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-rw-r--r--synapse/rest/__init__.py2
-rw-r--r--synapse/rest/admin/__init__.py7
-rw-r--r--synapse/rest/admin/rooms.py79
-rw-r--r--synapse/rest/client/v1/login.py178
-rw-r--r--synapse/rest/client/v1/room.py33
-rw-r--r--synapse/rest/client/v2_alpha/account.py40
-rw-r--r--synapse/rest/client/v2_alpha/auth.py88
-rw-r--r--synapse/rest/client/v2_alpha/devices.py12
-rw-r--r--synapse/rest/client/v2_alpha/keys.py6
-rw-r--r--synapse/rest/client/v2_alpha/password_policy.py58
-rw-r--r--synapse/rest/client/v2_alpha/register.py8
-rw-r--r--synapse/rest/client/v2_alpha/room_keys.py2
-rw-r--r--synapse/rest/media/v1/download_resource.py3
-rw-r--r--synapse/rest/media/v1/media_repository.py110
-rw-r--r--synapse/rest/media/v1/preview_url_resource.py54
-rw-r--r--synapse/rest/media/v1/thumbnail_resource.py54
16 files changed, 406 insertions, 328 deletions
diff --git a/synapse/rest/__init__.py b/synapse/rest/__init__.py
index 4a1fc2ec2b..46e458e95b 100644
--- a/synapse/rest/__init__.py
+++ b/synapse/rest/__init__.py
@@ -41,6 +41,7 @@ from synapse.rest.client.v2_alpha import (
     keys,
     notifications,
     openid,
+    password_policy,
     read_marker,
     receipts,
     register,
@@ -118,6 +119,7 @@ class ClientRestResource(JsonResource):
         capabilities.register_servlets(hs, client_resource)
         account_validity.register_servlets(hs, client_resource)
         relations.register_servlets(hs, client_resource)
+        password_policy.register_servlets(hs, client_resource)
 
         # moving to /_synapse/admin
         synapse.rest.admin.register_servlets_for_client_rest_resource(
diff --git a/synapse/rest/admin/__init__.py b/synapse/rest/admin/__init__.py
index 42cc2b062a..ed70d448a1 100644
--- a/synapse/rest/admin/__init__.py
+++ b/synapse/rest/admin/__init__.py
@@ -29,7 +29,11 @@ from synapse.rest.admin._base import (
 from synapse.rest.admin.groups import DeleteGroupAdminRestServlet
 from synapse.rest.admin.media import ListMediaInRoom, register_servlets_for_media_repo
 from synapse.rest.admin.purge_room_servlet import PurgeRoomServlet
-from synapse.rest.admin.rooms import ListRoomRestServlet, ShutdownRoomRestServlet
+from synapse.rest.admin.rooms import (
+    JoinRoomAliasServlet,
+    ListRoomRestServlet,
+    ShutdownRoomRestServlet,
+)
 from synapse.rest.admin.server_notice_servlet import SendServerNoticeServlet
 from synapse.rest.admin.users import (
     AccountValidityRenewServlet,
@@ -189,6 +193,7 @@ def register_servlets(hs, http_server):
     """
     register_servlets_for_client_rest_resource(hs, http_server)
     ListRoomRestServlet(hs).register(http_server)
+    JoinRoomAliasServlet(hs).register(http_server)
     PurgeRoomServlet(hs).register(http_server)
     SendServerNoticeServlet(hs).register(http_server)
     VersionServlet(hs).register(http_server)
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index f9b8c0a4f0..659b8a10ee 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -13,9 +13,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import logging
+from typing import List, Optional
 
-from synapse.api.constants import Membership
-from synapse.api.errors import Codes, SynapseError
+from synapse.api.constants import EventTypes, JoinRules, Membership
+from synapse.api.errors import Codes, NotFoundError, SynapseError
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
@@ -29,7 +30,7 @@ from synapse.rest.admin._base import (
     historical_admin_path_patterns,
 )
 from synapse.storage.data_stores.main.room import RoomSortOrder
-from synapse.types import create_requester
+from synapse.types import RoomAlias, RoomID, UserID, create_requester
 from synapse.util.async_helpers import maybe_awaitable
 
 logger = logging.getLogger(__name__)
@@ -237,3 +238,75 @@ class ListRoomRestServlet(RestServlet):
                 response["prev_batch"] = 0
 
         return 200, response
+
+
+class JoinRoomAliasServlet(RestServlet):
+
+    PATTERNS = admin_patterns("/join/(?P<room_identifier>[^/]*)")
+
+    def __init__(self, hs):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.room_member_handler = hs.get_room_member_handler()
+        self.admin_handler = hs.get_handlers().admin_handler
+        self.state_handler = hs.get_state_handler()
+
+    async def on_POST(self, request, room_identifier):
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        content = parse_json_object_from_request(request)
+
+        assert_params_in_dict(content, ["user_id"])
+        target_user = UserID.from_string(content["user_id"])
+
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "This endpoint can only be used with local users")
+
+        if not await self.admin_handler.get_user(target_user):
+            raise NotFoundError("User not found")
+
+        if RoomID.is_valid(room_identifier):
+            room_id = room_identifier
+            try:
+                remote_room_hosts = [
+                    x.decode("ascii") for x in request.args[b"server_name"]
+                ]  # type: Optional[List[str]]
+            except Exception:
+                remote_room_hosts = None
+        elif RoomAlias.is_valid(room_identifier):
+            handler = self.room_member_handler
+            room_alias = RoomAlias.from_string(room_identifier)
+            room_id, remote_room_hosts = await handler.lookup_room_alias(room_alias)
+            room_id = room_id.to_string()
+        else:
+            raise SynapseError(
+                400, "%s was not legal room ID or room alias" % (room_identifier,)
+            )
+
+        fake_requester = create_requester(target_user)
+
+        # send invite if room has "JoinRules.INVITE"
+        room_state = await self.state_handler.get_current_state(room_id)
+        join_rules_event = room_state.get((EventTypes.JoinRules, ""))
+        if join_rules_event:
+            if not (join_rules_event.content.get("join_rule") == JoinRules.PUBLIC):
+                await self.room_member_handler.update_membership(
+                    requester=requester,
+                    target=fake_requester.user,
+                    room_id=room_id,
+                    action="invite",
+                    remote_room_hosts=remote_room_hosts,
+                    ratelimit=False,
+                )
+
+        await self.room_member_handler.update_membership(
+            requester=fake_requester,
+            target=fake_requester.user,
+            room_id=room_id,
+            action="join",
+            remote_room_hosts=remote_room_hosts,
+            ratelimit=False,
+        )
+
+        return 200, {"room_id": room_id}
diff --git a/synapse/rest/client/v1/login.py b/synapse/rest/client/v1/login.py
index d0d4999795..4de2f97d06 100644
--- a/synapse/rest/client/v1/login.py
+++ b/synapse/rest/client/v1/login.py
@@ -14,11 +14,6 @@
 # limitations under the License.
 
