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-rw-r--r--synapse/api/constants.py2
-rw-r--r--synapse/api/ratelimiting.py8
-rw-r--r--synapse/app/_base.py2
-rw-r--r--synapse/app/complement_fork_starter.py4
-rw-r--r--synapse/app/generic_worker.py8
-rw-r--r--synapse/appservice/__init__.py16
-rw-r--r--synapse/appservice/api.py12
-rw-r--r--synapse/config/experimental.py6
-rw-r--r--synapse/config/logger.py2
-rw-r--r--synapse/config/oidc.py12
-rw-r--r--synapse/federation/federation_client.py130
-rw-r--r--synapse/federation/sender/__init__.py3
-rw-r--r--synapse/handlers/admin.py1
-rw-r--r--synapse/handlers/auth.py64
-rw-r--r--synapse/handlers/directory.py4
-rw-r--r--synapse/handlers/e2e_keys.py37
-rw-r--r--synapse/handlers/federation.py19
-rw-r--r--synapse/handlers/federation_event.py35
-rw-r--r--synapse/handlers/message.py61
-rw-r--r--synapse/handlers/oidc.py386
-rw-r--r--synapse/handlers/profile.py6
-rw-r--r--synapse/handlers/relations.py56
-rw-r--r--synapse/handlers/room.py184
-rw-r--r--synapse/handlers/sso.py71
-rw-r--r--synapse/http/client.py24
-rw-r--r--synapse/metrics/background_process_metrics.py6
-rw-r--r--synapse/module_api/__init__.py41
-rw-r--r--synapse/push/bulk_push_rule_evaluator.py123
-rw-r--r--synapse/res/templates/_base.html29
-rw-r--r--synapse/res/templates/account_previously_renewed.html18
-rw-r--r--synapse/res/templates/account_renewed.html18
-rw-r--r--synapse/res/templates/add_threepid.html22
-rw-r--r--synapse/res/templates/add_threepid_failure.html20
-rw-r--r--synapse/res/templates/add_threepid_success.html18
-rw-r--r--synapse/res/templates/auth_success.html28
-rw-r--r--synapse/res/templates/invalid_token.html17
-rw-r--r--synapse/res/templates/notice_expiry.html93
-rw-r--r--synapse/res/templates/notif_mail.html116
-rw-r--r--synapse/res/templates/password_reset.html19
-rw-r--r--synapse/res/templates/password_reset_confirmation.html14
-rw-r--r--synapse/res/templates/password_reset_failure.html14
-rw-r--r--synapse/res/templates/password_reset_success.html12
-rw-r--r--synapse/res/templates/recaptcha.html19
-rw-r--r--synapse/res/templates/registration.html21
-rw-r--r--synapse/res/templates/registration_failure.html12
-rw-r--r--synapse/res/templates/registration_success.html13
-rw-r--r--synapse/res/templates/registration_token.html16
-rw-r--r--synapse/res/templates/sso_account_deactivated.html49
-rw-r--r--synapse/res/templates/sso_auth_account_details.html372
-rw-r--r--synapse/res/templates/sso_auth_bad_user.html52
-rw-r--r--synapse/res/templates/sso_auth_confirm.html56
-rw-r--r--synapse/res/templates/sso_auth_success.html54
-rw-r--r--synapse/res/templates/sso_error.html34
-rw-r--r--synapse/res/templates/sso_login_idp_picker.html114
-rw-r--r--synapse/res/templates/sso_new_user_consent.html60
-rw-r--r--synapse/res/templates/sso_redirect_confirm.html75
-rw-r--r--synapse/res/templates/style.css29
-rw-r--r--synapse/res/templates/terms.html16
-rw-r--r--synapse/rest/client/capabilities.py5
-rw-r--r--synapse/rest/client/devices.py5
-rw-r--r--synapse/rest/client/login.py3
-rw-r--r--synapse/rest/client/login_token_request.py5
-rw-r--r--synapse/rest/client/room.py57
-rw-r--r--synapse/rest/client/room_batch.py7
-rw-r--r--synapse/rest/client/sync.py8
-rw-r--r--synapse/rest/client/versions.py2
-rw-r--r--synapse/rest/synapse/client/oidc/__init__.py4
-rw-r--r--synapse/rest/synapse/client/oidc/backchannel_logout_resource.py35
-rw-r--r--synapse/storage/databases/main/__init__.py13
-rw-r--r--synapse/storage/databases/main/appservice.py17
-rw-r--r--synapse/storage/databases/main/devices.py54
-rw-r--r--synapse/storage/databases/main/end_to_end_keys.py17
-rw-r--r--synapse/storage/databases/main/events.py61
-rw-r--r--synapse/storage/databases/main/push_rule.py15
-rw-r--r--synapse/storage/databases/main/registration.py177
-rw-r--r--synapse/storage/databases/main/relations.py47
-rw-r--r--synapse/storage/databases/main/roommember.py6
-rw-r--r--synapse/storage/databases/main/search.py372
-rw-r--r--synapse/storage/engines/postgres.py16
-rw-r--r--synapse/storage/engines/sqlite.py4
-rw-r--r--synapse/storage/schema/main/delta/73/10_update_sqlite_fts4_tokenizer.py62
-rw-r--r--synapse/storage/schema/main/delta/73/10login_tokens.sql35
-rw-r--r--synapse/util/caches/descriptors.py104
-rw-r--r--synapse/util/macaroons.py87
-rw-r--r--synapse/util/retryutils.py2
85 files changed, 2539 insertions, 1434 deletions
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index 44c5ffc6a5..bc04a0755b 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -125,6 +125,8 @@ class EventTypes:
     MSC2716_BATCH: Final = "org.matrix.msc2716.batch"
     MSC2716_MARKER: Final = "org.matrix.msc2716.marker"
 
+    Reaction: Final = "m.reaction"
+
 
 class ToDeviceEventTypes:
     RoomKeyRequest: Final = "m.room_key_request"
diff --git a/synapse/api/ratelimiting.py b/synapse/api/ratelimiting.py
index 044c7d4926..511790c7c5 100644
--- a/synapse/api/ratelimiting.py
+++ b/synapse/api/ratelimiting.py
@@ -343,6 +343,7 @@ class RequestRatelimiter:
         requester: Requester,
         update: bool = True,
         is_admin_redaction: bool = False,
+        n_actions: int = 1,
     ) -> None:
         """Ratelimits requests.
 
@@ -355,6 +356,8 @@ class RequestRatelimiter:
             is_admin_redaction: Whether this is a room admin/moderator
                 redacting an event. If so then we may apply different
                 ratelimits depending on config.
+            n_actions: Multiplier for the number of actions to apply to the
+                rate limiter at once.
 
         Raises:
             LimitExceededError if the request should be ratelimited
@@ -383,7 +386,9 @@ class RequestRatelimiter:
         if is_admin_redaction and self.admin_redaction_ratelimiter:
             # If we have separate config for admin redactions, use a separate
             # ratelimiter as to not have user_ids clash
-            await self.admin_redaction_ratelimiter.ratelimit(requester, update=update)
+            await self.admin_redaction_ratelimiter.ratelimit(
+                requester, update=update, n_actions=n_actions
+            )
         else:
             # Override rate and burst count per-user
             await self.request_ratelimiter.ratelimit(
@@ -391,4 +396,5 @@ class RequestRatelimiter:
                 rate_hz=messages_per_second,
                 burst_count=burst_count,
                 update=update,
+                n_actions=n_actions,
             )
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 000912e86e..a683ebf4cb 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -558,7 +558,7 @@ def reload_cache_config(config: HomeServerConfig) -> None:
             logger.warning(f)
     else:
         logger.debug(
-            "New cache config. Was:\n %s\nNow:\n",
+            "New cache config. Was:\n %s\nNow:\n %s",
             previous_cache_config.__dict__,
             config.caches.__dict__,
         )
diff --git a/synapse/app/complement_fork_starter.py b/synapse/app/complement_fork_starter.py
index b22f315453..8c0f4a57e7 100644
--- a/synapse/app/complement_fork_starter.py
+++ b/synapse/app/complement_fork_starter.py
@@ -55,13 +55,13 @@ import os
 import signal
 import sys
 from types import FrameType
-from typing import Any, Callable, List, Optional
+from typing import Any, Callable, Dict, List, Optional
 
 from twisted.internet.main import installReactor
 
 # a list of the original signal handlers, before we installed our custom ones.
 # We restore these in our child processes.
-_original_signal_handlers: dict[int, Any] = {}
+_original_signal_handlers: Dict[int, Any] = {}
 
 
 class ProxiedReactor:
diff --git a/synapse/app/generic_worker.py b/synapse/app/generic_worker.py
index 2a9f039367..cb5892f041 100644
--- a/synapse/app/generic_worker.py
+++ b/synapse/app/generic_worker.py
@@ -178,13 +178,13 @@ class KeyUploadServlet(RestServlet):
             # Proxy headers from the original request, such as the auth headers
             # (in case the access token is there) and the original IP /
             # User-Agent of the request.
-            headers = {
-                header: request.requestHeaders.getRawHeaders(header, [])
+            headers: Dict[bytes, List[bytes]] = {
+                header: list(request.requestHeaders.getRawHeaders(header, []))
                 for header in (b"Authorization", b"User-Agent")
             }
             # Add the previous hop to the X-Forwarded-For header.
-            x_forwarded_for = request.requestHeaders.getRawHeaders(
-                b"X-Forwarded-For", []
+            x_forwarded_for = list(
+                request.requestHeaders.getRawHeaders(b"X-Forwarded-For", [])
             )
             # we use request.client here, since we want the previous hop, not the
             # original client (as returned by request.getClientAddress()).
diff --git a/synapse/appservice/__init__.py b/synapse/appservice/__init__.py
index 0dfa00df44..500bdde3a9 100644
--- a/synapse/appservice/__init__.py
+++ b/synapse/appservice/__init__.py
@@ -172,12 +172,24 @@ class ApplicationService:
         Returns:
             True if this service would like to know about this room.
         """
-        member_list = await store.get_users_in_room(
+        # We can use `get_local_users_in_room(...)` here because an application service
+        # can only be interested in local users of the server it's on (ignore any remote
+        # users that might match the user namespace regex).
+        #
+        # In the future, we can consider re-using
+        # `store.get_app_service_users_in_room` which is very similar to this
+        # function but has a slightly worse performance than this because we
+        # have an early escape-hatch if we find a single user that the
+        # appservice is interested in. The juice would be worth the squeeze if
+        # `store.get_app_service_users_in_room` was used in more places besides
+        # an experimental MSC. But for now we can avoid doing more work and
+        # barely using it later.
+        local_user_ids = await store.get_local_users_in_room(
             room_id, on_invalidate=cache_context.invalidate
         )
 
         # check joined member events
-        for user_id in member_list:
+        for user_id in local_user_ids:
             if self.is_interested_in_user(user_id):
                 return True
         return False
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index fbac4375b0..60774b240d 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -123,7 +123,7 @@ class ApplicationServiceApi(SimpleHttpClient):
             response = await self.get_json(
                 uri,
                 {"access_token": service.hs_token},
-                headers={"Authorization": f"Bearer {service.hs_token}"},
+                headers={"Authorization": [f"Bearer {service.hs_token}"]},
             )
             if response is not None:  # just an empty json object
                 return True
@@ -147,7 +147,7 @@ class ApplicationServiceApi(SimpleHttpClient):
             response = await self.get_json(
                 uri,
                 {"access_token": service.hs_token},
-                headers={"Authorization": f"Bearer {service.hs_token}"},
+                headers={"Authorization": [f"Bearer {service.hs_token}"]},
             )
             if response is not None:  # just an empty json object
                 return True
@@ -190,7 +190,9 @@ class ApplicationServiceApi(SimpleHttpClient):
                 b"access_token": service.hs_token,
             }
             response = await self.get_json(
-                uri, args=args, headers={"Authorization": f"Bearer {service.hs_token}"}
+                uri,
+                args=args,
+                headers={"Authorization": [f"Bearer {service.hs_token}"]},
             )
             if not isinstance(response, list):
                 logger.warning(
@@ -230,7 +232,7 @@ class ApplicationServiceApi(SimpleHttpClient):
                 info = await self.get_json(
                     uri,
                     {"access_token": service.hs_token},
-                    headers={"Authorization": f"Bearer {service.hs_token}"},
+                    headers={"Authorization": [f"Bearer {service.hs_token}"]},
                 )
 
                 if not _is_valid_3pe_metadata(info):
@@ -327,7 +329,7 @@ class ApplicationServiceApi(SimpleHttpClient):
                 uri=uri,
                 json_body=body,
                 args={"access_token": service.hs_token},
-                headers={"Authorization": f"Bearer {service.hs_token}"},
+                headers={"Authorization": [f"Bearer {service.hs_token}"]},
             )
             if logger.isEnabledFor(logging.DEBUG):
                 logger.debug(
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index 4009add01d..d4b71d1673 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -98,6 +98,9 @@ class ExperimentalConfig(Config):
         # MSC3773: Thread notifications
         self.msc3773_enabled: bool = experimental.get("msc3773_enabled", False)
 
+        # MSC3664: Pushrules to match on related events
+        self.msc3664_enabled: bool = experimental.get("msc3664_enabled", False)
+
         # MSC3848: Introduce errcodes for specific event sending failures
         self.msc3848_enabled: bool = experimental.get("msc3848_enabled", False)
 
@@ -125,3 +128,6 @@ class ExperimentalConfig(Config):
         self.msc3886_endpoint: Optional[str] = experimental.get(
             "msc3886_endpoint", None
         )
+
+        # MSC3912: Relation-based redactions.
+        self.msc3912_enabled: bool = experimental.get("msc3912_enabled", False)
diff --git a/synapse/config/logger.py b/synapse/config/logger.py
index b62b3b9205..94d1150415 100644
--- a/synapse/config/logger.py
+++ b/synapse/config/logger.py
@@ -53,7 +53,7 @@ DEFAULT_LOG_CONFIG = Template(
 # Synapse also supports structured logging for machine readable logs which can
 # be ingested by ELK stacks. See [2] for details.
 #
-# [1]: https://docs.python.org/3.7/library/logging.config.html#configuration-dictionary-schema
+# [1]: https://docs.python.org/3/library/logging.config.html#configuration-dictionary-schema
 # [2]: https://matrix-org.github.io/synapse/latest/structured_logging.html
 
 version: 1
diff --git a/synapse/config/oidc.py b/synapse/config/oidc.py
index 5418a332da..0bd83f4010 100644
--- a/synapse/config/oidc.py
+++ b/synapse/config/oidc.py
@@ -123,6 +123,8 @@ OIDC_PROVIDER_CONFIG_SCHEMA = {
         "userinfo_endpoint": {"type": "string"},
         "jwks_uri": {"type": "string"},
         "skip_verification": {"type": "boolean"},
+        "backchannel_logout_enabled": {"type": "boolean"},
+        "backchannel_logout_ignore_sub": {"type": "boolean"},
         "user_profile_method": {
             "type": "string",
             "enum": ["auto", "userinfo_endpoint"],
@@ -292,6 +294,10 @@ def _parse_oidc_config_dict(
         token_endpoint=oidc_config.get("token_endpoint"),
         userinfo_endpoint=oidc_config.get("userinfo_endpoint"),
         jwks_uri=oidc_config.get("jwks_uri"),
+        backchannel_logout_enabled=oidc_config.get("backchannel_logout_enabled", False),
+        backchannel_logout_ignore_sub=oidc_config.get(
+            "backchannel_logout_ignore_sub", False
+        ),
         skip_verification=oidc_config.get("skip_verification", False),
         user_profile_method=oidc_config.get("user_profile_method", "auto"),
         allow_existing_users=oidc_config.get("allow_existing_users", False),
@@ -368,6 +374,12 @@ class OidcProviderConfig:
     # "openid" scope is used.
     jwks_uri: Optional[str]
 
+    # Whether Synapse should react to backchannel logouts
+    backchannel_logout_enabled: bool
+
+    # Whether Synapse should ignore the `sub` claim in backchannel logouts or not.
+    backchannel_logout_ignore_sub: bool
+
     # Whether to skip metadata verification
     skip_verification: bool
 
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index b220ab43fc..c4c0bc7315 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -80,6 +80,18 @@ PDU_RETRY_TIME_MS = 1 * 60 * 1000
 T = TypeVar("T")
 
 
+@attr.s(frozen=True, slots=True, auto_attribs=True)
+class PulledPduInfo:
+    """
+    A result object that stores the PDU and info about it like which homeserver we
+    pulled it from (`pull_origin`)
+    """
+
+    pdu: EventBase
+    # Which homeserver we pulled the PDU from
+    pull_origin: str
+
+
 class InvalidResponseError(RuntimeError):
     """Helper for _try_destination_list: indicates that the server returned a response
     we couldn't parse
@@ -114,7 +126,9 @@ class FederationClient(FederationBase):
         self.hostname = hs.hostname
         self.signing_key = hs.signing_key
 
-        self._get_pdu_cache: ExpiringCache[str, EventBase] = ExpiringCache(
+        # Cache mapping `event_id` to a tuple of the event itself and the `pull_origin`
+        # (which server we pulled the event from)
+        self._get_pdu_cache: ExpiringCache[str, Tuple[EventBase, str]] = ExpiringCache(
             cache_name="get_pdu_cache",
             clock=self._clock,
             max_len=1000,
@@ -352,11 +366,11 @@ class FederationClient(FederationBase):
     @tag_args
     async def get_pdu(
         self,
-        destinations: Iterable[str],
+        destinations: Collection[str],
         event_id: str,
         room_version: RoomVersion,
         timeout: Optional[int] = None,
-    ) -> Optional[EventBase]:
+    ) -> Optional[PulledPduInfo]:
         """Requests the PDU with given origin and ID from the remote home
         servers.
 
@@ -371,11 +385,11 @@ class FederationClient(FederationBase):
                 moving to the next destination. None indicates no timeout.
 
         Returns:
-            The requested PDU, or None if we were unable to find it.
+            The requested PDU wrapped in `PulledPduInfo`, or None if we were unable to find it.
         """
 
         logger.debug(
-            "get_pdu: event_id=%s from destinations=%s", event_id, destinations
+            "get_pdu(event_id=%s): from destinations=%s", event_id, destinations
         )
 
         # TODO: Rate limit the number of times we try and get the same event.
@@ -384,19 +398,25 @@ class FederationClient(FederationBase):
         # it gets persisted to the database), so we cache the results of the lookup.
         # Note that this is separate to the regular get_event cache which caches
         # events once they have been persisted.
-        event = self._get_pdu_cache.get(event_id)
+        get_pdu_cache_entry = self._get_pdu_cache.get(event_id)
 
+        event = None
+        pull_origin = None
+        if get_pdu_cache_entry:
+            event, pull_origin = get_pdu_cache_entry
         # If we don't see the event in the cache, go try to fetch it from the
         # provided remote federated destinations
-        if not event:
+        else:
             pdu_attempts = self.pdu_destination_tried.setdefault(event_id, {})
 
+            # TODO: We can probably refactor this to use `_try_destination_list`
             for destination in destinations:
                 now = self._clock.time_msec()
                 last_attempt = pdu_attempts.get(destination, 0)
                 if last_attempt + PDU_RETRY_TIME_MS > now:
                     logger.debug(
-                        "get_pdu: skipping destination=%s because we tried it recently last_attempt=%s and we only check every %s (now=%s)",
+                        "get_pdu(event_id=%s): skipping destination=%s because we tried it recently last_attempt=%s and we only check every %s (now=%s)",
+                        event_id,
                         destination,
                         last_attempt,
                         PDU_RETRY_TIME_MS,
@@ -411,43 +431,48 @@ class FederationClient(FederationBase):
                         room_version=room_version,
                         timeout=timeout,
                     )
+                    pull_origin = destination
 
                     pdu_attempts[destination] = now
 
                     if event:
                         # Prime the cache
-                        self._get_pdu_cache[event.event_id] = event
+                        self._get_pdu_cache[event.event_id] = (event, pull_origin)
 
                         # Now that we have an event, we can break out of this
                         # loop and stop asking other destinations.
                         break
 
+                except NotRetryingDestination as e:
+                    logger.info("get_pdu(event_id=%s): %s", event_id, e)
+                    continue
+                except FederationDeniedError:
+                    logger.info(
+                        "get_pdu(event_id=%s): Not attempting to fetch PDU from %s because the homeserver is not on our federation whitelist",
+                        event_id,
+                        destination,
+                    )
+                    continue
                 except SynapseError as e:
                     logger.info(
-                        "Failed to get PDU %s from %s because %s",
+                        "get_pdu(event_id=%s): Failed to get PDU from %s because %s",
                         event_id,
                         destination,
                         e,
                     )
                     continue
-                except NotRetryingDestination as e:
-                    logger.info(str(e))
-                    continue
-                except FederationDeniedError as e:
-                    logger.info(str(e))
-                    continue
                 except Exception as e:
                     pdu_attempts[destination] = now
 
                     logger.info(
-                        "Failed to get PDU %s from %s because %s",
+                        "get_pdu(event_id=%s): Failed to get PDU from %s because %s",
                         event_id,
                         destination,
                         e,
                     )
                     continue
 
-        if not event:
+        if not event or not pull_origin:
             return None
 
         # `event` now refers to an object stored in `get_pdu_cache`. Our
@@ -459,7 +484,7 @@ class FederationClient(FederationBase):
             event.room_version,
         )
 
-        return event_copy
+        return PulledPduInfo(event_copy, pull_origin)
 
     @trace
     @tag_args
@@ -699,12 +724,14 @@ class FederationClient(FederationBase):
         pdu_origin = get_domain_from_id(pdu.sender)
         if not res and pdu_origin != origin:
             try:
-                res = await self.get_pdu(
+                pulled_pdu_info = await self.get_pdu(
                     destinations=[pdu_origin],
                     event_id=pdu.event_id,
                     room_version=room_version,
                     timeout=10000,
                 )
+                if pulled_pdu_info is not None:
+                    res = pulled_pdu_info.pdu
             except SynapseError:
                 pass
 
@@ -806,6 +833,7 @@ class FederationClient(FederationBase):
             )
 
         for destination in destinations:
+            # We don't want to ask our own server for information we don't have
             if destination == self.server_name:
                 continue
 
@@ -814,9 +842,21 @@ class FederationClient(FederationBase):
             except (
                 RequestSendFailed,
                 InvalidResponseError,
-                NotRetryingDestination,
             ) as e:
                 logger.warning("Failed to %s via %s: %s", description, destination, e)
+                # Skip to the next homeserver in the list to try.
+                continue
+            except NotRetryingDestination as e:
+                logger.info("%s: %s", description, e)
+                continue
+            except FederationDeniedError:
+                logger.info(
+                    "%s: Not attempting to %s from %s because the homeserver is not on our federation whitelist",
+                    description,
+                    description,
+                    destination,
+                )
+                continue
             except UnsupportedRoomVersionError:
                 raise
             except HttpResponseException as e:
@@ -1609,6 +1649,54 @@ class FederationClient(FederationBase):
         return result
 
     async def timestamp_to_event(
+        self, *, destinations: List[str], room_id: str, timestamp: int, direction: str
+    ) -> Optional["TimestampToEventResponse"]:
+        """
+        Calls each remote federating server from `destinations` asking for their closest
+        event to the given timestamp in the given direction until we get a response.
+        Also validates the response to always return the expected keys or raises an
+        error.
+
+        Args:
+            destinations: The domains of homeservers to try fetching from
+            room_id: Room to fetch the event from
+            timestamp: The point in time (inclusive) we should navigate from in
+                the given direction to find the closest event.
+            direction: ["f"|"b"] to indicate whether we should navigate forward
+                or backward from the given timestamp to find the closest event.
+
+        Returns:
+            A parsed TimestampToEventResponse including the closest event_id
+            and origin_server_ts or None if no destination has a response.
+        """
+
+        async def _timestamp_to_event_from_destination(
+            destination: str,
+        ) -> TimestampToEventResponse:
+            return await self._timestamp_to_event_from_destination(
+                destination, room_id, timestamp, direction
+            )
+
+        try:
+            # Loop through each homeserver candidate until we get a succesful response
+            timestamp_to_event_response = await self._try_destination_list(
+                "timestamp_to_event",
+                destinations,
+                # TODO: The requested timestamp may lie in a part of the
+                #   event graph that the remote server *also* didn't have,
+                #   in which case they will have returned another event
+                #   which may be nowhere near the requested timestamp. In
+                #   the future, we may need to reconcile that gap and ask
+                #   other homeservers, and/or extend `/timestamp_to_event`
+                #   to return events on *both* sides of the timestamp to
+                #   help reconcile the gap faster.
+                _timestamp_to_event_from_destination,
+            )
+            return timestamp_to_event_response
+        except SynapseError:
+            return None
+
+    async def _timestamp_to_event_from_destination(
         self, destination: str, room_id: str, timestamp: int, direction: str
     ) -> "TimestampToEventResponse":
         """
diff --git a/synapse/federation/sender/__init__.py b/synapse/federation/sender/__init__.py
index 774ecd81b6..3ad483efe0 100644
--- a/synapse/federation/sender/__init__.py
+++ b/synapse/federation/sender/__init__.py
@@ -536,8 +536,7 @@ class FederationSender(AbstractFederationSender):
 
                 if event_entries:
                     now = self.clock.time_msec()
-                    last_id = next(reversed(event_ids))
-                    ts = event_to_received_ts[last_id]
+                    ts = max(t for t in event_to_received_ts.values() if t)
                     assert ts is not None
 
                     synapse.metrics.event_processing_lag.labels(
diff --git a/synapse/handlers/admin.py b/synapse/handlers/admin.py
index f2989cc4a2..5bf8e86387 100644
--- a/synapse/handlers/admin.py
+++ b/synapse/handlers/admin.py
@@ -100,6 +100,7 @@ class AdminHandler:
         user_info_dict["avatar_url"] = profile.avatar_url
         user_info_dict["threepids"] = threepids
         user_info_dict["external_ids"] = external_ids
+        user_info_dict["erased"] = await self.store.is_user_erased(user.to_string())
 
         return user_info_dict
 
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index f5f0e0e7a7..8b9ef25d29 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -38,6 +38,7 @@ from typing import (
 import attr
 import bcrypt
 import unpaddedbase64
+from prometheus_client import Counter
 
 from twisted.internet.defer import CancelledError
 from twisted.web.server import Request
@@ -48,6 +49,7 @@ from synapse.api.errors import (
     Codes,
     InteractiveAuthIncompleteError,
     LoginError,
+    NotFoundError,
     StoreError,
     SynapseError,
     UserDeactivatedError,
@@ -63,10 +65,14 @@ from synapse.http.server import finish_request, respond_with_html
 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.storage.databases.main.registration import (
+    LoginTokenExpired,
+    LoginTokenLookupResult,
+    LoginTokenReused,
+)
 from synapse.types import JsonDict, Requester, UserID
 from synapse.util import stringutils as stringutils
 from synapse.util.async_helpers import delay_cancellation, maybe_awaitable
-from synapse.util.macaroons import LoginTokenAttributes
 from synapse.util.msisdn import phone_number_to_msisdn
 from synapse.util.stringutils import base62_encode
 from synapse.util.threepids import canonicalise_email
@@ -80,6 +86,12 @@ logger = logging.getLogger(__name__)
 
