. ([\#9244](https://github.com/matrix-org/synapse/issues/9244))
+
+
+Deprecations and Removals
+-------------------------
+
+- The `service_url` parameter in `cas_config` is deprecated in favor of `public_baseurl`. ([\#9199](https://github.com/matrix-org/synapse/issues/9199))
+- Add new endpoint `/_synapse/client/saml2` for SAML2 authentication callbacks, and deprecate the old endpoint `/_matrix/saml2`. ([\#9289](https://github.com/matrix-org/synapse/issues/9289))
+
+
+Internal Changes
+----------------
+
+- Add tests to `test_user.UsersListTestCase` for List Users Admin API. ([\#9045](https://github.com/matrix-org/synapse/issues/9045))
+- Various improvements to the federation client. ([\#9129](https://github.com/matrix-org/synapse/issues/9129))
+- Speed up chain cover calculation when persisting a batch of state events at once. ([\#9176](https://github.com/matrix-org/synapse/issues/9176))
+- Add a `long_description_type` to the package metadata. ([\#9180](https://github.com/matrix-org/synapse/issues/9180))
+- Speed up batch insertion when using PostgreSQL. ([\#9181](https://github.com/matrix-org/synapse/issues/9181), [\#9188](https://github.com/matrix-org/synapse/issues/9188))
+- Emit an error at startup if different Identity Providers are configured with the same `idp_id`. ([\#9184](https://github.com/matrix-org/synapse/issues/9184))
+- Improve performance of concurrent use of `StreamIDGenerators`. ([\#9190](https://github.com/matrix-org/synapse/issues/9190))
+- Add some missing source directories to the automatic linting script. ([\#9191](https://github.com/matrix-org/synapse/issues/9191))
+- Precompute joined hosts and store in Redis. ([\#9198](https://github.com/matrix-org/synapse/issues/9198), [\#9227](https://github.com/matrix-org/synapse/issues/9227))
+- Clean-up template loading code. ([\#9200](https://github.com/matrix-org/synapse/issues/9200))
+- Fix the Python 3.5 old dependencies build. ([\#9217](https://github.com/matrix-org/synapse/issues/9217))
+- Update `isort` to v5.7.0 to bypass a bug where it would disagree with `black` about formatting. ([\#9222](https://github.com/matrix-org/synapse/issues/9222))
+- Add type hints to handlers code. ([\#9223](https://github.com/matrix-org/synapse/issues/9223), [\#9232](https://github.com/matrix-org/synapse/issues/9232))
+- Fix Debian package building on Ubuntu 16.04 LTS (Xenial). ([\#9254](https://github.com/matrix-org/synapse/issues/9254))
+- Minor performance improvement during TLS handshake. ([\#9255](https://github.com/matrix-org/synapse/issues/9255))
+- Refactor the generation of summary text for email notifications. ([\#9260](https://github.com/matrix-org/synapse/issues/9260))
+- Restore PyPy compatibility by not calling CPython-specific GC methods when under PyPy. ([\#9270](https://github.com/matrix-org/synapse/issues/9270))
+
+
+Synapse 1.26.0 (2021-01-27)
+===========================
+
+This release brings a new schema version for Synapse and rolling back to a previous
+version is not trivial. Please review [UPGRADE.rst](UPGRADE.rst) for more details
+on these changes and for general upgrade guidance.
+
+No significant changes since 1.26.0rc2.
+
+
+Synapse 1.26.0rc2 (2021-01-25)
+==============================
+
+Bugfixes
+--------
+
+- Fix receipts and account data not being sent down sync. Introduced in v1.26.0rc1. ([\#9193](https://github.com/matrix-org/synapse/issues/9193), [\#9195](https://github.com/matrix-org/synapse/issues/9195))
+- Fix chain cover update to handle events with duplicate auth events. Introduced in v1.26.0rc1. ([\#9210](https://github.com/matrix-org/synapse/issues/9210))
+
+
+Internal Changes
+----------------
+
+- Add an `oidc-` prefix to any `idp_id`s which are given in the `oidc_providers` configuration. ([\#9189](https://github.com/matrix-org/synapse/issues/9189))
+- Bump minimum `psycopg2` version to v2.8. ([\#9204](https://github.com/matrix-org/synapse/issues/9204))
+
+
+Synapse 1.26.0rc1 (2021-01-20)
+==============================
+
+This release brings a new schema version for Synapse and rolling back to a previous
+version is not trivial. Please review [UPGRADE.rst](UPGRADE.rst) for more details
+on these changes and for general upgrade guidance.
+
+Features
+--------
+
+- Add support for multiple SSO Identity Providers. ([\#9015](https://github.com/matrix-org/synapse/issues/9015), [\#9017](https://github.com/matrix-org/synapse/issues/9017), [\#9036](https://github.com/matrix-org/synapse/issues/9036), [\#9067](https://github.com/matrix-org/synapse/issues/9067), [\#9081](https://github.com/matrix-org/synapse/issues/9081), [\#9082](https://github.com/matrix-org/synapse/issues/9082), [\#9105](https://github.com/matrix-org/synapse/issues/9105), [\#9107](https://github.com/matrix-org/synapse/issues/9107), [\#9109](https://github.com/matrix-org/synapse/issues/9109), [\#9110](https://github.com/matrix-org/synapse/issues/9110), [\#9127](https://github.com/matrix-org/synapse/issues/9127), [\#9153](https://github.com/matrix-org/synapse/issues/9153), [\#9154](https://github.com/matrix-org/synapse/issues/9154), [\#9177](https://github.com/matrix-org/synapse/issues/9177))
+- During user-interactive authentication via single-sign-on, give a better error if the user uses the wrong account on the SSO IdP. ([\#9091](https://github.com/matrix-org/synapse/issues/9091))
+- Give the `public_baseurl` a default value, if it is not explicitly set in the configuration file. ([\#9159](https://github.com/matrix-org/synapse/issues/9159))
+- Improve performance when calculating ignored users in large rooms. ([\#9024](https://github.com/matrix-org/synapse/issues/9024))
+- Implement [MSC2176](https://github.com/matrix-org/matrix-doc/pull/2176) in an experimental room version. ([\#8984](https://github.com/matrix-org/synapse/issues/8984))
+- Add an admin API for protecting local media from quarantine. ([\#9086](https://github.com/matrix-org/synapse/issues/9086))
+- Remove a user's avatar URL and display name when deactivated with the Admin API. ([\#8932](https://github.com/matrix-org/synapse/issues/8932))
+- Update `/_synapse/admin/v1/users/<user_id>/joined_rooms` to work for both local and remote users. ([\#8948](https://github.com/matrix-org/synapse/issues/8948))
+- Add experimental support for handling to-device messages on worker processes. ([\#9042](https://github.com/matrix-org/synapse/issues/9042), [\#9043](https://github.com/matrix-org/synapse/issues/9043), [\#9044](https://github.com/matrix-org/synapse/issues/9044), [\#9130](https://github.com/matrix-org/synapse/issues/9130))
+- Add experimental support for handling `/keys/claim` and `/room_keys` APIs on worker processes. ([\#9068](https://github.com/matrix-org/synapse/issues/9068))
+- Add experimental support for handling `/devices` API on worker processes. ([\#9092](https://github.com/matrix-org/synapse/issues/9092))
+- Add experimental support for moving off receipts and account data persistence off master. ([\#9104](https://github.com/matrix-org/synapse/issues/9104), [\#9166](https://github.com/matrix-org/synapse/issues/9166))
+
+
+Bugfixes
+--------
+
+- Fix a long-standing issue where an internal server error would occur when requesting a profile over federation that did not include a display name / avatar URL. ([\#9023](https://github.com/matrix-org/synapse/issues/9023))
+- Fix a long-standing bug where some caches could grow larger than configured. ([\#9028](https://github.com/matrix-org/synapse/issues/9028))
+- Fix error handling during insertion of client IPs into the database. ([\#9051](https://github.com/matrix-org/synapse/issues/9051))
+- Fix bug where we didn't correctly record CPU time spent in `on_new_event` block. ([\#9053](https://github.com/matrix-org/synapse/issues/9053))
+- Fix a minor bug which could cause confusing error messages from invalid configurations. ([\#9054](https://github.com/matrix-org/synapse/issues/9054))
+- Fix incorrect exit code when there is an error at startup. ([\#9059](https://github.com/matrix-org/synapse/issues/9059))
+- Fix `JSONDecodeError` spamming the logs when sending transactions to remote servers. ([\#9070](https://github.com/matrix-org/synapse/issues/9070))
+- Fix "Failed to send request" errors when a client provides an invalid room alias. ([\#9071](https://github.com/matrix-org/synapse/issues/9071))
+- Fix bugs in federation catchup logic that caused outbound federation to be delayed for large servers after start up. Introduced in v1.8.0 and v1.21.0. ([\#9114](https://github.com/matrix-org/synapse/issues/9114), [\#9116](https://github.com/matrix-org/synapse/issues/9116))
+- Fix corruption of `pushers` data when a postgres bouncer is used. ([\#9117](https://github.com/matrix-org/synapse/issues/9117))
+- Fix minor bugs in handling the `clientRedirectUrl` parameter for SSO login. ([\#9128](https://github.com/matrix-org/synapse/issues/9128))
+- Fix "Unhandled error in Deferred: BodyExceededMaxSize" errors when .well-known files that are too large. ([\#9108](https://github.com/matrix-org/synapse/issues/9108))
+- Fix "UnboundLocalError: local variable 'length' referenced before assignment" errors when the response body exceeds the expected size. This bug was introduced in v1.25.0. ([\#9145](https://github.com/matrix-org/synapse/issues/9145))
+- Fix a long-standing bug "ValueError: invalid literal for int() with base 10" when `/publicRooms` is requested with an invalid `server` parameter. ([\#9161](https://github.com/matrix-org/synapse/issues/9161))
+
+
+Improved Documentation
+----------------------
+
+- Add some extra docs for getting Synapse running on macOS. ([\#8997](https://github.com/matrix-org/synapse/issues/8997))
+- Correct a typo in the `systemd-with-workers` documentation. ([\#9035](https://github.com/matrix-org/synapse/issues/9035))
+- Correct a typo in `INSTALL.md`. ([\#9040](https://github.com/matrix-org/synapse/issues/9040))
+- Add missing `user_mapping_provider` configuration to the Keycloak OIDC example. Contributed by @chris-ruecker. ([\#9057](https://github.com/matrix-org/synapse/issues/9057))
+- Quote `pip install` packages when extras are used to avoid shells interpreting bracket characters. ([\#9151](https://github.com/matrix-org/synapse/issues/9151))
+
+
+Deprecations and Removals
+-------------------------
+
+- Remove broken and unmaintained `demo/webserver.py` script. ([\#9039](https://github.com/matrix-org/synapse/issues/9039))
+
+
+Internal Changes
+----------------
+
+- Improve efficiency of large state resolutions. ([\#8868](https://github.com/matrix-org/synapse/issues/8868), [\#9029](https://github.com/matrix-org/synapse/issues/9029), [\#9115](https://github.com/matrix-org/synapse/issues/9115), [\#9118](https://github.com/matrix-org/synapse/issues/9118), [\#9124](https://github.com/matrix-org/synapse/issues/9124))
+- Various clean-ups to the structured logging and logging context code. ([\#8939](https://github.com/matrix-org/synapse/issues/8939))
+- Ensure rejected events get added to some metadata tables. ([\#9016](https://github.com/matrix-org/synapse/issues/9016))
+- Ignore date-rotated homeserver logs saved to disk. ([\#9018](https://github.com/matrix-org/synapse/issues/9018))
+- Remove an unused column from `access_tokens` table. ([\#9025](https://github.com/matrix-org/synapse/issues/9025))
+- Add a `-noextras` factor to `tox.ini`, to support running the tests with no optional dependencies. ([\#9030](https://github.com/matrix-org/synapse/issues/9030))
+- Fix running unit tests when optional dependencies are not installed. ([\#9031](https://github.com/matrix-org/synapse/issues/9031))
+- Allow bumping schema version when using split out state database. ([\#9033](https://github.com/matrix-org/synapse/issues/9033))
+- Configure the linters to run on a consistent set of files. ([\#9038](https://github.com/matrix-org/synapse/issues/9038))
+- Various cleanups to device inbox store. ([\#9041](https://github.com/matrix-org/synapse/issues/9041))
+- Drop unused database tables. ([\#9055](https://github.com/matrix-org/synapse/issues/9055))
+- Remove unused `SynapseService` class. ([\#9058](https://github.com/matrix-org/synapse/issues/9058))
+- Remove unnecessary declarations in the tests for the admin API. ([\#9063](https://github.com/matrix-org/synapse/issues/9063))
+- Remove `SynapseRequest.get_user_agent`. ([\#9069](https://github.com/matrix-org/synapse/issues/9069))
+- Remove redundant `Homeserver.get_ip_from_request` method. ([\#9080](https://github.com/matrix-org/synapse/issues/9080))
+- Add type hints to media repository. ([\#9093](https://github.com/matrix-org/synapse/issues/9093))
+- Fix the wrong arguments being passed to `BlacklistingAgentWrapper` from `MatrixFederationAgent`. Contributed by Timothy Leung. ([\#9098](https://github.com/matrix-org/synapse/issues/9098))
+- Reduce the scope of caught exceptions in `BlacklistingAgentWrapper`. ([\#9106](https://github.com/matrix-org/synapse/issues/9106))
+- Improve `UsernamePickerTestCase`. ([\#9112](https://github.com/matrix-org/synapse/issues/9112))
+- Remove dependency on `distutils`. ([\#9125](https://github.com/matrix-org/synapse/issues/9125))
+- Enforce that replication HTTP clients are called with keyword arguments only. ([\#9144](https://github.com/matrix-org/synapse/issues/9144))
+- Fix the Python 3.5 / old dependencies build in CI. ([\#9146](https://github.com/matrix-org/synapse/issues/9146))
+- Replace the old `perspectives` option in the Synapse docker config file template with `trusted_key_servers`. ([\#9157](https://github.com/matrix-org/synapse/issues/9157))
+
+
 Synapse 1.25.0 (2021-01-13)
 ===========================
 
diff --git a/README.rst b/README.rst
index af914d71a8..d872b11f57 100644
--- a/README.rst
+++ b/README.rst
@@ -286,7 +286,7 @@ We recommend using the demo which starts 3 federated instances running on ports
 
 (to stop, you can use `./demo/stop.sh`)
 
-If you just want to start a single instance of the app and run it directly:
+If you just want to start a single instance of the app and run it directly::
 
     # Create the homeserver.yaml config once
     python -m synapse.app.homeserver \
diff --git a/UPGRADE.rst b/UPGRADE.rst
index f750d17da2..22edfe0d60 100644
--- a/UPGRADE.rst
+++ b/UPGRADE.rst
@@ -85,6 +85,108 @@ for example:
      wget https://packages.matrix.org/debian/pool/main/m/matrix-synapse-py3/matrix-synapse-py3_1.3.0+stretch1_amd64.deb
      dpkg -i matrix-synapse-py3_1.3.0+stretch1_amd64.deb
 
+Upgrading to v1.27.0
+====================
+
+Changes to callback URI for OAuth2 / OpenID Connect
+---------------------------------------------------
+
+This version changes the URI used for callbacks from OAuth2 identity providers. If
+your server is configured for single sign-on via an OpenID Connect or OAuth2 identity
+provider, you will need to add ``[synapse public baseurl]/_synapse/client/oidc/callback``
+to the list of permitted "redirect URIs" at the identity provider.
+
+See `docs/openid.md <docs/openid.md>`_ for more information on setting up OpenID
+Connect.
+
+(Note: a similar change is being made for SAML2; in this case the old URI
+``[synapse public baseurl]/_matrix/saml2`` is being deprecated, but will continue to
+work, so no immediate changes are required for existing installations.)
+
+Changes to HTML templates
+-------------------------
+
+The HTML templates for SSO and email notifications now have `Jinja2's autoescape <https://jinja.palletsprojects.com/en/2.11.x/api/#autoescaping>`_
+enabled for files ending in ``.html``, ``.htm``, and ``.xml``. If you have customised
+these templates and see issues when viewing them you might need to update them.
+It is expected that most configurations will need no changes.
+
+If you have customised the templates *names* for these templates, it is recommended
+to verify they end in ``.html`` to ensure autoescape is enabled.
+
+The above applies to the following templates:
+
+* ``add_threepid.html``
+* ``add_threepid_failure.html``
+* ``add_threepid_success.html``
+* ``notice_expiry.html``
+* ``notice_expiry.html``
+* ``notif_mail.html`` (which, by default, includes ``room.html`` and ``notif.html``)
+* ``password_reset.html``
+* ``password_reset_confirmation.html``
+* ``password_reset_failure.html``
+* ``password_reset_success.html``
+* ``registration.html``
+* ``registration_failure.html``
+* ``registration_success.html``
+* ``sso_account_deactivated.html``
+* ``sso_auth_bad_user.html``
+* ``sso_auth_confirm.html``
+* ``sso_auth_success.html``
+* ``sso_error.html``
+* ``sso_login_idp_picker.html``
+* ``sso_redirect_confirm.html``
+
+Upgrading to v1.26.0
+====================
+
+Rolling back to v1.25.0 after a failed upgrade
+----------------------------------------------
+
+v1.26.0 includes a lot of large changes. If something problematic occurs, you
+may want to roll-back to a previous version of Synapse. Because v1.26.0 also
+includes a new database schema version, reverting that version is also required
+alongside the generic rollback instructions mentioned above. In short, to roll
+back to v1.25.0 you need to:
+
+1. Stop the server
+2. Decrease the schema version in the database:
+
+   .. code:: sql
+
+      UPDATE schema_version SET version = 58;
+
+3. Delete the ignored users & chain cover data:
+
+   .. code:: sql
+
+      DROP TABLE IF EXISTS ignored_users;
+      UPDATE rooms SET has_auth_chain_index = false;
+
+   For PostgreSQL run:
+
+   .. code:: sql
+
+      TRUNCATE event_auth_chain_links;
+      TRUNCATE event_auth_chains;
+
+   For SQLite run:
+
+   .. code:: sql
+
+      DELETE FROM event_auth_chain_links;
+      DELETE FROM event_auth_chains;
+
+4. Mark the deltas as not run (so they will re-run on upgrade).
+
+   .. code:: sql
+
+      DELETE FROM applied_schema_deltas WHERE version = 59 AND file = "59/01ignored_user.py";
+      DELETE FROM applied_schema_deltas WHERE version = 59 AND file = "59/06chain_cover_index.sql";
+
+5. Downgrade Synapse by following the instructions for your installation method
+   in the "Rolling back to older versions" section above.
+
 Upgrading to v1.25.0
 ====================
 
@@ -148,7 +250,7 @@ shown below:
 
           return {"localpart": localpart}
 
-Removal historical Synapse Admin API 
+Removal historical Synapse Admin API
 ------------------------------------
 
 Historically, the Synapse Admin API has been accessible under:
diff --git a/changelog.d/8868.misc b/changelog.d/8868.misc
deleted file mode 100644
index 346741d982..0000000000
--- a/changelog.d/8868.misc
+++ /dev/null
@@ -1 +0,0 @@
-Improve efficiency of large state resolutions.
diff --git a/changelog.d/8932.feature b/changelog.d/8932.feature
deleted file mode 100644
index a1d17394d7..0000000000
--- a/changelog.d/8932.feature
+++ /dev/null
@@ -1 +0,0 @@
-Remove a user's avatar URL and display name when deactivated with the Admin API.
diff --git a/changelog.d/8939.misc b/changelog.d/8939.misc
deleted file mode 100644
index bf94135fd5..0000000000
--- a/changelog.d/8939.misc
+++ /dev/null
@@ -1 +0,0 @@
-Various clean-ups to the structured logging and logging context code.
diff --git a/changelog.d/8948.feature b/changelog.d/8948.feature
deleted file mode 100644
index 3b06cbfa22..0000000000
--- a/changelog.d/8948.feature
+++ /dev/null
@@ -1 +0,0 @@
-Update `/_synapse/admin/v1/users/<user_id>/joined_rooms` to work for both local and remote users.
diff --git a/changelog.d/8984.feature b/changelog.d/8984.feature
deleted file mode 100644
index 4db629746e..0000000000
--- a/changelog.d/8984.feature
+++ /dev/null
@@ -1 +0,0 @@
-Implement [MSC2176](https://github.com/matrix-org/matrix-doc/pull/2176) in an experimental room version.
diff --git a/changelog.d/8997.doc b/changelog.d/8997.doc
deleted file mode 100644
index dd1a882301..0000000000
--- a/changelog.d/8997.doc
+++ /dev/null
@@ -1 +0,0 @@
-Add some extra docs for getting Synapse running on macOS.
diff --git a/changelog.d/9015.feature b/changelog.d/9015.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9015.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9016.misc b/changelog.d/9016.misc
deleted file mode 100644
index 0d455b17db..0000000000
--- a/changelog.d/9016.misc
+++ /dev/null
@@ -1 +0,0 @@
-Ensure rejected events get added to some metadata tables.
diff --git a/changelog.d/9017.feature b/changelog.d/9017.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9017.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9018.misc b/changelog.d/9018.misc
deleted file mode 100644
index bb31eb4a46..0000000000
--- a/changelog.d/9018.misc
+++ /dev/null
@@ -1 +0,0 @@
-Ignore date-rotated homeserver logs saved to disk.
diff --git a/changelog.d/9023.bugfix b/changelog.d/9023.bugfix
deleted file mode 100644
index deae64d933..0000000000
--- a/changelog.d/9023.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a longstanding issue where an internal server error would occur when requesting a profile over federation that did not include a display name / avatar URL.
diff --git a/changelog.d/9024.feature b/changelog.d/9024.feature
deleted file mode 100644
index 073dafbf83..0000000000
--- a/changelog.d/9024.feature
+++ /dev/null
@@ -1 +0,0 @@
-Improved performance when calculating ignored users in large rooms.
diff --git a/changelog.d/9025.misc b/changelog.d/9025.misc
deleted file mode 100644
index 658f50d853..0000000000
--- a/changelog.d/9025.misc
+++ /dev/null
@@ -1 +0,0 @@
-Removed an unused column from `access_tokens` table.
diff --git a/changelog.d/9028.bugfix b/changelog.d/9028.bugfix
deleted file mode 100644
index 66666886a4..0000000000
--- a/changelog.d/9028.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a long-standing bug where some caches could grow larger than configured.
diff --git a/changelog.d/9029.misc b/changelog.d/9029.misc
deleted file mode 100644
index 346741d982..0000000000
--- a/changelog.d/9029.misc
+++ /dev/null
@@ -1 +0,0 @@
-Improve efficiency of large state resolutions.
diff --git a/changelog.d/9030.misc b/changelog.d/9030.misc
deleted file mode 100644
index 267cfbf9f9..0000000000
--- a/changelog.d/9030.misc
+++ /dev/null
@@ -1 +0,0 @@
-Add a `-noextras` factor to `tox.ini`, to support running the tests with no optional dependencies.
diff --git a/changelog.d/9031.misc b/changelog.d/9031.misc
deleted file mode 100644
index f43611c385..0000000000
--- a/changelog.d/9031.misc
+++ /dev/null
@@ -1 +0,0 @@
-Fix running unit tests when optional dependencies are not installed.
diff --git a/changelog.d/9033.misc b/changelog.d/9033.misc
deleted file mode 100644
index e9a305c0e8..0000000000
--- a/changelog.d/9033.misc
+++ /dev/null
@@ -1 +0,0 @@
-Allow bumping schema version when using split out state database.
diff --git a/changelog.d/9035.doc b/changelog.d/9035.doc
deleted file mode 100644
index 2a7f0db518..0000000000
--- a/changelog.d/9035.doc
+++ /dev/null
@@ -1 +0,0 @@
-Corrected a typo in the `systemd-with-workers` documentation.
diff --git a/changelog.d/9036.feature b/changelog.d/9036.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9036.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9038.misc b/changelog.d/9038.misc
deleted file mode 100644
index 5b9e21a1db..0000000000
--- a/changelog.d/9038.misc
+++ /dev/null
@@ -1 +0,0 @@
-Configure the linters to run on a consistent set of files.
diff --git a/changelog.d/9039.removal b/changelog.d/9039.removal
deleted file mode 100644
index fb99283ed8..0000000000
--- a/changelog.d/9039.removal
+++ /dev/null
@@ -1 +0,0 @@
-Remove broken and unmaintained `demo/webserver.py` script.
diff --git a/changelog.d/9040.doc b/changelog.d/9040.doc
deleted file mode 100644
index 5c1f7be781..0000000000
--- a/changelog.d/9040.doc
+++ /dev/null
@@ -1 +0,0 @@
-Corrected a typo in `INSTALL.md`.
diff --git a/changelog.d/9041.misc b/changelog.d/9041.misc
deleted file mode 100644
index 4952fbe8a2..0000000000
--- a/changelog.d/9041.misc
+++ /dev/null
@@ -1 +0,0 @@
-Various cleanups to device inbox store.
diff --git a/changelog.d/9042.feature b/changelog.d/9042.feature
deleted file mode 100644
index 4ec319f1f2..0000000000
--- a/changelog.d/9042.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add experimental support for handling and persistence of to-device messages to happen on worker processes.
diff --git a/changelog.d/9043.feature b/changelog.d/9043.feature
deleted file mode 100644
index 4ec319f1f2..0000000000
--- a/changelog.d/9043.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add experimental support for handling and persistence of to-device messages to happen on worker processes.
diff --git a/changelog.d/9044.feature b/changelog.d/9044.feature
deleted file mode 100644
index 4ec319f1f2..0000000000
--- a/changelog.d/9044.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add experimental support for handling and persistence of to-device messages to happen on worker processes.
diff --git a/changelog.d/9051.bugfix b/changelog.d/9051.bugfix
deleted file mode 100644
index 272be9d7a3..0000000000
--- a/changelog.d/9051.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix error handling during insertion of client IPs into the database.
diff --git a/changelog.d/9053.bugfix b/changelog.d/9053.bugfix
deleted file mode 100644
index 3d8bbf11a1..0000000000
--- a/changelog.d/9053.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix bug where we didn't correctly record CPU time spent in 'on_new_event' block.
diff --git a/changelog.d/9054.bugfix b/changelog.d/9054.bugfix
deleted file mode 100644
index 0bfe951f17..0000000000
--- a/changelog.d/9054.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a minor bug which could cause confusing error messages from invalid configurations.
diff --git a/changelog.d/9055.misc b/changelog.d/9055.misc
deleted file mode 100644
index 8e0512eb1e..0000000000
--- a/changelog.d/9055.misc
+++ /dev/null
@@ -1 +0,0 @@
-Drop unused database tables.
diff --git a/changelog.d/9057.doc b/changelog.d/9057.doc
deleted file mode 100644
index d16686e7dc..0000000000
--- a/changelog.d/9057.doc
+++ /dev/null
@@ -1 +0,0 @@
-Add missing user_mapping_provider configuration to the Keycloak OIDC example. Contributed by @chris-ruecker.
diff --git a/changelog.d/9058.misc b/changelog.d/9058.misc
deleted file mode 100644
index 9df6796e22..0000000000
--- a/changelog.d/9058.misc
+++ /dev/null
@@ -1 +0,0 @@
-Remove unused `SynapseService` class.
diff --git a/changelog.d/9059.bugfix b/changelog.d/9059.bugfix
deleted file mode 100644
index 2933703ffa..0000000000
--- a/changelog.d/9059.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix incorrect exit code when there is an error at startup.
diff --git a/changelog.d/9063.misc b/changelog.d/9063.misc
deleted file mode 100644
index 22eed43147..0000000000
--- a/changelog.d/9063.misc
+++ /dev/null
@@ -1 +0,0 @@
-Removes unnecessary declarations in the tests for the admin API.
\ No newline at end of file
diff --git a/changelog.d/9067.feature b/changelog.d/9067.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9067.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9068.feature b/changelog.d/9068.feature
deleted file mode 100644
index cdf1844fa7..0000000000
--- a/changelog.d/9068.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add experimental support for handling `/keys/claim` and `/room_keys` APIs on worker processes.
diff --git a/changelog.d/9069.misc b/changelog.d/9069.misc
deleted file mode 100644
index 5e9e62d252..0000000000
--- a/changelog.d/9069.misc
+++ /dev/null
@@ -1 +0,0 @@
-Remove `SynapseRequest.get_user_agent`.
diff --git a/changelog.d/9070.bugfix b/changelog.d/9070.bugfix
deleted file mode 100644
index 72b8fe9f1c..0000000000
--- a/changelog.d/9070.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix `JSONDecodeError` spamming the logs when sending transactions to remote servers.
diff --git a/changelog.d/9071.bugfix b/changelog.d/9071.bugfix
deleted file mode 100644
index 0201271f84..0000000000
--- a/changelog.d/9071.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix "Failed to send request" errors when a client provides an invalid room alias.
diff --git a/changelog.d/9080.misc b/changelog.d/9080.misc
deleted file mode 100644
index 3da8171f5f..0000000000
--- a/changelog.d/9080.misc
+++ /dev/null
@@ -1 +0,0 @@
-Remove redundant `Homeserver.get_ip_from_request` method.
diff --git a/changelog.d/9081.feature b/changelog.d/9081.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9081.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9082.feature b/changelog.d/9082.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9082.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9086.feature b/changelog.d/9086.feature
deleted file mode 100644
index 3e678e24d5..0000000000
--- a/changelog.d/9086.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add an admin API for protecting local media from quarantine.
diff --git a/changelog.d/9091.feature b/changelog.d/9091.feature
deleted file mode 100644
index 79fcd701f8..0000000000
--- a/changelog.d/9091.feature
+++ /dev/null
@@ -1 +0,0 @@
-During user-interactive authentication via single-sign-on, give a better error if the user uses the wrong account on the SSO IdP.
diff --git a/changelog.d/9092.feature b/changelog.d/9092.feature
deleted file mode 100644
index 64843a6a95..0000000000
--- a/changelog.d/9092.feature
+++ /dev/null
@@ -1 +0,0 @@
- Add experimental support for handling `/devices` API on worker processes.
diff --git a/changelog.d/9093.misc b/changelog.d/9093.misc
deleted file mode 100644
index 53eb8f72a8..0000000000
--- a/changelog.d/9093.misc
+++ /dev/null
@@ -1 +0,0 @@
-Add type hints to media repository.
diff --git a/changelog.d/9098.misc b/changelog.d/9098.misc
deleted file mode 100644
index 907020d428..0000000000
--- a/changelog.d/9098.misc
+++ /dev/null
@@ -1 +0,0 @@
-Fix the wrong arguments being passed to `BlacklistingAgentWrapper` from `MatrixFederationAgent`. Contributed by Timothy Leung.
diff --git a/changelog.d/9104.feature b/changelog.d/9104.feature
deleted file mode 100644
index 1c4f88bce9..0000000000
--- a/changelog.d/9104.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add experimental support for moving off receipts and account data persistence off master.
diff --git a/changelog.d/9105.feature b/changelog.d/9105.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9105.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9106.misc b/changelog.d/9106.misc
deleted file mode 100644
index 4cd2605754..0000000000
--- a/changelog.d/9106.misc
+++ /dev/null
@@ -1 +0,0 @@
-Reduce the scope of caught exceptions in `BlacklistingAgentWrapper`.
diff --git a/changelog.d/9107.feature b/changelog.d/9107.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9107.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9108.bugfix b/changelog.d/9108.bugfix
deleted file mode 100644
index 465ef63508..0000000000
--- a/changelog.d/9108.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix "Unhandled error in Deferred: BodyExceededMaxSize" errors when .well-known files that are too large.
diff --git a/changelog.d/9109.feature b/changelog.d/9109.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9109.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9110.feature b/changelog.d/9110.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9110.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9112.misc b/changelog.d/9112.misc
deleted file mode 100644
index 691f9d8b43..0000000000
--- a/changelog.d/9112.misc
+++ /dev/null
@@ -1 +0,0 @@
-Improve `UsernamePickerTestCase`.
diff --git a/changelog.d/9114.bugfix b/changelog.d/9114.bugfix
deleted file mode 100644
index 211f26589d..0000000000
--- a/changelog.d/9114.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix bugs in federation catchup logic that caused outbound federation to be delayed for large servers after start up. Introduced in v1.8.0 and v1.21.0.
diff --git a/changelog.d/9115.misc b/changelog.d/9115.misc
deleted file mode 100644
index 346741d982..0000000000
--- a/changelog.d/9115.misc
+++ /dev/null
@@ -1 +0,0 @@
-Improve efficiency of large state resolutions.
diff --git a/changelog.d/9116.bugfix b/changelog.d/9116.bugfix
deleted file mode 100644
index 211f26589d..0000000000
--- a/changelog.d/9116.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix bugs in federation catchup logic that caused outbound federation to be delayed for large servers after start up. Introduced in v1.8.0 and v1.21.0.
diff --git a/changelog.d/9117.bugfix b/changelog.d/9117.bugfix
deleted file mode 100644
index 233a76d18b..0000000000
--- a/changelog.d/9117.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix corruption of `pushers` data when a postgres bouncer is used.
diff --git a/changelog.d/9118.misc b/changelog.d/9118.misc
deleted file mode 100644
index 346741d982..0000000000
--- a/changelog.d/9118.misc
+++ /dev/null
@@ -1 +0,0 @@
-Improve efficiency of large state resolutions.
diff --git a/changelog.d/9124.misc b/changelog.d/9124.misc
deleted file mode 100644
index 346741d982..0000000000
--- a/changelog.d/9124.misc
+++ /dev/null
@@ -1 +0,0 @@
-Improve efficiency of large state resolutions.
diff --git a/changelog.d/9125.misc b/changelog.d/9125.misc
deleted file mode 100644
index 08459caf5a..0000000000
--- a/changelog.d/9125.misc
+++ /dev/null
@@ -1 +0,0 @@
-Remove dependency on `distutils`.
diff --git a/changelog.d/9127.feature b/changelog.d/9127.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9127.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9128.bugfix b/changelog.d/9128.bugfix
deleted file mode 100644
index f87b9fb9aa..0000000000
--- a/changelog.d/9128.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix minor bugs in handling the `clientRedirectUrl` parameter for SSO login.
diff --git a/changelog.d/9130.feature b/changelog.d/9130.feature
deleted file mode 100644
index 4ec319f1f2..0000000000
--- a/changelog.d/9130.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add experimental support for handling and persistence of to-device messages to happen on worker processes.
diff --git a/changelog.d/9144.misc b/changelog.d/9144.misc
deleted file mode 100644
index 38a506b170..0000000000
--- a/changelog.d/9144.misc
+++ /dev/null
@@ -1 +0,0 @@
-Enforce that replication HTTP clients are called with keyword arguments only.
diff --git a/changelog.d/9145.bugfix b/changelog.d/9145.bugfix
deleted file mode 100644
index 947cf1dc25..0000000000
--- a/changelog.d/9145.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix "UnboundLocalError: local variable 'length' referenced before assignment" errors when the response body exceeds the expected size. This bug was introduced in v1.25.0.
diff --git a/changelog.d/9146.misc b/changelog.d/9146.misc
deleted file mode 100644
index 7af29baa30..0000000000
--- a/changelog.d/9146.misc
+++ /dev/null
@@ -1 +0,0 @@
-Fix the Python 3.5 + old dependencies build in CI.
diff --git a/changelog.d/9151.doc b/changelog.d/9151.doc
deleted file mode 100644
index 7535748060..0000000000
--- a/changelog.d/9151.doc
+++ /dev/null
@@ -1 +0,0 @@
-Quote `pip install` packages when extras are used to avoid shells interpreting bracket characters.
diff --git a/changelog.d/9153.feature b/changelog.d/9153.feature
deleted file mode 100644
index 01a24dcf49..0000000000
--- a/changelog.d/9153.feature
+++ /dev/null
@@ -1 +0,0 @@
-Add support for multiple SSO Identity Providers.
diff --git a/changelog.d/9157.misc b/changelog.d/9157.misc
deleted file mode 100644
index 76b2a66a05..0000000000
--- a/changelog.d/9157.misc
+++ /dev/null
@@ -1 +0,0 @@
-Replace the old `perspectives` option in the Synapse docker config file template with `trusted_key_servers`.
\ No newline at end of file
diff --git a/changelog.d/9161.bugfix b/changelog.d/9161.bugfix
deleted file mode 100644
index 6798126b7c..0000000000
--- a/changelog.d/9161.bugfix
+++ /dev/null
@@ -1 +0,0 @@
-Fix a long-standing bug "ValueError: invalid literal for int() with base 10" when `/publicRooms` is requested with an invalid `server` parameter.
diff --git a/debian/build_virtualenv b/debian/build_virtualenv
index cbdde93f96..cf19084a9f 100755
--- a/debian/build_virtualenv
+++ b/debian/build_virtualenv
@@ -33,11 +33,13 @@ esac
 # Use --builtin-venv to use the better `venv` module from CPython 3.4+ rather
 # than the 2/3 compatible `virtualenv`.
 
+# Pin pip to 20.3.4 to fix breakage in 21.0 on py3.5 (xenial)
+
 dh_virtualenv \
     --install-suffix "matrix-synapse" \
     --builtin-venv \
     --python "$SNAKE" \
-    --upgrade-pip \
+    --upgrade-pip-to="20.3.4" \
     --preinstall="lxml" \
     --preinstall="mock" \
     --extra-pip-arg="--no-cache-dir" \
diff --git a/debian/changelog b/debian/changelog
index 1c6308e3a2..1a421a85bd 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,8 +1,18 @@
-matrix-synapse-py3 (1.25.0ubuntu1) UNRELEASED; urgency=medium
+matrix-synapse-py3 (1.26.0+nmu1) UNRELEASED; urgency=medium
 
+  * Fix build on Ubuntu 16.04 LTS (Xenial).
+
+ -- Dan Callahan <danc@element.io>  Thu, 28 Jan 2021 16:21:03 +0000
+
+matrix-synapse-py3 (1.26.0) stable; urgency=medium
+
+  [ Richard van der Hoff ]
   * Remove dependency on `python3-distutils`.
 
- -- Richard van der Hoff <richard@matrix.org>  Fri, 15 Jan 2021 12:44:19 +0000
+  [ Synapse Packaging team ]
+  * New synapse release 1.26.0.
+
+ -- Synapse Packaging team <packages@matrix.org>  Wed, 27 Jan 2021 12:43:35 -0500
 
 matrix-synapse-py3 (1.25.0) stable; urgency=medium
 
diff --git a/docker/Dockerfile-dhvirtualenv b/docker/Dockerfile-dhvirtualenv
index e529293803..0d74630370 100644
--- a/docker/Dockerfile-dhvirtualenv
+++ b/docker/Dockerfile-dhvirtualenv
@@ -27,6 +27,7 @@ RUN env DEBIAN_FRONTEND=noninteractive apt-get install \
         wget
 
 # fetch and unpack the package
+# TODO: Upgrade to 1.2.2 once xenial is dropped
 RUN mkdir /dh-virtualenv
 RUN wget -q -O /dh-virtualenv.tar.gz https://github.com/spotify/dh-virtualenv/archive/ac6e1b1.tar.gz
 RUN tar -xv --strip-components=1 -C /dh-virtualenv -f /dh-virtualenv.tar.gz
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 9e560003a9..3832b36407 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -9,6 +9,7 @@
   * [Response](#response)
   * [Undoing room shutdowns](#undoing-room-shutdowns)
 - [Make Room Admin API](#make-room-admin-api)
+- [Forward Extremities Admin API](#forward-extremities-admin-api)
 
 # List Room API
 
@@ -367,6 +368,36 @@ Response:
 }
 ```
 
+# Room State API
+
+The Room State admin API allows server admins to get a list of all state events in a room.
+
+The response includes the following fields:
+
+* `state` - The current state of the room at the time of request.
+
+## Usage
+
+A standard request:
+
+```
+GET /_synapse/admin/v1/rooms/<room_id>/state
+
+{}
+```
+
+Response:
+
+```json
+{
+  "state": [
+    {"type": "m.room.create", "state_key": "", "etc": true},
+    {"type": "m.room.power_levels", "state_key": "", "etc": true},
+    {"type": "m.room.name", "state_key": "", "etc": true}
+  ]
+}
+```
+
 # Delete Room API
 
 The Delete Room admin API allows server admins to remove rooms from server
@@ -511,3 +542,55 @@ optionally be specified, e.g.:
         "user_id": "@foo:example.com"
     }
 ```
+
+# Forward Extremities Admin API
+
+Enables querying and deleting forward extremities from rooms. When a lot of forward
+extremities accumulate in a room, performance can become degraded. For details, see 
+[#1760](https://github.com/matrix-org/synapse/issues/1760).
+
+## Check for forward extremities
+
+To check the status of forward extremities for a room:
+
+```
+    GET /_synapse/admin/v1/rooms/<room_id_or_alias>/forward_extremities
+```
+
+A response as follows will be returned:
+
+```json
+{
+  "count": 1,
+  "results": [
+    {
+      "event_id": "$M5SP266vsnxctfwFgFLNceaCo3ujhRtg_NiiHabcdefgh",
+      "state_group": 439,
+      "depth": 123,
+      "received_ts": 1611263016761
+    }
+  ]
+}    
+```
+
+## Deleting forward extremities
+
+**WARNING**: Please ensure you know what you're doing and have read 
+the related issue [#1760](https://github.com/matrix-org/synapse/issues/1760).
+Under no situations should this API be executed as an automated maintenance task!
+
+If a room has lots of forward extremities, the extra can be
+deleted as follows:
+
+```
+    DELETE /_synapse/admin/v1/rooms/<room_id_or_alias>/forward_extremities
+```
+
+A response as follows will be returned, indicating the amount of forward extremities
+that were deleted.
+
+```json
+{
+  "deleted": 1
+}
+```
diff --git a/docs/admin_api/user_admin_api.rst b/docs/admin_api/user_admin_api.rst
index b3d413cf57..1eb674939e 100644
--- a/docs/admin_api/user_admin_api.rst
+++ b/docs/admin_api/user_admin_api.rst
@@ -760,3 +760,33 @@ The following fields are returned in the JSON response body:
 - ``total`` - integer - Number of pushers.
 
 See also `Client-Server API Spec <https://matrix.org/docs/spec/client_server/latest#get-matrix-client-r0-pushers>`_
+
+Shadow-banning users
+====================
+
+Shadow-banning is a useful tool for moderating malicious or egregiously abusive users.
+A shadow-banned users receives successful responses to their client-server API requests,
+but the events are not propagated into rooms. This can be an effective tool as it
+(hopefully) takes longer for the user to realise they are being moderated before
+pivoting to another account.
+
+Shadow-banning a user should be used as a tool of last resort and may lead to confusing
+or broken behaviour for the client. A shadow-banned user will not receive any
+notification and it is generally more appropriate to ban or kick abusive users.
+A shadow-banned user will be unable to contact anyone on the server.
+
+The API is::
+
+  POST /_synapse/admin/v1/users/<user_id>/shadow_ban
+
+To use it, you will need to authenticate by providing an ``access_token`` for a
+server admin: see `README.rst <README.rst>`_.
+
+An empty JSON dict is returned.
+
+**Parameters**
+
+The following parameters should be set in the URL:
+
+- ``user_id`` - The fully qualified MXID: for example, ``@user:server.com``. The user must
+  be local.
diff --git a/docs/openid.md b/docs/openid.md
index b86ae89768..9d19368845 100644
--- a/docs/openid.md
+++ b/docs/openid.md
@@ -44,7 +44,7 @@ as follows:
 
 To enable the OpenID integration, you should then add a section to the `oidc_providers`
 setting in your configuration file (or uncomment one of the existing examples).
-See [sample_config.yaml](./sample_config.yaml) for some sample settings, as well as 
+See [sample_config.yaml](./sample_config.yaml) for some sample settings, as well as
 the text below for example configurations for specific providers.
 
 ## Sample configs
@@ -52,11 +52,12 @@ the text below for example configurations for specific providers.
 Here are a few configs for providers that should work with Synapse.
 
 ### Microsoft Azure Active Directory
-Azure AD can act as an OpenID Connect Provider. Register a new application under 
+Azure AD can act as an OpenID Connect Provider. Register a new application under
 *App registrations* in the Azure AD management console. The RedirectURI for your
-application should point to your matrix server: `[synapse public baseurl]/_synapse/oidc/callback`
+application should point to your matrix server:
+`[synapse public baseurl]/_synapse/client/oidc/callback`
 
-Go to *Certificates & secrets* and register a new client secret. Make note of your 
+Go to *Certificates & secrets* and register a new client secret. Make note of your
 Directory (tenant) ID as it will be used in the Azure links.
 Edit your Synapse config file and change the `oidc_config` section:
 
@@ -94,7 +95,7 @@ staticClients:
 - id: synapse
   secret: secret
   redirectURIs:
-  - '[synapse public baseurl]/_synapse/oidc/callback'
+  - '[synapse public baseurl]/_synapse/client/oidc/callback'
   name: 'Synapse'
 ```
 
@@ -118,7 +119,7 @@ oidc_providers:
 ```
 ### [Keycloak][keycloak-idp]
 
-[Keycloak][keycloak-idp] is an opensource IdP maintained by Red Hat. 
+[Keycloak][keycloak-idp] is an opensource IdP maintained by Red Hat.
 
 Follow the [Getting Started Guide](https://www.keycloak.org/getting-started) to install Keycloak and set up a realm.
 
@@ -140,7 +141,7 @@ Follow the [Getting Started Guide](https://www.keycloak.org/getting-started) to
 | Enabled | `On` |
 | Client Protocol | `openid-connect` |
 | Access Type | `confidential` |
-| Valid Redirect URIs | `[synapse public baseurl]/_synapse/oidc/callback` |
+| Valid Redirect URIs | `[synapse public baseurl]/_synapse/client/oidc/callback` |
 
 5. Click `Save`
 6. On the Credentials tab, update the fields:
@@ -168,7 +169,7 @@ oidc_providers:
 ### [Auth0][auth0]
 
 1. Create a regular web application for Synapse
-2. Set the Allowed Callback URLs to `[synapse public baseurl]/_synapse/oidc/callback`
+2. Set the Allowed Callback URLs to `[synapse public baseurl]/_synapse/client/oidc/callback`
 3. Add a rule to add the `preferred_username` claim.
    <details>
     <summary>Code sample</summary>
@@ -194,7 +195,7 @@ Synapse config:
 
 ```yaml
 oidc_providers:
-  - idp_id: auth0 
+  - idp_id: auth0
     idp_name: Auth0
     issuer: "https://your-tier.eu.auth0.com/" # TO BE FILLED
     client_id: "your-client-id" # TO BE FILLED
@@ -217,7 +218,7 @@ login mechanism needs an attribute to uniquely identify users, and that endpoint
 does not return a `sub` property, an alternative `subject_claim` has to be set.
 
 1. Create a new OAuth application: https://github.com/settings/applications/new.
-2. Set the callback URL to `[synapse public baseurl]/_synapse/oidc/callback`.
+2. Set the callback URL to `[synapse public baseurl]/_synapse/client/oidc/callback`.
 
 Synapse config:
 
@@ -225,6 +226,7 @@ Synapse config:
 oidc_providers:
   - idp_id: github
     idp_name: Github
+    idp_brand: "org.matrix.github"  # optional: styling hint for clients
     discover: false
     issuer: "https://github.com/"
     client_id: "your-client-id" # TO BE FILLED
@@ -250,6 +252,7 @@ oidc_providers:
    oidc_providers:
      - idp_id: google
        idp_name: Google
+       idp_brand: "org.matrix.google"  # optional: styling hint for clients
        issuer: "https://accounts.google.com/"
        client_id: "your-client-id" # TO BE FILLED
        client_secret: "your-client-secret" # TO BE FILLED
@@ -260,13 +263,13 @@ oidc_providers:
            display_name_template: "{{ user.name }}"
    ```
 4. Back in the Google console, add this Authorized redirect URI: `[synapse
-   public baseurl]/_synapse/oidc/callback`.
+   public baseurl]/_synapse/client/oidc/callback`.
 
 ### Twitch
 
 1. Setup a developer account on [Twitch](https://dev.twitch.tv/)
 2. Obtain the OAuth 2.0 credentials by [creating an app](https://dev.twitch.tv/console/apps/)
-3. Add this OAuth Redirect URL: `[synapse public baseurl]/_synapse/oidc/callback`
+3. Add this OAuth Redirect URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
 
 Synapse config:
 
@@ -288,7 +291,7 @@ oidc_providers:
 
 1. Create a [new application](https://gitlab.com/profile/applications).
 2. Add the `read_user` and `openid` scopes.
-3. Add this Callback URL: `[synapse public baseurl]/_synapse/oidc/callback`
+3. Add this Callback URL: `[synapse public baseurl]/_synapse/client/oidc/callback`
 
 Synapse config:
 
@@ -296,6 +299,7 @@ Synapse config:
 oidc_providers:
   - idp_id: gitlab
     idp_name: Gitlab
+    idp_brand: "org.matrix.gitlab"  # optional: styling hint for clients
     issuer: "https://gitlab.com/"
     client_id: "your-client-id" # TO BE FILLED
     client_secret: "your-client-secret" # TO BE FILLED
@@ -307,3 +311,80 @@ oidc_providers:
         localpart_template: '{{ user.nickname }}'
         display_name_template: '{{ user.name }}'
 ```
+
+### Facebook
+
+Like Github, Facebook provide a custom OAuth2 API rather than an OIDC-compliant
+one so requires a little more configuration.
+
+0. You will need a Facebook developer account. You can register for one
+   [here](https://developers.facebook.com/async/registration/).
+1. On the [apps](https://developers.facebook.com/apps/) page of the developer
+   console, "Create App", and choose "Build Connected Experiences".
+2. Once the app is created, add "Facebook Login" and choose "Web". You don't
+   need to go through the whole form here.
+3. In the left-hand menu, open "Products"/"Facebook Login"/"Settings".
+   * Add `[synapse public baseurl]/_synapse/client/oidc/callback` as an OAuth Redirect
+     URL.
+4. In the left-hand menu, open "Settings/Basic". Here you can copy the "App ID"
+   and "App Secret" for use below.
+
+Synapse config:
+
+```yaml
+  - idp_id: facebook
+    idp_name: Facebook
+    idp_brand: "org.matrix.facebook"  # optional: styling hint for clients
+    discover: false
+    issuer: "https://facebook.com"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    scopes: ["openid", "email"]
+    authorization_endpoint: https://facebook.com/dialog/oauth
+    token_endpoint: https://graph.facebook.com/v9.0/oauth/access_token
+    user_profile_method: "userinfo_endpoint"
+    userinfo_endpoint: "https://graph.facebook.com/v9.0/me?fields=id,name,email,picture"
+    user_mapping_provider:
+      config:
+        subject_claim: "id"
+        display_name_template: "{{ user.name }}"
+```
+
+Relevant documents:
+ * https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow
+ * Using Facebook's Graph API: https://developers.facebook.com/docs/graph-api/using-graph-api/
+ * Reference to the User endpoint: https://developers.facebook.com/docs/graph-api/reference/user
+
+### Gitea
+
+Gitea is, like Github, not an OpenID provider, but just an OAuth2 provider.
+
+The [`/user` API endpoint](https://try.gitea.io/api/swagger#/user/userGetCurrent)
+can be used to retrieve information on the authenticated user. As the Synapse
+login mechanism needs an attribute to uniquely identify users, and that endpoint
+does not return a `sub` property, an alternative `subject_claim` has to be set.
+
+1. Create a new application.
+2. Add this Callback URL: `[synapse public baseurl]/_synapse/oidc/callback`
+
+Synapse config:
+
+```yaml
+oidc_providers:
+  - idp_id: gitea
+    idp_name: Gitea
+    discover: false
+    issuer: "https://your-gitea.com/"
+    client_id: "your-client-id" # TO BE FILLED
+    client_secret: "your-client-secret" # TO BE FILLED
+    client_auth_method: client_secret_post
+    scopes: [] # Gitea doesn't support Scopes
+    authorization_endpoint: "https://your-gitea.com/login/oauth/authorize"
+    token_endpoint: "https://your-gitea.com/login/oauth/access_token"
+    userinfo_endpoint: "https://your-gitea.com/api/v1/user"
+    user_mapping_provider:
+      config:
+        subject_claim: "id"
+        localpart_template: "{{ user.login }}"
+        display_name_template: "{{ user.full_name }}" 
+```
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index ae995efe9b..6d265d2972 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -67,11 +67,16 @@ pid_file: DATADIR/homeserver.pid
 #
 #web_client_location: https://riot.example.com/
 
-# The public-facing base URL that clients use to access this HS
-# (not including _matrix/...). This is the same URL a user would
-# enter into the 'custom HS URL' field on their client. If you
-# use synapse with a reverse proxy, this should be the URL to reach
-# synapse via the proxy.
+# The public-facing base URL that clients use to access this Homeserver (not
+# including _matrix/...). This is the same URL a user might enter into the
+# 'Custom Homeserver URL' field on their client. If you use Synapse with a
+# reverse proxy, this should be the URL to reach Synapse via the proxy.
+# Otherwise, it should be the URL to reach Synapse's client HTTP listener (see
+# 'listeners' below).
+#
+# If this is left unset, it defaults to 'https://<server_name>/'. (Note that
+# that will not work unless you configure Synapse or a reverse-proxy to listen
+# on port 443.)
 #
 #public_baseurl: https://example.com/
 
@@ -819,6 +824,9 @@ log_config: "CONFDIR/SERVERNAME.log.config"
 #     users are joining rooms the server is already in (this is cheap) vs
 #     "remote" for when users are trying to join rooms not on the server (which
 #     can be more expensive)
+#   - one for ratelimiting how often a user or IP can attempt to validate a 3PID.
+#   - two for ratelimiting how often invites can be sent in a room or to a
+#     specific user.
 #
 # The defaults are as shown below.
 #
@@ -852,7 +860,18 @@ log_config: "CONFDIR/SERVERNAME.log.config"
 #  remote:
 #    per_second: 0.01
 #    burst_count: 3
-
+#
+#rc_3pid_validation:
+#  per_second: 0.003
+#  burst_count: 5
+#
+#rc_invites:
+#  per_room:
+#    per_second: 0.3
+#    burst_count: 10
+#  per_user:
+#    per_second: 0.003
+#    burst_count: 5
 
 # Ratelimiting settings for incoming federation
 #
@@ -1150,8 +1169,9 @@ account_validity:
   # send an email to the account's email address with a renewal link. By
   # default, no such emails are sent.
   #
-  # If you enable this setting, you will also need to fill out the 'email' and
-  # 'public_baseurl' configuration sections.
+  # If you enable this setting, you will also need to fill out the 'email'
+  # configuration section. You should also check that 'public_baseurl' is set
+  # correctly.
   #
   #renew_at: 1w
 
@@ -1242,8 +1262,7 @@ account_validity:
 # The identity server which we suggest that clients should use when users log
 # in on this server.
 #
-# (By default, no suggestion is made, so it is left up to the client.
-# This setting is ignored unless public_baseurl is also set.)
+# (By default, no suggestion is made, so it is left up to the client.)
 #
 #default_identity_server: https://matrix.org
 
@@ -1268,8 +1287,6 @@ account_validity:
 # by the Matrix Identity Service API specification:
 # https://matrix.org/docs/spec/identity_service/latest
 #
-# If a delegate is specified, the config option public_baseurl must also be filled out.
-#
 account_threepid_delegates:
     #email: https://example.com     # Delegate email sending to example.com
     #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
@@ -1549,10 +1566,10 @@ trusted_key_servers:
 # enable SAML login.
 #
 # Once SAML support is enabled, a metadata file will be exposed at
-# https://<server>:<port>/_matrix/saml2/metadata.xml, which you may be able to
+# https://<server>:<port>/_synapse/client/saml2/metadata.xml, which you may be able to
 # use to configure your SAML IdP with. Alternatively, you can manually configure
 # the IdP to use an ACS location of
-# https://<server>:<port>/_matrix/saml2/authn_response.
+# https://<server>:<port>/_synapse/client/saml2/authn_response.
 #
 saml2_config:
   # `sp_config` is the configuration for the pysaml2 Service Provider.
@@ -1723,6 +1740,16 @@ saml2_config:
 #   idp_name: A user-facing name for this identity provider, which is used to
 #       offer the user a choice of login mechanisms.
 #
+#   idp_icon: An optional icon for this identity provider, which is presented
+#       by clients and Synapse's own IdP picker page. If given, must be an
+#       MXC URI of the format mxc://<server-name>/<media-id>. (An easy way to
+#       obtain such an MXC URI is to upload an image to an (unencrypted) room
+#       and then copy the "url" from the source of the event.)
+#
+#   idp_brand: An optional brand for this identity provider, allowing clients
+#       to style the login flow according to the identity provider in question.
+#       See the spec for possible options here.
+#
 #   discover: set to 'false' to disable the use of the OIDC discovery mechanism
 #       to discover endpoints. Defaults to true.
 #
@@ -1782,17 +1809,21 @@ saml2_config:
 #
 #           For the default provider, the following settings are available:
 #
-#             sub: name of the claim containing a unique identifier for the
-#                 user. Defaults to 'sub', which OpenID Connect compliant
-#                 providers should provide.
+#             subject_claim: name of the claim containing a unique identifier
+#                 for the user. Defaults to 'sub', which OpenID Connect
+#                 compliant providers should provide.
 #
 #             localpart_template: Jinja2 template for the localpart of the MXID.
 #                 If this is not set, the user will be prompted to choose their
-#                 own username.
+#                 own username (see 'sso_auth_account_details.html' in the 'sso'
+#                 section of this file).
 #
 #             display_name_template: Jinja2 template for the display name to set
 #                 on first login. If unset, no displayname will be set.
 #
+#             email_template: Jinja2 template for the email address of the user.
+#                 If unset, no email address will be added to the account.
+#
 #             extra_attributes: a map of Jinja2 templates for extra attributes
 #                 to send back to the client during login.
 #                 Note that these are non-standard and clients will ignore them
@@ -1807,13 +1838,16 @@ saml2_config:
 #
 # For backwards compatibility, it is also possible to configure a single OIDC
 # provider via an 'oidc_config' setting. This is now deprecated and admins are
-# advised to migrate to the 'oidc_providers' format.
+# advised to migrate to the 'oidc_providers' format. (When doing that migration,
+# use 'oidc' for the idp_id to ensure that existing users continue to be
+# recognised.)
 #
 oidc_providers:
   # Generic example
   #
   #- idp_id: my_idp
   #  idp_name: "My OpenID provider"
+  #  idp_icon: "mxc://example.com/mediaid"
   #  discover: false
   #  issuer: "https://accounts.example.com/"
   #  client_id: "provided-by-your-issuer"
@@ -1825,6 +1859,12 @@ oidc_providers:
   #  userinfo_endpoint: "https://accounts.example.com/userinfo"
   #  jwks_uri: "https://accounts.example.com/.well-known/jwks.json"
   #  skip_verification: true
+  #  user_mapping_provider:
+  #    config:
+  #      subject_claim: "id"
+  #      localpart_template: "{ user.login }"
+  #      display_name_template: "{ user.name }"
+  #      email_template: "{ user.email }"
 
   # For use with Keycloak
   #
@@ -1837,8 +1877,9 @@ oidc_providers:
 
   # For use with Github
   #
-  #- idp_id: google
-  #  idp_name: Google
+  #- idp_id: github
+  #  idp_name: Github
+  #  idp_brand: org.matrix.github
   #  discover: false
   #  issuer: "https://github.com/"
   #  client_id: "your-client-id" # TO BE FILLED
@@ -1866,10 +1907,6 @@ cas_config:
   #
   #server_url: "https://cas-server.com"
 
-  # The public URL of the homeserver.
-  #
-  #service_url: "https://homeserver.domain.com:8448"
-
   # The attribute of the CAS response to use as the display name.
   #
   # If unset, no displayname will be set.
@@ -1901,9 +1938,9 @@ sso:
     # phishing attacks from evil.site. To avoid this, include a slash after the
     # hostname: "https://my.client/".
     #
-    # If public_baseurl is set, then the login fallback page (used by clients
-    # that don't natively support the required login flows) is whitelisted in
-    # addition to any URLs in this list.
+    # The login fallback page (used by clients that don't natively support the
+    # required login flows) is automatically whitelisted in addition to any URLs
+    # in this list.
     #
     # By default, this list is empty.
     #
@@ -1931,8 +1968,13 @@ sso:
     #
     #     * providers: a list of available Identity Providers. Each element is
     #       an object with the following attributes:
+    #
     #         * idp_id: unique identifier for the IdP
     #         * idp_name: user-facing name for the IdP
+    #         * idp_icon: if specified in the IdP config, an MXC URI for an icon
+    #              for the IdP
+    #         * idp_brand: if specified in the IdP config, a textual identifier
+    #              for the brand of the IdP
     #
     #   The rendered HTML page should contain a form which submits its results
     #   back as a GET request, with the following query parameters:
@@ -1942,10 +1984,62 @@ sso:
     #
     #     * idp: the 'idp_id' of the chosen IDP.
     #
+    # * HTML page to prompt new users to enter a userid and confirm other
+    #   details: 'sso_auth_account_details.html'. This is only shown if the
+    #   SSO implementation (with any user_mapping_provider) does not return
+    #   a localpart.
+    #
+    #   When rendering, this template is given the following variables:
+    #
+    #     * server_name: the homeserver's name.
+    #
+    #     * idp: details of the SSO Identity Provider that the user logged in
+    #       with: an object with the following attributes:
+    #
+    #         * idp_id: unique identifier for the IdP
+    #         * idp_name: user-facing name for the IdP
+    #         * idp_icon: if specified in the IdP config, an MXC URI for an icon
+    #              for the IdP
+    #         * idp_brand: if specified in the IdP config, a textual identifier
+    #              for the brand of the IdP
+    #
+    #     * user_attributes: an object containing details about the user that
+    #       we received from the IdP. May have the following attributes:
+    #
+    #         * display_name: the user's display_name
+    #         * emails: a list of email addresses
+    #
+    #   The template should render a form which submits the following fields:
+    #
+    #     * username: the localpart of the user's chosen user id
+    #
+    # * HTML page allowing the user to consent to the server's terms and
+    #   conditions. This is only shown for new users, and only if
+    #   `user_consent.require_at_registration` is set.
+    #
+    #   When rendering, this template is given the following variables:
+    #
+    #     * server_name: the homeserver's name.
+    #
+    #     * user_id: the user's matrix proposed ID.
+    #
+    #     * user_profile.display_name: the user's proposed display name, if any.
+    #
+    #     * consent_version: the version of the terms that the user will be
+    #       shown
+    #
+    #     * terms_url: a link to the page showing the terms.
+    #
+    #   The template should render a form which submits the following fields:
+    #
+    #     * accepted_version: the version of the terms accepted by the user
+    #       (ie, 'consent_version' from the input variables).
+    #
     # * HTML page for a confirmation step before redirecting back to the client
     #   with the login token: 'sso_redirect_confirm.html'.
     #
-    #   When rendering, this template is given three variables:
+    #   When rendering, this template is given the following variables:
+    #
     #     * redirect_url: the URL the user is about to be redirected to. Needs
     #                     manual escaping (see
     #                     https://jinja.palletsprojects.com/en/2.11.x/templates/#html-escaping).
@@ -1958,6 +2052,17 @@ sso:
     #
     #     * server_name: the homeserver's name.
     #
+    #     * new_user: a boolean indicating whether this is the user's first time
+    #          logging in.
+    #
+    #     * user_id: the user's matrix ID.
+    #
+    #     * user_profile.avatar_url: an MXC URI for the user's avatar, if any.
+    #           None if the user has not set an avatar.
+    #
+    #     * user_profile.display_name: the user's display name. None if the user
+    #           has not set a display name.
+    #
     # * HTML page which notifies the user that they are authenticating to confirm
     #   an operation on their account during the user interactive authentication
     #   process: 'sso_auth_confirm.html'.
@@ -1969,6 +2074,16 @@ sso:
     #
     #     * description: the operation which the user is being asked to confirm
     #
+    #     * idp: details of the Identity Provider that we will use to confirm
+    #       the user's identity: an object with the following attributes:
+    #
+    #         * idp_id: unique identifier for the IdP
+    #         * idp_name: user-facing name for the IdP
+    #         * idp_icon: if specified in the IdP config, an MXC URI for an icon
+    #              for the IdP
+    #         * idp_brand: if specified in the IdP config, a textual identifier
+    #              for the brand of the IdP
+    #
     # * HTML page shown after a successful user interactive authentication session:
     #   'sso_auth_success.html'.
     #
diff --git a/docs/turn-howto.md b/docs/turn-howto.md
index a470c274a5..e8f13ad484 100644
--- a/docs/turn-howto.md
+++ b/docs/turn-howto.md
@@ -232,6 +232,12 @@ Here are a few things to try:
 
    (Understanding the output is beyond the scope of this document!)
 