 import logging
-import xml.etree.ElementTree as ET
-
-from six.moves import urllib
-
-from twisted.web.client import PartialDownloadError
 
 from synapse.api.errors import Codes, LoginError, SynapseError
 from synapse.api.ratelimiting import Ratelimiter
@@ -28,10 +23,10 @@ from synapse.http.servlet import (
     parse_json_object_from_request,
     parse_string,
 )
-from synapse.push.mailer import load_jinja2_templates
+from synapse.http.site import SynapseRequest
 from synapse.rest.client.v2_alpha._base import client_patterns
 from synapse.rest.well_known import WellKnownBuilder
-from synapse.types import UserID, map_username_to_mxid_localpart
+from synapse.types import UserID
 from synapse.util.msisdn import phone_number_to_msisdn
 
 logger = logging.getLogger(__name__)
@@ -402,7 +397,7 @@ class BaseSSORedirectServlet(RestServlet):
 
     PATTERNS = client_patterns("/login/(cas|sso)/redirect", v1=True)
 
-    def on_GET(self, request):
+    def on_GET(self, request: SynapseRequest):
         args = request.args
         if b"redirectUrl" not in args:
             return 400, "Redirect URL not specified for SSO auth"
@@ -411,15 +406,15 @@ class BaseSSORedirectServlet(RestServlet):
         request.redirect(sso_url)
         finish_request(request)
 
-    def get_sso_url(self, client_redirect_url):
+    def get_sso_url(self, client_redirect_url: bytes) -> bytes:
         """Get the URL to redirect to, to perform SSO auth
 
         Args:
-            client_redirect_url (bytes): the URL that we should redirect the
+            client_redirect_url: the URL that we should redirect the
                 client to when everything is done
 
         Returns:
-            bytes: URL to redirect to
+            URL to redirect to
         """
         # to be implemented by subclasses
         raise NotImplementedError()
@@ -427,19 +422,12 @@ class BaseSSORedirectServlet(RestServlet):
 
 class CasRedirectServlet(BaseSSORedirectServlet):
     def __init__(self, hs):
-        super(CasRedirectServlet, self).__init__()
-        self.cas_server_url = hs.config.cas_server_url.encode("ascii")
-        self.cas_service_url = hs.config.cas_service_url.encode("ascii")
+        self._cas_handler = hs.get_cas_handler()
 
-    def get_sso_url(self, client_redirect_url):
-        client_redirect_url_param = urllib.parse.urlencode(
-            {b"redirectUrl": client_redirect_url}
+    def get_sso_url(self, client_redirect_url: bytes) -> bytes:
+        return self._cas_handler.get_redirect_url(
+            {"redirectUrl": client_redirect_url}
         ).encode("ascii")
-        hs_redirect_url = self.cas_service_url + b"/_matrix/client/r0/login/cas/ticket"
-        service_param = urllib.parse.urlencode(
-            {b"service": b"%s?%s" % (hs_redirect_url, client_redirect_url_param)}
-        ).encode("ascii")
-        return b"%s/login?%s" % (self.cas_server_url, service_param)
 
 
 class CasTicketServlet(RestServlet):
@@ -447,81 +435,25 @@ class CasTicketServlet(RestServlet):
 
     def __init__(self, hs):
         super(CasTicketServlet, self).__init__()
-        self.cas_server_url = hs.config.cas_server_url
-        self.cas_service_url = hs.config.cas_service_url
-        self.cas_displayname_attribute = hs.config.cas_displayname_attribute
-        self.cas_required_attributes = hs.config.cas_required_attributes
-        self._sso_auth_handler = SSOAuthHandler(hs)
-        self._http_client = hs.get_proxied_http_client()
-
-    async def on_GET(self, request):
-        client_redirect_url = parse_string(request, "redirectUrl", required=True)
-        uri = self.cas_server_url + "/proxyValidate"
-        args = {
-            "ticket": parse_string(request, "ticket", required=True),
-            "service": self.cas_service_url,
-        }
-        try:
-            body = await self._http_client.get_raw(uri, args)
-        except PartialDownloadError as pde:
-            # Twisted raises this error if the connection is closed,
-            # even if that's being used old-http style to signal end-of-data
-            body = pde.response
-        result = await self.handle_cas_response(request, body, client_redirect_url)
-        return result
+        self._cas_handler = hs.get_cas_handler()
 
-    def handle_cas_response(self, request, cas_response_body, client_redirect_url):
-        user, attributes = self.parse_cas_response(cas_response_body)
-        displayname = attributes.pop(self.cas_displayname_attribute, None)
+    async def on_GET(self, request: SynapseRequest) -> None:
+        client_redirect_url = parse_string(request, "redirectUrl")
+        ticket = parse_string(request, "ticket", required=True)
 
-        for required_attribute, required_value in self.cas_required_attributes.items():
-            # If required attribute was not in CAS Response - Forbidden
-            if required_attribute not in attributes:
-                raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
+        # Maybe get a session ID (if this ticket is from user interactive
+        # authentication).
+        session = parse_string(request, "session")
 
-            # Also need to check value
-            if required_value is not None:
-                actual_value = attributes[required_attribute]
-                # If required attribute value does not match expected - Forbidden
-                if required_value != actual_value:
-                    raise LoginError(401, "Unauthorized", errcode=Codes.UNAUTHORIZED)
+        # Either client_redirect_url or session must be provided.
+        if not client_redirect_url and not session:
+            message = "Missing string query parameter redirectUrl or session"
+            raise SynapseError(400, message, errcode=Codes.MISSING_PARAM)
 
-        return self._sso_auth_handler.on_successful_auth(
-            user, request, client_redirect_url, displayname
+        await self._cas_handler.handle_ticket(
+            request, ticket, client_redirect_url, session
         )
 