 INVALID_USERNAME_OR_PASSWORD = "Invalid username or password"
 
+invalid_login_token_counter = Counter(
+    "synapse_user_login_invalid_login_tokens",
+    "Counts the number of rejected m.login.token on /login",
+    ["reason"],
+)
+
 
 def convert_client_dict_legacy_fields_to_identifier(
     submission: JsonDict,
@@ -883,6 +895,25 @@ class AuthHandler:
 
         return True
 
+    async def create_login_token_for_user_id(
+        self,
+        user_id: str,
+        duration_ms: int = (2 * 60 * 1000),
+        auth_provider_id: Optional[str] = None,
+        auth_provider_session_id: Optional[str] = None,
+    ) -> str:
+        login_token = self.generate_login_token()
+        now = self._clock.time_msec()
+        expiry_ts = now + duration_ms
+        await self.store.add_login_token_to_user(
+            user_id=user_id,
+            token=login_token,
+            expiry_ts=expiry_ts,
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
+        )
+        return login_token
+
     async def create_refresh_token_for_user_id(
         self,
         user_id: str,
@@ -1401,6 +1432,18 @@ class AuthHandler:
             return None
         return user_id
 
+    def generate_login_token(self) -> str:
+        """Generates an opaque string, for use as an short-term login token"""
+
+        # we use the following format for access tokens:
+        #    syl_<random string>_<base62 crc check>
+
+        random_string = stringutils.random_string(20)
+        base = f"syl_{random_string}"
+
+        crc = base62_encode(crc32(base.encode("ascii")), minwidth=6)
+        return f"{base}_{crc}"
+
     def generate_access_token(self, for_user: UserID) -> str:
         """Generates an opaque string, for use as an access token"""
 
@@ -1427,16 +1470,17 @@ class AuthHandler:
         crc = base62_encode(crc32(base.encode("ascii")), minwidth=6)
         return f"{base}_{crc}"
 
-    async def validate_short_term_login_token(
-        self, login_token: str
-    ) -> LoginTokenAttributes:
+    async def consume_login_token(self, login_token: str) -> LoginTokenLookupResult:
         try:
-            res = self.macaroon_gen.verify_short_term_login_token(login_token)
-        except Exception:
-            raise AuthError(403, "Invalid login token", errcode=Codes.FORBIDDEN)
+            return await self.store.consume_login_token(login_token)
+        except LoginTokenExpired:
+            invalid_login_token_counter.labels("expired").inc()
+        except LoginTokenReused:
+            invalid_login_token_counter.labels("reused").inc()
+        except NotFoundError:
+            invalid_login_token_counter.labels("not found").inc()
 
-        await self.auth_blocking.check_auth_blocking(res.user_id)
-        return res
+        raise AuthError(403, "Invalid login token", errcode=Codes.FORBIDDEN)
 
     async def delete_access_token(self, access_token: str) -> None:
         """Invalidate a single access token
@@ -1711,7 +1755,7 @@ class AuthHandler:
             )
 
         # Create a login token
-        login_token = self.macaroon_gen.generate_short_term_login_token(
+        login_token = await self.create_login_token_for_user_id(
             registered_user_id,
             auth_provider_id=auth_provider_id,
             auth_provider_session_id=auth_provider_session_id,
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
index d52ebada6b..2ea52257cb 100644
--- a/synapse/handlers/directory.py
+++ b/synapse/handlers/directory.py
@@ -85,7 +85,7 @@ class DirectoryHandler:
         # TODO(erikj): Add transactions.
         # TODO(erikj): Check if there is a current association.
         if not servers:
-            servers = await self._storage_controllers.state.get_current_hosts_in_room(
+            servers = await self._storage_controllers.state.get_current_hosts_in_room_or_partial_state_approximation(
                 room_id
             )
 
@@ -290,7 +290,7 @@ class DirectoryHandler:
                 Codes.NOT_FOUND,
             )
 
-        extra_servers = await self._storage_controllers.state.get_current_hosts_in_room(
+        extra_servers = await self._storage_controllers.state.get_current_hosts_in_room_or_partial_state_approximation(
             room_id
         )
         servers_set = set(extra_servers) | set(servers)
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index 09a2492afc..a9912c467d 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -49,6 +49,7 @@ logger = logging.getLogger(__name__)
 
 class E2eKeysHandler:
     def __init__(self, hs: "HomeServer"):
+        self.config = hs.config
         self.store = hs.get_datastores().main
         self.federation = hs.get_federation_client()
         self.device_handler = hs.get_device_handler()
@@ -431,13 +432,17 @@ class E2eKeysHandler:
     @trace
     @cancellable
     async def query_local_devices(
-        self, query: Mapping[str, Optional[List[str]]]
+        self,
+        query: Mapping[str, Optional[List[str]]],
+        include_displaynames: bool = True,
     ) -> Dict[str, Dict[str, dict]]:
         """Get E2E device keys for local users
 
         Args:
             query: map from user_id to a list
                  of devices to query (None for all devices)
+            include_displaynames: Whether to include device displaynames in the returned
+                device details.
 
         Returns:
             A map from user_id -> device_id -> device details
@@ -469,7 +474,9 @@ class E2eKeysHandler:
             # make sure that each queried user appears in the result dict
             result_dict[user_id] = {}
 
-        results = await self.store.get_e2e_device_keys_for_cs_api(local_query)
+        results = await self.store.get_e2e_device_keys_for_cs_api(
+            local_query, include_displaynames
+        )
 
         # Build the result structure
         for user_id, device_keys in results.items():
@@ -482,11 +489,33 @@ class E2eKeysHandler:
     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"""
+        """Handle a device key query from a federated server:
+
+        Handles the path: GET /_matrix/federation/v1/users/keys/query
+
+        Args:
+            query_body: The body of the query request. Should contain a key
+                "device_keys" that map to a dictionary of user ID's -> list of
+                device IDs. If the list of device IDs is empty, all devices of
+                that user will be queried.
+
+        Returns:
+            A json dictionary containing the following:
+                - device_keys: A dictionary containing the requested device information.
+                - master_keys: An optional dictionary of user ID -> master cross-signing
+                   key info.
+                - self_signing_key: An optional dictionary of user ID -> self-signing
+                    key info.
+        """
         device_keys_query: Dict[str, Optional[List[str]]] = query_body.get(
             "device_keys", {}
         )
-        res = await self.query_local_devices(device_keys_query)
+        res = await self.query_local_devices(
+            device_keys_query,
+            include_displaynames=(
+                self.config.federation.allow_device_name_lookup_over_federation
+            ),
+        )
         ret = {"device_keys": res}
 
         # add in the cross-signing keys
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 275a37a575..5fc3b8bc8c 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -442,6 +442,15 @@ class FederationHandler:
                     # appropriate stuff.
                     # TODO: We can probably do something more intelligent here.
                     return True
+                except NotRetryingDestination as e:
+                    logger.info("_maybe_backfill_inner: %s", e)
+                    continue
+                except FederationDeniedError:
+                    logger.info(
+                        "_maybe_backfill_inner: Not attempting to backfill from %s because the homeserver is not on our federation whitelist",
+                        dom,
+                    )
+                    continue
                 except (SynapseError, InvalidResponseError) as e:
                     logger.info("Failed to backfill from %s because %s", dom, e)
                     continue
@@ -477,15 +486,9 @@ class FederationHandler:
 
                     logger.info("Failed to backfill from %s because %s", dom, e)
                     continue
-                except NotRetryingDestination as e:
-                    logger.info(str(e))
-                    continue
                 except RequestSendFailed as e:
                     logger.info("Failed to get backfill from %s because %s", dom, e)
                     continue
-                except FederationDeniedError as e:
-                    logger.info(e)
-                    continue
                 except Exception as e:
                     logger.exception("Failed to backfill from %s because %s", dom, e)
                     continue
@@ -1017,7 +1020,9 @@ class FederationHandler:
 
         context = EventContext.for_outlier(self._storage_controllers)
 
-        await self._bulk_push_rule_evaluator.action_for_event_by_user(event, context)
+        await self._bulk_push_rule_evaluator.action_for_events_by_user(
+            [(event, context)]
+        )
         try:
             await self._federation_event_handler.persist_events_and_notify(
                 event.room_id, [(event, context)]
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index 06e41b5cc0..9ca5df7c78 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -58,7 +58,7 @@ from synapse.event_auth import (
 )
 from synapse.events import EventBase
 from synapse.events.snapshot import EventContext
-from synapse.federation.federation_client import InvalidResponseError
+from synapse.federation.federation_client import InvalidResponseError, PulledPduInfo
 from synapse.logging.context import nested_logging_context
 from synapse.logging.opentracing import (
     SynapseTags,
@@ -1517,8 +1517,8 @@ class FederationEventHandler:
         )
 
     async def backfill_event_id(
-        self, destination: str, room_id: str, event_id: str
-    ) -> EventBase:
+        self, destinations: List[str], room_id: str, event_id: str
+    ) -> PulledPduInfo:
         """Backfill a single event and persist it as a non-outlier which means
         we also pull in all of the state and auth events necessary for it.
 
@@ -1530,24 +1530,21 @@ class FederationEventHandler:
         Raises:
             FederationError if we are unable to find the event from the destination
         """
-        logger.info(
-            "backfill_event_id: event_id=%s from destination=%s", event_id, destination
-        )
+        logger.info("backfill_event_id: event_id=%s", event_id)
 
         room_version = await self._store.get_room_version(room_id)
 
-        event_from_response = await self._federation_client.get_pdu(
-            [destination],
+        pulled_pdu_info = await self._federation_client.get_pdu(
+            destinations,
             event_id,
             room_version,
         )
 
-        if not event_from_response:
+        if not pulled_pdu_info:
             raise FederationError(
                 "ERROR",
                 404,
-                "Unable to find event_id=%s from destination=%s to backfill."
-                % (event_id, destination),
+                f"Unable to find event_id={event_id} from remote servers to backfill.",
                 affected=event_id,
             )
 
@@ -1555,13 +1552,13 @@ class FederationEventHandler:
         # and auth events to de-outlier it. This also sets up the necessary
         # `state_groups` for the event.
         await self._process_pulled_events(
-            destination,
-            [event_from_response],
+            pulled_pdu_info.pull_origin,
+            [pulled_pdu_info.pdu],
             # Prevent notifications going to clients
             backfilled=True,
         )
 
-        return event_from_response
+        return pulled_pdu_info
 
     @trace
     @tag_args
@@ -1584,19 +1581,19 @@ class FederationEventHandler:
         async def get_event(event_id: str) -> None:
             with nested_logging_context(event_id):
                 try:
-                    event = await self._federation_client.get_pdu(
+                    pulled_pdu_info = await self._federation_client.get_pdu(
                         [destination],
                         event_id,
                         room_version,
                     )
-                    if event is None:
+                    if pulled_pdu_info is None:
                         logger.warning(
                             "Server %s didn't return event %s",
                             destination,
                             event_id,
                         )
                         return
-                    events.append(event)
+                    events.append(pulled_pdu_info.pdu)
 
                 except Exception as e:
                     logger.warning(
@@ -2171,8 +2168,8 @@ class FederationEventHandler:
                     min_depth,
                 )
             else:
-                await self._bulk_push_rule_evaluator.action_for_event_by_user(
-                    event, context
+                await self._bulk_push_rule_evaluator.action_for_events_by_user(
+                    [(event, context)]
                 )
 
         try:
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index cf8017b0db..fcfdaa074f 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -872,6 +872,36 @@ class EventCreationHandler:
                 return prev_event
         return None
 
+    async def get_event_from_transaction(
+        self,
+        requester: Requester,
+        txn_id: str,
+        room_id: str,
+    ) -> Optional[EventBase]:
+        """For the given transaction ID and room ID, check if there is a matching event.
+        If so, fetch it and return it.
+
+        Args:
+            requester: The requester making the request in the context of which we want
+                to fetch the event.
+            txn_id: The transaction ID.
+            room_id: The room ID.
+
+        Returns:
+            An event if one could be found, None otherwise.
+        """
+        if requester.access_token_id:
+            existing_event_id = await self.store.get_event_id_from_transaction_id(
+                room_id,
+                requester.user.to_string(),
+                requester.access_token_id,
+                txn_id,
+            )
+            if existing_event_id:
+                return await self.store.get_event(existing_event_id)
+
+        return None
+
     async def create_and_send_nonmember_event(
         self,
         requester: Requester,
@@ -951,18 +981,17 @@ class EventCreationHandler:
         # extremities to pile up, which in turn leads to state resolution
         # taking longer.
         async with self.limiter.queue(event_dict["room_id"]):
-            if txn_id and requester.access_token_id:
-                existing_event_id = await self.store.get_event_id_from_transaction_id(
-                    event_dict["room_id"],
-                    requester.user.to_string(),
-                    requester.access_token_id,
-                    txn_id,
+            if txn_id:
+                event = await self.get_event_from_transaction(
+                    requester, txn_id, event_dict["room_id"]
                 )
-                if existing_event_id:
-                    event = await self.store.get_event(existing_event_id)
+                if event:
                     # we know it was persisted, so must have a stream ordering
                     assert event.internal_metadata.stream_ordering
-                    return event, event.internal_metadata.stream_ordering
+                    return (
+                        event,
+                        event.internal_metadata.stream_ordering,
+                    )
 
             event, context = await self.create_event(
                 requester,
@@ -1421,17 +1450,9 @@ class EventCreationHandler:
             a room that has been un-partial stated.
         """
 
-        for event, context in events_and_context:
-            # Skip push notification actions for historical messages
-            # because we don't want to notify people about old history back in time.
-            # The historical messages also do not have the proper `context.current_state_ids`
-            # and `state_groups` because they have `prev_events` that aren't persisted yet
-            # (historical messages persisted in reverse-chronological order).
-            if not event.internal_metadata.is_historical():
-                with opentracing.start_active_span("calculate_push_actions"):
-                    await self._bulk_push_rule_evaluator.action_for_event_by_user(
-                        event, context
-                    )
+        await self._bulk_push_rule_evaluator.action_for_events_by_user(
+            events_and_context
+        )
 
         try:
             # If we're a worker we need to hit out to the master.
diff --git a/synapse/handlers/oidc.py b/synapse/handlers/oidc.py
index d7a8226900..867973dcca 100644
--- a/synapse/handlers/oidc.py
+++ b/synapse/handlers/oidc.py
@@ -12,14 +12,28 @@
 # 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 binascii
 import inspect
+import json
 import logging
-from typing import TYPE_CHECKING, Any, Dict, Generic, List, Optional, TypeVar, Union
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Dict,
+    Generic,
+    List,
+    Optional,
+    Type,
+    TypeVar,
+    Union,
+)
 from urllib.parse import urlencode, urlparse
 
 import attr
+import unpaddedbase64
 from authlib.common.security import generate_token
-from authlib.jose import JsonWebToken, jwt
+from authlib.jose import JsonWebToken, JWTClaims
+from authlib.jose.errors import InvalidClaimError, JoseError, MissingClaimError
 from authlib.oauth2.auth import ClientAuth
 from authlib.oauth2.rfc6749.parameters import prepare_grant_uri
 from authlib.oidc.core import CodeIDToken, UserInfo
@@ -35,9 +49,12 @@ from typing_extensions import TypedDict
 from twisted.web.client import readBody
 from twisted.web.http_headers import Headers
 
+from synapse.api.errors import SynapseError
 from synapse.config import ConfigError
 from synapse.config.oidc import OidcProviderClientSecretJwtKey, OidcProviderConfig
 from synapse.handlers.sso import MappingException, UserAttributes
+from synapse.http.server import finish_request
+from synapse.http.servlet import parse_string
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
 from synapse.types import JsonDict, UserID, map_username_to_mxid_localpart
@@ -88,6 +105,8 @@ class Token(TypedDict):
 #: there is no real point of doing this in our case.
 JWK = Dict[str, str]
 
+C = TypeVar("C")
+
 
 #: A JWK Set, as per RFC7517 sec 5.
 class JWKS(TypedDict):
@@ -247,6 +266,80 @@ class OidcHandler:
 
         await oidc_provider.handle_oidc_callback(request, session_data, code)
 
+    async def handle_backchannel_logout(self, request: SynapseRequest) -> None:
+        """Handle an incoming request to /_synapse/client/oidc/backchannel_logout
+
+        This extracts the logout_token from the request and tries to figure out
+        which OpenID Provider it is comming from. This works by matching the iss claim
+        with the issuer and the aud claim with the client_id.
+
+        Since at this point we don't know who signed the JWT, we can't just
+        decode it using authlib since it will always verifies the signature. We
+        have to decode it manually without validating the signature. The actual JWT
+        verification is done in the `OidcProvider.handler_backchannel_logout` method,
+        once we figured out which provider sent the request.
+
+        Args:
+            request: the incoming request from the browser.
+        """
+        logout_token = parse_string(request, "logout_token")
+        if logout_token is None:
+            raise SynapseError(400, "Missing logout_token in request")
+
+        # A JWT looks like this:
+        #    header.payload.signature
+        # where all parts are encoded with urlsafe base64.
+        # The aud and iss claims we care about are in the payload part, which
+        # is a JSON object.
+        try:
+            # By destructuring the list after splitting, we ensure that we have
+            # exactly 3 segments
+            _, payload, _ = logout_token.split(".")
+        except ValueError:
+            raise SynapseError(400, "Invalid logout_token in request")
+
+        try:
+            payload_bytes = unpaddedbase64.decode_base64(payload)
+            claims = json_decoder.decode(payload_bytes.decode("utf-8"))
+        except (json.JSONDecodeError, binascii.Error, UnicodeError):
+            raise SynapseError(400, "Invalid logout_token payload in request")
+
+        try:
+            # Let's extract the iss and aud claims
+            iss = claims["iss"]
+            aud = claims["aud"]
+            # The aud claim can be either a string or a list of string. Here we
+            # normalize it as a list of strings.
+            if isinstance(aud, str):
+                aud = [aud]
+
+            # Check that we have the right types for the aud and the iss claims
+            if not isinstance(iss, str) or not isinstance(aud, list):
+                raise TypeError()
+            for a in aud:
+                if not isinstance(a, str):
+                    raise TypeError()
+
+            # At this point we properly checked both claims types
+            issuer: str = iss
+            audience: List[str] = aud
+        except (TypeError, KeyError):
+            raise SynapseError(400, "Invalid issuer/audience in logout_token")
+
+        # Now that we know the audience and the issuer, we can figure out from
+        # what provider it is coming from
+        oidc_provider: Optional[OidcProvider] = None
+        for provider in self._providers.values():
+            if provider.issuer == issuer and provider.client_id in audience:
+                oidc_provider = provider
+                break
+
+        if oidc_provider is None:
+            raise SynapseError(400, "Could not find the OP that issued this event")
+
+        # Ask the provider to handle the logout request.
+        await oidc_provider.handle_backchannel_logout(request, logout_token)
+
 
 class OidcError(Exception):
     """Used to catch errors when calling the token_endpoint"""
@@ -275,6 +368,7 @@ class OidcProvider:
         provider: OidcProviderConfig,
     ):
         self._store = hs.get_datastores().main
+        self._clock = hs.get_clock()
 
         self._macaroon_generaton = macaroon_generator
 
@@ -341,6 +435,7 @@ class OidcProvider:
         self.idp_brand = provider.idp_brand
 
         self._sso_handler = hs.get_sso_handler()
+        self._device_handler = hs.get_device_handler()
 
         self._sso_handler.register_identity_provider(self)
 
@@ -399,6 +494,41 @@ class OidcProvider:
             # If we're not using userinfo, we need a valid jwks to validate the ID token
             m.validate_jwks_uri()
 
+        if self._config.backchannel_logout_enabled:
+            if not m.get("backchannel_logout_supported", False):
+                logger.warning(
+                    "OIDC Back-Channel Logout is enabled for issuer %r"
+                    "but it does not advertise support for it",
+                    self.issuer,
+                )
+
+            elif not m.get("backchannel_logout_session_supported", False):
+                logger.warning(
+                    "OIDC Back-Channel Logout is enabled and supported "
+                    "by issuer %r but it might not send a session ID with "
+                    "logout tokens, which is required for the logouts to work",
+                    self.issuer,
+                )
+
+            if not self._config.backchannel_logout_ignore_sub:
+                # If OIDC backchannel logouts are enabled, the provider mapping provider
+                # should use the `sub` claim. We verify that by mapping a dumb user and
+                # see if we get back the sub claim
+                user = UserInfo({"sub": "thisisasubject"})
+                try:
+                    subject = self._user_mapping_provider.get_remote_user_id(user)
+                    if subject != user["sub"]:
+                        raise ValueError("Unexpected subject")
+                except Exception:
+                    logger.warning(
+                        f"OIDC Back-Channel Logout is enabled for issuer {self.issuer!r} "
+                        "but it looks like the configured `user_mapping_provider` "
+                        "does not use the `sub` claim as subject. If it is the case, "
+                        "and you want Synapse to ignore the `sub` claim in OIDC "
+                        "Back-Channel Logouts, set `backchannel_logout_ignore_sub` "
+                        "to `true` in the issuer config."
+                    )
+
     @property
     def _uses_userinfo(self) -> bool:
         """Returns True if the ``userinfo_endpoint`` should be used.
@@ -414,6 +544,16 @@ class OidcProvider:
             or self._user_profile_method == "userinfo_endpoint"
         )
 
+    @property
+    def issuer(self) -> str:
+        """The issuer identifying this provider."""
+        return self._config.issuer
+
+    @property
+    def client_id(self) -> str:
+        """The client_id used when interacting with this provider."""
+        return self._config.client_id
+
     async def load_metadata(self, force: bool = False) -> OpenIDProviderMetadata:
         """Return the provider metadata.
 
@@ -661,61 +801,99 @@ class OidcProvider:
 
         return UserInfo(resp)
 
-    async def _parse_id_token(self, token: Token, nonce: str) -> CodeIDToken:
-        """Return an instance of UserInfo from token's ``id_token``.
+    async def _verify_jwt(
+        self,
+        alg_values: List[str],
+        token: str,
+        claims_cls: Type[C],
+        claims_options: Optional[dict] = None,
+        claims_params: Optional[dict] = None,
+    ) -> C:
+        """Decode and validate a JWT, re-fetching the JWKS as needed.
 
         Args:
-            token: the token given by the ``token_endpoint``.
-                Must include an ``id_token`` field.
-            nonce: the nonce value originally sent in the initial authorization
-                request. This value should match the one inside the token.
+            alg_values: list of `alg` values allowed when verifying the JWT.
+            token: the JWT.
+            claims_cls: the JWTClaims class to use to validate the claims.
+            claims_options: dict of options passed to the `claims_cls` constructor.
+            claims_params: dict of params passed to the `claims_cls` constructor.
 