+ * You can test your Matrix homeserver TURN setup with https://test.voip.librepush.net/.
+   Note that this test is not fully reliable yet, so don't be discouraged if
+   the test fails.
+   [Here](https://github.com/matrix-org/voip-tester) is the github repo of the
+   source of the tester, where you can file bug reports.
+
  * There is a WebRTC test tool at
    https://webrtc.github.io/samples/src/content/peerconnection/trickle-ice/. To
    use it, you will need a username/password for your TURN server. You can
diff --git a/docs/workers.md b/docs/workers.md
index d01683681f..f7fc6df119 100644
--- a/docs/workers.md
+++ b/docs/workers.md
@@ -40,6 +40,9 @@ which relays replication commands between processes. This can give a significant
 cpu saving on the main process and will be a prerequisite for upcoming
 performance improvements.
 
+If Redis support is enabled Synapse will use it as a shared cache, as well as a
+pub/sub mechanism.
+
 See the [Architectural diagram](#architectural-diagram) section at the end for
 a visualisation of what this looks like.
 
@@ -225,7 +228,6 @@ expressions:
     ^/_matrix/client/(api/v1|r0|unstable)/joined_groups$
     ^/_matrix/client/(api/v1|r0|unstable)/publicised_groups$
     ^/_matrix/client/(api/v1|r0|unstable)/publicised_groups/
-    ^/_synapse/client/password_reset/email/submit_token$
 
     # Registration/login requests
     ^/_matrix/client/(api/v1|r0|unstable)/login$
@@ -256,25 +258,29 @@ Additionally, the following endpoints should be included if Synapse is configure
 to use SSO (you only need to include the ones for whichever SSO provider you're
 using):
 
+    # for all SSO providers
+    ^/_matrix/client/(api/v1|r0|unstable)/login/sso/redirect
+    ^/_synapse/client/pick_idp$
+    ^/_synapse/client/pick_username
+    ^/_synapse/client/new_user_consent$
+    ^/_synapse/client/sso_register$
+
     # OpenID Connect requests.
-    ^/_matrix/client/(api/v1|r0|unstable)/login/sso/redirect$
-    ^/_synapse/oidc/callback$
+    ^/_synapse/client/oidc/callback$
 
     # SAML requests.
-    ^/_matrix/client/(api/v1|r0|unstable)/login/sso/redirect$
-    ^/_matrix/saml2/authn_response$
+    ^/_synapse/client/saml2/authn_response$
 
     # CAS requests.
-    ^/_matrix/client/(api/v1|r0|unstable)/login/(cas|sso)/redirect$
     ^/_matrix/client/(api/v1|r0|unstable)/login/cas/ticket$
 
-Note that a HTTP listener with `client` and `federation` resources must be
-configured in the `worker_listeners` option in the worker config.
-
-Ensure that all SSO logins go to a single process (usually the main process). 
+Ensure that all SSO logins go to a single process.
 For multiple workers not handling the SSO endpoints properly, see
 [#7530](https://github.com/matrix-org/synapse/issues/7530).
 
+Note that a HTTP listener with `client` and `federation` resources must be
+configured in the `worker_listeners` option in the worker config.
+
 #### Load balancing
 
 It is possible to run multiple instances of this worker app, with incoming requests
diff --git a/mypy.ini b/mypy.ini
index b996867121..68a4533973 100644
--- a/mypy.ini
+++ b/mypy.ini
@@ -23,39 +23,7 @@ files =
   synapse/events/validator.py,
   synapse/events/spamcheck.py,
   synapse/federation,
-  synapse/handlers/_base.py,
-  synapse/handlers/account_data.py,
-  synapse/handlers/account_validity.py,
-  synapse/handlers/admin.py,
-  synapse/handlers/appservice.py,
-  synapse/handlers/auth.py,
-  synapse/handlers/cas_handler.py,
-  synapse/handlers/deactivate_account.py,
-  synapse/handlers/device.py,
-  synapse/handlers/devicemessage.py,
-  synapse/handlers/directory.py,
-  synapse/handlers/events.py,
-  synapse/handlers/federation.py,
-  synapse/handlers/identity.py,
-  synapse/handlers/initial_sync.py,
-  synapse/handlers/message.py,
-  synapse/handlers/oidc_handler.py,
-  synapse/handlers/pagination.py,
-  synapse/handlers/password_policy.py,
-  synapse/handlers/presence.py,
-  synapse/handlers/profile.py,
-  synapse/handlers/read_marker.py,
-  synapse/handlers/receipts.py,
-  synapse/handlers/register.py,
-  synapse/handlers/room.py,
-  synapse/handlers/room_list.py,
-  synapse/handlers/room_member.py,
-  synapse/handlers/room_member_worker.py,
-  synapse/handlers/saml_handler.py,
-  synapse/handlers/sso.py,
-  synapse/handlers/sync.py,
-  synapse/handlers/user_directory.py,
-  synapse/handlers/ui_auth,
+  synapse/handlers,
   synapse/http/client.py,
   synapse/http/federation/matrix_federation_agent.py,
   synapse/http/federation/well_known_resolver.py,
@@ -100,6 +68,7 @@ files =
   synapse/util/async_helpers.py,
   synapse/util/caches,
   synapse/util/metrics.py,
+  synapse/util/stringutils.py,
   tests/replication,
   tests/test_utils,
   tests/handlers/test_password_providers.py,
@@ -193,3 +162,9 @@ ignore_missing_imports = True
 
 [mypy-hiredis]
 ignore_missing_imports = True
+
+[mypy-josepy.*]
+ignore_missing_imports = True
+
+[mypy-txacme.*]
+ignore_missing_imports = True
diff --git a/scripts-dev/lint.sh b/scripts-dev/lint.sh
index f328ab57d5..fe2965cd36 100755
--- a/scripts-dev/lint.sh
+++ b/scripts-dev/lint.sh
@@ -80,7 +80,8 @@ else
   # then lint everything!
   if [[ -z ${files+x} ]]; then
     # Lint all source code files and directories
-    files=("synapse" "tests" "scripts-dev" "scripts" "contrib" "synctl" "setup.py" "synmark")
+    # Note: this list aims the mirror the one in tox.ini
+    files=("synapse" "docker" "tests" "scripts-dev" "scripts" "contrib" "synctl" "setup.py" "synmark" "stubs" ".buildkite")
   fi
 fi
 
diff --git a/setup.py b/setup.py
index 9730afb41b..99425d52de 100755
--- a/setup.py
+++ b/setup.py
@@ -96,7 +96,7 @@ CONDITIONAL_REQUIREMENTS["all"] = list(ALL_OPTIONAL_REQUIREMENTS)
 #
 # We pin black so that our tests don't start failing on new releases.
 CONDITIONAL_REQUIREMENTS["lint"] = [
-    "isort==5.0.3",
+    "isort==5.7.0",
     "black==19.10b0",
     "flake8-comprehensions",
     "flake8",
@@ -121,6 +121,7 @@ setup(
     include_package_data=True,
     zip_safe=False,
     long_description=long_description,
+    long_description_content_type="text/x-rst",
     python_requires="~=3.5",
     classifiers=[
         "Development Status :: 5 - Production/Stable",
diff --git a/stubs/txredisapi.pyi b/stubs/txredisapi.pyi
index bfac6840e6..618548a305 100644
--- a/stubs/txredisapi.pyi
+++ b/stubs/txredisapi.pyi
@@ -15,13 +15,23 @@
 
 """Contains *incomplete* type hints for txredisapi.
 """
-
-from typing import List, Optional, Type, Union
+from typing import Any, List, Optional, Type, Union
 
 class RedisProtocol:
     def publish(self, channel: str, message: bytes): ...
+    async def ping(self) -> None: ...
+    async def set(
+        self,
+        key: str,
+        value: Any,
+        expire: Optional[int] = None,
+        pexpire: Optional[int] = None,
+        only_if_not_exists: bool = False,
+        only_if_exists: bool = False,
+    ) -> None: ...
+    async def get(self, key: str) -> Any: ...
 
-class SubscriberProtocol:
+class SubscriberProtocol(RedisProtocol):
     def __init__(self, *args, **kwargs): ...
     password: Optional[str]
     def subscribe(self, channels: Union[str, List[str]]): ...
@@ -40,14 +50,13 @@ def lazyConnection(
     convertNumbers: bool = ...,
 ) -> RedisProtocol: ...
 
-class SubscriberFactory:
-    def buildProtocol(self, addr): ...
-
 class ConnectionHandler: ...
 
 class RedisFactory:
     continueTrying: bool
     handler: RedisProtocol
+    pool: List[RedisProtocol]
+    replyTimeout: Optional[int]
     def __init__(
         self,
         uuid: str,
@@ -60,3 +69,7 @@ class RedisFactory:
         replyTimeout: Optional[int] = None,
         convertNumbers: Optional[int] = True,
     ): ...
+    def buildProtocol(self, addr) -> RedisProtocol: ...
+
+class SubscriberFactory(RedisFactory):
+    def __init__(self): ...
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 193adca624..06b3820be5 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -48,7 +48,7 @@ try:
 except ImportError:
     pass
 
-__version__ = "1.25.0"
+__version__ = "1.27.0rc1"
 
 if bool(os.environ.get("SYNAPSE_TEST_PATCH_LOG_CONTEXTS", False)):
     # We import here so that we don't have to install a bunch of deps when
diff --git a/synapse/api/urls.py b/synapse/api/urls.py
index 6379c86dde..e36aeef31f 100644
--- a/synapse/api/urls.py
+++ b/synapse/api/urls.py
@@ -42,8 +42,6 @@ class ConsentURIBuilder:
         """
         if hs_config.form_secret is None:
             raise ConfigError("form_secret not set in config")
-        if hs_config.public_baseurl is None:
-            raise ConfigError("public_baseurl not set in config")
 
         self._hmac_secret = hs_config.form_secret.encode("utf-8")
         self._public_baseurl = hs_config.public_baseurl
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 395e202b89..9840a9d55b 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -16,6 +16,7 @@
 import gc
 import logging
 import os
+import platform
 import signal
 import socket
 import sys
@@ -339,7 +340,7 @@ async def start(hs: "synapse.server.HomeServer", listeners: Iterable[ListenerCon
     # rest of time. Doing so means less work each GC (hopefully).
     #
     # This only works on Python 3.7
-    if sys.version_info >= (3, 7):
+    if platform.python_implementation() == "CPython" and sys.version_info >= (3, 7):
         gc.collect()
         gc.freeze()
 
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index e60988fa4a..516f2464b4 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -22,6 +22,7 @@ from typing import Dict, Iterable, Optional, Set
 from typing_extensions import ContextManager
 
 from twisted.internet import address
+from twisted.web.resource import IResource
 
 import synapse
 import synapse.events
@@ -90,9 +91,8 @@ from synapse.replication.tcp.streams import (
     ToDeviceStream,
 )
 from synapse.rest.admin import register_servlets_for_media_repo
-from synapse.rest.client.v1 import events, room
+from synapse.rest.client.v1 import events, login, room
 from synapse.rest.client.v1.initial_sync import InitialSyncRestServlet
-from synapse.rest.client.v1.login import LoginRestServlet
 from synapse.rest.client.v1.profile import (
     ProfileAvatarURLRestServlet,
     ProfileDisplaynameRestServlet,
@@ -127,6 +127,7 @@ from synapse.rest.client.v2_alpha.sendtodevice import SendToDeviceRestServlet
 from synapse.rest.client.versions import VersionsRestServlet
 from synapse.rest.health import HealthResource
 from synapse.rest.key.v2 import KeyApiV2Resource
+from synapse.rest.synapse.client import build_synapse_client_resource_tree
 from synapse.server import HomeServer, cache_in_self
 from synapse.storage.databases.main.censor_events import CensorEventsStore
 from synapse.storage.databases.main.client_ips import ClientIpWorkerStore
@@ -507,7 +508,7 @@ class GenericWorkerServer(HomeServer):
             site_tag = port
 
         # We always include a health resource.
-        resources = {"/health": HealthResource()}
+        resources = {"/health": HealthResource()}  # type: Dict[str, IResource]
 
         for res in listener_config.http_options.resources:
             for name in res.names:
@@ -517,7 +518,7 @@ class GenericWorkerServer(HomeServer):
                     resource = JsonResource(self, canonical_json=False)
 
                     RegisterRestServlet(self).register(resource)
-                    LoginRestServlet(self).register(resource)
+                    login.register_servlets(self, resource)
                     ThreepidRestServlet(self).register(resource)
                     DevicesRestServlet(self).register(resource)
                     KeyQueryServlet(self).register(resource)
@@ -557,6 +558,8 @@ class GenericWorkerServer(HomeServer):
                     groups.register_servlets(self, resource)
 
                     resources.update({CLIENT_API_PREFIX: resource})
+
+                    resources.update(build_synapse_client_resource_tree(self))
                 elif name == "federation":
                     resources.update({FEDERATION_PREFIX: TransportLayerServer(self)})
                 elif name == "media":
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 57a2f5237c..244657cb88 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -60,8 +60,7 @@ from synapse.rest import ClientRestResource
 from synapse.rest.admin import AdminRestResource
 from synapse.rest.health import HealthResource
 from synapse.rest.key.v2 import KeyApiV2Resource
-from synapse.rest.synapse.client.pick_idp import PickIdpResource
-from synapse.rest.synapse.client.pick_username import pick_username_resource
+from synapse.rest.synapse.client import build_synapse_client_resource_tree
 from synapse.rest.well_known import WellKnownResource
 from synapse.server import HomeServer
 from synapse.storage import DataStore
@@ -190,21 +189,10 @@ class SynapseHomeServer(HomeServer):
                     "/_matrix/client/versions": client_resource,
                     "/.well-known/matrix/client": WellKnownResource(self),
                     "/_synapse/admin": AdminRestResource(self),
-                    "/_synapse/client/pick_username": pick_username_resource(self),
-                    "/_synapse/client/pick_idp": PickIdpResource(self),
+                    **build_synapse_client_resource_tree(self),
                 }
             )
 
-            if self.get_config().oidc_enabled:
-                from synapse.rest.oidc import OIDCResource
-
-                resources["/_synapse/oidc"] = OIDCResource(self)
-
-            if self.get_config().saml2_enabled:
-                from synapse.rest.saml2 import SAML2Resource
-
-                resources["/_matrix/saml2"] = SAML2Resource(self)
-
             if self.get_config().threepid_behaviour_email == ThreepidBehaviour.LOCAL:
                 from synapse.rest.synapse.client.password_reset import (
                     PasswordResetSubmitTokenResource,
diff --git a/synapse/app/phone_stats_home.py b/synapse/app/phone_stats_home.py
index c38cf8231f..8f86cecb76 100644
--- a/synapse/app/phone_stats_home.py
+++ b/synapse/app/phone_stats_home.py
@@ -93,15 +93,20 @@ async def phone_stats_home(hs, stats, stats_process=_stats_process):
 
     stats["daily_active_users"] = await hs.get_datastore().count_daily_users()
     stats["monthly_active_users"] = await hs.get_datastore().count_monthly_users()
+    daily_active_e2ee_rooms = await hs.get_datastore().count_daily_active_e2ee_rooms()
+    stats["daily_active_e2ee_rooms"] = daily_active_e2ee_rooms
+    stats["daily_e2ee_messages"] = await hs.get_datastore().count_daily_e2ee_messages()
+    daily_sent_e2ee_messages = await hs.get_datastore().count_daily_sent_e2ee_messages()
+    stats["daily_sent_e2ee_messages"] = daily_sent_e2ee_messages
     stats["daily_active_rooms"] = await hs.get_datastore().count_daily_active_rooms()
     stats["daily_messages"] = await hs.get_datastore().count_daily_messages()
+    daily_sent_messages = await hs.get_datastore().count_daily_sent_messages()
+    stats["daily_sent_messages"] = daily_sent_messages
 
     r30_results = await hs.get_datastore().count_r30_users()
     for name, count in r30_results.items():
         stats["r30_users_" + name] = count
 
-    daily_sent_messages = await hs.get_datastore().count_daily_sent_messages()
-    stats["daily_sent_messages"] = daily_sent_messages
     stats["cache_factor"] = hs.config.caches.global_factor
     stats["event_cache_size"] = hs.config.caches.event_cache_size
 
diff --git a/synapse/config/_base.py b/synapse/config/_base.py
index 2931a88207..a851f8801d 100644
--- a/synapse/config/_base.py
+++ b/synapse/config/_base.py
@@ -18,18 +18,18 @@
 import argparse
 import errno
 import os
-import time
-import urllib.parse
 from collections import OrderedDict
 from hashlib import sha256
 from textwrap import dedent
-from typing import Any, Callable, Iterable, List, MutableMapping, Optional
+from typing import Any, Iterable, List, MutableMapping, Optional
 
 import attr
 import jinja2
 import pkg_resources
 import yaml
 
+from synapse.util.templates import _create_mxc_to_http_filter, _format_ts_filter
+
 
 class ConfigError(Exception):
     """Represents a problem parsing the configuration
@@ -203,11 +203,28 @@ class Config:
         with open(file_path) as file_stream:
             return file_stream.read()
 
+    def read_template(self, filename: str) -> jinja2.Template:
+        """Load a template file from disk.
+
+        This function will attempt to load the given template from the default Synapse
+        template directory.
+
+        Files read are treated as Jinja templates. The templates is not rendered yet
+        and has autoescape enabled.
+
+        Args:
+            filename: A template filename to read.
+
+        Raises:
+            ConfigError: if the file's path is incorrect or otherwise cannot be read.
+
+        Returns:
+            A jinja2 template.
+        """
+        return self.read_templates([filename])[0]
+
     def read_templates(
-        self,
-        filenames: List[str],
-        custom_template_directory: Optional[str] = None,
-        autoescape: bool = False,
+        self, filenames: List[str], custom_template_directory: Optional[str] = None,
     ) -> List[jinja2.Template]:
         """Load a list of template files from disk using the given variables.
 
@@ -215,7 +232,8 @@ class Config:
         template directory. If `custom_template_directory` is supplied, that directory
         is tried first.
 
-        Files read are treated as Jinja templates. These templates are not rendered yet.
+        Files read are treated as Jinja templates. The templates are not rendered yet
+        and have autoescape enabled.
 
         Args:
             filenames: A list of template filenames to read.
@@ -223,16 +241,12 @@ class Config:
             custom_template_directory: A directory to try to look for the templates
                 before using the default Synapse template directory instead.
 
-            autoescape: Whether to autoescape variables before inserting them into the
-                template.
-
         Raises:
             ConfigError: if the file's path is incorrect or otherwise cannot be read.
 
         Returns:
             A list of jinja2 templates.
         """
-        templates = []
         search_directories = [self.default_template_dir]
 
         # The loader will first look in the custom template directory (if specified) for the
@@ -248,54 +262,20 @@ class Config:
             # Search the custom template directory as well
             search_directories.insert(0, custom_template_directory)
 
+        # TODO: switch to synapse.util.templates.build_jinja_env
         loader = jinja2.FileSystemLoader(search_directories)
-        env = jinja2.Environment(loader=loader, autoescape=autoescape)
+        env = jinja2.Environment(loader=loader, autoescape=jinja2.select_autoescape(),)
 
         # Update the environment with our custom filters
-        env.filters.update({"format_ts": _format_ts_filter})
-        if self.public_baseurl:
-            env.filters.update(
-                {"mxc_to_http": _create_mxc_to_http_filter(self.public_baseurl)}
-            )
-
-        for filename in filenames:
-            # Load the template
-            template = env.get_template(filename)
-            templates.append(template)
-
-        return templates
-
-
-def _format_ts_filter(value: int, format: str):
-    return time.strftime(format, time.localtime(value / 1000))
-
-
-def _create_mxc_to_http_filter(public_baseurl: str) -> Callable:
-    """Create and return a jinja2 filter that converts MXC urls to HTTP
-
-    Args:
-        public_baseurl: The public, accessible base URL of the homeserver
-    """
-
-    def mxc_to_http_filter(value, width, height, resize_method="crop"):
-        if value[0:6] != "mxc://":
-            return ""
-
-        server_and_media_id = value[6:]
-        fragment = None
-        if "#" in server_and_media_id:
-            server_and_media_id, fragment = server_and_media_id.split("#", 1)
-            fragment = "#" + fragment
-
-        params = {"width": width, "height": height, "method": resize_method}
-        return "%s_matrix/media/v1/thumbnail/%s?%s%s" % (
-            public_baseurl,
-            server_and_media_id,
-            urllib.parse.urlencode(params),
-            fragment or "",
+        env.filters.update(
+            {
+                "format_ts": _format_ts_filter,
+                "mxc_to_http": _create_mxc_to_http_filter(self.public_baseurl),
+            }
         )
 
-    return mxc_to_http_filter
+        # Load the templates
+        return [env.get_template(filename) for filename in filenames]
 
 
 class RootConfig:
diff --git a/synapse/config/_base.pyi b/synapse/config/_base.pyi
index 29aa064e57..70025b5d60 100644
--- a/synapse/config/_base.pyi
+++ b/synapse/config/_base.pyi
@@ -9,6 +9,7 @@ from synapse.config import (
     consent_config,
     database,
     emailconfig,
+    experimental,
     groups,
     jwt_config,
     key,
@@ -18,6 +19,7 @@ from synapse.config import (
     password_auth_providers,
     push,
     ratelimiting,
+    redis,
     registration,
     repository,
     room_directory,
@@ -48,10 +50,11 @@ def path_exists(file_path: str): ...
 
 class RootConfig:
     server: server.ServerConfig
+    experimental: experimental.ExperimentalConfig
     tls: tls.TlsConfig
     database: database.DatabaseConfig
     logging: logger.LoggingConfig
-    ratelimit: ratelimiting.RatelimitConfig
+    ratelimiting: ratelimiting.RatelimitConfig
     media: repository.ContentRepositoryConfig
     captcha: captcha.CaptchaConfig
     voip: voip.VoipConfig
@@ -79,6 +82,7 @@ class RootConfig:
     roomdirectory: room_directory.RoomDirectoryConfig
     thirdpartyrules: third_party_event_rules.ThirdPartyRulesConfig
     tracer: tracer.TracerConfig
+    redis: redis.RedisConfig
 
     config_classes: List = ...
     def __init__(self) -> None: ...
diff --git a/synapse/config/captcha.py b/synapse/config/captcha.py
index cb00958165..9e48f865cc 100644
--- a/synapse/config/captcha.py
+++ b/synapse/config/captcha.py
@@ -28,9 +28,7 @@ class CaptchaConfig(Config):
             "recaptcha_siteverify_api",
             "https://www.recaptcha.net/recaptcha/api/siteverify",
         )
-        self.recaptcha_template = self.read_templates(
-            ["recaptcha.html"], autoescape=True
-        )[0]
+        self.recaptcha_template = self.read_template("recaptcha.html")
 
     def generate_config_section(self, **kwargs):
         return """\
diff --git a/synapse/config/cas.py b/synapse/config/cas.py
index c7877b4095..b226890c2a 100644
--- a/synapse/config/cas.py
+++ b/synapse/config/cas.py
@@ -30,7 +30,13 @@ class CasConfig(Config):
 
         if self.cas_enabled:
             self.cas_server_url = cas_config["server_url"]
-            self.cas_service_url = cas_config["service_url"]
+            public_base_url = cas_config.get("service_url") or self.public_baseurl
+            if public_base_url[-1] != "/":
+                public_base_url += "/"
+            # TODO Update this to a _synapse URL.
+            self.cas_service_url = (
+                public_base_url + "_matrix/client/r0/login/cas/ticket"
+            )
             self.cas_displayname_attribute = cas_config.get("displayname_attribute")
             self.cas_required_attributes = cas_config.get("required_attributes") or {}
         else:
@@ -53,10 +59,6 @@ class CasConfig(Config):
           #
           #server_url: "https://cas-server.com"
 
-          # The public URL of the homeserver.
-          #
-          #service_url: "https://homeserver.domain.com:8448"
-
           # The attribute of the CAS response to use as the display name.
           #
           # If unset, no displayname will be set.
diff --git a/synapse/config/consent_config.py b/synapse/config/consent_config.py
index 6efa59b110..c47f364b14 100644
--- a/synapse/config/consent_config.py
+++ b/synapse/config/consent_config.py
@@ -89,7 +89,7 @@ class ConsentConfig(Config):
 
     def read_config(self, config, **kwargs):
         consent_config = config.get("user_consent")
-        self.terms_template = self.read_templates(["terms.html"], autoescape=True)[0]
+        self.terms_template = self.read_template("terms.html")
 
         if consent_config is None:
             return
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index d4328c46b9..6a487afd34 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -166,11 +166,6 @@ class EmailConfig(Config):
             if not self.email_notif_from:
                 missing.append("email.notif_from")
 
-            # public_baseurl is required to build password reset and validation links that
-            # will be emailed to users
-            if config.get("public_baseurl") is None:
-                missing.append("public_baseurl")
-
             if missing:
                 raise ConfigError(
                     MISSING_PASSWORD_RESET_CONFIG_ERROR % (", ".join(missing),)
@@ -269,9 +264,6 @@ class EmailConfig(Config):
             if not self.email_notif_from:
                 missing.append("email.notif_from")
 
-            if config.get("public_baseurl") is None:
-                missing.append("public_baseurl")
-
             if missing:
                 raise ConfigError(
                     "email.enable_notifs is True but required keys are missing: %s"
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
new file mode 100644
index 0000000000..b1c1c51e4d
--- /dev/null
+++ b/synapse/config/experimental.py
@@ -0,0 +1,29 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from synapse.config._base import Config
+from synapse.types import JsonDict
+
+
+class ExperimentalConfig(Config):
+    """Config section for enabling experimental features"""
+
+    section = "experimental"
+
+    def read_config(self, config: JsonDict, **kwargs):
+        experimental = config.get("experimental_features") or {}
+
+        # MSC2858 (multiple SSO identity providers)
+        self.msc2858_enabled = experimental.get("msc2858_enabled", False)  # type: bool
diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index 4bd2b3587b..64a2429f77 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -24,6 +24,7 @@ from .cas import CasConfig
 from .consent_config import ConsentConfig
 from .database import DatabaseConfig
 from .emailconfig import EmailConfig
+from .experimental import ExperimentalConfig
 from .federation import FederationConfig
 from .groups import GroupsConfig
 from .jwt_config import JWTConfig
@@ -57,6 +58,7 @@ class HomeServerConfig(RootConfig):
 
     config_classes = [
         ServerConfig,
+        ExperimentalConfig,
         TlsConfig,
         FederationConfig,
         CacheConfig,
diff --git a/synapse/config/oidc_config.py b/synapse/config/oidc_config.py
index 80a24cfbc9..4c24c50629 100644
--- a/synapse/config/oidc_config.py
+++ b/synapse/config/oidc_config.py
@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import string
+from collections import Counter
 from typing import Iterable, Optional, Tuple, Type
 
 import attr
@@ -23,6 +23,7 @@ from synapse.config._util import validate_config
 from synapse.python_dependencies import DependencyException, check_requirements
 from synapse.types import Collection, JsonDict
 from synapse.util.module_loader import load_module
+from synapse.util.stringutils import parse_and_validate_mxc_uri
 
 from ._base import Config, ConfigError
 
@@ -42,10 +43,17 @@ class OIDCConfig(Config):
         except DependencyException as e:
             raise ConfigError(e.message) from e
 
-        public_baseurl = self.public_baseurl
-        if public_baseurl is None:
-            raise ConfigError("oidc_config requires a public_baseurl to be set")
-        self.oidc_callback_url = public_baseurl + "_synapse/oidc/callback"
+        # check we don't have any duplicate idp_ids now. (The SSO handler will also
+        # check for duplicates when the REST listeners get registered, but that happens
+        # after synapse has forked so doesn't give nice errors.)
+        c = Counter([i.idp_id for i in self.oidc_providers])
+        for idp_id, count in c.items():
+            if count > 1:
+                raise ConfigError(
+                    "Multiple OIDC providers have the idp_id %r." % idp_id
+                )
+
+        self.oidc_callback_url = self.public_baseurl + "_synapse/client/oidc/callback"
 
     @property
     def oidc_enabled(self) -> bool:
@@ -68,6 +76,16 @@ class OIDCConfig(Config):
         #   idp_name: A user-facing name for this identity provider, which is used to
         #       offer the user a choice of login mechanisms.
         #
+        #   idp_icon: An optional icon for this identity provider, which is presented
+        #       by clients and Synapse's own IdP picker page. If given, must be an
+        #       MXC URI of the format mxc://<server-name>/<media-id>. (An easy way to
+        #       obtain such an MXC URI is to upload an image to an (unencrypted) room
+        #       and then copy the "url" from the source of the event.)
+        #
+        #   idp_brand: An optional brand for this identity provider, allowing clients
+        #       to style the login flow according to the identity provider in question.
+        #       See the spec for possible options here.
+        #
         #   discover: set to 'false' to disable the use of the OIDC discovery mechanism
         #       to discover endpoints. Defaults to true.
         #
@@ -127,17 +145,21 @@ class OIDCConfig(Config):
         #
         #           For the default provider, the following settings are available:
         #
-        #             sub: name of the claim containing a unique identifier for the
-        #                 user. Defaults to 'sub', which OpenID Connect compliant
-        #                 providers should provide.
+        #             subject_claim: name of the claim containing a unique identifier
+        #                 for the user. Defaults to 'sub', which OpenID Connect
+        #                 compliant providers should provide.
         #
         #             localpart_template: Jinja2 template for the localpart of the MXID.
         #                 If this is not set, the user will be prompted to choose their
-        #                 own username.
+        #                 own username (see 'sso_auth_account_details.html' in the 'sso'
+        #                 section of this file).
         #
         #             display_name_template: Jinja2 template for the display name to set
         #                 on first login. If unset, no displayname will be set.
         #
+        #             email_template: Jinja2 template for the email address of the user.
+        #                 If unset, no email address will be added to the account.
+        #
         #             extra_attributes: a map of Jinja2 templates for extra attributes
         #                 to send back to the client during login.
         #                 Note that these are non-standard and clients will ignore them
@@ -152,13 +174,16 @@ class OIDCConfig(Config):
         #
         # For backwards compatibility, it is also possible to configure a single OIDC
         # provider via an 'oidc_config' setting. This is now deprecated and admins are
-        # advised to migrate to the 'oidc_providers' format.
+        # advised to migrate to the 'oidc_providers' format. (When doing that migration,
+        # use 'oidc' for the idp_id to ensure that existing users continue to be
+        # recognised.)
         #
         oidc_providers:
           # Generic example
           #
           #- idp_id: my_idp
           #  idp_name: "My OpenID provider"
+          #  idp_icon: "mxc://example.com/mediaid"
           #  discover: false
           #  issuer: "https://accounts.example.com/"
           #  client_id: "provided-by-your-issuer"
@@ -170,6 +195,12 @@ class OIDCConfig(Config):
           #  userinfo_endpoint: "https://accounts.example.com/userinfo"
           #  jwks_uri: "https://accounts.example.com/.well-known/jwks.json"
           #  skip_verification: true
+          #  user_mapping_provider:
+          #    config:
+          #      subject_claim: "id"
+          #      localpart_template: "{{ user.login }}"
+          #      display_name_template: "{{ user.name }}"
+          #      email_template: "{{ user.email }}"
 
           # For use with Keycloak
           #
@@ -182,8 +213,9 @@ class OIDCConfig(Config):
 
           # For use with Github
           #
-          #- idp_id: google
-          #  idp_name: Google
+          #- idp_id: github
+          #  idp_name: Github
+          #  idp_brand: org.matrix.github
           #  discover: false
           #  issuer: "https://github.com/"
           #  client_id: "your-client-id" # TO BE FILLED
@@ -207,8 +239,22 @@ OIDC_PROVIDER_CONFIG_SCHEMA = {
     "type": "object",
     "required": ["issuer", "client_id", "client_secret"],
     "properties": {
-        "idp_id": {"type": "string", "minLength": 1, "maxLength": 128},
+        "idp_id": {
+            "type": "string",
+            "minLength": 1,
+            # MSC2858 allows a maxlen of 255, but we prefix with "oidc-"
+            "maxLength": 250,
+            "pattern": "^[A-Za-z0-9._~-]+$",
+        },
         "idp_name": {"type": "string"},
+        "idp_icon": {"type": "string"},
+        "idp_brand": {
+            "type": "string",
+            # MSC2758-style namespaced identifier
+            "minLength": 1,
+            "maxLength": 255,
+            "pattern": "^[a-z][a-z0-9_.-]*$",
+        },
         "discover": {"type": "boolean"},
         "issuer": {"type": "string"},
         "client_id": {"type": "string"},
@@ -327,20 +373,34 @@ def _parse_oidc_config_dict(
             config_path + ("user_mapping_provider", "module"),
         )
 
-    # MSC2858 will appy certain limits in what can be used as an IdP id, so let's
-    # enforce those limits now.
     idp_id = oidc_config.get("idp_id", "oidc")
-    valid_idp_chars = set(string.ascii_letters + string.digits + "-._~")
 
-    if any(c not in valid_idp_chars for c in idp_id):
-        raise ConfigError(
-            'idp_id may only contain A-Z, a-z, 0-9, "-", ".", "_", "~"',
-            config_path + ("idp_id",),
-        )
+    # prefix the given IDP with a prefix specific to the SSO mechanism, to avoid
+    # clashes with other mechs (such as SAML, CAS).
+    #
+    # We allow "oidc" as an exception so that people migrating from old-style
+    # "oidc_config" format (which has long used "oidc" as its idp_id) can migrate to
+    # a new-style "oidc_providers" entry without changing the idp_id for their provider
+    # (and thereby invalidating their user_external_ids data).
+
+    if idp_id != "oidc":
+        idp_id = "oidc-" + idp_id
+
+    # MSC2858 also specifies that the idp_icon must be a valid MXC uri
+    idp_icon = oidc_config.get("idp_icon")
+    if idp_icon is not None:
+        try:
+            parse_and_validate_mxc_uri(idp_icon)
+        except ValueError as e:
+            raise ConfigError(
+                "idp_icon must be a valid MXC URI", config_path + ("idp_icon",)
+            ) from e
 
     return OidcProviderConfig(
         idp_id=idp_id,
         idp_name=oidc_config.get("idp_name", "OIDC"),
+        idp_icon=idp_icon,
+        idp_brand=oidc_config.get("idp_brand"),
         discover=oidc_config.get("discover", True),
         issuer=oidc_config["issuer"],
         client_id=oidc_config["client_id"],
@@ -368,6 +428,12 @@ class OidcProviderConfig:
     # user-facing name for this identity provider.
     idp_name = attr.ib(type=str)
 
+    # Optional MXC URI for icon for this IdP.
+    idp_icon = attr.ib(type=Optional[str])
+
+    # Optional brand identifier for this IdP.
+    idp_brand = attr.ib(type=Optional[str])
+
     # whether the OIDC discovery mechanism is used to discover endpoints
     discover = attr.ib(type=bool)
 
diff --git a/synapse/config/ratelimiting.py b/synapse/config/ratelimiting.py
index 14b8836197..def33a60ad 100644
--- a/synapse/config/ratelimiting.py
+++ b/synapse/config/ratelimiting.py
@@ -24,7 +24,7 @@ class RateLimitConfig:
         defaults={"per_second": 0.17, "burst_count": 3.0},
     ):
         self.per_second = config.get("per_second", defaults["per_second"])
-        self.burst_count = config.get("burst_count", defaults["burst_count"])
+        self.burst_count = int(config.get("burst_count", defaults["burst_count"]))
 
 
 class FederationRateLimitConfig:
@@ -102,6 +102,20 @@ class RatelimitConfig(Config):
             defaults={"per_second": 0.01, "burst_count": 3},
         )
 
+        self.rc_3pid_validation = RateLimitConfig(
+            config.get("rc_3pid_validation") or {},
+            defaults={"per_second": 0.003, "burst_count": 5},
+        )
+
+        self.rc_invites_per_room = RateLimitConfig(
+            config.get("rc_invites", {}).get("per_room", {}),
+            defaults={"per_second": 0.3, "burst_count": 10},
+        )
+        self.rc_invites_per_user = RateLimitConfig(
+            config.get("rc_invites", {}).get("per_user", {}),
+            defaults={"per_second": 0.003, "burst_count": 5},
+        )
+
     def generate_config_section(self, **kwargs):
         return """\
         ## Ratelimiting ##
@@ -131,6 +145,9 @@ class RatelimitConfig(Config):
         #     users are joining rooms the server is already in (this is cheap) vs
         #     "remote" for when users are trying to join rooms not on the server (which
         #     can be more expensive)
+        #   - one for ratelimiting how often a user or IP can attempt to validate a 3PID.
+        #   - two for ratelimiting how often invites can be sent in a room or to a
+        #     specific user.
         #
         # The defaults are as shown below.
         #
@@ -164,7 +181,18 @@ class RatelimitConfig(Config):
         #  remote:
         #    per_second: 0.01
         #    burst_count: 3
-
+        #
+        #rc_3pid_validation:
+        #  per_second: 0.003
+        #  burst_count: 5
+        #
+        #rc_invites:
+        #  per_room:
+        #    per_second: 0.3
+        #    burst_count: 10
+        #  per_user:
+        #    per_second: 0.003
+        #    burst_count: 5
 
         # Ratelimiting settings for incoming federation
         #
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index 740c3fc1b1..ac48913a0b 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -49,10 +49,6 @@ class AccountValidityConfig(Config):
 
             self.startup_job_max_delta = self.period * 10.0 / 100.0
 
-        if self.renew_by_email_enabled:
-            if "public_baseurl" not in synapse_config:
-                raise ConfigError("Can't send renewal emails without 'public_baseurl'")
-
         template_dir = config.get("template_dir")
 
         if not template_dir:
@@ -109,13 +105,6 @@ class RegistrationConfig(Config):
         account_threepid_delegates = config.get("account_threepid_delegates") or {}
         self.account_threepid_delegate_email = account_threepid_delegates.get("email")
         self.account_threepid_delegate_msisdn = account_threepid_delegates.get("msisdn")
-        if self.account_threepid_delegate_msisdn and not self.public_baseurl:
-            raise ConfigError(
-                "The configuration option `public_baseurl` is required if "
-                "`account_threepid_delegate.msisdn` is set, such that "
-                "clients know where to submit validation tokens to. Please "
-                "configure `public_baseurl`."
-            )
 
         self.default_identity_server = config.get("default_identity_server")
         self.allow_guest_access = config.get("allow_guest_access", False)
@@ -187,9 +176,7 @@ class RegistrationConfig(Config):
         self.session_lifetime = session_lifetime
 
         # The success template used during fallback auth.
-        self.fallback_success_template = self.read_templates(
-            ["auth_success.html"], autoescape=True
-        )[0]
+        self.fallback_success_template = self.read_template("auth_success.html")
 
     def generate_config_section(self, generate_secrets=False, **kwargs):
         if generate_secrets:
@@ -240,8 +227,9 @@ class RegistrationConfig(Config):
           # send an email to the account's email address with a renewal link. By
           # default, no such emails are sent.
           #
-          # If you enable this setting, you will also need to fill out the 'email' and
-          # 'public_baseurl' configuration sections.
+          # If you enable this setting, you will also need to fill out the 'email'
+          # configuration section. You should also check that 'public_baseurl' is set
+          # correctly.
           #
           #renew_at: 1w
 
@@ -332,8 +320,7 @@ class RegistrationConfig(Config):
         # The identity server which we suggest that clients should use when users log
         # in on this server.
         #
-        # (By default, no suggestion is made, so it is left up to the client.
-        # This setting is ignored unless public_baseurl is also set.)
+        # (By default, no suggestion is made, so it is left up to the client.)
         #
         #default_identity_server: https://matrix.org
 
@@ -358,8 +345,6 @@ class RegistrationConfig(Config):
         # by the Matrix Identity Service API specification:
         # https://matrix.org/docs/spec/identity_service/latest
         #
-        # If a delegate is specified, the config option public_baseurl must also be filled out.
-        #
         account_threepid_delegates:
             #email: https://example.com     # Delegate email sending to example.com
             #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
diff --git a/synapse/config/saml2_config.py b/synapse/config/saml2_config.py
index 7b97d4f114..ad865a667f 100644
--- a/synapse/config/saml2_config.py
+++ b/synapse/config/saml2_config.py
@@ -189,15 +189,13 @@ class SAML2Config(Config):
         import saml2
 
         public_baseurl = self.public_baseurl
-        if public_baseurl is None:
-            raise ConfigError("saml2_config requires a public_baseurl to be set")
 
         if self.saml2_grandfathered_mxid_source_attribute:
             optional_attributes.add(self.saml2_grandfathered_mxid_source_attribute)
         optional_attributes -= required_attributes
 
-        metadata_url = public_baseurl + "_matrix/saml2/metadata.xml"
-        response_url = public_baseurl + "_matrix/saml2/authn_response"
+        metadata_url = public_baseurl + "_synapse/client/saml2/metadata.xml"
+        response_url = public_baseurl + "_synapse/client/saml2/authn_response"
         return {
             "entityid": metadata_url,
             "service": {
@@ -235,10 +233,10 @@ class SAML2Config(Config):
         # enable SAML login.
         #
         # Once SAML support is enabled, a metadata file will be exposed at
-        # https://<server>:<port>/_matrix/saml2/metadata.xml, which you may be able to
+        # https://<server>:<port>/_synapse/client/saml2/metadata.xml, which you may be able to
         # use to configure your SAML IdP with. Alternatively, you can manually configure
         # the IdP to use an ACS location of
-        # https://<server>:<port>/_matrix/saml2/authn_response.
+        # https://<server>:<port>/_synapse/client/saml2/authn_response.
         #
         saml2_config:
           # `sp_config` is the configuration for the pysaml2 Service Provider.
diff --git a/synapse/config/server.py b/synapse/config/server.py
index 7242a4aa8e..47a0370173 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -26,7 +26,7 @@ import yaml
 from netaddr import IPSet
 
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
-from synapse.http.endpoint import parse_and_validate_server_name
+from synapse.util.stringutils import parse_and_validate_server_name
 
 from ._base import Config, ConfigError
 
@@ -161,7 +161,11 @@ class ServerConfig(Config):
         self.print_pidfile = config.get("print_pidfile")
         self.user_agent_suffix = config.get("user_agent_suffix")
         self.use_frozen_dicts = config.get("use_frozen_dicts", False)
-        self.public_baseurl = config.get("public_baseurl")
+        self.public_baseurl = config.get("public_baseurl") or "https://%s/" % (
+            self.server_name,
+        )
+        if self.public_baseurl[-1] != "/":
+            self.public_baseurl += "/"
 
         # Whether to enable user presence.
         self.use_presence = config.get("use_presence", True)
@@ -317,9 +321,6 @@ class ServerConfig(Config):
         # Always blacklist 0.0.0.0, ::
         self.federation_ip_range_blacklist.update(["0.0.0.0", "::"])
 
-        if self.public_baseurl is not None:
-            if self.public_baseurl[-1] != "/":
-                self.public_baseurl += "/"
         self.start_pushers = config.get("start_pushers", True)
 
         # (undocumented) option for torturing the worker-mode replication a bit,
@@ -740,11 +741,16 @@ class ServerConfig(Config):
         #
         #web_client_location: https://riot.example.com/
 
-        # The public-facing base URL that clients use to access this HS
-        # (not including _matrix/...). This is the same URL a user would
-        # enter into the 'custom HS URL' field on their client. If you
-        # use synapse with a reverse proxy, this should be the URL to reach
-        # synapse via the proxy.
+        # The public-facing base URL that clients use to access this Homeserver (not
+        # including _matrix/...). This is the same URL a user might enter into the
+        # 'Custom Homeserver URL' field on their client. If you use Synapse with a
+        # reverse proxy, this should be the URL to reach Synapse via the proxy.
+        # Otherwise, it should be the URL to reach Synapse's client HTTP listener (see
+        # 'listeners' below).
+        #
+        # If this is left unset, it defaults to 'https://<server_name>/'. (Note that
+        # that will not work unless you configure Synapse or a reverse-proxy to listen
+        # on port 443.)
         #
         #public_baseurl: https://example.com/
 
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index 366f0d4698..939eeac6de 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -27,7 +27,7 @@ class SSOConfig(Config):
         sso_config = config.get("sso") or {}  # type: Dict[str, Any]
 
         # The sso-specific template_dir
-        template_dir = sso_config.get("template_dir")
+        self.sso_template_dir = sso_config.get("template_dir")
 
         # Read templates from disk
         (
@@ -48,7 +48,7 @@ class SSOConfig(Config):
                 "sso_auth_success.html",
                 "sso_auth_bad_user.html",
             ],
-            template_dir,
+            self.sso_template_dir,
         )
 
         # These templates have no placeholders, so render them here
@@ -64,11 +64,8 @@ class SSOConfig(Config):
         # gracefully to the client). This would make it pointless to ask the user for
         # confirmation, since the URL the confirmation page would be showing wouldn't be
         # the client's.
-        # public_baseurl is an optional setting, so we only add the fallback's URL to the
-        # list if it's provided (because we can't figure out what that URL is otherwise).
-        if self.public_baseurl:
-            login_fallback_url = self.public_baseurl + "_matrix/static/client/login"
-            self.sso_client_whitelist.append(login_fallback_url)
+        login_fallback_url = self.public_baseurl + "_matrix/static/client/login"
+        self.sso_client_whitelist.append(login_fallback_url)
 
     def generate_config_section(self, **kwargs):
         return """\
@@ -86,9 +83,9 @@ class SSOConfig(Config):
             # phishing attacks from evil.site. To avoid this, include a slash after the
             # hostname: "https://my.client/".
             #
-            # If public_baseurl is set, then the login fallback page (used by clients
-            # that don't natively support the required login flows) is whitelisted in
-            # addition to any URLs in this list.
+            # The login fallback page (used by clients that don't natively support the
+            # required login flows) is automatically whitelisted in addition to any URLs
+            # in this list.
             #
             # By default, this list is empty.
             #
@@ -116,8 +113,13 @@ class SSOConfig(Config):
             #
             #     * providers: a list of available Identity Providers. Each element is
             #       an object with the following attributes:
+            #
             #         * idp_id: unique identifier for the IdP
             #         * idp_name: user-facing name for the IdP
+            #         * idp_icon: if specified in the IdP config, an MXC URI for an icon
+            #              for the IdP
+            #         * idp_brand: if specified in the IdP config, a textual identifier
+            #              for the brand of the IdP
             #
             #   The rendered HTML page should contain a form which submits its results
             #   back as a GET request, with the following query parameters:
@@ -127,10 +129,62 @@ class SSOConfig(Config):
             #
             #     * idp: the 'idp_id' of the chosen IDP.
             #
+            # * HTML page to prompt new users to enter a userid and confirm other
+            #   details: 'sso_auth_account_details.html'. This is only shown if the
+            #   SSO implementation (with any user_mapping_provider) does not return
+            #   a localpart.
+            #
+            #   When rendering, this template is given the following variables:
+            #
+            #     * server_name: the homeserver's name.
+            #
+            #     * idp: details of the SSO Identity Provider that the user logged in
+            #       with: an object with the following attributes:
+            #
+            #         * idp_id: unique identifier for the IdP
+            #         * idp_name: user-facing name for the IdP
+            #         * idp_icon: if specified in the IdP config, an MXC URI for an icon
+            #              for the IdP
+            #         * idp_brand: if specified in the IdP config, a textual identifier
+            #              for the brand of the IdP
+            #
+            #     * user_attributes: an object containing details about the user that
+            #       we received from the IdP. May have the following attributes:
+            #
+            #         * display_name: the user's display_name
+            #         * emails: a list of email addresses
+            #
+            #   The template should render a form which submits the following fields:
+            #
+            #     * username: the localpart of the user's chosen user id
+            #
+            # * HTML page allowing the user to consent to the server's terms and
+            #   conditions. This is only shown for new users, and only if
+            #   `user_consent.require_at_registration` is set.
+            #
+            #   When rendering, this template is given the following variables:
+            #
+            #     * server_name: the homeserver's name.
+            #
+            #     * user_id: the user's matrix proposed ID.
+            #
+            #     * user_profile.display_name: the user's proposed display name, if any.
+            #
+            #     * consent_version: the version of the terms that the user will be
+            #       shown
+            #
+            #     * terms_url: a link to the page showing the terms.
+            #
+            #   The template should render a form which submits the following fields:
+            #
+            #     * accepted_version: the version of the terms accepted by the user
+            #       (ie, 'consent_version' from the input variables).
+            #
             # * HTML page for a confirmation step before redirecting back to the client
             #   with the login token: 'sso_redirect_confirm.html'.
             #
-            #   When rendering, this template is given three variables:
+            #   When rendering, this template is given the following variables:
+            #
             #     * redirect_url: the URL the user is about to be redirected to. Needs
             #                     manual escaping (see
             #                     https://jinja.palletsprojects.com/en/2.11.x/templates/#html-escaping).
@@ -143,6 +197,17 @@ class SSOConfig(Config):
             #
             #     * server_name: the homeserver's name.
             #
+            #     * new_user: a boolean indicating whether this is the user's first time
+            #          logging in.
+            #
+            #     * user_id: the user's matrix ID.
+            #
+            #     * user_profile.avatar_url: an MXC URI for the user's avatar, if any.
+            #           None if the user has not set an avatar.
+            #
+            #     * user_profile.display_name: the user's display name. None if the user
+            #           has not set a display name.
+            #
             # * HTML page which notifies the user that they are authenticating to confirm
             #   an operation on their account during the user interactive authentication
             #   process: 'sso_auth_confirm.html'.
@@ -154,6 +219,16 @@ class SSOConfig(Config):
             #
             #     * description: the operation which the user is being asked to confirm
             #
+            #     * idp: details of the Identity Provider that we will use to confirm
+            #       the user's identity: an object with the following attributes:
+            #
+            #         * idp_id: unique identifier for the IdP
+            #         * idp_name: user-facing name for the IdP
+            #         * idp_icon: if specified in the IdP config, an MXC URI for an icon
+            #              for the IdP
+            #         * idp_brand: if specified in the IdP config, a textual identifier
+            #              for the brand of the IdP
+            #
             # * HTML page shown after a successful user interactive authentication session:
             #   'sso_auth_success.html'.
             #
diff --git a/synapse/crypto/context_factory.py b/synapse/crypto/context_factory.py
index 74b67b230a..14b21796d9 100644
--- a/synapse/crypto/context_factory.py
+++ b/synapse/crypto/context_factory.py
@@ -125,19 +125,24 @@ class FederationPolicyForHTTPS:
         self._no_verify_ssl_context = _no_verify_ssl.getContext()
         self._no_verify_ssl_context.set_info_callback(_context_info_cb)
 
-    def get_options(self, host: bytes):
+        self._should_verify = self._config.federation_verify_certificates
+
+        self._federation_certificate_verification_whitelist = (
+            self._config.federation_certificate_verification_whitelist
+        )
 
+    def get_options(self, host: bytes):
         # IPolicyForHTTPS.get_options takes bytes, but we want to compare
         # against the str whitelist. The hostnames in the whitelist are already
         # IDNA-encoded like the hosts will be here.
         ascii_host = host.decode("ascii")
 
         # Check if certificate verification has been enabled
-        should_verify = self._config.federation_verify_certificates
+        should_verify = self._should_verify
 
         # Check if we've disabled certificate verification for this host
-        if should_verify:
-            for regex in self._config.federation_certificate_verification_whitelist:
+        if self._should_verify:
+            for regex in self._federation_certificate_verification_whitelist:
                 if regex.match(ascii_host):
                     should_verify = False
                     break
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 302b2f69bc..40e1451201 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -18,6 +18,7 @@ import copy
 import itertools
 import logging
 from typing import (
+    TYPE_CHECKING,
     Any,
     Awaitable,
     Callable,
@@ -26,7 +27,6 @@ from typing import (
     List,
     Mapping,
     Optional,
-    Sequence,
     Tuple,
     TypeVar,
     Union,
@@ -61,6 +61,9 @@ from synapse.util import unwrapFirstError
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.retryutils import NotRetryingDestination
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
 sent_queries_counter = Counter("synapse_federation_client_sent_queries", "", ["type"])
@@ -80,10 +83,10 @@ class InvalidResponseError(RuntimeError):
 
 
 class FederationClient(FederationBase):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
-        self.pdu_destination_tried = {}
+        self.pdu_destination_tried = {}  # type: Dict[str, Dict[str, int]]
         self._clock.looping_call(self._clear_tried_cache, 60 * 1000)
         self.state = hs.get_state_handler()
         self.transport_layer = hs.get_federation_transport_client()
@@ -116,33 +119,32 @@ class FederationClient(FederationBase):
                 self.pdu_destination_tried[event_id] = destination_dict
 
     @log_function
-    def make_query(
+    async def make_query(
         self,
-        destination,
-        query_type,
-        args,
-        retry_on_dns_fail=False,
-        ignore_backoff=False,
-    ):
+        destination: str,
+        query_type: str,
+        args: dict,
+        retry_on_dns_fail: bool = False,
+        ignore_backoff: bool = False,
+    ) -> JsonDict:
         """Sends a federation Query to a remote homeserver of the given type
         and arguments.
 