-    def parse_cas_response(self, cas_response_body):
-        user = None
-        attributes = {}
-        try:
-            root = ET.fromstring(cas_response_body)
-            if not root.tag.endswith("serviceResponse"):
-                raise Exception("root of CAS response is not serviceResponse")
-            success = root[0].tag.endswith("authenticationSuccess")
-            for child in root[0]:
-                if child.tag.endswith("user"):
-                    user = child.text
-                if child.tag.endswith("attributes"):
-                    for attribute in child:
-                        # ElementTree library expands the namespace in
-                        # attribute tags to the full URL of the namespace.
-                        # We don't care about namespace here and it will always
-                        # be encased in curly braces, so we remove them.
-                        tag = attribute.tag
-                        if "}" in tag:
-                            tag = tag.split("}")[1]
-                        attributes[tag] = attribute.text
-            if user is None:
-                raise Exception("CAS response does not contain user")
-        except Exception:
-            logger.exception("Error parsing CAS response")
-            raise LoginError(401, "Invalid CAS response", errcode=Codes.UNAUTHORIZED)
-        if not success:
-            raise LoginError(
-                401, "Unsuccessful CAS response", errcode=Codes.UNAUTHORIZED
-            )
-        return user, attributes
-
 
 class SAMLRedirectServlet(BaseSSORedirectServlet):
     PATTERNS = client_patterns("/login/sso/redirect", v1=True)
@@ -529,72 +461,10 @@ class SAMLRedirectServlet(BaseSSORedirectServlet):
     def __init__(self, hs):
         self._saml_handler = hs.get_saml_handler()
 
-    def get_sso_url(self, client_redirect_url):
+    def get_sso_url(self, client_redirect_url: bytes) -> bytes:
         return self._saml_handler.handle_redirect_request(client_redirect_url)
 
 
-class SSOAuthHandler(object):
-    """
-    Utility class for Resources and Servlets which handle the response from a SSO
-    service
-
-    Args:
-        hs (synapse.server.HomeServer)
-    """
-
-    def __init__(self, hs):
-        self._hostname = hs.hostname
-        self._auth_handler = hs.get_auth_handler()
-        self._registration_handler = hs.get_registration_handler()
-        self._macaroon_gen = hs.get_macaroon_generator()
-
-        # Load the redirect page HTML template
-        self._template = load_jinja2_templates(
-            hs.config.sso_redirect_confirm_template_dir, ["sso_redirect_confirm.html"],
-        )[0]
-
-        self._server_name = hs.config.server_name
-
-        # cast to tuple for use with str.startswith
-        self._whitelisted_sso_clients = tuple(hs.config.sso_client_whitelist)
-
-    async def on_successful_auth(
-        self, username, request, client_redirect_url, user_display_name=None
-    ):
-        """Called once the user has successfully authenticated with the SSO.
-
-        Registers the user if necessary, and then returns a redirect (with
-        a login token) to the client.
-
-        Args:
-            username (unicode|bytes): the remote user id. We'll map this onto
-                something sane for a MXID localpath.
-
-            request (SynapseRequest): the incoming request from the browser. We'll
-                respond to it with a redirect.
-
-            client_redirect_url (unicode): the redirect_url the client gave us when
-                it first started the process.
-
-            user_display_name (unicode|None): if set, and we have to register a new user,
-                we will set their displayname to this.
-
-        Returns:
-            Deferred[none]: Completes once we have handled the request.
-        """
-        localpart = map_username_to_mxid_localpart(username)
-        user_id = UserID(localpart, self._hostname).to_string()
-        registered_user_id = await self._auth_handler.check_user_exists(user_id)
-        if not registered_user_id:
-            registered_user_id = await self._registration_handler.register_user(
-                localpart=localpart, default_display_name=user_display_name
-            )
-
-        self._auth_handler.complete_sso_login(
-            registered_user_id, request, client_redirect_url
-        )
-
-
 def register_servlets(hs, http_server):
     LoginRestServlet(hs).register(http_server)
     if hs.config.cas_enabled:
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index bffd43de5f..6b5830cc3f 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -27,6 +27,7 @@ from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import (
     AuthError,
     Codes,
+    HttpResponseException,
     InvalidClientCredentialsError,
     SynapseError,
 )
@@ -364,10 +365,13 @@ class PublicRoomListRestServlet(TransactionRestServlet):
             limit = None
 
         handler = self.hs.get_room_list_handler()
-        if server:
-            data = await handler.get_remote_public_room_list(
-                server, limit=limit, since_token=since_token
-            )
+        if server and server != self.hs.config.server_name:
+            try:
+                data = await handler.get_remote_public_room_list(
+                    server, limit=limit, since_token=since_token
+                )
+            except HttpResponseException as e:
+                raise e.to_synapse_error()
         else:
             data = await handler.get_local_public_room_list(
                 limit=limit, since_token=since_token
@@ -404,15 +408,18 @@ class PublicRoomListRestServlet(TransactionRestServlet):
             limit = None
 
         handler = self.hs.get_room_list_handler()
-        if server:
-            data = await handler.get_remote_public_room_list(
-                server,
-                limit=limit,
-                since_token=since_token,
-                search_filter=search_filter,
-                include_all_networks=include_all_networks,
-                third_party_instance_id=third_party_instance_id,
-            )
+        if server and server != self.hs.config.server_name:
+            try:
+                data = await handler.get_remote_public_room_list(
+                    server,
+                    limit=limit,
+                    since_token=since_token,
+                    search_filter=search_filter,
+                    include_all_networks=include_all_networks,
+                    third_party_instance_id=third_party_instance_id,
+                )
+            except HttpResponseException as e:
+                raise e.to_synapse_error()
         else:
             data = await handler.get_local_public_room_list(
                 limit=limit,
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index 631cc74cb4..31435b1e1c 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -234,13 +234,21 @@ class PasswordRestServlet(RestServlet):
         if self.auth.has_access_token(request):
             requester = await self.auth.get_user_by_req(request)
             params = await self.auth_handler.validate_user_via_ui_auth(
-                requester, body, self.hs.get_ip_from_request(request)
+                requester,
+                request,
+                body,
+                self.hs.get_ip_from_request(request),
+                "modify your account password",
             )
             user_id = requester.user.to_string()
         else:
             requester = None
             result, params, _ = await self.auth_handler.check_auth(
-                [[LoginType.EMAIL_IDENTITY]], body, self.hs.get_ip_from_request(request)
+                [[LoginType.EMAIL_IDENTITY]],
+                request,
+                body,
+                self.hs.get_ip_from_request(request),
+                "modify your account password",
             )
 
             if LoginType.EMAIL_IDENTITY in result:
@@ -308,7 +316,11 @@ class DeactivateAccountRestServlet(RestServlet):
             return 200, {}
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, body, self.hs.get_ip_from_request(request)
+            requester,
+            request,
+            body,
+            self.hs.get_ip_from_request(request),
+            "deactivate your account",
         )
         result = await self._deactivate_account_handler.deactivate_account(
             requester.user.to_string(), erase, id_server=body.get("id_server")
@@ -602,6 +614,11 @@ class ThreepidRestServlet(RestServlet):
         return 200, {"threepids": threepids}
 
     async def on_POST(self, request):
+        if not self.hs.config.enable_3pid_changes:
+            raise SynapseError(
+                400, "3PID changes are disabled on this server", Codes.FORBIDDEN
+            )
+
         requester = await self.auth.get_user_by_req(request)
         user_id = requester.user.to_string()
         body = parse_json_object_from_request(request)
@@ -646,6 +663,11 @@ class ThreepidAddRestServlet(RestServlet):
 