         Returns:
-            The decoded claims in the ID token.
+            The decoded claims in the JWT.
         """
-        metadata = await self.load_metadata()
-        claims_params = {
-            "nonce": nonce,
-            "client_id": self._client_auth.client_id,
-        }
-        if "access_token" in token:
-            # If we got an `access_token`, there should be an `at_hash` claim
-            # in the `id_token` that we can check against.
-            claims_params["access_token"] = token["access_token"]
-
-        alg_values = metadata.get("id_token_signing_alg_values_supported", ["RS256"])
         jwt = JsonWebToken(alg_values)
 
-        claim_options = {"iss": {"values": [metadata["issuer"]]}}
-
-        id_token = token["id_token"]
-        logger.debug("Attempting to decode JWT id_token %r", id_token)
+        logger.debug("Attempting to decode JWT (%s) %r", claims_cls.__name__, token)
 
         # Try to decode the keys in cache first, then retry by forcing the keys
         # to be reloaded
         jwk_set = await self.load_jwks()
         try:
             claims = jwt.decode(
-                id_token,
+                token,
                 key=jwk_set,
-                claims_cls=CodeIDToken,
-                claims_options=claim_options,
+                claims_cls=claims_cls,
+                claims_options=claims_options,
                 claims_params=claims_params,
             )
         except ValueError:
             logger.info("Reloading JWKS after decode error")
             jwk_set = await self.load_jwks(force=True)  # try reloading the jwks
             claims = jwt.decode(
-                id_token,
+                token,
                 key=jwk_set,
-                claims_cls=CodeIDToken,
-                claims_options=claim_options,
+                claims_cls=claims_cls,
+                claims_options=claims_options,
                 claims_params=claims_params,
             )
 
-        logger.debug("Decoded id_token JWT %r; validating", claims)
+        logger.debug("Decoded JWT (%s) %r; validating", claims_cls.__name__, claims)
+
+        claims.validate(
+            now=self._clock.time(), leeway=120
+        )  # allows 2 min of clock skew
+        return claims
+
+    async def _parse_id_token(self, token: Token, nonce: str) -> CodeIDToken:
+        """Return an instance of UserInfo from token's ``id_token``.
+
+        Args:
+            token: the token given by the ``token_endpoint``.
+                Must include an ``id_token`` field.
+            nonce: the nonce value originally sent in the initial authorization
+                request. This value should match the one inside the token.
+
+        Returns:
+            The decoded claims in the ID token.
+        """
+        id_token = token.get("id_token")
+
+        # That has been theoritically been checked by the caller, so even though
+        # assertion are not enabled in production, it is mainly here to appease mypy
+        assert id_token is not None
+
+        metadata = await self.load_metadata()
+
+        claims_params = {
+            "nonce": nonce,
+            "client_id": self._client_auth.client_id,
+        }
+        if "access_token" in token:
+            # If we got an `access_token`, there should be an `at_hash` claim
+            # in the `id_token` that we can check against.
+            claims_params["access_token"] = token["access_token"]
+
+        claims_options = {"iss": {"values": [metadata["issuer"]]}}
+
+        alg_values = metadata.get("id_token_signing_alg_values_supported", ["RS256"])
 
-        claims.validate(leeway=120)  # allows 2 min of clock skew
+        claims = await self._verify_jwt(
+            alg_values=alg_values,
+            token=id_token,
+            claims_cls=CodeIDToken,
+            claims_options=claims_options,
+            claims_params=claims_params,
+        )
 
         return claims
 
@@ -1036,6 +1214,146 @@ class OidcProvider:
         # to be strings.
         return str(remote_user_id)
 
+    async def handle_backchannel_logout(
+        self, request: SynapseRequest, logout_token: str
+    ) -> None:
+        """Handle an incoming request to /_synapse/client/oidc/backchannel_logout
+
+        The OIDC Provider posts a logout token to this endpoint when a user
+        session ends. That token is a JWT signed with the same keys as
+        ID tokens. The OpenID Connect Back-Channel Logout draft explains how to
+        validate the JWT and figure out what session to end.
+
+        Args:
+            request: The request to respond to
+            logout_token: The logout token (a JWT) extracted from the request body
+        """
+        # Back-Channel Logout can be disabled in the config, hence this check.
+        # This is not that important for now since Synapse is registered
+        # manually to the OP, so not specifying the backchannel-logout URI is
+        # as effective than disabling it here. It might make more sense if we
+        # support dynamic registration in Synapse at some point.
+        if not self._config.backchannel_logout_enabled:
+            logger.warning(
+                f"Received an OIDC Back-Channel Logout request from issuer {self.issuer!r} but it is disabled in config"
+            )
+
+            # TODO: this responds with a 400 status code, which is what the OIDC
+            # Back-Channel Logout spec expects, but spec also suggests answering with
+            # a JSON object, with the `error` and `error_description` fields set, which
+            # we are not doing here.
+            # See https://openid.net/specs/openid-connect-backchannel-1_0.html#BCResponse
+            raise SynapseError(
+                400, "OpenID Connect Back-Channel Logout is disabled for this provider"
+            )
+
+        metadata = await self.load_metadata()
+
+        # As per OIDC Back-Channel Logout 1.0 sec. 2.4:
+        #   A Logout Token MUST be signed and MAY also be encrypted. The same
+        #   keys are used to sign and encrypt Logout Tokens as are used for ID
+        #   Tokens. If the Logout Token is encrypted, it SHOULD replicate the
+        #   iss (issuer) claim in the JWT Header Parameters, as specified in
+        #   Section 5.3 of [JWT].
+        alg_values = metadata.get("id_token_signing_alg_values_supported", ["RS256"])
+
+        # As per sec. 2.6:
+        #    3. Validate the iss, aud, and iat Claims in the same way they are
+        #       validated in ID Tokens.
+        # Which means the audience should contain Synapse's client_id and the
+        # issuer should be the IdP issuer
+        claims_options = {
+            "iss": {"values": [metadata["issuer"]]},
+            "aud": {"values": [self.client_id]},
+        }
+
+        try:
+            claims = await self._verify_jwt(
+                alg_values=alg_values,
+                token=logout_token,
+                claims_cls=LogoutToken,
+                claims_options=claims_options,
+            )
+        except JoseError:
+            logger.exception("Invalid logout_token")
+            raise SynapseError(400, "Invalid logout_token")
+
+        # As per sec. 2.6:
+        #    4. Verify that the Logout Token contains a sub Claim, a sid Claim,
+        #       or both.
+        #    5. Verify that the Logout Token contains an events Claim whose
+        #       value is JSON object containing the member name
+        #       http://schemas.openid.net/event/backchannel-logout.
+        #    6. Verify that the Logout Token does not contain a nonce Claim.
+        # This is all verified by the LogoutToken claims class, so at this
+        # point the `sid` claim exists and is a string.
+        sid: str = claims.get("sid")
+
+        # If the `sub` claim was included in the logout token, we check that it matches
+        # that it matches the right user. We can have cases where the `sub` claim is not
+        # the ID saved in database, so we let admins disable this check in config.
+        sub: Optional[str] = claims.get("sub")
+        expected_user_id: Optional[str] = None
+        if sub is not None and not self._config.backchannel_logout_ignore_sub:
+            expected_user_id = await self._store.get_user_by_external_id(
+                self.idp_id, sub
+            )
+
+        # Invalidate any running user-mapping sessions, in-flight login tokens and
+        # active devices
+        await self._sso_handler.revoke_sessions_for_provider_session_id(
+            auth_provider_id=self.idp_id,
+            auth_provider_session_id=sid,
+            expected_user_id=expected_user_id,
+        )
+
+        request.setResponseCode(200)
+        request.setHeader(b"Cache-Control", b"no-cache, no-store")
+        request.setHeader(b"Pragma", b"no-cache")
+        finish_request(request)
+
+
+class LogoutToken(JWTClaims):
+    """
+    Holds and verify claims of a logout token, as per
+    https://openid.net/specs/openid-connect-backchannel-1_0.html#LogoutToken
+    """
+
+    REGISTERED_CLAIMS = ["iss", "sub", "aud", "iat", "jti", "events", "sid"]
+
+    def validate(self, now: Optional[int] = None, leeway: int = 0) -> None:
+        """Validate everything in claims payload."""
+        super().validate(now, leeway)
+        self.validate_sid()
+        self.validate_events()
+        self.validate_nonce()
+
+    def validate_sid(self) -> None:
+        """Ensure the sid claim is present"""
+        sid = self.get("sid")
+        if not sid:
+            raise MissingClaimError("sid")
+
+        if not isinstance(sid, str):
+            raise InvalidClaimError("sid")
+
+    def validate_nonce(self) -> None:
+        """Ensure the nonce claim is absent"""
+        if "nonce" in self:
+            raise InvalidClaimError("nonce")
+
+    def validate_events(self) -> None:
+        """Ensure the events claim is present and with the right value"""
+        events = self.get("events")
+        if not events:
+            raise MissingClaimError("events")
+
+        if not isinstance(events, dict):
+            raise InvalidClaimError("events")
+
+        if "http://schemas.openid.net/event/backchannel-logout" not in events:
+            raise InvalidClaimError("events")
+
 
 # number of seconds a newly-generated client secret should be valid for
 CLIENT_SECRET_VALIDITY_SECONDS = 3600
@@ -1105,6 +1423,7 @@ class JwtClientSecret:
         logger.info(
             "Generating new JWT for %s: %s %s", self._oauth_issuer, header, payload
         )
+        jwt = JsonWebToken(header["alg"])
         self._cached_secret = jwt.encode(header, payload, self._key.key)
         self._cached_secret_replacement_time = (
             expires_at - CLIENT_SECRET_MIN_VALIDITY_SECONDS
@@ -1119,9 +1438,6 @@ class UserAttributeDict(TypedDict):
     emails: List[str]
 
 
-C = TypeVar("C")
-
-
 class OidcMappingProvider(Generic[C]):
     """A mapping provider maps a UserInfo object to user attributes.
 
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index d8ff5289b5..4bf9a047a3 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -307,7 +307,11 @@ class ProfileHandler:
         if not self.max_avatar_size and not self.allowed_avatar_mimetypes:
             return True
 
-        server_name, _, media_id = parse_and_validate_mxc_uri(mxc)
+        host, port, media_id = parse_and_validate_mxc_uri(mxc)
+        if port is not None:
+            server_name = host + ":" + str(port)
+        else:
+            server_name = host
 
         if server_name == self.server_name:
             media_info = await self.store.get_local_media(media_id)
diff --git a/synapse/handlers/relations.py b/synapse/handlers/relations.py
index 0a0c6d938e..8e71dda970 100644
--- a/synapse/handlers/relations.py
+++ b/synapse/handlers/relations.py
@@ -17,7 +17,7 @@ from typing import TYPE_CHECKING, Dict, FrozenSet, Iterable, List, Optional, Tup
 
 import attr
 
-from synapse.api.constants import RelationTypes
+from synapse.api.constants import EventTypes, RelationTypes
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase, relation_from_event
 from synapse.logging.opentracing import trace
@@ -75,6 +75,7 @@ class RelationsHandler:
         self._clock = hs.get_clock()
         self._event_handler = hs.get_event_handler()
         self._event_serializer = hs.get_event_client_serializer()
+        self._event_creation_handler = hs.get_event_creation_handler()
 
     async def get_relations(
         self,
@@ -205,6 +206,59 @@ class RelationsHandler:
 
         return related_events, next_token
 
+    async def redact_events_related_to(
+        self,
+        requester: Requester,
+        event_id: str,
+        initial_redaction_event: EventBase,
+        relation_types: List[str],
+    ) -> None:
+        """Redacts all events related to the given event ID with one of the given
+        relation types.
+
+        This method is expected to be called when redacting the event referred to by
+        the given event ID.
+
+        If an event cannot be redacted (e.g. because of insufficient permissions), log
+        the error and try to redact the next one.
+
+        Args:
+            requester: The requester to redact events on behalf of.
+            event_id: The event IDs to look and redact relations of.
+            initial_redaction_event: The redaction for the event referred to by
+                event_id.
+            relation_types: The types of relations to look for.
+
+        Raises:
+            ShadowBanError if the requester is shadow-banned
+        """
+        related_event_ids = (
+            await self._main_store.get_all_relations_for_event_with_types(
+                event_id, relation_types
+            )
+        )
+
+        for related_event_id in related_event_ids:
+            try:
+                await self._event_creation_handler.create_and_send_nonmember_event(
+                    requester,
+                    {
+                        "type": EventTypes.Redaction,
+                        "content": initial_redaction_event.content,
+                        "room_id": initial_redaction_event.room_id,
+                        "sender": requester.user.to_string(),
+                        "redacts": related_event_id,
+                    },
+                    ratelimit=False,
+                )
+            except SynapseError as e:
+                logger.warning(
+                    "Failed to redact event %s (related to event %s): %s",
+                    related_event_id,
+                    event_id,
+                    e.msg,
+                )
+
     async def get_annotations_for_event(
         self,
         event_id: str,
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 04dc56e166..90b9dcf8a3 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -49,7 +49,6 @@ from synapse.api.constants import (
 from synapse.api.errors import (
     AuthError,
     Codes,
-    HttpResponseException,
     LimitExceededError,
     NotFoundError,
     StoreError,
@@ -60,7 +59,6 @@ from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion
 from synapse.event_auth import validate_event_for_room_version
 from synapse.events import EventBase
 from synapse.events.utils import copy_and_fixup_power_levels_contents
-from synapse.federation.federation_client import InvalidResponseError
 from synapse.handlers.relations import BundledAggregations
 from synapse.module_api import NOT_SPAM
 from synapse.rest.admin._base import assert_user_is_admin
@@ -559,7 +557,6 @@ class RoomCreationHandler:
             invite_list=[],
             initial_state=initial_state,
             creation_content=creation_content,
-            ratelimit=False,
         )
 
         # Transfer membership events
@@ -753,6 +750,10 @@ class RoomCreationHandler:
                 )
 
         if ratelimit:
+            # Rate limit once in advance, but don't rate limit the individual
+            # events in the room — room creation isn't atomic and it's very
+            # janky if half the events in the initial state don't make it because
+            # of rate limiting.
             await self.request_ratelimiter.ratelimit(requester)
 
         room_version_id = config.get(
@@ -913,7 +914,6 @@ class RoomCreationHandler:
             room_alias=room_alias,
             power_level_content_override=power_level_content_override,
             creator_join_profile=creator_join_profile,
-            ratelimit=ratelimit,
         )
 
         if "name" in config:
@@ -1037,7 +1037,6 @@ class RoomCreationHandler:
         room_alias: Optional[RoomAlias] = None,
         power_level_content_override: Optional[JsonDict] = None,
         creator_join_profile: Optional[JsonDict] = None,
-        ratelimit: bool = True,
     ) -> Tuple[int, str, int]:
         """Sends the initial events into a new room. Sends the room creation, membership,
         and power level events into the room sequentially, then creates and batches up the
@@ -1046,6 +1045,8 @@ class RoomCreationHandler:
         `power_level_content_override` doesn't apply when initial state has
         power level state event content.
 
+        Rate limiting should already have been applied by this point.
+
         Returns:
             A tuple containing the stream ID, event ID and depth of the last
             event sent to the room.
@@ -1055,9 +1056,6 @@ class RoomCreationHandler:
         event_keys = {"room_id": room_id, "sender": creator_id, "state_key": ""}
         depth = 1
 
-        # the last event sent/persisted to the db
-        last_sent_event_id: Optional[str] = None
-
         # the most recently created event
         prev_event: List[str] = []
         # a map of event types, state keys -> event_ids. We collect these mappings this as events are
@@ -1098,26 +1096,6 @@ class RoomCreationHandler:
 
             return new_event, new_context
 
-        async def send(
-            event: EventBase,
-            context: synapse.events.snapshot.EventContext,
-            creator: Requester,
-        ) -> int:
-            nonlocal last_sent_event_id
-
-            ev = await self.event_creation_handler.handle_new_client_event(
-                requester=creator,
-                events_and_context=[(event, context)],
-                ratelimit=False,
-                ignore_shadow_ban=True,
-            )
-
-            last_sent_event_id = ev.event_id
-
-            # we know it was persisted, so must have a stream ordering
-            assert ev.internal_metadata.stream_ordering
-            return ev.internal_metadata.stream_ordering
-
         try:
             config = self._presets_dict[preset_config]
         except KeyError:
@@ -1131,16 +1109,20 @@ class RoomCreationHandler:
         )
 
         logger.debug("Sending %s in new room", EventTypes.Member)
-        await send(creation_event, creation_context, creator)
+        ev = await self.event_creation_handler.handle_new_client_event(
+            requester=creator,
+            events_and_context=[(creation_event, creation_context)],
+            ratelimit=False,
+            ignore_shadow_ban=True,
+        )
+        last_sent_event_id = ev.event_id
 
-        # Room create event must exist at this point
-        assert last_sent_event_id is not None
         member_event_id, _ = await self.room_member_handler.update_membership(
             creator,
             creator.user,
             room_id,
             "join",
-            ratelimit=ratelimit,
+            ratelimit=False,
             content=creator_join_profile,
             new_room=True,
             prev_event_ids=[last_sent_event_id],
@@ -1152,7 +1134,9 @@ class RoomCreationHandler:
         # through a different code path
         depth += 1
         state_map[(EventTypes.Member, creator.user.to_string())] = member_event_id
+        current_state_group = await self._storage_controllers.state.get_state_group_for_events([member_event_id]).value
 
+        events_to_send = []
         # We treat the power levels override specially as this needs to be one
         # of the first events that get sent into a room.
         pl_content = initial_state.pop((EventTypes.PowerLevels, ""), None)
@@ -1160,8 +1144,7 @@ class RoomCreationHandler:
             power_event, power_context = await create_event(
                 EventTypes.PowerLevels, pl_content, False
             )
-            await send(power_event, power_context, creator)
-            current_state_group = power_context._state_group
+            events_to_send.append((power_event, power_context))
         else:
             power_level_content: JsonDict = {
                 "users": {creator_id: 100},
@@ -1209,10 +1192,8 @@ class RoomCreationHandler:
                 power_level_content,
                 False,
             )
-            await send(pl_event, pl_context, creator)
-            current_state_group = pl_context._state_group
+            events_to_send.append((pl_event, pl_context))
 
-        events_to_send = []
         if room_alias and (EventTypes.CanonicalAlias, "") not in initial_state:
             room_alias_event, room_alias_context = await create_event(
                 EventTypes.CanonicalAlias, {"alias": room_alias.to_string()}, True
@@ -1271,7 +1252,10 @@ class RoomCreationHandler:
             index += 1
 
         last_event = await self.event_creation_handler.handle_new_client_event(
-            creator, events_to_send, ignore_shadow_ban=True
+            creator,
+            events_to_send,
+            ignore_shadow_ban=True,
+            ratelimit=False,
         )
         assert last_event.internal_metadata.stream_ordering is not None
         return last_event.internal_metadata.stream_ordering, last_event.event_id, depth
@@ -1493,7 +1477,12 @@ class TimestampLookupHandler:
         Raises:
             SynapseError if unable to find any event locally in the given direction
         """
-
+        logger.debug(
+            "get_event_for_timestamp(room_id=%s, timestamp=%s, direction=%s) Finding closest event...",
+            room_id,
+            timestamp,
+            direction,
+        )
         local_event_id = await self.store.get_event_id_for_timestamp(
             room_id, timestamp, direction
         )
@@ -1545,85 +1534,54 @@ class TimestampLookupHandler:
                 )
             )
 
-            # Loop through each homeserver candidate until we get a succesful response
-            for domain in likely_domains:
-                # We don't want to ask our own server for information we don't have
-                if domain == self.server_name:
-                    continue
+            remote_response = await self.federation_client.timestamp_to_event(
+                destinations=likely_domains,
+                room_id=room_id,
+                timestamp=timestamp,
+                direction=direction,
+            )
+            if remote_response is not None:
+                logger.debug(
+                    "get_event_for_timestamp: remote_response=%s",
+                    remote_response,
+                )
 
-                try:
-                    remote_response = await self.federation_client.timestamp_to_event(
-                        domain, room_id, timestamp, direction
-                    )
-                    logger.debug(
-                        "get_event_for_timestamp: response from domain(%s)=%s",
-                        domain,
-                        remote_response,
-                    )
+                remote_event_id = remote_response.event_id
+                remote_origin_server_ts = remote_response.origin_server_ts
 
-                    remote_event_id = remote_response.event_id
-                    remote_origin_server_ts = remote_response.origin_server_ts
-
-                    # Backfill this event so we can get a pagination token for
-                    # it with `/context` and paginate `/messages` from this
-                    # point.
-                    #
-                    # TODO: The requested timestamp may lie in a part of the
-                    #   event graph that the remote server *also* didn't have,
-                    #   in which case they will have returned another event
-                    #   which may be nowhere near the requested timestamp. In
-                    #   the future, we may need to reconcile that gap and ask
-                    #   other homeservers, and/or extend `/timestamp_to_event`
-                    #   to return events on *both* sides of the timestamp to
-                    #   help reconcile the gap faster.
-                    remote_event = (
-                        await self.federation_event_handler.backfill_event_id(
-                            domain, room_id, remote_event_id
-                        )
-                    )
+                # Backfill this event so we can get a pagination token for
+                # it with `/context` and paginate `/messages` from this
+                # point.
+                pulled_pdu_info = await self.federation_event_handler.backfill_event_id(
+                    likely_domains, room_id, remote_event_id
+                )
+                remote_event = pulled_pdu_info.pdu
 
-                    # XXX: When we see that the remote server is not trustworthy,
-                    # maybe we should not ask them first in the future.
-                    if remote_origin_server_ts != remote_event.origin_server_ts:
-                        logger.info(
-                            "get_event_for_timestamp: Remote server (%s) claimed that remote_event_id=%s occured at remote_origin_server_ts=%s but that isn't true (actually occured at %s). Their claims are dubious and we should consider not trusting them.",
-                            domain,
-                            remote_event_id,
-                            remote_origin_server_ts,
-                            remote_event.origin_server_ts,
-                        )
-
-                    # Only return the remote event if it's closer than the local event
-                    if not local_event or (
-                        abs(remote_event.origin_server_ts - timestamp)
-                        < abs(local_event.origin_server_ts - timestamp)
-                    ):
-                        logger.info(
-                            "get_event_for_timestamp: returning remote_event_id=%s (%s) since it's closer to timestamp=%s than local_event=%s (%s)",
-                            remote_event_id,
-                            remote_event.origin_server_ts,
-                            timestamp,
-                            local_event.event_id if local_event else None,
-                            local_event.origin_server_ts if local_event else None,
-                        )
-                        return remote_event_id, remote_origin_server_ts
-                except (HttpResponseException, InvalidResponseError) as ex:
-                    # Let's not put a high priority on some other homeserver
-                    # failing to respond or giving a random response
-                    logger.debug(
-                        "get_event_for_timestamp: Failed to fetch /timestamp_to_event from %s because of exception(%s) %s args=%s",
-                        domain,
-                        type(ex).__name__,
-                        ex,
-                        ex.args,
+                # XXX: When we see that the remote server is not trustworthy,
+                # maybe we should not ask them first in the future.
+                if remote_origin_server_ts != remote_event.origin_server_ts:
+                    logger.info(
+                        "get_event_for_timestamp: Remote server (%s) claimed that remote_event_id=%s occured at remote_origin_server_ts=%s but that isn't true (actually occured at %s). Their claims are dubious and we should consider not trusting them.",
+                        pulled_pdu_info.pull_origin,
+                        remote_event_id,
+                        remote_origin_server_ts,
+                        remote_event.origin_server_ts,
                     )
-                except Exception:
-                    # But we do want to see some exceptions in our code
-                    logger.warning(
-                        "get_event_for_timestamp: Failed to fetch /timestamp_to_event from %s because of exception",
-                        domain,
-                        exc_info=True,
+
+                # Only return the remote event if it's closer than the local event
+                if not local_event or (
+                    abs(remote_event.origin_server_ts - timestamp)
+                    < abs(local_event.origin_server_ts - timestamp)
+                ):
+                    logger.info(
+                        "get_event_for_timestamp: returning remote_event_id=%s (%s) since it's closer to timestamp=%s than local_event=%s (%s)",
+                        remote_event_id,
+                        remote_event.origin_server_ts,
+                        timestamp,
+                        local_event.event_id if local_event else None,
+                        local_event.origin_server_ts if local_event else None,
                     )
+                    return remote_event_id, remote_origin_server_ts
 