         Args:
-            destination (str): Domain name of the remote homeserver
-            query_type (str): Category of the query type; should match the
+            destination: Domain name of the remote homeserver
+            query_type: Category of the query type; should match the
                 handler name used in register_query_handler().
-            args (dict): Mapping of strings to strings containing the details
+            args: Mapping of strings to strings containing the details
                 of the query request.
-            ignore_backoff (bool): true to ignore the historical backoff data
+            ignore_backoff: true to ignore the historical backoff data
                 and try the request anyway.
 
         Returns:
-            a Awaitable which will eventually yield a JSON object from the
-            response
+            The JSON object from the response
         """
         sent_queries_counter.labels(query_type).inc()
 
-        return self.transport_layer.make_query(
+        return await self.transport_layer.make_query(
             destination,
             query_type,
             args,
@@ -151,42 +153,52 @@ class FederationClient(FederationBase):
         )
 
     @log_function
-    def query_client_keys(self, destination, content, timeout):
+    async def query_client_keys(
+        self, destination: str, content: JsonDict, timeout: int
+    ) -> JsonDict:
         """Query device keys for a device hosted on a remote server.
 
         Args:
-            destination (str): Domain name of the remote homeserver
-            content (dict): The query content.
+            destination: Domain name of the remote homeserver
+            content: The query content.
 
         Returns:
-            an Awaitable which will eventually yield a JSON object from the
-            response
+            The JSON object from the response
         """
         sent_queries_counter.labels("client_device_keys").inc()
-        return self.transport_layer.query_client_keys(destination, content, timeout)
+        return await self.transport_layer.query_client_keys(
+            destination, content, timeout
+        )
 
     @log_function
-    def query_user_devices(self, destination, user_id, timeout=30000):
+    async def query_user_devices(
+        self, destination: str, user_id: str, timeout: int = 30000
+    ) -> JsonDict:
         """Query the device keys for a list of user ids hosted on a remote
         server.
         """
         sent_queries_counter.labels("user_devices").inc()
-        return self.transport_layer.query_user_devices(destination, user_id, timeout)
+        return await self.transport_layer.query_user_devices(
+            destination, user_id, timeout
+        )
 
     @log_function
-    def claim_client_keys(self, destination, content, timeout):
+    async def claim_client_keys(
+        self, destination: str, content: JsonDict, timeout: int
+    ) -> JsonDict:
         """Claims one-time keys for a device hosted on a remote server.
 
         Args:
-            destination (str): Domain name of the remote homeserver
-            content (dict): The query content.
+            destination: Domain name of the remote homeserver
+            content: The query content.
 
         Returns:
-            an Awaitable which will eventually yield a JSON object from the
-            response
+            The JSON object from the response
         """
         sent_queries_counter.labels("client_one_time_keys").inc()
-        return self.transport_layer.claim_client_keys(destination, content, timeout)
+        return await self.transport_layer.claim_client_keys(
+            destination, content, timeout
+        )
 
     async def backfill(
         self, dest: str, room_id: str, limit: int, extremities: Iterable[str]
@@ -195,10 +207,10 @@ class FederationClient(FederationBase):
         given destination server.
 
         Args:
-            dest (str): The remote homeserver to ask.
-            room_id (str): The room_id to backfill.
-            limit (int): The maximum number of events to return.
-            extremities (list): our current backwards extremities, to backfill from
+            dest: The remote homeserver to ask.
+            room_id: The room_id to backfill.
+            limit: The maximum number of events to return.
+            extremities: our current backwards extremities, to backfill from
         """
         logger.debug("backfill extrem=%s", extremities)
 
@@ -370,7 +382,7 @@ class FederationClient(FederationBase):
                 for events that have failed their checks
 
         Returns:
-            Deferred : A list of PDUs that have valid signatures and hashes.
+            A list of PDUs that have valid signatures and hashes.
         """
         deferreds = self._check_sigs_and_hashes(room_version, pdus)
 
@@ -418,7 +430,9 @@ class FederationClient(FederationBase):
         else:
             return [p for p in valid_pdus if p]
 
-    async def get_event_auth(self, destination, room_id, event_id):
+    async def get_event_auth(
+        self, destination: str, room_id: str, event_id: str
+    ) -> List[EventBase]:
         res = await self.transport_layer.get_event_auth(destination, room_id, event_id)
 
         room_version = await self.store.get_room_version(room_id)
@@ -700,18 +714,16 @@ class FederationClient(FederationBase):
 
         return await self._try_destination_list("send_join", destinations, send_request)
 
-    async def _do_send_join(self, destination: str, pdu: EventBase):
+    async def _do_send_join(self, destination: str, pdu: EventBase) -> JsonDict:
         time_now = self._clock.time_msec()
 
         try:
-            content = await self.transport_layer.send_join_v2(
+            return await self.transport_layer.send_join_v2(
                 destination=destination,
                 room_id=pdu.room_id,
                 event_id=pdu.event_id,
                 content=pdu.get_pdu_json(time_now),
             )
-
-            return content
         except HttpResponseException as e:
             if e.code in [400, 404]:
                 err = e.to_synapse_error()
@@ -769,7 +781,7 @@ class FederationClient(FederationBase):
         time_now = self._clock.time_msec()
 
         try:
-            content = await self.transport_layer.send_invite_v2(
+            return await self.transport_layer.send_invite_v2(
                 destination=destination,
                 room_id=pdu.room_id,
                 event_id=pdu.event_id,
@@ -779,7 +791,6 @@ class FederationClient(FederationBase):
                     "invite_room_state": pdu.unsigned.get("invite_room_state", []),
                 },
             )
-            return content
         except HttpResponseException as e:
             if e.code in [400, 404]:
                 err = e.to_synapse_error()
@@ -799,7 +810,7 @@ class FederationClient(FederationBase):
                         "User's homeserver does not support this room version",
                         Codes.UNSUPPORTED_ROOM_VERSION,
                     )
-            elif e.code == 403:
+            elif e.code in (403, 429):
                 raise e.to_synapse_error()
             else:
                 raise
@@ -842,18 +853,16 @@ class FederationClient(FederationBase):
             "send_leave", destinations, send_request
         )
 
-    async def _do_send_leave(self, destination, pdu):
+    async def _do_send_leave(self, destination: str, pdu: EventBase) -> JsonDict:
         time_now = self._clock.time_msec()
 
         try:
-            content = await self.transport_layer.send_leave_v2(
+            return await self.transport_layer.send_leave_v2(
                 destination=destination,
                 room_id=pdu.room_id,
                 event_id=pdu.event_id,
                 content=pdu.get_pdu_json(time_now),
             )
-
-            return content
         except HttpResponseException as e:
             if e.code in [400, 404]:
                 err = e.to_synapse_error()
@@ -879,7 +888,7 @@ class FederationClient(FederationBase):
         # content.
         return resp[1]
 
-    def get_public_rooms(
+    async def get_public_rooms(
         self,
         remote_server: str,
         limit: Optional[int] = None,
@@ -887,7 +896,7 @@ class FederationClient(FederationBase):
         search_filter: Optional[Dict] = None,
         include_all_networks: bool = False,
         third_party_instance_id: Optional[str] = None,
-    ):
+    ) -> JsonDict:
         """Get the list of public rooms from a remote homeserver
 
         Args:
@@ -901,8 +910,7 @@ class FederationClient(FederationBase):
                 party instance
 
         Returns:
-            Awaitable[Dict[str, Any]]: The response from the remote server, or None if
-            `remote_server` is the same as the local server_name
+            The response from the remote server.
 
         Raises:
             HttpResponseException: There was an exception returned from the remote server
@@ -910,7 +918,7 @@ class FederationClient(FederationBase):
                 requests over federation
 
         """
-        return self.transport_layer.get_public_rooms(
+        return await self.transport_layer.get_public_rooms(
             remote_server,
             limit,
             since_token,
@@ -923,7 +931,7 @@ class FederationClient(FederationBase):
         self,
         destination: str,
         room_id: str,
-        earliest_events_ids: Sequence[str],
+        earliest_events_ids: Iterable[str],
         latest_events: Iterable[EventBase],
         limit: int,
         min_depth: int,
@@ -974,7 +982,9 @@ class FederationClient(FederationBase):
 
         return signed_events
 
-    async def forward_third_party_invite(self, destinations, room_id, event_dict):
+    async def forward_third_party_invite(
+        self, destinations: Iterable[str], room_id: str, event_dict: JsonDict
+    ) -> None:
         for destination in destinations:
             if destination == self.server_name:
                 continue
@@ -983,7 +993,7 @@ class FederationClient(FederationBase):
                 await self.transport_layer.exchange_third_party_invite(
                     destination=destination, room_id=room_id, event_dict=event_dict
                 )
-                return None
+                return
             except CodeMessageException:
                 raise
             except Exception as e:
@@ -995,7 +1005,7 @@ class FederationClient(FederationBase):
 
     async def get_room_complexity(
         self, destination: str, room_id: str
-    ) -> Optional[dict]:
+    ) -> Optional[JsonDict]:
         """
         Fetch the complexity of a remote room from another server.
 
@@ -1008,10 +1018,9 @@ class FederationClient(FederationBase):
             could not fetch the complexity.
         """
         try:
-            complexity = await self.transport_layer.get_room_complexity(
+            return await self.transport_layer.get_room_complexity(
                 destination=destination, room_id=room_id
             )
-            return complexity
         except CodeMessageException as e:
             # We didn't manage to get it -- probably a 404. We are okay if other
             # servers don't give it to us.
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index e5339aca23..171d25c945 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -49,7 +49,6 @@ from synapse.events import EventBase
 from synapse.federation.federation_base import FederationBase, event_from_pdu_json
 from synapse.federation.persistence import TransactionActions
 from synapse.federation.units import Edu, Transaction
-from synapse.http.endpoint import parse_server_name
 from synapse.http.servlet import assert_params_in_dict
 from synapse.logging.context import (
     make_deferred_yieldable,
@@ -66,6 +65,7 @@ from synapse.types import JsonDict, get_domain_from_id
 from synapse.util import glob_to_regex, json_decoder, unwrapFirstError
 from synapse.util.async_helpers import Linearizer, concurrently_execute
 from synapse.util.caches.response_cache import ResponseCache
+from synapse.util.stringutils import parse_server_name
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
diff --git a/synapse/federation/sender/__init__.py b/synapse/federation/sender/__init__.py
index 604cfd1935..643b26ae6d 100644
--- a/synapse/federation/sender/__init__.py
+++ b/synapse/federation/sender/__init__.py
@@ -142,6 +142,8 @@ class FederationSender:
             self._wake_destinations_needing_catchup,
         )
 
+        self._external_cache = hs.get_external_cache()
+
     def _get_per_destination_queue(self, destination: str) -> PerDestinationQueue:
         """Get or create a PerDestinationQueue for the given destination
 
@@ -197,22 +199,40 @@ class FederationSender:
                     if not event.internal_metadata.should_proactively_send():
                         return
 
-                    try:
-                        # Get the state from before the event.
-                        # We need to make sure that this is the state from before
-                        # the event and not from after it.
-                        # Otherwise if the last member on a server in a room is
-                        # banned then it won't receive the event because it won't
-                        # be in the room after the ban.
-                        destinations = await self.state.get_hosts_in_room_at_events(
-                            event.room_id, event_ids=event.prev_event_ids()
-                        )
-                    except Exception:
-                        logger.exception(
-                            "Failed to calculate hosts in room for event: %s",
-                            event.event_id,
+                    destinations = None  # type: Optional[Set[str]]
+                    if not event.prev_event_ids():
+                        # If there are no prev event IDs then the state is empty
+                        # and so no remote servers in the room
+                        destinations = set()
+                    else:
+                        # We check the external cache for the destinations, which is
+                        # stored per state group.
+
+                        sg = await self._external_cache.get(
+                            "event_to_prev_state_group", event.event_id
                         )
-                        return
+                        if sg:
+                            destinations = await self._external_cache.get(
+                                "get_joined_hosts", str(sg)
+                            )
+
+                    if destinations is None:
+                        try:
+                            # Get the state from before the event.
+                            # We need to make sure that this is the state from before
+                            # the event and not from after it.
+                            # Otherwise if the last member on a server in a room is
+                            # banned then it won't receive the event because it won't
+                            # be in the room after the ban.
+                            destinations = await self.state.get_hosts_in_room_at_events(
+                                event.room_id, event_ids=event.prev_event_ids()
+                            )
+                        except Exception:
+                            logger.exception(
+                                "Failed to calculate hosts in room for event: %s",
+                                event.event_id,
+                            )
+                            return
 
                     destinations = {
                         d
diff --git a/synapse/federation/transport/server.py b/synapse/federation/transport/server.py
index cfd094e58f..95c64510a9 100644
--- a/synapse/federation/transport/server.py
+++ b/synapse/federation/transport/server.py
@@ -28,7 +28,6 @@ from synapse.api.urls import (
     FEDERATION_V1_PREFIX,
     FEDERATION_V2_PREFIX,
 )
-from synapse.http.endpoint import parse_and_validate_server_name
 from synapse.http.server import JsonResource
 from synapse.http.servlet import (
     parse_boolean_from_args,
@@ -45,6 +44,7 @@ from synapse.logging.opentracing import (
 )
 from synapse.server import HomeServer
 from synapse.types import ThirdPartyInstanceID, get_domain_from_id
+from synapse.util.stringutils import parse_and_validate_server_name
 from synapse.util.versionstring import get_version_string
 
 logger = logging.getLogger(__name__)
diff --git a/synapse/handlers/acme.py b/synapse/handlers/acme.py
index 8476256a59..5ecb2da1ac 100644
--- a/synapse/handlers/acme.py
+++ b/synapse/handlers/acme.py
@@ -14,6 +14,7 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING
 
 import twisted
 import twisted.internet.error
@@ -22,6 +23,9 @@ from twisted.web.resource import Resource
 
 from synapse.app import check_bind_error
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
 ACME_REGISTER_FAIL_ERROR = """
@@ -35,12 +39,12 @@ solutions, please read https://github.com/matrix-org/synapse/blob/master/docs/AC
 
 
 class AcmeHandler:
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.reactor = hs.get_reactor()
         self._acme_domain = hs.config.acme_domain
 
-    async def start_listening(self):
+    async def start_listening(self) -> None:
         from synapse.handlers import acme_issuing_service
 
         # Configure logging for txacme, if you need to debug
@@ -85,7 +89,7 @@ class AcmeHandler:
             logger.error(ACME_REGISTER_FAIL_ERROR)
             raise
 
-    async def provision_certificate(self):
+    async def provision_certificate(self) -> None:
 
         logger.warning("Reprovisioning %s", self._acme_domain)
 
@@ -110,5 +114,3 @@ class AcmeHandler:
         except Exception:
             logger.exception("Failed saving!")
             raise
-
-        return True
diff --git a/synapse/handlers/acme_issuing_service.py b/synapse/handlers/acme_issuing_service.py
index 7294649d71..ae2a9dd9c2 100644
--- a/synapse/handlers/acme_issuing_service.py
+++ b/synapse/handlers/acme_issuing_service.py
@@ -22,8 +22,10 @@ only need (and may only have available) if we are doing ACME, so is designed to
 imported conditionally.
 """
 import logging
+from typing import Dict, Iterable, List
 
 import attr
+import pem
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives import serialization
 from josepy import JWKRSA
@@ -36,20 +38,27 @@ from txacme.util import generate_private_key
 from zope.interface import implementer
 
 from twisted.internet import defer
+from twisted.internet.interfaces import IReactorTCP
 from twisted.python.filepath import FilePath
 from twisted.python.url import URL
+from twisted.web.resource import IResource
 
 logger = logging.getLogger(__name__)
 
 
-def create_issuing_service(reactor, acme_url, account_key_file, well_known_resource):
+def create_issuing_service(
+    reactor: IReactorTCP,
+    acme_url: str,
+    account_key_file: str,
+    well_known_resource: IResource,
+) -> AcmeIssuingService:
     """Create an ACME issuing service, and attach it to a web Resource
 
     Args:
         reactor: twisted reactor
-        acme_url (str): URL to use to request certificates
-        account_key_file (str): where to store the account key
-        well_known_resource (twisted.web.IResource): web resource for .well-known.
+        acme_url: URL to use to request certificates
+        account_key_file: where to store the account key
+        well_known_resource: web resource for .well-known.
             we will attach a child resource for "acme-challenge".
 
     Returns:
@@ -83,18 +92,20 @@ class ErsatzStore:
     A store that only stores in memory.
     """
 
-    certs = attr.ib(default=attr.Factory(dict))
+    certs = attr.ib(type=Dict[bytes, List[bytes]], default=attr.Factory(dict))
 
-    def store(self, server_name, pem_objects):
+    def store(
+        self, server_name: bytes, pem_objects: Iterable[pem.AbstractPEMObject]
+    ) -> defer.Deferred:
         self.certs[server_name] = [o.as_bytes() for o in pem_objects]
         return defer.succeed(None)
 
 
-def load_or_create_client_key(key_file):
+def load_or_create_client_key(key_file: str) -> JWKRSA:
     """Load the ACME account key from a file, creating it if it does not exist.
 
     Args:
-        key_file (str): name of the file to use as the account key
+        key_file: name of the file to use as the account key
     """
     # this is based on txacme.endpoint.load_or_create_client_key, but doesn't
     # hardcode the 'client.key' filename
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 0e98db22b3..a19c556437 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -61,6 +61,7 @@ from synapse.http.site import SynapseRequest
 from synapse.logging.context import defer_to_thread
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.module_api import ModuleApi
+from synapse.storage.roommember import ProfileInfo
 from synapse.types import JsonDict, Requester, UserID
 from synapse.util import stringutils as stringutils
 from synapse.util.async_helpers import maybe_awaitable
@@ -567,16 +568,6 @@ class AuthHandler(BaseHandler):
                         session.session_id, login_type, result
                     )
             except LoginError as e:
-                if login_type == LoginType.EMAIL_IDENTITY:
-                    # riot used to have a bug where it would request a new
-                    # validation token (thus sending a new email) each time it
-                    # got a 401 with a 'flows' field.
-                    # (https://github.com/vector-im/vector-web/issues/2447).
-                    #
-                    # Grandfather in the old behaviour for now to avoid
-                    # breaking old riot deployments.
-                    raise
-
                 # this step failed. Merge the error dict into the response
                 # so that the client can have another go.
                 errordict = e.error_dict()
@@ -1387,7 +1378,9 @@ class AuthHandler(BaseHandler):
         )
 
         return self._sso_auth_confirm_template.render(
-            description=session.description, redirect_url=redirect_url,
+            description=session.description,
+            redirect_url=redirect_url,
+            idp=sso_auth_provider,
         )
 
     async def complete_sso_login(
@@ -1396,6 +1389,7 @@ class AuthHandler(BaseHandler):
         request: Request,
         client_redirect_url: str,
         extra_attributes: Optional[JsonDict] = None,
+        new_user: bool = False,
     ):
         """Having figured out a mxid for this user, complete the HTTP request
 
@@ -1406,6 +1400,8 @@ class AuthHandler(BaseHandler):
                 process.
             extra_attributes: Extra attributes which will be passed to the client
                 during successful login. Must be JSON serializable.
+            new_user: True if we should use wording appropriate to a user who has just
+                registered.
         """
         # If the account has been deactivated, do not proceed with the login
         # flow.
@@ -1414,8 +1410,17 @@ class AuthHandler(BaseHandler):
             respond_with_html(request, 403, self._sso_account_deactivated_template)
             return
 
+        profile = await self.store.get_profileinfo(
+            UserID.from_string(registered_user_id).localpart
+        )
+
         self._complete_sso_login(
-            registered_user_id, request, client_redirect_url, extra_attributes
+            registered_user_id,
+            request,
+            client_redirect_url,
+            extra_attributes,
+            new_user=new_user,
+            user_profile_data=profile,
         )
 
     def _complete_sso_login(
@@ -1424,12 +1429,18 @@ class AuthHandler(BaseHandler):
         request: Request,
         client_redirect_url: str,
         extra_attributes: Optional[JsonDict] = None,
+        new_user: bool = False,
+        user_profile_data: Optional[ProfileInfo] = None,
     ):
         """
         The synchronous portion of complete_sso_login.
 
         This exists purely for backwards compatibility of synapse.module_api.ModuleApi.
         """
+
+        if user_profile_data is None:
+            user_profile_data = ProfileInfo(None, None)
+
         # Store any extra attributes which will be passed in the login response.
         # Note that this is per-user so it may overwrite a previous value, this
         # is considered OK since the newest SSO attributes should be most valid.
@@ -1467,6 +1478,9 @@ class AuthHandler(BaseHandler):
             display_url=redirect_url_no_params,
             redirect_url=redirect_url,
             server_name=self._server_name,
+            new_user=new_user,
+            user_id=registered_user_id,
+            user_profile=user_profile_data,
         )
         respond_with_html(request, 200, html)
 
diff --git a/synapse/handlers/cas_handler.py b/synapse/handlers/cas_handler.py
index f3430c6713..bd35d1fb87 100644
--- a/synapse/handlers/cas_handler.py
+++ b/synapse/handlers/cas_handler.py
@@ -80,6 +80,11 @@ class CasHandler:
         # user-facing name of this auth provider
         self.idp_name = "CAS"
 
+        # we do not currently support brands/icons for CAS auth, but this is required by
+        # the SsoIdentityProvider protocol type.
+        self.idp_icon = None
+        self.idp_brand = None
+
         self._sso_handler = hs.get_sso_handler()
 
         self._sso_handler.register_identity_provider(self)
@@ -95,11 +100,7 @@ class CasHandler:
         Returns:
             The URL to use as a "service" parameter.
         """
-        return "%s%s?%s" % (
-            self._cas_service_url,
-            "/_matrix/client/r0/login/cas/ticket",
-            urllib.parse.urlencode(args),
-        )
+        return "%s?%s" % (self._cas_service_url, urllib.parse.urlencode(args),)
 
     async def _validate_ticket(
         self, ticket: str, service_args: Dict[str, str]
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index debb1b4f29..0863154f7a 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -15,7 +15,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import TYPE_CHECKING, Any, Dict, Iterable, List, Optional, Set, Tuple
+from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Set, Tuple
 
 from synapse.api import errors
 from synapse.api.constants import EventTypes
@@ -62,7 +62,7 @@ class DeviceWorkerHandler(BaseHandler):
         self._auth_handler = hs.get_auth_handler()
 
     @trace
-    async def get_devices_by_user(self, user_id: str) -> List[Dict[str, Any]]:
+    async def get_devices_by_user(self, user_id: str) -> List[JsonDict]:
         """
         Retrieve the given user's devices
 
@@ -85,7 +85,7 @@ class DeviceWorkerHandler(BaseHandler):
         return devices
 
     @trace
-    async def get_device(self, user_id: str, device_id: str) -> Dict[str, Any]:
+    async def get_device(self, user_id: str, device_id: str) -> JsonDict:
         """ Retrieve the given device
 
         Args:
@@ -598,7 +598,7 @@ class DeviceHandler(DeviceWorkerHandler):
 
 
 def _update_device_from_client_ips(
-    device: Dict[str, Any], client_ips: Dict[Tuple[str, str], Dict[str, Any]]
+    device: JsonDict, client_ips: Dict[Tuple[str, str], JsonDict]
 ) -> None:
     ip = client_ips.get((device["user_id"], device["device_id"]), {})
     device.update({"last_seen_ts": ip.get("last_seen"), "last_seen_ip": ip.get("ip")})
@@ -946,8 +946,8 @@ class DeviceListUpdater:
     async def process_cross_signing_key_update(
         self,
         user_id: str,
-        master_key: Optional[Dict[str, Any]],
-        self_signing_key: Optional[Dict[str, Any]],
+        master_key: Optional[JsonDict],
+        self_signing_key: Optional[JsonDict],
     ) -> List[str]:
         """Process the given new master and self-signing key for the given remote user.
 
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 929752150d..8f3a6b35a4 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -16,7 +16,7 @@
 # limitations under the License.
 
 import logging
-from typing import Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Tuple
 
 import attr
 from canonicaljson import encode_canonical_json
@@ -31,6 +31,7 @@ from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.logging.opentracing import log_kv, set_tag, tag_args, trace
 from synapse.replication.http.devices import ReplicationUserDevicesResyncRestServlet
 from synapse.types import (
+    JsonDict,
     UserID,
     get_domain_from_id,
     get_verify_key_from_cross_signing_key,
@@ -40,11 +41,14 @@ from synapse.util.async_helpers import Linearizer
 from synapse.util.caches.expiringcache import ExpiringCache
 from synapse.util.retryutils import NotRetryingDestination
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 class E2eKeysHandler:
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.store = hs.get_datastore()
         self.federation = hs.get_federation_client()
         self.device_handler = hs.get_device_handler()
@@ -78,7 +82,9 @@ class E2eKeysHandler:
         )
 
     @trace
-    async def query_devices(self, query_body, timeout, from_user_id):
+    async def query_devices(
+        self, query_body: JsonDict, timeout: int, from_user_id: str
+    ) -> JsonDict:
         """ Handle a device key query from a client
 
         {
@@ -98,12 +104,14 @@ class E2eKeysHandler:
         }
 
         Args:
-            from_user_id (str): the user making the query.  This is used when
+            from_user_id: the user making the query.  This is used when
                 adding cross-signing signatures to limit what signatures users
                 can see.
         """
 
-        device_keys_query = query_body.get("device_keys", {})
+        device_keys_query = query_body.get(
+            "device_keys", {}
+        )  # type: Dict[str, Iterable[str]]
 
         # separate users by domain.
         # make a map from domain to user_id to device_ids
@@ -121,7 +129,8 @@ class E2eKeysHandler:
         set_tag("remote_key_query", remote_queries)
 
         # First get local devices.
-        failures = {}
+        # A map of destination -> failure response.
+        failures = {}  # type: Dict[str, JsonDict]
         results = {}
         if local_query:
             local_result = await self.query_local_devices(local_query)
@@ -135,9 +144,10 @@ class E2eKeysHandler:
         )
 
         # Now attempt to get any remote devices from our local cache.
-        remote_queries_not_in_cache = {}
+        # A map of destination -> user ID -> device IDs.
+        remote_queries_not_in_cache = {}  # type: Dict[str, Dict[str, Iterable[str]]]
         if remote_queries:
-            query_list = []
+            query_list = []  # type: List[Tuple[str, Optional[str]]]
             for user_id, device_ids in remote_queries.items():
                 if device_ids:
                     query_list.extend((user_id, device_id) for device_id in device_ids)
@@ -284,15 +294,15 @@ class E2eKeysHandler:
         return ret
 
     async def get_cross_signing_keys_from_cache(
-        self, query, from_user_id
+        self, query: Iterable[str], from_user_id: Optional[str]
     ) -> Dict[str, Dict[str, dict]]:
         """Get cross-signing keys for users from the database
 
         Args:
-            query (Iterable[string]) an iterable of user IDs.  A dict whose keys
+            query: an iterable of user IDs.  A dict whose keys
                 are user IDs satisfies this, so the query format used for
                 query_devices can be used here.
-            from_user_id (str): the user making the query.  This is used when
+            from_user_id: the user making the query.  This is used when
                 adding cross-signing signatures to limit what signatures users
                 can see.
 
@@ -315,14 +325,12 @@ class E2eKeysHandler:
             if "self_signing" in user_info:
                 self_signing_keys[user_id] = user_info["self_signing"]
 
-        if (
-            from_user_id in keys
-            and keys[from_user_id] is not None
-            and "user_signing" in keys[from_user_id]
-        ):
-            # users can see other users' master and self-signing keys, but can
-            # only see their own user-signing keys
-            user_signing_keys[from_user_id] = keys[from_user_id]["user_signing"]
+        # users can see other users' master and self-signing keys, but can
+        # only see their own user-signing keys
+        if from_user_id:
+            from_user_key = keys.get(from_user_id)
+            if from_user_key and "user_signing" in from_user_key:
+                user_signing_keys[from_user_id] = from_user_key["user_signing"]
 
         return {
             "master_keys": master_keys,
@@ -344,9 +352,9 @@ class E2eKeysHandler:
             A map from user_id -> device_id -> device details
         """
         set_tag("local_query", query)
-        local_query = []
+        local_query = []  # type: List[Tuple[str, Optional[str]]]
 
-        result_dict = {}
+        result_dict = {}  # type: Dict[str, Dict[str, dict]]
         for user_id, device_ids in query.items():
             # we use UserID.from_string to catch invalid user ids
             if not self.is_mine(UserID.from_string(user_id)):
@@ -380,10 +388,14 @@ class E2eKeysHandler:
         log_kv(results)
         return result_dict
 
-    async def on_federation_query_client_keys(self, query_body):
+    async def on_federation_query_client_keys(
+        self, query_body: Dict[str, Dict[str, Optional[List[str]]]]
+    ) -> JsonDict:
         """ Handle a device key query from a federated server
         """
-        device_keys_query = query_body.get("device_keys", {})
+        device_keys_query = query_body.get(
+            "device_keys", {}
+        )  # type: Dict[str, Optional[List[str]]]
         res = await self.query_local_devices(device_keys_query)
         ret = {"device_keys": res}
 
@@ -397,31 +409,34 @@ class E2eKeysHandler:
         return ret
 
     @trace
-    async def claim_one_time_keys(self, query, timeout):
-        local_query = []
-        remote_queries = {}
+    async def claim_one_time_keys(
+        self, query: Dict[str, Dict[str, Dict[str, str]]], timeout: int
+    ) -> JsonDict:
+        local_query = []  # type: List[Tuple[str, str, str]]
+        remote_queries = {}  # type: Dict[str, Dict[str, Dict[str, str]]]
 
-        for user_id, device_keys in query.get("one_time_keys", {}).items():
+        for user_id, one_time_keys in query.get("one_time_keys", {}).items():
             # we use UserID.from_string to catch invalid user ids
             if self.is_mine(UserID.from_string(user_id)):
-                for device_id, algorithm in device_keys.items():
+                for device_id, algorithm in one_time_keys.items():
                     local_query.append((user_id, device_id, algorithm))
             else:
                 domain = get_domain_from_id(user_id)
-                remote_queries.setdefault(domain, {})[user_id] = device_keys
+                remote_queries.setdefault(domain, {})[user_id] = one_time_keys
 
         set_tag("local_key_query", local_query)
         set_tag("remote_key_query", remote_queries)
 
         results = await self.store.claim_e2e_one_time_keys(local_query)
 
-        json_result = {}
-        failures = {}
+        # A map of user ID -> device ID -> key ID -> key.
+        json_result = {}  # type: Dict[str, Dict[str, Dict[str, JsonDict]]]
+        failures = {}  # type: Dict[str, JsonDict]
         for user_id, device_keys in results.items():
             for device_id, keys in device_keys.items():
-                for key_id, json_bytes in keys.items():
+                for key_id, json_str in keys.items():
                     json_result.setdefault(user_id, {})[device_id] = {
-                        key_id: json_decoder.decode(json_bytes)
+                        key_id: json_decoder.decode(json_str)
                     }
 
         @trace
@@ -468,7 +483,9 @@ class E2eKeysHandler:
         return {"one_time_keys": json_result, "failures": failures}
 
     @tag_args
-    async def upload_keys_for_user(self, user_id, device_id, keys):
+    async def upload_keys_for_user(
+        self, user_id: str, device_id: str, keys: JsonDict
+    ) -> JsonDict:
 
         time_now = self.clock.time_msec()
 
@@ -543,8 +560,8 @@ class E2eKeysHandler:
         return {"one_time_key_counts": result}
 
     async def _upload_one_time_keys_for_user(
-        self, user_id, device_id, time_now, one_time_keys
-    ):
+        self, user_id: str, device_id: str, time_now: int, one_time_keys: JsonDict
+    ) -> None:
         logger.info(
             "Adding one_time_keys %r for device %r for user %r at %d",
             one_time_keys.keys(),
@@ -585,12 +602,14 @@ class E2eKeysHandler:
         log_kv({"message": "Inserting new one_time_keys.", "keys": new_keys})
         await self.store.add_e2e_one_time_keys(user_id, device_id, time_now, new_keys)
 
-    async def upload_signing_keys_for_user(self, user_id, keys):
+    async def upload_signing_keys_for_user(
+        self, user_id: str, keys: JsonDict
+    ) -> JsonDict:
         """Upload signing keys for cross-signing
 
         Args:
-            user_id (string): the user uploading the keys
-            keys (dict[string, dict]): the signing keys
+            user_id: the user uploading the keys
+            keys: the signing keys
         """
 
         # if a master key is uploaded, then check it.  Otherwise, load the
@@ -667,16 +686,17 @@ class E2eKeysHandler:
 
         return {}
 
-    async def upload_signatures_for_device_keys(self, user_id, signatures):
+    async def upload_signatures_for_device_keys(
+        self, user_id: str, signatures: JsonDict
+    ) -> JsonDict:
         """Upload device signatures for cross-signing
 
         Args:
-            user_id (string): the user uploading the signatures
-            signatures (dict[string, dict[string, dict]]): map of users to
-                devices to signed keys. This is the submission from the user; an
-                exception will be raised if it is malformed.
+            user_id: the user uploading the signatures
+            signatures: map of users to devices to signed keys. This is the submission
+            from the user; an exception will be raised if it is malformed.
         Returns:
-            dict: response to be sent back to the client.  The response will have
+            The response to be sent back to the client.  The response will have
                 a "failures" key, which will be a dict mapping users to devices
                 to errors for the signatures that failed.
         Raises:
@@ -719,7 +739,9 @@ class E2eKeysHandler:
 
         return {"failures": failures}
 
-    async def _process_self_signatures(self, user_id, signatures):
+    async def _process_self_signatures(
+        self, user_id: str, signatures: JsonDict
+    ) -> Tuple[List["SignatureListItem"], Dict[str, Dict[str, dict]]]:
         """Process uploaded signatures of the user's own keys.
 
         Signatures of the user's own keys from this API come in two forms:
@@ -731,15 +753,14 @@ class E2eKeysHandler:
             signatures (dict[string, dict]): map of devices to signed keys
 
         Returns:
-            (list[SignatureListItem], dict[string, dict[string, dict]]):
-            a list of signatures to store, and a map of users to devices to failure
-            reasons
+            A tuple of a list of signatures to store, and a map of users to
+            devices to failure reasons
 
         Raises:
             SynapseError: if the input is malformed
         """
-        signature_list = []
-        failures = {}
+        signature_list = []  # type: List[SignatureListItem]
+        failures = {}  # type: Dict[str, Dict[str, JsonDict]]
         if not signatures:
             return signature_list, failures
 
@@ -834,19 +855,24 @@ class E2eKeysHandler:
         return signature_list, failures
 
     def _check_master_key_signature(
-        self, user_id, master_key_id, signed_master_key, stored_master_key, devices
-    ):
+        self,
+        user_id: str,
+        master_key_id: str,
+        signed_master_key: JsonDict,
+        stored_master_key: JsonDict,
+        devices: Dict[str, Dict[str, JsonDict]],
+    ) -> List["SignatureListItem"]:
         """Check signatures of a user's master key made by their devices.
 
         Args:
-            user_id (string): the user whose master key is being checked
-            master_key_id (string): the ID of the user's master key
-            signed_master_key (dict): the user's signed master key that was uploaded
-            stored_master_key (dict): our previously-stored copy of the user's master key
-            devices (iterable(dict)): the user's devices
+            user_id: the user whose master key is being checked
+            master_key_id: the ID of the user's master key
+            signed_master_key: the user's signed master key that was uploaded
+            stored_master_key: our previously-stored copy of the user's master key
+            devices: the user's devices
 
         Returns:
-            list[SignatureListItem]: a list of signatures to store
+            A list of signatures to store
 
         Raises:
             SynapseError: if a signature is invalid
@@ -877,25 +903,26 @@ class E2eKeysHandler:
 
         return master_key_signature_list
 
-    async def _process_other_signatures(self, user_id, signatures):
+    async def _process_other_signatures(
+        self, user_id: str, signatures: Dict[str, dict]
+    ) -> Tuple[List["SignatureListItem"], Dict[str, Dict[str, dict]]]:
         """Process uploaded signatures of other users' keys.  These will be the
         target user's master keys, signed by the uploading user's user-signing
         key.
 
         Args:
-            user_id (string): the user uploading the keys
-            signatures (dict[string, dict]): map of users to devices to signed keys
+            user_id: the user uploading the keys
+            signatures: map of users to devices to signed keys
 
         Returns:
-            (list[SignatureListItem], dict[string, dict[string, dict]]):
-            a list of signatures to store, and a map of users to devices to failure
+            A list of signatures to store, and a map of users to devices to failure
             reasons
 
         Raises:
             SynapseError: if the input is malformed
         """
-        signature_list = []
-        failures = {}
+        signature_list = []  # type: List[SignatureListItem]
+        failures = {}  # type: Dict[str, Dict[str, JsonDict]]
         if not signatures:
             return signature_list, failures
 
@@ -983,7 +1010,7 @@ class E2eKeysHandler:
 
     async def _get_e2e_cross_signing_verify_key(
         self, user_id: str, key_type: str, from_user_id: str = None
-    ):
+    ) -> Tuple[JsonDict, str, VerifyKey]:
         """Fetch locally or remotely query for a cross-signing public key.
 
         First, attempt to fetch the cross-signing public key from storage.
@@ -997,8 +1024,7 @@ class E2eKeysHandler:
                 This affects what signatures are fetched.
 
         Returns:
-            dict, str, VerifyKey: the raw key data, the key ID, and the
-                signedjson verify key
+            The raw key data, the key ID, and the signedjson verify key
 
         Raises:
             NotFoundError: if the key is not found
@@ -1135,16 +1161,18 @@ class E2eKeysHandler:
         return desired_key, desired_key_id, desired_verify_key
 
 
-def _check_cross_signing_key(key, user_id, key_type, signing_key=None):
+def _check_cross_signing_key(
+    key: JsonDict, user_id: str, key_type: str, signing_key: Optional[VerifyKey] = None
+) -> None:
     """Check a cross-signing key uploaded by a user.  Performs some basic sanity
     checking, and ensures that it is signed, if a signature is required.
 
     Args:
-        key (dict): the key data to verify
-        user_id (str): the user whose key is being checked
-        key_type (str): the type of key that the key should be
-        signing_key (VerifyKey): (optional) the signing key that the key should
-            be signed with.  If omitted, signatures will not be checked.
+        key: the key data to verify
+        user_id: the user whose key is being checked
+        key_type: the type of key that the key should be
+        signing_key: the signing key that the key should be signed with.  If
+            omitted, signatures will not be checked.
     """
     if (
         key.get("user_id") != user_id
@@ -1162,16 +1190,21 @@ def _check_cross_signing_key(key, user_id, key_type, signing_key=None):
             )
 
 
-def _check_device_signature(user_id, verify_key, signed_device, stored_device):
+def _check_device_signature(
+    user_id: str,
+    verify_key: VerifyKey,
+    signed_device: JsonDict,
+    stored_device: JsonDict,
+) -> None:
     """Check that a signature on a device or cross-signing key is correct and
     matches the copy of the device/key that we have stored.  Throws an
     exception if an error is detected.
 
     Args:
-        user_id (str): the user ID whose signature is being checked
-        verify_key (VerifyKey): the key to verify the device with
-        signed_device (dict): the uploaded signed device data
-        stored_device (dict): our previously stored copy of the device
+        user_id: the user ID whose signature is being checked
+        verify_key: the key to verify the device with
+        signed_device: the uploaded signed device data
+        stored_device: our previously stored copy of the device
 
     Raises:
         SynapseError: if the signature was invalid or the sent device is not the
@@ -1201,7 +1234,7 @@ def _check_device_signature(user_id, verify_key, signed_device, stored_device):
         raise SynapseError(400, "Invalid signature", Codes.INVALID_SIGNATURE)
 
 
-def _exception_to_failure(e):
+def _exception_to_failure(e: Exception) -> JsonDict:
     if isinstance(e, SynapseError):
         return {"status": e.code, "errcode": e.errcode, "message": str(e)}
 
@@ -1218,7 +1251,7 @@ def _exception_to_failure(e):
     return {"status": 503, "message": str(e)}
 
 
-def _one_time_keys_match(old_key_json, new_key):
+def _one_time_keys_match(old_key_json: str, new_key: JsonDict) -> bool:
     old_key = json_decoder.decode(old_key_json)
 
     # if either is a string rather than an object, they must match exactly
@@ -1239,16 +1272,16 @@ class SignatureListItem:
     """An item in the signature list as used by upload_signatures_for_device_keys.
     """
 
-    signing_key_id = attr.ib()
-    target_user_id = attr.ib()
-    target_device_id = attr.ib()
-    signature = attr.ib()
+    signing_key_id = attr.ib(type=str)
+    target_user_id = attr.ib(type=str)
+    target_device_id = attr.ib(type=str)
+    signature = attr.ib(type=JsonDict)
 
 
 class SigningKeyEduUpdater:
     """Handles incoming signing key updates from federation and updates the DB"""
 
-    def __init__(self, hs, e2e_keys_handler):
+    def __init__(self, hs: "HomeServer", e2e_keys_handler: E2eKeysHandler):
         self.store = hs.get_datastore()
         self.federation = hs.get_federation_client()
         self.clock = hs.get_clock()
@@ -1257,7 +1290,7 @@ class SigningKeyEduUpdater:
         self._remote_edu_linearizer = Linearizer(name="remote_signing_key")
 
         # user_id -> list of updates waiting to be handled.
-        self._pending_updates = {}
+        self._pending_updates = {}  # type: Dict[str, List[Tuple[JsonDict, JsonDict]]]
 
         # Recently seen stream ids. We don't bother keeping these in the DB,
         # but they're useful to have them about to reduce the number of spurious
@@ -1270,13 +1303,15 @@ class SigningKeyEduUpdater:
             iterable=True,
         )
 
-    async def incoming_signing_key_update(self, origin, edu_content):
+    async def incoming_signing_key_update(
+        self, origin: str, edu_content: JsonDict
+    ) -> None:
         """Called on incoming signing key update from federation. Responsible for
         parsing the EDU and adding to pending updates list.
 
         Args:
-            origin (string): the server that sent the EDU
-            edu_content (dict): the contents of the EDU
+            origin: the server that sent the EDU
+            edu_content: the contents of the EDU
         """
 
         user_id = edu_content.pop("user_id")
@@ -1299,11 +1334,11 @@ class SigningKeyEduUpdater:
 
         await self._handle_signing_key_updates(user_id)
 
-    async def _handle_signing_key_updates(self, user_id):
+    async def _handle_signing_key_updates(self, user_id: str) -> None:
         """Actually handle pending updates.
 
         Args:
-            user_id (string): the user whose updates we are processing
+            user_id: the user whose updates we are processing
         """
 
         device_handler = self.e2e_keys_handler.device_handler
@@ -1315,7 +1350,7 @@ class SigningKeyEduUpdater:
                 # This can happen since we batch updates
                 return
 
-            device_ids = []
+            device_ids = []  # type: List[str]
 
             logger.info("pending updates: %r", pending_updates)
 
diff --git a/synapse/handlers/e2e_room_keys.py b/synapse/handlers/e2e_room_keys.py
index f01b090772..622cae23be 100644
--- a/synapse/handlers/e2e_room_keys.py
+++ b/synapse/handlers/e2e_room_keys.py
@@ -15,6 +15,7 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING, List, Optional
 
 from synapse.api.errors import (
     Codes,
@@ -24,8 +25,12 @@ from synapse.api.errors import (
     SynapseError,
 )
 from synapse.logging.opentracing import log_kv, trace
+from synapse.types import JsonDict
 from synapse.util.async_helpers import Linearizer
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -37,7 +42,7 @@ class E2eRoomKeysHandler:
     The actual payload of the encrypted keys is completely opaque to the handler.
     """
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.store = hs.get_datastore()
 
         # Used to lock whenever a client is uploading key data.  This prevents collisions
@@ -48,21 +53,27 @@ class E2eRoomKeysHandler:
         self._upload_linearizer = Linearizer("upload_room_keys_lock")
 
     @trace
-    async def get_room_keys(self, user_id, version, room_id=None, session_id=None):
+    async def get_room_keys(
+        self,
+        user_id: str,
+        version: str,
+        room_id: Optional[str] = None,
+        session_id: Optional[str] = None,
+    ) -> List[JsonDict]:
         """Bulk get the E2E room keys for a given backup, optionally filtered to a given
         room, or a given session.
         See EndToEndRoomKeyStore.get_e2e_room_keys for full details.
 
         Args:
-            user_id(str): the user whose keys we're getting
-            version(str): the version ID of the backup we're getting keys from
-            room_id(string): room ID to get keys for, for None to get keys for all rooms
-            session_id(string): session ID to get keys for, for None to get keys for all
+            user_id: the user whose keys we're getting
+            version: the version ID of the backup we're getting keys from
+            room_id: room ID to get keys for, for None to get keys for all rooms
+            session_id: session ID to get keys for, for None to get keys for all
                 sessions
         Raises:
             NotFoundError: if the backup version does not exist
         Returns:
-            A deferred list of dicts giving the session_data and message metadata for
+            A list of dicts giving the session_data and message metadata for
             these room keys.
         """
 
@@ -86,17 +97,23 @@ class E2eRoomKeysHandler:
             return results
 
     @trace
-    async def delete_room_keys(self, user_id, version, room_id=None, session_id=None):
+    async def delete_room_keys(
+        self,
+        user_id: str,
+        version: str,
+        room_id: Optional[str] = None,
+        session_id: Optional[str] = None,
+    ) -> JsonDict:
         """Bulk delete the E2E room keys for a given backup, optionally filtered to a given
         room or a given session.
         See EndToEndRoomKeyStore.delete_e2e_room_keys for full details.
 
         Args:
-            user_id(str): the user whose backup we're deleting
-            version(str): the version ID of the backup we're deleting
-            room_id(string): room ID to delete keys for, for None to delete keys for all
+            user_id: the user whose backup we're deleting
+            version: the version ID of the backup we're deleting
+            room_id: room ID to delete keys for, for None to delete keys for all
                 rooms
-            session_id(string): session ID to delete keys for, for None to delete keys
+            session_id: session ID to delete keys for, for None to delete keys
                 for all sessions
         Raises:
             NotFoundError: if the backup version does not exist
@@ -128,15 +145,17 @@ class E2eRoomKeysHandler:
             return {"etag": str(version_etag), "count": count}
 
     @trace
-    async def upload_room_keys(self, user_id, version, room_keys):
+    async def upload_room_keys(
+        self, user_id: str, version: str, room_keys: JsonDict
+    ) -> JsonDict:
         """Bulk upload a list of room keys into a given backup version, asserting
         that the given version is the current backup version.  room_keys are merged
         into the current backup as described in RoomKeysServlet.on_PUT().
 
         Args:
-            user_id(str): the user whose backup we're setting
-            version(str): the version ID of the backup we're updating
-            room_keys(dict): a nested dict describing the room_keys we're setting:
+            user_id: the user whose backup we're setting
+            version: the version ID of the backup we're updating
+            room_keys: a nested dict describing the room_keys we're setting:
 
         {
             "rooms": {
@@ -254,14 +273,16 @@ class E2eRoomKeysHandler:
             return {"etag": str(version_etag), "count": count}
 
     @staticmethod
-    def _should_replace_room_key(current_room_key, room_key):
+    def _should_replace_room_key(
+        current_room_key: Optional[JsonDict], room_key: JsonDict
+    ) -> bool:
         """
         Determine whether to replace a given current_room_key (if any)
         with a newly uploaded room_key backup
 
         Args:
-            current_room_key (dict): Optional, the current room_key dict if any
-            room_key (dict): The new room_key dict which may or may not be fit to
+            current_room_key: Optional, the current room_key dict if any
+            room_key : The new room_key dict which may or may not be fit to
                 replace the current_room_key
 
         Returns:
@@ -286,14 +307,14 @@ class E2eRoomKeysHandler:
         return True
 
     @trace
-    async def create_version(self, user_id, version_info):
+    async def create_version(self, user_id: str, version_info: JsonDict) -> str:
         """Create a new backup version.  This automatically becomes the new
         backup version for the user's keys; previous backups will no longer be
         writeable to.
 
         Args:
-            user_id(str): the user whose backup version we're creating
-            version_info(dict): metadata about the new version being created
+            user_id: the user whose backup version we're creating
+            version_info: metadata about the new version being created
 
         {
             "algorithm": "m.megolm_backup.v1",
@@ -301,7 +322,7 @@ class E2eRoomKeysHandler:
         }
 
         Returns:
-            A deferred of a string that gives the new version number.
+            The new version number.
         """
 
         # TODO: Validate the JSON to make sure it has the right keys.
@@ -313,17 +334,19 @@ class E2eRoomKeysHandler:
             )
             return new_version
 
-    async def get_version_info(self, user_id, version=None):
+    async def get_version_info(
+        self, user_id: str, version: Optional[str] = None
+    ) -> JsonDict:
         """Get the info about a given version of the user's backup
 
         Args:
-            user_id(str): the user whose current backup version we're querying
-            version(str): Optional; if None gives the most recent version
+            user_id: the user whose current backup version we're querying
+            version: Optional; if None gives the most recent version
                 otherwise a historical one.
         Raises:
             NotFoundError: if the requested backup version doesn't exist
         Returns:
-            A deferred of a info dict that gives the info about the new version.
+            A info dict that gives the info about the new version.
 
         {
             "version": "1234",
@@ -346,7 +369,7 @@ class E2eRoomKeysHandler:
             return res
 
     @trace
-    async def delete_version(self, user_id, version=None):
+    async def delete_version(self, user_id: str, version: Optional[str] = None) -> None:
         """Deletes a given version of the user's e2e_room_keys backup
 
         Args:
@@ -366,17 +389,19 @@ class E2eRoomKeysHandler:
                     raise
 
     @trace
-    async def update_version(self, user_id, version, version_info):
+    async def update_version(
+        self, user_id: str, version: str, version_info: JsonDict
+    ) -> JsonDict:
         """Update the info about a given version of the user's backup
 
         Args:
-            user_id(str): the user whose current backup version we're updating
-            version(str): the backup version we're updating
-            version_info(dict): the new information about the backup
+            user_id: the user whose current backup version we're updating
+            version: the backup version we're updating
+            version_info: the new information about the backup
         Raises:
             NotFoundError: if the requested backup version doesn't exist
         Returns:
-            A deferred of an empty dict.
+            An empty dict.
         """
         if "version" not in version_info:
             version_info["version"] = version
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index fd8de8696d..dbdfd56ff5 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1617,6 +1617,10 @@ class FederationHandler(BaseHandler):
         if event.state_key == self._server_notices_mxid:
             raise SynapseError(HTTPStatus.FORBIDDEN, "Cannot invite this user")
 
+        # We retrieve the room member handler here as to not cause a cyclic dependency
+        member_handler = self.hs.get_room_member_handler()
+        member_handler.ratelimit_invite(event.room_id, event.state_key)
+
         # keep a record of the room version, if we don't yet know it.
         # (this may get overwritten if we later get a different room version in a
         # join dance).
@@ -2093,6 +2097,11 @@ class FederationHandler(BaseHandler):
         if event.type == EventTypes.GuestAccess and not context.rejected:
             await self.maybe_kick_guest_users(event)
 
+        # If we are going to send this event over federation we precaclculate
+        # the joined hosts.
+        if event.internal_metadata.get_send_on_behalf_of():
+            await self.event_creation_handler.cache_joined_hosts_for_event(event)
+
         return context
 
     async def _check_for_soft_fail(
diff --git a/synapse/handlers/groups_local.py b/synapse/handlers/groups_local.py
index a2f16f77df..73eb7db633 100644
--- a/synapse/handlers/groups_local.py
+++ b/synapse/handlers/groups_local.py
@@ -15,9 +15,13 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING, Dict, Iterable, List, Set
 
 from synapse.api.errors import HttpResponseException, RequestSendFailed, SynapseError
-from synapse.types import GroupID, get_domain_from_id
+from synapse.types import GroupID, JsonDict, get_domain_from_id
+
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
 
 logger = logging.getLogger(__name__)
 
@@ -56,7 +60,7 @@ def _create_rerouter(func_name):
 
 
 class GroupsLocalWorkerHandler:
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.store = hs.get_datastore()
         self.room_list_handler = hs.get_room_list_handler()
@@ -84,7 +88,9 @@ class GroupsLocalWorkerHandler:
     get_group_role = _create_rerouter("get_group_role")
     get_group_roles = _create_rerouter("get_group_roles")
 
-    async def get_group_summary(self, group_id, requester_user_id):
+    async def get_group_summary(
+        self, group_id: str, requester_user_id: str
+    ) -> JsonDict:
         """Get the group summary for a group.
 