     @interactive_auth_handler
     async def on_POST(self, request):
+        if not self.hs.config.enable_3pid_changes:
+            raise SynapseError(
+                400, "3PID changes are disabled on this server", Codes.FORBIDDEN
+            )
+
         requester = await self.auth.get_user_by_req(request)
         user_id = requester.user.to_string()
         body = parse_json_object_from_request(request)
@@ -656,7 +678,11 @@ class ThreepidAddRestServlet(RestServlet):
         assert_valid_client_secret(client_secret)
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, body, self.hs.get_ip_from_request(request)
+            requester,
+            request,
+            body,
+            self.hs.get_ip_from_request(request),
+            "add a third-party identifier to your account",
         )
 
         validation_session = await self.identity_handler.validate_threepid_session(
@@ -741,10 +767,16 @@ class ThreepidDeleteRestServlet(RestServlet):
 
     def __init__(self, hs):
         super(ThreepidDeleteRestServlet, self).__init__()
+        self.hs = hs
         self.auth = hs.get_auth()
         self.auth_handler = hs.get_auth_handler()
 
     async def on_POST(self, request):
+        if not self.hs.config.enable_3pid_changes:
+            raise SynapseError(
+                400, "3PID changes are disabled on this server", Codes.FORBIDDEN
+            )
+
         body = parse_json_object_from_request(request)
         assert_params_in_dict(body, ["medium", "address"])
 
diff --git a/synapse/rest/client/v2_alpha/auth.py b/synapse/rest/client/v2_alpha/auth.py
index 50e080673b..11599f5005 100644
--- a/synapse/rest/client/v2_alpha/auth.py
+++ b/synapse/rest/client/v2_alpha/auth.py
@@ -130,6 +130,16 @@ class AuthRestServlet(RestServlet):
         self.auth_handler = hs.get_auth_handler()
         self.registration_handler = hs.get_registration_handler()
 
+        # SSO configuration.
+        self._saml_enabled = hs.config.saml2_enabled
+        if self._saml_enabled:
+            self._saml_handler = hs.get_saml_handler()
+        self._cas_enabled = hs.config.cas_enabled
+        if self._cas_enabled:
+            self._cas_handler = hs.get_cas_handler()
+            self._cas_server_url = hs.config.cas_server_url
+            self._cas_service_url = hs.config.cas_service_url
+
     def on_GET(self, request, stagetype):
         session = parse_string(request, "session")
         if not session:
@@ -142,14 +152,6 @@ class AuthRestServlet(RestServlet):
                 % (CLIENT_API_PREFIX, LoginType.RECAPTCHA),
                 "sitekey": self.hs.config.recaptcha_public_key,
             }
-            html_bytes = html.encode("utf8")
-            request.setResponseCode(200)
-            request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
-            request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
-
-            request.write(html_bytes)
-            finish_request(request)
-            return None
         elif stagetype == LoginType.TERMS:
             html = TERMS_TEMPLATE % {
                 "session": session,
@@ -158,17 +160,41 @@ class AuthRestServlet(RestServlet):
                 "myurl": "%s/r0/auth/%s/fallback/web"
                 % (CLIENT_API_PREFIX, LoginType.TERMS),
             }
-            html_bytes = html.encode("utf8")
-            request.setResponseCode(200)
-            request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
-            request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
-
-            request.write(html_bytes)
-            finish_request(request)
-            return None
+
+        elif stagetype == LoginType.SSO:
+            # Display a confirmation page which prompts the user to
+            # re-authenticate with their SSO provider.
+            if self._cas_enabled:
+                # Generate a request to CAS that redirects back to an endpoint
+                # to verify the successful authentication.
+                sso_redirect_url = self._cas_handler.get_redirect_url(
+                    {"session": session},
+                )
+
+            elif self._saml_enabled:
+                client_redirect_url = ""
+                sso_redirect_url = self._saml_handler.handle_redirect_request(
+                    client_redirect_url, session
+                )
+
+            else:
+                raise SynapseError(400, "Homeserver not configured for SSO.")
+
+            html = self.auth_handler.start_sso_ui_auth(sso_redirect_url, session)
+
         else:
             raise SynapseError(404, "Unknown auth stage type")
 
+        # Render the HTML and return.
+        html_bytes = html.encode("utf8")
+        request.setResponseCode(200)
+        request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+        request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
+
+        request.write(html_bytes)
+        finish_request(request)
+        return None
+
     async def on_POST(self, request, stagetype):
 
         session = parse_string(request, "session")
@@ -196,15 +222,6 @@ class AuthRestServlet(RestServlet):
                     % (CLIENT_API_PREFIX, LoginType.RECAPTCHA),
                     "sitekey": self.hs.config.recaptcha_public_key,
                 }
-            html_bytes = html.encode("utf8")
-            request.setResponseCode(200)
-            request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
-            request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
-
-            request.write(html_bytes)
-            finish_request(request)
-
-            return None
         elif stagetype == LoginType.TERMS:
             authdict = {"session": session}
 
@@ -225,17 +242,22 @@ class AuthRestServlet(RestServlet):
                     "myurl": "%s/r0/auth/%s/fallback/web"
                     % (CLIENT_API_PREFIX, LoginType.TERMS),
                 }
-            html_bytes = html.encode("utf8")
-            request.setResponseCode(200)
-            request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
-            request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
-
-            request.write(html_bytes)
-            finish_request(request)
-            return None
+        elif stagetype == LoginType.SSO:
+            # The SSO fallback workflow should not post here,
+            raise SynapseError(404, "Fallback SSO auth does not support POST requests.")
         else:
             raise SynapseError(404, "Unknown auth stage type")
 