         # To appease mypy, we have to add both of these conditions to check for
         # `None`. We only expect `local_event` to be `None` when
diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py
index 5943f08e91..749d7e93b0 100644
--- a/synapse/handlers/sso.py
+++ b/synapse/handlers/sso.py
@@ -191,6 +191,7 @@ class SsoHandler:
         self._server_name = hs.hostname
         self._registration_handler = hs.get_registration_handler()
         self._auth_handler = hs.get_auth_handler()
+        self._device_handler = hs.get_device_handler()
         self._error_template = hs.config.sso.sso_error_template
         self._bad_user_template = hs.config.sso.sso_auth_bad_user_template
         self._profile_handler = hs.get_profile_handler()
@@ -1026,6 +1027,76 @@ class SsoHandler:
 
         return True
 
+    async def revoke_sessions_for_provider_session_id(
+        self,
+        auth_provider_id: str,
+        auth_provider_session_id: str,
+        expected_user_id: Optional[str] = None,
+    ) -> None:
+        """Revoke any devices and in-flight logins tied to a provider session.
+
+        Args:
+            auth_provider_id: A unique identifier for this SSO provider, e.g.
+                "oidc" or "saml".
+            auth_provider_session_id: The session ID from the provider to logout
+            expected_user_id: The user we're expecting to logout. If set, it will ignore
+                sessions belonging to other users and log an error.
+        """
+        # Invalidate any running user-mapping sessions
+        to_delete = []
+        for session_id, session in self._username_mapping_sessions.items():
+            if (
+                session.auth_provider_id == auth_provider_id
+                and session.auth_provider_session_id == auth_provider_session_id
+            ):
+                to_delete.append(session_id)
+
+        for session_id in to_delete:
+            logger.info("Revoking mapping session %s", session_id)
+            del self._username_mapping_sessions[session_id]
+
+        # Invalidate any in-flight login tokens
+        await self._store.invalidate_login_tokens_by_session_id(
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
+        )
+
+        # Fetch any device(s) in the store associated with the session ID.
+        devices = await self._store.get_devices_by_auth_provider_session_id(
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
+        )
+
+        # We have no guarantee that all the devices of that session are for the same
+        # `user_id`. Hence, we have to iterate over the list of devices and log them out
+        # one by one.
+        for device in devices:
+            user_id = device["user_id"]
+            device_id = device["device_id"]
+
+            # If the user_id associated with that device/session is not the one we got
+            # out of the `sub` claim, skip that device and show log an error.
+            if expected_user_id is not None and user_id != expected_user_id:
+                logger.error(
+                    "Received a logout notification from SSO provider "
+                    f"{auth_provider_id!r} for the user {expected_user_id!r}, but with "
+                    f"a session ID ({auth_provider_session_id!r}) which belongs to "
+                    f"{user_id!r}. This may happen when the SSO provider user mapper "
+                    "uses something else than the standard attribute as mapping ID. "
+                    "For OIDC providers, set `backchannel_logout_ignore_sub` to `true` "
+                    "in the provider config if that is the case."
+                )
+                continue
+
+            logger.info(
+                "Logging out %r (device %r) via SSO (%r) logout notification (session %r).",
+                user_id,
+                device_id,
+                auth_provider_id,
+                auth_provider_session_id,
+            )
+            await self._device_handler.delete_devices(user_id, [device_id])
+
 
 def get_username_mapping_session_cookie_from_request(request: IRequest) -> str:
     """Extract the session ID from the cookie
diff --git a/synapse/http/client.py b/synapse/http/client.py
index 084d0a5b84..4eb740c040 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -25,7 +25,6 @@ from typing import (
     List,
     Mapping,
     Optional,
-    Sequence,
     Tuple,
     Union,
 )
@@ -90,14 +89,29 @@ incoming_responses_counter = Counter(
     "synapse_http_client_responses", "", ["method", "code"]
 )
 
-# the type of the headers list, to be passed to the t.w.h.Headers.
-# Actually we can mix str and bytes keys, but Mapping treats 'key' as invariant so
-# we simplify.
+# the type of the headers map, to be passed to the t.w.h.Headers.
+#
+# The actual type accepted by Twisted is
+#   Mapping[Union[str, bytes], Sequence[Union[str, bytes]] ,
+# allowing us to mix and match str and bytes freely. However: any str is also a
+# Sequence[str]; passing a header string value which is a
+# standalone str is interpreted as a sequence of 1-codepoint strings. This is a disastrous footgun.
+# We use a narrower value type (RawHeaderValue) to avoid this footgun.
+#
+# We also simplify the keys to be either all str or all bytes. This helps because
+# Dict[K, V] is invariant in K (and indeed V).
 RawHeaders = Union[Mapping[str, "RawHeaderValue"], Mapping[bytes, "RawHeaderValue"]]
 
 # the value actually has to be a List, but List is invariant so we can't specify that
 # the entries can either be Lists or bytes.
-RawHeaderValue = Sequence[Union[str, bytes]]
+RawHeaderValue = Union[
+    List[str],
+    List[bytes],
+    List[Union[str, bytes]],
+    Tuple[str, ...],
+    Tuple[bytes, ...],
+    Tuple[Union[str, bytes], ...],
+]
 
 
 def check_against_blacklist(
diff --git a/synapse/metrics/background_process_metrics.py b/synapse/metrics/background_process_metrics.py
index 7a1516d3a8..9ea4e23b31 100644
--- a/synapse/metrics/background_process_metrics.py
+++ b/synapse/metrics/background_process_metrics.py
@@ -174,8 +174,10 @@ class _BackgroundProcess:
             diff = new_stats - self._reported_stats
         self._reported_stats = new_stats
 
-        _background_process_ru_utime.labels(self.desc).inc(diff.ru_utime)
-        _background_process_ru_stime.labels(self.desc).inc(diff.ru_stime)
+        # For unknown reasons, the difference in times can be negative. See comment in
+        # synapse.http.request_metrics.RequestMetrics.update_metrics.
+        _background_process_ru_utime.labels(self.desc).inc(max(diff.ru_utime, 0))
+        _background_process_ru_stime.labels(self.desc).inc(max(diff.ru_stime, 0))
         _background_process_db_txn_count.labels(self.desc).inc(diff.db_txn_count)
         _background_process_db_txn_duration.labels(self.desc).inc(
             diff.db_txn_duration_sec
diff --git a/synapse/module_api/__init__.py b/synapse/module_api/__init__.py
index 6a6ae208d1..30e689d00d 100644
--- a/synapse/module_api/__init__.py
+++ b/synapse/module_api/__init__.py
@@ -771,50 +771,11 @@ class ModuleApi:
             auth_provider_session_id: The session ID got during login from the SSO IdP,
                 if any.
         """
-        # The deprecated `generate_short_term_login_token` method defaulted to an empty
-        # string for the `auth_provider_id` because of how the underlying macaroon was
-        # generated. This will change to a proper NULL-able field when the tokens get
-        # moved to the database.
-        return self._hs.get_macaroon_generator().generate_short_term_login_token(
+        return await self._hs.get_auth_handler().create_login_token_for_user_id(
             user_id,
-            auth_provider_id or "",
-            auth_provider_session_id,
             duration_in_ms,
-        )
-
-    def generate_short_term_login_token(
-        self,
-        user_id: str,
-        duration_in_ms: int = (2 * 60 * 1000),
-        auth_provider_id: str = "",
-        auth_provider_session_id: Optional[str] = None,
-    ) -> str:
-        """Generate a login token suitable for m.login.token authentication
-
-        Added in Synapse v1.9.0.
-
-        This was deprecated in Synapse v1.69.0 in favor of create_login_token, and will
-        be removed in Synapse 1.71.0.
-
-        Args:
-            user_id: gives the ID of the user that the token is for
-
-            duration_in_ms: the time that the token will be valid for
-
-            auth_provider_id: the ID of the SSO IdP that the user used to authenticate
-               to get this token, if any. This is encoded in the token so that
-               /login can report stats on number of successful logins by IdP.
-        """
-        logger.warn(
-            "A module configured on this server uses ModuleApi.generate_short_term_login_token(), "
-            "which is deprecated in favor of ModuleApi.create_login_token(), and will be removed in "
-            "Synapse 1.71.0",
-        )
-        return self._hs.get_macaroon_generator().generate_short_term_login_token(
-            user_id,
             auth_provider_id,
             auth_provider_session_id,
-            duration_in_ms,
         )
 
     @defer.inlineCallbacks
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index a75386f6a0..75b7e126ca 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -45,7 +45,6 @@ if TYPE_CHECKING:
 
 logger = logging.getLogger(__name__)
 
-
 push_rules_invalidation_counter = Counter(
     "synapse_push_bulk_push_rule_evaluator_push_rules_invalidation_counter", ""
 )
@@ -107,6 +106,8 @@ class BulkPushRuleEvaluator:
         self.clock = hs.get_clock()
         self._event_auth_handler = hs.get_event_auth_handler()
 
+        self._related_event_match_enabled = self.hs.config.experimental.msc3664_enabled
+
         self.room_push_rule_cache_metrics = register_cache(
             "cache",
             "room_push_rule_cache",
@@ -165,8 +166,21 @@ class BulkPushRuleEvaluator:
         return rules_by_user
 
     async def _get_power_levels_and_sender_level(
-        self, event: EventBase, context: EventContext
+        self,
+        event: EventBase,
+        context: EventContext,
+        event_id_to_event: Mapping[str, EventBase],
     ) -> Tuple[dict, Optional[int]]:
+        """
+        Given an event and an event context, get the power level event relevant to the event
+        and the power level of the sender of the event.
+        Args:
+            event: event to check
+            context: context of event to check
+            event_id_to_event: a mapping of event_id to event for a set of events being
+            batch persisted. This is needed as the sought-after power level event may
+            be in this batch rather than the DB
+        """
         # There are no power levels and sender levels possible to get from outlier
         if event.internal_metadata.is_outlier():
             return {}, None
@@ -177,15 +191,26 @@ class BulkPushRuleEvaluator:
         )
         pl_event_id = prev_state_ids.get(POWER_KEY)
 
+        # fastpath: if there's a power level event, that's all we need, and
+        # not having a power level event is an extreme edge case
         if pl_event_id:
-            # fastpath: if there's a power level event, that's all we need, and
-            # not having a power level event is an extreme edge case
-            auth_events = {POWER_KEY: await self.store.get_event(pl_event_id)}
+            # Get the power level event from the batch, or fall back to the database.
+            pl_event = event_id_to_event.get(pl_event_id)
+            if pl_event:
+                auth_events = {POWER_KEY: pl_event}
+            else:
+                auth_events = {POWER_KEY: await self.store.get_event(pl_event_id)}
         else:
             auth_events_ids = self._event_auth_handler.compute_auth_events(
                 event, prev_state_ids, for_verification=False
             )
             auth_events_dict = await self.store.get_events(auth_events_ids)
+            # Some needed auth events might be in the batch, combine them with those
+            # fetched from the database.
+            for auth_event_id in auth_events_ids:
+                auth_event = event_id_to_event.get(auth_event_id)
+                if auth_event:
+                    auth_events_dict[auth_event_id] = auth_event
             auth_events = {(e.type, e.state_key): e for e in auth_events_dict.values()}
 
         sender_level = get_user_power_level(event.sender, auth_events)
@@ -194,16 +219,80 @@ class BulkPushRuleEvaluator:
 
         return pl_event.content if pl_event else {}, sender_level
 
-    @measure_func("action_for_event_by_user")
-    async def action_for_event_by_user(
-        self, event: EventBase, context: EventContext
+    async def _related_events(self, event: EventBase) -> Dict[str, Dict[str, str]]:
+        """Fetches the related events for 'event'. Sets the im.vector.is_falling_back key if the event is from a fallback relation
+
+        Returns:
+            Mapping of relation type to flattened events.
+        """
+        related_events: Dict[str, Dict[str, str]] = {}
+        if self._related_event_match_enabled:
+            related_event_id = event.content.get("m.relates_to", {}).get("event_id")
+            relation_type = event.content.get("m.relates_to", {}).get("rel_type")
+            if related_event_id is not None and relation_type is not None:
+                related_event = await self.store.get_event(
+                    related_event_id, allow_none=True
+                )
+                if related_event is not None:
+                    related_events[relation_type] = _flatten_dict(related_event)
+
+            reply_event_id = (
+                event.content.get("m.relates_to", {})
+                .get("m.in_reply_to", {})
+                .get("event_id")
+            )
+
+            # convert replies to pseudo relations
+            if reply_event_id is not None:
+                related_event = await self.store.get_event(
+                    reply_event_id, allow_none=True
+                )
+
+                if related_event is not None:
+                    related_events["m.in_reply_to"] = _flatten_dict(related_event)
+
+                    # indicate that this is from a fallback relation.
+                    if relation_type == "m.thread" and event.content.get(
+                        "m.relates_to", {}
+                    ).get("is_falling_back", False):
+                        related_events["m.in_reply_to"][
+                            "im.vector.is_falling_back"
+                        ] = ""
+
+        return related_events
+
+    async def action_for_events_by_user(
+        self, events_and_context: List[Tuple[EventBase, EventContext]]
     ) -> None:
-        """Given an event and context, evaluate the push rules, check if the message
-        should increment the unread count, and insert the results into the
-        event_push_actions_staging table.
+        """Given a list of events and their associated contexts, evaluate the push rules
+        for each event, check if the message should increment the unread count, and
+        insert the results into the event_push_actions_staging table.
         """
-        if not event.internal_metadata.is_notifiable():
-            # Push rules for events that aren't notifiable can't be processed by this
+        # For batched events the power level events may not have been persisted yet,
+        # so we pass in the batched events. Thus if the event cannot be found in the
+        # database we can check in the batch.
+        event_id_to_event = {e.event_id: e for e, _ in events_and_context}
+        for event, context in events_and_context:
+            await self._action_for_event_by_user(event, context, event_id_to_event)
+
+    @measure_func("action_for_event_by_user")
+    async def _action_for_event_by_user(
+        self,
+        event: EventBase,
+        context: EventContext,
+        event_id_to_event: Mapping[str, EventBase],
+    ) -> None:
+
+        if (
+            not event.internal_metadata.is_notifiable()
+            or event.internal_metadata.is_historical()
+        ):
+            # Push rules for events that aren't notifiable can't be processed by this and
+            # we want to skip push notification actions for historical messages
+            # because we don't want to notify people about old history back in time.
+            # The historical messages also do not have the proper `context.current_state_ids`
+            # and `state_groups` because they have `prev_events` that aren't persisted yet
+            # (historical messages persisted in reverse-chronological order).
             return
 
         # Disable counting as unread unless the experimental configuration is
@@ -223,7 +312,9 @@ class BulkPushRuleEvaluator:
         (
             power_levels,
             sender_power_level,
-        ) = await self._get_power_levels_and_sender_level(event, context)
+        ) = await self._get_power_levels_and_sender_level(
+            event, context, event_id_to_event
+        )
 
         # Find the event's thread ID.
         relation = relation_from_event(event)
@@ -238,6 +329,8 @@ class BulkPushRuleEvaluator:
                 # the parent is part of a thread.
                 thread_id = await self.store.get_thread_id(relation.parent_id)
 
+        related_events = await self._related_events(event)
+
         # It's possible that old room versions have non-integer power levels (floats or
         # strings). Workaround this by explicitly converting to int.
         notification_levels = power_levels.get("notifications", {})
@@ -250,6 +343,8 @@ class BulkPushRuleEvaluator:
             room_member_count,
             sender_power_level,
             notification_levels,
+            related_events,
+            self._related_event_match_enabled,
         )
 
         users = rules_by_user.keys()
diff --git a/synapse/res/templates/_base.html b/synapse/res/templates/_base.html
new file mode 100644
index 0000000000..46439fce6a
--- /dev/null
+++ b/synapse/res/templates/_base.html
@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8">
+    <meta http-equiv="X-UA-Compatible" content="IE=edge">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>{% block title %}{% endblock %}</title>
+    <style type="text/css">
+      {%- include 'style.css' without context %}
+    </style>
+    {% block header %}{%  endblock %}
+</head>
+<body>
+<header class="mx_Header">
+    {% if app_name == "Riot" %}
+        <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
+    {% elif app_name == "Vector" %}
+        <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
+    {% elif app_name == "Element" %}
+        <img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
+    {% else %}
+        <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
+    {% endif %}
+</header>
+
+{% block body %}{% endblock %}
+
+</body>
+</html>
diff --git a/synapse/res/templates/account_previously_renewed.html b/synapse/res/templates/account_previously_renewed.html
index bd4f7cea97..91582a8af0 100644
--- a/synapse/res/templates/account_previously_renewed.html
+++ b/synapse/res/templates/account_previously_renewed.html
@@ -1,12 +1,6 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Your account is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.</title>
-</head>
-<body>
-    Your account is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.
-</body>
-</html>
\ No newline at end of file
+{% extends "_base.html" %}
+{% block title %}Your account is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.{% endblock %}
+
+{% block body %}
+<p>Your account is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.</p>
+{% endblock %}
diff --git a/synapse/res/templates/account_renewed.html b/synapse/res/templates/account_renewed.html
index 57b319f375..18a57833f1 100644
--- a/synapse/res/templates/account_renewed.html
+++ b/synapse/res/templates/account_renewed.html
@@ -1,12 +1,6 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Your account has been successfully renewed and is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.</title>
-</head>
-<body>
-    Your account has been successfully renewed and is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.
-</body>
-</html>
\ No newline at end of file
+{% extends "_base.html" %}
+{% block title %}Your account has been successfully renewed and is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.{% endblock %}
+
+{% block body %}
+<p>Your account has been successfully renewed and is valid until {{ expiration_ts|format_ts("%d-%m-%Y") }}.</p>
+{% endblock %}
diff --git a/synapse/res/templates/add_threepid.html b/synapse/res/templates/add_threepid.html
index 71f2215b7a..33c883936a 100644
--- a/synapse/res/templates/add_threepid.html
+++ b/synapse/res/templates/add_threepid.html
@@ -1,14 +1,8 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Request to add an email address to your Matrix account</title>
-</head>
-<body>
-    <p>A request to add an email address to your Matrix account has been received. If this was you, please click the link below to confirm adding this email:</p>
-    <a href="{{ link }}">{{ link }}</a>
-    <p>If this was not you, you can safely ignore this email. Thank you.</p>
-</body>
-</html>
+{% extends "_base.html" %}
+{% block title %}Request to add an email address to your Matrix account{% endblock %}
+
+{% block body %}
+<p>A request to add an email address to your Matrix account has been received. If this was you, please click the link below to confirm adding this email:</p>
+<a href="{{ link }}">{{ link }}</a>
+<p>If this was not you, you can safely ignore this email. Thank you.</p>
+{% endblock %}
diff --git a/synapse/res/templates/add_threepid_failure.html b/synapse/res/templates/add_threepid_failure.html
index bd627ee9ce..f6d7e33825 100644
--- a/synapse/res/templates/add_threepid_failure.html
+++ b/synapse/res/templates/add_threepid_failure.html
@@ -1,13 +1,7 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Request failed</title>
-</head>
-<body>
-    <p>The request failed for the following reason: {{ failure_reason }}.</p>
-    <p>No changes have been made to your account.</p>
-</body>
-</html>
+{% extends "_base.html" %}
+{% block title %}Request failed{% endblock %}
+
+{% block body %}
+<p>The request failed for the following reason: {{ failure_reason }}.</p>
+<p>No changes have been made to your account.</p>
+{% endblock %}
diff --git a/synapse/res/templates/add_threepid_success.html b/synapse/res/templates/add_threepid_success.html
index 49170c138e..6d45111796 100644
--- a/synapse/res/templates/add_threepid_success.html
+++ b/synapse/res/templates/add_threepid_success.html
@@ -1,12 +1,6 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Your email has now been validated</title>
-</head>
-<body>
-    <p>Your email has now been validated, please return to your client. You may now close this window.</p>
-</body>
-</html>
\ No newline at end of file
+{% extends "_base.html" %}
+{% block title %}Your email has now been validated{% endblock %}
+
+{% block body %}
+<p>Your email has now been validated, please return to your client. You may now close this window.</p>
+{% endblock %}
diff --git a/synapse/res/templates/auth_success.html b/synapse/res/templates/auth_success.html
index 2d6ac44a0e..9178332f59 100644
--- a/synapse/res/templates/auth_success.html
+++ b/synapse/res/templates/auth_success.html
@@ -1,21 +1,21 @@
-<html>
-<head>
-<title>Success!</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+{% extends "_base.html" %}
+{% block title %}Success!{% endblock %}
+
+{% block header %}
 <link rel="stylesheet" href="/_matrix/static/client/register/style.css">
 <script>
 if (window.onAuthDone) {
     window.onAuthDone();
 } else if (window.opener && window.opener.postMessage) {
-     window.opener.postMessage("authDone", "*");
+    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>
-</body>
-</html>
+{% endblock %}
+
+{% block body %}
+<div>
+    <p>Thank you</p>
+    <p>You may now close this window and return to the application</p>
+</div>
+
+{% endblock %}
diff --git a/synapse/res/templates/invalid_token.html b/synapse/res/templates/invalid_token.html
index 2c7c384fe3..d0b1dae669 100644
--- a/synapse/res/templates/invalid_token.html
+++ b/synapse/res/templates/invalid_token.html
@@ -1,12 +1,5 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <title>Invalid renewal token.</title>
-</head>
-<body>
-    Invalid renewal token.
-</body>
-</html>
+{% block title %}Invalid renewal token.{% endblock %}
+
+{% block body %}
+<p>Invalid renewal token.</p>
+{% endblock %}
diff --git a/synapse/res/templates/notice_expiry.html b/synapse/res/templates/notice_expiry.html
index 865f9f7ada..406397aaca 100644
--- a/synapse/res/templates/notice_expiry.html
+++ b/synapse/res/templates/notice_expiry.html
@@ -1,47 +1,46 @@
-<!doctype html>
-<html lang="en">
-    <head>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <style type="text/css">
-            {% include 'mail.css' without context %}
-            {% include "mail-%s.css" % app_name ignore missing without context %}
-            {% include 'mail-expiry.css' without context %}
-        </style>
-    </head>
-    <body>
-        <table id="page">
-            <tr>
-                <td> </td>
-                <td id="inner">
-                    <table class="header">
-                        <tr>
-                            <td>
-                                <div class="salutation">Hi {{ display_name }},</div>
-                            </td>
-                            <td class="logo">
-                                {% if app_name == "Riot" %}
-                                    <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
-                                {% elif app_name == "Vector" %}
-                                    <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
-                                {% elif app_name == "Element" %}
-                                    <img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
-                                {% else %}
-                                    <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
-                                {% endif %}
-                            </td>
-                        </tr>
-                        <tr>
-                          <td colspan="2">
-                            <div class="noticetext">Your account will expire on {{ expiration_ts|format_ts("%d-%m-%Y") }}. This means that you will lose access to your account after this date.</div>
-                            <div class="noticetext">To extend the validity of your account, please click on the link below (or copy and paste it into a new browser tab):</div>
-                            <div class="noticetext"><a href="{{ url }}">{{ url }}</a></div>
-                          </td>
-                        </tr>
-                    </table>
-                </td>
-                <td> </td>
-            </tr>
-        </table>
-    </body>
-</html>
+{% extends "_base.html" %}
+{% block title %}Notice of expiry{% endblock %}
+
+{% block header %}
+<style type="text/css">
+    {% include 'mail.css' without context %}
+    {% include "mail-%s.css" % app_name ignore missing without context %}
+    {% include 'mail-expiry.css' without context %}
+</style>
+{% endblock %}
+
+{% block body %}
+<table id="page">
+    <tr>
+        <td> </td>
+        <td id="inner">
+            <table class="header">
+                <tr>
+                    <td>
+                        <div class="salutation">Hi {{ display_name }},</div>
+                    </td>
+                    <td class="logo">
+                        {% if app_name == "Riot" %}
+                            <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
+                        {% elif app_name == "Vector" %}
+                            <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
+                        {% elif app_name == "Element" %}
+                            <img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
+                        {% else %}
+                            <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
+                        {% endif %}
+                    </td>
+                </tr>
+                <tr>
+                    <td colspan="2">
+                    <div class="noticetext">Your account will expire on {{ expiration_ts|format_ts("%d-%m-%Y") }}. This means that you will lose access to your account after this date.</div>
+                    <div class="noticetext">To extend the validity of your account, please click on the link below (or copy and paste it into a new browser tab):</div>
+                    <div class="noticetext"><a href="{{ url }}">{{ url }}</a></div>
+                    </td>
+                </tr>
+            </table>
+        </td>
+        <td> </td>
+    </tr>
+</table>
+{% endblock %}
diff --git a/synapse/res/templates/notif_mail.html b/synapse/res/templates/notif_mail.html
index 9dba0c0253..939d40315f 100644
--- a/synapse/res/templates/notif_mail.html
+++ b/synapse/res/templates/notif_mail.html
@@ -1,59 +1,57 @@
-<!doctype html>
-<html lang="en">
-    <head>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <style type="text/css">
-            {%- include 'mail.css' without context %}
-            {%- include "mail-%s.css" % app_name ignore missing without context %}
-        </style>
-    </head>
-    <body>
-        <table id="page">
-            <tr>
-                <td> </td>
-                <td id="inner">
-                    <table class="header">
-                        <tr>
-                            <td>
-                                <div class="salutation">Hi {{ user_display_name }},</div>
-                                <div class="summarytext">{{ summary_text }}</div>
-                            </td>
-                            <td class="logo">
-                                {%- if app_name == "Riot" %}
-                                    <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
-                                {%- elif app_name == "Vector" %}
-                                    <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
-                                {%- elif app_name == "Element" %}
-                                    <img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
-                                {%- else %}
-                                    <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
-                                {%- endif %}
-                            </td>
-                        </tr>
-                    </table>
-                    {%- for room in rooms %}
-                        {%- include 'room.html' with context %}
-                    {%- endfor %}
-                    <div class="footer">
-                        <a href="{{ unsubscribe_link }}">Unsubscribe</a>
-                        <br/>
-                        <br/>
-                        <div class="debug">
-                            Sending email at {{ reason.now|format_ts("%c") }} due to activity in room {{ reason.room_name }} because
-                            an event was received at {{ reason.received_at|format_ts("%c") }}
-                            which is more than {{ "%.1f"|format(reason.delay_before_mail_ms / (60*1000)) }} ({{ reason.delay_before_mail_ms }}) mins ago,
-                            {%- if reason.last_sent_ts %}
-                                and the last time we sent a mail for this room was {{ reason.last_sent_ts|format_ts("%c") }},
-                                which is more than {{ "%.1f"|format(reason.throttle_ms / (60*1000)) }} (current throttle_ms) mins ago.
-                            {%- else %}
-                                and we don't have a last time we sent a mail for this room.
-                            {%- endif %}
-                        </div>
-                    </div>
-                </td>
-                <td> </td>
-            </tr>
-        </table>
-    </body>
-</html>
+{% block title %}New activity in room{% endblock %}
+
+{% block header %}
+<style type="text/css">
+    {%- include 'mail.css' without context %}
+    {%- include "mail-%s.css" % app_name ignore missing without context %}
+</style>
+{% endblock %}
+
+{% block body %}
+<table id="page">
+    <tr>
+        <td> </td>
+        <td id="inner">
+            <table class="header">
+                <tr>
+                    <td>
+                        <div class="salutation">Hi {{ user_display_name }},</div>
+                        <div class="summarytext">{{ summary_text }}</div>
+                    </td>
+                    <td class="logo">
+                        {%- if app_name == "Riot" %}
+                            <img src="http://riot.im/img/external/riot-logo-email.png" width="83" height="83" alt="[Riot]"/>
+                        {%- elif app_name == "Vector" %}
+                            <img src="http://matrix.org/img/vector-logo-email.png" width="64" height="83" alt="[Vector]"/>
+                        {%- elif app_name == "Element" %}
+                            <img src="https://static.element.io/images/email-logo.png" width="83" height="83" alt="[Element]"/>
+                        {%- else %}
+                            <img src="http://matrix.org/img/matrix-120x51.png" width="120" height="51" alt="[matrix]"/>
+                        {%- endif %}
+                    </td>
+                </tr>
+            </table>
+            {%- for room in rooms %}
+                {%- include 'room.html' with context %}
+            {%- endfor %}
+            <div class="footer">
+                <a href="{{ unsubscribe_link }}">Unsubscribe</a>
+                <br/>
+                <br/>
+                <div class="debug">
+                    Sending email at {{ reason.now|format_ts("%c") }} due to activity in room {{ reason.room_name }} because
+                    an event was received at {{ reason.received_at|format_ts("%c") }}
+                    which is more than {{ "%.1f"|format(reason.delay_before_mail_ms / (60*1000)) }} ({{ reason.delay_before_mail_ms }}) mins ago,
+                    {%- if reason.last_sent_ts %}
+                        and the last time we sent a mail for this room was {{ reason.last_sent_ts|format_ts("%c") }},
+                        which is more than {{ "%.1f"|format(reason.throttle_ms / (60*1000)) }} (current throttle_ms) mins ago.
+                    {%- else %}
+                        and we don't have a last time we sent a mail for this room.
+                    {%- endif %}
+                </div>
+            </div>
+        </td>
+        <td> </td>
+    </tr>
+</table>
+{% endblock %}
diff --git a/synapse/res/templates/password_reset.html b/synapse/res/templates/password_reset.html
index a8bdce357b..de5a9ec68f 100644
--- a/synapse/res/templates/password_reset.html
+++ b/synapse/res/templates/password_reset.html
@@ -1,14 +1,9 @@
-<html lang="en">
-    <head>
-        <title>Password reset</title>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    </head>
-<body>
-    <p>A password reset request has been received for your Matrix account. If this was you, please click the link below to confirm resetting your password:</p>
+{% block title %}Password reset{% endblock %}
 