         If the group is remote we check that the users have valid attestations.
@@ -137,14 +143,15 @@ class GroupsLocalWorkerHandler:
 
         return res
 
-    async def get_users_in_group(self, group_id, requester_user_id):
+    async def get_users_in_group(
+        self, group_id: str, requester_user_id: str
+    ) -> JsonDict:
         """Get users in a group
         """
         if self.is_mine_id(group_id):
-            res = await self.groups_server_handler.get_users_in_group(
+            return await self.groups_server_handler.get_users_in_group(
                 group_id, requester_user_id
             )
-            return res
 
         group_server_name = get_domain_from_id(group_id)
 
@@ -178,11 +185,11 @@ class GroupsLocalWorkerHandler:
 
         return res
 
-    async def get_joined_groups(self, user_id):
+    async def get_joined_groups(self, user_id: str) -> JsonDict:
         group_ids = await self.store.get_joined_groups(user_id)
         return {"groups": group_ids}
 
-    async def get_publicised_groups_for_user(self, user_id):
+    async def get_publicised_groups_for_user(self, user_id: str) -> JsonDict:
         if self.hs.is_mine_id(user_id):
             result = await self.store.get_publicised_groups_for_user(user_id)
 
@@ -206,8 +213,10 @@ class GroupsLocalWorkerHandler:
             # TODO: Verify attestations
             return {"groups": result}
 
-    async def bulk_get_publicised_groups(self, user_ids, proxy=True):
-        destinations = {}
+    async def bulk_get_publicised_groups(
+        self, user_ids: Iterable[str], proxy: bool = True
+    ) -> JsonDict:
+        destinations = {}  # type: Dict[str, Set[str]]
         local_users = set()
 
         for user_id in user_ids:
@@ -220,7 +229,7 @@ class GroupsLocalWorkerHandler:
             raise SynapseError(400, "Some user_ids are not local")
 
         results = {}
-        failed_results = []
+        failed_results = []  # type: List[str]
         for destination, dest_user_ids in destinations.items():
             try:
                 r = await self.transport_client.bulk_get_publicised_groups(
@@ -242,7 +251,7 @@ class GroupsLocalWorkerHandler:
 
 
 class GroupsLocalHandler(GroupsLocalWorkerHandler):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
         # Ensure attestations get renewed
@@ -271,7 +280,9 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
 
     set_group_join_policy = _create_rerouter("set_group_join_policy")
 
-    async def create_group(self, group_id, user_id, content):
+    async def create_group(
+        self, group_id: str, user_id: str, content: JsonDict
+    ) -> JsonDict:
         """Create a group
         """
 
@@ -284,27 +295,7 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
             local_attestation = None
             remote_attestation = None
         else:
-            local_attestation = self.attestations.create_attestation(group_id, user_id)
-            content["attestation"] = local_attestation
-
-            content["user_profile"] = await self.profile_handler.get_profile(user_id)
-
-            try:
-                res = await self.transport_client.create_group(
-                    get_domain_from_id(group_id), group_id, user_id, content
-                )
-            except HttpResponseException as e:
-                raise e.to_synapse_error()
-            except RequestSendFailed:
-                raise SynapseError(502, "Failed to contact group server")
-
-            remote_attestation = res["attestation"]
-            await self.attestations.verify_attestation(
-                remote_attestation,
-                group_id=group_id,
-                user_id=user_id,
-                server_name=get_domain_from_id(group_id),
-            )
+            raise SynapseError(400, "Unable to create remote groups")
 
         is_publicised = content.get("publicise", False)
         token = await self.store.register_user_group_membership(
@@ -320,7 +311,9 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
 
         return res
 
-    async def join_group(self, group_id, user_id, content):
+    async def join_group(
+        self, group_id: str, user_id: str, content: JsonDict
+    ) -> JsonDict:
         """Request to join a group
         """
         if self.is_mine_id(group_id):
@@ -391,7 +384,9 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
 
         return {}
 
-    async def accept_invite(self, group_id, user_id, content):
+    async def accept_invite(
+        self, group_id: str, user_id: str, content: JsonDict
+    ) -> JsonDict:
         """Accept an invite to a group
         """
         if self.is_mine_id(group_id):
@@ -436,7 +431,9 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
 
         return {}
 
-    async def invite(self, group_id, user_id, requester_user_id, config):
+    async def invite(
+        self, group_id: str, user_id: str, requester_user_id: str, config: JsonDict
+    ) -> JsonDict:
         """Invite a user to a group
         """
         content = {"requester_user_id": requester_user_id, "config": config}
@@ -460,7 +457,9 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
 
         return res
 
-    async def on_invite(self, group_id, user_id, content):
+    async def on_invite(
+        self, group_id: str, user_id: str, content: JsonDict
+    ) -> JsonDict:
         """One of our users were invited to a group
         """
         # TODO: Support auto join and rejection
@@ -491,8 +490,8 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
         return {"state": "invite", "user_profile": user_profile}
 
     async def remove_user_from_group(
-        self, group_id, user_id, requester_user_id, content
-    ):
+        self, group_id: str, user_id: str, requester_user_id: str, content: JsonDict
+    ) -> JsonDict:
         """Remove a user from a group
         """
         if user_id == requester_user_id:
@@ -525,7 +524,9 @@ class GroupsLocalHandler(GroupsLocalWorkerHandler):
 
         return res
 
-    async def user_removed_from_group(self, group_id, user_id, content):
+    async def user_removed_from_group(
+        self, group_id: str, user_id: str, content: JsonDict
+    ) -> None:
         """One of our users was removed/kicked from a group
         """
         # TODO: Check if user in group
diff --git a/synapse/handlers/identity.py b/synapse/handlers/identity.py
index c05036ad1f..4f7137539b 100644
--- a/synapse/handlers/identity.py
+++ b/synapse/handlers/identity.py
@@ -27,9 +27,11 @@ from synapse.api.errors import (
     HttpResponseException,
     SynapseError,
 )
+from synapse.api.ratelimiting import Ratelimiter
 from synapse.config.emailconfig import ThreepidBehaviour
 from synapse.http import RequestTimedOutError
 from synapse.http.client import SimpleHttpClient
+from synapse.http.site import SynapseRequest
 from synapse.types import JsonDict, Requester
 from synapse.util import json_decoder
 from synapse.util.hash import sha256_and_url_safe_base64
@@ -57,6 +59,32 @@ class IdentityHandler(BaseHandler):
 
         self._web_client_location = hs.config.invite_client_location
 
+        # Ratelimiters for `/requestToken` endpoints.
+        self._3pid_validation_ratelimiter_ip = Ratelimiter(
+            clock=hs.get_clock(),
+            rate_hz=hs.config.ratelimiting.rc_3pid_validation.per_second,
+            burst_count=hs.config.ratelimiting.rc_3pid_validation.burst_count,
+        )
+        self._3pid_validation_ratelimiter_address = Ratelimiter(
+            clock=hs.get_clock(),
+            rate_hz=hs.config.ratelimiting.rc_3pid_validation.per_second,
+            burst_count=hs.config.ratelimiting.rc_3pid_validation.burst_count,
+        )
+
+    def ratelimit_request_token_requests(
+        self, request: SynapseRequest, medium: str, address: str,
+    ):
+        """Used to ratelimit requests to `/requestToken` by IP and address.
+
+        Args:
+            request: The associated request
+            medium: The type of threepid, e.g. "msisdn" or "email"
+            address: The actual threepid ID, e.g. the phone number or email address
+        """
+
+        self._3pid_validation_ratelimiter_ip.ratelimit((medium, request.getClientIP()))
+        self._3pid_validation_ratelimiter_address.ratelimit((medium, address))
+
     async def threepid_from_creds(
         self, id_server: str, creds: Dict[str, str]
     ) -> Optional[JsonDict]:
@@ -476,8 +504,6 @@ class IdentityHandler(BaseHandler):
         except RequestTimedOutError:
             raise SynapseError(500, "Timed out contacting identity server")
 
-        assert self.hs.config.public_baseurl
-
         # we need to tell the client to send the token back to us, since it doesn't
         # otherwise know where to send it, so add submit_url response parameter
         # (see also MSC2078)
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 9dfeab09cd..a15336bf00 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -174,7 +174,7 @@ class MessageHandler:
                 raise NotFoundError("Can't find event for token %s" % (at_token,))
 
             visible_events = await filter_events_for_client(
-                self.storage, user_id, last_events, filter_send_to_client=False
+                self.storage, user_id, last_events, filter_send_to_client=False,
             )
 
             event = last_events[0]
@@ -432,6 +432,8 @@ class EventCreationHandler:
 
         self._ephemeral_events_enabled = hs.config.enable_ephemeral_messages
 
+        self._external_cache = hs.get_external_cache()
+
     async def create_event(
         self,
         requester: Requester,
@@ -939,6 +941,8 @@ class EventCreationHandler:
 
         await self.action_generator.handle_push_actions_for_event(event, context)
 
+        await self.cache_joined_hosts_for_event(event)
+
         try:
             # If we're a worker we need to hit out to the master.
             writer_instance = self._events_shard_config.get_instance(event.room_id)
@@ -978,6 +982,44 @@ class EventCreationHandler:
             await self.store.remove_push_actions_from_staging(event.event_id)
             raise
 
+    async def cache_joined_hosts_for_event(self, event: EventBase) -> None:
+        """Precalculate the joined hosts at the event, when using Redis, so that
+        external federation senders don't have to recalculate it themselves.
+        """
+
+        if not self._external_cache.is_enabled():
+            return
+
+        # We actually store two mappings, event ID -> prev state group,
+        # state group -> joined hosts, which is much more space efficient
+        # than event ID -> joined hosts.
+        #
+        # Note: We have to cache event ID -> prev state group, as we don't
+        # store that in the DB.
+        #
+        # Note: We always set the state group -> joined hosts cache, even if
+        # we already set it, so that the expiry time is reset.
+
+        state_entry = await self.state.resolve_state_groups_for_events(
+            event.room_id, event_ids=event.prev_event_ids()
+        )
+
+        if state_entry.state_group:
+            joined_hosts = await self.store.get_joined_hosts(event.room_id, state_entry)
+
+            await self._external_cache.set(
+                "event_to_prev_state_group",
+                event.event_id,
+                state_entry.state_group,
+                expiry_ms=60 * 60 * 1000,
+            )
+            await self._external_cache.set(
+                "get_joined_hosts",
+                str(state_entry.state_group),
+                list(joined_hosts),
+                expiry_ms=60 * 60 * 1000,
+            )
+
     async def _validate_canonical_alias(
         self, directory_handler, room_alias_str: str, expected_room_id: str
     ) -> None:
diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index ba686d74b2..71008ec50d 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -102,7 +102,7 @@ class OidcHandler:
                 ) from e
 
     async def handle_oidc_callback(self, request: SynapseRequest) -> None:
-        """Handle an incoming request to /_synapse/oidc/callback
+        """Handle an incoming request to /_synapse/client/oidc/callback
 
         Since we might want to display OIDC-related errors in a user-friendly
         way, we don't raise SynapseError from here. Instead, we call
@@ -271,6 +271,12 @@ class OidcProvider:
         # user-facing name of this auth provider
         self.idp_name = provider.idp_name
 
+        # MXC URI for icon for this auth provider
+        self.idp_icon = provider.idp_icon
+
+        # optional brand identifier for this auth provider
+        self.idp_brand = provider.idp_brand
+
         self._sso_handler = hs.get_sso_handler()
 
         self._sso_handler.register_identity_provider(self)
@@ -637,7 +643,7 @@ class OidcProvider:
 
           - ``client_id``: the client ID set in ``oidc_config.client_id``
           - ``response_type``: ``code``
-          - ``redirect_uri``: the callback URL ; ``{base url}/_synapse/oidc/callback``
+          - ``redirect_uri``: the callback URL ; ``{base url}/_synapse/client/oidc/callback``
           - ``scope``: the list of scopes set in ``oidc_config.scopes``
           - ``state``: a random string
           - ``nonce``: a random string
@@ -678,7 +684,7 @@ class OidcProvider:
         request.addCookie(
             SESSION_COOKIE_NAME,
             cookie,
-            path="/_synapse/oidc",
+            path="/_synapse/client/oidc",
             max_age="3600",
             httpOnly=True,
             sameSite="lax",
@@ -699,7 +705,7 @@ class OidcProvider:
     async def handle_oidc_callback(
         self, request: SynapseRequest, session_data: "OidcSessionData", code: str
     ) -> None:
-        """Handle an incoming request to /_synapse/oidc/callback
+        """Handle an incoming request to /_synapse/client/oidc/callback
 
         By this time we have already validated the session on the synapse side, and
         now need to do the provider-specific operations. This includes:
@@ -1053,7 +1059,8 @@ class OidcSessionData:
 
 
 UserAttributeDict = TypedDict(
-    "UserAttributeDict", {"localpart": Optional[str], "display_name": Optional[str]}
+    "UserAttributeDict",
+    {"localpart": Optional[str], "display_name": Optional[str], "emails": List[str]},
 )
 C = TypeVar("C")
 
@@ -1132,11 +1139,12 @@ def jinja_finalize(thing):
 env = Environment(finalize=jinja_finalize)
 
 
-@attr.s
+@attr.s(slots=True, frozen=True)
 class JinjaOidcMappingConfig:
     subject_claim = attr.ib(type=str)
     localpart_template = attr.ib(type=Optional[Template])
     display_name_template = attr.ib(type=Optional[Template])
+    email_template = attr.ib(type=Optional[Template])
     extra_attributes = attr.ib(type=Dict[str, Template])
 
 
@@ -1153,23 +1161,17 @@ class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]):
     def parse_config(config: dict) -> JinjaOidcMappingConfig:
         subject_claim = config.get("subject_claim", "sub")
 
-        localpart_template = None  # type: Optional[Template]
-        if "localpart_template" in config:
+        def parse_template_config(option_name: str) -> Optional[Template]:
+            if option_name not in config:
+                return None
             try:
-                localpart_template = env.from_string(config["localpart_template"])
+                return env.from_string(config[option_name])
             except Exception as e:
-                raise ConfigError(
-                    "invalid jinja template", path=["localpart_template"]
-                ) from e
+                raise ConfigError("invalid jinja template", path=[option_name]) from e
 
-        display_name_template = None  # type: Optional[Template]
-        if "display_name_template" in config:
-            try:
-                display_name_template = env.from_string(config["display_name_template"])
-            except Exception as e:
-                raise ConfigError(
-                    "invalid jinja template", path=["display_name_template"]
-                ) from e
+        localpart_template = parse_template_config("localpart_template")
+        display_name_template = parse_template_config("display_name_template")
+        email_template = parse_template_config("email_template")
 
         extra_attributes = {}  # type Dict[str, Template]
         if "extra_attributes" in config:
@@ -1189,6 +1191,7 @@ class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]):
             subject_claim=subject_claim,
             localpart_template=localpart_template,
             display_name_template=display_name_template,
+            email_template=email_template,
             extra_attributes=extra_attributes,
         )
 
@@ -1210,16 +1213,23 @@ class JinjaOidcMappingProvider(OidcMappingProvider[JinjaOidcMappingConfig]):
             # a usable mxid.
             localpart += str(failures) if failures else ""
 
-        display_name = None  # type: Optional[str]
-        if self._config.display_name_template is not None:
-            display_name = self._config.display_name_template.render(
-                user=userinfo
-            ).strip()
+        def render_template_field(template: Optional[Template]) -> Optional[str]:
+            if template is None:
+                return None
+            return template.render(user=userinfo).strip()
 
-            if display_name == "":
-                display_name = None
+        display_name = render_template_field(self._config.display_name_template)
+        if display_name == "":
+            display_name = None
 
-        return UserAttributeDict(localpart=localpart, display_name=display_name)
+        emails = []  # type: List[str]
+        email = render_template_field(self._config.email_template)
+        if email:
+            emails.append(email)
+
+        return UserAttributeDict(
+            localpart=localpart, display_name=display_name, emails=emails
+        )
 
     async def get_extra_attributes(self, userinfo: UserInfo, token: Token) -> JsonDict:
         extras = {}  # type: Dict[str, str]
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index a2cf0f6f3e..49b085269b 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -14,8 +14,9 @@
 # limitations under the License.
 
 """Contains functions for registering clients."""
+
 import logging
-from typing import TYPE_CHECKING, List, Optional, Tuple
+from typing import TYPE_CHECKING, Iterable, List, Optional, Tuple
 
 from synapse import types
 from synapse.api.constants import MAX_USERID_LENGTH, EventTypes, JoinRules, LoginType
@@ -152,7 +153,7 @@ class RegistrationHandler(BaseHandler):
         user_type: Optional[str] = None,
         default_display_name: Optional[str] = None,
         address: Optional[str] = None,
-        bind_emails: List[str] = [],
+        bind_emails: Iterable[str] = [],
         by_admin: bool = False,
         user_agent_ips: Optional[List[Tuple[str, str]]] = None,
     ) -> str:
@@ -693,6 +694,8 @@ class RegistrationHandler(BaseHandler):
             access_token: The access token of the newly logged in device, or
                 None if `inhibit_login` enabled.
         """
+        # TODO: 3pid registration can actually happen on the workers. Consider
+        # refactoring it.
         if self.hs.config.worker_app:
             await self._post_registration_client(
                 user_id=user_id, auth_result=auth_result, access_token=access_token
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 3bece6d668..07b2187eb1 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -38,7 +38,6 @@ from synapse.api.filtering import Filter
 from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
 from synapse.events import EventBase
 from synapse.events.utils import copy_power_levels_contents
-from synapse.http.endpoint import parse_and_validate_server_name
 from synapse.storage.state import StateFilter
 from synapse.types import (
     JsonDict,
@@ -55,6 +54,7 @@ from synapse.types import (
 from synapse.util import stringutils
 from synapse.util.async_helpers import Linearizer
 from synapse.util.caches.response_cache import ResponseCache
+from synapse.util.stringutils import parse_and_validate_server_name
 from synapse.visibility import filter_events_for_client
 
 from ._base import BaseHandler
@@ -126,6 +126,10 @@ class RoomCreationHandler(BaseHandler):
 
         self.third_party_event_rules = hs.get_third_party_event_rules()
 
+        self._invite_burst_count = (
+            hs.config.ratelimiting.rc_invites_per_room.burst_count
+        )
+
     async def upgrade_room(
         self, requester: Requester, old_room_id: str, new_version: RoomVersion
     ) -> str:
@@ -662,6 +666,9 @@ class RoomCreationHandler(BaseHandler):
             invite_3pid_list = []
             invite_list = []
 
+        if len(invite_list) + len(invite_3pid_list) > self._invite_burst_count:
+            raise SynapseError(400, "Cannot invite so many users at once")
+
         await self.event_creation_handler.assert_accepted_privacy_policy(requester)
 
         power_level_content_override = config.get("power_level_content_override")
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index e001e418f9..d335da6f19 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -85,6 +85,17 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
             burst_count=hs.config.ratelimiting.rc_joins_remote.burst_count,
         )
 
+        self._invites_per_room_limiter = Ratelimiter(
+            clock=self.clock,
+            rate_hz=hs.config.ratelimiting.rc_invites_per_room.per_second,
+            burst_count=hs.config.ratelimiting.rc_invites_per_room.burst_count,
+        )
+        self._invites_per_user_limiter = Ratelimiter(
+            clock=self.clock,
+            rate_hz=hs.config.ratelimiting.rc_invites_per_user.per_second,
+            burst_count=hs.config.ratelimiting.rc_invites_per_user.burst_count,
+        )
+
         # This is only used to get at ratelimit function, and
         # maybe_kick_guest_users. It's fine there are multiple of these as
         # it doesn't store state.
@@ -144,6 +155,12 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
         """
         raise NotImplementedError()
 
+    def ratelimit_invite(self, room_id: str, invitee_user_id: str):
+        """Ratelimit invites by room and by target user.
+        """
+        self._invites_per_room_limiter.ratelimit(room_id)
+        self._invites_per_user_limiter.ratelimit(invitee_user_id)
+
     async def _local_membership_update(
         self,
         requester: Requester,
@@ -387,8 +404,12 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                 raise SynapseError(403, "This room has been blocked on this server")
 
         if effective_membership_state == Membership.INVITE:
+            target_id = target.to_string()
+            if ratelimit:
+                self.ratelimit_invite(room_id, target_id)
+
             # block any attempts to invite the server notices mxid
-            if target.to_string() == self._server_notices_mxid:
+            if target_id == self._server_notices_mxid:
                 raise SynapseError(HTTPStatus.FORBIDDEN, "Cannot invite this user")
 
             block_invite = False
@@ -412,7 +433,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
                     block_invite = True
 
                 if not await self.spam_checker.user_may_invite(
-                    requester.user.to_string(), target.to_string(), room_id
+                    requester.user.to_string(), target_id, room_id
                 ):
                     logger.info("Blocking invite due to spam checker")
                     block_invite = True
diff --git a/synapse/handlers/saml_handler.py b/synapse/handlers/saml_handler.py
index a8376543c9..e88fd59749 100644
--- a/synapse/handlers/saml_handler.py
+++ b/synapse/handlers/saml_handler.py
@@ -78,6 +78,11 @@ class SamlHandler(BaseHandler):
         # user-facing name of this auth provider
         self.idp_name = "SAML"
 
+        # we do not currently support icons/brands for SAML auth, but this is required by
+        # the SsoIdentityProvider protocol type.
+        self.idp_icon = None
+        self.idp_brand = None
+
         # a map from saml session id to Saml2SessionData object
         self._outstanding_requests_dict = {}  # type: Dict[str, Saml2SessionData]
 
@@ -128,7 +133,7 @@ class SamlHandler(BaseHandler):
         raise Exception("prepare_for_authenticate didn't return a Location header")
 
     async def handle_saml_response(self, request: SynapseRequest) -> None:
-        """Handle an incoming request to /_matrix/saml2/authn_response
+        """Handle an incoming request to /_synapse/client/saml2/authn_response
 
         Args:
             request: the incoming request from the browser. We'll
diff --git a/synapse/handlers/search.py b/synapse/handlers/search.py
index 66f1bbcfc4..94062e79cb 100644
--- a/synapse/handlers/search.py
+++ b/synapse/handlers/search.py
@@ -15,23 +15,28 @@
 
 import itertools
 import logging
-from typing import Iterable
+from typing import TYPE_CHECKING, Dict, Iterable, List, Optional
 
 from unpaddedbase64 import decode_base64, encode_base64
 
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import NotFoundError, SynapseError
 from synapse.api.filtering import Filter
+from synapse.events import EventBase
 from synapse.storage.state import StateFilter
+from synapse.types import JsonDict, UserID
 from synapse.visibility import filter_events_for_client
 
 from ._base import BaseHandler
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 class SearchHandler(BaseHandler):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self._event_serializer = hs.get_event_client_serializer()
         self.storage = hs.get_storage()
@@ -87,13 +92,15 @@ class SearchHandler(BaseHandler):
 
         return historical_room_ids
 
-    async def search(self, user, content, batch=None):
+    async def search(
+        self, user: UserID, content: JsonDict, batch: Optional[str] = None
+    ) -> JsonDict:
         """Performs a full text search for a user.
 
         Args:
-            user (UserID)
-            content (dict): Search parameters
-            batch (str): The next_batch parameter. Used for pagination.
+            user
+            content: Search parameters
+            batch: The next_batch parameter. Used for pagination.
 
         Returns:
             dict to be returned to the client with results of search
@@ -186,7 +193,7 @@ class SearchHandler(BaseHandler):
         # If doing a subset of all rooms seearch, check if any of the rooms
         # are from an upgraded room, and search their contents as well
         if search_filter.rooms:
-            historical_room_ids = []
+            historical_room_ids = []  # type: List[str]
             for room_id in search_filter.rooms:
                 # Add any previous rooms to the search if they exist
                 ids = await self.get_old_rooms_from_upgraded_room(room_id)
@@ -209,8 +216,10 @@ class SearchHandler(BaseHandler):
 
         rank_map = {}  # event_id -> rank of event
         allowed_events = []
-        room_groups = {}  # Holds result of grouping by room, if applicable
-        sender_group = {}  # Holds result of grouping by sender, if applicable
+        # Holds result of grouping by room, if applicable
+        room_groups = {}  # type: Dict[str, JsonDict]
+        # Holds result of grouping by sender, if applicable
+        sender_group = {}  # type: Dict[str, JsonDict]
 
         # Holds the next_batch for the entire result set if one of those exists
         global_next_batch = None
@@ -254,7 +263,7 @@ class SearchHandler(BaseHandler):
                 s["results"].append(e.event_id)
 
         elif order_by == "recent":
-            room_events = []
+            room_events = []  # type: List[EventBase]
             i = 0
 
             pagination_token = batch_token
@@ -418,13 +427,10 @@ class SearchHandler(BaseHandler):
 
         state_results = {}
         if include_state:
-            rooms = {e.room_id for e in allowed_events}
-            for room_id in rooms:
+            for room_id in {e.room_id for e in allowed_events}:
                 state = await self.state_handler.get_current_state(room_id)
                 state_results[room_id] = list(state.values())
 
-            state_results.values()
-
         # We're now about to serialize the events. We should not make any
         # blocking calls after this. Otherwise the 'age' will be wrong
 
@@ -448,9 +454,9 @@ class SearchHandler(BaseHandler):
 
         if state_results:
             s = {}
-            for room_id, state in state_results.items():
+            for room_id, state_events in state_results.items():
                 s[room_id] = await self._event_serializer.serialize_events(
-                    state, time_now
+                    state_events, time_now
                 )
 
             rooms_cat_res["state"] = s
diff --git a/synapse/handlers/set_password.py b/synapse/handlers/set_password.py
index a5d67f828f..84af2dde7e 100644
--- a/synapse/handlers/set_password.py
+++ b/synapse/handlers/set_password.py
@@ -13,24 +13,26 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
-from typing import Optional
+from typing import TYPE_CHECKING, Optional
 
 from synapse.api.errors import Codes, StoreError, SynapseError
 from synapse.types import Requester
 
 from ._base import BaseHandler
 
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 class SetPasswordHandler(BaseHandler):
     """Handler which deals with changing user account passwords"""
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self._auth_handler = hs.get_auth_handler()
         self._device_handler = hs.get_device_handler()
-        self._password_policy_handler = hs.get_password_policy_handler()
 
     async def set_password(
         self,
@@ -38,7 +40,7 @@ class SetPasswordHandler(BaseHandler):
         password_hash: str,
         logout_devices: bool,
         requester: Optional[Requester] = None,
-    ):
+    ) -> None:
         if not self.hs.config.password_localdb_enabled:
             raise SynapseError(403, "Password change disabled", errcode=Codes.FORBIDDEN)
 
diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py
index dcc85e9871..b450668f1c 100644
--- a/synapse/handlers/sso.py
+++ b/synapse/handlers/sso.py
@@ -14,21 +14,31 @@
 # limitations under the License.
 import abc
 import logging
-from typing import TYPE_CHECKING, Awaitable, Callable, Dict, List, Mapping, Optional
+from typing import (
+    TYPE_CHECKING,
+    Awaitable,
+    Callable,
+    Dict,
+    Iterable,
+    Mapping,
+    Optional,
+    Set,
+)
 from urllib.parse import urlencode
 
 import attr
 from typing_extensions import NoReturn, Protocol
 
 from twisted.web.http import Request
+from twisted.web.iweb import IRequest
 
 from synapse.api.constants import LoginType
-from synapse.api.errors import Codes, RedirectException, SynapseError
+from synapse.api.errors import Codes, NotFoundError, RedirectException, SynapseError
 from synapse.handlers.ui_auth import UIAuthSessionDataConstants
 from synapse.http import get_request_user_agent
-from synapse.http.server import respond_with_html
+from synapse.http.server import respond_with_html, respond_with_redirect
 from synapse.http.site import SynapseRequest
-from synapse.types import JsonDict, UserID, contains_invalid_mxid_characters
+from synapse.types import Collection, JsonDict, UserID, contains_invalid_mxid_characters
 from synapse.util.async_helpers import Linearizer
 from synapse.util.stringutils import random_string
 
@@ -75,6 +85,16 @@ class SsoIdentityProvider(Protocol):
     def idp_name(self) -> str:
         """User-facing name for this provider"""
 
+    @property
+    def idp_icon(self) -> Optional[str]:
+        """Optional MXC URI for user-facing icon"""
+        return None
+
+    @property
+    def idp_brand(self) -> Optional[str]:
+        """Optional branding identifier"""
+        return None
+
     @abc.abstractmethod
     async def handle_redirect_request(
         self,
@@ -104,7 +124,7 @@ class UserAttributes:
     # enter one.
     localpart = attr.ib(type=Optional[str])
     display_name = attr.ib(type=Optional[str], default=None)
-    emails = attr.ib(type=List[str], default=attr.Factory(list))
+    emails = attr.ib(type=Collection[str], default=attr.Factory(list))
 
 
 @attr.s(slots=True)
@@ -119,7 +139,7 @@ class UsernameMappingSession:
 
     # attributes returned by the ID mapper
     display_name = attr.ib(type=Optional[str])
-    emails = attr.ib(type=List[str])
+    emails = attr.ib(type=Collection[str])
 
     # An optional dictionary of extra attributes to be provided to the client in the
     # login response.
@@ -131,6 +151,12 @@ class UsernameMappingSession:
     # expiry time for the session, in milliseconds
     expiry_time_ms = attr.ib(type=int)
 
+    # choices made by the user
+    chosen_localpart = attr.ib(type=Optional[str], default=None)
+    use_display_name = attr.ib(type=bool, default=True)
+    emails_to_use = attr.ib(type=Collection[str], default=())
+    terms_accepted_version = attr.ib(type=Optional[str], default=None)
+
 
 # the HTTP cookie used to track the mapping session id
 USERNAME_MAPPING_SESSION_COOKIE_NAME = b"username_mapping_session"
@@ -165,6 +191,8 @@ class SsoHandler:
         # map from idp_id to SsoIdentityProvider
         self._identity_providers = {}  # type: Dict[str, SsoIdentityProvider]
 
+        self._consent_at_registration = hs.config.consent.user_consent_at_registration
+
     def register_identity_provider(self, p: SsoIdentityProvider):
         p_id = p.idp_id
         assert p_id not in self._identity_providers
@@ -230,7 +258,10 @@ class SsoHandler:
         respond_with_html(request, code, html)
 
     async def handle_redirect_request(
-        self, request: SynapseRequest, client_redirect_url: bytes,
+        self,
+        request: SynapseRequest,
+        client_redirect_url: bytes,
+        idp_id: Optional[str],
     ) -> str:
         """Handle a request to /login/sso/redirect
 
@@ -238,6 +269,7 @@ class SsoHandler:
             request: incoming HTTP request
             client_redirect_url: the URL that we should redirect the
                 client to after login.
+            idp_id: optional identity provider chosen by the client
 
         Returns:
              the URI to redirect to
@@ -247,10 +279,19 @@ class SsoHandler:
                 400, "Homeserver not configured for SSO.", errcode=Codes.UNRECOGNIZED
             )
 
+        # if the client chose an IdP, use that
+        idp = None  # type: Optional[SsoIdentityProvider]
+        if idp_id:
+            idp = self._identity_providers.get(idp_id)
+            if not idp:
+                raise NotFoundError("Unknown identity provider")
+
         # if we only have one auth provider, redirect to it directly
-        if len(self._identity_providers) == 1:
-            ap = next(iter(self._identity_providers.values()))
-            return await ap.handle_redirect_request(request, client_redirect_url)
+        elif len(self._identity_providers) == 1:
+            idp = next(iter(self._identity_providers.values()))
+
+        if idp:
+            return await idp.handle_redirect_request(request, client_redirect_url)
 
         # otherwise, redirect to the IDP picker
         return "/_synapse/client/pick_idp?" + urlencode(
@@ -364,6 +405,8 @@ class SsoHandler:
                 to an additional page. (e.g. to prompt for more information)
 
         """
+        new_user = False
+
         # grab a lock while we try to find a mapping for this user. This seems...
         # optimistic, especially for implementations that end up redirecting to
         # interstitial pages.
@@ -404,9 +447,14 @@ class SsoHandler:
                     get_request_user_agent(request),
                     request.getClientIP(),
                 )
+                new_user = True
 
         await self._auth_handler.complete_sso_login(
-            user_id, request, client_redirect_url, extra_login_attributes
+            user_id,
+            request,
+            client_redirect_url,
+            extra_login_attributes,
+            new_user=new_user,
         )
 
     async def _call_attribute_mapper(
@@ -496,7 +544,7 @@ class SsoHandler:
         logger.info("Recorded registration session id %s", session_id)
 
         # Set the cookie and redirect to the username picker
-        e = RedirectException(b"/_synapse/client/pick_username")
+        e = RedirectException(b"/_synapse/client/pick_username/account_details")
         e.cookies.append(
             b"%s=%s; path=/"
             % (USERNAME_MAPPING_SESSION_COOKIE_NAME, session_id.encode("ascii"))
@@ -624,6 +672,25 @@ class SsoHandler:
         )
         respond_with_html(request, 200, html)
 
+    def get_mapping_session(self, session_id: str) -> UsernameMappingSession:
+        """Look up the given username mapping session
+
+        If it is not found, raises a SynapseError with an http code of 400
+
+        Args:
+            session_id: session to look up
+        Returns:
+            active mapping session
+        Raises:
+            SynapseError if the session is not found/has expired
+        """
+        self._expire_old_sessions()
+        session = self._username_mapping_sessions.get(session_id)
+        if session:
+            return session
+        logger.info("Couldn't find session id %s", session_id)
+        raise SynapseError(400, "unknown session")
+
     async def check_username_availability(
         self, localpart: str, session_id: str,
     ) -> bool:
@@ -640,12 +707,7 @@ class SsoHandler:
 
         # make sure that there is a valid mapping session, to stop people dictionary-
         # scanning for accounts
-
-        self._expire_old_sessions()
-        session = self._username_mapping_sessions.get(session_id)
-        if not session:
-            logger.info("Couldn't find session id %s", session_id)
-            raise SynapseError(400, "unknown session")
+        self.get_mapping_session(session_id)
 
         logger.info(
             "[session %s] Checking for availability of username %s",
@@ -662,7 +724,12 @@ class SsoHandler:
         return not user_infos
 
     async def handle_submit_username_request(
-        self, request: SynapseRequest, localpart: str, session_id: str
+        self,
+        request: SynapseRequest,
+        session_id: str,
+        localpart: str,
+        use_display_name: bool,
+        emails_to_use: Iterable[str],
     ) -> None:
         """Handle a request to the username-picker 'submit' endpoint
 
@@ -672,21 +739,90 @@ class SsoHandler:
             request: HTTP request
             localpart: localpart requested by the user
             session_id: ID of the username mapping session, extracted from a cookie
+            use_display_name: whether the user wants to use the suggested display name
+            emails_to_use: emails that the user would like to use
         """
-        self._expire_old_sessions()
-        session = self._username_mapping_sessions.get(session_id)
-        if not session:
-            logger.info("Couldn't find session id %s", session_id)
-            raise SynapseError(400, "unknown session")
+        session = self.get_mapping_session(session_id)
+
+        # update the session with the user's choices
+        session.chosen_localpart = localpart
+        session.use_display_name = use_display_name
+
+        emails_from_idp = set(session.emails)
+        filtered_emails = set()  # type: Set[str]
+
+        # we iterate through the list rather than just building a set conjunction, so
+        # that we can log attempts to use unknown addresses
+        for email in emails_to_use:
+            if email in emails_from_idp:
+                filtered_emails.add(email)
+            else:
+                logger.warning(
+                    "[session %s] ignoring user request to use unknown email address %r",
+                    session_id,
+                    email,
+                )
+        session.emails_to_use = filtered_emails
 
-        logger.info("[session %s] Registering localpart %s", session_id, localpart)
+        # we may now need to collect consent from the user, in which case, redirect
+        # to the consent-extraction-unit
+        if self._consent_at_registration:
+            redirect_url = b"/_synapse/client/new_user_consent"
+
+        # otherwise, redirect to the completion page
+        else:
+            redirect_url = b"/_synapse/client/sso_register"
+
+        respond_with_redirect(request, redirect_url)
+
+    async def handle_terms_accepted(
+        self, request: Request, session_id: str, terms_version: str
+    ):
+        """Handle a request to the new-user 'consent' endpoint
+
+        Will serve an HTTP response to the request.
+
+        Args:
+            request: HTTP request
+            session_id: ID of the username mapping session, extracted from a cookie
+            terms_version: the version of the terms which the user viewed and consented
+                to
+        """
+        logger.info(
+            "[session %s] User consented to terms version %s",
+            session_id,
+            terms_version,
+        )
+        session = self.get_mapping_session(session_id)
+        session.terms_accepted_version = terms_version
+
+        # we're done; now we can register the user
+        respond_with_redirect(request, b"/_synapse/client/sso_register")
+
+    async def register_sso_user(self, request: Request, session_id: str) -> None:
+        """Called once we have all the info we need to register a new user.
+
+        Does so and serves an HTTP response
+
+        Args:
+            request: HTTP request
+            session_id: ID of the username mapping session, extracted from a cookie
+        """
+        session = self.get_mapping_session(session_id)
+
+        logger.info(
+            "[session %s] Registering localpart %s",
+            session_id,
+            session.chosen_localpart,
+        )
 
         attributes = UserAttributes(
-            localpart=localpart,
-            display_name=session.display_name,
-            emails=session.emails,
+            localpart=session.chosen_localpart, emails=session.emails_to_use,
         )
 
+        if session.use_display_name:
+            attributes.display_name = session.display_name
+
         # the following will raise a 400 error if the username has been taken in the
         # meantime.
         user_id = await self._register_mapped_user(
@@ -697,7 +833,12 @@ class SsoHandler:
             request.getClientIP(),
         )
 
-        logger.info("[session %s] Registered userid %s", session_id, user_id)
+        logger.info(
+            "[session %s] Registered userid %s with attributes %s",
+            session_id,
+            user_id,
+            attributes,
+        )
 
         # delete the mapping session and the cookie
         del self._username_mapping_sessions[session_id]
@@ -710,11 +851,21 @@ class SsoHandler:
             path=b"/",
         )
 
+        auth_result = {}
+        if session.terms_accepted_version:
+            # TODO: make this less awful.
+            auth_result[LoginType.TERMS] = True
+
+        await self._registration_handler.post_registration_actions(
+            user_id, auth_result, access_token=None
+        )
+
         await self._auth_handler.complete_sso_login(
             user_id,
             request,
             session.client_redirect_url,
             session.extra_login_attributes,
+            new_user=True,
         )
 
     def _expire_old_sessions(self):
@@ -728,3 +879,14 @@ class SsoHandler:
         for session_id in to_expire:
             logger.info("Expiring mapping session %s", session_id)
             del self._username_mapping_sessions[session_id]
+
+
+def get_username_mapping_session_cookie_from_request(request: IRequest) -> str:
+    """Extract the session ID from the cookie
+
+    Raises a SynapseError if the cookie isn't found
+    """
+    session_id = request.getCookie(USERNAME_MAPPING_SESSION_COOKIE_NAME)
+    if not session_id:
+        raise SynapseError(code=400, msg="missing session_id")
+    return session_id.decode("ascii", errors="replace")
diff --git a/synapse/handlers/state_deltas.py b/synapse/handlers/state_deltas.py
index fb4f70e8e2..b3f9875358 100644
--- a/synapse/handlers/state_deltas.py
+++ b/synapse/handlers/state_deltas.py
@@ -14,15 +14,25 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING, Optional
+
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
 
 logger = logging.getLogger(__name__)
 
 
 class StateDeltasHandler:
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.store = hs.get_datastore()
 
-    async def _get_key_change(self, prev_event_id, event_id, key_name, public_value):
+    async def _get_key_change(
+        self,
+        prev_event_id: Optional[str],
+        event_id: Optional[str],
+        key_name: str,
+        public_value: str,
+    ) -> Optional[bool]:
         """Given two events check if the `key_name` field in content changed
         from not matching `public_value` to doing so.
 
diff --git a/synapse/handlers/stats.py b/synapse/handlers/stats.py
index dc62b21c06..d261d7cd4e 100644
--- a/synapse/handlers/stats.py
+++ b/synapse/handlers/stats.py
@@ -12,13 +12,19 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 import logging
 from collections import Counter
+from typing import TYPE_CHECKING, Any, Dict, Iterable, Optional, Tuple
+
+from typing_extensions import Counter as CounterType
 
 from synapse.api.constants import EventTypes, Membership
 from synapse.metrics import event_processing_positions
 from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.types import JsonDict
+
+if TYPE_CHECKING:
+    from synapse.app.homeserver import HomeServer
 
 logger = logging.getLogger(__name__)
 
@@ -31,7 +37,7 @@ class StatsHandler:
     Heavily derived from UserDirectoryHandler
     """
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.store = hs.get_datastore()
         self.state = hs.get_state_handler()
@@ -44,7 +50,7 @@ class StatsHandler:
         self.stats_enabled = hs.config.stats_enabled
 
         # The current position in the current_state_delta stream
-        self.pos = None
+        self.pos = None  # type: Optional[int]
 
         # Guard to ensure we only process deltas one at a time
         self._is_processing = False
@@ -56,7 +62,7 @@ class StatsHandler:
             # we start populating stats
             self.clock.call_later(0, self.notify_new_event)
 
-    def notify_new_event(self):
+    def notify_new_event(self) -> None:
         """Called when there may be more deltas to process
         """
         if not self.stats_enabled or self._is_processing:
@@ -72,7 +78,7 @@ class StatsHandler:
 
         run_as_background_process("stats.notify_new_event", process)
 
-    async def _unsafe_process(self):
+    async def _unsafe_process(self) -> None:
         # If self.pos is None then means we haven't fetched it from DB
         if self.pos is None:
             self.pos = await self.store.get_stats_positions()
@@ -110,10 +116,10 @@ class StatsHandler:
             )
 
             for room_id, fields in room_count.items():
-                room_deltas.setdefault(room_id, {}).update(fields)
+                room_deltas.setdefault(room_id, Counter()).update(fields)
 
             for user_id, fields in user_count.items():
-                user_deltas.setdefault(user_id, {}).update(fields)
+                user_deltas.setdefault(user_id, Counter()).update(fields)
 
             logger.debug("room_deltas: %s", room_deltas)
             logger.debug("user_deltas: %s", user_deltas)
@@ -131,19 +137,20 @@ class StatsHandler:
 
             self.pos = max_pos
 
-    async def _handle_deltas(self, deltas):
+    async def _handle_deltas(
+        self, deltas: Iterable[JsonDict]
+    ) -> Tuple[Dict[str, CounterType[str]], Dict[str, CounterType[str]]]:
         """Called with the state deltas to process
 
         Returns:
-            tuple[dict[str, Counter], dict[str, counter]]
             Two dicts: the room deltas and the user deltas,
             mapping from room/user ID to changes in the various fields.
         """
 
-        room_to_stats_deltas = {}
-        user_to_stats_deltas = {}
+        room_to_stats_deltas = {}  # type: Dict[str, CounterType[str]]
+        user_to_stats_deltas = {}  # type: Dict[str, CounterType[str]]
 
-        room_to_state_updates = {}
+        room_to_state_updates = {}  # type: Dict[str, Dict[str, Any]]
 
         for delta in deltas:
             typ = delta["type"]
@@ -173,7 +180,7 @@ class StatsHandler:
                 )
                 continue
 
-            event_content = {}
+            event_content = {}  # type: JsonDict
 
             sender = None
             if event_id is not None:
@@ -257,13 +264,13 @@ class StatsHandler:
                     )
 
                     if has_changed_joinedness:
-                        delta = +1 if membership == Membership.JOIN else -1
+                        membership_delta = +1 if membership == Membership.JOIN else -1
 
                         user_to_stats_deltas.setdefault(user_id, Counter())[
                             "joined_rooms"
-                        ] += delta
+                        ] += membership_delta
 
-                        room_stats_delta["local_users_in_room"] += delta
+                        room_stats_delta["local_users_in_room"] += membership_delta
 
             elif typ == EventTypes.Create:
                 room_state["is_federatable"] = (
diff --git a/synapse/handlers/typing.py b/synapse/handlers/typing.py
index e919a8f9ed..3f0dfc7a74 100644
--- a/synapse/handlers/typing.py
+++ b/synapse/handlers/typing.py
@@ -15,13 +15,13 @@
 import logging
 import random
 from collections import namedtuple
-from typing import TYPE_CHECKING, List, Set, Tuple
+from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Set, Tuple
 
 from synapse.api.errors import AuthError, ShadowBanError, SynapseError
 from synapse.appservice import ApplicationService
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.replication.tcp.streams import TypingStream
-from synapse.types import JsonDict, UserID, get_domain_from_id
+from synapse.types import JsonDict, Requester, UserID, get_domain_from_id
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.metrics import Measure
 from synapse.util.wheel_timer import WheelTimer
@@ -65,17 +65,17 @@ class FollowerTypingHandler:
             )
 
         # map room IDs to serial numbers
-        self._room_serials = {}
+        self._room_serials = {}  # type: Dict[str, int]
         # map room IDs to sets of users currently typing
-        self._room_typing = {}
+        self._room_typing = {}  # type: Dict[str, Set[str]]
 
-        self._member_last_federation_poke = {}
+        self._member_last_federation_poke = {}  # type: Dict[RoomMember, int]
         self.wheel_timer = WheelTimer(bucket_size=5000)
         self._latest_room_serial = 0
 
         self.clock.looping_call(self._handle_timeouts, 5000)
 
-    def _reset(self):
+    def _reset(self) -> None:
         """Reset the typing handler's data caches.
         """
         # map room IDs to serial numbers
@@ -86,7 +86,7 @@ class FollowerTypingHandler:
         self._member_last_federation_poke = {}
         self.wheel_timer = WheelTimer(bucket_size=5000)
 
-    def _handle_timeouts(self):
+    def _handle_timeouts(self) -> None:
         logger.debug("Checking for typing timeouts")
 
         now = self.clock.time_msec()
@@ -96,7 +96,7 @@ class FollowerTypingHandler:
         for member in members:
             self._handle_timeout_for_member(now, member)
 
-    def _handle_timeout_for_member(self, now: int, member: RoomMember):
+    def _handle_timeout_for_member(self, now: int, member: RoomMember) -> None:
         if not self.is_typing(member):
             # Nothing to do if they're no longer typing
             return
@@ -114,10 +114,10 @@ class FollowerTypingHandler:
         # each person typing.
         self.wheel_timer.insert(now=now, obj=member, then=now + 60 * 1000)
 
-    def is_typing(self, member):
+    def is_typing(self, member: RoomMember) -> bool:
         return member.user_id in self._room_typing.get(member.room_id, [])
 
-    async def _push_remote(self, member, typing):
+    async def _push_remote(self, member: RoomMember, typing: bool) -> None:
         if not self.federation:
             return
 
@@ -148,7 +148,7 @@ class FollowerTypingHandler:
 
     def process_replication_rows(
         self, token: int, rows: List[TypingStream.TypingStreamRow]
-    ):
+    ) -> None:
         """Should be called whenever we receive updates for typing stream.
         """
 
@@ -178,7 +178,7 @@ class FollowerTypingHandler:
 
     async def _send_changes_in_typing_to_remotes(
         self, room_id: str, prev_typing: Set[str], now_typing: Set[str]
-    ):
+    ) -> None:
         """Process a change in typing of a room from replication, sending EDUs
         for any local users.
         """
@@ -194,12 +194,12 @@ class FollowerTypingHandler:
             if self.is_mine_id(user_id):
                 await self._push_remote(RoomMember(room_id, user_id), False)
 
-    def get_current_token(self):
+    def get_current_token(self) -> int:
         return self._latest_room_serial
 
 
 class TypingWriterHandler(FollowerTypingHandler):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
         assert hs.config.worker.writers.typing == hs.get_instance_name()
@@ -213,14 +213,15 @@ class TypingWriterHandler(FollowerTypingHandler):
 
         hs.get_distributor().observe("user_left_room", self.user_left_room)
 
-        self._member_typing_until = {}  # clock time we expect to stop
+        # clock time we expect to stop
+        self._member_typing_until = {}  # type: Dict[RoomMember, int]
 
         # caches which room_ids changed at which serials
         self._typing_stream_change_cache = StreamChangeCache(
             "TypingStreamChangeCache", self._latest_room_serial
         )
 
-    def _handle_timeout_for_member(self, now: int, member: RoomMember):
+    def _handle_timeout_for_member(self, now: int, member: RoomMember) -> None:
         super()._handle_timeout_for_member(now, member)
 
         if not self.is_typing(member):
@@ -233,7 +234,9 @@ class TypingWriterHandler(FollowerTypingHandler):
             self._stopped_typing(member)
             return
 
-    async def started_typing(self, target_user, requester, room_id, timeout):
+    async def started_typing(
+        self, target_user: UserID, requester: Requester, room_id: str, timeout: int
+    ) -> None:
         target_user_id = target_user.to_string()
         auth_user_id = requester.user.to_string()
 
@@ -263,11 +266,13 @@ class TypingWriterHandler(FollowerTypingHandler):
 
         if was_present:
             # No point sending another notification
-            return None
+            return
 
         self._push_update(member=member, typing=True)
 
-    async def stopped_typing(self, target_user, requester, room_id):
+    async def stopped_typing(
+        self, target_user: UserID, requester: Requester, room_id: str
+    ) -> None:
         target_user_id = target_user.to_string()
         auth_user_id = requester.user.to_string()
 
@@ -290,23 +295,23 @@ class TypingWriterHandler(FollowerTypingHandler):
 
         self._stopped_typing(member)
 
-    def user_left_room(self, user, room_id):
+    def user_left_room(self, user: UserID, room_id: str) -> None:
         user_id = user.to_string()
         if self.is_mine_id(user_id):
             member = RoomMember(room_id=room_id, user_id=user_id)
             self._stopped_typing(member)
 
-    def _stopped_typing(self, member):
+    def _stopped_typing(self, member: RoomMember) -> None:
         if member.user_id not in self._room_typing.get(member.room_id, set()):
             # No point
-            return None
+            return
 
         self._member_typing_until.pop(member, None)
         self._member_last_federation_poke.pop(member, None)
 
         self._push_update(member=member, typing=False)
 
-    def _push_update(self, member, typing):
+    def _push_update(self, member: RoomMember, typing: bool) -> None:
         if self.hs.is_mine_id(member.user_id):
             # Only send updates for changes to our own users.
             run_as_background_process(
@@ -315,7 +320,7 @@ class TypingWriterHandler(FollowerTypingHandler):
 
         self._push_update_local(member=member, typing=typing)
 
-    async def _recv_edu(self, origin, content):
+    async def _recv_edu(self, origin: str, content: JsonDict) -> None:
         room_id = content["room_id"]
         user_id = content["user_id"]
 
@@ -340,7 +345,7 @@ class TypingWriterHandler(FollowerTypingHandler):
             self.wheel_timer.insert(now=now, obj=member, then=now + FEDERATION_TIMEOUT)
             self._push_update_local(member=member, typing=content["typing"])
 
-    def _push_update_local(self, member, typing):
+    def _push_update_local(self, member: RoomMember, typing: bool) -> None:
         room_set = self._room_typing.setdefault(member.room_id, set())
         if typing:
             room_set.add(member.user_id)
@@ -386,7 +391,7 @@ class TypingWriterHandler(FollowerTypingHandler):
 
         changed_rooms = self._typing_stream_change_cache.get_all_entities_changed(
             last_id
-        )
+        )  # type: Optional[Iterable[str]]
 
         if changed_rooms is None:
             changed_rooms = self._room_serials
@@ -412,13 +417,13 @@ class TypingWriterHandler(FollowerTypingHandler):
 
     def process_replication_rows(
         self, token: int, rows: List[TypingStream.TypingStreamRow]
-    ):
+    ) -> None:
         # The writing process should never get updates from replication.
         raise Exception("Typing writer instance got typing info over replication")
 
 
 class TypingNotificationEventSource:
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.clock = hs.get_clock()
         # We can't call get_typing_handler here because there's a cycle:
@@ -427,7 +432,7 @@ class TypingNotificationEventSource:
         #
         self.get_typing_handler = hs.get_typing_handler
 
-    def _make_event_for(self, room_id):
+    def _make_event_for(self, room_id: str) -> JsonDict:
         typing = self.get_typing_handler()._room_typing[room_id]
         return {
             "type": "m.typing",
@@ -462,7 +467,9 @@ class TypingNotificationEventSource:
 
             return (events, handler._latest_room_serial)
 
-    async def get_new_events(self, from_key, room_ids, **kwargs):
+    async def get_new_events(
+        self, from_key: int, room_ids: Iterable[str], **kwargs
+    ) -> Tuple[List[JsonDict], int]:
         with Measure(self.clock, "typing.get_new_events"):
             from_key = int(from_key)
             handler = self.get_typing_handler()
@@ -478,5 +485,5 @@ class TypingNotificationEventSource:
 
             return (events, handler._latest_room_serial)
 
-    def get_current_key(self):
+    def get_current_key(self) -> int:
         return self.get_typing_handler()._latest_room_serial
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index d4651c8348..8aedf5072e 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -145,10 +145,6 @@ class UserDirectoryHandler(StateDeltasHandler):
         if self.pos is None:
             self.pos = await self.store.get_user_directory_stream_pos()
 
-        # If still None then the initial background update hasn't happened yet
-        if self.pos is None:
-            return None
-
         # Loop round handling deltas until we're up to date
         while True:
             with Measure(self.clock, "user_dir_delta"):
@@ -233,6 +229,11 @@ class UserDirectoryHandler(StateDeltasHandler):
 
                     if change:  # The user joined
                         event = await self.store.get_event(event_id, allow_none=True)
+                        # It isn't expected for this event to not exist, but we
+                        # don't want the entire background process to break.
+                        if event is None:
+                            continue
+
                         profile = ProfileInfo(
                             avatar_url=event.content.get("avatar_url"),
                             display_name=event.content.get("displayname"),
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
deleted file mode 100644
index 92a5b606c8..0000000000
--- a/synapse/http/endpoint.py
+++ /dev/null
@@ -1,79 +0,0 @@
-# -*- coding: utf-8 -*-
-# Copyright 2014-2016 OpenMarket Ltd
-#
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-#
-#     http://www.apache.org/licenses/LICENSE-2.0
-#
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-import logging
-import re
-
-logger = logging.getLogger(__name__)
-
-
-def parse_server_name(server_name):
-    """Split a server name into host/port parts.
-
-    Args:
-        server_name (str): server name to parse
-
-    Returns:
-        Tuple[str, int|None]: host/port parts.
-
-    Raises:
-        ValueError if the server name could not be parsed.
-    """
-    try:
-        if server_name[-1] == "]":
-            # ipv6 literal, hopefully
-            return server_name, None
-
-        domain_port = server_name.rsplit(":", 1)
-        domain = domain_port[0]
-        port = int(domain_port[1]) if domain_port[1:] else None
-        return domain, port
-    except Exception:
-        raise ValueError("Invalid server name '%s'" % server_name)
-
-
-VALID_HOST_REGEX = re.compile("\\A[0-9a-zA-Z.-]+\\Z")
-
-
-def parse_and_validate_server_name(server_name):
-    """Split a server name into host/port parts and do some basic validation.
-
-    Args:
-        server_name (str): server name to parse
-
-    Returns:
-        Tuple[str, int|None]: host/port parts.
-
-    Raises:
-        ValueError if the server name could not be parsed.
-    """
-    host, port = parse_server_name(server_name)
-
-    # these tests don't need to be bulletproof as we'll find out soon enough
-    # if somebody is giving us invalid data. What we *do* need is to be sure
-    # that nobody is sneaking IP literals in that look like hostnames, etc.
-
-    # look for ipv6 literals
-    if host[0] == "[":
-        if host[-1] != "]":
-            raise ValueError("Mismatched [...] in server name '%s'" % (server_name,))
-        return host, port
-
-    # otherwise it should only be alphanumerics.
-    if not VALID_HOST_REGEX.match(host):
-        raise ValueError(
-            "Server name '%s' contains invalid characters" % (server_name,)
-        )
-
-    return host, port
diff --git a/synapse/http/server.py b/synapse/http/server.py
index e464bfe6c7..8249732b27 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -22,10 +22,22 @@ import types
 import urllib
 from http import HTTPStatus
 from io import BytesIO
-from typing import Any, Callable, Dict, Iterator, List, Tuple, Union
+from typing import (
+    Any,
+    Awaitable,
+    Callable,
+    Dict,
+    Iterable,
+    Iterator,
+    List,
+    Pattern,
+    Tuple,
+    Union,
+)
 
 import jinja2
 from canonicaljson import iterencode_canonical_json
+from typing_extensions import Protocol
 from zope.interface import implementer
 
 from twisted.internet import defer, interfaces
@@ -168,11 +180,25 @@ def wrap_async_request_handler(h):
     return preserve_fn(wrapped_async_request_handler)
 
 
-class HttpServer:
+# Type of a callback method for processing requests
+# it is actually called with a SynapseRequest and a kwargs dict for the params,
+# but I can't figure out how to represent that.
+ServletCallback = Callable[
+    ..., Union[None, Awaitable[None], Tuple[int, Any], Awaitable[Tuple[int, Any]]]
+]
+
+
+class HttpServer(Protocol):
     """ Interface for registering callbacks on a HTTP server
     """
 
-    def register_paths(self, method, path_patterns, callback):
+    def register_paths(
+        self,
+        method: str,
+        path_patterns: Iterable[Pattern],
+        callback: ServletCallback,
+        servlet_classname: str,
+    ) -> None:
         """ Register a callback that gets fired if we receive a http request
         with the given method for a path that matches the given regex.
 
@@ -180,12 +206,14 @@ class HttpServer:
         an unpacked tuple.
 
         Args:
-            method (str): The method to listen to.
-            path_patterns (list<SRE_Pattern>): The regex used to match requests.
-            callback (function): The function to fire if we receive a matched
+            method: The HTTP method to listen to.
+            path_patterns: The regex used to match requests.
+            callback: The function to fire if we receive a matched
                 request. The first argument will be the request object and
                 subsequent arguments will be any matched groups from the regex.
-                This should return a tuple of (code, response).
+                This should return either tuple of (code, response), or None.
+            servlet_classname (str): The name of the handler to be used in prometheus
+                and opentracing logs.
         """
         pass
 
@@ -354,7 +382,7 @@ class JsonResource(DirectServeJsonResource):
 
     def _get_handler_for_request(
         self, request: SynapseRequest
-    ) -> Tuple[Callable, str, Dict[str, str]]:
+    ) -> Tuple[ServletCallback, str, Dict[str, str]]:
         """Finds a callback method to handle the given request.
 
         Returns:
@@ -733,6 +761,13 @@ def set_clickjacking_protection_headers(request: Request):
     request.setHeader(b"Content-Security-Policy", b"frame-ancestors 'none';")
 
 
+def respond_with_redirect(request: Request, url: bytes) -> None:
+    """Write a 302 response to the request, if it is still alive."""
+    logger.debug("Redirect to %s", url.decode("utf-8"))
+    request.redirect(url)
+    finish_request(request)
+
+
 def finish_request(request: Request):
     """ Finish writing the response to the request.
 
diff --git a/synapse/logging/opentracing.py b/synapse/logging/opentracing.py
index ab586c318c..0538350f38 100644
--- a/synapse/logging/opentracing.py
+++ b/synapse/logging/opentracing.py
@@ -791,7 +791,7 @@ def tag_args(func):
 
     @wraps(func)
     def _tag_args_inner(*args, **kwargs):
-        argspec = inspect.getargspec(func)
+        argspec = inspect.getfullargspec(func)
         for i, arg in enumerate(argspec.args[1:]):
             set_tag("ARG_" + arg, args[i])
         set_tag("args", args[len(argspec.args) :])
diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index 72ab5750cc..401d577293 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -279,7 +279,11 @@ class ModuleApi:
         )
 
     async def complete_sso_login_async(
-        self, registered_user_id: str, request: SynapseRequest, client_redirect_url: str
+        self,
+        registered_user_id: str,
+        request: SynapseRequest,
+        client_redirect_url: str,
+        new_user: bool = False,
     ):
         """Complete a SSO login by redirecting the user to a page to confirm whether they
         want their access token sent to `client_redirect_url`, or redirect them to that
@@ -291,9 +295,11 @@ class ModuleApi:
             request: The request to respond to.
             client_redirect_url: The URL to which to offer to redirect the user (or to
                 redirect them directly if whitelisted).
+            new_user: set to true to use wording for the consent appropriate to a user
+                who has just registered.
         """
         await self._auth_handler.complete_sso_login(
-            registered_user_id, request, client_redirect_url,
+            registered_user_id, request, client_redirect_url, new_user=new_user
         )
 
     @defer.inlineCallbacks
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index 4d875dcb91..8a6dcff30d 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -267,9 +267,21 @@ class Mailer:
             fallback_to_members=True,
         )
 
-        summary_text = await self.make_summary_text(
-            notifs_by_room, state_by_room, notif_events, user_id, reason
-        )
+        if len(notifs_by_room) == 1:
+            # Only one room has new stuff
+            room_id = list(notifs_by_room.keys())[0]
+
+            summary_text = await self.make_summary_text_single_room(
+                room_id,
+                notifs_by_room[room_id],
+                state_by_room[room_id],
+                notif_events,
+                user_id,
+            )
+        else:
+            summary_text = await self.make_summary_text(
+                notifs_by_room, state_by_room, notif_events, reason
+            )
 
         template_vars = {
             "user_display_name": user_display_name,
@@ -492,139 +504,178 @@ class Mailer:
         if "url" in event.content:
             messagevars["image_url"] = event.content["url"]
 
-    async def make_summary_text(
+    async def make_summary_text_single_room(
         self,
-        notifs_by_room: Dict[str, List[Dict[str, Any]]],
-        room_state_ids: Dict[str, StateMap[str]],
+        room_id: str,
+        notifs: List[Dict[str, Any]],
+        room_state_ids: StateMap[str],
         notif_events: Dict[str, EventBase],
         user_id: str,
-        reason: Dict[str, Any],
-    ):
-        if len(notifs_by_room) == 1:
-            # Only one room has new stuff
-            room_id = list(notifs_by_room.keys())[0]
+    ) -> str:
+        """
+        Make a summary text for the email when only a single room has notifications.
 