+        # Render the HTML and return.
+        html_bytes = html.encode("utf8")
+        request.setResponseCode(200)
+        request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+        request.setHeader(b"Content-Length", b"%d" % (len(html_bytes),))
+
+        request.write(html_bytes)
+        finish_request(request)
+        return None
+
     def on_OPTIONS(self, _):
         return 200, {}
 
diff --git a/synapse/rest/client/v2_alpha/devices.py b/synapse/rest/client/v2_alpha/devices.py
index 94ff73f384..c0714fcfb1 100644
--- a/synapse/rest/client/v2_alpha/devices.py
+++ b/synapse/rest/client/v2_alpha/devices.py
@@ -81,7 +81,11 @@ class DeleteDevicesRestServlet(RestServlet):
         assert_params_in_dict(body, ["devices"])
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, body, self.hs.get_ip_from_request(request)
+            requester,
+            request,
+            body,
+            self.hs.get_ip_from_request(request),
+            "remove device(s) from your account",
         )
 
         await self.device_handler.delete_devices(
@@ -127,7 +131,11 @@ class DeviceRestServlet(RestServlet):
                 raise
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, body, self.hs.get_ip_from_request(request)
+            requester,
+            request,
+            body,
+            self.hs.get_ip_from_request(request),
+            "remove a device from your account",
         )
 
         await self.device_handler.delete_device(requester.user.to_string(), device_id)
diff --git a/synapse/rest/client/v2_alpha/keys.py b/synapse/rest/client/v2_alpha/keys.py
index f7ed4daf90..8f41a3edbf 100644
--- a/synapse/rest/client/v2_alpha/keys.py
+++ b/synapse/rest/client/v2_alpha/keys.py
@@ -263,7 +263,11 @@ class SigningKeyUploadServlet(RestServlet):
         body = parse_json_object_from_request(request)
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, body, self.hs.get_ip_from_request(request)
+            requester,
+            request,
+            body,
+            self.hs.get_ip_from_request(request),
+            "add a device signing key to your account",
         )
 
         result = await self.e2e_keys_handler.upload_signing_keys_for_user(user_id, body)
diff --git a/synapse/rest/client/v2_alpha/password_policy.py b/synapse/rest/client/v2_alpha/password_policy.py
new file mode 100644
index 0000000000..968403cca4
--- /dev/null
+++ b/synapse/rest/client/v2_alpha/password_policy.py
@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 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 synapse.http.servlet import RestServlet
+
+from ._base import client_patterns
+
+logger = logging.getLogger(__name__)
+
+
+class PasswordPolicyServlet(RestServlet):
+    PATTERNS = client_patterns("/password_policy$")
+
+    def __init__(self, hs):
+        """
+        Args:
+            hs (synapse.server.HomeServer): server
+        """
+        super(PasswordPolicyServlet, self).__init__()
+
+        self.policy = hs.config.password_policy
+        self.enabled = hs.config.password_policy_enabled
+
+    def on_GET(self, request):
+        if not self.enabled or not self.policy:
+            return (200, {})
+
+        policy = {}
+
+        for param in [
+            "minimum_length",
+            "require_digit",
+            "require_symbol",
+            "require_lowercase",
+            "require_uppercase",
+        ]:
+            if param in self.policy:
+                policy["m.%s" % param] = self.policy[param]
+
+        return (200, policy)
+
+
+def register_servlets(hs, http_server):
+    PasswordPolicyServlet(hs).register(http_server)
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index a09189b1b4..431ecf4f84 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -373,6 +373,7 @@ class RegisterRestServlet(RestServlet):
         self.room_member_handler = hs.get_room_member_handler()
         self.macaroon_gen = hs.get_macaroon_generator()
         self.ratelimiter = hs.get_registration_ratelimiter()
+        self.password_policy_handler = hs.get_password_policy_handler()
         self.clock = hs.get_clock()
 
         self._registration_flows = _calculate_registration_flows(
@@ -420,6 +421,7 @@ class RegisterRestServlet(RestServlet):
                 or len(body["password"]) > 512
             ):
                 raise SynapseError(400, "Invalid password")
+            self.password_policy_handler.validate_password(body["password"])
 
         desired_username = None
         if "username" in body:
@@ -499,7 +501,11 @@ class RegisterRestServlet(RestServlet):
             )
 
         auth_result, params, session_id = await self.auth_handler.check_auth(
-            self._registration_flows, body, self.hs.get_ip_from_request(request)
+            self._registration_flows,
+            request,
+            body,
+            self.hs.get_ip_from_request(request),
+            "register a new account",
         )
 
         # Check that we're not trying to register a denied 3pid.
diff --git a/synapse/rest/client/v2_alpha/room_keys.py b/synapse/rest/client/v2_alpha/room_keys.py
index 38952a1d27..59529707df 100644
--- a/synapse/rest/client/v2_alpha/room_keys.py
+++ b/synapse/rest/client/v2_alpha/room_keys.py
@@ -188,7 +188,7 @@ class RoomKeysServlet(RestServlet):
         """
         requester = await self.auth.get_user_by_req(request, allow_guest=False)
         user_id = requester.user.to_string()
-        version = parse_string(request, "version")
+        version = parse_string(request, "version", required=True)
 
         room_keys = await self.e2e_room_keys_handler.get_room_keys(
             user_id, version, room_id, session_id
diff --git a/synapse/rest/media/v1/download_resource.py b/synapse/rest/media/v1/download_resource.py
index 66a01559e1..24d3ae5bbc 100644
--- a/synapse/rest/media/v1/download_resource.py
+++ b/synapse/rest/media/v1/download_resource.py
@@ -50,6 +50,9 @@ class DownloadResource(DirectServeResource):
             b" media-src 'self';"
             b" object-src 'self';",
         )
+        request.setHeader(
+            b"Referrer-Policy", b"no-referrer",
+        )
         server_name, media_id, name = parse_media_id(request)
         if server_name == self.server_name:
             await self.media_repo.get_local_media(request, media_id, name)
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index 490b1b45a8..fd10d42f2f 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -24,7 +24,6 @@ from six import iteritems
 
 import twisted.internet.error
 import twisted.web.http
-from twisted.internet import defer
 from twisted.web.resource import Resource
 
 from synapse.api.errors import (
@@ -114,15 +113,14 @@ class MediaRepository(object):
             "update_recently_accessed_media", self._update_recently_accessed
         )
 
-    @defer.inlineCallbacks
-    def _update_recently_accessed(self):
+    async def _update_recently_accessed(self):
         remote_media = self.recently_accessed_remotes
         self.recently_accessed_remotes = set()
 
         local_media = self.recently_accessed_locals
         self.recently_accessed_locals = set()
 
-        yield self.store.update_cached_last_access_time(
+        await self.store.update_cached_last_access_time(
             local_media, remote_media, self.clock.time_msec()
         )
 
@@ -138,8 +136,7 @@ class MediaRepository(object):
         else:
             self.recently_accessed_locals.add(media_id)
 
-    @defer.inlineCallbacks
-    def create_content(
+    async def create_content(
         self, media_type, upload_name, content, content_length, auth_user
     ):
         """Store uploaded content for a local user and return the mxc URL
@@ -158,11 +155,11 @@ class MediaRepository(object):
 
         file_info = FileInfo(server_name=None, file_id=media_id)
 