-    <a href="{{ link }}">{{ link }}</a>
+{% block body %}
+<p>A password reset request has been received for your Matrix account. If this was you, please click the link below to confirm resetting your password:</p>
 
-    <p>If this was not you, <strong>do not</strong> click the link above and instead contact your server administrator. Thank you.</p>
-</body>
-</html>
+<a href="{{ link }}">{{ link }}</a>
+
+<p>If this was not you, <strong>do not</strong> click the link above and instead contact your server administrator. Thank you.</p>
+{% endblock %}
diff --git a/synapse/res/templates/password_reset_confirmation.html b/synapse/res/templates/password_reset_confirmation.html
index 2e3fd2ec1e..0eac64b6a8 100644
--- a/synapse/res/templates/password_reset_confirmation.html
+++ b/synapse/res/templates/password_reset_confirmation.html
@@ -1,10 +1,6 @@
-<html lang="en">
-<head>
-    <title>Password reset confirmation</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-</head>
-<body>
+{% block title %}Password reset confirmation{% endblock %}
+
+{% block body %}
 <!--Use a hidden form to resubmit the information necessary to reset the password-->
 <form method="post">
     <input type="hidden" name="sid" value="{{ sid }}">
@@ -15,6 +11,4 @@
         If you did not mean to do this, please close this page and your password will not be changed.</p>
     <p><button type="submit">Confirm changing my password</button></p>
 </form>
-</body>
-</html>
-
+{% endblock %}
diff --git a/synapse/res/templates/password_reset_failure.html b/synapse/res/templates/password_reset_failure.html
index 2d59c463f0..977babdb40 100644
--- a/synapse/res/templates/password_reset_failure.html
+++ b/synapse/res/templates/password_reset_failure.html
@@ -1,12 +1,6 @@
-<html lang="en">
-<head>
-    <title>Password reset failure</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-</head>
-<body>
-<p>The request failed for the following reason: {{ failure_reason }}.</p>
+{% block title %}Password reset failure{% endblock %}
 
+{% block body %}
+<p>The request failed for the following reason: {{ failure_reason }}.</p>
 <p>Your password has not been reset.</p>
-</body>
-</html>
+{% endblock %}
diff --git a/synapse/res/templates/password_reset_success.html b/synapse/res/templates/password_reset_success.html
index 5165bd1fa2..0e99fad7ff 100644
--- a/synapse/res/templates/password_reset_success.html
+++ b/synapse/res/templates/password_reset_success.html
@@ -1,9 +1,5 @@
-<html lang="en">
-<head>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-</head>
-<body>
+{% block title %}Password reset success{% endblock %}
+
+{% block body %}
 <p>Your email has now been validated, please return to your client to reset your password. You may now close this window.</p>
-</body>
-</html>
+{% endblock %}
diff --git a/synapse/res/templates/recaptcha.html b/synapse/res/templates/recaptcha.html
index 615d3239c6..feaf3f6aed 100644
--- a/synapse/res/templates/recaptcha.html
+++ b/synapse/res/templates/recaptcha.html
@@ -1,10 +1,7 @@
-<html>
-<head>
-<title>Authentication</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-<script src="https://www.recaptcha.net/recaptcha/api.js"
-    async defer></script>
+{% block title %}Authentication{% endblock %}
+
+{% block header %}
+<script src="https://www.recaptcha.net/recaptcha/api.js" async defer></script>
 <script src="//code.jquery.com/jquery-1.11.2.min.js"></script>
 <link rel="stylesheet" href="/_matrix/static/client/register/style.css">
 <script>
@@ -12,8 +9,9 @@ function captchaDone() {
     $('#registrationForm').submit();
 }
 </script>
-</head>
-<body>
+{% endblock %}
+
+{% block body %}
 <form id="registrationForm" method="post" action="{{ myurl }}">
     <div>
         {% if error is defined %}
@@ -37,5 +35,4 @@ function captchaDone() {
         </div>
     </div>
 </form>
-</body>
-</html>
+{% endblock %}
\ No newline at end of file
diff --git a/synapse/res/templates/registration.html b/synapse/res/templates/registration.html
index 20e831ff4a..189960a832 100644
--- a/synapse/res/templates/registration.html
+++ b/synapse/res/templates/registration.html
@@ -1,16 +1,11 @@
-<html lang="en">
-<head>
-    <title>Registration</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-</head>
-<body>
-    <p>You have asked us to register this email with a new Matrix account. If this was you, please click the link below to confirm your email address:</p>
+{% block title %}Registration{% endblock %}
 
-    <a href="{{ link }}">Verify Your Email Address</a>
+{% block body %}
+<p>You have asked us to register this email with a new Matrix account. If this was you, please click the link below to confirm your email address:</p>
 
-    <p>If this was not you, you can safely disregard this email.</p>
+<a href="{{ link }}">Verify Your Email Address</a>
 
-    <p>Thank you.</p>
-</body>
-</html>
+<p>If this was not you, you can safely disregard this email.</p>
+
+<p>Thank you.</p>
+{% endblock %}
diff --git a/synapse/res/templates/registration_failure.html b/synapse/res/templates/registration_failure.html
index a6ed22bc90..3debe9301d 100644
--- a/synapse/res/templates/registration_failure.html
+++ b/synapse/res/templates/registration_failure.html
@@ -1,9 +1,5 @@
-<html lang="en">
-<head>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-</head>
-<body>
+{% block title %}Registration failure{% endblock %}
+
+{% block body %}
 <p>Validation failed for the following reason: {{ failure_reason }}.</p>
-</body>
-</html>
+{% endblock %}
diff --git a/synapse/res/templates/registration_success.html b/synapse/res/templates/registration_success.html
index d51d5549d8..e2dd020a9e 100644
--- a/synapse/res/templates/registration_success.html
+++ b/synapse/res/templates/registration_success.html
@@ -1,10 +1,5 @@
-<html lang="en">
-<head>
-    <title>Your email has now been validated</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-</head>
-<body>
+{% block title %}Your email has now been validated{% endblock %}
+
+{% block body %}
 <p>Your email has now been validated, please return to your client. You may now close this window.</p>
-</body>
-</html>
+{% endblock %}
diff --git a/synapse/res/templates/registration_token.html b/synapse/res/templates/registration_token.html
index 59a98f564c..2ee5866ba5 100644
--- a/synapse/res/templates/registration_token.html
+++ b/synapse/res/templates/registration_token.html
@@ -1,11 +1,10 @@
-<html lang="en">
-<head>
-<title>Authentication</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+{% block title %}Authentication{% endblock %}
+
+{% block header %}
 <link rel="stylesheet" href="/_matrix/static/client/register/style.css">
-</head>
-<body>
+{% endblock %}
+
+{% block body %}
 <form id="registrationForm" method="post" action="{{ myurl }}">
     <div>
         {% if error is defined %}
@@ -19,5 +18,4 @@
         <input type="submit" value="Authenticate" />
     </div>
 </form>
-</body>
-</html>
+{% endblock %}
diff --git a/synapse/res/templates/sso_account_deactivated.html b/synapse/res/templates/sso_account_deactivated.html
index 075f801cec..c634229840 100644
--- a/synapse/res/templates/sso_account_deactivated.html
+++ b/synapse/res/templates/sso_account_deactivated.html
@@ -1,25 +1,24 @@
-<!DOCTYPE html>
-<html lang="en">
-    <head>
-        <meta charset="UTF-8">
-        <title>SSO account deactivated</title>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">        <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>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+{% block title %}SSO account deactivated{% endblock %}
+
+{% block header %}
+<style type="text/css">
+    {% include "sso.css" without context %}
+</style>
+{% endblock %}
+
+{% block body %}
+<div 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>
+</div>
+{% include "sso_footer.html" without context %}
+{% endblock %}
diff --git a/synapse/res/templates/sso_auth_account_details.html b/synapse/res/templates/sso_auth_account_details.html
index 2d1db386e1..b516333373 100644
--- a/synapse/res/templates/sso_auth_account_details.html
+++ b/synapse/res/templates/sso_auth_account_details.html
@@ -1,189 +1,185 @@
-<!DOCTYPE html>
-<html lang="en">
-  <head>
-    <title>Create your account</title>
-    <meta charset="utf-8">
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <script type="text/javascript">
-      let wasKeyboard = false;
-      document.addEventListener("mousedown", function() { wasKeyboard = false; });
-      document.addEventListener("keydown", function() { wasKeyboard = true; });
-      document.addEventListener("focusin", function() {
-        if (wasKeyboard) {
-          document.body.classList.add("keyboard-focus");
-        } else {
-          document.body.classList.remove("keyboard-focus");
-        }
-      });
-    </script>
-    <style type="text/css">
-      {% include "sso.css" without context %}
-
-      body.keyboard-focus :focus, body.keyboard-focus .username_input:focus-within {
-        outline: 3px solid #17191C;
-        outline-offset: 4px;
-      }
-
-      .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.invalid {
-        border-color: #FE2928;
-      }
-
-      .username_input.invalid input, .username_input.invalid label {
-        color: #FE2928;
-      }
-
-      .username_input div, .username_input input {
-        line-height: 18px;
-        font-size: 14px;
-      }
-
-      .username_input label {
-        position: absolute;
-        top: -5px;
-        left: 14px;
-        font-size: 10px;
-        line-height: 10px;
-        background: white;
-        padding: 0 2px;
-      }
-
-      .username_input input {
-        flex: 1;
-        display: block;
-        min-width: 0;
-        border: none;
-      }
-
-      /* only clear the outline if we know it will be shown on the parent div using :focus-within */
-      @supports selector(:focus-within) {
-        .username_input input {
-          outline: none !important;
-        }
-      }
-
-      .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;
-        display: block;
-      }
-      .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;
-      }
-
-      output {
-        padding: 0 14px;
-        display: block;
-      }
-
-      output.error {
-        color: #FE2928;
-      }
-    </style>
-  </head>
-  <body>
-    <header>
-      <h1>Create your account</h1>
-      <p>This is required. Continue to create your account on {{ server_name }}. You can't change this later.</p>
-    </header>
-    <main>
-      <form method="post" class="form__input" id="form">
-        <div class="username_input" id="username_input">
-          <label for="field-username">Username (required)</label>
-          <div class="prefix">@</div>
-          <input type="text" name="username" id="field-username" value="{{ user_attributes.localpart }}" autofocus autocorrect="off" autocapitalize="none">
-          <div class="postfix">:{{ server_name }}</div>
+{% block title %}Create your account{% endblock %}
+
+{% block header %}
+<script type="text/javascript">
+  let wasKeyboard = false;
+  document.addEventListener("mousedown", function() { wasKeyboard = false; });
+  document.addEventListener("keydown", function() { wasKeyboard = true; });
+  document.addEventListener("focusin", function() {
+    if (wasKeyboard) {
+      document.body.classList.add("keyboard-focus");
+    } else {
+      document.body.classList.remove("keyboard-focus");
+    }
+  });
+</script>
+<style type="text/css">
+  {% include "sso.css" without context %}
+
+  body.keyboard-focus :focus, body.keyboard-focus .username_input:focus-within {
+    outline: 3px solid #17191C;
+    outline-offset: 4px;
+  }
+
+  .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.invalid {
+    border-color: #FE2928;
+  }
+
+  .username_input.invalid input, .username_input.invalid label {
+    color: #FE2928;
+  }
+
+  .username_input div, .username_input input {
+    line-height: 18px;
+    font-size: 14px;
+  }
+
+  .username_input label {
+    position: absolute;
+    top: -5px;
+    left: 14px;
+    font-size: 10px;
+    line-height: 10px;
+    background: white;
+    padding: 0 2px;
+  }
+
+  .username_input input {
+    flex: 1;
+    display: block;
+    min-width: 0;
+    border: none;
+  }
+
+  /* only clear the outline if we know it will be shown on the parent div using :focus-within */
+  @supports selector(:focus-within) {
+    .username_input input {
+      outline: none !important;
+    }
+  }
+
+  .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;
+    display: block;
+  }
+  .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;
+  }
+
+  output {
+    padding: 0 14px;
+    display: block;
+  }
+
+  output.error {
+    color: #FE2928;
+  }
+</style>
+{% endblock %}
+
+{% block body %}
+<header>
+  <h1>Create your account</h1>
+  <p>This is required. Continue to create your account on {{ server_name }}. You can't change this later.</p>
+</header>
+<main>
+  <form method="post" class="form__input" id="form">
+    <div class="username_input" id="username_input">
+      <label for="field-username">Username (required)</label>
+      <div class="prefix">@</div>
+      <input type="text" name="username" id="field-username" value="{{ user_attributes.localpart }}" autofocus autocorrect="off" autocapitalize="none">
+      <div class="postfix">:{{ server_name }}</div>
+    </div>
+    <output for="username_input" id="field-username-output"></output>
+    <input type="submit" value="Continue" class="primary-button">
+    {% if user_attributes.avatar_url or user_attributes.display_name or user_attributes.emails %}
+    <section class="idp-pick-details">
+      <h2>{% if idp.idp_icon %}<img src="{{ idp.idp_icon | mxc_to_http(24, 24) }}"/>{% endif %}Optional data from {{ idp.idp_name }}</h2>
+      {% if user_attributes.avatar_url %}
+      <label class="idp-detail idp-avatar" for="idp-avatar">
+        <div class="check-row">
+          <span class="name">Avatar</span>
+          <span class="use">Use</span>
+          <input type="checkbox" name="use_avatar" id="idp-avatar" value="true" checked>
         </div>
-        <output for="username_input" id="field-username-output"></output>
-        <input type="submit" value="Continue" class="primary-button">
-        {% if user_attributes.avatar_url or user_attributes.display_name or user_attributes.emails %}
-        <section class="idp-pick-details">
-          <h2>{% if idp.idp_icon %}<img src="{{ idp.idp_icon | mxc_to_http(24, 24) }}"/>{% endif %}Optional data from {{ idp.idp_name }}</h2>
-          {% if user_attributes.avatar_url %}
-          <label class="idp-detail idp-avatar" for="idp-avatar">
-            <div class="check-row">
-              <span class="name">Avatar</span>
-              <span class="use">Use</span>
-              <input type="checkbox" name="use_avatar" id="idp-avatar" value="true" checked>
-            </div>
-            <img src="{{ user_attributes.avatar_url }}" class="avatar" />
-          </label>
-          {% endif %}
-          {% if user_attributes.display_name %}
-          <label class="idp-detail" for="idp-displayname">
-            <div class="check-row">
-              <span class="name">Display name</span>
-              <span class="use">Use</span>
-              <input type="checkbox" name="use_display_name" id="idp-displayname" value="true" checked>
-            </div>
-            <p class="idp-value">{{ user_attributes.display_name }}</p>
-          </label>
-          {% endif %}
-          {% for email in user_attributes.emails %}
-          <label class="idp-detail" for="idp-email{{ loop.index }}">
-            <div class="check-row">
-              <span class="name">E-mail</span>
-              <span class="use">Use</span>
-              <input type="checkbox" name="use_email" id="idp-email{{ loop.index }}" value="{{ email }}" checked>
-            </div>
-            <p class="idp-value">{{ email }}</p>
-          </label>
-          {% endfor %}
-        </section>
-        {% endif %}
-      </form>
-    </main>
-    {% include "sso_footer.html" without context %}
-    <script type="text/javascript">
-      {% include "sso_auth_account_details.js" without context %}
-    </script>
-  </body>
-</html>
+        <img src="{{ user_attributes.avatar_url }}" class="avatar" />
+      </label>
+      {% endif %}
+      {% if user_attributes.display_name %}
+      <label class="idp-detail" for="idp-displayname">
+        <div class="check-row">
+          <span class="name">Display name</span>
+          <span class="use">Use</span>
+          <input type="checkbox" name="use_display_name" id="idp-displayname" value="true" checked>
+        </div>
+        <p class="idp-value">{{ user_attributes.display_name }}</p>
+      </label>
+      {% endif %}
+      {% for email in user_attributes.emails %}
+      <label class="idp-detail" for="idp-email{{ loop.index }}">
+        <div class="check-row">
+          <span class="name">E-mail</span>
+          <span class="use">Use</span>
+          <input type="checkbox" name="use_email" id="idp-email{{ loop.index }}" value="{{ email }}" checked>
+        </div>
+        <p class="idp-value">{{ email }}</p>
+      </label>
+      {% endfor %}
+    </section>
+    {% endif %}
+  </form>
+</main>
+{% include "sso_footer.html" without context %}
+<script type="text/javascript">
+  {% include "sso_auth_account_details.js" without context %}
+</script>
+{% endblock %}
diff --git a/synapse/res/templates/sso_auth_bad_user.html b/synapse/res/templates/sso_auth_bad_user.html
index 94403fc3ce..69fdcc9ef0 100644
--- a/synapse/res/templates/sso_auth_bad_user.html
+++ b/synapse/res/templates/sso_auth_bad_user.html
@@ -1,27 +1,25 @@
-<!DOCTYPE html>
-<html lang="en">
-    <head>
-        <meta charset="UTF-8">
-        <title>Authentication failed</title>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <style type="text/css">
-            {% include "sso.css" without context %}
-        </style>
-    </head>
-    <body class="error_page">
-        <header>
-            <h1>That doesn't look right</h1>
-            <p>
-                <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>
-        </header>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+{% block title %}Authentication failed{% endblock %}
+
+{% block header %}
+<style type="text/css">
+    {% include "sso.css" without context %}
+</style>
+{% endblock %}
+
+{% block body %}
+<div class="error_page">
+    <header>
+        <h1>That doesn't look right</h1>
+        <p>
+            <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>
+    </header>
+</div>
+{% include "sso_footer.html" without context %}
+{% endblock %}
diff --git a/synapse/res/templates/sso_auth_confirm.html b/synapse/res/templates/sso_auth_confirm.html
index aa1c974a6b..2d106e0ae4 100644
--- a/synapse/res/templates/sso_auth_confirm.html
+++ b/synapse/res/templates/sso_auth_confirm.html
@@ -1,30 +1,26 @@
-<!DOCTYPE html>
-<html lang="en">
-    <head>
-        <meta charset="UTF-8">
-        <title>Confirm it's you</title>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <style type="text/css">
-            {% include "sso.css" without context %}
-        </style>
-    </head>
-    <body>
-        <header>
-            <h1>Confirm it's you to continue</h1>
-            <p>
-                A client is trying to {{ description }}. To confirm this action
-                re-authorize your account with single sign-on.
-            </p>
-            <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>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+{% block title %}Confirm it's you{% endblock %}
+
+{% block header %}
+<style type="text/css">
+    {% include "sso.css" without context %}
+</style>
+{% endblock %}
+
+{% block body %}
+<header>
+    <h1>Confirm it's you to continue</h1>
+    <p>
+        A client is trying to {{ description }}. To confirm this action
+        re-authorize your account with single sign-on.
+    </p>
+    <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>
+{% include "sso_footer.html" without context %}
+{% endblock %}
diff --git a/synapse/res/templates/sso_auth_success.html b/synapse/res/templates/sso_auth_success.html
index 4898af6011..56150eaefe 100644
--- a/synapse/res/templates/sso_auth_success.html
+++ b/synapse/res/templates/sso_auth_success.html
@@ -1,29 +1,25 @@
-<!DOCTYPE html>
-<html lang="en">
-    <head>
-        <meta charset="UTF-8">
-        <title>Authentication successful</title>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <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>
-        <header>
-            <h1>Thank you</h1>
-            <p>
-                Now we know it’s you, you can close this window and return to the
-                application.
-            </p>
-        </header>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+{% block title %}Authentication successful{% endblock %}
+
+{% block header %}
+<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>
+{% endblock %}
+
+{% block body %}
+<header>
+    <h1>Thank you</h1>
+    <p>
+        Now we know it’s you, you can close this window and return to the
+        application.
+    </p>
+</header>
+{% include "sso_footer.html" without context %}
+{% endblock %}
diff --git a/synapse/res/templates/sso_error.html b/synapse/res/templates/sso_error.html
index 19992ff2ad..e394a92623 100644
--- a/synapse/res/templates/sso_error.html
+++ b/synapse/res/templates/sso_error.html
@@ -1,19 +1,19 @@
-<!DOCTYPE html>
-<html lang="en">
-    <head>
-        <meta charset="UTF-8">
-        <title>Authentication failed</title>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <style type="text/css">
-            {% include "sso.css" without context %}
+{% block title %}Authentication failed{% endblock %}
 
-            #error_code {
-                margin-top: 56px;
-            }
-        </style>
-    </head>
-    <body class="error_page">
+{% block header %}
+{% if error == "unauthorised" %}
+<style type="text/css">
+    {% include "sso.css" without context %}
+
+    #error_code {
+        margin-top: 56px;
+    }
+</style>
+{% endif %}
+{% endblock %}
+
+{% block body %}
+<div class="error_page">
 {# If an error of unauthorised is returned it means we have actively rejected their login #}
 {% if error == "unauthorised" %}
         <header>
@@ -66,5 +66,5 @@
             }
         </script>
 {% endif %}
-</body>
-</html>
+</div>
+{% endblock %}
diff --git a/synapse/res/templates/sso_login_idp_picker.html b/synapse/res/templates/sso_login_idp_picker.html
index 56fabfa3d2..a2772ca9ef 100644
--- a/synapse/res/templates/sso_login_idp_picker.html
+++ b/synapse/res/templates/sso_login_idp_picker.html
@@ -1,63 +1,59 @@
-<!DOCTYPE html>
-<html lang="en">
-    <head>
-        <meta http-equiv="X-UA-Compatible" content="IE=edge">
-        <meta name="viewport" content="width=device-width, initial-scale=1.0">
-        <meta charset="UTF-8">
-        <title>Choose identity provider</title>
-        <style type="text/css">
-          {% include "sso.css" without context %}
+{% block title %}Choose identity provider{% endblock %}
 
-          .providers {
-            list-style: none;
-            padding: 0;
-          }
+{% block header %}
+<style type="text/css">
+  {% include "sso.css" without context %}
 