-            # If the room has some kind of name, use it, but we don't
-            # want the generated-from-names one here otherwise we'll
-            # end up with, "new message from Bob in the Bob room"
-            room_name = await calculate_room_name(
-                self.store, room_state_ids[room_id], user_id, fallback_to_members=False
-            )
+        Args:
+            room_id: The ID of the room.
+            notifs: The notifications for this room.
+            room_state_ids: The state map for the room.
+            notif_events: A map of event ID -> notification event.
+            user_id: The user receiving the notification.
+
+        Returns:
+            The summary text.
+        """
+        # If the room has some kind of name, use it, but we don't
+        # want the generated-from-names one here otherwise we'll
+        # end up with, "new message from Bob in the Bob room"
+        room_name = await calculate_room_name(
+            self.store, room_state_ids, user_id, fallback_to_members=False
+        )
 
-            # See if one of the notifs is an invite event for the user
-            invite_event = None
-            for n in notifs_by_room[room_id]:
-                ev = notif_events[n["event_id"]]
-                if ev.type == EventTypes.Member and ev.state_key == user_id:
-                    if ev.content.get("membership") == Membership.INVITE:
-                        invite_event = ev
-                        break
-
-            if invite_event:
-                inviter_member_event_id = room_state_ids[room_id].get(
-                    ("m.room.member", invite_event.sender)
-                )
-                inviter_name = invite_event.sender
-                if inviter_member_event_id:
-                    inviter_member_event = await self.store.get_event(
-                        inviter_member_event_id, allow_none=True
-                    )
-                    if inviter_member_event:
-                        inviter_name = name_from_member_event(inviter_member_event)
-
-                if room_name is None:
-                    return self.email_subjects.invite_from_person % {
-                        "person": inviter_name,
-                        "app": self.app_name,
-                    }
-                else:
-                    return self.email_subjects.invite_from_person_to_room % {
-                        "person": inviter_name,
-                        "room": room_name,
-                        "app": self.app_name,
-                    }
+        # See if one of the notifs is an invite event for the user
+        invite_event = None
+        for n in notifs:
+            ev = notif_events[n["event_id"]]
+            if ev.type == EventTypes.Member and ev.state_key == user_id:
+                if ev.content.get("membership") == Membership.INVITE:
+                    invite_event = ev
+                    break
 
-            sender_name = None
-            if len(notifs_by_room[room_id]) == 1:
-                # There is just the one notification, so give some detail
-                event = notif_events[notifs_by_room[room_id][0]["event_id"]]
-                if ("m.room.member", event.sender) in room_state_ids[room_id]:
-                    state_event_id = room_state_ids[room_id][
-                        ("m.room.member", event.sender)
-                    ]
-                    state_event = await self.store.get_event(state_event_id)
-                    sender_name = name_from_member_event(state_event)
-
-                if sender_name is not None and room_name is not None:
-                    return self.email_subjects.message_from_person_in_room % {
-                        "person": sender_name,
-                        "room": room_name,
-                        "app": self.app_name,
-                    }
-                elif sender_name is not None:
-                    return self.email_subjects.message_from_person % {
-                        "person": sender_name,
-                        "app": self.app_name,
-                    }
-            else:
-                # There's more than one notification for this room, so just
-                # say there are several
-                if room_name is not None:
-                    return self.email_subjects.messages_in_room % {
-                        "room": room_name,
-                        "app": self.app_name,
-                    }
-                else:
-                    # If the room doesn't have a name, say who the messages
-                    # are from explicitly to avoid, "messages in the Bob room"
-                    sender_ids = list(
-                        {
-                            notif_events[n["event_id"]].sender
-                            for n in notifs_by_room[room_id]
-                        }
-                    )
-
-                    member_events = await self.store.get_events(
-                        [
-                            room_state_ids[room_id][("m.room.member", s)]
-                            for s in sender_ids
-                        ]
-                    )
-
-                    return self.email_subjects.messages_from_person % {
-                        "person": descriptor_from_member_events(member_events.values()),
-                        "app": self.app_name,
-                    }
-        else:
-            # Stuff's happened in multiple different rooms
+        if invite_event:
+            inviter_member_event_id = room_state_ids.get(
+                ("m.room.member", invite_event.sender)
+            )
+            inviter_name = invite_event.sender
+            if inviter_member_event_id:
+                inviter_member_event = await self.store.get_event(
+                    inviter_member_event_id, allow_none=True
+                )
+                if inviter_member_event:
+                    inviter_name = name_from_member_event(inviter_member_event)
 
-            # ...but we still refer to the 'reason' room which triggered the mail
-            if reason["room_name"] is not None:
-                return self.email_subjects.messages_in_room_and_others % {
-                    "room": reason["room_name"],
+            if room_name is None:
+                return self.email_subjects.invite_from_person % {
+                    "person": inviter_name,
                     "app": self.app_name,
                 }
-            else:
-                # If the reason room doesn't have a name, say who the messages
-                # are from explicitly to avoid, "messages in the Bob room"
-                room_id = reason["room_id"]
-
-                sender_ids = list(
-                    {
-                        notif_events[n["event_id"]].sender
-                        for n in notifs_by_room[room_id]
-                    }
-                )
 
-                member_events = await self.store.get_events(
-                    [room_state_ids[room_id][("m.room.member", s)] for s in sender_ids]
-                )
+            return self.email_subjects.invite_from_person_to_room % {
+                "person": inviter_name,
+                "room": room_name,
+                "app": self.app_name,
+            }
+
+        if len(notifs) == 1:
+            # There is just the one notification, so give some detail
+            sender_name = None
+            event = notif_events[notifs[0]["event_id"]]
+            if ("m.room.member", event.sender) in room_state_ids:
+                state_event_id = room_state_ids[("m.room.member", event.sender)]
+                state_event = await self.store.get_event(state_event_id)
+                sender_name = name_from_member_event(state_event)
+
+            if sender_name is not None and room_name is not None:
+                return self.email_subjects.message_from_person_in_room % {
+                    "person": sender_name,
+                    "room": room_name,
+                    "app": self.app_name,
+                }
+            elif sender_name is not None:
+                return self.email_subjects.message_from_person % {
+                    "person": sender_name,
+                    "app": self.app_name,
+                }
 
-                return self.email_subjects.messages_from_person_and_others % {
-                    "person": descriptor_from_member_events(member_events.values()),
+            # The sender is unknown, just use the room name (or ID).
+            return self.email_subjects.messages_in_room % {
+                "room": room_name or room_id,
+                "app": self.app_name,
+            }
+        else:
+            # There's more than one notification for this room, so just
+            # say there are several
+            if room_name is not None:
+                return self.email_subjects.messages_in_room % {
+                    "room": room_name,
                     "app": self.app_name,
                 }
 
+            return await self.make_summary_text_from_member_events(
+                room_id, notifs, room_state_ids, notif_events
+            )
+
+    async def make_summary_text(
+        self,
+        notifs_by_room: Dict[str, List[Dict[str, Any]]],
+        room_state_ids: Dict[str, StateMap[str]],
+        notif_events: Dict[str, EventBase],
+        reason: Dict[str, Any],
+    ) -> str:
+        """
+        Make a summary text for the email when multiple rooms have notifications.
+
+        Args:
+            notifs_by_room: A map of room ID to the notifications for that room.
+            room_state_ids: A map of room ID to the state map for that room.
+            notif_events: A map of event ID -> notification event.
+            reason: The reason this notification is being sent.
+
+        Returns:
+            The summary text.
+        """
+        # Stuff's happened in multiple different rooms
+        # ...but we still refer to the 'reason' room which triggered the mail
+        if reason["room_name"] is not None:
+            return self.email_subjects.messages_in_room_and_others % {
+                "room": reason["room_name"],
+                "app": self.app_name,
+            }
+
+        room_id = reason["room_id"]
+        return await self.make_summary_text_from_member_events(
+            room_id, notifs_by_room[room_id], room_state_ids[room_id], notif_events
+        )
+
+    async def make_summary_text_from_member_events(
+        self,
+        room_id: str,
+        notifs: List[Dict[str, Any]],
+        room_state_ids: StateMap[str],
+        notif_events: Dict[str, EventBase],
+    ) -> str:
+        """
+        Make a summary text for the email when only a single room has notifications.
+
+        Args:
+            room_id: The ID of the room.
+            notifs: The notifications for this room.
+            room_state_ids: The state map for the room.
+            notif_events: A map of event ID -> notification event.
+
+        Returns:
+            The summary text.
+        """
+        # If the room doesn't have a name, say who the messages
+        # are from explicitly to avoid, "messages in the Bob room"
+        sender_ids = {notif_events[n["event_id"]].sender for n in notifs}
+
+        member_events = await self.store.get_events(
+            [room_state_ids[("m.room.member", s)] for s in sender_ids]
+        )
+
+        # There was a single sender.
+        if len(sender_ids) == 1:
+            return self.email_subjects.messages_from_person % {
+                "person": descriptor_from_member_events(member_events.values()),
+                "app": self.app_name,
+            }
+
+        # There was more than one sender, use the first one and a tweaked template.
+        return self.email_subjects.messages_from_person_and_others % {
+            "person": descriptor_from_member_events(list(member_events.values())[:1]),
+            "app": self.app_name,
+        }
+
     def make_room_link(self, room_id: str) -> str:
         if self.hs.config.email_riot_base_url:
             base_url = "%s/#/room" % (self.hs.config.email_riot_base_url)
@@ -668,6 +719,15 @@ class Mailer:
 
 
 def safe_markup(raw_html: str) -> jinja2.Markup:
+    """
+    Sanitise a raw HTML string to a set of allowed tags and attributes, and linkify any bare URLs.
+
+    Args
+        raw_html: Unsafe HTML.
+
+    Returns:
+        A Markup object ready to safely use in a Jinja template.
+    """
     return jinja2.Markup(
         bleach.linkify(
             bleach.clean(
@@ -684,8 +744,13 @@ def safe_markup(raw_html: str) -> jinja2.Markup:
 
 def safe_text(raw_text: str) -> jinja2.Markup:
     """
-    Process text: treat it as HTML but escape any tags (ie. just escape the
-    HTML) then linkify it.
+    Sanitise text (escape any HTML tags), and then linkify any bare URLs.
+
+    Args
+        raw_text: Unsafe text which might include HTML markup.
+
+    Returns:
+        A Markup object ready to safely use in a Jinja template.
     """
     return jinja2.Markup(
         bleach.linkify(bleach.clean(raw_text, tags=[], attributes={}, strip=False))
diff --git a/synapse/push/presentable_names.py b/synapse/push/presentable_names.py
index 7e50341d74..04c2c1482c 100644
--- a/synapse/push/presentable_names.py
+++ b/synapse/push/presentable_names.py
@@ -17,7 +17,7 @@ import logging
 import re
 from typing import TYPE_CHECKING, Dict, Iterable, Optional
 
-from synapse.api.constants import EventTypes
+from synapse.api.constants import EventTypes, Membership
 from synapse.events import EventBase
 from synapse.types import StateMap
 
@@ -63,7 +63,7 @@ async def calculate_room_name(
         m_room_name = await store.get_event(
             room_state_ids[(EventTypes.Name, "")], allow_none=True
         )
-        if m_room_name and m_room_name.content and m_room_name.content["name"]:
+        if m_room_name and m_room_name.content and m_room_name.content.get("name"):
             return m_room_name.content["name"]
 
     # does it have a canonical alias?
@@ -74,15 +74,11 @@ async def calculate_room_name(
         if (
             canon_alias
             and canon_alias.content
-            and canon_alias.content["alias"]
+            and canon_alias.content.get("alias")
             and _looks_like_an_alias(canon_alias.content["alias"])
         ):
             return canon_alias.content["alias"]
 
-    # at this point we're going to need to search the state by all state keys
-    # for an event type, so rearrange the data structure
-    room_state_bytype_ids = _state_as_two_level_dict(room_state_ids)
-
     if not fallback_to_members:
         return None
 
@@ -94,7 +90,7 @@ async def calculate_room_name(
 
     if (
         my_member_event is not None
-        and my_member_event.content["membership"] == "invite"
+        and my_member_event.content.get("membership") == Membership.INVITE
     ):
         if (EventTypes.Member, my_member_event.sender) in room_state_ids:
             inviter_member_event = await store.get_event(
@@ -111,6 +107,10 @@ async def calculate_room_name(
         else:
             return "Room Invite"
 
+    # at this point we're going to need to search the state by all state keys
+    # for an event type, so rearrange the data structure
+    room_state_bytype_ids = _state_as_two_level_dict(room_state_ids)
+
     # we're going to have to generate a name based on who's in the room,
     # so find out who is in the room that isn't the user.
     if EventTypes.Member in room_state_bytype_ids:
@@ -120,8 +120,8 @@ async def calculate_room_name(
         all_members = [
             ev
             for ev in member_events.values()
-            if ev.content["membership"] == "join"
-            or ev.content["membership"] == "invite"
+            if ev.content.get("membership") == Membership.JOIN
+            or ev.content.get("membership") == Membership.INVITE
         ]
         # Sort the member events oldest-first so the we name people in the
         # order the joined (it should at least be deterministic rather than
@@ -194,11 +194,7 @@ def descriptor_from_member_events(member_events: Iterable[EventBase]) -> str:
 
 
 def name_from_member_event(member_event: EventBase) -> str:
-    if (
-        member_event.content
-        and "displayname" in member_event.content
-        and member_event.content["displayname"]
-    ):
+    if member_event.content and member_event.content.get("displayname"):
         return member_event.content["displayname"]
     return member_event.state_key
 
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index c97e0df1f5..bfd46a3730 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -86,8 +86,8 @@ REQUIREMENTS = [
 
 CONDITIONAL_REQUIREMENTS = {
     "matrix-synapse-ldap3": ["matrix-synapse-ldap3>=0.1"],
-    # we use execute_batch, which arrived in psycopg 2.7.
-    "postgres": ["psycopg2>=2.7"],
+    # we use execute_values with the fetch param, which arrived in psycopg 2.8.
+    "postgres": ["psycopg2>=2.8"],
     # ACME support is required to provision TLS certificates from authorities
     # that use the protocol, such as Let's Encrypt.
     "acme": [
diff --git a/synapse/replication/tcp/external_cache.py b/synapse/replication/tcp/external_cache.py
new file mode 100644
index 0000000000..34fa3ff5b3
--- /dev/null
+++ b/synapse/replication/tcp/external_cache.py
@@ -0,0 +1,105 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from typing import TYPE_CHECKING, Any, Optional
+
+from prometheus_client import Counter
+
+from synapse.logging.context import make_deferred_yieldable
+from synapse.util import json_decoder, json_encoder
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+set_counter = Counter(
+    "synapse_external_cache_set",
+    "Number of times we set a cache",
+    labelnames=["cache_name"],
+)
+
+get_counter = Counter(
+    "synapse_external_cache_get",
+    "Number of times we get a cache",
+    labelnames=["cache_name", "hit"],
+)
+
+
+logger = logging.getLogger(__name__)
+
+
+class ExternalCache:
+    """A cache backed by an external Redis. Does nothing if no Redis is
+    configured.
+    """
+
+    def __init__(self, hs: "HomeServer"):
+        self._redis_connection = hs.get_outbound_redis_connection()
+
+    def _get_redis_key(self, cache_name: str, key: str) -> str:
+        return "cache_v1:%s:%s" % (cache_name, key)
+
+    def is_enabled(self) -> bool:
+        """Whether the external cache is used or not.
+
+        It's safe to use the cache when this returns false, the methods will
+        just no-op, but the function is useful to avoid doing unnecessary work.
+        """
+        return self._redis_connection is not None
+
+    async def set(self, cache_name: str, key: str, value: Any, expiry_ms: int) -> None:
+        """Add the key/value to the named cache, with the expiry time given.
+        """
+
+        if self._redis_connection is None:
+            return
+
+        set_counter.labels(cache_name).inc()
+
+        # txredisapi requires the value to be string, bytes or numbers, so we
+        # encode stuff in JSON.
+        encoded_value = json_encoder.encode(value)
+
+        logger.debug("Caching %s %s: %r", cache_name, key, encoded_value)
+
+        return await make_deferred_yieldable(
+            self._redis_connection.set(
+                self._get_redis_key(cache_name, key), encoded_value, pexpire=expiry_ms,
+            )
+        )
+
+    async def get(self, cache_name: str, key: str) -> Optional[Any]:
+        """Look up a key/value in the named cache.
+        """
+
+        if self._redis_connection is None:
+            return None
+
+        result = await make_deferred_yieldable(
+            self._redis_connection.get(self._get_redis_key(cache_name, key))
+        )
+
+        logger.debug("Got cache result %s %s: %r", cache_name, key, result)
+
+        get_counter.labels(cache_name, result is not None).inc()
+
+        if not result:
+            return None
+
+        # For some reason the integers get magically converted back to integers
+        if isinstance(result, int):
+            return result
+
+        return json_decoder.decode(result)
diff --git a/synapse/replication/tcp/handler.py b/synapse/replication/tcp/handler.py
index 317796d5e0..8ea8dcd587 100644
--- a/synapse/replication/tcp/handler.py
+++ b/synapse/replication/tcp/handler.py
@@ -15,6 +15,7 @@
 # limitations under the License.
 import logging
 from typing import (
+    TYPE_CHECKING,
     Any,
     Awaitable,
     Dict,
@@ -63,6 +64,9 @@ from synapse.replication.tcp.streams import (
     TypingStream,
 )
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -88,7 +92,7 @@ class ReplicationCommandHandler:
     back out to connections.
     """
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self._replication_data_handler = hs.get_replication_data_handler()
         self._presence_handler = hs.get_presence_handler()
         self._store = hs.get_datastore()
@@ -282,13 +286,6 @@ class ReplicationCommandHandler:
         if hs.config.redis.redis_enabled:
             from synapse.replication.tcp.redis import (
                 RedisDirectTcpReplicationClientFactory,
-                lazyConnection,
-            )
-
-            logger.info(
-                "Connecting to redis (host=%r port=%r)",
-                hs.config.redis_host,
-                hs.config.redis_port,
             )
 
             # First let's ensure that we have a ReplicationStreamer started.
@@ -299,13 +296,7 @@ class ReplicationCommandHandler:
             # connection after SUBSCRIBE is called).
 
             # First create the connection for sending commands.
-            outbound_redis_connection = lazyConnection(
-                reactor=hs.get_reactor(),
-                host=hs.config.redis_host,
-                port=hs.config.redis_port,
-                password=hs.config.redis.redis_password,
-                reconnect=True,
-            )
+            outbound_redis_connection = hs.get_outbound_redis_connection()
 
             # Now create the factory/connection for the subscription stream.
             self._factory = RedisDirectTcpReplicationClientFactory(
diff --git a/synapse/replication/tcp/redis.py b/synapse/replication/tcp/redis.py
index bc6ba709a7..fdd087683b 100644
--- a/synapse/replication/tcp/redis.py
+++ b/synapse/replication/tcp/redis.py
@@ -15,7 +15,7 @@
 
 import logging
 from inspect import isawaitable
-from typing import TYPE_CHECKING, Optional
+from typing import TYPE_CHECKING, Optional, Type, cast
 
 import txredisapi
 
@@ -23,6 +23,7 @@ from synapse.logging.context import PreserveLoggingContext, make_deferred_yielda
 from synapse.metrics.background_process_metrics import (
     BackgroundProcessLoggingContext,
     run_as_background_process,
+    wrap_as_background_process,
 )
 from synapse.replication.tcp.commands import (
     Command,
@@ -59,16 +60,16 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
     immediately after initialisation.
 
     Attributes:
-        handler: The command handler to handle incoming commands.
-        stream_name: The *redis* stream name to subscribe to and publish from
-            (not anything to do with Synapse replication streams).
-        outbound_redis_connection: The connection to redis to use to send
+        synapse_handler: The command handler to handle incoming commands.
+        synapse_stream_name: The *redis* stream name to subscribe to and publish
+            from (not anything to do with Synapse replication streams).
+        synapse_outbound_redis_connection: The connection to redis to use to send
             commands.
     """
 
-    handler = None  # type: ReplicationCommandHandler
-    stream_name = None  # type: str
-    outbound_redis_connection = None  # type: txredisapi.RedisProtocol
+    synapse_handler = None  # type: ReplicationCommandHandler
+    synapse_stream_name = None  # type: str
+    synapse_outbound_redis_connection = None  # type: txredisapi.RedisProtocol
 
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
@@ -88,19 +89,19 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
         # it's important to make sure that we only send the REPLICATE command once we
         # have successfully subscribed to the stream - otherwise we might miss the
         # POSITION response sent back by the other end.
-        logger.info("Sending redis SUBSCRIBE for %s", self.stream_name)
-        await make_deferred_yieldable(self.subscribe(self.stream_name))
+        logger.info("Sending redis SUBSCRIBE for %s", self.synapse_stream_name)
+        await make_deferred_yieldable(self.subscribe(self.synapse_stream_name))
         logger.info(
             "Successfully subscribed to redis stream, sending REPLICATE command"
         )
-        self.handler.new_connection(self)
+        self.synapse_handler.new_connection(self)
         await self._async_send_command(ReplicateCommand())
         logger.info("REPLICATE successfully sent")
 
         # We send out our positions when there is a new connection in case the
         # other side missed updates. We do this for Redis connections as the
         # otherside won't know we've connected and so won't issue a REPLICATE.
-        self.handler.send_positions_to_connection(self)
+        self.synapse_handler.send_positions_to_connection(self)
 
     def messageReceived(self, pattern: str, channel: str, message: str):
         """Received a message from redis.
@@ -137,7 +138,7 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
             cmd: received command
         """
 
-        cmd_func = getattr(self.handler, "on_%s" % (cmd.NAME,), None)
+        cmd_func = getattr(self.synapse_handler, "on_%s" % (cmd.NAME,), None)
         if not cmd_func:
             logger.warning("Unhandled command: %r", cmd)
             return
@@ -155,7 +156,7 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
     def connectionLost(self, reason):
         logger.info("Lost connection to redis")
         super().connectionLost(reason)
-        self.handler.lost_connection(self)
+        self.synapse_handler.lost_connection(self)
 
         # mark the logging context as finished
         self._logging_context.__exit__(None, None, None)
@@ -183,11 +184,54 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
         tcp_outbound_commands_counter.labels(cmd.NAME, "redis").inc()
 
         await make_deferred_yieldable(
-            self.outbound_redis_connection.publish(self.stream_name, encoded_string)
+            self.synapse_outbound_redis_connection.publish(
+                self.synapse_stream_name, encoded_string
+            )
+        )
+
+
+class SynapseRedisFactory(txredisapi.RedisFactory):
+    """A subclass of RedisFactory that periodically sends pings to ensure that
+    we detect dead connections.
+    """
+
+    def __init__(
+        self,
+        hs: "HomeServer",
+        uuid: str,
+        dbid: Optional[int],
+        poolsize: int,
+        isLazy: bool = False,
+        handler: Type = txredisapi.ConnectionHandler,
+        charset: str = "utf-8",
+        password: Optional[str] = None,
+        replyTimeout: int = 30,
+        convertNumbers: Optional[int] = True,
+    ):
+        super().__init__(
+            uuid=uuid,
+            dbid=dbid,
+            poolsize=poolsize,
+            isLazy=isLazy,
+            handler=handler,
+            charset=charset,
+            password=password,
+            replyTimeout=replyTimeout,
+            convertNumbers=convertNumbers,
         )
 
+        hs.get_clock().looping_call(self._send_ping, 30 * 1000)
+
+    @wrap_as_background_process("redis_ping")
+    async def _send_ping(self):
+        for connection in self.pool:
+            try:
+                await make_deferred_yieldable(connection.ping())
+            except Exception:
+                logger.warning("Failed to send ping to a redis connection")
 
-class RedisDirectTcpReplicationClientFactory(txredisapi.SubscriberFactory):
+
+class RedisDirectTcpReplicationClientFactory(SynapseRedisFactory):
     """This is a reconnecting factory that connects to redis and immediately
     subscribes to a stream.
 
@@ -206,65 +250,62 @@ class RedisDirectTcpReplicationClientFactory(txredisapi.SubscriberFactory):
         self, hs: "HomeServer", outbound_redis_connection: txredisapi.RedisProtocol
     ):
 
-        super().__init__()
-
-        # This sets the password on the RedisFactory base class (as
-        # SubscriberFactory constructor doesn't pass it through).
-        self.password = hs.config.redis.redis_password
+        super().__init__(
+            hs,
+            uuid="subscriber",
+            dbid=None,
+            poolsize=1,
+            replyTimeout=30,
+            password=hs.config.redis.redis_password,
+        )
 
-        self.handler = hs.get_tcp_replication()
-        self.stream_name = hs.hostname
+        self.synapse_handler = hs.get_tcp_replication()
+        self.synapse_stream_name = hs.hostname
 
-        self.outbound_redis_connection = outbound_redis_connection
+        self.synapse_outbound_redis_connection = outbound_redis_connection
 
     def buildProtocol(self, addr):
-        p = super().buildProtocol(addr)  # type: RedisSubscriber
+        p = super().buildProtocol(addr)
+        p = cast(RedisSubscriber, p)
 
         # We do this here rather than add to the constructor of `RedisSubcriber`
         # as to do so would involve overriding `buildProtocol` entirely, however
         # the base method does some other things than just instantiating the
         # protocol.
-        p.handler = self.handler
-        p.outbound_redis_connection = self.outbound_redis_connection
-        p.stream_name = self.stream_name
-        p.password = self.password
+        p.synapse_handler = self.synapse_handler
+        p.synapse_outbound_redis_connection = self.synapse_outbound_redis_connection
+        p.synapse_stream_name = self.synapse_stream_name
 
         return p
 
 
 def lazyConnection(
-    reactor,
+    hs: "HomeServer",
     host: str = "localhost",
     port: int = 6379,
     dbid: Optional[int] = None,
     reconnect: bool = True,
-    charset: str = "utf-8",
     password: Optional[str] = None,
-    connectTimeout: Optional[int] = None,
-    replyTimeout: Optional[int] = None,
-    convertNumbers: bool = True,
+    replyTimeout: int = 30,
 ) -> txredisapi.RedisProtocol:
-    """Equivalent to `txredisapi.lazyConnection`, except allows specifying a
-    reactor.
+    """Creates a connection to Redis that is lazily set up and reconnects if the
+    connections is lost.
     """
 
-    isLazy = True
-    poolsize = 1
-
     uuid = "%s:%d" % (host, port)
-    factory = txredisapi.RedisFactory(
-        uuid,
-        dbid,
-        poolsize,
-        isLazy,
-        txredisapi.ConnectionHandler,
-        charset,
-        password,
-        replyTimeout,
-        convertNumbers,
+    factory = SynapseRedisFactory(
+        hs,
+        uuid=uuid,
+        dbid=dbid,
+        poolsize=1,
+        isLazy=True,
+        handler=txredisapi.ConnectionHandler,
+        password=password,
+        replyTimeout=replyTimeout,
     )
     factory.continueTrying = reconnect
-    for x in range(poolsize):
-        reactor.connectTCP(host, port, factory, connectTimeout)
+
+    reactor = hs.get_reactor()
+    reactor.connectTCP(host, port, factory, 30)
 
     return factory.handler
diff --git a/synapse/res/templates/sso.css b/synapse/res/templates/sso.css
new file mode 100644
index 0000000000..46b309ea4e
--- /dev/null
+++ b/synapse/res/templates/sso.css
@@ -0,0 +1,88 @@
+body {
+  font-family: "Inter", "Helvetica", "Arial", sans-serif;
+  font-size: 14px;
+  color: #17191C;
+}
+
+header {
+  max-width: 480px;
+  width: 100%;
+  margin: 24px auto;
+  text-align: center;
+}
+
+header p {
+  color: #737D8C;
+  line-height: 24px;
+}
+
+h1 {
+  font-size: 24px;
+}
+
+.error_page h1 {
+  color: #FE2928;
+}
+
+h2 {
+  font-size: 14px;
+}
+
+h2 img {
+  vertical-align: middle;
+  margin-right: 8px;
+  width: 24px;
+  height: 24px;
+}
+
+label {
+  cursor: pointer;
+}
+
+main {
+  max-width: 360px;
+  width: 100%;
+  margin: 24px auto;
+}
+
+.primary-button {
+  border: none;
+  text-decoration: none;
+  padding: 12px;
+  color: white;
+  background-color: #418DED;
+  font-weight: bold;
+  display: block;
+  border-radius: 12px;
+  width: 100%;
+  box-sizing: border-box;
+  margin: 16px 0;
+  cursor: pointer;
+  text-align: center;
+}
+
+.profile {
+  display: flex;
+  justify-content: center;
+  margin: 24px 0;
+}
+
+.profile .avatar {
+  width: 36px;
+  height: 36px;
+  border-radius: 100%;
+  display: block;
+  margin-right: 8px;
+}
+
+.profile .display-name {
+  font-weight: bold;
+  margin-bottom: 4px;
+}
+.profile .user-id {
+  color: #737D8C;
+}
+
+.profile .display-name, .profile .user-id {
+  line-height: 18px;
+}
diff --git a/synapse/res/templates/sso_account_deactivated.html b/synapse/res/templates/sso_account_deactivated.html
index 4eb8db9fb4..50a0979c2f 100644
--- a/synapse/res/templates/sso_account_deactivated.html
+++ b/synapse/res/templates/sso_account_deactivated.html
@@ -1,10 +1,24 @@
 <!DOCTYPE html>
 <html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <title>SSO account deactivated</title>
-</head>
-    <body>
-        <p>This account has been deactivated.</p>
+    <head>
+        <meta charset="UTF-8">
+        <title>SSO account deactivated</title>
+        <meta name="viewport" content="width=device-width, user-scalable=no">
+        <style type="text/css">
+            {% include "sso.css" without context %}
+        </style>
+    </head>
+    <body class="error_page">
+        <header>
+            <h1>Your account has been deactivated</h1>
+            <p>
+                <strong>No account found</strong>
+            </p>
+            <p>
+                Your account might have been deactivated by the server administrator.
+                You can either try to create a new account or contact the server’s
+                administrator.
+            </p>
+        </header>
     </body>
 </html>
diff --git a/synapse/res/templates/sso_auth_account_details.html b/synapse/res/templates/sso_auth_account_details.html
new file mode 100644
index 0000000000..105063825a
--- /dev/null
+++ b/synapse/res/templates/sso_auth_account_details.html
@@ -0,0 +1,138 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <title>Synapse Login</title>
+    <meta charset="utf-8">
+    <meta name="viewport" content="width=device-width, user-scalable=no">
+    <style type="text/css">
+      {% include "sso.css" without context %}
+
+      .username_input {
+        display: flex;
+        border: 2px solid #418DED;
+        border-radius: 8px;
+        padding: 12px;
+        position: relative;
+        margin: 16px 0;
+        align-items: center;
+        font-size: 12px;
+      }
+
+      .username_input label {
+        position: absolute;
+        top: -8px;
+        left: 14px;
+        font-size: 80%;
+        background: white;
+        padding: 2px;
+      }
+
+      .username_input input {
+        flex: 1;
+        display: block;
+        min-width: 0;
+        border: none;
+      }
+
+      .username_input div {
+        color: #8D99A5;
+      }
+
+      .idp-pick-details {
+        border: 1px solid #E9ECF1;
+        border-radius: 8px;
+        margin: 24px 0;
+      }
+
+      .idp-pick-details h2 {
+        margin: 0;
+        padding: 8px 12px;
+      }
+
+      .idp-pick-details .idp-detail {
+        border-top: 1px solid #E9ECF1;
+        padding: 12px;
+      }
+      .idp-pick-details .check-row {
+        display: flex;
+        align-items: center;
+      }
+
+      .idp-pick-details .check-row .name {
+        flex: 1;
+      }
+
+      .idp-pick-details .use, .idp-pick-details .idp-value {
+        color: #737D8C;
+      }
+
+      .idp-pick-details .idp-value {
+        margin: 0;
+        margin-top: 8px;
+      }
+
+      .idp-pick-details .avatar {
+        width: 53px;
+        height: 53px;
+        border-radius: 100%;
+        display: block;
+        margin-top: 8px;
+      }
+    </style>
+  </head>
+  <body>
+    <header>
+      <h1>Your account is nearly ready</h1>
+      <p>Check your details before creating an account on {{ server_name }}</p>
+    </header>
+    <main>
+      <form method="post" class="form__input" id="form">
+        <div class="username_input">
+          <label for="field-username">Username</label>
+          <div class="prefix">@</div>
+          <input type="text" name="username" id="field-username" autofocus required pattern="[a-z0-9\-=_\/\.]+">
+          <div class="postfix">:{{ server_name }}</div>
+        </div>
+        <input type="submit" value="Continue" class="primary-button">
+        {% if user_attributes %}
+        <section class="idp-pick-details">
+          <h2><img src="{{ idp.idp_icon | mxc_to_http(24, 24) }}"/>Information from {{ idp.idp_name }}</h2>
+          {% if user_attributes.avatar_url %}
+          <div class="idp-detail idp-avatar">
+            <div class="check-row">
+              <label for="idp-avatar" class="name">Avatar</label>
+              <label for="idp-avatar" class="use">Use</label>
+              <input type="checkbox" name="use_avatar" id="idp-avatar" value="true" checked>
+            </div>
+            <img src="{{ user_attributes.avatar_url }}" class="avatar" />
+          </div>
+          {% endif %}
+          {% if user_attributes.display_name %}
+          <div class="idp-detail">
+            <div class="check-row">
+              <label for="idp-displayname" class="name">Display name</label>
+              <label for="idp-displayname" class="use">Use</label>
+              <input type="checkbox" name="use_display_name" id="idp-displayname" value="true" checked>
+            </div>
+            <p class="idp-value">{{ user_attributes.display_name }}</p>
+          </div>
+          {% endif %}
+          {% for email in user_attributes.emails %}
+          <div class="idp-detail">
+            <div class="check-row">
+              <label for="idp-email{{ loop.index }}" class="name">E-mail</label>
+              <label for="idp-email{{ loop.index }}" class="use">Use</label>
+              <input type="checkbox" name="use_email" id="idp-email{{ loop.index }}" value="{{ email }}" checked>
+            </div>
+            <p class="idp-value">{{ email }}</p>
+          </div>
+          {% endfor %}
+        </section>
+        {% endif %}
+      </form>
+    </main>
+    <script type="text/javascript">
+      {% include "sso_auth_account_details.js" without context %}
+    </script>
+  </body>
+</html>
diff --git a/synapse/res/templates/sso_auth_account_details.js b/synapse/res/templates/sso_auth_account_details.js
new file mode 100644
index 0000000000..deef419bb6
--- /dev/null
+++ b/synapse/res/templates/sso_auth_account_details.js
@@ -0,0 +1,76 @@
+const usernameField = document.getElementById("field-username");
+
+function throttle(fn, wait) {
+    let timeout;
+    return function() {
+        const args = Array.from(arguments);
+        if (timeout) {
+            clearTimeout(timeout);
+        }
+        timeout = setTimeout(fn.bind.apply(fn, [null].concat(args)), wait);
+    }
+}
+
+function checkUsernameAvailable(username) {
+    let check_uri = 'check?username=' + encodeURIComponent(username);
+    return fetch(check_uri, {
+        // include the cookie
+        "credentials": "same-origin",
+    }).then((response) => {
+        if(!response.ok) {
+            // for non-200 responses, raise the body of the response as an exception
+            return response.text().then((text) => { throw new Error(text); });
+        } else {
+            return response.json();
+        }
+    }).then((json) => {
+        if(json.error) {
+            return {message: json.error};
+        } else if(json.available) {
+            return {available: true};
+        } else {
+            return {message: username + " is not available, please choose another."};
+        }
+    });
+}
+
+function validateUsername(username) {
+    usernameField.setCustomValidity("");
+    if (usernameField.validity.valueMissing) {
+        usernameField.setCustomValidity("Please provide a username");
+        return;
+    }
+    if (usernameField.validity.patternMismatch) {
+        usernameField.setCustomValidity("Invalid username, please only use " + allowedCharactersString);
+        return;
+    }
+    usernameField.setCustomValidity("Checking if username is available …");
+    throttledCheckUsernameAvailable(username);
+}
+
+const throttledCheckUsernameAvailable = throttle(function(username) {
+    const handleError =  function(err) {
+        // don't prevent form submission on error
+        usernameField.setCustomValidity("");
+        console.log(err.message);
+    };
+    try {
+        checkUsernameAvailable(username).then(function(result) {
+            if (!result.available) {
+                usernameField.setCustomValidity(result.message);
+                usernameField.reportValidity();
+            } else {
+                usernameField.setCustomValidity("");
+            }
+        }, handleError);
+    } catch (err) {
+        handleError(err);
+    }
+}, 500);
+
+usernameField.addEventListener("input", function(evt) {
+    validateUsername(usernameField.value);
+});
+usernameField.addEventListener("change", function(evt) {
+    validateUsername(usernameField.value);
+});
diff --git a/synapse/res/templates/sso_auth_bad_user.html b/synapse/res/templates/sso_auth_bad_user.html
index 3611191bf9..c9bd4bef20 100644
--- a/synapse/res/templates/sso_auth_bad_user.html
+++ b/synapse/res/templates/sso_auth_bad_user.html
@@ -1,18 +1,25 @@
-<html>
-<head>
-    <title>Authentication Failed</title>
-</head>
-    <body>
-        <div>
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8">
+        <title>Authentication failed</title>
+        <meta name="viewport" content="width=device-width, user-scalable=no">
+        <style type="text/css">
+            {% include "sso.css" without context %}
+        </style>
+    </head>
+    <body class="error_page">
+        <header>
+            <h1>That doesn't look right</h1>
             <p>
-                We were unable to validate your <tt>{{server_name | e}}</tt> account via
-                single-sign-on (SSO), because the SSO Identity Provider returned
-                different details than when you logged in.
+                <strong>We were unable to validate your {{ server_name }} account</strong>
+                via single&nbsp;sign&#8209;on&nbsp;(SSO), because the SSO Identity
+                Provider returned different details than when you logged in.
             </p>
             <p>
                 Try the operation again, and ensure that you use the same details on
                 the Identity Provider as when you log into your account.
             </p>
-        </div>
+        </header>
     </body>
 </html>
diff --git a/synapse/res/templates/sso_auth_confirm.html b/synapse/res/templates/sso_auth_confirm.html
index 0d9de9d465..2099c2f1f8 100644
--- a/synapse/res/templates/sso_auth_confirm.html
+++ b/synapse/res/templates/sso_auth_confirm.html
@@ -1,14 +1,28 @@
-<html>
-<head>
-    <title>Authentication</title>
-</head>
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8">
+        <title>Authentication</title>
+        <meta name="viewport" content="width=device-width, user-scalable=no">
+        <style type="text/css">
+            {% include "sso.css" without context %}
+        </style>
+    </head>
     <body>
-        <div>
+        <header>
+            <h1>Confirm it's you to continue</h1>
             <p>
-                A client is trying to {{ description | e }}. To confirm this action,
-                <a href="{{ redirect_url | e }}">re-authenticate with single sign-on</a>.
-                If you did not expect this, your account may be compromised!
+                A client is trying to {{ description }}. To confirm this action
+                re-authorize your account with single sign-on.
             </p>
-        </div>
+            <p><strong>
+                If you did not expect this, your account may be compromised.
+            </strong></p>
+        </header>
+        <main>
+            <a href="{{ redirect_url }}" class="primary-button">
+                Continue with {{ idp.idp_name }}
+            </a>
+        </main>
     </body>
 </html>
diff --git a/synapse/res/templates/sso_auth_success.html b/synapse/res/templates/sso_auth_success.html
index 03f1419467..3b975d7219 100644
--- a/synapse/res/templates/sso_auth_success.html
+++ b/synapse/res/templates/sso_auth_success.html
@@ -1,18 +1,27 @@
-<html>
-<head>
-    <title>Authentication Successful</title>
-    <script>
-    if (window.onAuthDone) {
-        window.onAuthDone();
-    } else if (window.opener && window.opener.postMessage) {
-        window.opener.postMessage("authDone", "*");
-    }
-    </script>
-</head>
+<!DOCTYPE html>
+<html lang="en">
+    <head>
+        <meta charset="UTF-8">
+        <title>Authentication successful</title>
+        <meta name="viewport" content="width=device-width, user-scalable=no">
+        <style type="text/css">
+            {% include "sso.css" without context %}
+        </style>
+        <script>
+            if (window.onAuthDone) {
+                window.onAuthDone();
+            } else if (window.opener && window.opener.postMessage) {
+                window.opener.postMessage("authDone", "*");
+            }
+        </script>
+    </head>
     <body>
-        <div>
-            <p>Thank you</p>
-            <p>You may now close this window and return to the application</p>
-        </div>
+        <header>
+            <h1>Thank you</h1>
+            <p>
+                Now we know it’s you, you can close this window and return to the
+                application.
+            </p>
+        </header>
     </body>
 </html>
diff --git a/synapse/res/templates/sso_error.html b/synapse/res/templates/sso_error.html
index 944bc9c9ca..b223ca0f56 100644
--- a/synapse/res/templates/sso_error.html
+++ b/synapse/res/templates/sso_error.html
@@ -1,53 +1,68 @@
 <!DOCTYPE html>
 <html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <title>SSO error</title>
-</head>
-<body>
+    <head>
+        <meta charset="UTF-8">
+        <title>Authentication failed</title>
+        <meta name="viewport" content="width=device-width, user-scalable=no">
+        <style type="text/css">
+            {% include "sso.css" without context %}
+
+            #error_code {
+                margin-top: 56px;
+            }
+        </style>
+    </head>
+    <body class="error_page">
 {# If an error of unauthorised is returned it means we have actively rejected their login #}
 {% if error == "unauthorised" %}
-    <p>You are not allowed to log in here.</p>
+        <header>
+            <p>You are not allowed to log in here.</p>
+        </header>
 {% else %}
-    <p>
-        There was an error during authentication:
-    </p>
-    <div id="errormsg" style="margin:20px 80px">{{ error_description | e }}</div>
-    <p>
-        If you are seeing this page after clicking a link sent to you via email, make
-        sure you only click the confirmation link once, and that you open the
-        validation link in the same client you're logging in from.
-    </p>
-    <p>
-        Try logging in again from your Matrix client and if the problem persists
-        please contact the server's administrator.
-    </p>
-    <p>Error: <code>{{ error }}</code></p>
+        <header>
+            <h1>There was an error</h1>
+            <p>
+                <strong id="errormsg">{{ error_description }}</strong>
+            </p>
+            <p>
+                If you are seeing this page after clicking a link sent to you via email,
+                make sure you only click the confirmation link once, and that you open
+                the validation link in the same client you're logging in from.
+            </p>
+            <p>
+                Try logging in again from your Matrix client and if the problem persists
+                please contact the server's administrator.
+            </p>
+            <div id="error_code">
+                <p><strong>Error code</strong></p>
+                <p>{{ error }}</p>
+            </div>
+        </header>
 
-    <script type="text/javascript">
-        // Error handling to support Auth0 errors that we might get through a GET request
-        // to the validation endpoint. If an error is provided, it's either going to be
-        // located in the query string or in a query string-like URI fragment.
-        // We try to locate the error from any of these two locations, but if we can't
-        // we just don't print anything specific.
-        let searchStr = "";
-        if (window.location.search) {
-            // window.location.searchParams isn't always defined when
-            // window.location.search is, so it's more reliable to parse the latter.
-            searchStr = window.location.search;
-        } else if (window.location.hash) {
-            // Replace the # with a ? so that URLSearchParams does the right thing and
-            // doesn't parse the first parameter incorrectly.
-            searchStr = window.location.hash.replace("#", "?");
-        }
+        <script type="text/javascript">
+            // Error handling to support Auth0 errors that we might get through a GET request
+            // to the validation endpoint. If an error is provided, it's either going to be
+            // located in the query string or in a query string-like URI fragment.
+            // We try to locate the error from any of these two locations, but if we can't
+            // we just don't print anything specific.
+            let searchStr = "";
+            if (window.location.search) {
+                // window.location.searchParams isn't always defined when
+                // window.location.search is, so it's more reliable to parse the latter.
+                searchStr = window.location.search;
+            } else if (window.location.hash) {
+                // Replace the # with a ? so that URLSearchParams does the right thing and
+                // doesn't parse the first parameter incorrectly.
+                searchStr = window.location.hash.replace("#", "?");
+            }
 
-        // We might end up with no error in the URL, so we need to check if we have one
-        // to print one.
-        let errorDesc = new URLSearchParams(searchStr).get("error_description")
-        if (errorDesc) {
-            document.getElementById("errormsg").innerText = errorDesc;
-        }
-    </script>
+            // We might end up with no error in the URL, so we need to check if we have one
+            // to print one.
+            let errorDesc = new URLSearchParams(searchStr).get("error_description")
+            if (errorDesc) {
+                document.getElementById("errormsg").innerText = errorDesc;
+            }
+        </script>
 {% endif %}
 </body>
 </html>
diff --git a/synapse/res/templates/sso_login_idp_picker.html b/synapse/res/templates/sso_login_idp_picker.html
index f53c9cd679..62a640dad2 100644
--- a/synapse/res/templates/sso_login_idp_picker.html
+++ b/synapse/res/templates/sso_login_idp_picker.html
@@ -3,20 +3,23 @@
     <head>
         <meta charset="UTF-8">
         <link rel="stylesheet" href="/_matrix/static/client/login/style.css">
-        <title>{{server_name | e}} Login</title>
+        <title>{{ server_name }} Login</title>
     </head>
     <body>
         <div id="container">
-            <h1 id="title">{{server_name | e}} Login</h1>
+            <h1 id="title">{{ server_name }} Login</h1>
             <div class="login_flow">
                 <p>Choose one of the following identity providers:</p>
             <form>
-                <input type="hidden" name="redirectUrl" value="{{redirect_url | e}}">
+                <input type="hidden" name="redirectUrl" value="{{ redirect_url }}">
                 <ul class="radiobuttons">
 {% for p in providers %}
                     <li>
-                        <input type="radio" name="idp" id="prov{{loop.index}}" value="{{p.idp_id}}">
-                        <label for="prov{{loop.index}}">{{p.idp_name | e}}</label>
+                        <input type="radio" name="idp" id="prov{{ loop.index }}" value="{{ p.idp_id }}">
+                        <label for="prov{{ loop.index }}">{{ p.idp_name }}</label>
+{% if p.idp_icon %}
+                        <img src="{{ p.idp_icon | mxc_to_http(32, 32) }}"/>
+{% endif %}
                     </li>
 {% endfor %}
                 </ul>
diff --git a/synapse/res/templates/sso_new_user_consent.html b/synapse/res/templates/sso_new_user_consent.html
new file mode 100644
index 0000000000..8c33787c54
--- /dev/null
+++ b/synapse/res/templates/sso_new_user_consent.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <title>SSO redirect confirmation</title>
+    <meta name="viewport" content="width=device-width, user-scalable=no">
+    <style type="text/css">
+      {% include "sso.css" without context %}
+
+      #consent_form {
+        margin-top: 56px;
+      }
+    </style>
+</head>
+    <body>
+        <header>
+            <h1>Your account is nearly ready</h1>
+            <p>Agree to the terms to create your account.</p>
+        </header>
+        <main>
+            <!-- {% if user_profile.avatar_url and user_profile.display_name %} -->
+            <div class="profile">
+                <img src="{{ user_profile.avatar_url | mxc_to_http(64, 64) }}" class="avatar" />
+                <div class="profile-details">
+                    <div class="display-name">{{ user_profile.display_name }}</div>
+                    <div class="user-id">{{ user_id }}</div>
+                </div>
+            </div>
+            <!-- {% endif %} -->
+            <form method="post" action="{{my_url}}" id="consent_form">
+                <p>
+                    <input id="accepted_version" type="checkbox" name="accepted_version" value="{{ consent_version }}" required>
+                    <label for="accepted_version">I have read and agree to the <a href="{{ terms_url }}" target="_blank">terms and conditions</a>.</label>
+                </p>
+                <input type="submit" class="primary-button" value="Continue"/>
+            </form>
+        </main>
+    </body>
+</html>
diff --git a/synapse/res/templates/sso_redirect_confirm.html b/synapse/res/templates/sso_redirect_confirm.html
index 20a15e1e74..d1328a6969 100644
--- a/synapse/res/templates/sso_redirect_confirm.html
+++ b/synapse/res/templates/sso_redirect_confirm.html
@@ -3,12 +3,34 @@
 <head>
     <meta charset="UTF-8">
     <title>SSO redirect confirmation</title>
+    <meta name="viewport" content="width=device-width, user-scalable=no">
+    <style type="text/css">
+      {% include "sso.css" without context %}
+    </style>
 </head>
     <body>
-        <p>The application at <span style="font-weight:bold">{{ display_url | e }}</span> is requesting full access to your <span style="font-weight:bold">{{ server_name }}</span> Matrix account.</p>
-        <p>If you don't recognise this address, you should ignore this and close this tab.</p>
-        <p>
-            <a href="{{ redirect_url | e }}">I trust this address</a>
-        </p>
+        <header>
+            {% if new_user %}
+            <h1>Your account is now ready</h1>
+            <p>You've made your account on {{ server_name }}.</p>
+            {% else %}
+            <h1>Log in</h1>
+            {% endif %}
+            <p>Continue to confirm you trust <strong>{{ display_url }}</strong>.</p>
+        </header>
+        <main>
+            {% if user_profile.avatar_url %}
+            <div class="profile">
+                <img src="{{ user_profile.avatar_url | mxc_to_http(64, 64) }}" class="avatar" />
+                <div class="profile-details">
+                    {% if user_profile.display_name %}
+                    <div class="display-name">{{ user_profile.display_name }}</div>
+                    {% endif %}
+                    <div class="user-id">{{ user_id }}</div>
+                </div>
+            </div>
+            {% endif %}
+            <a href="{{ redirect_url }}" class="primary-button">Continue</a>
+        </main>
     </body>
-</html>
\ No newline at end of file
+</html>
diff --git a/synapse/res/username_picker/index.html b/synapse/res/username_picker/index.html
deleted file mode 100644
index 37ea8bb6d8..0000000000
--- a/synapse/res/username_picker/index.html
+++ /dev/null
@@ -1,19 +0,0 @@
-<!DOCTYPE html>
-<html lang="en">
-  <head>
-    <title>Synapse Login</title>
-    <link rel="stylesheet" href="style.css" type="text/css" />
-  </head>
-  <body>
-    <div class="card">
-      <form method="post" class="form__input" id="form" action="submit">
-        <label for="field-username">Please pick your username:</label>
-        <input type="text" name="username" id="field-username" autofocus="">
-        <input type="submit" class="button button--full-width" id="button-submit" value="Submit">
-      </form>
-      <!-- this is used for feedback -->
-      <div role=alert class="tooltip hidden" id="message"></div>
-      <script src="script.js"></script>
-    </div>
-  </body>
-</html>
diff --git a/synapse/res/username_picker/script.js b/synapse/res/username_picker/script.js
deleted file mode 100644
index 416a7c6f41..0000000000
--- a/synapse/res/username_picker/script.js
+++ /dev/null
@@ -1,95 +0,0 @@
-let inputField = document.getElementById("field-username");
-let inputForm = document.getElementById("form");
-let submitButton = document.getElementById("button-submit");
-let message = document.getElementById("message");
-
-// Submit username and receive response
-function showMessage(messageText) {
-    // Unhide the message text
-    message.classList.remove("hidden");
-
-    message.textContent = messageText;
-};
-
-function doSubmit() {
-    showMessage("Success. Please wait a moment for your browser to redirect.");
-
-    // remove the event handler before re-submitting the form.
-    delete inputForm.onsubmit;
-    inputForm.submit();
-}
-
-function onResponse(response) {
-    // Display message
-    showMessage(response);
-
-    // Enable submit button and input field
-    submitButton.classList.remove('button--disabled');
-    submitButton.value = "Submit";
-};
-
-let allowedUsernameCharacters = RegExp("[^a-z0-9\\.\\_\\=\\-\\/]");
-function usernameIsValid(username) {
-    return !allowedUsernameCharacters.test(username);
-}
-let allowedCharactersString = "lowercase letters, digits, ., _, -, /, =";
-
-function buildQueryString(params) {
-    return Object.keys(params)
-        .map(k => encodeURIComponent(k) + '=' + encodeURIComponent(params[k]))
-        .join('&');
-}
-
-function submitUsername(username) {
-    if(username.length == 0) {
-        onResponse("Please enter a username.");
-        return;
-    }
-    if(!usernameIsValid(username)) {
-        onResponse("Invalid username. Only the following characters are allowed: " + allowedCharactersString);
-        return;
-    }
-
-    // if this browser doesn't support fetch, skip the availability check.
-    if(!window.fetch) {
-        doSubmit();
-        return;
-    }
-
-    let check_uri = 'check?' + buildQueryString({"username": username});
-    fetch(check_uri, {
-        // include the cookie
-        "credentials": "same-origin",
-    }).then((response) => {
-        if(!response.ok) {
-            // for non-200 responses, raise the body of the response as an exception
-            return response.text().then((text) => { throw text; });
-        } else {
-            return response.json();
-        }
-    }).then((json) => {
-        if(json.error) {
-            throw json.error;
-        } else if(json.available) {
-            doSubmit();
-        } else {
-            onResponse("This username is not available, please choose another.");
-        }
-    }).catch((err) => {
-        onResponse("Error checking username availability: " + err);
-    });
-}
-
-function clickSubmit() {
-    event.preventDefault();
-    if(submitButton.classList.contains('button--disabled')) { return; }
-
-    // Disable submit button and input field
-    submitButton.classList.add('button--disabled');
-
-    // Submit username
-    submitButton.value = "Checking...";
-    submitUsername(inputField.value);
-};
-
-inputForm.onsubmit = clickSubmit;
diff --git a/synapse/res/username_picker/style.css b/synapse/res/username_picker/style.css
deleted file mode 100644
index 745bd4c684..0000000000
--- a/synapse/res/username_picker/style.css
+++ /dev/null
@@ -1,27 +0,0 @@
-input[type="text"] {
-  font-size: 100%;
-  background-color: #ededf0;
-  border: 1px solid #fff;
-  border-radius: .2em;
-  padding: .5em .9em;
-  display: block;
-  width: 26em;
-}
-
-.button--disabled {
-  border-color: #fff;
-  background-color: transparent;
-  color: #000;
-  text-transform: none;
-}
-
-.hidden {
-  display: none;
-}
-
-.tooltip {
-  background-color: #f9f9fa;
-  padding: 1em;
-  margin: 1em 0;
-}
-
diff --git a/synapse/rest/admin/__init__.py b/synapse/rest/admin/__init__.py
index b7121c0c26..065e7c3e68 100644
--- a/synapse/rest/admin/__init__.py
+++ b/synapse/rest/admin/__init__.py
@@ -1,6 +1,8 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2018-2019 New Vector Ltd
+# Copyright 2020, 2021 The Matrix.org Foundation C.I.C.
+
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -40,11 +42,13 @@ from synapse.rest.admin.media import ListMediaInRoom, register_servlets_for_medi
 from synapse.rest.admin.purge_room_servlet import PurgeRoomServlet
 from synapse.rest.admin.rooms import (
     DeleteRoomRestServlet,
+    ForwardExtremitiesRestServlet,
     JoinRoomAliasServlet,
     ListRoomRestServlet,
     MakeRoomAdminRestServlet,
     RoomMembersRestServlet,
     RoomRestServlet,
+    RoomStateRestServlet,
     ShutdownRoomRestServlet,
 )
 from synapse.rest.admin.server_notice_servlet import SendServerNoticeServlet
@@ -55,6 +59,7 @@ from synapse.rest.admin.users import (
     PushersRestServlet,
     ResetPasswordRestServlet,
     SearchUsersRestServlet,
+    ShadowBanRestServlet,
     UserAdminServlet,
     UserMediaRestServlet,
     UserMembershipRestServlet,
@@ -213,6 +218,7 @@ def register_servlets(hs, http_server):
     """
     register_servlets_for_client_rest_resource(hs, http_server)
     ListRoomRestServlet(hs).register(http_server)
+    RoomStateRestServlet(hs).register(http_server)
     RoomRestServlet(hs).register(http_server)
     RoomMembersRestServlet(hs).register(http_server)
     DeleteRoomRestServlet(hs).register(http_server)
@@ -234,6 +240,8 @@ def register_servlets(hs, http_server):
     EventReportsRestServlet(hs).register(http_server)
     PushersRestServlet(hs).register(http_server)
     MakeRoomAdminRestServlet(hs).register(http_server)
+    ShadowBanRestServlet(hs).register(http_server)
+    ForwardExtremitiesRestServlet(hs).register(http_server)
 
 
 def register_servlets_for_client_rest_resource(hs, http_server):
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index ab7cc9102a..3e57e6a4d0 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Copyright 2019 The Matrix.org Foundation C.I.C.
+# Copyright 2019-2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -292,6 +292,45 @@ class RoomMembersRestServlet(RestServlet):
         return 200, ret
 