-        fname = yield self.media_storage.store_file(content, file_info)
+        fname = await self.media_storage.store_file(content, file_info)
 
         logger.info("Stored local media in file %r", fname)
 
-        yield self.store.store_local_media(
+        await self.store.store_local_media(
             media_id=media_id,
             media_type=media_type,
             time_now_ms=self.clock.time_msec(),
@@ -171,12 +168,11 @@ class MediaRepository(object):
             user_id=auth_user,
         )
 
-        yield self._generate_thumbnails(None, media_id, media_id, media_type)
+        await self._generate_thumbnails(None, media_id, media_id, media_type)
 
         return "mxc://%s/%s" % (self.server_name, media_id)
 
-    @defer.inlineCallbacks
-    def get_local_media(self, request, media_id, name):
+    async def get_local_media(self, request, media_id, name):
         """Responds to reqests for local media, if exists, or returns 404.
 
         Args:
@@ -190,7 +186,7 @@ class MediaRepository(object):
             Deferred: Resolves once a response has successfully been written
                 to request
         """
-        media_info = yield self.store.get_local_media(media_id)
+        media_info = await self.store.get_local_media(media_id)
         if not media_info or media_info["quarantined_by"]:
             respond_404(request)
             return
@@ -204,13 +200,12 @@ class MediaRepository(object):
 
         file_info = FileInfo(None, media_id, url_cache=url_cache)
 
-        responder = yield self.media_storage.fetch_media(file_info)
-        yield respond_with_responder(
+        responder = await self.media_storage.fetch_media(file_info)
+        await respond_with_responder(
             request, responder, media_type, media_length, upload_name
         )
 
-    @defer.inlineCallbacks
-    def get_remote_media(self, request, server_name, media_id, name):
+    async def get_remote_media(self, request, server_name, media_id, name):
         """Respond to requests for remote media.
 
         Args:
@@ -236,8 +231,8 @@ class MediaRepository(object):
         # We linearize here to ensure that we don't try and download remote
         # media multiple times concurrently
         key = (server_name, media_id)
-        with (yield self.remote_media_linearizer.queue(key)):
-            responder, media_info = yield self._get_remote_media_impl(
+        with (await self.remote_media_linearizer.queue(key)):
+            responder, media_info = await self._get_remote_media_impl(
                 server_name, media_id
             )
 
@@ -246,14 +241,13 @@ class MediaRepository(object):
             media_type = media_info["media_type"]
             media_length = media_info["media_length"]
             upload_name = name if name else media_info["upload_name"]
-            yield respond_with_responder(
+            await respond_with_responder(
                 request, responder, media_type, media_length, upload_name
             )
         else:
             respond_404(request)
 
-    @defer.inlineCallbacks
-    def get_remote_media_info(self, server_name, media_id):
+    async def get_remote_media_info(self, server_name, media_id):
         """Gets the media info associated with the remote file, downloading
         if necessary.
 
@@ -274,8 +268,8 @@ class MediaRepository(object):
         # We linearize here to ensure that we don't try and download remote
         # media multiple times concurrently
         key = (server_name, media_id)
-        with (yield self.remote_media_linearizer.queue(key)):
-            responder, media_info = yield self._get_remote_media_impl(
+        with (await self.remote_media_linearizer.queue(key)):
+            responder, media_info = await self._get_remote_media_impl(
                 server_name, media_id
             )
 
@@ -286,8 +280,7 @@ class MediaRepository(object):
 
         return media_info
 
-    @defer.inlineCallbacks
-    def _get_remote_media_impl(self, server_name, media_id):
+    async def _get_remote_media_impl(self, server_name, media_id):
         """Looks for media in local cache, if not there then attempt to
         download from remote server.
 
@@ -299,7 +292,7 @@ class MediaRepository(object):
         Returns:
             Deferred[(Responder, media_info)]
         """
-        media_info = yield self.store.get_cached_remote_media(server_name, media_id)
+        media_info = await self.store.get_cached_remote_media(server_name, media_id)
 
         # file_id is the ID we use to track the file locally. If we've already
         # seen the file then reuse the existing ID, otherwise genereate a new
@@ -317,19 +310,18 @@ class MediaRepository(object):
                 logger.info("Media is quarantined")
                 raise NotFoundError()
 
-            responder = yield self.media_storage.fetch_media(file_info)
+            responder = await self.media_storage.fetch_media(file_info)
             if responder:
                 return responder, media_info
 
         # Failed to find the file anywhere, lets download it.
 
-        media_info = yield self._download_remote_file(server_name, media_id, file_id)
+        media_info = await self._download_remote_file(server_name, media_id, file_id)
 
-        responder = yield self.media_storage.fetch_media(file_info)
+        responder = await self.media_storage.fetch_media(file_info)
         return responder, media_info
 
-    @defer.inlineCallbacks
-    def _download_remote_file(self, server_name, media_id, file_id):
+    async def _download_remote_file(self, server_name, media_id, file_id):
         """Attempt to download the remote file from the given server name,
         using the given file_id as the local id.
 
@@ -351,7 +343,7 @@ class MediaRepository(object):
                 ("/_matrix/media/v1/download", server_name, media_id)
             )
             try:
-                length, headers = yield self.client.get_file(
+                length, headers = await self.client.get_file(
                     server_name,
                     request_path,
                     output_stream=f,
@@ -397,7 +389,7 @@ class MediaRepository(object):
                 )
                 raise SynapseError(502, "Failed to fetch remote media")
 
-            yield finish()
+            await finish()
 
         media_type = headers[b"Content-Type"][0].decode("ascii")
         upload_name = get_filename_from_headers(headers)
@@ -405,7 +397,7 @@ class MediaRepository(object):
 
         logger.info("Stored remote media in file %r", fname)
 
-        yield self.store.store_cached_remote_media(
+        await self.store.store_cached_remote_media(
             origin=server_name,
             media_id=media_id,
             media_type=media_type,
@@ -423,7 +415,7 @@ class MediaRepository(object):
             "filesystem_id": file_id,
         }
 