-          .providers li {
-            margin: 12px;
-          }
+  .providers {
+    list-style: none;
+    padding: 0;
+  }
 
-          .providers a {
-            display: block;
-            border-radius: 4px;
-            border: 1px solid #17191C;
-            padding: 8px;
-            text-align: center;
-            text-decoration: none;
-            color: #17191C;
-            display: flex;
-            align-items: center;
-            font-weight: bold;
-          }
+  .providers li {
+    margin: 12px;
+  }
 
-          .providers a img {
-            width: 24px;
-            height: 24px;
-          }
-          .providers a span {
-            flex: 1;
-          }
-        </style>
-    </head>
-    <body>
-        <header>
-            <h1>Log in to {{ server_name }} </h1>
-            <p>Choose an identity provider to log in</p>
-        </header>
-        <main>
-            <ul class="providers">
-                {% for p in providers %}
-                <li>
-                    <a href="pick_idp?idp={{ p.idp_id }}&redirectUrl={{ redirect_url | urlencode }}">
-                        {% if p.idp_icon %}
-                        <img src="{{ p.idp_icon | mxc_to_http(32, 32) }}"/>
-                        {% endif %}
-                        <span>{{ p.idp_name }}</span>
-                    </a>
-                </li>
-                {% endfor %}
-            </ul>
-        </main>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+  .providers a {
+    display: block;
+    border-radius: 4px;
+    border: 1px solid #17191C;
+    padding: 8px;
+    text-align: center;
+    text-decoration: none;
+    color: #17191C;
+    display: flex;
+    align-items: center;
+    font-weight: bold;
+  }
+
+  .providers a img {
+    width: 24px;
+    height: 24px;
+  }
+  .providers a span {
+    flex: 1;
+  }
+</style>
+{% endblock %}
+
+{% block body %}
+<header>
+    <h1>Log in to {{ server_name }} </h1>
+    <p>Choose an identity provider to log in</p>
+</header>
+<main>
+    <ul class="providers">
+        {% for p in providers %}
+        <li>
+            <a href="pick_idp?idp={{ p.idp_id }}&redirectUrl={{ redirect_url | urlencode }}">
+                {% if p.idp_icon %}
+                <img src="{{ p.idp_icon | mxc_to_http(32, 32) }}"/>
+                {% endif %}
+                <span>{{ p.idp_name }}</span>
+            </a>
+        </li>
+        {% endfor %}
+    </ul>
+</main>
+{% include "sso_footer.html" without context %}
+{% endblock %}
diff --git a/synapse/res/templates/sso_new_user_consent.html b/synapse/res/templates/sso_new_user_consent.html
index 523f64c4fc..126887d26c 100644
--- a/synapse/res/templates/sso_new_user_consent.html
+++ b/synapse/res/templates/sso_new_user_consent.html
@@ -1,33 +1,29 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <title>Agree to terms and conditions</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <style type="text/css">
-      {% include "sso.css" without context %}
+{% block title %}Agree to terms and conditions{% endblock %}
 
-      #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>
-            {% include "sso_partial_profile.html" %}
-            <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" rel="noopener">terms and conditions</a>.</label>
-                </p>
-                <input type="submit" class="primary-button" value="Continue"/>
-            </form>
-        </main>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+{% block header %}
+<style type="text/css">
+    {% include "sso.css" without context %}
+
+    #consent_form {
+      margin-top: 56px;
+    }
+</style>
+{% endblock %}
+
+{% block body %}
+<header>
+    <h1>Your account is nearly ready</h1>
+    <p>Agree to the terms to create your account.</p>
+</header>
+<main>
+    {% include "sso_partial_profile.html" %}
+    <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" rel="noopener">terms and conditions</a>.</label>
+        </p>
+        <input type="submit" class="primary-button" value="Continue"/>
+    </form>
+</main>
+{% include "sso_footer.html" without context %}
+{% endblock %}
diff --git a/synapse/res/templates/sso_redirect_confirm.html b/synapse/res/templates/sso_redirect_confirm.html
index 1049a9bd92..887ee0d294 100644
--- a/synapse/res/templates/sso_redirect_confirm.html
+++ b/synapse/res/templates/sso_redirect_confirm.html
@@ -1,41 +1,38 @@
-<!DOCTYPE html>
-<html lang="en">
-<head>
-    <meta charset="UTF-8">
-    <title>Continue to your account</title>
-    <meta http-equiv="X-UA-Compatible" content="IE=edge">
-    <meta name="viewport" content="width=device-width, initial-scale=1.0">
-    <style type="text/css">
-      {% include "sso.css" without context %}
+{% block title %}Continue to your account{% endblock %}
 
-      .confirm-trust {
-        margin: 34px 0;
-        color: #8D99A5;
-      }
-      .confirm-trust strong {
-        color: #17191C;
-      }
+{% block header %}
+<style type="text/css">
+  {% include "sso.css" without context %}
 
-      .confirm-trust::before {
-        content: "";
-        background-image: url('data:image/svg+xml;base64,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');
-        background-repeat: no-repeat;
-        width: 24px;
-        height: 24px;
-        display: block;
-        float: left;
-      }
-    </style>
-</head>
-    <body>
-        <header>
-            <h1>Continue to your account</h1>
-        </header>
-        <main>
-            {% include "sso_partial_profile.html" %}
-            <p class="confirm-trust">Continuing will grant <strong>{{ display_url }}</strong> access to your account.</p>
-            <a href="{{ redirect_url }}" class="primary-button">Continue</a>
-        </main>
-        {% include "sso_footer.html" without context %}
-    </body>
-</html>
+  .confirm-trust {
+    margin: 34px 0;
+    color: #8D99A5;
+  }
+  .confirm-trust strong {
+    color: #17191C;
+  }
+
+  .confirm-trust::before {
+    content: "";
+    background-image: url('data:image/svg+xml;base64,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');
+    background-repeat: no-repeat;
+    width: 24px;
+    height: 24px;
+    display: block;
+    float: left;
+  }
+</style>
+{% endblock %}
+
+{% block body %}
+<header>
+    <h1>Continue to your account</h1>
+</header>
+<main>
+    {% include "sso_partial_profile.html" %}
+    <p class="confirm-trust">Continuing will grant <strong>{{ display_url }}</strong> access to your account.</p>
+    <a href="{{ redirect_url }}" class="primary-button">Continue</a>
+</main>
+{% include "sso_footer.html" without context %}
+
+{% endblock %}
diff --git a/synapse/res/templates/style.css b/synapse/res/templates/style.css
new file mode 100644
index 0000000000..097b235ae5
--- /dev/null
+++ b/synapse/res/templates/style.css
@@ -0,0 +1,29 @@
+html {
+    height: 100%;
+}
+
+body {
+    background: #f9fafb;
+    max-width: 680px;
+    margin: auto;
+    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
+}
+
+.mx_Header {
+    border-bottom: 3px solid #ddd;
+    margin-bottom: 1rem;
+    padding-top: 1rem;
+    padding-bottom: 1rem;
+    text-align: center;
+}
+
+@media screen and (max-width: 1120px) {
+    body {
+        font-size: 20px;
+    }
+
+    h1 { font-size: 1rem; }
+    h2 { font-size: .9rem; }
+    h3 { font-size: .85rem; }
+    h4 { font-size: .8rem; }
+}
diff --git a/synapse/res/templates/terms.html b/synapse/res/templates/terms.html
index 2081d990ab..977c3d0bc7 100644
--- a/synapse/res/templates/terms.html
+++ b/synapse/res/templates/terms.html
@@ -1,11 +1,10 @@
-<html>
-<head>
-<title>Authentication</title>
-<meta http-equiv="X-UA-Compatible" content="IE=edge">
-<meta name="viewport" content="width=device-width, initial-scale=1.0">
+{% block title %}Authentication{% endblock %}
+
+{% block header %}
 <link rel="stylesheet" href="/_matrix/static/client/register/style.css">
-</head>
-<body>
+{% endblock %}
+
+{% block body %}
 <form id="registrationForm" method="post" action="{{ myurl }}">
     <div>
         {% if error is defined %}
@@ -19,5 +18,4 @@
         <input type="submit" value="Agree" />
     </div>
 </form>
-</body>
-</html>
+{% endblock %}
diff --git a/synapse/rest/client/capabilities.py b/synapse/rest/client/capabilities.py
index 4237071c61..e84dde31b1 100644
--- a/synapse/rest/client/capabilities.py
+++ b/synapse/rest/client/capabilities.py
@@ -77,6 +77,11 @@ class CapabilitiesRestServlet(RestServlet):
                 "enabled": True,
             }
 
+        if self.config.experimental.msc3664_enabled:
+            response["capabilities"]["im.nheko.msc3664.related_event_match"] = {
+                "enabled": self.config.experimental.msc3664_enabled,
+            }
+
         return HTTPStatus.OK, response
 
 
diff --git a/synapse/rest/client/devices.py b/synapse/rest/client/devices.py
index 90828c95c4..8f3cbd4ea2 100644
--- a/synapse/rest/client/devices.py
+++ b/synapse/rest/client/devices.py
@@ -231,7 +231,7 @@ class DehydratedDeviceServlet(RestServlet):
       }
     }
 
-    PUT /org.matrix.msc2697/dehydrated_device
+    PUT /org.matrix.msc2697.v2/dehydrated_device
     Content-Type: application/json
 
     {
@@ -271,7 +271,6 @@ class DehydratedDeviceServlet(RestServlet):
             raise errors.NotFoundError("No dehydrated device available")
 
     class PutBody(RequestBodyModel):
-        device_id: StrictStr
         device_data: DehydratedDeviceDataModel
         initial_device_display_name: Optional[StrictStr]
 
@@ -281,7 +280,7 @@ class DehydratedDeviceServlet(RestServlet):
 
         device_id = await self.device_handler.store_dehydrated_device(
             requester.user.to_string(),
-            submission.device_data,
+            submission.device_data.dict(),
             submission.initial_device_display_name,
         )
         return 200, {"device_id": device_id}
diff --git a/synapse/rest/client/login.py b/synapse/rest/client/login.py
index f554586ac3..7774f1967d 100644
--- a/synapse/rest/client/login.py
+++ b/synapse/rest/client/login.py
@@ -436,8 +436,7 @@ class LoginRestServlet(RestServlet):
             The body of the JSON response.
         """
         token = login_submission["token"]
-        auth_handler = self.auth_handler
-        res = await auth_handler.validate_short_term_login_token(token)
+        res = await self.auth_handler.consume_login_token(token)
 
         return await self._complete_login(
             res.user_id,
diff --git a/synapse/rest/client/login_token_request.py b/synapse/rest/client/login_token_request.py
index 277b20fb63..43ea21d5e6 100644
--- a/synapse/rest/client/login_token_request.py
+++ b/synapse/rest/client/login_token_request.py
@@ -57,7 +57,6 @@ class LoginTokenRequestServlet(RestServlet):
         self.store = hs.get_datastores().main
         self.clock = hs.get_clock()
         self.server_name = hs.config.server.server_name
-        self.macaroon_gen = hs.get_macaroon_generator()
         self.auth_handler = hs.get_auth_handler()
         self.token_timeout = hs.config.experimental.msc3882_token_timeout
         self.ui_auth = hs.config.experimental.msc3882_ui_auth
@@ -76,10 +75,10 @@ class LoginTokenRequestServlet(RestServlet):
                 can_skip_ui_auth=False,  # Don't allow skipping of UI auth
             )
 
-        login_token = self.macaroon_gen.generate_short_term_login_token(
+        login_token = await self.auth_handler.create_login_token_for_user_id(
             user_id=requester.user.to_string(),
             auth_provider_id="org.matrix.msc3882.login_token_request",
-            duration_in_ms=self.token_timeout,
+            duration_ms=self.token_timeout,
         )
 
         return (
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index 01e5079963..91cb791139 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -52,6 +52,7 @@ from synapse.http.servlet import (
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.logging.opentracing import set_tag
+from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.rest.client._base import client_patterns
 from synapse.rest.client.transactions import HttpTransactionCache
 from synapse.storage.state import StateFilter
@@ -1029,6 +1030,8 @@ class RoomRedactEventRestServlet(TransactionRestServlet):
         super().__init__(hs)
         self.event_creation_handler = hs.get_event_creation_handler()
         self.auth = hs.get_auth()
+        self._relation_handler = hs.get_relations_handler()
+        self._msc3912_enabled = hs.config.experimental.msc3912_enabled
 
     def register(self, http_server: HttpServer) -> None:
         PATTERNS = "/rooms/(?P<room_id>[^/]*)/redact/(?P<event_id>[^/]*)"
@@ -1045,20 +1048,46 @@ class RoomRedactEventRestServlet(TransactionRestServlet):
         content = parse_json_object_from_request(request)
 
         try:
-            (
-                event,
-                _,
-            ) = await self.event_creation_handler.create_and_send_nonmember_event(
-                requester,
-                {
-                    "type": EventTypes.Redaction,
-                    "content": content,
-                    "room_id": room_id,
-                    "sender": requester.user.to_string(),
-                    "redacts": event_id,
-                },
-                txn_id=txn_id,
-            )
+            with_relations = None
+            if self._msc3912_enabled and "org.matrix.msc3912.with_relations" in content:
+                with_relations = content["org.matrix.msc3912.with_relations"]
+                del content["org.matrix.msc3912.with_relations"]
+
+            # Check if there's an existing event for this transaction now (even though
+            # create_and_send_nonmember_event also does it) because, if there's one,
+            # then we want to skip the call to redact_events_related_to.
+            event = None
+            if txn_id:
+                event = await self.event_creation_handler.get_event_from_transaction(
+                    requester, txn_id, room_id
+                )
+
+            if event is None:
+                (
+                    event,
+                    _,
+                ) = await self.event_creation_handler.create_and_send_nonmember_event(
+                    requester,
+                    {
+                        "type": EventTypes.Redaction,
+                        "content": content,
+                        "room_id": room_id,
+                        "sender": requester.user.to_string(),
+                        "redacts": event_id,
+                    },
+                    txn_id=txn_id,
+                )
+
+                if with_relations:
+                    run_as_background_process(
+                        "redact_related_events",
+                        self._relation_handler.redact_events_related_to,
+                        requester=requester,
+                        event_id=event_id,
+                        initial_redaction_event=event,
+                        relation_types=with_relations,
+                    )
+
             event_id = event.event_id
         except ShadowBanError:
             event_id = "$" + random_string(43)
diff --git a/synapse/rest/client/room_batch.py b/synapse/rest/client/room_batch.py
index dd91dabedd..10be4a781b 100644
--- a/synapse/rest/client/room_batch.py
+++ b/synapse/rest/client/room_batch.py
@@ -108,6 +108,13 @@ class RoomBatchSendEventRestServlet(RestServlet):
                 errcode=Codes.MISSING_PARAM,
             )
 
+        if await self.store.is_partial_state_room(room_id):
+            raise SynapseError(
+                HTTPStatus.BAD_REQUEST,
+                "Cannot insert history batches until we have fully joined the room",
+                errcode=Codes.UNABLE_DUE_TO_PARTIAL_STATE,
+            )
+
         # Verify the batch_id_from_query corresponds to an actual insertion event
         # and have the batch connected.
         if batch_id_from_query:
diff --git a/synapse/rest/client/sync.py b/synapse/rest/client/sync.py
index 8a16459105..f2013faeb2 100644
--- a/synapse/rest/client/sync.py
+++ b/synapse/rest/client/sync.py
@@ -146,12 +146,12 @@ class SyncRestServlet(RestServlet):
         elif filter_id.startswith("{"):
             try:
                 filter_object = json_decoder.decode(filter_id)
-                set_timeline_upper_limit(
-                    filter_object, self.hs.config.server.filter_timeline_limit
-                )
             except Exception:
-                raise SynapseError(400, "Invalid filter JSON")
+                raise SynapseError(400, "Invalid filter JSON", errcode=Codes.NOT_JSON)
             self.filtering.check_valid_filter(filter_object)
+            set_timeline_upper_limit(
+                filter_object, self.hs.config.server.filter_timeline_limit
+            )
             filter_collection = FilterCollection(self.hs, filter_object)
         else:
             try:
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index 9b1b72c68a..180a11ef88 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -119,6 +119,8 @@ class VersionsRestServlet(RestServlet):
                     # Adds support for simple HTTP rendezvous as per MSC3886
                     "org.matrix.msc3886": self.config.experimental.msc3886_endpoint
                     is not None,
+                    # Adds support for relation-based redactions as per MSC3912.
+                    "org.matrix.msc3912": self.config.experimental.msc3912_enabled,
                 },
             },
         )
diff --git a/synapse/rest/synapse/client/oidc/__init__.py b/synapse/rest/synapse/client/oidc/__init__.py
index 81fec39659..e4b28ce3df 100644
--- a/synapse/rest/synapse/client/oidc/__init__.py
+++ b/synapse/rest/synapse/client/oidc/__init__.py
@@ -17,6 +17,9 @@ from typing import TYPE_CHECKING
 
 from twisted.web.resource import Resource
 
+from synapse.rest.synapse.client.oidc.backchannel_logout_resource import (
+    OIDCBackchannelLogoutResource,
+)
 from synapse.rest.synapse.client.oidc.callback_resource import OIDCCallbackResource
 
 if TYPE_CHECKING:
@@ -29,6 +32,7 @@ class OIDCResource(Resource):
     def __init__(self, hs: "HomeServer"):
         Resource.__init__(self)
         self.putChild(b"callback", OIDCCallbackResource(hs))
+        self.putChild(b"backchannel_logout", OIDCBackchannelLogoutResource(hs))
 
 
 __all__ = ["OIDCResource"]
diff --git a/synapse/rest/synapse/client/oidc/backchannel_logout_resource.py b/synapse/rest/synapse/client/oidc/backchannel_logout_resource.py
new file mode 100644
index 0000000000..e07e76855a
--- /dev/null
+++ b/synapse/rest/synapse/client/oidc/backchannel_logout_resource.py
@@ -0,0 +1,35 @@
+# Copyright 2022 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 synapse.http.server import DirectServeJsonResource
+from synapse.http.site import SynapseRequest
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+class OIDCBackchannelLogoutResource(DirectServeJsonResource):
+    isLeaf = 1
+
+    def __init__(self, hs: "HomeServer"):
+        super().__init__()
+        self._oidc_handler = hs.get_oidc_handler()
+
+    async def _async_render_POST(self, request: SynapseRequest) -> None:
+        await self._oidc_handler.handle_backchannel_logout(request)
diff --git a/synapse/storage/databases/main/__init__.py b/synapse/storage/databases/main/__init__.py
index a62b4abd4e..cfaedf5e0c 100644
--- a/synapse/storage/databases/main/__init__.py
+++ b/synapse/storage/databases/main/__init__.py
@@ -201,7 +201,7 @@ class DataStore(
         name: Optional[str] = None,
         guests: bool = True,
         deactivated: bool = False,
-        order_by: str = UserSortOrder.USER_ID.value,
+        order_by: str = UserSortOrder.NAME.value,
         direction: str = "f",
         approved: bool = True,
     ) -> Tuple[List[JsonDict], int]:
@@ -261,6 +261,7 @@ class DataStore(
             sql_base = f"""
                 FROM users as u
                 LEFT JOIN profiles AS p ON u.name = '@' || p.user_id || ':' || ?
+                LEFT JOIN erased_users AS eu ON u.name = eu.user_id
                 {where_clause}
                 """
             sql = "SELECT COUNT(*) as total_users " + sql_base
@@ -269,7 +270,8 @@ class DataStore(
 
             sql = f"""
                 SELECT name, user_type, is_guest, admin, deactivated, shadow_banned,
-                displayname, avatar_url, creation_ts * 1000 as creation_ts, approved
+                displayname, avatar_url, creation_ts * 1000 as creation_ts, approved,
+                eu.user_id is not null as erased
                 {sql_base}
                 ORDER BY {order_by_column} {order}, u.name ASC
                 LIMIT ? OFFSET ?
@@ -277,6 +279,13 @@ class DataStore(
             args += [limit, start]
             txn.execute(sql, args)
             users = self.db_pool.cursor_to_dict(txn)
+
+            # some of those boolean values are returned as integers when we're on SQLite
+            columns_to_boolify = ["erased"]
+            for user in users:
+                for column in columns_to_boolify:
+                    user[column] = bool(user[column])
+
             return users, count
 
         return await self.db_pool.runInteraction(
diff --git a/synapse/storage/databases/main/appservice.py b/synapse/storage/databases/main/appservice.py
index 64b70a7b28..63046c0527 100644
--- a/synapse/storage/databases/main/appservice.py
+++ b/synapse/storage/databases/main/appservice.py
@@ -157,10 +157,23 @@ class ApplicationServiceWorkerStore(RoomMemberWorkerStore):
         app_service: "ApplicationService",
         cache_context: _CacheContext,
     ) -> List[str]:
-        users_in_room = await self.get_users_in_room(
+        """
+        Get all users in a room that the appservice controls.
+
+        Args:
+            room_id: The room to check in.
+            app_service: The application service to check interest/control against
+
+        Returns:
+            List of user IDs that the appservice controls.
+        """
+        # We can use `get_local_users_in_room(...)` here because an application service
+        # can only be interested in local users of the server it's on (ignore any remote
+        # users that might match the user namespace regex).
+        local_users_in_room = await self.get_local_users_in_room(
             room_id, on_invalidate=cache_context.invalidate
         )
-        return list(filter(app_service.is_interested_in_user, users_in_room))
+        return list(filter(app_service.is_interested_in_user, local_users_in_room))
 
 
 class ApplicationServiceStore(ApplicationServiceWorkerStore):
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index 830b076a32..979dd4e17e 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -274,6 +274,13 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
             destination, int(from_stream_id)
         )
         if not has_changed:
+            # debugging for https://github.com/matrix-org/synapse/issues/14251
+            issue_8631_logger.debug(
+                "%s: no change between %i and %i",
+                destination,
+                from_stream_id,
+                now_stream_id,
+            )
             return now_stream_id, []
 
         updates = await self.db_pool.runInteraction(
@@ -1848,7 +1855,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         self,
         txn: LoggingTransaction,
         user_id: str,
-        device_ids: Iterable[str],
+        device_id: str,
         hosts: Collection[str],
         stream_ids: List[int],
         context: Optional[Dict[str, str]],
@@ -1864,6 +1871,21 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
         stream_id_iterator = iter(stream_ids)
 
         encoded_context = json_encoder.encode(context)
+        mark_sent = not self.hs.is_mine_id(user_id)
+
+        values = [
+            (
+                destination,
+                next(stream_id_iterator),
+                user_id,
+                device_id,
+                mark_sent,
+                now,
+                encoded_context if whitelisted_homeserver(destination) else "{}",
+            )
+            for destination in hosts
+        ]
+
         self.db_pool.simple_insert_many_txn(
             txn,
             table="device_lists_outbound_pokes",
@@ -1876,23 +1898,21 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
                 "ts",
                 "opentracing_context",
             ),
-            values=[
-                (
-                    destination,
-                    next(stream_id_iterator),
-                    user_id,
-                    device_id,
-                    not self.hs.is_mine_id(
-                        user_id
-                    ),  # We only need to send out update for *our* users
-                    now,
-                    encoded_context if whitelisted_homeserver(destination) else "{}",
-                )
-                for destination in hosts
-                for device_id in device_ids
-            ],
+            values=values,
         )
 
+        # debugging for https://github.com/matrix-org/synapse/issues/14251
+        if issue_8631_logger.isEnabledFor(logging.DEBUG):
+            issue_8631_logger.debug(
+                "Recorded outbound pokes for %s:%s with device stream ids %s",
+                user_id,
+                device_id,
+                {
+                    stream_id: destination
+                    for (destination, stream_id, _, _, _, _, _) in values
+                },
+            )
+
     def _add_device_outbound_room_poke_txn(
         self,
         txn: LoggingTransaction,
@@ -1997,7 +2017,7 @@ class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
                 self._add_device_outbound_poke_to_stream_txn(
                     txn,
                     user_id=user_id,
-                    device_ids=[device_id],
+                    device_id=device_id,
                     hosts=hosts,
                     stream_ids=stream_ids,
                     context=context,
diff --git a/synapse/storage/databases/main/end_to_end_keys.py b/synapse/storage/databases/main/end_to_end_keys.py
index 8a10ae800c..2a4f58ed92 100644
--- a/synapse/storage/databases/main/end_to_end_keys.py
+++ b/synapse/storage/databases/main/end_to_end_keys.py
@@ -139,11 +139,15 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore, CacheInvalidationWorker
     @trace
     @cancellable
     async def get_e2e_device_keys_for_cs_api(
-        self, query_list: List[Tuple[str, Optional[str]]]
+        self,
+        query_list: List[Tuple[str, Optional[str]]],
+        include_displaynames: bool = True,
     ) -> Dict[str, Dict[str, JsonDict]]:
         """Fetch a list of device keys, formatted suitably for the C/S API.
         Args:
-            query_list(list): List of pairs of user_ids and device_ids.
+            query_list: List of pairs of user_ids and device_ids.
+            include_displaynames: Whether to include the displayname of returned devices
+                (if one exists).
         Returns:
             Dict mapping from user-id to dict mapping from device_id to
             key data.  The key data will be a dict in the same format as the
@@ -166,9 +170,12 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore, CacheInvalidationWorker
                     continue
 
                 r["unsigned"] = {}
-                display_name = device_info.display_name
-                if display_name is not None:
-                    r["unsigned"]["device_display_name"] = display_name
+                if include_displaynames:
+                    # Include the device's display name in the "unsigned" dictionary
+                    display_name = device_info.display_name
+                    if display_name is not None:
+                        r["unsigned"]["device_display_name"] = display_name
+
                 rv[user_id][device_id] = r
 
         return rv
diff --git a/synapse/storage/databases/main/events.py b/synapse/storage/databases/main/events.py
index 6698cbf664..00880bb37d 100644
--- a/synapse/storage/databases/main/events.py
+++ b/synapse/storage/databases/main/events.py
@@ -2028,25 +2028,37 @@ class PersistEventsStore:
             redacted_event_id: The event that was redacted.
         """
 