 
+class RoomStateRestServlet(RestServlet):
+    """
+    Get full state within a room.
+    """
+
+    PATTERNS = admin_patterns("/rooms/(?P<room_id>[^/]+)/state")
+
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self._event_serializer = hs.get_event_client_serializer()
+
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        ret = await self.store.get_room(room_id)
+        if not ret:
+            raise NotFoundError("Room not found")
+
+        event_ids = await self.store.get_current_state_ids(room_id)
+        events = await self.store.get_events(event_ids.values())
+        now = self.clock.time_msec()
+        room_state = await self._event_serializer.serialize_events(
+            events.values(),
+            now,
+            # We don't bother bundling aggregations in when asked for state
+            # events, as clients won't use them.
+            bundle_aggregations=False,
+        )
+        ret = {"state": room_state}
+
+        return 200, ret
+
+
 class JoinRoomAliasServlet(RestServlet):
 
     PATTERNS = admin_patterns("/join/(?P<room_identifier>[^/]*)")
@@ -431,7 +470,17 @@ class MakeRoomAdminRestServlet(RestServlet):
             if not admin_users:
                 raise SynapseError(400, "No local admin user in room")
 
-            admin_user_id = admin_users[-1]
+            admin_user_id = None
+
+            for admin_user in reversed(admin_users):
+                if room_state.get((EventTypes.Member, admin_user)):
+                    admin_user_id = admin_user
+                    break
+
+            if not admin_user_id:
+                raise SynapseError(
+                    400, "No local admin user in room",
+                )
 
             pl_content = power_levels.content
         else:
@@ -499,3 +548,60 @@ class MakeRoomAdminRestServlet(RestServlet):
         )
 
         return 200, {}
+
+
+class ForwardExtremitiesRestServlet(RestServlet):
+    """Allows a server admin to get or clear forward extremities.
+
+    Clearing does not require restarting the server.
+
+        Clear forward extremities:
+        DELETE /_synapse/admin/v1/rooms/<room_id_or_alias>/forward_extremities
+
+        Get forward_extremities:
+        GET /_synapse/admin/v1/rooms/<room_id_or_alias>/forward_extremities
+    """
+
+    PATTERNS = admin_patterns("/rooms/(?P<room_identifier>[^/]*)/forward_extremities")
+
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.room_member_handler = hs.get_room_member_handler()
+        self.store = hs.get_datastore()
+
+    async def resolve_room_id(self, room_identifier: str) -> str:
+        """Resolve to a room ID, if necessary."""
+        if RoomID.is_valid(room_identifier):
+            resolved_room_id = room_identifier
+        elif RoomAlias.is_valid(room_identifier):
+            room_alias = RoomAlias.from_string(room_identifier)
+            room_id, _ = await self.room_member_handler.lookup_room_alias(room_alias)
+            resolved_room_id = room_id.to_string()
+        else:
+            raise SynapseError(
+                400, "%s was not legal room ID or room alias" % (room_identifier,)
+            )
+        if not resolved_room_id:
+            raise SynapseError(
+                400, "Unknown room ID or room alias %s" % room_identifier
+            )
+        return resolved_room_id
+
+    async def on_DELETE(self, request, room_identifier):
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        room_id = await self.resolve_room_id(room_identifier)
+
+        deleted_count = await self.store.delete_forward_extremities_for_room(room_id)
+        return 200, {"deleted": deleted_count}
+
+    async def on_GET(self, request, room_identifier):
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        room_id = await self.resolve_room_id(room_identifier)
+
+        extremities = await self.store.get_forward_extremities_for_room(room_id)
+        return 200, {"count": len(extremities), "results": extremities}
diff --git a/synapse/rest/admin/users.py b/synapse/rest/admin/users.py
index f39e3d6d5c..68c3c64a0d 100644
--- a/synapse/rest/admin/users.py
+++ b/synapse/rest/admin/users.py
@@ -83,17 +83,32 @@ class UsersRestServletV2(RestServlet):
     The parameter `deactivated` can be used to include deactivated users.
     """
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         self.store = hs.get_datastore()
         self.auth = hs.get_auth()
         self.admin_handler = hs.get_admin_handler()
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         await assert_requester_is_admin(self.auth, request)
 
         start = parse_integer(request, "from", default=0)
         limit = parse_integer(request, "limit", default=100)
+
+        if start < 0:
+            raise SynapseError(
+                400,
+                "Query parameter from must be a string representing a positive integer.",
+                errcode=Codes.INVALID_PARAM,
+            )
+
+        if limit < 0:
+            raise SynapseError(
+                400,
+                "Query parameter limit must be a string representing a positive integer.",
+                errcode=Codes.INVALID_PARAM,
+            )
+
         user_id = parse_string(request, "user_id", default=None)
         name = parse_string(request, "name", default=None)
         guests = parse_boolean(request, "guests", default=True)
@@ -103,7 +118,7 @@ class UsersRestServletV2(RestServlet):
             start, limit, user_id, name, guests, deactivated
         )
         ret = {"users": users, "total": total}
-        if len(users) >= limit:
+        if (start + limit) < total:
             ret["next_token"] = str(start + len(users))
 
         return 200, ret
@@ -875,3 +890,39 @@ class UserTokenRestServlet(RestServlet):
         )
 
         return 200, {"access_token": token}
+
+
+class ShadowBanRestServlet(RestServlet):
+    """An admin API for shadow-banning a user.
+
+    A shadow-banned users receives successful responses to their client-server
+    API requests, but the events are not propagated into rooms.
+
+    Shadow-banning a user should be used as a tool of last resort and may lead
+    to confusing or broken behaviour for the client.
+
+    Example:
+
+        POST /_synapse/admin/v1/users/@test:example.com/shadow_ban
+        {}
+
+        200 OK
+        {}
+    """
+
+    PATTERNS = admin_patterns("/users/(?P<user_id>[^/]*)/shadow_ban")
+
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+        self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
+
+    async def on_POST(self, request, user_id):
+        await assert_requester_is_admin(self.auth, request)
+
+        if not self.hs.is_mine_id(user_id):
+            raise SynapseError(400, "Only local users can be shadow-banned")
+
+        await self.store.set_shadow_banned(UserID.from_string(user_id), True)
+
+        return 200, {}
diff --git a/synapse/rest/client/v1/login.py b/synapse/rest/client/v1/login.py
index be938df962..0fb9419e58 100644
--- a/synapse/rest/client/v1/login.py
+++ b/synapse/rest/client/v1/login.py
@@ -19,7 +19,8 @@ from typing import TYPE_CHECKING, Awaitable, Callable, Dict, Optional
 from synapse.api.errors import Codes, LoginError, SynapseError
 from synapse.api.ratelimiting import Ratelimiter
 from synapse.appservice import ApplicationService
-from synapse.http.server import finish_request
+from synapse.handlers.sso import SsoIdentityProvider
+from synapse.http.server import HttpServer, finish_request
 from synapse.http.servlet import (
     RestServlet,
     parse_json_object_from_request,
@@ -60,11 +61,14 @@ class LoginRestServlet(RestServlet):
         self.saml2_enabled = hs.config.saml2_enabled
         self.cas_enabled = hs.config.cas_enabled
         self.oidc_enabled = hs.config.oidc_enabled
+        self._msc2858_enabled = hs.config.experimental.msc2858_enabled
 
         self.auth = hs.get_auth()
 
         self.auth_handler = self.hs.get_auth_handler()
         self.registration_handler = hs.get_registration_handler()
+        self._sso_handler = hs.get_sso_handler()
+
         self._well_known_builder = WellKnownBuilder(hs)
         self._address_ratelimiter = Ratelimiter(
             clock=hs.get_clock(),
@@ -89,8 +93,17 @@ class LoginRestServlet(RestServlet):
             flows.append({"type": LoginRestServlet.CAS_TYPE})
 
         if self.cas_enabled or self.saml2_enabled or self.oidc_enabled:
-            flows.append({"type": LoginRestServlet.SSO_TYPE})
-            # While its valid for us to advertise this login type generally,
+            sso_flow = {"type": LoginRestServlet.SSO_TYPE}  # type: JsonDict
+
+            if self._msc2858_enabled:
+                sso_flow["org.matrix.msc2858.identity_providers"] = [
+                    _get_auth_flow_dict_for_idp(idp)
+                    for idp in self._sso_handler.get_identity_providers().values()
+                ]
+
+            flows.append(sso_flow)
+
+            # While it's valid for us to advertise this login type generally,
             # synapse currently only gives out these tokens as part of the
             # SSO login flow.
             # Generally we don't want to advertise login flows that clients
@@ -311,8 +324,22 @@ class LoginRestServlet(RestServlet):
         return result
 
 
+def _get_auth_flow_dict_for_idp(idp: SsoIdentityProvider) -> JsonDict:
+    """Return an entry for the login flow dict
+
+    Returns an entry suitable for inclusion in "identity_providers" in the
+    response to GET /_matrix/client/r0/login
+    """
+    e = {"id": idp.idp_id, "name": idp.idp_name}  # type: JsonDict
+    if idp.idp_icon:
+        e["icon"] = idp.idp_icon
+    if idp.idp_brand:
+        e["brand"] = idp.idp_brand
+    return e
+
+
 class SsoRedirectServlet(RestServlet):
-    PATTERNS = client_patterns("/login/(cas|sso)/redirect", v1=True)
+    PATTERNS = client_patterns("/login/(cas|sso)/redirect$", v1=True)
 
     def __init__(self, hs: "HomeServer"):
         # make sure that the relevant handlers are instantiated, so that they
@@ -324,13 +351,31 @@ class SsoRedirectServlet(RestServlet):
         if hs.config.oidc_enabled:
             hs.get_oidc_handler()
         self._sso_handler = hs.get_sso_handler()
+        self._msc2858_enabled = hs.config.experimental.msc2858_enabled
+
+    def register(self, http_server: HttpServer) -> None:
+        super().register(http_server)
+        if self._msc2858_enabled:
+            # expose additional endpoint for MSC2858 support
+            http_server.register_paths(
+                "GET",
+                client_patterns(
+                    "/org.matrix.msc2858/login/sso/redirect/(?P<idp_id>[A-Za-z0-9_.~-]+)$",
+                    releases=(),
+                    unstable=True,
+                ),
+                self.on_GET,
+                self.__class__.__name__,
+            )
 
-    async def on_GET(self, request: SynapseRequest):
+    async def on_GET(
+        self, request: SynapseRequest, idp_id: Optional[str] = None
+    ) -> None:
         client_redirect_url = parse_string(
             request, "redirectUrl", required=True, encoding=None
         )
         sso_url = await self._sso_handler.handle_redirect_request(
-            request, client_redirect_url
+            request, client_redirect_url, idp_id,
         )
         logger.info("Redirecting to %s", sso_url)
         request.redirect(sso_url)
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index e6725b03b0..f95627ee61 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -32,7 +32,6 @@ from synapse.api.errors import (
 )
 from synapse.api.filtering import Filter
 from synapse.events.utils import format_event_for_client_v2
-from synapse.http.endpoint import parse_and_validate_server_name
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
@@ -47,7 +46,7 @@ from synapse.storage.state import StateFilter
 from synapse.streams.config import PaginationConfig
 from synapse.types import RoomAlias, RoomID, StreamToken, ThirdPartyInstanceID, UserID
 from synapse.util import json_decoder
-from synapse.util.stringutils import random_string
+from synapse.util.stringutils import parse_and_validate_server_name, random_string
 
 if TYPE_CHECKING:
     import synapse.server
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index 65e68d641b..a84a2fb385 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -54,7 +54,7 @@ logger = logging.getLogger(__name__)
 class EmailPasswordRequestTokenRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/password/email/requestToken$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.datastore = hs.get_datastore()
@@ -103,6 +103,8 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
             # Raise if the provided next_link value isn't valid
             assert_valid_next_link(self.hs, next_link)
 
+        self.identity_handler.ratelimit_request_token_requests(request, "email", email)
+
         # The email will be sent to the stored address.
         # This avoids a potential account hijack by requesting a password reset to
         # an email address which is controlled by the attacker but which, after
@@ -379,6 +381,8 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
+        self.identity_handler.ratelimit_request_token_requests(request, "email", email)
+
         if next_link:
             # Raise if the provided next_link value isn't valid
             assert_valid_next_link(self.hs, next_link)
@@ -430,7 +434,7 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
 class MsisdnThreepidRequestTokenRestServlet(RestServlet):
     PATTERNS = client_patterns("/account/3pid/msisdn/requestToken$")
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.hs = hs
         super().__init__()
         self.store = self.hs.get_datastore()
@@ -458,6 +462,10 @@ class MsisdnThreepidRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
+        self.identity_handler.ratelimit_request_token_requests(
+            request, "msisdn", msisdn
+        )
+
         if next_link:
             # Raise if the provided next_link value isn't valid
             assert_valid_next_link(self.hs, next_link)
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index b093183e79..10e1891174 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -126,6 +126,8 @@ class EmailRegisterRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
+        self.identity_handler.ratelimit_request_token_requests(request, "email", email)
+
         existing_user_id = await self.hs.get_datastore().get_user_id_by_threepid(
             "email", email
         )
@@ -205,6 +207,10 @@ class MsisdnRegisterRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
+        self.identity_handler.ratelimit_request_token_requests(
+            request, "msisdn", msisdn
+        )
+
         existing_user_id = await self.hs.get_datastore().get_user_id_by_threepid(
             "msisdn", msisdn
         )
diff --git a/synapse/rest/consent/consent_resource.py b/synapse/rest/consent/consent_resource.py
index b3e4d5612e..8b9ef26cf2 100644
--- a/synapse/rest/consent/consent_resource.py
+++ b/synapse/rest/consent/consent_resource.py
@@ -100,6 +100,7 @@ class ConsentResource(DirectServeHtmlResource):
 
         consent_template_directory = hs.config.user_consent_template_dir
 
+        # TODO: switch to synapse.util.templates.build_jinja_env
         loader = jinja2.FileSystemLoader(consent_template_directory)
         self._jinja_env = jinja2.Environment(
             loader=loader, autoescape=jinja2.select_autoescape(["html", "htm", "xml"])
diff --git a/synapse/rest/media/v1/_base.py b/synapse/rest/media/v1/_base.py
index 31a41e4a27..f71a03a12d 100644
--- a/synapse/rest/media/v1/_base.py
+++ b/synapse/rest/media/v1/_base.py
@@ -300,6 +300,7 @@ class FileInfo:
         thumbnail_height (int)
         thumbnail_method (str)
         thumbnail_type (str): Content type of thumbnail, e.g. image/png
+        thumbnail_length (int): The size of the media file, in bytes.
     """
 
     def __init__(
@@ -312,6 +313,7 @@ class FileInfo:
         thumbnail_height=None,
         thumbnail_method=None,
         thumbnail_type=None,
+        thumbnail_length=None,
     ):
         self.server_name = server_name
         self.file_id = file_id
@@ -321,6 +323,7 @@ class FileInfo:
         self.thumbnail_height = thumbnail_height
         self.thumbnail_method = thumbnail_method
         self.thumbnail_type = thumbnail_type
+        self.thumbnail_length = thumbnail_length
 
 
 def get_filename_from_headers(headers: Dict[bytes, List[bytes]]) -> Optional[str]:
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index a632099167..bf3be653aa 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -386,7 +386,7 @@ class PreviewUrlResource(DirectServeJsonResource):
         """
         Check whether the URL should be downloaded as oEmbed content instead.
 
-        Params:
+        Args:
             url: The URL to check.
 
         Returns:
@@ -403,7 +403,7 @@ class PreviewUrlResource(DirectServeJsonResource):
         """
         Request content from an oEmbed endpoint.
 
-        Params:
+        Args:
             endpoint: The oEmbed API endpoint.
             url: The URL to pass to the API.
 
@@ -692,27 +692,51 @@ class PreviewUrlResource(DirectServeJsonResource):
 def decode_and_calc_og(
     body: bytes, media_uri: str, request_encoding: Optional[str] = None
 ) -> Dict[str, Optional[str]]:
+    """
+    Calculate metadata for an HTML document.
+
+    This uses lxml to parse the HTML document into the OG response. If errors
+    occur during processing of the document, an empty response is returned.
+
+    Args:
+        body: The HTML document, as bytes.
+        media_url: The URI used to download the body.
+        request_encoding: The character encoding of the body, as a string.
+
+    Returns:
+        The OG response as a dictionary.
+    """
     # If there's no body, nothing useful is going to be found.
     if not body:
         return {}
 
     from lxml import etree
 
+    # Create an HTML parser. If this fails, log and return no metadata.
     try:
         parser = etree.HTMLParser(recover=True, encoding=request_encoding)
-        tree = etree.fromstring(body, parser)
-        og = _calc_og(tree, media_uri)
+    except LookupError:
+        # blindly consider the encoding as utf-8.
+        parser = etree.HTMLParser(recover=True, encoding="utf-8")
+    except Exception as e:
+        logger.warning("Unable to create HTML parser: %s" % (e,))
+        return {}
+
+    def _attempt_calc_og(body_attempt: Union[bytes, str]) -> Dict[str, Optional[str]]:
+        # Attempt to parse the body. If this fails, log and return no metadata.
+        tree = etree.fromstring(body_attempt, parser)
+        return _calc_og(tree, media_uri)
+
+    # Attempt to parse the body. If this fails, log and return no metadata.
+    try:
+        return _attempt_calc_og(body)
     except UnicodeDecodeError:
         # blindly try decoding the body as utf-8, which seems to fix
         # the charset mismatches on https://google.com
-        parser = etree.HTMLParser(recover=True, encoding=request_encoding)
-        tree = etree.fromstring(body.decode("utf-8", "ignore"), parser)
-        og = _calc_og(tree, media_uri)
-
-    return og
+        return _attempt_calc_og(body.decode("utf-8", "ignore"))
 
 
-def _calc_og(tree, media_uri: str) -> Dict[str, Optional[str]]:
+def _calc_og(tree: "etree.Element", media_uri: str) -> Dict[str, Optional[str]]:
     # suck our tree into lxml and define our OG response.
 
     # if we see any image URLs in the OG response, then spider them
diff --git a/synapse/rest/media/v1/thumbnail_resource.py b/synapse/rest/media/v1/thumbnail_resource.py
index d6880f2e6e..d653a58be9 100644
--- a/synapse/rest/media/v1/thumbnail_resource.py
+++ b/synapse/rest/media/v1/thumbnail_resource.py
@@ -16,7 +16,7 @@
 
 
 import logging
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, Dict, List, Optional
 
 from twisted.web.http import Request
 
@@ -106,31 +106,17 @@ class ThumbnailResource(DirectServeJsonResource):
             return
 
         thumbnail_infos = await self.store.get_local_media_thumbnails(media_id)
-
-        if thumbnail_infos:
-            thumbnail_info = self._select_thumbnail(
-                width, height, method, m_type, thumbnail_infos
-            )
-
-            file_info = FileInfo(
-                server_name=None,
-                file_id=media_id,
-                url_cache=media_info["url_cache"],
-                thumbnail=True,
-                thumbnail_width=thumbnail_info["thumbnail_width"],
-                thumbnail_height=thumbnail_info["thumbnail_height"],
-                thumbnail_type=thumbnail_info["thumbnail_type"],
-                thumbnail_method=thumbnail_info["thumbnail_method"],
-            )
-
-            t_type = file_info.thumbnail_type
-            t_length = thumbnail_info["thumbnail_length"]
-
-            responder = await self.media_storage.fetch_media(file_info)
-            await respond_with_responder(request, responder, t_type, t_length)
-        else:
-            logger.info("Couldn't find any generated thumbnails")
-            respond_404(request)
+        await self._select_and_respond_with_thumbnail(
+            request,
+            width,
+            height,
+            method,
+            m_type,
+            thumbnail_infos,
+            media_id,
+            url_cache=media_info["url_cache"],
+            server_name=None,
+        )
 
     async def _select_or_generate_local_thumbnail(
         self,
@@ -276,26 +262,64 @@ class ThumbnailResource(DirectServeJsonResource):
         thumbnail_infos = await self.store.get_remote_media_thumbnails(
             server_name, media_id
         )
+        await self._select_and_respond_with_thumbnail(
+            request,
+            width,
+            height,
+            method,
+            m_type,
+            thumbnail_infos,
+            media_info["filesystem_id"],
+            url_cache=None,
+            server_name=server_name,
+        )
 
+    async def _select_and_respond_with_thumbnail(
+        self,
+        request: Request,
+        desired_width: int,
+        desired_height: int,
+        desired_method: str,
+        desired_type: str,
+        thumbnail_infos: List[Dict[str, Any]],
+        file_id: str,
+        url_cache: Optional[str] = None,
+        server_name: Optional[str] = None,
+    ) -> None:
+        """
+        Respond to a request with an appropriate thumbnail from the previously generated thumbnails.
+
+        Args:
+            request: The incoming request.
+            desired_width: The desired width, the returned thumbnail may be larger than this.
+            desired_height: The desired height, the returned thumbnail may be larger than this.
+            desired_method: The desired method used to generate the thumbnail.
+            desired_type: The desired content-type of the thumbnail.
+            thumbnail_infos: A list of dictionaries of candidate thumbnails.
+            file_id: The ID of the media that a thumbnail is being requested for.
+            url_cache: The URL cache value.
+            server_name: The server name, if this is a remote thumbnail.
+        """
         if thumbnail_infos:
-            thumbnail_info = self._select_thumbnail(
-                width, height, method, m_type, thumbnail_infos
+            file_info = self._select_thumbnail(
+                desired_width,
+                desired_height,
+                desired_method,
+                desired_type,
+                thumbnail_infos,
+                file_id,
+                url_cache,
+                server_name,
             )
-            file_info = FileInfo(
-                server_name=server_name,
-                file_id=media_info["filesystem_id"],
-                thumbnail=True,
-                thumbnail_width=thumbnail_info["thumbnail_width"],
-                thumbnail_height=thumbnail_info["thumbnail_height"],
-                thumbnail_type=thumbnail_info["thumbnail_type"],
-                thumbnail_method=thumbnail_info["thumbnail_method"],
-            )
-
-            t_type = file_info.thumbnail_type
-            t_length = thumbnail_info["thumbnail_length"]
+            if not file_info:
+                logger.info("Couldn't find a thumbnail matching the desired inputs")
+                respond_404(request)
+                return
 
             responder = await self.media_storage.fetch_media(file_info)
-            await respond_with_responder(request, responder, t_type, t_length)
+            await respond_with_responder(
+                request, responder, file_info.thumbnail_type, file_info.thumbnail_length
+            )
         else:
             logger.info("Failed to find any generated thumbnails")
             respond_404(request)
@@ -306,67 +330,117 @@ class ThumbnailResource(DirectServeJsonResource):
         desired_height: int,
         desired_method: str,
         desired_type: str,
-        thumbnail_infos,
-    ) -> dict:
+        thumbnail_infos: List[Dict[str, Any]],
+        file_id: str,
+        url_cache: Optional[str],
+        server_name: Optional[str],
+    ) -> Optional[FileInfo]:
+        """
+        Choose an appropriate thumbnail from the previously generated thumbnails.
+
+        Args:
+            desired_width: The desired width, the returned thumbnail may be larger than this.
+            desired_height: The desired height, the returned thumbnail may be larger than this.
+            desired_method: The desired method used to generate the thumbnail.
+            desired_type: The desired content-type of the thumbnail.
+            thumbnail_infos: A list of dictionaries of candidate thumbnails.
+            file_id: The ID of the media that a thumbnail is being requested for.
+            url_cache: The URL cache value.
+            server_name: The server name, if this is a remote thumbnail.
+
+        Returns:
+             The thumbnail which best matches the desired parameters.
+        """
+        desired_method = desired_method.lower()
+
+        # The chosen thumbnail.
+        thumbnail_info = None
+
         d_w = desired_width
         d_h = desired_height
 
-        if desired_method.lower() == "crop":
+        if desired_method == "crop":
+            # Thumbnails that match equal or larger sizes of desired width/height.
             crop_info_list = []
+            # Other thumbnails.
             crop_info_list2 = []
             for info in thumbnail_infos:
+                # Skip thumbnails generated with different methods.
+                if info["thumbnail_method"] != "crop":
+                    continue
+
                 t_w = info["thumbnail_width"]
                 t_h = info["thumbnail_height"]
-                t_method = info["thumbnail_method"]
-                if t_method == "crop":
-                    aspect_quality = abs(d_w * t_h - d_h * t_w)
-                    min_quality = 0 if d_w <= t_w and d_h <= t_h else 1
-                    size_quality = abs((d_w - t_w) * (d_h - t_h))
-                    type_quality = desired_type != info["thumbnail_type"]
-                    length_quality = info["thumbnail_length"]
-                    if t_w >= d_w or t_h >= d_h:
-                        crop_info_list.append(
-                            (
-                                aspect_quality,
-                                min_quality,
-                                size_quality,
-                                type_quality,
-                                length_quality,
-                                info,
-                            )
+                aspect_quality = abs(d_w * t_h - d_h * t_w)
+                min_quality = 0 if d_w <= t_w and d_h <= t_h else 1
+                size_quality = abs((d_w - t_w) * (d_h - t_h))
+                type_quality = desired_type != info["thumbnail_type"]
+                length_quality = info["thumbnail_length"]
+                if t_w >= d_w or t_h >= d_h:
+                    crop_info_list.append(
+                        (
+                            aspect_quality,
+                            min_quality,
+                            size_quality,
+                            type_quality,
+                            length_quality,
+                            info,
                         )
-                    else:
-                        crop_info_list2.append(
-                            (
-                                aspect_quality,
-                                min_quality,
-                                size_quality,
-                                type_quality,
-                                length_quality,
-                                info,
-                            )
+                    )
+                else:
+                    crop_info_list2.append(
+                        (
+                            aspect_quality,
+                            min_quality,
+                            size_quality,
+                            type_quality,
+                            length_quality,
+                            info,
                         )
+                    )
             if crop_info_list:
-                return min(crop_info_list)[-1]
-            else:
-                return min(crop_info_list2)[-1]
-        else:
+                thumbnail_info = min(crop_info_list)[-1]
+            elif crop_info_list2:
+                thumbnail_info = min(crop_info_list2)[-1]
+        elif desired_method == "scale":
+            # Thumbnails that match equal or larger sizes of desired width/height.
             info_list = []
+            # Other thumbnails.
             info_list2 = []
+
             for info in thumbnail_infos:
+                # Skip thumbnails generated with different methods.
+                if info["thumbnail_method"] != "scale":
+                    continue
+
                 t_w = info["thumbnail_width"]
                 t_h = info["thumbnail_height"]
-                t_method = info["thumbnail_method"]
                 size_quality = abs((d_w - t_w) * (d_h - t_h))
                 type_quality = desired_type != info["thumbnail_type"]
                 length_quality = info["thumbnail_length"]
-                if t_method == "scale" and (t_w >= d_w or t_h >= d_h):
+                if t_w >= d_w or t_h >= d_h:
                     info_list.append((size_quality, type_quality, length_quality, info))
-                elif t_method == "scale":
+                else:
                     info_list2.append(
                         (size_quality, type_quality, length_quality, info)
                     )
             if info_list:
-                return min(info_list)[-1]
-            else:
-                return min(info_list2)[-1]
+                thumbnail_info = min(info_list)[-1]
+            elif info_list2:
+                thumbnail_info = min(info_list2)[-1]
+
+        if thumbnail_info:
+            return FileInfo(
+                file_id=file_id,
+                url_cache=url_cache,
+                server_name=server_name,
+                thumbnail=True,
+                thumbnail_width=thumbnail_info["thumbnail_width"],
+                thumbnail_height=thumbnail_info["thumbnail_height"],
+                thumbnail_type=thumbnail_info["thumbnail_type"],
+                thumbnail_method=thumbnail_info["thumbnail_method"],
+                thumbnail_length=thumbnail_info["thumbnail_length"],
+            )
+
+        # No matching thumbnail was found.
+        return None
diff --git a/synapse/rest/synapse/client/__init__.py b/synapse/rest/synapse/client/__init__.py
index c0b733488b..e5ef515090 100644
--- a/synapse/rest/synapse/client/__init__.py
+++ b/synapse/rest/synapse/client/__init__.py
@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# Copyright 2020 The Matrix.org Foundation C.I.C.
+# Copyright 2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -12,3 +12,55 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
+from typing import TYPE_CHECKING, Mapping
+
+from twisted.web.resource import Resource
+
+from synapse.rest.synapse.client.new_user_consent import NewUserConsentResource
+from synapse.rest.synapse.client.pick_idp import PickIdpResource
+from synapse.rest.synapse.client.pick_username import pick_username_resource
+from synapse.rest.synapse.client.sso_register import SsoRegisterResource
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+
+def build_synapse_client_resource_tree(hs: "HomeServer") -> Mapping[str, Resource]:
+    """Builds a resource tree to include synapse-specific client resources
+
+    These are resources which should be loaded on all workers which expose a C-S API:
+    ie, the main process, and any generic workers so configured.
+
+    Returns:
+         map from path to Resource.
+    """
+    resources = {
+        # SSO bits. These are always loaded, whether or not SSO login is actually
+        # enabled (they just won't work very well if it's not)
+        "/_synapse/client/pick_idp": PickIdpResource(hs),
+        "/_synapse/client/pick_username": pick_username_resource(hs),
+        "/_synapse/client/new_user_consent": NewUserConsentResource(hs),
+        "/_synapse/client/sso_register": SsoRegisterResource(hs),
+    }
+
+    # provider-specific SSO bits. Only load these if they are enabled, since they
+    # rely on optional dependencies.
+    if hs.config.oidc_enabled:
+        from synapse.rest.synapse.client.oidc import OIDCResource
+
+        resources["/_synapse/client/oidc"] = OIDCResource(hs)
+
+    if hs.config.saml2_enabled:
+        from synapse.rest.synapse.client.saml2 import SAML2Resource
+
+        res = SAML2Resource(hs)
+        resources["/_synapse/client/saml2"] = res
+
+        # This is also mounted under '/_matrix' for backwards-compatibility.
+        resources["/_matrix/saml2"] = res
+
+    return resources
+
+
+__all__ = ["build_synapse_client_resource_tree"]
diff --git a/synapse/rest/synapse/client/new_user_consent.py b/synapse/rest/synapse/client/new_user_consent.py
new file mode 100644
index 0000000000..b2e0f93810
--- /dev/null
+++ b/synapse/rest/synapse/client/new_user_consent.py
@@ -0,0 +1,97 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+from typing import TYPE_CHECKING
+
+from twisted.web.http import Request
+
+from synapse.api.errors import SynapseError
+from synapse.handlers.sso import get_username_mapping_session_cookie_from_request
+from synapse.http.server import DirectServeHtmlResource, respond_with_html
+from synapse.http.servlet import parse_string
+from synapse.types import UserID
+from synapse.util.templates import build_jinja_env
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class NewUserConsentResource(DirectServeHtmlResource):
+    """A resource which collects consent to the server's terms from a new user
+
+    This resource gets mounted at /_synapse/client/new_user_consent, and is shown
+    when we are automatically creating a new user due to an SSO login.
+
+    It shows a template which prompts the user to go and read the Ts and Cs, and click
+    a clickybox if they have done so.
+    """
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self._sso_handler = hs.get_sso_handler()
+        self._server_name = hs.hostname
+        self._consent_version = hs.config.consent.user_consent_version
+
+        def template_search_dirs():
+            if hs.config.sso.sso_template_dir:
+                yield hs.config.sso.sso_template_dir
+            yield hs.config.sso.default_template_dir
+
+        self._jinja_env = build_jinja_env(template_search_dirs(), hs.config)
+
+    async def _async_render_GET(self, request: Request) -> None:
+        try:
+            session_id = get_username_mapping_session_cookie_from_request(request)
+            session = self._sso_handler.get_mapping_session(session_id)
+        except SynapseError as e:
+            logger.warning("Error fetching session: %s", e)
+            self._sso_handler.render_error(request, "bad_session", e.msg, code=e.code)
+            return
+
+        user_id = UserID(session.chosen_localpart, self._server_name)
+        user_profile = {
+            "display_name": session.display_name,
+        }
+
+        template_params = {
+            "user_id": user_id.to_string(),
+            "user_profile": user_profile,
+            "consent_version": self._consent_version,
+            "terms_url": "/_matrix/consent?v=%s" % (self._consent_version,),
+        }
+
+        template = self._jinja_env.get_template("sso_new_user_consent.html")
+        html = template.render(template_params)
+        respond_with_html(request, 200, html)
+
+    async def _async_render_POST(self, request: Request):
+        try:
+            session_id = get_username_mapping_session_cookie_from_request(request)
+        except SynapseError as e:
+            logger.warning("Error fetching session cookie: %s", e)
+            self._sso_handler.render_error(request, "bad_session", e.msg, code=e.code)
+            return
+
+        try:
+            accepted_version = parse_string(request, "accepted_version", required=True)
+        except SynapseError as e:
+            self._sso_handler.render_error(request, "bad_param", e.msg, code=e.code)
+            return
+
+        await self._sso_handler.handle_terms_accepted(
+            request, session_id, accepted_version
+        )
diff --git a/synapse/rest/oidc/__init__.py b/synapse/rest/synapse/client/oidc/__init__.py
index d958dd65bb..64c0deb75d 100644
--- a/synapse/rest/oidc/__init__.py
+++ b/synapse/rest/synapse/client/oidc/__init__.py
@@ -12,11 +12,12 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 import logging
 
 from twisted.web.resource import Resource
 
-from synapse.rest.oidc.callback_resource import OIDCCallbackResource
+from synapse.rest.synapse.client.oidc.callback_resource import OIDCCallbackResource
 
 logger = logging.getLogger(__name__)
 
@@ -25,3 +26,6 @@ class OIDCResource(Resource):
     def __init__(self, hs):
         Resource.__init__(self)
         self.putChild(b"callback", OIDCCallbackResource(hs))
+
+
+__all__ = ["OIDCResource"]
diff --git a/synapse/rest/oidc/callback_resource.py b/synapse/rest/synapse/client/oidc/callback_resource.py
index f7a0bc4bdb..f7a0bc4bdb 100644
--- a/synapse/rest/oidc/callback_resource.py
+++ b/synapse/rest/synapse/client/oidc/callback_resource.py
diff --git a/synapse/rest/synapse/client/pick_username.py b/synapse/rest/synapse/client/pick_username.py
index d3b6803e65..96077cfcd1 100644
--- a/synapse/rest/synapse/client/pick_username.py
+++ b/synapse/rest/synapse/client/pick_username.py
@@ -12,42 +12,42 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from typing import TYPE_CHECKING
 
-import pkg_resources
+import logging
+from typing import TYPE_CHECKING, List
 
 from twisted.web.http import Request
 from twisted.web.resource import Resource
-from twisted.web.static import File
 
 from synapse.api.errors import SynapseError
-from synapse.handlers.sso import USERNAME_MAPPING_SESSION_COOKIE_NAME
-from synapse.http.server import DirectServeHtmlResource, DirectServeJsonResource
-from synapse.http.servlet import parse_string
+from synapse.handlers.sso import get_username_mapping_session_cookie_from_request
+from synapse.http.server import (
+    DirectServeHtmlResource,
+    DirectServeJsonResource,
+    respond_with_html,
+)
+from synapse.http.servlet import parse_boolean, parse_string
 from synapse.http.site import SynapseRequest
+from synapse.util.templates import build_jinja_env
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
+logger = logging.getLogger(__name__)
+
 
 def pick_username_resource(hs: "HomeServer") -> Resource:
     """Factory method to generate the username picker resource.
 
-    This resource gets mounted under /_synapse/client/pick_username. The top-level
-    resource is just a File resource which serves up the static files in the resources
-    "res" directory, but it has a couple of children:
-
-    * "submit", which does the mechanics of registering the new user, and redirects the
-      browser back to the client URL
+    This resource gets mounted under /_synapse/client/pick_username and has two
+       children:
 
-    * "check": checks if a userid is free.
+      * "account_details": renders the form and handles the POSTed response
+      * "check": a JSON endpoint which checks if a userid is free.
     """
 
-    # XXX should we make this path customisable so that admins can restyle it?
-    base_path = pkg_resources.resource_filename("synapse", "res/username_picker")
-
-    res = File(base_path)
-    res.putChild(b"submit", SubmitResource(hs))
+    res = Resource()
+    res.putChild(b"account_details", AccountDetailsResource(hs))
     res.putChild(b"check", AvailabilityCheckResource(hs))
 
     return res
@@ -61,28 +61,71 @@ class AvailabilityCheckResource(DirectServeJsonResource):
     async def _async_render_GET(self, request: Request):
         localpart = parse_string(request, "username", required=True)
 
-        session_id = request.getCookie(USERNAME_MAPPING_SESSION_COOKIE_NAME)
-        if not session_id:
-            raise SynapseError(code=400, msg="missing session_id")
+        session_id = get_username_mapping_session_cookie_from_request(request)
 
         is_available = await self._sso_handler.check_username_availability(
-            localpart, session_id.decode("ascii", errors="replace")
+            localpart, session_id
         )
         return 200, {"available": is_available}
 
 
-class SubmitResource(DirectServeHtmlResource):
+class AccountDetailsResource(DirectServeHtmlResource):
     def __init__(self, hs: "HomeServer"):
         super().__init__()
         self._sso_handler = hs.get_sso_handler()
 
-    async def _async_render_POST(self, request: SynapseRequest):
-        localpart = parse_string(request, "username", required=True)
+        def template_search_dirs():
+            if hs.config.sso.sso_template_dir:
+                yield hs.config.sso.sso_template_dir
+            yield hs.config.sso.default_template_dir
+
+        self._jinja_env = build_jinja_env(template_search_dirs(), hs.config)
+
+    async def _async_render_GET(self, request: Request) -> None:
+        try:
+            session_id = get_username_mapping_session_cookie_from_request(request)
+            session = self._sso_handler.get_mapping_session(session_id)
+        except SynapseError as e:
+            logger.warning("Error fetching session: %s", e)
+            self._sso_handler.render_error(request, "bad_session", e.msg, code=e.code)
+            return
+
+        idp_id = session.auth_provider_id
+        template_params = {
+            "idp": self._sso_handler.get_identity_providers()[idp_id],
+            "user_attributes": {
+                "display_name": session.display_name,
+                "emails": session.emails,
+            },
+        }
+
+        template = self._jinja_env.get_template("sso_auth_account_details.html")
+        html = template.render(template_params)
+        respond_with_html(request, 200, html)
 
-        session_id = request.getCookie(USERNAME_MAPPING_SESSION_COOKIE_NAME)
-        if not session_id:
-            raise SynapseError(code=400, msg="missing session_id")
+    async def _async_render_POST(self, request: SynapseRequest):
+        try:
+            session_id = get_username_mapping_session_cookie_from_request(request)
+        except SynapseError as e:
+            logger.warning("Error fetching session cookie: %s", e)
+            self._sso_handler.render_error(request, "bad_session", e.msg, code=e.code)
+            return
+
+        try:
+            localpart = parse_string(request, "username", required=True)
+            use_display_name = parse_boolean(request, "use_display_name", default=False)
+
+            try:
+                emails_to_use = [
+                    val.decode("utf-8") for val in request.args.get(b"use_email", [])
+                ]  # type: List[str]
+            except ValueError:
+                raise SynapseError(400, "Query parameter use_email must be utf-8")
+        except SynapseError as e:
+            logger.warning("[session %s] bad param: %s", session_id, e)
+            self._sso_handler.render_error(request, "bad_param", e.msg, code=e.code)
+            return
 
         await self._sso_handler.handle_submit_username_request(
-            request, localpart, session_id.decode("ascii", errors="replace")
+            request, session_id, localpart, use_display_name, emails_to_use
         )
diff --git a/synapse/rest/saml2/__init__.py b/synapse/rest/synapse/client/saml2/__init__.py
index 68da37ca6a..3e8235ee1e 100644
--- a/synapse/rest/saml2/__init__.py
+++ b/synapse/rest/synapse/client/saml2/__init__.py
@@ -12,12 +12,13 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 import logging
 
 from twisted.web.resource import Resource
 
-from synapse.rest.saml2.metadata_resource import SAML2MetadataResource
-from synapse.rest.saml2.response_resource import SAML2ResponseResource
+from synapse.rest.synapse.client.saml2.metadata_resource import SAML2MetadataResource
+from synapse.rest.synapse.client.saml2.response_resource import SAML2ResponseResource
 
 logger = logging.getLogger(__name__)
 
@@ -27,3 +28,6 @@ class SAML2Resource(Resource):
         Resource.__init__(self)
         self.putChild(b"metadata.xml", SAML2MetadataResource(hs))
         self.putChild(b"authn_response", SAML2ResponseResource(hs))
+
+
+__all__ = ["SAML2Resource"]
diff --git a/synapse/rest/saml2/metadata_resource.py b/synapse/rest/synapse/client/saml2/metadata_resource.py
index 1e8526e22e..1e8526e22e 100644
--- a/synapse/rest/saml2/metadata_resource.py
+++ b/synapse/rest/synapse/client/saml2/metadata_resource.py
diff --git a/synapse/rest/saml2/response_resource.py b/synapse/rest/synapse/client/saml2/response_resource.py
index f6668fb5e3..f6668fb5e3 100644
--- a/synapse/rest/saml2/response_resource.py
+++ b/synapse/rest/synapse/client/saml2/response_resource.py
diff --git a/synapse/rest/synapse/client/sso_register.py b/synapse/rest/synapse/client/sso_register.py
new file mode 100644
index 0000000000..dfefeb7796
--- /dev/null
+++ b/synapse/rest/synapse/client/sso_register.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from typing import TYPE_CHECKING
+
+from twisted.web.http import Request
+
+from synapse.api.errors import SynapseError
+from synapse.handlers.sso import get_username_mapping_session_cookie_from_request
+from synapse.http.server import DirectServeHtmlResource
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class SsoRegisterResource(DirectServeHtmlResource):
+    """A resource which completes SSO registration
+
+    This resource gets mounted at /_synapse/client/sso_register, and is shown
+    after we collect username and/or consent for a new SSO user. It (finally) registers
+    the user, and confirms redirect to the client
+    """
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self._sso_handler = hs.get_sso_handler()
+
+    async def _async_render_GET(self, request: Request) -> None:
+        try:
+            session_id = get_username_mapping_session_cookie_from_request(request)
+        except SynapseError as e:
+            logger.warning("Error fetching session cookie: %s", e)
+            self._sso_handler.render_error(request, "bad_session", e.msg, code=e.code)
+            return
+        await self._sso_handler.register_sso_user(request, session_id)
diff --git a/synapse/rest/well_known.py b/synapse/rest/well_known.py
index f591cc6c5c..241fe746d9 100644
--- a/synapse/rest/well_known.py
+++ b/synapse/rest/well_known.py
@@ -34,10 +34,6 @@ class WellKnownBuilder:
         self._config = hs.config
 
     def get_well_known(self):
-        # if we don't have a public_baseurl, we can't help much here.
-        if self._config.public_baseurl is None:
-            return None
-
         result = {"m.homeserver": {"base_url": self._config.public_baseurl}}
 
         if self._config.default_identity_server:
diff --git a/synapse/server.py b/synapse/server.py
index 9cdda83aa1..9bdd3177d7 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -103,6 +103,7 @@ from synapse.notifier import Notifier
 from synapse.push.action_generator import ActionGenerator
 from synapse.push.pusherpool import PusherPool
 from synapse.replication.tcp.client import ReplicationDataHandler
+from synapse.replication.tcp.external_cache import ExternalCache
 from synapse.replication.tcp.handler import ReplicationCommandHandler
 from synapse.replication.tcp.resource import ReplicationStreamer
 from synapse.replication.tcp.streams import STREAMS_MAP, Stream
@@ -128,6 +129,8 @@ from synapse.util.stringutils import random_string
 logger = logging.getLogger(__name__)
 
 if TYPE_CHECKING:
+    from txredisapi import RedisProtocol
+
     from synapse.handlers.oidc_handler import OidcHandler
     from synapse.handlers.saml_handler import SamlHandler
 
@@ -716,6 +719,33 @@ class HomeServer(metaclass=abc.ABCMeta):
     def get_account_data_handler(self) -> AccountDataHandler:
         return AccountDataHandler(self)
 
+    @cache_in_self
+    def get_external_cache(self) -> ExternalCache:
+        return ExternalCache(self)
+
+    @cache_in_self
+    def get_outbound_redis_connection(self) -> Optional["RedisProtocol"]:
+        if not self.config.redis.redis_enabled:
+            return None
+
+        # We only want to import redis module if we're using it, as we have
+        # `txredisapi` as an optional dependency.
+        from synapse.replication.tcp.redis import lazyConnection
+
+        logger.info(
+            "Connecting to redis (host=%r port=%r) for external cache",
+            self.config.redis_host,
+            self.config.redis_port,
+        )
+
+        return lazyConnection(
+            hs=self,
+            host=self.config.redis_host,
+            port=self.config.redis_port,
+            password=self.config.redis.redis_password,
+            reconnect=True,
+        )
+
     async def remove_pusher(self, app_id: str, push_key: str, user_id: str):
         return await self.get_pusherpool().remove_pusher(app_id, push_key, user_id)
 
diff --git a/synapse/server_notices/resource_limits_server_notices.py b/synapse/server_notices/resource_limits_server_notices.py
index 2258d306d9..8dd01fce76 100644
--- a/synapse/server_notices/resource_limits_server_notices.py
+++ b/synapse/server_notices/resource_limits_server_notices.py
@@ -42,6 +42,7 @@ class ResourceLimitsServerNotices:
         self._auth = hs.get_auth()
         self._config = hs.config
         self._resouce_limited = False
+        self._account_data_handler = hs.get_account_data_handler()
         self._message_handler = hs.get_message_handler()
         self._state = hs.get_state_handler()
 
@@ -177,7 +178,7 @@ class ResourceLimitsServerNotices:
                 # tag already present, nothing to do here
                 need_to_set_tag = False
         if need_to_set_tag:
-            max_id = await self._store.add_tag_to_room(
+            max_id = await self._account_data_handler.add_tag_to_room(
                 user_id, room_id, SERVER_NOTICE_ROOM_TAG, {}
             )
             self._notifier.on_new_event("account_data_key", max_id, users=[user_id])
diff --git a/synapse/server_notices/server_notices_manager.py b/synapse/server_notices/server_notices_manager.py
index 100dbd5e2c..c46b2f047d 100644
--- a/synapse/server_notices/server_notices_manager.py
+++ b/synapse/server_notices/server_notices_manager.py
@@ -35,6 +35,7 @@ class ServerNoticesManager:
 
         self._store = hs.get_datastore()
         self._config = hs.config
+        self._account_data_handler = hs.get_account_data_handler()
         self._room_creation_handler = hs.get_room_creation_handler()
         self._room_member_handler = hs.get_room_member_handler()
         self._event_creation_handler = hs.get_event_creation_handler()
@@ -163,7 +164,7 @@ class ServerNoticesManager:
         )
         room_id = info["room_id"]
 
-        max_id = await self._store.add_tag_to_room(
+        max_id = await self._account_data_handler.add_tag_to_room(
             user_id, room_id, SERVER_NOTICE_ROOM_TAG, {}
         )
         self._notifier.on_new_event("account_data_key", max_id, users=[user_id])
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index 84f59c7d85..3bd9ff8ca0 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -310,6 +310,7 @@ class StateHandler:
             state_group_before_event = None
             state_group_before_event_prev_group = None
             deltas_to_state_group_before_event = None
+            entry = None
 
         else:
             # otherwise, we'll need to resolve the state across the prev_events.
@@ -340,9 +341,13 @@ class StateHandler:
                 current_state_ids=state_ids_before_event,
             )
 
-            # XXX: can we update the state cache entry for the new state group? or
-            # could we set a flag on resolve_state_groups_for_events to tell it to
-            # always make a state group?
+            # Assign the new state group to the cached state entry.
+            #
+            # Note that this can race in that we could generate multiple state
+            # groups for the same state entry, but that is just inefficient
+            # rather than dangerous.
+            if entry and entry.state_group is None:
+                entry.state_group = state_group_before_event
 
         #
         # now if it's not a state event, we're done
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index a19d65ad23..d2ba4bd2fc 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -262,13 +262,18 @@ class LoggingTransaction:
         return self.txn.description
 
     def execute_batch(self, sql: str, args: Iterable[Iterable[Any]]) -> None:
+        """Similar to `executemany`, except `txn.rowcount` will not be correct
+        afterwards.
+
+        More efficient than `executemany` on PostgreSQL
+        """
+
         if isinstance(self.database_engine, PostgresEngine):
             from psycopg2.extras import execute_batch  # type: ignore
 
             self._do_execute(lambda *x: execute_batch(self.txn, *x), sql, args)
         else:
-            for val in args:
-                self.execute(sql, val)
+            self.executemany(sql, args)
 
     def execute_values(self, sql: str, *args: Any) -> List[Tuple]:
         """Corresponds to psycopg2.extras.execute_values. Only available when
@@ -888,7 +893,7 @@ class DatabasePool:
             ", ".join("?" for _ in keys[0]),
         )
 
-        txn.executemany(sql, vals)
+        txn.execute_batch(sql, vals)
 
     async def simple_upsert(
         self,
diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index ae561a2da3..5d0845588c 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
 # Copyright 2018 New Vector Ltd
-# Copyright 2019 The Matrix.org Foundation C.I.C.
+# Copyright 2019-2021 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -43,6 +43,7 @@ from .end_to_end_keys import EndToEndKeyStore
 from .event_federation import EventFederationStore
 from .event_push_actions import EventPushActionsStore
 from .events_bg_updates import EventsBackgroundUpdatesStore
+from .events_forward_extremities import EventForwardExtremitiesStore
 from .filtering import FilteringStore
 from .group_server import GroupServerStore
 from .keys import KeyStore
@@ -118,6 +119,7 @@ class DataStore(
     UIAuthStore,
     CacheInvalidationWorkerStore,
     ServerMetricsStore,
+    EventForwardExtremitiesStore,
 ):
     def __init__(self, database: DatabasePool, db_conn, hs):
         self.hs = hs
diff --git a/synapse/storage/databases/main/account_data.py b/synapse/storage/databases/main/account_data.py
index 68896f34af..a277a1ef13 100644
--- a/synapse/storage/databases/main/account_data.py
+++ b/synapse/storage/databases/main/account_data.py
@@ -68,7 +68,7 @@ class AccountDataWorkerStore(SQLBaseStore):
             # `StreamIdGenerator`, otherwise we use `SlavedIdTracker` which gets
             # updated over replication. (Multiple writers are not supported for
             # SQLite).
-            if hs.get_instance_name() in hs.config.worker.writers.events:
+            if hs.get_instance_name() in hs.config.worker.writers.account_data:
                 self._account_data_id_gen = StreamIdGenerator(
                     db_conn,
                     "room_account_data",
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index 9097677648..659d8f245f 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -897,7 +897,7 @@ class DeviceWorkerStore(SQLBaseStore):
                 DELETE FROM device_lists_outbound_last_success
                 WHERE destination = ? AND user_id = ?
             """
-            txn.executemany(sql, ((row[0], row[1]) for row in rows))
+            txn.execute_batch(sql, ((row[0], row[1]) for row in rows))
 
             logger.info("Pruned %d device list outbound pokes", count)
 
@@ -1343,7 +1343,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
 
         # Delete older entries in the table, as we really only care about
         # when the latest change happened.
-        txn.executemany(
+        txn.execute_batch(
             """
             DELETE FROM device_lists_stream
             WHERE user_id = ? AND device_id = ? AND stream_id < ?
diff --git a/synapse/storage/databases/main/end_to_end_keys.py b/synapse/storage/databases/main/end_to_end_keys.py
index c128889bf9..309f1e865b 100644
--- a/synapse/storage/databases/main/end_to_end_keys.py
+++ b/synapse/storage/databases/main/end_to_end_keys.py
@@ -634,7 +634,7 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore):
 
     async def get_e2e_cross_signing_keys_bulk(
         self, user_ids: List[str], from_user_id: Optional[str] = None
-    ) -> Dict[str, Dict[str, dict]]:
+    ) -> Dict[str, Optional[Dict[str, dict]]]:
         """Returns the cross-signing keys for a set of users.
 
         Args:
@@ -724,7 +724,7 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore):
 
     async def claim_e2e_one_time_keys(
         self, query_list: Iterable[Tuple[str, str, str]]
-    ) -> Dict[str, Dict[str, Dict[str, bytes]]]:
+    ) -> Dict[str, Dict[str, Dict[str, str]]]:
         """Take a list of one time keys out of the database.
 