-        yield self._generate_thumbnails(server_name, media_id, file_id, media_type)
+        await self._generate_thumbnails(server_name, media_id, file_id, media_type)
 
         return media_info
 
@@ -458,16 +450,15 @@ class MediaRepository(object):
 
         return t_byte_source
 
-    @defer.inlineCallbacks
-    def generate_local_exact_thumbnail(
+    async def generate_local_exact_thumbnail(
         self, media_id, t_width, t_height, t_method, t_type, url_cache
     ):
-        input_path = yield self.media_storage.ensure_media_is_in_local_cache(
+        input_path = await self.media_storage.ensure_media_is_in_local_cache(
             FileInfo(None, media_id, url_cache=url_cache)
         )
 
         thumbnailer = Thumbnailer(input_path)
-        t_byte_source = yield defer_to_thread(
+        t_byte_source = await defer_to_thread(
             self.hs.get_reactor(),
             self._generate_thumbnail,
             thumbnailer,
@@ -490,7 +481,7 @@ class MediaRepository(object):
                     thumbnail_type=t_type,
                 )
 
-                output_path = yield self.media_storage.store_file(
+                output_path = await self.media_storage.store_file(
                     t_byte_source, file_info
                 )
             finally:
@@ -500,22 +491,21 @@ class MediaRepository(object):
 
             t_len = os.path.getsize(output_path)
 
-            yield self.store.store_local_thumbnail(
+            await self.store.store_local_thumbnail(
                 media_id, t_width, t_height, t_type, t_method, t_len
             )
 
             return output_path
 
-    @defer.inlineCallbacks
-    def generate_remote_exact_thumbnail(
+    async def generate_remote_exact_thumbnail(
         self, server_name, file_id, media_id, t_width, t_height, t_method, t_type
     ):
-        input_path = yield self.media_storage.ensure_media_is_in_local_cache(
+        input_path = await self.media_storage.ensure_media_is_in_local_cache(
             FileInfo(server_name, file_id, url_cache=False)
         )
 
         thumbnailer = Thumbnailer(input_path)
-        t_byte_source = yield defer_to_thread(
+        t_byte_source = await defer_to_thread(
             self.hs.get_reactor(),
             self._generate_thumbnail,
             thumbnailer,
@@ -537,7 +527,7 @@ class MediaRepository(object):
                     thumbnail_type=t_type,
                 )
 
-                output_path = yield self.media_storage.store_file(
+                output_path = await self.media_storage.store_file(
                     t_byte_source, file_info
                 )
             finally:
@@ -547,7 +537,7 @@ class MediaRepository(object):
 
             t_len = os.path.getsize(output_path)
 
-            yield self.store.store_remote_media_thumbnail(
+            await self.store.store_remote_media_thumbnail(
                 server_name,
                 media_id,
                 file_id,
@@ -560,8 +550,7 @@ class MediaRepository(object):
 
             return output_path
 
-    @defer.inlineCallbacks
-    def _generate_thumbnails(
+    async def _generate_thumbnails(
         self, server_name, media_id, file_id, media_type, url_cache=False
     ):
         """Generate and store thumbnails for an image.
@@ -582,7 +571,7 @@ class MediaRepository(object):
         if not requirements:
             return
 
-        input_path = yield self.media_storage.ensure_media_is_in_local_cache(
+        input_path = await self.media_storage.ensure_media_is_in_local_cache(
             FileInfo(server_name, file_id, url_cache=url_cache)
         )
 
@@ -600,7 +589,7 @@ class MediaRepository(object):
             return
 
         if thumbnailer.transpose_method is not None:
-            m_width, m_height = yield defer_to_thread(
+            m_width, m_height = await defer_to_thread(
                 self.hs.get_reactor(), thumbnailer.transpose
             )
 
@@ -620,11 +609,11 @@ class MediaRepository(object):
         for (t_width, t_height, t_type), t_method in iteritems(thumbnails):
             # Generate the thumbnail
             if t_method == "crop":
-                t_byte_source = yield defer_to_thread(
+                t_byte_source = await defer_to_thread(
                     self.hs.get_reactor(), thumbnailer.crop, t_width, t_height, t_type
                 )
             elif t_method == "scale":
-                t_byte_source = yield defer_to_thread(
+                t_byte_source = await defer_to_thread(
                     self.hs.get_reactor(), thumbnailer.scale, t_width, t_height, t_type
                 )
             else:
@@ -646,7 +635,7 @@ class MediaRepository(object):
                     url_cache=url_cache,
                 )
 
-                output_path = yield self.media_storage.store_file(
+                output_path = await self.media_storage.store_file(
                     t_byte_source, file_info
                 )
             finally:
@@ -656,7 +645,7 @@ class MediaRepository(object):
 
             # Write to database
             if server_name:
-                yield self.store.store_remote_media_thumbnail(
+                await self.store.store_remote_media_thumbnail(
                     server_name,
                     media_id,
                     file_id,
@@ -667,15 +656,14 @@ class MediaRepository(object):
                     t_len,
                 )
             else:
-                yield self.store.store_local_thumbnail(
+                await self.store.store_local_thumbnail(
                     media_id, t_width, t_height, t_type, t_method, t_len
                 )
 
         return {"width": m_width, "height": m_height}
 
-    @defer.inlineCallbacks
-    def delete_old_remote_media(self, before_ts):
-        old_media = yield self.store.get_remote_media_before(before_ts)
+    async def delete_old_remote_media(self, before_ts):
+        old_media = await self.store.get_remote_media_before(before_ts)
 
         deleted = 0
 
@@ -689,7 +677,7 @@ class MediaRepository(object):
 
             # TODO: Should we delete from the backup store
 
-            with (yield self.remote_media_linearizer.queue(key)):
+            with (await self.remote_media_linearizer.queue(key)):
                 full_path = self.filepaths.remote_media_filepath(origin, file_id)
                 try:
                     os.remove(full_path)
@@ -705,7 +693,7 @@ class MediaRepository(object):
                 )
                 shutil.rmtree(thumbnail_dir, ignore_errors=True)
 
-                yield self.store.delete_remote_media(origin, media_id)
+                await self.store.delete_remote_media(origin, media_id)
                 deleted += 1
 
         return {"deleted": deleted}
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 07e395cfd1..f206605727 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -86,6 +86,7 @@ class PreviewUrlResource(DirectServeResource):
         self.media_storage = media_storage
 
         self.url_preview_url_blacklist = hs.config.url_preview_url_blacklist
+        self.url_preview_accept_language = hs.config.url_preview_accept_language
 
         # memory cache mapping urls to an ObservableDeferred returning
         # JSON-encoded OG metadata
@@ -165,8 +166,7 @@ class PreviewUrlResource(DirectServeResource):
         og = await make_deferred_yieldable(defer.maybeDeferred(observable.observe))
         respond_with_json_bytes(request, 200, og, send_cors=True)
 
-    @defer.inlineCallbacks
-    def _do_preview(self, url, user, ts):
+    async def _do_preview(self, url, user, ts):
         """Check the db, and download the URL and build a preview
 