-        # Fetch the current relation of the event being redacted.
-        redacted_relates_to = self.db_pool.simple_select_one_onecol_txn(
+        # Fetch the relation of the event being redacted.
+        row = self.db_pool.simple_select_one_txn(
             txn,
             table="event_relations",
             keyvalues={"event_id": redacted_event_id},
-            retcol="relates_to_id",
+            retcols=("relates_to_id", "relation_type"),
             allow_none=True,
         )
+        # Nothing to do if no relation is found.
+        if row is None:
+            return
+
+        redacted_relates_to = row["relates_to_id"]
+        rel_type = row["relation_type"]
+        self.db_pool.simple_delete_txn(
+            txn, table="event_relations", keyvalues={"event_id": redacted_event_id}
+        )
+
         # Any relation information for the related event must be cleared.
-        if redacted_relates_to is not None:
-            self.store._invalidate_cache_and_stream(
-                txn, self.store.get_relations_for_event, (redacted_relates_to,)
-            )
+        self.store._invalidate_cache_and_stream(
+            txn, self.store.get_relations_for_event, (redacted_relates_to,)
+        )
+        if rel_type == RelationTypes.ANNOTATION:
             self.store._invalidate_cache_and_stream(
                 txn, self.store.get_aggregation_groups_for_event, (redacted_relates_to,)
             )
+        if rel_type == RelationTypes.REPLACE:
             self.store._invalidate_cache_and_stream(
                 txn, self.store.get_applicable_edit, (redacted_relates_to,)
             )
+        if rel_type == RelationTypes.THREAD:
             self.store._invalidate_cache_and_stream(
                 txn, self.store.get_thread_summary, (redacted_relates_to,)
             )
@@ -2057,9 +2069,38 @@ class PersistEventsStore:
                 txn, self.store.get_threads, (room_id,)
             )
 
-        self.db_pool.simple_delete_txn(
-            txn, table="event_relations", keyvalues={"event_id": redacted_event_id}
-        )
+            # Find the new latest event in the thread.
+            sql = """
+            SELECT event_id, topological_ordering, stream_ordering
+            FROM event_relations
+            INNER JOIN events USING (event_id)
+            WHERE relates_to_id = ? AND relation_type = ?
+            ORDER BY topological_ordering DESC, stream_ordering DESC
+            LIMIT 1
+            """
+            txn.execute(sql, (redacted_relates_to, RelationTypes.THREAD))
+
+            # If a latest event is found, update the threads table, this might
+            # be the same current latest event (if an earlier event in the thread
+            # was redacted).
+            latest_event_row = txn.fetchone()
+            if latest_event_row:
+                self.db_pool.simple_upsert_txn(
+                    txn,
+                    table="threads",
+                    keyvalues={"room_id": room_id, "thread_id": redacted_relates_to},
+                    values={
+                        "latest_event_id": latest_event_row[0],
+                        "topological_ordering": latest_event_row[1],
+                        "stream_ordering": latest_event_row[2],
+                    },
+                )
+
+            # Otherwise, delete the thread: it no longer exists.
+            else:
+                self.db_pool.simple_delete_one_txn(
+                    txn, table="threads", keyvalues={"thread_id": redacted_relates_to}
+                )
 
     def _store_room_topic_txn(self, txn: LoggingTransaction, event: EventBase) -> None:
         if isinstance(event.content.get("topic"), str):
diff --git a/synapse/storage/databases/main/push_rule.py b/synapse/storage/databases/main/push_rule.py
index 51416b2236..b6c15f29f8 100644
--- a/synapse/storage/databases/main/push_rule.py
+++ b/synapse/storage/databases/main/push_rule.py
@@ -29,6 +29,7 @@ from typing import (
 )
 
 from synapse.api.errors import StoreError
+from synapse.config.homeserver import ExperimentalConfig
 from synapse.replication.slave.storage._slaved_id_tracker import SlavedIdTracker
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import (
@@ -62,7 +63,9 @@ logger = logging.getLogger(__name__)
 
 
 def _load_rules(
-    rawrules: List[JsonDict], enabled_map: Dict[str, bool]
+    rawrules: List[JsonDict],
+    enabled_map: Dict[str, bool],
+    experimental_config: ExperimentalConfig,
 ) -> FilteredPushRules:
     """Take the DB rows returned from the DB and convert them into a full
     `FilteredPushRules` object.
@@ -80,7 +83,9 @@ def _load_rules(
 
     push_rules = PushRules(ruleslist)
 
-    filtered_rules = FilteredPushRules(push_rules, enabled_map)
+    filtered_rules = FilteredPushRules(
+        push_rules, enabled_map, msc3664_enabled=experimental_config.msc3664_enabled
+    )
 
     return filtered_rules
 
@@ -160,7 +165,7 @@ class PushRulesWorkerStore(
 
         enabled_map = await self.get_push_rules_enabled_for_user(user_id)
 
-        return _load_rules(rows, enabled_map)
+        return _load_rules(rows, enabled_map, self.hs.config.experimental)
 
     async def get_push_rules_enabled_for_user(self, user_id: str) -> Dict[str, bool]:
         results = await self.db_pool.simple_select_list(
@@ -219,7 +224,9 @@ class PushRulesWorkerStore(
         results: Dict[str, FilteredPushRules] = {}
 
         for user_id, rules in raw_rules.items():
-            results[user_id] = _load_rules(rules, enabled_map_by_user.get(user_id, {}))
+            results[user_id] = _load_rules(
+                rules, enabled_map_by_user.get(user_id, {}), self.hs.config.experimental
+            )
 
         return results
 
diff --git a/synapse/storage/databases/main/registration.py b/synapse/storage/databases/main/registration.py
index 2996d6bb4d..5167089e03 100644
--- a/synapse/storage/databases/main/registration.py
+++ b/synapse/storage/databases/main/registration.py
@@ -21,7 +21,13 @@ from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Union, cast
 import attr
 
 from synapse.api.constants import UserTypes
-from synapse.api.errors import Codes, StoreError, SynapseError, ThreepidValidationError
+from synapse.api.errors import (
+    Codes,
+    NotFoundError,
+    StoreError,
+    SynapseError,
+    ThreepidValidationError,
+)
 from synapse.config.homeserver import HomeServerConfig
 from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.storage.database import (
@@ -50,6 +56,14 @@ class ExternalIDReuseException(Exception):
     because this external id is given to an other user."""
 
 
+class LoginTokenExpired(Exception):
+    """Exception if the login token sent expired"""
+
+
+class LoginTokenReused(Exception):
+    """Exception if the login token sent was already used"""
+
+
 @attr.s(frozen=True, slots=True, auto_attribs=True)
 class TokenLookupResult:
     """Result of looking up an access token.
@@ -115,6 +129,20 @@ class RefreshTokenLookupResult:
     If None, the session can be refreshed indefinitely."""
 
 
+@attr.s(auto_attribs=True, frozen=True, slots=True)
+class LoginTokenLookupResult:
+    """Result of looking up a login token."""
+
+    user_id: str
+    """The user this token belongs to."""
+
+    auth_provider_id: Optional[str]
+    """The SSO Identity Provider that the user authenticated with, to get this token."""
+
+    auth_provider_session_id: Optional[str]
+    """The session ID advertised by the SSO Identity Provider."""
+
+
 class RegistrationWorkerStore(CacheInvalidationWorkerStore):
     def __init__(
         self,
@@ -1789,6 +1817,130 @@ class RegistrationWorkerStore(CacheInvalidationWorkerStore):
             "replace_refresh_token", _replace_refresh_token_txn
         )
 
+    async def add_login_token_to_user(
+        self,
+        user_id: str,
+        token: str,
+        expiry_ts: int,
+        auth_provider_id: Optional[str],
+        auth_provider_session_id: Optional[str],
+    ) -> None:
+        """Adds a short-term login token for the given user.
+
+        Args:
+            user_id: The user ID.
+            token: The new login token to add.
+            expiry_ts (milliseconds since the epoch): Time after which the login token
+                cannot be used.
+            auth_provider_id: The SSO Identity Provider that the user authenticated with
+                to get this token, if any
+            auth_provider_session_id: The session ID advertised by the SSO Identity
+                Provider, if any.
+        """
+        await self.db_pool.simple_insert(
+            "login_tokens",
+            {
+                "token": token,
+                "user_id": user_id,
+                "expiry_ts": expiry_ts,
+                "auth_provider_id": auth_provider_id,
+                "auth_provider_session_id": auth_provider_session_id,
+            },
+            desc="add_login_token_to_user",
+        )
+
+    def _consume_login_token(
+        self,
+        txn: LoggingTransaction,
+        token: str,
+        ts: int,
+    ) -> LoginTokenLookupResult:
+        values = self.db_pool.simple_select_one_txn(
+            txn,
+            "login_tokens",
+            keyvalues={"token": token},
+            retcols=(
+                "user_id",
+                "expiry_ts",
+                "used_ts",
+                "auth_provider_id",
+                "auth_provider_session_id",
+            ),
+            allow_none=True,
+        )
+
+        if values is None:
+            raise NotFoundError()
+
+        self.db_pool.simple_update_one_txn(
+            txn,
+            "login_tokens",
+            keyvalues={"token": token},
+            updatevalues={"used_ts": ts},
+        )
+        user_id = values["user_id"]
+        expiry_ts = values["expiry_ts"]
+        used_ts = values["used_ts"]
+        auth_provider_id = values["auth_provider_id"]
+        auth_provider_session_id = values["auth_provider_session_id"]
+
+        # Token was already used
+        if used_ts is not None:
+            raise LoginTokenReused()
+
+        # Token expired
+        if ts > int(expiry_ts):
+            raise LoginTokenExpired()
+
+        return LoginTokenLookupResult(
+            user_id=user_id,
+            auth_provider_id=auth_provider_id,
+            auth_provider_session_id=auth_provider_session_id,
+        )
+
+    async def consume_login_token(self, token: str) -> LoginTokenLookupResult:
+        """Lookup a login token and consume it.
+
+        Args:
+            token: The login token.
+
+        Returns:
+            The data stored with that token, including the `user_id`. Returns `None` if
+            the token does not exist or if it expired.
+
+        Raises:
+            NotFound if the login token was not found in database
+            LoginTokenExpired if the login token expired
+            LoginTokenReused if the login token was already used
+        """
+        return await self.db_pool.runInteraction(
+            "consume_login_token",
+            self._consume_login_token,
+            token,
+            self._clock.time_msec(),
+        )
+
+    async def invalidate_login_tokens_by_session_id(
+        self, auth_provider_id: str, auth_provider_session_id: str
+    ) -> None:
+        """Invalidate login tokens with the given IdP session ID.
+
+        Args:
+            auth_provider_id: The SSO Identity Provider that the user authenticated with
+                to get this token
+            auth_provider_session_id: The session ID advertised by the SSO Identity
+                Provider
+        """
+        await self.db_pool.simple_update(
+            table="login_tokens",
+            keyvalues={
+                "auth_provider_id": auth_provider_id,
+                "auth_provider_session_id": auth_provider_session_id,
+            },
+            updatevalues={"used_ts": self._clock.time_msec()},
+            desc="invalidate_login_tokens_by_session_id",
+        )
+
     @cached()
     async def is_guest(self, user_id: str) -> bool:
         res = await self.db_pool.simple_select_one_onecol(
@@ -2019,6 +2171,12 @@ class RegistrationStore(StatsStore, RegistrationBackgroundUpdateStore):
             and hs.config.experimental.msc3866.require_approval_for_new_accounts
         )
 
+        # Create a background job for removing expired login tokens
+        if hs.config.worker.run_background_tasks:
+            self._clock.looping_call(
+                self._delete_expired_login_tokens, THIRTY_MINUTES_IN_MS
+            )
+
     async def add_access_token_to_user(
         self,
         user_id: str,
@@ -2617,6 +2775,23 @@ class RegistrationStore(StatsStore, RegistrationBackgroundUpdateStore):
             approved,
         )
 
+    @wrap_as_background_process("delete_expired_login_tokens")
+    async def _delete_expired_login_tokens(self) -> None:
+        """Remove login tokens with expiry dates that have passed."""
+
+        def _delete_expired_login_tokens_txn(txn: LoggingTransaction, ts: int) -> None:
+            sql = "DELETE FROM login_tokens WHERE expiry_ts <= ?"
+            txn.execute(sql, (ts,))
+
+        # We keep the expired tokens for an extra 5 minutes so we can measure how many
+        # times a token is being used after its expiry
+        now = self._clock.time_msec()
+        await self.db_pool.runInteraction(
+            "delete_expired_login_tokens",
+            _delete_expired_login_tokens_txn,
+            now - (5 * 60 * 1000),
+        )
+
 
 def find_max_generated_user_id_localpart(cur: Cursor) -> int:
     """
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 1de62ee9df..ca431002c8 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -295,6 +295,42 @@ class RelationsWorkerStore(SQLBaseStore):
             "get_recent_references_for_event", _get_recent_references_for_event_txn
         )
 
+    async def get_all_relations_for_event_with_types(
+        self,
+        event_id: str,
+        relation_types: List[str],
+    ) -> List[str]:
+        """Get the event IDs of all events that have a relation to the given event with
+        one of the given relation types.
+
+        Args:
+            event_id: The event for which to look for related events.
+            relation_types: The types of relations to look for.
+
+        Returns:
+            A list of the IDs of the events that relate to the given event with one of
+            the given relation types.
+        """
+
+        def get_all_relation_ids_for_event_with_types_txn(
+            txn: LoggingTransaction,
+        ) -> List[str]:
+            rows = self.db_pool.simple_select_many_txn(
+                txn=txn,
+                table="event_relations",
+                column="relation_type",
+                iterable=relation_types,
+                keyvalues={"relates_to_id": event_id},
+                retcols=["event_id"],
+            )
+
+            return [row["event_id"] for row in rows]
+
+        return await self.db_pool.runInteraction(
+            desc="get_all_relation_ids_for_event_with_types",
+            func=get_all_relation_ids_for_event_with_types_txn,
+        )
+
     async def event_includes_relation(self, event_id: str) -> bool:
         """Check if the given event relates to another event.
 
@@ -484,11 +520,12 @@ class RelationsWorkerStore(SQLBaseStore):
             the event will map to None.
         """
 
-        # We only allow edits for events that have the same sender and event type.
-        # We can't assert these things during regular event auth so we have to do
-        # the checks post hoc.
+        # We only allow edits for `m.room.message` events that have the same sender
+        # and event type. We can't assert these things during regular event auth so
+        # we have to do the checks post hoc.
 
-        # Fetches latest edit that has the same type and sender as the original.
+        # Fetches latest edit that has the same type and sender as the
+        # original, and is an `m.room.message`.
         if isinstance(self.database_engine, PostgresEngine):
             # The `DISTINCT ON` clause will pick the *first* row it encounters,
             # so ordering by origin server ts + event ID desc will ensure we get
@@ -504,6 +541,7 @@ class RelationsWorkerStore(SQLBaseStore):
                 WHERE
                     %s
                     AND relation_type = ?
+                    AND edit.type = 'm.room.message'
                 ORDER by original.event_id DESC, edit.origin_server_ts DESC, edit.event_id DESC
             """
         else:
@@ -522,6 +560,7 @@ class RelationsWorkerStore(SQLBaseStore):
                 WHERE
                     %s
                     AND relation_type = ?
+                    AND edit.type = 'm.room.message'
                 ORDER by edit.origin_server_ts, edit.event_id
             """
 
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 32e1e983a5..e56a13f21e 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -152,6 +152,9 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         the forward extremities of those rooms will exclude most members. We may also
         calculate room state incorrectly for such rooms and believe that a member is or
         is not in the room when the opposite is true.
+
+        Note: If you only care about users in the room local to the homeserver, use
+        `get_local_users_in_room(...)` instead which will be more performant.
         """
         return await self.db_pool.simple_select_onecol(
             table="current_state_events",
@@ -742,7 +745,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             # user and the set of other users, and then checking if there is any
             # overlap.
             sql = f"""
-                SELECT b.state_key
+                SELECT DISTINCT b.state_key
                 FROM (
                     SELECT room_id FROM current_state_events
                     WHERE type = 'm.room.member' AND membership = 'join' AND state_key = ?
@@ -751,7 +754,6 @@ class RoomMemberWorkerStore(EventsWorkerStore):
                     SELECT room_id, state_key FROM current_state_events
                     WHERE type = 'm.room.member' AND membership = 'join' AND {clause}
                 ) AS b using (room_id)
-                LIMIT 1
             """
 
             txn.execute(sql, (user_id, *args))
diff --git a/synapse/storage/databases/main/search.py b/synapse/storage/databases/main/search.py
index 1b79acf955..e9588d1755 100644
--- a/synapse/storage/databases/main/search.py
+++ b/synapse/storage/databases/main/search.py
@@ -11,10 +11,22 @@
 # 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 enum
 import logging
 import re
-from typing import TYPE_CHECKING, Any, Collection, Iterable, List, Optional, Set, Tuple
+from collections import deque
+from dataclasses import dataclass
+from typing import (
+    TYPE_CHECKING,
+    Any,
+    Collection,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Tuple,
+    Union,
+)
 
 import attr
 
@@ -27,7 +39,7 @@ from synapse.storage.database import (
     LoggingTransaction,
 )
 from synapse.storage.databases.main.events_worker import EventRedactBehaviour
-from synapse.storage.engines import BaseDatabaseEngine, PostgresEngine, Sqlite3Engine
+from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 from synapse.types import JsonDict
 
 if TYPE_CHECKING:
@@ -68,11 +80,11 @@ class SearchWorkerStore(SQLBaseStore):
         if not self.hs.config.server.enable_search:
             return
         if isinstance(self.database_engine, PostgresEngine):
-            sql = (
-                "INSERT INTO event_search"
-                " (event_id, room_id, key, vector, stream_ordering, origin_server_ts)"
-                " VALUES (?,?,?,to_tsvector('english', ?),?,?)"
-            )
+            sql = """
+            INSERT INTO event_search
+            (event_id, room_id, key, vector, stream_ordering, origin_server_ts)
+            VALUES (?,?,?,to_tsvector('english', ?),?,?)
+            """
 
             args1 = (
                 (
@@ -89,20 +101,20 @@ class SearchWorkerStore(SQLBaseStore):
             txn.execute_batch(sql, args1)
 
         elif isinstance(self.database_engine, Sqlite3Engine):
-            sql = (
-                "INSERT INTO event_search (event_id, room_id, key, value)"
-                " VALUES (?,?,?,?)"
-            )
-            args2 = (
-                (
-                    entry.event_id,
-                    entry.room_id,
-                    entry.key,
-                    _clean_value_for_search(entry.value),
-                )
-                for entry in entries
+            self.db_pool.simple_insert_many_txn(
+                txn,
+                table="event_search",
+                keys=("event_id", "room_id", "key", "value"),
+                values=(
+                    (
+                        entry.event_id,
+                        entry.room_id,
+                        entry.key,
+                        _clean_value_for_search(entry.value),
+                    )
+                    for entry in entries
+                ),
             )
-            txn.execute_batch(sql, args2)
 
         else:
             # This should be unreachable.
@@ -150,15 +162,17 @@ class SearchBackgroundUpdateStore(SearchWorkerStore):
         TYPES = ["m.room.name", "m.room.message", "m.room.topic"]
 
         def reindex_search_txn(txn: LoggingTransaction) -> int:
-            sql = (
-                "SELECT stream_ordering, event_id, room_id, type, json, "
-                " origin_server_ts FROM events"
-                " JOIN event_json USING (room_id, event_id)"
-                " WHERE ? <= stream_ordering AND stream_ordering < ?"
-                " AND (%s)"
-                " ORDER BY stream_ordering DESC"
-                " LIMIT ?"
-            ) % (" OR ".join("type = '%s'" % (t,) for t in TYPES),)
+            sql = """
+            SELECT stream_ordering, event_id, room_id, type, json, origin_server_ts
+            FROM events
+            JOIN event_json USING (room_id, event_id)
+            WHERE ? <= stream_ordering AND stream_ordering < ?
+            AND (%s)
+            ORDER BY stream_ordering DESC
+            LIMIT ?
+            """ % (
+                " OR ".join("type = '%s'" % (t,) for t in TYPES),
+            )
 
             txn.execute(sql, (target_min_stream_id, max_stream_id, batch_size))
 
@@ -272,8 +286,10 @@ class SearchBackgroundUpdateStore(SearchWorkerStore):
 
                 try:
                     c.execute(
-                        "CREATE INDEX CONCURRENTLY event_search_fts_idx"
-                        " ON event_search USING GIN (vector)"
+                        """
+                        CREATE INDEX CONCURRENTLY event_search_fts_idx
+                        ON event_search USING GIN (vector)
+                        """
                     )
                 except psycopg2.ProgrammingError as e:
                     logger.warning(
@@ -311,12 +327,16 @@ class SearchBackgroundUpdateStore(SearchWorkerStore):
                 # We create with NULLS FIRST so that when we search *backwards*
                 # we get the ones with non null origin_server_ts *first*
                 c.execute(
-                    "CREATE INDEX CONCURRENTLY event_search_room_order ON event_search("
-                    "room_id, origin_server_ts NULLS FIRST, stream_ordering NULLS FIRST)"
+                    """
+                    CREATE INDEX CONCURRENTLY event_search_room_order
+                    ON event_search(room_id, origin_server_ts NULLS FIRST, stream_ordering NULLS FIRST)
+                    """
                 )
                 c.execute(
-                    "CREATE INDEX CONCURRENTLY event_search_order ON event_search("
-                    "origin_server_ts NULLS FIRST, stream_ordering NULLS FIRST)"
+                    """
+                    CREATE INDEX CONCURRENTLY event_search_order
+                    ON event_search(origin_server_ts NULLS FIRST, stream_ordering NULLS FIRST)
+                    """
                 )
                 conn.set_session(autocommit=False)
 
@@ -333,14 +353,14 @@ class SearchBackgroundUpdateStore(SearchWorkerStore):
             )
 
         def reindex_search_txn(txn: LoggingTransaction) -> Tuple[int, bool]:
-            sql = (
-                "UPDATE event_search AS es SET stream_ordering = e.stream_ordering,"
-                " origin_server_ts = e.origin_server_ts"
-                " FROM events AS e"
-                " WHERE e.event_id = es.event_id"
-                " AND ? <= e.stream_ordering AND e.stream_ordering < ?"
-                " RETURNING es.stream_ordering"
-            )
+            sql = """
+            UPDATE event_search AS es
+            SET stream_ordering = e.stream_ordering, origin_server_ts = e.origin_server_ts
+            FROM events AS e
+            WHERE e.event_id = es.event_id
+            AND ? <= e.stream_ordering AND e.stream_ordering < ?
+            RETURNING es.stream_ordering
+            """
 
             min_stream_id = max_stream_id - batch_size
             txn.execute(sql, (min_stream_id, max_stream_id))
@@ -421,8 +441,6 @@ class SearchStore(SearchBackgroundUpdateStore):
         """
         clauses = []
 
-        search_query = _parse_query(self.database_engine, search_term)
-
         args: List[Any] = []
 
         # Make sure we don't explode because the person is in too many rooms.
@@ -444,32 +462,36 @@ class SearchStore(SearchBackgroundUpdateStore):
         count_clauses = clauses
 
         if isinstance(self.database_engine, PostgresEngine):
-            sql = (
-                "SELECT ts_rank_cd(vector, to_tsquery('english', ?)) AS rank,"
-                " room_id, event_id"
-                " FROM event_search"
-                " WHERE vector @@ to_tsquery('english', ?)"
-            )
+            search_query = search_term
+            tsquery_func = self.database_engine.tsquery_func
+            sql = f"""
+            SELECT ts_rank_cd(vector, {tsquery_func}('english', ?)) AS rank,
+            room_id, event_id
+            FROM event_search
+            WHERE vector @@  {tsquery_func}('english', ?)
+            """
             args = [search_query, search_query] + args
 
-            count_sql = (
-                "SELECT room_id, count(*) as count FROM event_search"
-                " WHERE vector @@ to_tsquery('english', ?)"
-            )
+            count_sql = f"""
+            SELECT room_id, count(*) as count FROM event_search
+            WHERE vector @@ {tsquery_func}('english', ?)
+            """
             count_args = [search_query] + count_args
         elif isinstance(self.database_engine, Sqlite3Engine):
-            sql = (
-                "SELECT rank(matchinfo(event_search)) as rank, room_id, event_id"
-                " FROM event_search"
-                " WHERE value MATCH ?"
-            )
+            search_query = _parse_query_for_sqlite(search_term)
+
+            sql = """
+            SELECT rank(matchinfo(event_search)) as rank, room_id, event_id
+            FROM event_search
+            WHERE value MATCH ?
+            """
             args = [search_query] + args
 