         Args:
diff --git a/synapse/storage/databases/main/event_push_actions.py b/synapse/storage/databases/main/event_push_actions.py
index 1b657191a9..438383abe1 100644
--- a/synapse/storage/databases/main/event_push_actions.py
+++ b/synapse/storage/databases/main/event_push_actions.py
@@ -487,7 +487,7 @@ class EventPushActionsWorkerStore(SQLBaseStore):
                 VALUES (?, ?, ?, ?, ?, ?)
             """
 
-            txn.executemany(
+            txn.execute_batch(
                 sql,
                 (
                     _gen_entry(user_id, actions)
@@ -803,7 +803,7 @@ class EventPushActionsWorkerStore(SQLBaseStore):
             ],
         )
 
-        txn.executemany(
+        txn.execute_batch(
             """
                 UPDATE event_push_summary
                 SET notif_count = ?, unread_count = ?, stream_ordering = ?
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 3216b3f3c8..ccda9f1caa 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -473,8 +473,9 @@ class PersistEventsStore:
             txn, self.db_pool, event_to_room_id, event_to_types, event_to_auth_chain,
         )
 
-    @staticmethod
+    @classmethod
     def _add_chain_cover_index(
+        cls,
         txn,
         db_pool: DatabasePool,
         event_to_room_id: Dict[str, str],
@@ -614,60 +615,17 @@ class PersistEventsStore:
         if not events_to_calc_chain_id_for:
             return
 
-        # We now calculate the chain IDs/sequence numbers for the events. We
-        # do this by looking at the chain ID and sequence number of any auth
-        # event with the same type/state_key and incrementing the sequence
-        # number by one. If there was no match or the chain ID/sequence
-        # number is already taken we generate a new chain.
-        #
-        # We need to do this in a topologically sorted order as we want to
-        # generate chain IDs/sequence numbers of an event's auth events
-        # before the event itself.
-        chains_tuples_allocated = set()  # type: Set[Tuple[int, int]]
-        new_chain_tuples = {}  # type: Dict[str, Tuple[int, int]]
-        for event_id in sorted_topologically(
-            events_to_calc_chain_id_for, event_to_auth_chain
-        ):
-            existing_chain_id = None
-            for auth_id in event_to_auth_chain.get(event_id, []):
-                if event_to_types.get(event_id) == event_to_types.get(auth_id):
-                    existing_chain_id = chain_map[auth_id]
-                    break
-
-            new_chain_tuple = None
-            if existing_chain_id:
-                # We found a chain ID/sequence number candidate, check its
-                # not already taken.
-                proposed_new_id = existing_chain_id[0]
-                proposed_new_seq = existing_chain_id[1] + 1
-                if (proposed_new_id, proposed_new_seq) not in chains_tuples_allocated:
-                    already_allocated = db_pool.simple_select_one_onecol_txn(
-                        txn,
-                        table="event_auth_chains",
-                        keyvalues={
-                            "chain_id": proposed_new_id,
-                            "sequence_number": proposed_new_seq,
-                        },
-                        retcol="event_id",
-                        allow_none=True,
-                    )
-                    if already_allocated:
-                        # Mark it as already allocated so we don't need to hit
-                        # the DB again.
-                        chains_tuples_allocated.add((proposed_new_id, proposed_new_seq))
-                    else:
-                        new_chain_tuple = (
-                            proposed_new_id,
-                            proposed_new_seq,
-                        )
-
-            if not new_chain_tuple:
-                new_chain_tuple = (db_pool.event_chain_id_gen.get_next_id_txn(txn), 1)
-
-            chains_tuples_allocated.add(new_chain_tuple)
-
-            chain_map[event_id] = new_chain_tuple
-            new_chain_tuples[event_id] = new_chain_tuple
+        # Allocate chain ID/sequence numbers to each new event.
+        new_chain_tuples = cls._allocate_chain_ids(
+            txn,
+            db_pool,
+            event_to_room_id,
+            event_to_types,
+            event_to_auth_chain,
+            events_to_calc_chain_id_for,
+            chain_map,
+        )
+        chain_map.update(new_chain_tuples)
 
         db_pool.simple_insert_many_txn(
             txn,
@@ -794,6 +752,137 @@ class PersistEventsStore:
             ],
         )
 
+    @staticmethod
+    def _allocate_chain_ids(
+        txn,
+        db_pool: DatabasePool,
+        event_to_room_id: Dict[str, str],
+        event_to_types: Dict[str, Tuple[str, str]],
+        event_to_auth_chain: Dict[str, List[str]],
+        events_to_calc_chain_id_for: Set[str],
+        chain_map: Dict[str, Tuple[int, int]],
+    ) -> Dict[str, Tuple[int, int]]:
+        """Allocates, but does not persist, chain ID/sequence numbers for the
+        events in `events_to_calc_chain_id_for`. (c.f. _add_chain_cover_index
+        for info on args)
+        """
+
+        # We now calculate the chain IDs/sequence numbers for the events. We do
+        # this by looking at the chain ID and sequence number of any auth event
+        # with the same type/state_key and incrementing the sequence number by
+        # one. If there was no match or the chain ID/sequence number is already
+        # taken we generate a new chain.
+        #
+        # We try to reduce the number of times that we hit the database by
+        # batching up calls, to make this more efficient when persisting large
+        # numbers of state events (e.g. during joins).
+        #
+        # We do this by:
+        #   1. Calculating for each event which auth event will be used to
+        #      inherit the chain ID, i.e. converting the auth chain graph to a
+        #      tree that we can allocate chains on. We also keep track of which
+        #      existing chain IDs have been referenced.
+        #   2. Fetching the max allocated sequence number for each referenced
+        #      existing chain ID, generating a map from chain ID to the max
+        #      allocated sequence number.
+        #   3. Iterating over the tree and allocating a chain ID/seq no. to the
+        #      new event, by incrementing the sequence number from the
+        #      referenced event's chain ID/seq no. and checking that the
+        #      incremented sequence number hasn't already been allocated (by
+        #      looking in the map generated in the previous step). We generate a
+        #      new chain if the sequence number has already been allocated.
+        #
+
+        existing_chains = set()  # type: Set[int]
+        tree = []  # type: List[Tuple[str, Optional[str]]]
+
+        # We need to do this in a topologically sorted order as we want to
+        # generate chain IDs/sequence numbers of an event's auth events before
+        # the event itself.
+        for event_id in sorted_topologically(
+            events_to_calc_chain_id_for, event_to_auth_chain
+        ):
+            for auth_id in event_to_auth_chain.get(event_id, []):
+                if event_to_types.get(event_id) == event_to_types.get(auth_id):
+                    existing_chain_id = chain_map.get(auth_id)
+                    if existing_chain_id:
+                        existing_chains.add(existing_chain_id[0])
+
+                    tree.append((event_id, auth_id))
+                    break
+            else:
+                tree.append((event_id, None))
+
+        # Fetch the current max sequence number for each existing referenced chain.
+        sql = """
+            SELECT chain_id, MAX(sequence_number) FROM event_auth_chains
+            WHERE %s
+            GROUP BY chain_id
+        """
+        clause, args = make_in_list_sql_clause(
+            db_pool.engine, "chain_id", existing_chains
+        )
+        txn.execute(sql % (clause,), args)
+
+        chain_to_max_seq_no = {row[0]: row[1] for row in txn}  # type: Dict[Any, int]
+
+        # Allocate the new events chain ID/sequence numbers.
+        #
+        # To reduce the number of calls to the database we don't allocate a
+        # chain ID number in the loop, instead we use a temporary `object()` for
+        # each new chain ID. Once we've done the loop we generate the necessary
+        # number of new chain IDs in one call, replacing all temporary
+        # objects with real allocated chain IDs.
+
+        unallocated_chain_ids = set()  # type: Set[object]
+        new_chain_tuples = {}  # type: Dict[str, Tuple[Any, int]]
+        for event_id, auth_event_id in tree:
+            # If we reference an auth_event_id we fetch the allocated chain ID,
+            # either from the existing `chain_map` or the newly generated
+            # `new_chain_tuples` map.
+            existing_chain_id = None
+            if auth_event_id:
+                existing_chain_id = new_chain_tuples.get(auth_event_id)
+                if not existing_chain_id:
+                    existing_chain_id = chain_map[auth_event_id]
+
+            new_chain_tuple = None  # type: Optional[Tuple[Any, int]]
+            if existing_chain_id:
+                # We found a chain ID/sequence number candidate, check its
+                # not already taken.
+                proposed_new_id = existing_chain_id[0]
+                proposed_new_seq = existing_chain_id[1] + 1
+
+                if chain_to_max_seq_no[proposed_new_id] < proposed_new_seq:
+                    new_chain_tuple = (
+                        proposed_new_id,
+                        proposed_new_seq,
+                    )
+
+            # If we need to start a new chain we allocate a temporary chain ID.
+            if not new_chain_tuple:
+                new_chain_tuple = (object(), 1)
+                unallocated_chain_ids.add(new_chain_tuple[0])
+
+            new_chain_tuples[event_id] = new_chain_tuple
+            chain_to_max_seq_no[new_chain_tuple[0]] = new_chain_tuple[1]
+
+        # Generate new chain IDs for all unallocated chain IDs.
+        newly_allocated_chain_ids = db_pool.event_chain_id_gen.get_next_mult_txn(
+            txn, len(unallocated_chain_ids)
+        )
+
+        # Map from potentially temporary chain ID to real chain ID
+        chain_id_to_allocated_map = dict(
+            zip(unallocated_chain_ids, newly_allocated_chain_ids)
+        )  # type: Dict[Any, int]
+        chain_id_to_allocated_map.update((c, c) for c in existing_chains)
+
+        return {
+            event_id: (chain_id_to_allocated_map[chain_id], seq)
+            for event_id, (chain_id, seq) in new_chain_tuples.items()
+        }
+
     def _persist_transaction_ids_txn(
         self,
         txn: LoggingTransaction,
@@ -876,7 +965,7 @@ class PersistEventsStore:
                         WHERE room_id = ? AND type = ? AND state_key = ?
                     )
                 """
-                txn.executemany(
+                txn.execute_batch(
                     sql,
                     (
                         (
@@ -895,7 +984,7 @@ class PersistEventsStore:
                 )
                 # Now we actually update the current_state_events table
 
-                txn.executemany(
+                txn.execute_batch(
                     "DELETE FROM current_state_events"
                     " WHERE room_id = ? AND type = ? AND state_key = ?",
                     (
@@ -907,7 +996,7 @@ class PersistEventsStore:
                 # We include the membership in the current state table, hence we do
                 # a lookup when we insert. This assumes that all events have already
                 # been inserted into room_memberships.
-                txn.executemany(
+                txn.execute_batch(
                     """INSERT INTO current_state_events
                         (room_id, type, state_key, event_id, membership)
                     VALUES (?, ?, ?, ?, (SELECT membership FROM room_memberships WHERE event_id = ?))
@@ -927,7 +1016,7 @@ class PersistEventsStore:
             # we have no record of the fact the user *was* a member of the
             # room but got, say, state reset out of it.
             if to_delete or to_insert:
-                txn.executemany(
+                txn.execute_batch(
                     "DELETE FROM local_current_membership"
                     " WHERE room_id = ? AND user_id = ?",
                     (
@@ -938,7 +1027,7 @@ class PersistEventsStore:
                 )
 
             if to_insert:
-                txn.executemany(
+                txn.execute_batch(
                     """INSERT INTO local_current_membership
                         (room_id, user_id, event_id, membership)
                     VALUES (?, ?, ?, (SELECT membership FROM room_memberships WHERE event_id = ?))
@@ -1738,7 +1827,7 @@ class PersistEventsStore:
         """
 
         if events_and_contexts:
-            txn.executemany(
+            txn.execute_batch(
                 sql,
                 (
                     (
@@ -1767,7 +1856,7 @@ class PersistEventsStore:
 
         # Now we delete the staging area for *all* events that were being
         # persisted.
-        txn.executemany(
+        txn.execute_batch(
             "DELETE FROM event_push_actions_staging WHERE event_id = ?",
             ((event.event_id,) for event, _ in all_events_and_contexts),
         )
@@ -1886,7 +1975,7 @@ class PersistEventsStore:
             " )"
         )
 
-        txn.executemany(
+        txn.execute_batch(
             query,
             [
                 (e_id, ev.room_id, e_id, ev.room_id, e_id, ev.room_id, False)
@@ -1900,7 +1989,7 @@ class PersistEventsStore:
             "DELETE FROM event_backward_extremities"
             " WHERE event_id = ? AND room_id = ?"
         )
-        txn.executemany(
+        txn.execute_batch(
             query,
             [
                 (ev.event_id, ev.room_id)
diff --git a/synapse/storage/databases/main/events_bg_updates.py b/synapse/storage/databases/main/events_bg_updates.py
index e46e44ba54..5ca4fa6817 100644
--- a/synapse/storage/databases/main/events_bg_updates.py
+++ b/synapse/storage/databases/main/events_bg_updates.py
@@ -139,8 +139,6 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
         max_stream_id = progress["max_stream_id_exclusive"]
         rows_inserted = progress.get("rows_inserted", 0)
 
-        INSERT_CLUMP_SIZE = 1000
-
         def reindex_txn(txn):
             sql = (
                 "SELECT stream_ordering, event_id, json FROM events"
@@ -178,9 +176,7 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
 
             sql = "UPDATE events SET sender = ?, contains_url = ? WHERE event_id = ?"
 
-            for index in range(0, len(update_rows), INSERT_CLUMP_SIZE):
-                clump = update_rows[index : index + INSERT_CLUMP_SIZE]
-                txn.executemany(sql, clump)
+            txn.execute_batch(sql, update_rows)
 
             progress = {
                 "target_min_stream_id_inclusive": target_min_stream_id,
@@ -210,8 +206,6 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
         max_stream_id = progress["max_stream_id_exclusive"]
         rows_inserted = progress.get("rows_inserted", 0)
 
-        INSERT_CLUMP_SIZE = 1000
-
         def reindex_search_txn(txn):
             sql = (
                 "SELECT stream_ordering, event_id FROM events"
@@ -256,9 +250,7 @@ class EventsBackgroundUpdatesStore(SQLBaseStore):
 
             sql = "UPDATE events SET origin_server_ts = ? WHERE event_id = ?"
 
-            for index in range(0, len(rows_to_update), INSERT_CLUMP_SIZE):
-                clump = rows_to_update[index : index + INSERT_CLUMP_SIZE]
-                txn.executemany(sql, clump)
+            txn.execute_batch(sql, rows_to_update)
 
             progress = {
                 "target_min_stream_id_inclusive": target_min_stream_id,
diff --git a/synapse/storage/databases/main/events_forward_extremities.py b/synapse/storage/databases/main/events_forward_extremities.py
new file mode 100644
index 0000000000..0ac1da9c35
--- /dev/null
+++ b/synapse/storage/databases/main/events_forward_extremities.py
@@ -0,0 +1,101 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+from typing import Dict, List
+
+from synapse.api.errors import SynapseError
+from synapse.storage._base import SQLBaseStore
+
+logger = logging.getLogger(__name__)
+
+
+class EventForwardExtremitiesStore(SQLBaseStore):
+    async def delete_forward_extremities_for_room(self, room_id: str) -> int:
+        """Delete any extra forward extremities for a room.
+
+        Invalidates the "get_latest_event_ids_in_room" cache if any forward
+        extremities were deleted.
+
+        Returns count deleted.
+        """
+
+        def delete_forward_extremities_for_room_txn(txn):
+            # First we need to get the event_id to not delete
+            sql = """
+                SELECT event_id FROM event_forward_extremities
+                INNER JOIN events USING (room_id, event_id)
+                WHERE room_id = ?
+                ORDER BY stream_ordering DESC
+                LIMIT 1
+            """
+            txn.execute(sql, (room_id,))
+            rows = txn.fetchall()
+            try:
+                event_id = rows[0][0]
+                logger.debug(
+                    "Found event_id %s as the forward extremity to keep for room %s",
+                    event_id,
+                    room_id,
+                )
+            except KeyError:
+                msg = "No forward extremity event found for room %s" % room_id
+                logger.warning(msg)
+                raise SynapseError(400, msg)
+
+            # Now delete the extra forward extremities
+            sql = """
+                DELETE FROM event_forward_extremities
+                WHERE event_id != ? AND room_id = ?
+            """
+
+            txn.execute(sql, (event_id, room_id))
+            logger.info(
+                "Deleted %s extra forward extremities for room %s",
+                txn.rowcount,
+                room_id,
+            )
+
+            if txn.rowcount > 0:
+                # Invalidate the cache
+                self._invalidate_cache_and_stream(
+                    txn, self.get_latest_event_ids_in_room, (room_id,),
+                )
+
+            return txn.rowcount
+
+        return await self.db_pool.runInteraction(
+            "delete_forward_extremities_for_room",
+            delete_forward_extremities_for_room_txn,
+        )
+
+    async def get_forward_extremities_for_room(self, room_id: str) -> List[Dict]:
+        """Get list of forward extremities for a room."""
+
+        def get_forward_extremities_for_room_txn(txn):
+            sql = """
+                SELECT event_id, state_group, depth, received_ts
+                FROM event_forward_extremities
+                INNER JOIN event_to_state_groups USING (event_id)
+                INNER JOIN events USING (room_id, event_id)
+                WHERE room_id = ?
+            """
+
+            txn.execute(sql, (room_id,))
+            return self.db_pool.cursor_to_dict(txn)
+
+        return await self.db_pool.runInteraction(
+            "get_forward_extremities_for_room", get_forward_extremities_for_room_txn,
+        )
diff --git a/synapse/storage/databases/main/media_repository.py b/synapse/storage/databases/main/media_repository.py
index 283c8a5e22..e017177655 100644
--- a/synapse/storage/databases/main/media_repository.py
+++ b/synapse/storage/databases/main/media_repository.py
@@ -417,7 +417,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                 " WHERE media_origin = ? AND media_id = ?"
             )
 
-            txn.executemany(
+            txn.execute_batch(
                 sql,
                 (
                     (time_ms, media_origin, media_id)
@@ -430,7 +430,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
                 " WHERE media_id = ?"
             )
 
-            txn.executemany(sql, ((time_ms, media_id) for media_id in local_media))
+            txn.execute_batch(sql, ((time_ms, media_id) for media_id in local_media))
 
         return await self.db_pool.runInteraction(
             "update_cached_last_access_time", update_cache_txn
@@ -557,7 +557,7 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
         sql = "DELETE FROM local_media_repository_url_cache WHERE media_id = ?"
 
         def _delete_url_cache_txn(txn):
-            txn.executemany(sql, [(media_id,) for media_id in media_ids])
+            txn.execute_batch(sql, [(media_id,) for media_id in media_ids])
 
         return await self.db_pool.runInteraction(
             "delete_url_cache", _delete_url_cache_txn
@@ -586,11 +586,11 @@ class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
         def _delete_url_cache_media_txn(txn):
             sql = "DELETE FROM local_media_repository WHERE media_id = ?"
 
-            txn.executemany(sql, [(media_id,) for media_id in media_ids])
+            txn.execute_batch(sql, [(media_id,) for media_id in media_ids])
 
             sql = "DELETE FROM local_media_repository_thumbnails WHERE media_id = ?"
 
-            txn.executemany(sql, [(media_id,) for media_id in media_ids])
+            txn.execute_batch(sql, [(media_id,) for media_id in media_ids])
 
         return await self.db_pool.runInteraction(
             "delete_url_cache_media", _delete_url_cache_media_txn
diff --git a/synapse/storage/databases/main/metrics.py b/synapse/storage/databases/main/metrics.py
index ab18cc4d79..92e65aa640 100644
--- a/synapse/storage/databases/main/metrics.py
+++ b/synapse/storage/databases/main/metrics.py
@@ -88,6 +88,62 @@ class ServerMetricsStore(EventPushActionsWorkerStore, SQLBaseStore):
             (x[0] - 1) * x[1] for x in res if x[1]
         )
 
+    async def count_daily_e2ee_messages(self):
+        """
+        Returns an estimate of the number of messages sent in the last day.
+
+        If it has been significantly less or more than one day since the last
+        call to this function, it will return None.
+        """
+
+        def _count_messages(txn):
+            sql = """
+                SELECT COALESCE(COUNT(*), 0) FROM events
+                WHERE type = 'm.room.encrypted'
+                AND stream_ordering > ?
+            """
+            txn.execute(sql, (self.stream_ordering_day_ago,))
+            (count,) = txn.fetchone()
+            return count
+
+        return await self.db_pool.runInteraction("count_e2ee_messages", _count_messages)
+
+    async def count_daily_sent_e2ee_messages(self):
+        def _count_messages(txn):
+            # This is good enough as if you have silly characters in your own
+            # hostname then thats your own fault.
+            like_clause = "%:" + self.hs.hostname
+
+            sql = """
+                SELECT COALESCE(COUNT(*), 0) FROM events
+                WHERE type = 'm.room.encrypted'
+                    AND sender LIKE ?
+                AND stream_ordering > ?
+            """
+
+            txn.execute(sql, (like_clause, self.stream_ordering_day_ago))
+            (count,) = txn.fetchone()
+            return count
+
+        return await self.db_pool.runInteraction(
+            "count_daily_sent_e2ee_messages", _count_messages
+        )
+
+    async def count_daily_active_e2ee_rooms(self):
+        def _count(txn):
+            sql = """
+                SELECT COALESCE(COUNT(DISTINCT room_id), 0) FROM events
+                WHERE type = 'm.room.encrypted'
+                AND stream_ordering > ?
+            """
+            txn.execute(sql, (self.stream_ordering_day_ago,))
+            (count,) = txn.fetchone()
+            return count
+
+        return await self.db_pool.runInteraction(
+            "count_daily_active_e2ee_rooms", _count
+        )
+
     async def count_daily_messages(self):
         """
         Returns an estimate of the number of messages sent in the last day.
diff --git a/synapse/storage/databases/main/purge_events.py b/synapse/storage/databases/main/purge_events.py
index 5d668aadb2..ecfc9f20b1 100644
--- a/synapse/storage/databases/main/purge_events.py
+++ b/synapse/storage/databases/main/purge_events.py
@@ -172,7 +172,7 @@ class PurgeEventsStore(StateGroupWorkerStore, SQLBaseStore):
         )
 
         # Update backward extremeties
-        txn.executemany(
+        txn.execute_batch(
             "INSERT INTO event_backward_extremities (room_id, event_id)"
             " VALUES (?, ?)",
             [(room_id, event_id) for event_id, in new_backwards_extrems],
diff --git a/synapse/storage/databases/main/pusher.py b/synapse/storage/databases/main/pusher.py
index bc7621b8d6..2687ef3e43 100644
--- a/synapse/storage/databases/main/pusher.py
+++ b/synapse/storage/databases/main/pusher.py
@@ -344,7 +344,9 @@ class PusherStore(PusherWorkerStore):
                 txn, self.get_if_user_has_pusher, (user_id,)
             )
 
-            self.db_pool.simple_delete_one_txn(
+            # It is expected that there is exactly one pusher to delete, but
+            # if it isn't there (or there are multiple) delete them all.
+            self.db_pool.simple_delete_txn(
                 txn,
                 "pushers",
                 {"app_id": app_id, "pushkey": pushkey, "user_name": user_id},
diff --git a/synapse/storage/databases/main/receipts.py b/synapse/storage/databases/main/receipts.py
index e0e57f0578..e4843a202c 100644
--- a/synapse/storage/databases/main/receipts.py
+++ b/synapse/storage/databases/main/receipts.py
@@ -45,7 +45,7 @@ class ReceiptsWorkerStore(SQLBaseStore):
             self._receipts_id_gen = MultiWriterIdGenerator(
                 db_conn=db_conn,
                 db=database,
-                stream_name="account_data",
+                stream_name="receipts",
                 instance_name=self._instance_name,
                 tables=[("receipts_linearized", "instance_name", "stream_id")],
                 sequence_name="receipts_sequence",
@@ -61,7 +61,7 @@ class ReceiptsWorkerStore(SQLBaseStore):
             # `StreamIdGenerator`, otherwise we use `SlavedIdTracker` which gets
             # updated over replication. (Multiple writers are not supported for
             # SQLite).
-            if hs.get_instance_name() in hs.config.worker.writers.events:
+            if hs.get_instance_name() in hs.config.worker.writers.receipts:
                 self._receipts_id_gen = StreamIdGenerator(
                     db_conn, "receipts_linearized", "stream_id"
                 )
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 8d05288ed4..8405dd460f 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -360,6 +360,35 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
 
         await self.db_pool.runInteraction("set_server_admin", set_server_admin_txn)
 
+    async def set_shadow_banned(self, user: UserID, shadow_banned: bool) -> None:
+        """Sets whether a user shadow-banned.
+
+        Args:
+            user: user ID of the user to test
+            shadow_banned: true iff the user is to be shadow-banned, false otherwise.
+        """
+
+        def set_shadow_banned_txn(txn):
+            self.db_pool.simple_update_one_txn(
+                txn,
+                table="users",
+                keyvalues={"name": user.to_string()},
+                updatevalues={"shadow_banned": shadow_banned},
+            )
+            # In order for this to apply immediately, clear the cache for this user.
+            tokens = self.db_pool.simple_select_onecol_txn(
+                txn,
+                table="access_tokens",
+                keyvalues={"user_id": user.to_string()},
+                retcol="token",
+            )
+            for token in tokens:
+                self._invalidate_cache_and_stream(
+                    txn, self.get_user_by_access_token, (token,)
+                )
+
+        await self.db_pool.runInteraction("set_shadow_banned", set_shadow_banned_txn)
+
     def _query_for_auth(self, txn, token: str) -> Optional[TokenLookupResult]:
         sql = """
             SELECT users.name as user_id,
@@ -443,6 +472,26 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
 
         return await self.db_pool.runInteraction("get_users_by_id_case_insensitive", f)
 
+    async def record_user_external_id(
+        self, auth_provider: str, external_id: str, user_id: str
+    ) -> None:
+        """Record a mapping from an external user id to a mxid
+
+        Args:
+            auth_provider: identifier for the remote auth provider
+            external_id: id on that system
+            user_id: complete mxid that it is mapped to
+        """
+        await self.db_pool.simple_insert(
+            table="user_external_ids",
+            values={
+                "auth_provider": auth_provider,
+                "external_id": external_id,
+                "user_id": user_id,
+            },
+            desc="record_user_external_id",
+        )
+
     async def get_user_by_external_id(
         self, auth_provider: str, external_id: str
     ) -> Optional[str]:
@@ -1104,7 +1153,7 @@ class RegistrationBackgroundUpdateStore(RegistrationWorkerStore):
                 FROM user_threepids
             """
 
-            txn.executemany(sql, [(id_server,) for id_server in id_servers])
+            txn.execute_batch(sql, [(id_server,) for id_server in id_servers])
 
         if id_servers:
             await self.db_pool.runInteraction(
@@ -1371,26 +1420,6 @@ class RegistrationStore(StatsStore, RegistrationBackgroundUpdateStore):
 
         self._invalidate_cache_and_stream(txn, self.get_user_by_id, (user_id,))
 
-    async def record_user_external_id(
-        self, auth_provider: str, external_id: str, user_id: str
-    ) -> None:
-        """Record a mapping from an external user id to a mxid
-
-        Args:
-            auth_provider: identifier for the remote auth provider
-            external_id: id on that system
-            user_id: complete mxid that it is mapped to
-        """
-        await self.db_pool.simple_insert(
-            table="user_external_ids",
-            values={
-                "auth_provider": auth_provider,
-                "external_id": external_id,
-                "user_id": user_id,
-            },
-            desc="record_user_external_id",
-        )
-
     async def user_set_password_hash(
         self, user_id: str, password_hash: Optional[str]
     ) -> None:
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index 284f2ce77c..a9fcb5f59c 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -16,7 +16,6 @@
 
 import collections
 import logging
-import re
 from abc import abstractmethod
 from enum import Enum
 from typing import Any, Dict, List, Optional, Tuple
@@ -30,6 +29,7 @@ from synapse.storage.databases.main.search import SearchStore
 from synapse.types import JsonDict, ThirdPartyInstanceID
 from synapse.util import json_encoder
 from synapse.util.caches.descriptors import cached
+from synapse.util.stringutils import MXC_REGEX
 
 logger = logging.getLogger(__name__)
 
@@ -660,8 +660,6 @@ class RoomWorkerStore(SQLBaseStore):
             The local and remote media as a lists of tuples where the key is
             the hostname and the value is the media ID.
         """
-        mxc_re = re.compile("^mxc://([^/]+)/([^/#?]+)")
-
         sql = """
             SELECT stream_ordering, json FROM events
             JOIN event_json USING (room_id, event_id)
@@ -688,7 +686,7 @@ class RoomWorkerStore(SQLBaseStore):
                 for url in (content_url, thumbnail_url):
                     if not url:
                         continue
-                    matches = mxc_re.match(url)
+                    matches = MXC_REGEX.match(url)
                     if matches:
                         hostname = matches.group(1)
                         media_id = matches.group(2)
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index dcdaf09682..92382bed28 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -873,8 +873,6 @@ class RoomMemberBackgroundUpdateStore(SQLBaseStore):
             "max_stream_id_exclusive", self._stream_order_on_start + 1
         )
 
-        INSERT_CLUMP_SIZE = 1000
-
         def add_membership_profile_txn(txn):
             sql = """
                 SELECT stream_ordering, event_id, events.room_id, event_json.json
@@ -915,9 +913,7 @@ class RoomMemberBackgroundUpdateStore(SQLBaseStore):
                 UPDATE room_memberships SET display_name = ?, avatar_url = ?
                 WHERE event_id = ? AND room_id = ?
             """
-            for index in range(0, len(to_update), INSERT_CLUMP_SIZE):
-                clump = to_update[index : index + INSERT_CLUMP_SIZE]
-                txn.executemany(to_update_sql, clump)
+            txn.execute_batch(to_update_sql, to_update)
 
             progress = {
                 "target_min_stream_id_inclusive": target_min_stream_id,
diff --git a/synapse/storage/databases/main/schema/delta/59/01ignored_user.py b/synapse/storage/databases/main/schema/delta/59/01ignored_user.py
index f35c70b699..9e8f35c1d2 100644
--- a/synapse/storage/databases/main/schema/delta/59/01ignored_user.py
+++ b/synapse/storage/databases/main/schema/delta/59/01ignored_user.py
@@ -55,7 +55,7 @@ def run_create(cur: Cursor, database_engine: BaseDatabaseEngine, *args, **kwargs
         # { "ignored_users": "@someone:example.org": {} }
         ignored_users = content.get("ignored_users", {})
         if isinstance(ignored_users, dict) and ignored_users:
-            cur.executemany(insert_sql, [(user_id, u) for u in ignored_users])
+            cur.execute_batch(insert_sql, [(user_id, u) for u in ignored_users])
 
     # Add indexes after inserting data for efficiency.
     logger.info("Adding constraints to ignored_users table")
diff --git a/synapse/storage/databases/main/schema/delta/59/07shard_account_data_fix.sql b/synapse/storage/databases/main/schema/delta/59/07shard_account_data_fix.sql
new file mode 100644
index 0000000000..9f2b5ebc5a
--- /dev/null
+++ b/synapse/storage/databases/main/schema/delta/59/07shard_account_data_fix.sql
@@ -0,0 +1,18 @@
+/* Copyright 2021 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- We incorrectly populated these, so we delete them and let the
+-- MultiWriterIdGenerator repopulate it.
+DELETE FROM stream_positions WHERE stream_name = 'receipts' OR stream_name = 'account_data';
diff --git a/synapse/storage/databases/main/search.py b/synapse/storage/databases/main/search.py
index e34fce6281..f5e7d9ef98 100644
--- a/synapse/storage/databases/main/search.py
+++ b/synapse/storage/databases/main/search.py
@@ -24,6 +24,7 @@ from synapse.storage._base import SQLBaseStore, db_to_json, make_in_list_sql_cla
 from synapse.storage.database import DatabasePool
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
+from synapse.types import Collection
 
 logger = logging.getLogger(__name__)
 
@@ -63,7 +64,7 @@ class SearchWorkerStore(SQLBaseStore):
                 for entry in entries
             )
 
-            txn.executemany(sql, args)
+            txn.execute_batch(sql, args)
 
         elif isinstance(self.database_engine, Sqlite3Engine):
             sql = (
@@ -75,7 +76,7 @@ class SearchWorkerStore(SQLBaseStore):
                 for entry in entries
             )
 
-            txn.executemany(sql, args)
+            txn.execute_batch(sql, args)
         else:
             # This should be unreachable.
             raise Exception("Unrecognized database engine")
@@ -460,7 +461,7 @@ class SearchStore(SearchBackgroundUpdateStore):
 
     async def search_rooms(
         self,
-        room_ids: List[str],
+        room_ids: Collection[str],
         search_term: str,
         keys: List[str],
         limit,
diff --git a/synapse/storage/databases/main/stats.py b/synapse/storage/databases/main/stats.py
index 0cdb3ec1f7..d421d18f8d 100644
--- a/synapse/storage/databases/main/stats.py
+++ b/synapse/storage/databases/main/stats.py
@@ -15,11 +15,12 @@
 # limitations under the License.
 
 import logging
-from collections import Counter
 from enum import Enum
 from itertools import chain
 from typing import Any, Dict, List, Optional, Tuple
 
+from typing_extensions import Counter
+
 from twisted.internet.defer import DeferredLock
 
 from synapse.api.constants import EventTypes, Membership
@@ -319,7 +320,9 @@ class StatsStore(StateDeltasStore):
         return slice_list
 
     @cached()
-    async def get_earliest_token_for_stats(self, stats_type: str, id: str) -> int:
+    async def get_earliest_token_for_stats(
+        self, stats_type: str, id: str
+    ) -> Optional[int]:
         """
         Fetch the "earliest token". This is used by the room stats delta
         processor to ignore deltas that have been processed between the
@@ -339,7 +342,7 @@ class StatsStore(StateDeltasStore):
         )
 
     async def bulk_update_stats_delta(
-        self, ts: int, updates: Dict[str, Dict[str, Dict[str, Counter]]], stream_id: int
+        self, ts: int, updates: Dict[str, Dict[str, Counter[str]]], stream_id: int
     ) -> None:
         """Bulk update stats tables for a given stream_id and updates the stats
         incremental position.
@@ -665,7 +668,7 @@ class StatsStore(StateDeltasStore):
 
     async def get_changes_room_total_events_and_bytes(
         self, min_pos: int, max_pos: int
-    ) -> Dict[str, Dict[str, int]]:
+    ) -> Tuple[Dict[str, Dict[str, int]], Dict[str, Dict[str, int]]]:
         """Fetches the counts of events in the given range of stream IDs.
 
         Args:
@@ -683,18 +686,19 @@ class StatsStore(StateDeltasStore):
             max_pos,
         )
 
-    def get_changes_room_total_events_and_bytes_txn(self, txn, low_pos, high_pos):
+    def get_changes_room_total_events_and_bytes_txn(
+        self, txn, low_pos: int, high_pos: int
+    ) -> Tuple[Dict[str, Dict[str, int]], Dict[str, Dict[str, int]]]:
         """Gets the total_events and total_event_bytes counts for rooms and
         senders, in a range of stream_orderings (including backfilled events).
 
         Args:
             txn
-            low_pos (int): Low stream ordering
-            high_pos (int): High stream ordering
+            low_pos: Low stream ordering
+            high_pos: High stream ordering
 
         Returns:
-            tuple[dict[str, dict[str, int]], dict[str, dict[str, int]]]: The
-            room and user deltas for total_events/total_event_bytes in the
+            The room and user deltas for total_events/total_event_bytes in the
             format of `stats_id` -> fields
         """
 
diff --git a/synapse/storage/databases/main/user_directory.py b/synapse/storage/databases/main/user_directory.py
index ef11f1c3b3..7b9729da09 100644
--- a/synapse/storage/databases/main/user_directory.py
+++ b/synapse/storage/databases/main/user_directory.py
@@ -540,7 +540,7 @@ class UserDirectoryBackgroundUpdateStore(StateDeltasStore):
             desc="get_user_in_directory",
         )
 
-    async def update_user_directory_stream_pos(self, stream_id: str) -> None:
+    async def update_user_directory_stream_pos(self, stream_id: int) -> None:
         await self.db_pool.simple_update_one(
             table="user_directory_stream_pos",
             keyvalues={},
diff --git a/synapse/storage/databases/state/store.py b/synapse/storage/databases/state/store.py
index 0e31cc811a..89cdc84a9c 100644
--- a/synapse/storage/databases/state/store.py
+++ b/synapse/storage/databases/state/store.py
@@ -565,11 +565,11 @@ class StateGroupDataStore(StateBackgroundUpdateStore, SQLBaseStore):
             )
 
         logger.info("[purge] removing redundant state groups")
-        txn.executemany(
+        txn.execute_batch(
             "DELETE FROM state_groups_state WHERE state_group = ?",
             ((sg,) for sg in state_groups_to_delete),
         )
-        txn.executemany(
+        txn.execute_batch(
             "DELETE FROM state_groups WHERE id = ?",
             ((sg,) for sg in state_groups_to_delete),
         )
diff --git a/synapse/storage/util/id_generators.py b/synapse/storage/util/id_generators.py
index 39a3ab1162..71ef5a72dc 100644
--- a/synapse/storage/util/id_generators.py
+++ b/synapse/storage/util/id_generators.py
@@ -15,12 +15,11 @@
 import heapq
 import logging
 import threading
-from collections import deque
+from collections import OrderedDict
 from contextlib import contextmanager
 from typing import Dict, List, Optional, Set, Tuple, Union
 
 import attr
-from typing_extensions import Deque
 
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.database import DatabasePool, LoggingTransaction
@@ -101,7 +100,13 @@ class StreamIdGenerator:
             self._current = (max if step > 0 else min)(
                 self._current, _load_current_id(db_conn, table, column, step)
             )
-        self._unfinished_ids = deque()  # type: Deque[int]
+
+        # We use this as an ordered set, as we want to efficiently append items,
+        # remove items and get the first item. Since we insert IDs in order, the
+        # insertion ordering will ensure its in the correct ordering.
+        #
+        # The key and values are the same, but we never look at the values.
+        self._unfinished_ids = OrderedDict()  # type: OrderedDict[int, int]
 
     def get_next(self):
         """
@@ -113,7 +118,7 @@ class StreamIdGenerator:
             self._current += self._step
             next_id = self._current
 
-            self._unfinished_ids.append(next_id)
+            self._unfinished_ids[next_id] = next_id
 
         @contextmanager
         def manager():
@@ -121,7 +126,7 @@ class StreamIdGenerator:
                 yield next_id
             finally:
                 with self._lock:
-                    self._unfinished_ids.remove(next_id)
+                    self._unfinished_ids.pop(next_id)
 
         return _AsyncCtxManagerWrapper(manager())
 
@@ -140,7 +145,7 @@ class StreamIdGenerator:
             self._current += n * self._step
 
             for next_id in next_ids:
-                self._unfinished_ids.append(next_id)
+                self._unfinished_ids[next_id] = next_id
 
         @contextmanager
         def manager():
@@ -149,7 +154,7 @@ class StreamIdGenerator:
             finally:
                 with self._lock:
                     for next_id in next_ids:
-                        self._unfinished_ids.remove(next_id)
+                        self._unfinished_ids.pop(next_id)
 
         return _AsyncCtxManagerWrapper(manager())
 
@@ -162,7 +167,7 @@ class StreamIdGenerator:
         """
         with self._lock:
             if self._unfinished_ids:
-                return self._unfinished_ids[0] - self._step
+                return next(iter(self._unfinished_ids)) - self._step
 
             return self._current
 
@@ -261,7 +266,11 @@ class MultiWriterIdGenerator:
         # We check that the table and sequence haven't diverged.
         for table, _, id_column in tables:
             self._sequence_gen.check_consistency(
-                db_conn, table=table, id_column=id_column, positive=positive
+                db_conn,
+                table=table,
+                id_column=id_column,
+                stream_name=stream_name,
+                positive=positive,
             )
 
         # This goes and fills out the above state from the database.
diff --git a/synapse/storage/util/sequence.py b/synapse/storage/util/sequence.py
index 412df6b8ef..0ec4dc2918 100644
--- a/synapse/storage/util/sequence.py
+++ b/synapse/storage/util/sequence.py
@@ -45,6 +45,21 @@ and run the following SQL:
 See docs/postgres.md for more information.
 """
 
+_INCONSISTENT_STREAM_ERROR = """
+Postgres sequence '%(seq)s' is inconsistent with associated stream position
+of '%(stream_name)s' in the 'stream_positions' table.
+
+This is likely a programming error and should be reported at
+https://github.com/matrix-org/synapse.
+
+A temporary workaround to fix this error is to shut down Synapse (including
+any and all workers) and run the following SQL:
+
+    DELETE FROM stream_positions WHERE stream_name = '%(stream_name)s';
+
+This will need to be done every time the server is restarted.
+"""
+
 
 class SequenceGenerator(metaclass=abc.ABCMeta):
     """A class which generates a unique sequence of integers"""
@@ -55,19 +70,30 @@ class SequenceGenerator(metaclass=abc.ABCMeta):
         ...
 
     @abc.abstractmethod
+    def get_next_mult_txn(self, txn: Cursor, n: int) -> List[int]:
+        """Get the next `n` IDs in the sequence"""
+        ...
+
+    @abc.abstractmethod
     def check_consistency(
         self,
         db_conn: "LoggingDatabaseConnection",
         table: str,
         id_column: str,
+        stream_name: Optional[str] = None,
         positive: bool = True,
     ):
         """Should be called during start up to test that the current value of
         the sequence is greater than or equal to the maximum ID in the table.
 
-        This is to handle various cases where the sequence value can get out
-        of sync with the table, e.g. if Synapse gets rolled back to a previous
+        This is to handle various cases where the sequence value can get out of
+        sync with the table, e.g. if Synapse gets rolled back to a previous
         version and the rolled forwards again.
+
+        If a stream name is given then this will check that any value in the
+        `stream_positions` table is less than or equal to the current sequence
+        value. If it isn't then it's likely that streams have been crossed
+        somewhere (e.g. two ID generators have the same stream name).
         """
         ...
 
@@ -93,8 +119,12 @@ class PostgresSequenceGenerator(SequenceGenerator):
         db_conn: "LoggingDatabaseConnection",
         table: str,
         id_column: str,
+        stream_name: Optional[str] = None,
         positive: bool = True,
     ):
+        """See SequenceGenerator.check_consistency for docstring.
+        """
+
         txn = db_conn.cursor(txn_name="sequence.check_consistency")
 
         # First we get the current max ID from the table.
@@ -118,6 +148,18 @@ class PostgresSequenceGenerator(SequenceGenerator):
             "SELECT last_value, is_called FROM %(seq)s" % {"seq": self._sequence_name}
         )
         last_value, is_called = txn.fetchone()
+
+        # If we have an associated stream check the stream_positions table.
+        max_in_stream_positions = None
+        if stream_name:
+            txn.execute(
+                "SELECT MAX(stream_id) FROM stream_positions WHERE stream_name = ?",
+                (stream_name,),
+            )
+            row = txn.fetchone()
+            if row:
+                max_in_stream_positions = row[0]
+
         txn.close()
 
         # If `is_called` is False then `last_value` is actually the value that
@@ -138,6 +180,14 @@ class PostgresSequenceGenerator(SequenceGenerator):
                 % {"seq": self._sequence_name, "table": table, "max_id_sql": table_sql}
             )
 
+        # If we have values in the stream positions table then they have to be
+        # less than or equal to `last_value`
+        if max_in_stream_positions and max_in_stream_positions > last_value:
+            raise IncorrectDatabaseSetup(
+                _INCONSISTENT_STREAM_ERROR
+                % {"seq": self._sequence_name, "stream_name": stream_name}
+            )
+
 
 GetFirstCallbackType = Callable[[Cursor], int]
 
@@ -174,8 +224,24 @@ class LocalSequenceGenerator(SequenceGenerator):
             self._current_max_id += 1
             return self._current_max_id
 
+    def get_next_mult_txn(self, txn: Cursor, n: int) -> List[int]:
+        with self._lock:
+            if self._current_max_id is None:
+                assert self._callback is not None
+                self._current_max_id = self._callback(txn)
+                self._callback = None
+
+            first_id = self._current_max_id + 1
+            self._current_max_id += n
+            return [first_id + i for i in range(n)]
+
     def check_consistency(
-        self, db_conn: Connection, table: str, id_column: str, positive: bool = True
+        self,
+        db_conn: Connection,
+        table: str,
+        id_column: str,
+        stream_name: Optional[str] = None,
+        positive: bool = True,
     ):
         # There is nothing to do for in memory sequences
         pass
diff --git a/synapse/types.py b/synapse/types.py
index 20a43d05bf..eafe729dfe 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -37,7 +37,7 @@ from signedjson.key import decode_verify_key_bytes
 from unpaddedbase64 import decode_base64
 
 from synapse.api.errors import Codes, SynapseError
-from synapse.http.endpoint import parse_and_validate_server_name
+from synapse.util.stringutils import parse_and_validate_server_name
 
 if TYPE_CHECKING:
     from synapse.appservice.api import ApplicationService
diff --git a/synapse/util/iterutils.py b/synapse/util/iterutils.py
index 6ef2b008a4..8d2411513f 100644
--- a/synapse/util/iterutils.py
+++ b/synapse/util/iterutils.py
@@ -78,7 +78,7 @@ def sorted_topologically(
         if node not in degree_map:
             continue
 
-        for edge in edges:
+        for edge in set(edges):
             if edge in degree_map:
                 degree_map[node] += 1
 
diff --git a/synapse/util/module_loader.py b/synapse/util/module_loader.py
index 1ee61851e4..09b094ded7 100644
--- a/synapse/util/module_loader.py
+++ b/synapse/util/module_loader.py
@@ -49,7 +49,8 @@ def load_module(provider: dict, config_path: Iterable[str]) -> Tuple[Type, Any]:
     module = importlib.import_module(module)
     provider_class = getattr(module, clz)
 
-    module_config = provider.get("config")
+    # Load the module config. If None, pass an empty dictionary instead
+    module_config = provider.get("config") or {}
     try:
         provider_config = provider_class.parse_config(module_config)
     except jsonschema.ValidationError as e:
diff --git a/synapse/util/stringutils.py b/synapse/util/stringutils.py
index b103c8694c..f8038bf861 100644
--- a/synapse/util/stringutils.py
+++ b/synapse/util/stringutils.py
@@ -18,6 +18,7 @@ import random
 import re
 import string
 from collections.abc import Iterable
+from typing import Optional, Tuple
 
 from synapse.api.errors import Codes, SynapseError
 
@@ -26,6 +27,15 @@ _string_with_symbols = string.digits + string.ascii_letters + ".,;:^&*-_+=#~@"
 # https://matrix.org/docs/spec/client_server/r0.6.0#post-matrix-client-r0-register-email-requesttoken
 client_secret_regex = re.compile(r"^[0-9a-zA-Z\.\=\_\-]+$")
 
+# https://matrix.org/docs/spec/client_server/r0.6.1#matrix-content-mxc-uris,
+# together with https://github.com/matrix-org/matrix-doc/issues/2177 which basically
+# says "there is no grammar for media ids"
+#
+# The server_name part of this is purposely lax: use parse_and_validate_mxc for
+# additional validation.
+#
+MXC_REGEX = re.compile("^mxc://([^/]+)/([^/#?]+)$")
+
 # random_string and random_string_with_symbols are used for a range of things,
 # some cryptographically important, some less so. We use SystemRandom to make sure
 # we get cryptographically-secure randoms.
@@ -59,6 +69,88 @@ def assert_valid_client_secret(client_secret):
         )
 
 
+def parse_server_name(server_name: str) -> Tuple[str, Optional[int]]:
+    """Split a server name into host/port parts.
+
+    Args:
+        server_name: server name to parse
+
+    Returns:
+        host/port parts.
+
+    Raises:
+        ValueError if the server name could not be parsed.
+    """
+    try:
+        if server_name[-1] == "]":
+            # ipv6 literal, hopefully
+            return server_name, None
+
+        domain_port = server_name.rsplit(":", 1)
+        domain = domain_port[0]
+        port = int(domain_port[1]) if domain_port[1:] else None
+        return domain, port
+    except Exception:
+        raise ValueError("Invalid server name '%s'" % server_name)
+
+
+VALID_HOST_REGEX = re.compile("\\A[0-9a-zA-Z.-]+\\Z")
+
+
+def parse_and_validate_server_name(server_name: str) -> Tuple[str, Optional[int]]:
+    """Split a server name into host/port parts and do some basic validation.
+
+    Args:
+        server_name: server name to parse
+
+    Returns:
+        host/port parts.
+
+    Raises:
+        ValueError if the server name could not be parsed.
+    """
+    host, port = parse_server_name(server_name)
+
+    # these tests don't need to be bulletproof as we'll find out soon enough
+    # if somebody is giving us invalid data. What we *do* need is to be sure
+    # that nobody is sneaking IP literals in that look like hostnames, etc.
+
+    # look for ipv6 literals
+    if host[0] == "[":
+        if host[-1] != "]":
+            raise ValueError("Mismatched [...] in server name '%s'" % (server_name,))
+        return host, port
+
+    # otherwise it should only be alphanumerics.
+    if not VALID_HOST_REGEX.match(host):
+        raise ValueError(
+            "Server name '%s' contains invalid characters" % (server_name,)
+        )
+
+    return host, port
+
+
+def parse_and_validate_mxc_uri(mxc: str) -> Tuple[str, Optional[int], str]:
+    """Parse the given string as an MXC URI
+
+    Checks that the "server name" part is a valid server name
+
+    Args:
+        mxc: the (alleged) MXC URI to be checked
+    Returns:
+        hostname, port, media id
+    Raises:
+        ValueError if the URI cannot be parsed
+    """
+    m = MXC_REGEX.match(mxc)
+    if not m:
+        raise ValueError("mxc URI %r did not match expected format" % (mxc,))
+    server_name = m.group(1)
+    media_id = m.group(2)
+    host, port = parse_and_validate_server_name(server_name)
+    return host, port, media_id
+
+
 def shortstr(iterable: Iterable, maxitems: int = 5) -> str:
     """If iterable has maxitems or fewer, return the stringification of a list
     containing those items.
diff --git a/synapse/util/templates.py b/synapse/util/templates.py
new file mode 100644
index 0000000000..7e5109d206
--- /dev/null
+++ b/synapse/util/templates.py
@@ -0,0 +1,106 @@
+# -*- coding: utf-8 -*-
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for dealing with jinja2 templates"""
+
+import time
+import urllib.parse
+from typing import TYPE_CHECKING, Callable, Iterable, Union
+
+import jinja2
+
+if TYPE_CHECKING:
+    from synapse.config.homeserver import HomeServerConfig
+
+
+def build_jinja_env(
+    template_search_directories: Iterable[str],
+    config: "HomeServerConfig",
+    autoescape: Union[bool, Callable[[str], bool], None] = None,
+) -> jinja2.Environment:
+    """Set up a Jinja2 environment to load templates from the given search path
+
+    The returned environment defines the following filters:
+        - format_ts: formats timestamps as strings in the server's local timezone
+             (XXX: why is that useful??)
+        - mxc_to_http: converts mxc: uris to http URIs. Args are:
+             (uri, width, height, resize_method="crop")
+
+    and the following global variables:
+        - server_name: matrix server name
+
+    Args:
+        template_search_directories: directories to search for templates
+
+        config: homeserver config, for things like `server_name` and `public_baseurl`
+
+        autoescape: whether template variables should be autoescaped. bool, or
+           a function mapping from template name to bool. Defaults to escaping templates
+           whose names end in .html, .xml or .htm.
+
+    Returns:
+        jinja environment
+    """
+
+    if autoescape is None:
+        autoescape = jinja2.select_autoescape()
+
+    loader = jinja2.FileSystemLoader(template_search_directories)
+    env = jinja2.Environment(loader=loader, autoescape=autoescape)
+
+    # Update the environment with our custom filters
+    env.filters.update(
+        {
+            "format_ts": _format_ts_filter,
+            "mxc_to_http": _create_mxc_to_http_filter(config.public_baseurl),
+        }
+    )
+
+    # common variables for all templates
+    env.globals.update({"server_name": config.server_name})
+
+    return env
+
+
+def _create_mxc_to_http_filter(public_baseurl: str) -> Callable:
+    """Create and return a jinja2 filter that converts MXC urls to HTTP
+
+    Args:
+        public_baseurl: The public, accessible base URL of the homeserver
+    """
+
+    def mxc_to_http_filter(value, width, height, resize_method="crop"):
+        if value[0:6] != "mxc://":
+            return ""
+
+        server_and_media_id = value[6:]
+        fragment = None
+        if "#" in server_and_media_id:
+            server_and_media_id, fragment = server_and_media_id.split("#", 1)
+            fragment = "#" + fragment
+
+        params = {"width": width, "height": height, "method": resize_method}
+        return "%s_matrix/media/v1/thumbnail/%s?%s%s" % (
+            public_baseurl,
+            server_and_media_id,
+            urllib.parse.urlencode(params),
+            fragment or "",
+        )
+
+    return mxc_to_http_filter
+
+
+def _format_ts_filter(value: int, format: str):
+    return time.strftime(format, time.localtime(value / 1000))
diff --git a/tests/handlers/test_cas.py b/tests/handlers/test_cas.py
index c37bb6440e..7baf224f7e 100644
--- a/tests/handlers/test_cas.py
+++ b/tests/handlers/test_cas.py
@@ -62,7 +62,7 @@ class CasHandlerTestCase(HomeserverTestCase):
 
         # check that the auth handler got called as expected
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", request, "redirect_uri", None
+            "@test_user:test", request, "redirect_uri", None, new_user=True
         )
 
     def test_map_cas_user_to_existing_user(self):
@@ -85,7 +85,7 @@ class CasHandlerTestCase(HomeserverTestCase):
 
         # check that the auth handler got called as expected
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", request, "redirect_uri", None
+            "@test_user:test", request, "redirect_uri", None, new_user=False
         )
 
         # Subsequent calls should map to the same mxid.
@@ -94,7 +94,7 @@ class CasHandlerTestCase(HomeserverTestCase):
             self.handler._handle_cas_response(request, cas_response, "redirect_uri", "")
         )
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", request, "redirect_uri", None
+            "@test_user:test", request, "redirect_uri", None, new_user=False
         )
 
     def test_map_cas_user_to_invalid_localpart(self):
@@ -112,7 +112,7 @@ class CasHandlerTestCase(HomeserverTestCase):
 
         # check that the auth handler got called as expected
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@f=c3=b6=c3=b6:test", request, "redirect_uri", None
+            "@f=c3=b6=c3=b6:test", request, "redirect_uri", None, new_user=True
         )
 
 
diff --git a/tests/handlers/test_federation.py b/tests/handlers/test_federation.py
index 0b24b89a2e..74503112f5 100644
--- a/tests/handlers/test_federation.py
+++ b/tests/handlers/test_federation.py
@@ -16,7 +16,7 @@ import logging
 from unittest import TestCase
 
 from synapse.api.constants import EventTypes
-from synapse.api.errors import AuthError, Codes, SynapseError
+from synapse.api.errors import AuthError, Codes, LimitExceededError, SynapseError
 from synapse.api.room_versions import RoomVersions
 from synapse.events import EventBase
 from synapse.federation.federation_base import event_from_pdu_json
@@ -191,6 +191,97 @@ class FederationTestCase(unittest.HomeserverTestCase):
 
         self.assertEqual(sg, sg2)
 
+    @unittest.override_config(
+        {"rc_invites": {"per_room": {"per_second": 0.5, "burst_count": 3}}}
+    )
+    def test_invite_by_room_ratelimit(self):
+        """Tests that invites from federation in a room are actually rate-limited.
+        """
+        other_server = "otherserver"
+        other_user = "@otheruser:" + other_server
+
+        # create the room
+        user_id = self.register_user("kermit", "test")
+        tok = self.login("kermit", "test")
+        room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+        room_version = self.get_success(self.store.get_room_version(room_id))
+
+        def create_invite_for(local_user):
+            return event_from_pdu_json(
+                {
+                    "type": EventTypes.Member,
+                    "content": {"membership": "invite"},
+                    "room_id": room_id,
+                    "sender": other_user,
+                    "state_key": local_user,
+                    "depth": 32,
+                    "prev_events": [],
+                    "auth_events": [],
+                    "origin_server_ts": self.clock.time_msec(),
+                },
+                room_version,
+            )
+
+        for i in range(3):
+            self.get_success(
+                self.handler.on_invite_request(
+                    other_server,
+                    create_invite_for("@user-%d:test" % (i,)),
+                    room_version,
+                )
+            )
+
+        self.get_failure(
+            self.handler.on_invite_request(
+                other_server, create_invite_for("@user-4:test"), room_version,
+            ),
+            exc=LimitExceededError,
+        )
+
+    @unittest.override_config(
+        {"rc_invites": {"per_user": {"per_second": 0.5, "burst_count": 3}}}
+    )
+    def test_invite_by_user_ratelimit(self):
+        """Tests that invites from federation to a particular user are
+        actually rate-limited.
+        """
+        other_server = "otherserver"
+        other_user = "@otheruser:" + other_server
+
+        # create the room
+        user_id = self.register_user("kermit", "test")
+        tok = self.login("kermit", "test")
+
+        def create_invite():
+            room_id = self.helper.create_room_as(room_creator=user_id, tok=tok)
+            room_version = self.get_success(self.store.get_room_version(room_id))
+            return event_from_pdu_json(
+                {
+                    "type": EventTypes.Member,
+                    "content": {"membership": "invite"},
+                    "room_id": room_id,
+                    "sender": other_user,
+                    "state_key": "@user:test",
+                    "depth": 32,
+                    "prev_events": [],
+                    "auth_events": [],
+                    "origin_server_ts": self.clock.time_msec(),
+                },
+                room_version,
+            )
+
+        for i in range(3):
+            event = create_invite()
+            self.get_success(
+                self.handler.on_invite_request(other_server, event, event.room_version,)
+            )
+
+        event = create_invite()
+        self.get_failure(
+            self.handler.on_invite_request(other_server, event, event.room_version,),
+            exc=LimitExceededError,
+        )
+
     def _build_and_send_join_event(self, other_server, other_user, room_id):
         join_event = self.get_success(
             self.handler.on_make_join_request(other_server, room_id, other_user)
diff --git a/tests/handlers/test_oidc.py b/tests/handlers/test_oidc.py
index b3dfa40d25..ad20400b1d 100644
--- a/tests/handlers/test_oidc.py
+++ b/tests/handlers/test_oidc.py
@@ -40,7 +40,7 @@ ISSUER = "https://issuer/"
 CLIENT_ID = "test-client-id"
 CLIENT_SECRET = "test-client-secret"
 BASE_URL = "https://synapse/"
-CALLBACK_URL = BASE_URL + "_synapse/oidc/callback"
+CALLBACK_URL = BASE_URL + "_synapse/client/oidc/callback"
 SCOPES = ["openid"]
 
 AUTHORIZATION_ENDPOINT = ISSUER + "authorize"
@@ -58,12 +58,6 @@ COMMON_CONFIG = {
 }
 
 
-# The cookie name and path don't really matter, just that it has to be coherent
-# between the callback & redirect handlers.
-COOKIE_NAME = b"oidc_session"
-COOKIE_PATH = "/_synapse/oidc"
-
-
 class TestMappingProvider:
     @staticmethod
     def parse_config(config):
@@ -340,8 +334,11 @@ class OidcHandlerTestCase(HomeserverTestCase):
         # For some reason, call.args does not work with python3.5
         args = calls[0][0]
         kwargs = calls[0][1]
-        self.assertEqual(args[0], COOKIE_NAME)
-        self.assertEqual(kwargs["path"], COOKIE_PATH)
+
+        # The cookie name and path don't really matter, just that it has to be coherent
+        # between the callback & redirect handlers.
+        self.assertEqual(args[0], b"oidc_session")
+        self.assertEqual(kwargs["path"], "/_synapse/client/oidc")
         cookie = args[1]
 
         macaroon = pymacaroons.Macaroon.deserialize(cookie)
@@ -419,7 +416,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
         self.get_success(self.handler.handle_oidc_callback(request))
 
         auth_handler.complete_sso_login.assert_called_once_with(
-            expected_user_id, request, client_redirect_url, None,
+            expected_user_id, request, client_redirect_url, None, new_user=True
         )
         self.provider._exchange_code.assert_called_once_with(code)
         self.provider._parse_id_token.assert_called_once_with(token, nonce=nonce)
@@ -450,7 +447,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
         self.get_success(self.handler.handle_oidc_callback(request))
 
         auth_handler.complete_sso_login.assert_called_once_with(
-            expected_user_id, request, client_redirect_url, None,
+            expected_user_id, request, client_redirect_url, None, new_user=False
         )
         self.provider._exchange_code.assert_called_once_with(code)
         self.provider._parse_id_token.assert_not_called()
@@ -623,7 +620,11 @@ class OidcHandlerTestCase(HomeserverTestCase):
         self.get_success(self.handler.handle_oidc_callback(request))
 
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@foo:test", request, client_redirect_url, {"phone": "1234567"},
+            "@foo:test",
+            request,
+            client_redirect_url,
+            {"phone": "1234567"},
+            new_user=True,
         )
 
     def test_map_userinfo_to_user(self):
@@ -637,7 +638,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
         }
         self.get_success(_make_callback_with_userinfo(self.hs, userinfo))
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", ANY, ANY, None,
+            "@test_user:test", ANY, ANY, None, new_user=True
         )
         auth_handler.complete_sso_login.reset_mock()
 
@@ -648,7 +649,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
         }
         self.get_success(_make_callback_with_userinfo(self.hs, userinfo))
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user_2:test", ANY, ANY, None,
+            "@test_user_2:test", ANY, ANY, None, new_user=True
         )
         auth_handler.complete_sso_login.reset_mock()
 
@@ -685,14 +686,14 @@ class OidcHandlerTestCase(HomeserverTestCase):
         }
         self.get_success(_make_callback_with_userinfo(self.hs, userinfo))
         auth_handler.complete_sso_login.assert_called_once_with(
-            user.to_string(), ANY, ANY, None,
+            user.to_string(), ANY, ANY, None, new_user=False
         )
         auth_handler.complete_sso_login.reset_mock()
 
         # Subsequent calls should map to the same mxid.
         self.get_success(_make_callback_with_userinfo(self.hs, userinfo))
         auth_handler.complete_sso_login.assert_called_once_with(
-            user.to_string(), ANY, ANY, None,
+            user.to_string(), ANY, ANY, None, new_user=False
         )
         auth_handler.complete_sso_login.reset_mock()
 
@@ -707,7 +708,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
         }
         self.get_success(_make_callback_with_userinfo(self.hs, userinfo))
         auth_handler.complete_sso_login.assert_called_once_with(
-            user.to_string(), ANY, ANY, None,
+            user.to_string(), ANY, ANY, None, new_user=False
         )
         auth_handler.complete_sso_login.reset_mock()
 
@@ -743,7 +744,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
 
         self.get_success(_make_callback_with_userinfo(self.hs, userinfo))
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@TEST_USER_2:test", ANY, ANY, None,
+            "@TEST_USER_2:test", ANY, ANY, None, new_user=False
         )
 
     def test_map_userinfo_to_invalid_localpart(self):
@@ -779,7 +780,7 @@ class OidcHandlerTestCase(HomeserverTestCase):
 
         # test_user is already taken, so test_user1 gets registered instead.
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user1:test", ANY, ANY, None,
+            "@test_user1:test", ANY, ANY, None, new_user=True
         )
         auth_handler.complete_sso_login.reset_mock()
 
diff --git a/tests/handlers/test_saml.py b/tests/handlers/test_saml.py
index 261c7083d1..a8d6c0f617 100644
--- a/tests/handlers/test_saml.py
+++ b/tests/handlers/test_saml.py
@@ -131,7 +131,7 @@ class SamlHandlerTestCase(HomeserverTestCase):
 
         # check that the auth handler got called as expected
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", request, "redirect_uri", None
+            "@test_user:test", request, "redirect_uri", None, new_user=True
         )
 
     @override_config({"saml2_config": {"grandfathered_mxid_source_attribute": "mxid"}})
@@ -157,7 +157,7 @@ class SamlHandlerTestCase(HomeserverTestCase):
 
         # check that the auth handler got called as expected
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", request, "", None
+            "@test_user:test", request, "", None, new_user=False
         )
 
         # Subsequent calls should map to the same mxid.
@@ -166,7 +166,7 @@ class SamlHandlerTestCase(HomeserverTestCase):
             self.handler._handle_authn_response(request, saml_response, "")
         )
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user:test", request, "", None
+            "@test_user:test", request, "", None, new_user=False
         )
 
     def test_map_saml_response_to_invalid_localpart(self):
@@ -214,7 +214,7 @@ class SamlHandlerTestCase(HomeserverTestCase):
 
         # test_user is already taken, so test_user1 gets registered instead.
         auth_handler.complete_sso_login.assert_called_once_with(
-            "@test_user1:test", request, "", None
+            "@test_user1:test", request, "", None, new_user=True
         )
         auth_handler.complete_sso_login.reset_mock()
 
diff --git a/tests/http/test_endpoint.py b/tests/http/test_endpoint.py
index b2e9533b07..d06ea518ce 100644
--- a/tests/http/test_endpoint.py
+++ b/tests/http/test_endpoint.py
@@ -12,7 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from synapse.http.endpoint import parse_and_validate_server_name, parse_server_name
+from synapse.util.stringutils import parse_and_validate_server_name, parse_server_name
 
 from tests import unittest
 
diff --git a/tests/push/test_email.py b/tests/push/test_email.py
index 961bf09de9..c4e1e7ed85 100644
--- a/tests/push/test_email.py
+++ b/tests/push/test_email.py
@@ -187,6 +187,36 @@ class EmailPusherTests(HomeserverTestCase):
         # We should get emailed about those messages
         self._check_for_mail()
 
+    def test_multiple_rooms(self):
+        # We want to test multiple notifications from multiple rooms, so we pause
+        # processing of push while we send messages.
+        self.pusher._pause_processing()
+
+        # Create a simple room with multiple other users
+        rooms = [
+            self.helper.create_room_as(self.user_id, tok=self.access_token),
+            self.helper.create_room_as(self.user_id, tok=self.access_token),
+        ]
+
+        for r, other in zip(rooms, self.others):
+            self.helper.invite(
+                room=r, src=self.user_id, tok=self.access_token, targ=other.id
+            )
+            self.helper.join(room=r, user=other.id, tok=other.token)
+
+        # The other users send some messages
+        self.helper.send(rooms[0], body="Hi!", tok=self.others[0].token)
+        self.helper.send(rooms[1], body="There!", tok=self.others[1].token)
+        self.helper.send(rooms[1], body="There!", tok=self.others[1].token)
+
+        # Nothing should have happened yet, as we're paused.
+        assert not self.email_attempts
+
+        self.pusher._resume_processing()
+
+        # We should get emailed about those messages
+        self._check_for_mail()
+
     def test_encrypted_message(self):
         room = self.helper.create_room_as(self.user_id, tok=self.access_token)
         self.helper.invite(
diff --git a/tests/push/test_presentable_names.py b/tests/push/test_presentable_names.py
new file mode 100644
index 0000000000..aff563919d
--- /dev/null
+++ b/tests/push/test_presentable_names.py
@@ -0,0 +1,229 @@
+#  Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+from typing import Iterable, Optional, Tuple
+
+from synapse.api.constants import EventTypes, Membership
+from synapse.api.room_versions import RoomVersions
+from synapse.events import FrozenEvent
+from synapse.push.presentable_names import calculate_room_name
+from synapse.types import StateKey, StateMap
+
+from tests import unittest
+
+
+class MockDataStore:
+    """
+    A fake data store which stores a mapping of state key to event content.
+    (I.e. the state key is used as the event ID.)
+    """
+
+    def __init__(self, events: Iterable[Tuple[StateKey, dict]]):
+        """
+        Args:
+            events: A state map to event contents.
+        """
+        self._events = {}
+
+        for i, (event_id, content) in enumerate(events):
+            self._events[event_id] = FrozenEvent(
+                {
+                    "event_id": "$event_id",
+                    "type": event_id[0],
+                    "sender": "@user:test",
+                    "state_key": event_id[1],
+                    "room_id": "#room:test",
+                    "content": content,
+                    "origin_server_ts": i,
+                },
+                RoomVersions.V1,
+            )
+
+    async def get_event(
+        self, event_id: StateKey, allow_none: bool = False
+    ) -> Optional[FrozenEvent]:
+        assert allow_none, "Mock not configured for allow_none = False"
+
+        return self._events.get(event_id)
+
+    async def get_events(self, event_ids: Iterable[StateKey]):
+        # This is cheating since it just returns all events.
+        return self._events
+
+
+class PresentableNamesTestCase(unittest.HomeserverTestCase):
+    USER_ID = "@test:test"
+    OTHER_USER_ID = "@user:test"
+
+    def _calculate_room_name(
+        self,
+        events: StateMap[dict],
+        user_id: str = "",
+        fallback_to_members: bool = True,
+        fallback_to_single_member: bool = True,
+    ):
+        # This isn't 100% accurate, but works with MockDataStore.
+        room_state_ids = {k[0]: k[0] for k in events}
+
+        return self.get_success(
+            calculate_room_name(
+                MockDataStore(events),
+                room_state_ids,
+                user_id or self.USER_ID,
+                fallback_to_members,
+                fallback_to_single_member,
+            )
+        )
+
+    def test_name(self):
+        """A room name event should be used."""
+        events = [
+            ((EventTypes.Name, ""), {"name": "test-name"}),
+        ]
+        self.assertEqual("test-name", self._calculate_room_name(events))
+
+        # Check if the event content has garbage.
+        events = [((EventTypes.Name, ""), {"foo": 1})]
+        self.assertEqual("Empty Room", self._calculate_room_name(events))
+
+        events = [((EventTypes.Name, ""), {"name": 1})]
+        self.assertEqual(1, self._calculate_room_name(events))
+
+    def test_canonical_alias(self):
+        """An canonical alias should be used."""
+        events = [
+            ((EventTypes.CanonicalAlias, ""), {"alias": "#test-name:test"}),
+        ]
+        self.assertEqual("#test-name:test", self._calculate_room_name(events))
+
+        # Check if the event content has garbage.
+        events = [((EventTypes.CanonicalAlias, ""), {"foo": 1})]
+        self.assertEqual("Empty Room", self._calculate_room_name(events))
+
+        events = [((EventTypes.CanonicalAlias, ""), {"alias": "test-name"})]
+        self.assertEqual("Empty Room", self._calculate_room_name(events))
+
+    def test_invite(self):
+        """An invite has special behaviour."""
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.INVITE}),
+            ((EventTypes.Member, self.OTHER_USER_ID), {"displayname": "Other User"}),
+        ]
+        self.assertEqual("Invite from Other User", self._calculate_room_name(events))
+        self.assertIsNone(
+            self._calculate_room_name(events, fallback_to_single_member=False)
+        )
+        # Ensure this logic is skipped if we don't fallback to members.
+        self.assertIsNone(self._calculate_room_name(events, fallback_to_members=False))
+
+        # Check if the event content has garbage.
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.INVITE}),
+            ((EventTypes.Member, self.OTHER_USER_ID), {"foo": 1}),
+        ]
+        self.assertEqual("Invite from @user:test", self._calculate_room_name(events))
+
+        # No member event for sender.
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.INVITE}),
+        ]
+        self.assertEqual("Room Invite", self._calculate_room_name(events))
+
+    def test_no_members(self):
+        """Behaviour of an empty room."""
+        events = []
+        self.assertEqual("Empty Room", self._calculate_room_name(events))
+
+        # Note that events with invalid (or missing) membership are ignored.
+        events = [
+            ((EventTypes.Member, self.OTHER_USER_ID), {"foo": 1}),
+            ((EventTypes.Member, "@foo:test"), {"membership": "foo"}),
+        ]
+        self.assertEqual("Empty Room", self._calculate_room_name(events))
+
+    def test_no_other_members(self):
+        """Behaviour of a room with no other members in it."""
+        events = [
+            (
+                (EventTypes.Member, self.USER_ID),
+                {"membership": Membership.JOIN, "displayname": "Me"},
+            ),
+        ]
+        self.assertEqual("Me", self._calculate_room_name(events))
+
+        # Check if the event content has no displayname.
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.JOIN}),
+        ]
+        self.assertEqual("@test:test", self._calculate_room_name(events))
+
+        # 3pid invite, use the other user (who is set as the sender).
+        events = [
+            ((EventTypes.Member, self.OTHER_USER_ID), {"membership": Membership.JOIN}),
+        ]
+        self.assertEqual(
+            "nobody", self._calculate_room_name(events, user_id=self.OTHER_USER_ID)
+        )
+
+        events = [
+            ((EventTypes.Member, self.OTHER_USER_ID), {"membership": Membership.JOIN}),
+            ((EventTypes.ThirdPartyInvite, self.OTHER_USER_ID), {}),
+        ]
+        self.assertEqual(
+            "Inviting email address",
+            self._calculate_room_name(events, user_id=self.OTHER_USER_ID),
+        )
+
+    def test_one_other_member(self):
+        """Behaviour of a room with a single other member."""
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.JOIN}),
+            (
+                (EventTypes.Member, self.OTHER_USER_ID),
+                {"membership": Membership.JOIN, "displayname": "Other User"},
+            ),
+        ]
+        self.assertEqual("Other User", self._calculate_room_name(events))
+        self.assertIsNone(
+            self._calculate_room_name(events, fallback_to_single_member=False)
+        )
+
+        # Check if the event content has no displayname and is an invite.
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.JOIN}),
+            (
+                (EventTypes.Member, self.OTHER_USER_ID),
+                {"membership": Membership.INVITE},
+            ),
+        ]
+        self.assertEqual("@user:test", self._calculate_room_name(events))
+
+    def test_other_members(self):
+        """Behaviour of a room with multiple other members."""
+        # Two other members.
+        events = [
+            ((EventTypes.Member, self.USER_ID), {"membership": Membership.JOIN}),
+            (
+                (EventTypes.Member, self.OTHER_USER_ID),
+                {"membership": Membership.JOIN, "displayname": "Other User"},
+            ),
+            ((EventTypes.Member, "@foo:test"), {"membership": Membership.JOIN}),
+        ]
+        self.assertEqual("Other User and @foo:test", self._calculate_room_name(events))
+
+        # Three or more other members.
+        events.append(
+            ((EventTypes.Member, "@fourth:test"), {"membership": Membership.INVITE})
+        )
+        self.assertEqual("Other User and 2 others", self._calculate_room_name(events))
diff --git a/tests/push/test_push_rule_evaluator.py b/tests/push/test_push_rule_evaluator.py
index 1f4b5ca2ac..4a841f5bb8 100644
--- a/tests/push/test_push_rule_evaluator.py
+++ b/tests/push/test_push_rule_evaluator.py
@@ -29,7 +29,7 @@ class PushRuleEvaluatorTestCase(unittest.TestCase):
                 "type": "m.room.history_visibility",
                 "sender": "@user:test",
                 "state_key": "",
-                "room_id": "@room:test",
+                "room_id": "#room:test",
                 "content": content,
             },
             RoomVersions.V1,
diff --git a/tests/replication/_base.py b/tests/replication/_base.py
index 3379189785..d5dce1f83f 100644
--- a/tests/replication/_base.py
+++ b/tests/replication/_base.py
@@ -212,6 +212,9 @@ class BaseMultiWorkerStreamTestCase(unittest.HomeserverTestCase):
         # Fake in memory Redis server that servers can connect to.
         self._redis_server = FakeRedisPubSubServer()
 
+        # We may have an attempt to connect to redis for the external cache already.
+        self.connect_any_redis_attempts()
+
         store = self.hs.get_datastore()
         self.database_pool = store.db_pool
 
@@ -401,25 +404,23 @@ class BaseMultiWorkerStreamTestCase(unittest.HomeserverTestCase):
         fake one.
         """
         clients = self.reactor.tcpClients
-        self.assertEqual(len(clients), 1)
-        (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
-        self.assertEqual(host, "localhost")
-        self.assertEqual(port, 6379)
+        while clients:
+            (host, port, client_factory, _timeout, _bindAddress) = clients.pop(0)
+            self.assertEqual(host, "localhost")
+            self.assertEqual(port, 6379)
 
-        client_protocol = client_factory.buildProtocol(None)
-        server_protocol = self._redis_server.buildProtocol(None)
+            client_protocol = client_factory.buildProtocol(None)
+            server_protocol = self._redis_server.buildProtocol(None)
 
-        client_to_server_transport = FakeTransport(
-            server_protocol, self.reactor, client_protocol
-        )
-        client_protocol.makeConnection(client_to_server_transport)
-
-        server_to_client_transport = FakeTransport(
-            client_protocol, self.reactor, server_protocol
-        )
-        server_protocol.makeConnection(server_to_client_transport)
+            client_to_server_transport = FakeTransport(
+                server_protocol, self.reactor, client_protocol
+            )
+            client_protocol.makeConnection(client_to_server_transport)
 
-        return client_to_server_transport, server_to_client_transport
+            server_to_client_transport = FakeTransport(
+                client_protocol, self.reactor, server_protocol
+            )
+            server_protocol.makeConnection(server_to_client_transport)
 
 
 class TestReplicationDataHandler(GenericWorkerReplicationHandler):
@@ -624,6 +625,12 @@ class FakeRedisPubSubProtocol(Protocol):
             (channel,) = args
             self._server.add_subscriber(self)
             self.send(["subscribe", channel, 1])
+
+        # Since we use SET/GET to cache things we can safely no-op them.
+        elif command == b"SET":
+            self.send("OK")
+        elif command == b"GET":
+            self.send(None)
         else:
             raise Exception("Unknown command")
 
@@ -645,6 +652,8 @@ class FakeRedisPubSubProtocol(Protocol):
             # We assume bytes are just unicode strings.
             obj = obj.decode("utf-8")
 
+        if obj is None:
+            return "$-1\r\n"
         if isinstance(obj, str):
             return "${len}\r\n{str}\r\n".format(len=len(obj), str=obj)
         if isinstance(obj, int):
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index a0f32c5512..7c47aa7e0a 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -1180,6 +1180,21 @@ class RoomTestCase(unittest.HomeserverTestCase):
         )
         self.assertEqual(channel.json_body["total"], 3)
 
+    def test_room_state(self):
+        """Test that room state can be requested correctly"""
+        # Create two test rooms
+        room_id = self.helper.create_room_as(self.admin_user, tok=self.admin_user_tok)
+
+        url = "/_synapse/admin/v1/rooms/%s/state" % (room_id,)
+        channel = self.make_request(
+            "GET", url.encode("ascii"), access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertIn("state", channel.json_body)
+        # testing that the state events match is painful and not done here. We assume that
+        # the create_room already does the right thing, so no need to verify that we got
+        # the state events it created.
+
 
 class JoinAliasRoomTestCase(unittest.HomeserverTestCase):
 
diff --git a/tests/rest/admin/test_user.py b/tests/rest/admin/test_user.py
index 04599c2fcf..ee05ee60bc 100644
--- a/tests/rest/admin/test_user.py
+++ b/tests/rest/admin/test_user.py
@@ -28,6 +28,7 @@ from synapse.api.errors import Codes, HttpResponseException, ResourceLimitError
 from synapse.api.room_versions import RoomVersions
 from synapse.rest.client.v1 import login, logout, profile, room
 from synapse.rest.client.v2_alpha import devices, sync
+from synapse.types import JsonDict
 
 from tests import unittest
 from tests.test_utils import make_awaitable
@@ -468,13 +469,6 @@ class UsersListTestCase(unittest.HomeserverTestCase):
         self.admin_user = self.register_user("admin", "pass", admin=True)
         self.admin_user_tok = self.login("admin", "pass")
 
-        self.user1 = self.register_user(
-            "user1", "pass1", admin=False, displayname="Name 1"
-        )
-        self.user2 = self.register_user(
-            "user2", "pass2", admin=False, displayname="Name 2"
-        )
-
     def test_no_auth(self):
         """
         Try to list users without authentication.
@@ -488,6 +482,7 @@ class UsersListTestCase(unittest.HomeserverTestCase):
         """
         If the user is not a server admin, an error is returned.
         """
+        self._create_users(1)
         other_user_token = self.login("user1", "pass1")
 
         channel = self.make_request("GET", self.url, access_token=other_user_token)
@@ -499,6 +494,8 @@ class UsersListTestCase(unittest.HomeserverTestCase):
         """
         List all users, including deactivated users.
         """
+        self._create_users(2)
+
         channel = self.make_request(
             "GET",
             self.url + "?deactivated=true",
@@ -511,14 +508,7 @@ class UsersListTestCase(unittest.HomeserverTestCase):
         self.assertEqual(3, channel.json_body["total"])
 
         # Check that all fields are available
-        for u in channel.json_body["users"]:
-            self.assertIn("name", u)
-            self.assertIn("is_guest", u)
-            self.assertIn("admin", u)
-            self.assertIn("user_type", u)
-            self.assertIn("deactivated", u)
-            self.assertIn("displayname", u)
-            self.assertIn("avatar_url", u)
+        self._check_fields(channel.json_body["users"])
 
     def test_search_term(self):
         """Test that searching for a users works correctly"""
@@ -549,6 +539,7 @@ class UsersListTestCase(unittest.HomeserverTestCase):
 
             # Check that users were returned
             self.assertTrue("users" in channel.json_body)
+            self._check_fields(channel.json_body["users"])
             users = channel.json_body["users"]
 
             # Check that the expected number of users were returned
@@ -561,25 +552,30 @@ class UsersListTestCase(unittest.HomeserverTestCase):
                 u = users[0]
                 self.assertEqual(expected_user_id, u["name"])
 
+        self._create_users(2)
+
+        user1 = "@user1:test"
+        user2 = "@user2:test"
+
         # Perform search tests
-        _search_test(self.user1, "er1")
-        _search_test(self.user1, "me 1")
+        _search_test(user1, "er1")
+        _search_test(user1, "me 1")
 
-        _search_test(self.user2, "er2")
-        _search_test(self.user2, "me 2")
+        _search_test(user2, "er2")
+        _search_test(user2, "me 2")
 
-        _search_test(self.user1, "er1", "user_id")
-        _search_test(self.user2, "er2", "user_id")
+        _search_test(user1, "er1", "user_id")
+        _search_test(user2, "er2", "user_id")
 
         # Test case insensitive
-        _search_test(self.user1, "ER1")
-        _search_test(self.user1, "NAME 1")
+        _search_test(user1, "ER1")
+        _search_test(user1, "NAME 1")
 
-        _search_test(self.user2, "ER2")
-        _search_test(self.user2, "NAME 2")
+        _search_test(user2, "ER2")
+        _search_test(user2, "NAME 2")
 
-        _search_test(self.user1, "ER1", "user_id")
-        _search_test(self.user2, "ER2", "user_id")
+        _search_test(user1, "ER1", "user_id")
+        _search_test(user2, "ER2", "user_id")
 
         _search_test(None, "foo")
         _search_test(None, "bar")
@@ -587,6 +583,179 @@ class UsersListTestCase(unittest.HomeserverTestCase):
         _search_test(None, "foo", "user_id")
         _search_test(None, "bar", "user_id")
 
+    def test_invalid_parameter(self):
+        """
+        If parameters are invalid, an error is returned.
+        """
+
+        # negative limit
+        channel = self.make_request(
+            "GET", self.url + "?limit=-5", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.INVALID_PARAM, channel.json_body["errcode"])
+
+        # negative from
+        channel = self.make_request(
+            "GET", self.url + "?from=-5", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.INVALID_PARAM, channel.json_body["errcode"])
+
+        # invalid guests
+        channel = self.make_request(
+            "GET", self.url + "?guests=not_bool", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.UNKNOWN, channel.json_body["errcode"])
+
+        # invalid deactivated
+        channel = self.make_request(
+            "GET", self.url + "?deactivated=not_bool", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(400, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.UNKNOWN, channel.json_body["errcode"])
+
+    def test_limit(self):
+        """
+        Testing list of users with limit
+        """
+
+        number_users = 20
+        # Create one less user (since there's already an admin user).
+        self._create_users(number_users - 1)
+
+        channel = self.make_request(
+            "GET", self.url + "?limit=5", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(len(channel.json_body["users"]), 5)
+        self.assertEqual(channel.json_body["next_token"], "5")
+        self._check_fields(channel.json_body["users"])
+
+    def test_from(self):
+        """
+        Testing list of users with a defined starting point (from)
+        """
+
+        number_users = 20
+        # Create one less user (since there's already an admin user).
+        self._create_users(number_users - 1)
+
+        channel = self.make_request(
+            "GET", self.url + "?from=5", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(len(channel.json_body["users"]), 15)
+        self.assertNotIn("next_token", channel.json_body)
+        self._check_fields(channel.json_body["users"])
+
+    def test_limit_and_from(self):
+        """
+        Testing list of users with a defined starting point and limit
+        """
+
+        number_users = 20
+        # Create one less user (since there's already an admin user).
+        self._create_users(number_users - 1)
+
+        channel = self.make_request(
+            "GET", self.url + "?from=5&limit=10", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(channel.json_body["next_token"], "15")
+        self.assertEqual(len(channel.json_body["users"]), 10)
+        self._check_fields(channel.json_body["users"])
+
+    def test_next_token(self):
+        """
+        Testing that `next_token` appears at the right place
+        """
+
+        number_users = 20
+        # Create one less user (since there's already an admin user).
+        self._create_users(number_users - 1)
+
+        #  `next_token` does not appear
+        # Number of results is the number of entries
+        channel = self.make_request(
+            "GET", self.url + "?limit=20", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(len(channel.json_body["users"]), number_users)
+        self.assertNotIn("next_token", channel.json_body)
+
+        #  `next_token` does not appear
+        # Number of max results is larger than the number of entries
+        channel = self.make_request(
+            "GET", self.url + "?limit=21", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(len(channel.json_body["users"]), number_users)
+        self.assertNotIn("next_token", channel.json_body)
+
+        #  `next_token` does appear
+        # Number of max results is smaller than the number of entries
+        channel = self.make_request(
+            "GET", self.url + "?limit=19", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(len(channel.json_body["users"]), 19)
+        self.assertEqual(channel.json_body["next_token"], "19")
+
+        # Check
+        # Set `from` to value of `next_token` for request remaining entries
+        #  `next_token` does not appear
+        channel = self.make_request(
+            "GET", self.url + "?from=19", access_token=self.admin_user_tok,
+        )
+
+        self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(channel.json_body["total"], number_users)
+        self.assertEqual(len(channel.json_body["users"]), 1)
+        self.assertNotIn("next_token", channel.json_body)
+
+    def _check_fields(self, content: JsonDict):
+        """Checks that the expected user attributes are present in content
+        Args:
+            content: List that is checked for content
+        """
+        for u in content:
+            self.assertIn("name", u)
+            self.assertIn("is_guest", u)
+            self.assertIn("admin", u)
+            self.assertIn("user_type", u)
+            self.assertIn("deactivated", u)
+            self.assertIn("displayname", u)
+            self.assertIn("avatar_url", u)
+
+    def _create_users(self, number_users: int):
+        """
+        Create a number of users
+        Args:
+            number_users: Number of users to be created
+        """
+        for i in range(1, number_users + 1):
+            self.register_user(
+                "user%d" % i, "pass%d" % i, admin=False, displayname="Name %d" % i,
+            )
+
 
 class DeactivateAccountTestCase(unittest.HomeserverTestCase):
 
@@ -2211,3 +2380,67 @@ class WhoisRestTestCase(unittest.HomeserverTestCase):
         self.assertEqual(200, channel.code, msg=channel.json_body)
         self.assertEqual(self.other_user, channel.json_body["user_id"])
         self.assertIn("devices", channel.json_body)
+
+
+class ShadowBanRestTestCase(unittest.HomeserverTestCase):
+
+    servlets = [
+        synapse.rest.admin.register_servlets,
+        login.register_servlets,
+    ]
+
+    def prepare(self, reactor, clock, hs):
+        self.store = hs.get_datastore()
+
+        self.admin_user = self.register_user("admin", "pass", admin=True)
+        self.admin_user_tok = self.login("admin", "pass")
+
+        self.other_user = self.register_user("user", "pass")
+
+        self.url = "/_synapse/admin/v1/users/%s/shadow_ban" % urllib.parse.quote(
+            self.other_user
+        )
+
+    def test_no_auth(self):
+        """
+        Try to get information of an user without authentication.
+        """
+        channel = self.make_request("POST", self.url)
+        self.assertEqual(401, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.MISSING_TOKEN, channel.json_body["errcode"])
+
+    def test_requester_is_not_admin(self):
+        """
+        If the user is not a server admin, an error is returned.
+        """
+        other_user_token = self.login("user", "pass")
+
+        channel = self.make_request("POST", self.url, access_token=other_user_token)
+        self.assertEqual(403, int(channel.result["code"]), msg=channel.result["body"])
+        self.assertEqual(Codes.FORBIDDEN, channel.json_body["errcode"])
+
+    def test_user_is_not_local(self):
+        """
+        Tests that shadow-banning for a user that is not a local returns a 400
+        """
+        url = "/_synapse/admin/v1/whois/@unknown_person:unknown_domain"
+
+        channel = self.make_request("POST", url, access_token=self.admin_user_tok)
+        self.assertEqual(400, channel.code, msg=channel.json_body)
+
+    def test_success(self):
+        """
+        Shadow-banning should succeed for an admin.
+        """
+        # The user starts off as not shadow-banned.
+        other_user_token = self.login("user", "pass")
+        result = self.get_success(self.store.get_user_by_access_token(other_user_token))
+        self.assertFalse(result.shadow_banned)
+
+        channel = self.make_request("POST", self.url, access_token=self.admin_user_tok)
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual({}, channel.json_body)
+
+        # Ensure the user is shadow-banned (and the cache was cleared).
+        result = self.get_success(self.store.get_user_by_access_token(other_user_token))
+        self.assertTrue(result.shadow_banned)
diff --git a/tests/rest/client/test_shadow_banned.py b/tests/rest/client/test_shadow_banned.py
index e689c3fbea..0ebdf1415b 100644
--- a/tests/rest/client/test_shadow_banned.py
+++ b/tests/rest/client/test_shadow_banned.py
@@ -18,6 +18,7 @@ import synapse.rest.admin
 from synapse.api.constants import EventTypes
 from synapse.rest.client.v1 import directory, login, profile, room
 from synapse.rest.client.v2_alpha import room_upgrade_rest_servlet
+from synapse.types import UserID
 
 from tests import unittest
 
@@ -31,12 +32,7 @@ class _ShadowBannedBase(unittest.HomeserverTestCase):
         self.store = self.hs.get_datastore()
 
         self.get_success(
-            self.store.db_pool.simple_update(
-                table="users",
-                keyvalues={"name": self.banned_user_id},
-                updatevalues={"shadow_banned": True},
-                desc="shadow_ban",
-            )
+            self.store.set_shadow_banned(UserID.from_string(self.banned_user_id), True)
         )
 
         self.other_user_id = self.register_user("otheruser", "pass")
diff --git a/tests/rest/client/v1/test_login.py b/tests/rest/client/v1/test_login.py
index 2d25490374..66dfdaffbc 100644
--- a/tests/rest/client/v1/test_login.py
+++ b/tests/rest/client/v1/test_login.py
@@ -29,8 +29,7 @@ from synapse.appservice import ApplicationService
 from synapse.rest.client.v1 import login, logout
 from synapse.rest.client.v2_alpha import devices, register
 from synapse.rest.client.v2_alpha.account import WhoamiRestServlet
-from synapse.rest.synapse.client.pick_idp import PickIdpResource
-from synapse.rest.synapse.client.pick_username import pick_username_resource
+from synapse.rest.synapse.client import build_synapse_client_resource_tree
 from synapse.types import create_requester
 
 from tests import unittest
@@ -75,6 +74,10 @@ TEST_CLIENT_REDIRECT_URL = 'https://x?<ab c>&q"+%3D%2B"="fö%26=o"'
 # the query params in TEST_CLIENT_REDIRECT_URL
 EXPECTED_CLIENT_REDIRECT_URL_PARAMS = [("<ab c>", ""), ('q" =+"', '"fö&=o"')]
 
+# (possibly experimental) login flows we expect to appear in the list after the normal
+# ones
+ADDITIONAL_LOGIN_FLOWS = [{"type": "uk.half-shot.msc2778.login.application_service"}]
+
 
 class LoginRestServletTestCase(unittest.HomeserverTestCase):
 
@@ -419,13 +422,61 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
         return config
 
     def create_resource_dict(self) -> Dict[str, Resource]:
-        from synapse.rest.oidc import OIDCResource
-
         d = super().create_resource_dict()
-        d["/_synapse/client/pick_idp"] = PickIdpResource(self.hs)
-        d["/_synapse/oidc"] = OIDCResource(self.hs)
+        d.update(build_synapse_client_resource_tree(self.hs))
         return d
 
+    def test_get_login_flows(self):
+        """GET /login should return password and SSO flows"""
+        channel = self.make_request("GET", "/_matrix/client/r0/login")
+        self.assertEqual(channel.code, 200, channel.result)
+
+        expected_flows = [
+            {"type": "m.login.cas"},
+            {"type": "m.login.sso"},
+            {"type": "m.login.token"},
+            {"type": "m.login.password"},
+        ] + ADDITIONAL_LOGIN_FLOWS
+
+        self.assertCountEqual(channel.json_body["flows"], expected_flows)
+
+    @override_config({"experimental_features": {"msc2858_enabled": True}})
+    def test_get_msc2858_login_flows(self):
+        """The SSO flow should include IdP info if MSC2858 is enabled"""
+        channel = self.make_request("GET", "/_matrix/client/r0/login")
+        self.assertEqual(channel.code, 200, channel.result)
+
+        # stick the flows results in a dict by type
+        flow_results = {}  # type: Dict[str, Any]
+        for f in channel.json_body["flows"]:
+            flow_type = f["type"]
+            self.assertNotIn(
+                flow_type, flow_results, "duplicate flow type %s" % (flow_type,)
+            )
+            flow_results[flow_type] = f
+
+        self.assertIn("m.login.sso", flow_results, "m.login.sso was not returned")
+        sso_flow = flow_results.pop("m.login.sso")
+        # we should have a set of IdPs
+        self.assertCountEqual(
+            sso_flow["org.matrix.msc2858.identity_providers"],
+            [
+                {"id": "cas", "name": "CAS"},
+                {"id": "saml", "name": "SAML"},
+                {"id": "oidc-idp1", "name": "IDP1"},
+                {"id": "oidc", "name": "OIDC"},
+            ],
+        )
+
+        # the rest of the flows are simple
+        expected_flows = [
+            {"type": "m.login.cas"},
+            {"type": "m.login.token"},
+            {"type": "m.login.password"},
+        ] + ADDITIONAL_LOGIN_FLOWS
+
+        self.assertCountEqual(flow_results.values(), expected_flows)
+
     def test_multi_sso_redirect(self):
         """/login/sso/redirect should redirect to an identity picker"""
         # first hit the redirect url, which should redirect to our idp picker
@@ -446,7 +497,7 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
         p.feed(channel.result["body"].decode("utf-8"))
         p.close()
 
-        self.assertCountEqual(p.radios["idp"], ["cas", "oidc", "idp1", "saml"])
+        self.assertCountEqual(p.radios["idp"], ["cas", "oidc", "oidc-idp1", "saml"])
 
         self.assertEqual(p.hiddens["redirectUrl"], TEST_CLIENT_REDIRECT_URL)
 
@@ -564,6 +615,43 @@ class MultiSSOTestCase(unittest.HomeserverTestCase):
         )
         self.assertEqual(channel.code, 400, channel.result)
 
+    def test_client_idp_redirect_msc2858_disabled(self):
+        """If the client tries to pick an IdP but MSC2858 is disabled, return a 400"""
+        channel = self.make_request(
+            "GET",
+            "/_matrix/client/unstable/org.matrix.msc2858/login/sso/redirect/oidc?redirectUrl="
+            + urllib.parse.quote_plus(TEST_CLIENT_REDIRECT_URL),
+        )
+        self.assertEqual(channel.code, 400, channel.result)
+        self.assertEqual(channel.json_body["errcode"], "M_UNRECOGNIZED")
+
+    @override_config({"experimental_features": {"msc2858_enabled": True}})
+    def test_client_idp_redirect_to_unknown(self):
+        """If the client tries to pick an unknown IdP, return a 404"""
+        channel = self.make_request(
+            "GET",
+            "/_matrix/client/unstable/org.matrix.msc2858/login/sso/redirect/xxx?redirectUrl="
+            + urllib.parse.quote_plus(TEST_CLIENT_REDIRECT_URL),
+        )
+        self.assertEqual(channel.code, 404, channel.result)
+        self.assertEqual(channel.json_body["errcode"], "M_NOT_FOUND")
+
+    @override_config({"experimental_features": {"msc2858_enabled": True}})
+    def test_client_idp_redirect_to_oidc(self):
+        """If the client pick a known IdP, redirect to it"""
+        channel = self.make_request(
+            "GET",
+            "/_matrix/client/unstable/org.matrix.msc2858/login/sso/redirect/oidc?redirectUrl="
+            + urllib.parse.quote_plus(TEST_CLIENT_REDIRECT_URL),
+        )
+
+        self.assertEqual(channel.code, 302, channel.result)
+        oidc_uri = channel.headers.getRawHeaders("Location")[0]
+        oidc_uri_path, oidc_uri_query = oidc_uri.split("?", 1)
+
+        # it should redirect us to the auth page of the OIDC server
+        self.assertEqual(oidc_uri_path, TEST_OIDC_AUTH_ENDPOINT)
+
     @staticmethod
     def _get_value_from_macaroon(macaroon: pymacaroons.Macaroon, key: str) -> str:
         prefix = key + " = "
@@ -1119,11 +1207,8 @@ class UsernamePickerTestCase(HomeserverTestCase):
         return config
 
     def create_resource_dict(self) -> Dict[str, Resource]:
-        from synapse.rest.oidc import OIDCResource
-
         d = super().create_resource_dict()
-        d["/_synapse/client/pick_username"] = pick_username_resource(self.hs)
-        d["/_synapse/oidc"] = OIDCResource(self.hs)
+        d.update(build_synapse_client_resource_tree(self.hs))
         return d
 
     def test_username_picker(self):
@@ -1137,7 +1222,7 @@ class UsernamePickerTestCase(HomeserverTestCase):
         # that should redirect to the username picker
         self.assertEqual(channel.code, 302, channel.result)
         picker_url = channel.headers.getRawHeaders("Location")[0]
-        self.assertEqual(picker_url, "/_synapse/client/pick_username")
+        self.assertEqual(picker_url, "/_synapse/client/pick_username/account_details")
 
         # ... with a username_mapping_session cookie
         cookies = {}  # type: Dict[str,str]
@@ -1161,12 +1246,11 @@ class UsernamePickerTestCase(HomeserverTestCase):
         self.assertApproximates(session.expiry_time_ms, expected_expiry, tolerance=1000)
 
         # Now, submit a username to the username picker, which should serve a redirect
-        # back to the client
-        submit_path = picker_url + "/submit"
+        # to the completion page
         content = urlencode({b"username": b"bobby"}).encode("utf8")
         chan = self.make_request(
             "POST",
-            path=submit_path,
+            path=picker_url,
             content=content,
             content_is_form=True,
             custom_headers=[
@@ -1178,6 +1262,16 @@ class UsernamePickerTestCase(HomeserverTestCase):
         )
         self.assertEqual(chan.code, 302, chan.result)
         location_headers = chan.headers.getRawHeaders("Location")
+
+        # send a request to the completion page, which should 302 to the client redirectUrl
+        chan = self.make_request(
+            "GET",
+            path=location_headers[0],
+            custom_headers=[("Cookie", "username_mapping_session=" + session_id)],
+        )
+        self.assertEqual(chan.code, 302, chan.result)
+        location_headers = chan.headers.getRawHeaders("Location")
+
         # ensure that the returned location matches the requested redirect URL
         path, query = location_headers[0].split("?", 1)
         self.assertEqual(path, "https://x")
diff --git a/tests/rest/client/v1/test_rooms.py b/tests/rest/client/v1/test_rooms.py
index d4e3165436..2548b3a80c 100644
--- a/tests/rest/client/v1/test_rooms.py
+++ b/tests/rest/client/v1/test_rooms.py
@@ -616,6 +616,41 @@ class RoomMemberStateTestCase(RoomBase):
         self.assertEquals(json.loads(content), channel.json_body)
 
 
+class RoomInviteRatelimitTestCase(RoomBase):
+    user_id = "@sid1:red"
+
+    servlets = [
+        admin.register_servlets,
+        profile.register_servlets,
+        room.register_servlets,
+    ]
+
+    @unittest.override_config(
+        {"rc_invites": {"per_room": {"per_second": 0.5, "burst_count": 3}}}
+    )
+    def test_invites_by_rooms_ratelimit(self):
+        """Tests that invites in a room are actually rate-limited."""
+        room_id = self.helper.create_room_as(self.user_id)
+
+        for i in range(3):
+            self.helper.invite(room_id, self.user_id, "@user-%s:red" % (i,))
+
+        self.helper.invite(room_id, self.user_id, "@user-4:red", expect_code=429)
+
+    @unittest.override_config(
+        {"rc_invites": {"per_user": {"per_second": 0.5, "burst_count": 3}}}
+    )
+    def test_invites_by_users_ratelimit(self):
+        """Tests that invites to a specific user are actually rate-limited."""
+
+        for i in range(3):
+            room_id = self.helper.create_room_as(self.user_id)
+            self.helper.invite(room_id, self.user_id, "@other-users:red")
+
+        room_id = self.helper.create_room_as(self.user_id)
+        self.helper.invite(room_id, self.user_id, "@other-users:red", expect_code=429)
+
+
 class RoomJoinRatelimitTestCase(RoomBase):
     user_id = "@sid1:red"
 
diff --git a/tests/rest/client/v2_alpha/test_account.py b/tests/rest/client/v2_alpha/test_account.py
index cb87b80e33..177dc476da 100644
--- a/tests/rest/client/v2_alpha/test_account.py
+++ b/tests/rest/client/v2_alpha/test_account.py
@@ -24,7 +24,7 @@ import pkg_resources
 
 import synapse.rest.admin
 from synapse.api.constants import LoginType, Membership
-from synapse.api.errors import Codes
+from synapse.api.errors import Codes, HttpResponseException
 from synapse.rest.client.v1 import login, room
 from synapse.rest.client.v2_alpha import account, register
 from synapse.rest.synapse.client.password_reset import PasswordResetSubmitTokenResource
@@ -112,6 +112,56 @@ class PasswordResetTestCase(unittest.HomeserverTestCase):
         # Assert we can't log in with the old password
         self.attempt_wrong_password_login("kermit", old_password)
 
+    @override_config({"rc_3pid_validation": {"burst_count": 3}})
+    def test_ratelimit_by_email(self):
+        """Test that we ratelimit /requestToken for the same email.
+        """
+        old_password = "monkey"
+        new_password = "kangeroo"
+
+        user_id = self.register_user("kermit", old_password)
+        self.login("kermit", old_password)
+
+        email = "test1@example.com"
+
+        # Add a threepid
+        self.get_success(
+            self.store.user_add_threepid(
+                user_id=user_id,
+                medium="email",
+                address=email,
+                validated_at=0,
+                added_at=0,
+            )
+        )
+
+        def reset(ip):
+            client_secret = "foobar"
+            session_id = self._request_token(email, client_secret, ip)
+
+            self.assertEquals(len(self.email_attempts), 1)
+            link = self._get_link_from_email()
+
+            self._validate_token(link)
+
+            self._reset_password(new_password, session_id, client_secret)
+
+            self.email_attempts.clear()
+
+        # We expect to be able to make three requests before getting rate
+        # limited.
+        #
+        # We change IPs to ensure that we're not being ratelimited due to the
+        # same IP
+        reset("127.0.0.1")
+        reset("127.0.0.2")
+        reset("127.0.0.3")
+
+        with self.assertRaises(HttpResponseException) as cm:
+            reset("127.0.0.4")
+
+        self.assertEqual(cm.exception.code, 429)
+
     def test_basic_password_reset_canonicalise_email(self):
         """Test basic password reset flow
         Request password reset with different spelling
@@ -239,13 +289,18 @@ class PasswordResetTestCase(unittest.HomeserverTestCase):
 
         self.assertIsNotNone(session_id)
 
-    def _request_token(self, email, client_secret):
+    def _request_token(self, email, client_secret, ip="127.0.0.1"):
         channel = self.make_request(
             "POST",
             b"account/password/email/requestToken",
             {"client_secret": client_secret, "email": email, "send_attempt": 1},
+            client_ip=ip,
         )
-        self.assertEquals(200, channel.code, channel.result)
+
+        if channel.code != 200:
+            raise HttpResponseException(
+                channel.code, channel.result["reason"], channel.result["body"],
+            )
 
         return channel.json_body["sid"]
 
@@ -509,6 +564,21 @@ class ThreepidEmailRestTestCase(unittest.HomeserverTestCase):
     def test_address_trim(self):
         self.get_success(self._add_email(" foo@test.bar ", "foo@test.bar"))
 
+    @override_config({"rc_3pid_validation": {"burst_count": 3}})
+    def test_ratelimit_by_ip(self):
+        """Tests that adding emails is ratelimited by IP
+        """
+
+        # We expect to be able to set three emails before getting ratelimited.
+        self.get_success(self._add_email("foo1@test.bar", "foo1@test.bar"))
+        self.get_success(self._add_email("foo2@test.bar", "foo2@test.bar"))
+        self.get_success(self._add_email("foo3@test.bar", "foo3@test.bar"))
+
+        with self.assertRaises(HttpResponseException) as cm:
+            self.get_success(self._add_email("foo4@test.bar", "foo4@test.bar"))
+
+        self.assertEqual(cm.exception.code, 429)
+
     def test_add_email_if_disabled(self):
         """Test adding email to profile when doing so is disallowed
         """
@@ -777,7 +847,11 @@ class ThreepidEmailRestTestCase(unittest.HomeserverTestCase):
             body["next_link"] = next_link
 
         channel = self.make_request("POST", b"account/3pid/email/requestToken", body,)
-        self.assertEquals(expect_code, channel.code, channel.result)
+
+        if channel.code != expect_code:
+            raise HttpResponseException(
+                channel.code, channel.result["reason"], channel.result["body"],
+            )
 
         return channel.json_body.get("sid")
 
@@ -823,10 +897,12 @@ class ThreepidEmailRestTestCase(unittest.HomeserverTestCase):
     def _add_email(self, request_email, expected_email):
         """Test adding an email to profile
         """
+        previous_email_attempts = len(self.email_attempts)
+
         client_secret = "foobar"
         session_id = self._request_token(request_email, client_secret)
 
-        self.assertEquals(len(self.email_attempts), 1)
+        self.assertEquals(len(self.email_attempts) - previous_email_attempts, 1)
         link = self._get_link_from_email()
 
         self._validate_token(link)
@@ -855,4 +931,6 @@ class ThreepidEmailRestTestCase(unittest.HomeserverTestCase):
 
         self.assertEqual(200, int(channel.result["code"]), msg=channel.result["body"])
         self.assertEqual("email", channel.json_body["threepids"][0]["medium"])
-        self.assertEqual(expected_email, channel.json_body["threepids"][0]["address"])
+
+        threepids = {threepid["address"] for threepid in channel.json_body["threepids"]}
+        self.assertIn(expected_email, threepids)
diff --git a/tests/rest/client/v2_alpha/test_auth.py b/tests/rest/client/v2_alpha/test_auth.py
index a6488a3d29..3f50c56745 100644
--- a/tests/rest/client/v2_alpha/test_auth.py
+++ b/tests/rest/client/v2_alpha/test_auth.py
@@ -22,7 +22,7 @@ from synapse.api.constants import LoginType
 from synapse.handlers.ui_auth.checkers import UserInteractiveAuthChecker
 from synapse.rest.client.v1 import login
 from synapse.rest.client.v2_alpha import auth, devices, register
-from synapse.rest.oidc import OIDCResource
+from synapse.rest.synapse.client import build_synapse_client_resource_tree
 from synapse.types import JsonDict, UserID
 
 from tests import unittest
@@ -173,9 +173,7 @@ class UIAuthTests(unittest.HomeserverTestCase):
 
     def create_resource_dict(self):
         resource_dict = super().create_resource_dict()
-        if HAS_OIDC:
-            # mount the OIDC resource at /_synapse/oidc
-            resource_dict["/_synapse/oidc"] = OIDCResource(self.hs)
+        resource_dict.update(build_synapse_client_resource_tree(self.hs))
         return resource_dict
 
     def prepare(self, reactor, clock, hs):
diff --git a/tests/rest/media/v1/test_media_storage.py b/tests/rest/media/v1/test_media_storage.py
index ae2b32b131..a6c6985173 100644
--- a/tests/rest/media/v1/test_media_storage.py
+++ b/tests/rest/media/v1/test_media_storage.py
@@ -202,7 +202,6 @@ class MediaRepoTests(unittest.HomeserverTestCase):
 
         config = self.default_config()
         config["media_store_path"] = self.media_store_path
-        config["thumbnail_requirements"] = {}
         config["max_image_pixels"] = 2000000
 
         provider_config = {
@@ -313,15 +312,39 @@ class MediaRepoTests(unittest.HomeserverTestCase):
         self.assertEqual(headers.getRawHeaders(b"Content-Disposition"), None)
 
     def test_thumbnail_crop(self):
+        """Test that a cropped remote thumbnail is available."""
         self._test_thumbnail(
             "crop", self.test_image.expected_cropped, self.test_image.expected_found
         )
 
     def test_thumbnail_scale(self):
+        """Test that a scaled remote thumbnail is available."""
         self._test_thumbnail(
             "scale", self.test_image.expected_scaled, self.test_image.expected_found
         )
 
+    def test_invalid_type(self):
+        """An invalid thumbnail type is never available."""
+        self._test_thumbnail("invalid", None, False)
+
+    @unittest.override_config(
+        {"thumbnail_sizes": [{"width": 32, "height": 32, "method": "scale"}]}
+    )
+    def test_no_thumbnail_crop(self):
+        """
+        Override the config to generate only scaled thumbnails, but request a cropped one.
+        """
+        self._test_thumbnail("crop", None, False)
+
+    @unittest.override_config(
+        {"thumbnail_sizes": [{"width": 32, "height": 32, "method": "crop"}]}
+    )
+    def test_no_thumbnail_scale(self):
+        """
+        Override the config to generate only cropped thumbnails, but request a scaled one.
+        """
+        self._test_thumbnail("scale", None, False)
+
     def _test_thumbnail(self, method, expected_body, expected_found):
         params = "?width=32&height=32&method=" + method
         channel = make_request(
diff --git a/tests/rest/test_well_known.py b/tests/rest/test_well_known.py
index 14de0921be..c5e44af9f7 100644
--- a/tests/rest/test_well_known.py
+++ b/tests/rest/test_well_known.py
@@ -40,12 +40,3 @@ class WellKnownTests(unittest.HomeserverTestCase):
                 "m.identity_server": {"base_url": "https://testis"},
             },
         )
-
-    def test_well_known_no_public_baseurl(self):
-        self.hs.config.public_baseurl = None
-
-        channel = self.make_request(
-            "GET", "/.well-known/matrix/client", shorthand=False
-        )
-
-        self.assertEqual(channel.code, 404)
diff --git a/tests/server.py b/tests/server.py
index 5a85d5fe7f..6419c445ec 100644
--- a/tests/server.py
+++ b/tests/server.py
@@ -47,6 +47,7 @@ class FakeChannel:
     site = attr.ib(type=Site)
     _reactor = attr.ib()
     result = attr.ib(type=dict, default=attr.Factory(dict))
+    _ip = attr.ib(type=str, default="127.0.0.1")
     _producer = None
 
     @property
@@ -120,7 +121,7 @@ class FakeChannel:
     def getPeer(self):
         # We give an address so that getClientIP returns a non null entry,
         # causing us to record the MAU
-        return address.IPv4Address("TCP", "127.0.0.1", 3423)
+        return address.IPv4Address("TCP", self._ip, 3423)
 
     def getHost(self):
         return None
@@ -196,6 +197,7 @@ def make_request(
     custom_headers: Optional[
         Iterable[Tuple[Union[bytes, str], Union[bytes, str]]]
     ] = None,
+    client_ip: str = "127.0.0.1",
 ) -> FakeChannel:
     """
     Make a web request using the given method, path and content, and render it
@@ -223,6 +225,9 @@ def make_request(
              will pump the reactor until the the renderer tells the channel the request
              is finished.
 
+        client_ip: The IP to use as the requesting IP. Useful for testing
+            ratelimiting.
+
     Returns:
         channel
     """
@@ -250,7 +255,7 @@ def make_request(
     if isinstance(content, str):
         content = content.encode("utf8")
 
-    channel = FakeChannel(site, reactor)
+    channel = FakeChannel(site, reactor, ip=client_ip)
 
     req = request(channel)
     req.content = BytesIO(content)
diff --git a/tests/test_preview.py b/tests/test_preview.py
index c19facc1cb..0c6cbbd921 100644
--- a/tests/test_preview.py
+++ b/tests/test_preview.py
@@ -261,3 +261,32 @@ class PreviewUrlTestCase(unittest.TestCase):
         html = ""
         og = decode_and_calc_og(html, "http://example.com/test.html")
         self.assertEqual(og, {})
+
+    def test_invalid_encoding(self):
+        """An invalid character encoding should be ignored and treated as UTF-8, if possible."""
+        html = """
+        <html>
+        <head><title>Foo</title></head>
+        <body>
+        Some text.
+        </body>
+        </html>
+        """
+        og = decode_and_calc_og(
+            html, "http://example.com/test.html", "invalid-encoding"
+        )
+        self.assertEqual(og, {"og:title": "Foo", "og:description": "Some text."})
+
+    def test_invalid_encoding2(self):
+        """A body which doesn't match the sent character encoding."""
+        # Note that this contains an invalid UTF-8 sequence in the title.
+        html = b"""
+        <html>
+        <head><title>\xff\xff Foo</title></head>
+        <body>
+        Some text.
+        </body>
+        </html>
+        """
+        og = decode_and_calc_og(html, "http://example.com/test.html")
+        self.assertEqual(og, {"og:title": "ÿÿ Foo", "og:description": "Some text."})
diff --git a/tests/unittest.py b/tests/unittest.py
index bbd295687c..767d5d6077 100644
--- a/tests/unittest.py
+++ b/tests/unittest.py
@@ -386,6 +386,7 @@ class HomeserverTestCase(TestCase):
         custom_headers: Optional[
             Iterable[Tuple[Union[bytes, str], Union[bytes, str]]]
         ] = None,
+        client_ip: str = "127.0.0.1",
     ) -> FakeChannel:
         """
         Create a SynapseRequest at the path using the method and containing the
@@ -410,6 +411,9 @@ class HomeserverTestCase(TestCase):
 
             custom_headers: (name, value) pairs to add as request headers
 
+            client_ip: The IP to use as the requesting IP. Useful for testing
+                ratelimiting.
+
         Returns:
             The FakeChannel object which stores the result of the request.
         """
@@ -426,6 +430,7 @@ class HomeserverTestCase(TestCase):
             content_is_form,
             await_result,
             custom_headers,
+            client_ip,
         )
 
     def setup_test_homeserver(self, *args, **kwargs):
diff --git a/tests/util/test_itertools.py b/tests/util/test_itertools.py
index 522c8061f9..1ef0af8e8f 100644
--- a/tests/util/test_itertools.py
+++ b/tests/util/test_itertools.py
@@ -92,3 +92,15 @@ class SortTopologically(TestCase):
         # Valid orderings are `[1, 3, 2, 4]` or `[1, 2, 3, 4]`, but we should
         # always get the same one.
         self.assertEqual(list(sorted_topologically([4, 3, 2, 1], graph)), [1, 2, 3, 4])
+
+    def test_duplicates(self):
+        "Test that a graph with duplicate edges work"
+        graph = {1: [], 2: [1, 1], 3: [2, 2], 4: [3]}  # type: Dict[int, List[int]]
+
+        self.assertEqual(list(sorted_topologically([4, 3, 2, 1], graph)), [1, 2, 3, 4])
+
+    def test_multiple_paths(self):
+        "Test that a graph with multiple paths between two nodes work"
+        graph = {1: [], 2: [1], 3: [2], 4: [3, 2, 1]}  # type: Dict[int, List[int]]
+
+        self.assertEqual(list(sorted_topologically([4, 3, 2, 1], graph)), [1, 2, 3, 4])
diff --git a/tests/utils.py b/tests/utils.py
index 977eeaf6ee..68033d7535 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -33,7 +33,6 @@ from synapse.api.room_versions import RoomVersions
 from synapse.config.database import DatabaseConnectionConfig
 from synapse.config.homeserver import HomeServerConfig
 from synapse.config.server import DEFAULT_ROOM_VERSION
-from synapse.http.server import HttpServer
 from synapse.logging.context import current_context, set_current_context
 from synapse.server import HomeServer
 from synapse.storage import DataStore
@@ -158,8 +157,8 @@ def default_config(name, parse=False):
             "local": {"per_second": 10000, "burst_count": 10000},
             "remote": {"per_second": 10000, "burst_count": 10000},
         },
+        "rc_3pid_validation": {"per_second": 10000, "burst_count": 10000},
         "saml2_enabled": False,
-        "public_baseurl": None,
         "default_identity_server": None,
         "key_refresh_interval": 24 * 60 * 60 * 1000,
         "old_signing_keys": {},
@@ -352,7 +351,7 @@ def mock_getRawHeaders(headers=None):
 
 
 # This is a mock /resource/ not an entire server
-class MockHttpResource(HttpServer):
+class MockHttpResource:
     def __init__(self, prefix=""):
         self.callbacks = []  # 3-tuple of method/pattern/function
         self.prefix = prefix
diff --git a/tox.ini b/tox.ini
index 5210e7b860..9ff70fe312 100644
--- a/tox.ini
+++ b/tox.ini
@@ -18,13 +18,16 @@ deps =
     # installed on that).
     #
     # anyway, make sure that we have a recent enough setuptools.
-    setuptools>=18.5
+    setuptools>=18.5 ; python_version >= '3.6'
+    setuptools>=18.5,<51.0.0 ; python_version < '3.6'
 
     # we also need a semi-recent version of pip, because old ones fail to
     # install the "enum34" dependency of cryptography.
-    pip>=10
+    pip>=10 ; python_version >= '3.6'
+    pip>=10,<21.0 ; python_version < '3.6'
 
-# directories/files we run the linters on
+# directories/files we run the linters on.
+# if you update this list, make sure to do the same in scripts-dev/lint.sh
 lint_targets =
     setup.py
     synapse
@@ -103,21 +106,16 @@ usedevelop=true
 [testenv:py35-old]
 skip_install=True
 deps =
-    # Ensure a version of setuptools that supports Python 3.5 is installed.
-    setuptools < 51.0.0
-
     # Old automat version for Twisted
     Automat == 0.3.0
-
     lxml
-    coverage
-    coverage-enable-subprocess==1.0
+    {[base]deps}
 
 commands =
     # Make all greater-thans equals so we test the oldest version of our direct
     # dependencies, but make the pyopenssl 17.0, which can work against an
     # OpenSSL 1.1 compiled cryptography (as older ones don't compile on Travis).
-    /bin/sh -c 'python -m synapse.python_dependencies | sed -e "s/>=/==/g" -e "s/psycopg2==2.6//" -e "s/pyopenssl==16.0.0/pyopenssl==17.0.0/" | xargs -d"\n" pip install'
+    /bin/sh -c 'python -m synapse.python_dependencies | sed -e "s/>=/==/g" -e "/psycopg2/d" -e "s/pyopenssl==16.0.0/pyopenssl==17.0.0/" | xargs -d"\n" pip install'
 
     # Install Synapse itself. This won't update any libraries.
     pip install -e ".[test]"
@@ -168,6 +166,8 @@ commands = {toxinidir}/scripts-dev/generate_sample_config --check
 skip_install = True
 deps =
     coverage
+    pip>=10 ; python_version >= '3.6'
+    pip>=10,<21.0 ; python_version < '3.6'
 commands=
     coverage combine
     coverage report