-            count_sql = (
-                "SELECT room_id, count(*) as count FROM event_search"
-                " WHERE value MATCH ?"
-            )
-            count_args = [search_term] + count_args
+            count_sql = """
+            SELECT room_id, count(*) as count FROM event_search
+            WHERE value MATCH ?
+            """
+            count_args = [search_query] + count_args
         else:
             # This should be unreachable.
             raise Exception("Unrecognized database engine")
@@ -501,7 +523,9 @@ class SearchStore(SearchBackgroundUpdateStore):
 
         highlights = None
         if isinstance(self.database_engine, PostgresEngine):
-            highlights = await self._find_highlights_in_postgres(search_query, events)
+            highlights = await self._find_highlights_in_postgres(
+                search_query, events, tsquery_func
+            )
 
         count_sql += " GROUP BY room_id"
 
@@ -510,7 +534,6 @@ class SearchStore(SearchBackgroundUpdateStore):
         )
 
         count = sum(row["count"] for row in count_results if row["room_id"] in room_ids)
-
         return {
             "results": [
                 {"event": event_map[r["event_id"]], "rank": r["rank"]}
@@ -542,9 +565,6 @@ class SearchStore(SearchBackgroundUpdateStore):
             Each match as a dictionary.
         """
         clauses = []
-
-        search_query = _parse_query(self.database_engine, search_term)
-
         args: List[Any] = []
 
         # Make sure we don't explode because the person is in too many rooms.
@@ -576,26 +596,30 @@ class SearchStore(SearchBackgroundUpdateStore):
                 raise SynapseError(400, "Invalid pagination token")
 
             clauses.append(
-                "(origin_server_ts < ?"
-                " OR (origin_server_ts = ? AND stream_ordering < ?))"
+                """
+                (origin_server_ts < ? OR (origin_server_ts = ? AND stream_ordering < ?))
+                """
             )
             args.extend([origin_server_ts, origin_server_ts, stream])
 
         if isinstance(self.database_engine, PostgresEngine):
-            sql = (
-                "SELECT ts_rank_cd(vector, to_tsquery('english', ?)) as rank,"
-                " origin_server_ts, stream_ordering, room_id, event_id"
-                " FROM event_search"
-                " WHERE vector @@ to_tsquery('english', ?) AND "
-            )
+            search_query = search_term
+            tsquery_func = self.database_engine.tsquery_func
+            sql = f"""
+            SELECT ts_rank_cd(vector, {tsquery_func}('english', ?)) as rank,
+            origin_server_ts, stream_ordering, room_id, event_id
+            FROM event_search
+            WHERE vector @@ {tsquery_func}('english', ?) AND
+            """
             args = [search_query, search_query] + args
 
-            count_sql = (
-                "SELECT room_id, count(*) as count FROM event_search"
-                " WHERE vector @@ to_tsquery('english', ?) AND "
-            )
+            count_sql = f"""
+            SELECT room_id, count(*) as count FROM event_search
+            WHERE vector @@ {tsquery_func}('english', ?) AND
+            """
             count_args = [search_query] + count_args
         elif isinstance(self.database_engine, Sqlite3Engine):
+
             # We use CROSS JOIN here to ensure we use the right indexes.
             # https://sqlite.org/optoverview.html#crossjoin
             #
@@ -604,23 +628,25 @@ class SearchStore(SearchBackgroundUpdateStore):
             # in the events table to get the topological ordering. We need
             # to use the indexes in this order because sqlite refuses to
             # MATCH unless it uses the full text search index
-            sql = (
-                "SELECT rank(matchinfo) as rank, room_id, event_id,"
-                " origin_server_ts, stream_ordering"
-                " FROM (SELECT key, event_id, matchinfo(event_search) as matchinfo"
-                " FROM event_search"
-                " WHERE value MATCH ?"
-                " )"
-                " CROSS JOIN events USING (event_id)"
-                " WHERE "
+            sql = """
+            SELECT
+                rank(matchinfo) as rank, room_id, event_id, origin_server_ts, stream_ordering
+            FROM (
+                SELECT key, event_id, matchinfo(event_search) as matchinfo
+                FROM event_search
+                WHERE value MATCH ?
             )
+            CROSS JOIN events USING (event_id)
+            WHERE
+            """
+            search_query = _parse_query_for_sqlite(search_term)
             args = [search_query] + args
 
-            count_sql = (
-                "SELECT room_id, count(*) as count FROM event_search"
-                " WHERE value MATCH ? AND "
-            )
-            count_args = [search_term] + count_args
+            count_sql = """
+            SELECT room_id, count(*) as count FROM event_search
+            WHERE value MATCH ? AND
+            """
+            count_args = [search_query] + count_args
         else:
             # This should be unreachable.
             raise Exception("Unrecognized database engine")
@@ -631,10 +657,10 @@ class SearchStore(SearchBackgroundUpdateStore):
         # We add an arbitrary limit here to ensure we don't try to pull the
         # entire table from the database.
         if isinstance(self.database_engine, PostgresEngine):
-            sql += (
-                " ORDER BY origin_server_ts DESC NULLS LAST,"
-                " stream_ordering DESC NULLS LAST LIMIT ?"
-            )
+            sql += """
+            ORDER BY origin_server_ts DESC NULLS LAST, stream_ordering DESC NULLS LAST
+            LIMIT ?
+            """
         elif isinstance(self.database_engine, Sqlite3Engine):
             sql += " ORDER BY origin_server_ts DESC, stream_ordering DESC LIMIT ?"
         else:
@@ -660,7 +686,9 @@ class SearchStore(SearchBackgroundUpdateStore):
 
         highlights = None
         if isinstance(self.database_engine, PostgresEngine):
-            highlights = await self._find_highlights_in_postgres(search_query, events)
+            highlights = await self._find_highlights_in_postgres(
+                search_query, events, tsquery_func
+            )
 
         count_sql += " GROUP BY room_id"
 
@@ -686,7 +714,7 @@ class SearchStore(SearchBackgroundUpdateStore):
         }
 
     async def _find_highlights_in_postgres(
-        self, search_query: str, events: List[EventBase]
+        self, search_query: str, events: List[EventBase], tsquery_func: str
     ) -> Set[str]:
         """Given a list of events and a search term, return a list of words
         that match from the content of the event.
@@ -697,6 +725,7 @@ class SearchStore(SearchBackgroundUpdateStore):
         Args:
             search_query
             events: A list of events
+            tsquery_func: The tsquery_* function to use when making queries
 
         Returns:
             A set of strings.
@@ -729,7 +758,7 @@ class SearchStore(SearchBackgroundUpdateStore):
                 while stop_sel in value:
                     stop_sel += ">"
 
-                query = "SELECT ts_headline(?, to_tsquery('english', ?), %s)" % (
+                query = f"SELECT ts_headline(?, {tsquery_func}('english', ?), %s)" % (
                     _to_postgres_options(
                         {
                             "StartSel": start_sel,
@@ -760,20 +789,127 @@ def _to_postgres_options(options_dict: JsonDict) -> str:
     return "'%s'" % (",".join("%s=%s" % (k, v) for k, v in options_dict.items()),)
 
 
-def _parse_query(database_engine: BaseDatabaseEngine, search_term: str) -> str:
-    """Takes a plain unicode string from the user and converts it into a form
-    that can be passed to database.
-    We use this so that we can add prefix matching, which isn't something
-    that is supported by default.
+@dataclass
+class Phrase:
+    phrase: List[str]
+
+
+class SearchToken(enum.Enum):
+    Not = enum.auto()
+    Or = enum.auto()
+    And = enum.auto()
+
+
+Token = Union[str, Phrase, SearchToken]
+TokenList = List[Token]
+
+
+def _is_stop_word(word: str) -> bool:
+    # TODO Pull these out of the dictionary:
+    #  https://github.com/postgres/postgres/blob/master/src/backend/snowball/stopwords/english.stop
+    return word in {"the", "a", "you", "me", "and", "but"}
+
+
+def _tokenize_query(query: str) -> TokenList:
+    """
+    Convert the user-supplied `query` into a TokenList, which can be translated into
+    some DB-specific syntax.
+
+    The following constructs are supported:
+
+    - phrase queries using "double quotes"
+    - case-insensitive `or` and `and` operators
+    - negation of a keyword via unary `-`
+    - unary hyphen to denote NOT e.g. 'include -exclude'
+
+    The following differs from websearch_to_tsquery:
+
+    - Stop words are not removed.
+    - Unclosed phrases are treated differently.
+
     """
+    tokens: TokenList = []
+
+    # Find phrases.
+    in_phrase = False
+    parts = deque(query.split('"'))
+    for i, part in enumerate(parts):
+        # The contents inside double quotes is treated as a phrase.
+        in_phrase = bool(i % 2)
+
+        # Pull out the individual words, discarding any non-word characters.
+        words = deque(re.findall(r"([\w\-]+)", part, re.UNICODE))
+
+        # Phrases have simplified handling of words.
+        if in_phrase:
+            # Skip stop words.
+            phrase = [word for word in words if not _is_stop_word(word)]
+
+            # Consecutive words are implicitly ANDed together.
+            if tokens and tokens[-1] not in (SearchToken.Not, SearchToken.Or):
+                tokens.append(SearchToken.And)
+
+            # Add the phrase.
+            tokens.append(Phrase(phrase))
+            continue
+
+        # Otherwise, not in a phrase.
+        while words:
+            word = words.popleft()
+
+            if word.startswith("-"):
+                tokens.append(SearchToken.Not)
+
+                # If there's more word, put it back to be processed again.
+                word = word[1:]
+                if word:
+                    words.appendleft(word)
+            elif word.lower() == "or":
+                tokens.append(SearchToken.Or)
+            else:
+                # Skip stop words.
+                if _is_stop_word(word):
+                    continue
+
+                # Consecutive words are implicitly ANDed together.
+                if tokens and tokens[-1] not in (SearchToken.Not, SearchToken.Or):
+                    tokens.append(SearchToken.And)
 
-    # Pull out the individual words, discarding any non-word characters.
-    results = re.findall(r"([\w\-]+)", search_term, re.UNICODE)
+                # Add the search term.
+                tokens.append(word)
+
+    return tokens
+
+
+def _tokens_to_sqlite_match_query(tokens: TokenList) -> str:
+    """
+    Convert the list of tokens to a string suitable for passing to sqlite's MATCH.
+    Assume sqlite was compiled with enhanced query syntax.
 
-    if isinstance(database_engine, PostgresEngine):
-        return " & ".join(result + ":*" for result in results)
-    elif isinstance(database_engine, Sqlite3Engine):
-        return " & ".join(result + "*" for result in results)
-    else:
-        # This should be unreachable.
-        raise Exception("Unrecognized database engine")
+    Ref: https://www.sqlite.org/fts3.html#full_text_index_queries
+    """
+    match_query = []
+    for token in tokens:
+        if isinstance(token, str):
+            match_query.append(token)
+        elif isinstance(token, Phrase):
+            match_query.append('"' + " ".join(token.phrase) + '"')
+        elif token == SearchToken.Not:
+            # TODO: SQLite treats NOT as a *binary* operator. Hopefully a search
+            # term has already been added before this.
+            match_query.append(" NOT ")
+        elif token == SearchToken.Or:
+            match_query.append(" OR ")
+        elif token == SearchToken.And:
+            match_query.append(" AND ")
+        else:
+            raise ValueError(f"unknown token {token}")
+
+    return "".join(match_query)
+
+
+def _parse_query_for_sqlite(search_term: str) -> str:
+    """Takes a plain unicode string from the user and converts it into a form
+    that can be passed to sqllite's matchinfo().
+    """
+    return _tokens_to_sqlite_match_query(_tokenize_query(search_term))
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index d8c0f64d9a..9bf74bbf59 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -170,6 +170,22 @@ class PostgresEngine(
         """Do we support the `RETURNING` clause in insert/update/delete?"""
         return True
 
+    @property
+    def tsquery_func(self) -> str:
+        """
+        Selects a tsquery_* func to use.
+
+        Ref: https://www.postgresql.org/docs/current/textsearch-controls.html
+
+        Returns:
+            The function name.
+        """
+        # Postgres 11 added support for websearch_to_tsquery.
+        assert self._version is not None
+        if self._version >= 110000:
+            return "websearch_to_tsquery"
+        return "plainto_tsquery"
+
     def is_deadlock(self, error: Exception) -> bool:
         if isinstance(error, psycopg2.DatabaseError):
             # https://www.postgresql.org/docs/current/static/errcodes-appendix.html
diff --git a/synapse/storage/engines/sqlite.py b/synapse/storage/engines/sqlite.py
index faa574dbfd..14260442b6 100644
--- a/synapse/storage/engines/sqlite.py
+++ b/synapse/storage/engines/sqlite.py
@@ -88,6 +88,10 @@ class Sqlite3Engine(BaseDatabaseEngine[sqlite3.Connection, sqlite3.Cursor]):
 
         db_conn.create_function("rank", 1, _rank)
         db_conn.execute("PRAGMA foreign_keys = ON;")
+
+        # Enable WAL.
+        # see https://www.sqlite.org/wal.html
+        db_conn.execute("PRAGMA journal_mode = WAL;")
         db_conn.commit()
 
     def is_deadlock(self, error: Exception) -> bool:
diff --git a/synapse/storage/schema/main/delta/73/10_update_sqlite_fts4_tokenizer.py b/synapse/storage/schema/main/delta/73/10_update_sqlite_fts4_tokenizer.py
new file mode 100644
index 0000000000..3de0a709eb
--- /dev/null
+++ b/synapse/storage/schema/main/delta/73/10_update_sqlite_fts4_tokenizer.py
@@ -0,0 +1,62 @@
+# Copyright 2022 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 json
+
+from synapse.storage.engines import BaseDatabaseEngine, Sqlite3Engine
+from synapse.storage.types import Cursor
+
+
+def run_create(cur: Cursor, database_engine: BaseDatabaseEngine) -> None:
+    """
+    Upgrade the event_search table to use the porter tokenizer if it isn't already
+
+    Applies only for sqlite.
+    """
+    if not isinstance(database_engine, Sqlite3Engine):
+        return
+
+    # Rebuild the table event_search table with tokenize=porter configured.
+    cur.execute("DROP TABLE event_search")
+    cur.execute(
+        """
+        CREATE VIRTUAL TABLE event_search
+        USING fts4 (tokenize=porter, event_id, room_id, sender, key, value )
+        """
+    )
+
+    # Re-run the background job to re-populate the event_search table.
+    cur.execute("SELECT MIN(stream_ordering) FROM events")
+    row = cur.fetchone()
+    min_stream_id = row[0]
+
+    # If there are not any events, nothing to do.
+    if min_stream_id is None:
+        return
+
+    cur.execute("SELECT MAX(stream_ordering) FROM events")
+    row = cur.fetchone()
+    max_stream_id = row[0]
+
+    progress = {
+        "target_min_stream_id_inclusive": min_stream_id,
+        "max_stream_id_exclusive": max_stream_id + 1,
+    }
+    progress_json = json.dumps(progress)
+
+    sql = """
+    INSERT into background_updates (ordering, update_name, progress_json)
+    VALUES (?, ?, ?)
+    """
+
+    cur.execute(sql, (7310, "event_search", progress_json))
diff --git a/synapse/storage/schema/main/delta/73/10login_tokens.sql b/synapse/storage/schema/main/delta/73/10login_tokens.sql
new file mode 100644
index 0000000000..a39b7bcece
--- /dev/null
+++ b/synapse/storage/schema/main/delta/73/10login_tokens.sql
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2022 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.
+ */
+
+-- Login tokens are short-lived tokens that are used for the m.login.token
+-- login method, mainly during SSO logins
+CREATE TABLE login_tokens (
+    token TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL, 
+    expiry_ts BIGINT NOT NULL,
+    used_ts BIGINT,
+    auth_provider_id TEXT,
+    auth_provider_session_id TEXT
+);
+
+-- We're sometimes querying them by their session ID we got from their IDP
+CREATE INDEX login_tokens_auth_provider_idx 
+    ON login_tokens (auth_provider_id, auth_provider_session_id);
+
+-- We're deleting them by their expiration time
+CREATE INDEX login_tokens_expiry_time_idx 
+    ON login_tokens (expiry_ts);
+
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index b3c748ef44..75428d19ba 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -12,7 +12,6 @@
 # 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 enum
 import functools
 import inspect
 import logging
@@ -146,109 +145,6 @@ class _CacheDescriptorBase:
         )
 
 
-class _LruCachedFunction(Generic[F]):
-    cache: LruCache[CacheKey, Any]
-    __call__: F
-
-
-def lru_cache(
-    *, max_entries: int = 1000, cache_context: bool = False
-) -> Callable[[F], _LruCachedFunction[F]]:
-    """A method decorator that applies a memoizing cache around the function.
-
-    This is more-or-less a drop-in equivalent to functools.lru_cache, although note
-    that the signature is slightly different.
-
-    The main differences with functools.lru_cache are:
-        (a) the size of the cache can be controlled via the cache_factor mechanism
-        (b) the wrapped function can request a "cache_context" which provides a
-            callback mechanism to indicate that the result is no longer valid
-        (c) prometheus metrics are exposed automatically.
-
-    The function should take zero or more arguments, which are used as the key for the
-    cache. Single-argument functions use that argument as the cache key; otherwise the
-    arguments are built into a tuple.
-
-    Cached functions can be "chained" (i.e. a cached function can call other cached
-    functions and get appropriately invalidated when they called caches are
-    invalidated) by adding a special "cache_context" argument to the function
-    and passing that as a kwarg to all caches called. For example:
-
-        @lru_cache(cache_context=True)
-        def foo(self, key, cache_context):
-            r1 = self.bar1(key, on_invalidate=cache_context.invalidate)
-            r2 = self.bar2(key, on_invalidate=cache_context.invalidate)
-            return r1 + r2
-
-    The wrapped function also has a 'cache' property which offers direct access to the
-    underlying LruCache.
-    """
-
-    def func(orig: F) -> _LruCachedFunction[F]:
-        desc = LruCacheDescriptor(
-            orig,
-            max_entries=max_entries,
-            cache_context=cache_context,
-        )
-        return cast(_LruCachedFunction[F], desc)
-
-    return func
-
-
-class LruCacheDescriptor(_CacheDescriptorBase):
-    """Helper for @lru_cache"""
-
-    class _Sentinel(enum.Enum):
-        sentinel = object()
-
-    def __init__(
-        self,
-        orig: Callable[..., Any],
-        max_entries: int = 1000,
-        cache_context: bool = False,
-    ):
-        super().__init__(
-            orig, num_args=None, uncached_args=None, cache_context=cache_context
-        )
-        self.max_entries = max_entries
-
-    def __get__(self, obj: Optional[Any], owner: Optional[Type]) -> Callable[..., Any]:
-        cache: LruCache[CacheKey, Any] = LruCache(
-            cache_name=self.name,
-            max_size=self.max_entries,
-        )
-
-        get_cache_key = self.cache_key_builder
-        sentinel = LruCacheDescriptor._Sentinel.sentinel
-
-        @functools.wraps(self.orig)
-        def _wrapped(*args: Any, **kwargs: Any) -> Any:
-            invalidate_callback = kwargs.pop("on_invalidate", None)
-            callbacks = (invalidate_callback,) if invalidate_callback else ()
-
-            cache_key = get_cache_key(args, kwargs)
-
-            ret = cache.get(cache_key, default=sentinel, callbacks=callbacks)
-            if ret != sentinel:
-                return ret
-
-            # Add our own `cache_context` to argument list if the wrapped function
-            # has asked for one
-            if self.add_cache_context:
-                kwargs["cache_context"] = _CacheContext.get_instance(cache, cache_key)
-
-            ret2 = self.orig(obj, *args, **kwargs)
-            cache.set(cache_key, ret2, callbacks=callbacks)
-
-            return ret2
-
-        wrapped = cast(CachedFunction, _wrapped)
-        wrapped.cache = cache
-        obj.__dict__[self.name] = wrapped
-
-        return wrapped
-
-
 class DeferredCacheDescriptor(_CacheDescriptorBase):
     """A method decorator that applies a memoizing cache around the function.
 
diff --git a/synapse/util/macaroons.py b/synapse/util/macaroons.py
index df77edcce2..5df03d3ddc 100644
--- a/synapse/util/macaroons.py
+++ b/synapse/util/macaroons.py
@@ -24,7 +24,7 @@ from typing_extensions import Literal
 
 from synapse.util import Clock, stringutils
 
-MacaroonType = Literal["access", "delete_pusher", "session", "login"]
+MacaroonType = Literal["access", "delete_pusher", "session"]
 
 
 def get_value_from_macaroon(macaroon: pymacaroons.Macaroon, key: str) -> str:
@@ -111,19 +111,6 @@ class OidcSessionData:
     """The session ID of the ongoing UI Auth ("" if this is a login)"""
 
 
-@attr.s(slots=True, frozen=True, auto_attribs=True)
-class LoginTokenAttributes:
-    """Data we store in a short-term login token"""
-
-    user_id: str
-
-    auth_provider_id: str
-    """The SSO Identity Provider that the user authenticated with, to get this token."""
-
-    auth_provider_session_id: Optional[str]
-    """The session ID advertised by the SSO Identity Provider."""
-
-
 class MacaroonGenerator:
     def __init__(self, clock: Clock, location: str, secret_key: bytes):
         self._clock = clock
@@ -165,35 +152,6 @@ class MacaroonGenerator:
         macaroon.add_first_party_caveat(f"pushkey = {pushkey}")
         return macaroon.serialize()
 
-    def generate_short_term_login_token(
-        self,
-        user_id: str,
-        auth_provider_id: str,
-        auth_provider_session_id: Optional[str] = None,
-        duration_in_ms: int = (2 * 60 * 1000),
-    ) -> str:
-        """Generate a short-term login token used during SSO logins
-
-        Args:
-            user_id: The user for which the token is valid.
-            auth_provider_id: The SSO IdP the user used.
-            auth_provider_session_id: The session ID got during login from the SSO IdP.
-
-        Returns:
-            A signed token valid for using as a ``m.login.token`` token.
-        """
-        now = self._clock.time_msec()
-        expiry = now + duration_in_ms
-        macaroon = self._generate_base_macaroon("login")
-        macaroon.add_first_party_caveat(f"user_id = {user_id}")
-        macaroon.add_first_party_caveat(f"time < {expiry}")
-        macaroon.add_first_party_caveat(f"auth_provider_id = {auth_provider_id}")
-        if auth_provider_session_id is not None:
-            macaroon.add_first_party_caveat(
-                f"auth_provider_session_id = {auth_provider_session_id}"
-            )
-        return macaroon.serialize()
-
     def generate_oidc_session_token(
         self,
         state: str,
@@ -233,49 +191,6 @@ class MacaroonGenerator:
 
         return macaroon.serialize()
 
-    def verify_short_term_login_token(self, token: str) -> LoginTokenAttributes:
-        """Verify a short-term-login macaroon
-
-        Checks that the given token is a valid, unexpired short-term-login token
-        minted by this server.
-
-        Args:
-            token: The login token to verify.
-
-        Returns:
-            A set of attributes carried by this token, including the
-            ``user_id`` and informations about the SSO IDP used during that
-            login.
-
-        Raises:
-            MacaroonVerificationFailedException if the verification failed
-        """
-        macaroon = pymacaroons.Macaroon.deserialize(token)
-
-        v = self._base_verifier("login")
-        v.satisfy_general(lambda c: c.startswith("user_id = "))
-        v.satisfy_general(lambda c: c.startswith("auth_provider_id = "))
-        v.satisfy_general(lambda c: c.startswith("auth_provider_session_id = "))
-        satisfy_expiry(v, self._clock.time_msec)
-        v.verify(macaroon, self._secret_key)
-
-        user_id = get_value_from_macaroon(macaroon, "user_id")
-        auth_provider_id = get_value_from_macaroon(macaroon, "auth_provider_id")
-
-        auth_provider_session_id: Optional[str] = None
-        try:
-            auth_provider_session_id = get_value_from_macaroon(
-                macaroon, "auth_provider_session_id"
-            )
-        except MacaroonVerificationFailedException:
-            pass
-
-        return LoginTokenAttributes(
-            user_id=user_id,
-            auth_provider_id=auth_provider_id,
-            auth_provider_session_id=auth_provider_session_id,
-        )
-
     def verify_guest_token(self, token: str) -> str:
         """Verify a guest access token macaroon
 
diff --git a/synapse/util/retryutils.py b/synapse/util/retryutils.py
index d0a69ff843..dcc037b982 100644
--- a/synapse/util/retryutils.py
+++ b/synapse/util/retryutils.py
@@ -51,7 +51,7 @@ class NotRetryingDestination(Exception):
             destination: the domain in question
         """
 
-        msg = "Not retrying server %s." % (destination,)
+        msg = f"Not retrying server {destination} because we tried it recently retry_last_ts={retry_last_ts} and we won't check for another retry_interval={retry_interval}ms."
         super().__init__(msg)
 
         self.retry_last_ts = retry_last_ts