         Args:
@@ -179,7 +179,7 @@ class PreviewUrlResource(DirectServeResource):
         """
         # check the URL cache in the DB (which will also provide us with
         # historical previews, if we have any)
-        cache_result = yield self.store.get_url_cache(url, ts)
+        cache_result = await self.store.get_url_cache(url, ts)
         if (
             cache_result
             and cache_result["expires_ts"] > ts
@@ -192,13 +192,13 @@ class PreviewUrlResource(DirectServeResource):
                 og = og.encode("utf8")
             return og
 
-        media_info = yield self._download_url(url, user)
+        media_info = await self._download_url(url, user)
 
         logger.debug("got media_info of '%s'", media_info)
 
         if _is_media(media_info["media_type"]):
             file_id = media_info["filesystem_id"]
-            dims = yield self.media_repo._generate_thumbnails(
+            dims = await self.media_repo._generate_thumbnails(
                 None, file_id, file_id, media_info["media_type"], url_cache=True
             )
 
@@ -248,14 +248,14 @@ class PreviewUrlResource(DirectServeResource):
             # request itself and benefit from the same caching etc.  But for now we
             # just rely on the caching on the master request to speed things up.
             if "og:image" in og and og["og:image"]:
-                image_info = yield self._download_url(
+                image_info = await self._download_url(
                     _rebase_url(og["og:image"], media_info["uri"]), user
                 )
 
                 if _is_media(image_info["media_type"]):
                     # TODO: make sure we don't choke on white-on-transparent images
                     file_id = image_info["filesystem_id"]
-                    dims = yield self.media_repo._generate_thumbnails(
+                    dims = await self.media_repo._generate_thumbnails(
                         None, file_id, file_id, image_info["media_type"], url_cache=True
                     )
                     if dims:
@@ -293,7 +293,7 @@ class PreviewUrlResource(DirectServeResource):
         jsonog = json.dumps(og)
 
         # store OG in history-aware DB cache
-        yield self.store.store_url_cache(
+        await self.store.store_url_cache(
             url,
             media_info["response_code"],
             media_info["etag"],
@@ -305,8 +305,7 @@ class PreviewUrlResource(DirectServeResource):
 
         return jsonog.encode("utf8")
 
-    @defer.inlineCallbacks
-    def _download_url(self, url, user):
+    async def _download_url(self, url, user):
         # TODO: we should probably honour robots.txt... except in practice
         # we're most likely being explicitly triggered by a human rather than a
         # bot, so are we really a robot?
@@ -317,9 +316,12 @@ class PreviewUrlResource(DirectServeResource):
 
         with self.media_storage.store_into_file(file_info) as (f, fname, finish):
             try:
-                logger.debug("Trying to get url '%s'", url)
-                length, headers, uri, code = yield self.client.get_file(
-                    url, output_stream=f, max_size=self.max_spider_size
+                logger.debug("Trying to get preview for url '%s'", url)
+                length, headers, uri, code = await self.client.get_file(
+                    url,
+                    output_stream=f,
+                    max_size=self.max_spider_size,
+                    headers={"Accept-Language": self.url_preview_accept_language},
                 )
             except SynapseError:
                 # Pass SynapseErrors through directly, so that the servlet
@@ -345,7 +347,7 @@ class PreviewUrlResource(DirectServeResource):
                     % (traceback.format_exception_only(sys.exc_info()[0], e),),
                     Codes.UNKNOWN,
                 )
-            yield finish()
+            await finish()
 
         try:
             if b"Content-Type" in headers:
@@ -356,7 +358,7 @@ class PreviewUrlResource(DirectServeResource):
 
             download_name = get_filename_from_headers(headers)
 
-            yield self.store.store_local_media(
+            await self.store.store_local_media(
                 media_id=file_id,
                 media_type=media_type,
                 time_now_ms=self.clock.time_msec(),
@@ -393,22 +395,21 @@ class PreviewUrlResource(DirectServeResource):
             "expire_url_cache_data", self._expire_url_cache_data
         )
 
-    @defer.inlineCallbacks
-    def _expire_url_cache_data(self):
+    async def _expire_url_cache_data(self):
         """Clean up expired url cache content, media and thumbnails.
         """
         # TODO: Delete from backup media store
 
         now = self.clock.time_msec()
 
-        logger.info("Running url preview cache expiry")
+        logger.debug("Running url preview cache expiry")
 
-        if not (yield self.store.db.updates.has_completed_background_updates()):
+        if not (await self.store.db.updates.has_completed_background_updates()):
             logger.info("Still running DB updates; skipping expiry")
             return
 
         # First we delete expired url cache entries
-        media_ids = yield self.store.get_expired_url_cache(now)
+        media_ids = await self.store.get_expired_url_cache(now)
 
         removed_media = []
         for media_id in media_ids:
@@ -430,17 +431,19 @@ class PreviewUrlResource(DirectServeResource):
             except Exception:
                 pass
 
-        yield self.store.delete_url_cache(removed_media)
+        await self.store.delete_url_cache(removed_media)
 
         if removed_media:
             logger.info("Deleted %d entries from url cache", len(removed_media))
+        else:
+            logger.debug("No entries removed from url cache")
 
         # Now we delete old images associated with the url cache.
         # These may be cached for a bit on the client (i.e., they
         # may have a room open with a preview url thing open).
         # So we wait a couple of days before deleting, just in case.
         expire_before = now - 2 * 24 * 60 * 60 * 1000
-        media_ids = yield self.store.get_url_cache_media_before(expire_before)
+        media_ids = await self.store.get_url_cache_media_before(expire_before)
 
         removed_media = []
         for media_id in media_ids:
@@ -478,9 +481,12 @@ class PreviewUrlResource(DirectServeResource):
             except Exception:
                 pass
 
-        yield self.store.delete_url_cache_media(removed_media)
+        await self.store.delete_url_cache_media(removed_media)
 
-        logger.info("Deleted %d media from url cache", len(removed_media))
+        if removed_media:
+            logger.info("Deleted %d media from url cache", len(removed_media))
+        else:
+            logger.debug("No media removed from url cache")
 
 
 def decode_and_calc_og(body, media_uri, request_encoding=None):
diff --git a/synapse/rest/media/v1/thumbnail_resource.py b/synapse/rest/media/v1/thumbnail_resource.py
index d57480f761..0b87220234 100644
--- a/synapse/rest/media/v1/thumbnail_resource.py
+++ b/synapse/rest/media/v1/thumbnail_resource.py
@@ -16,8 +16,6 @@
 
 import logging
 
-from twisted.internet import defer
-
 from synapse.http.server import (
     DirectServeResource,
     set_cors_headers,
@@ -79,11 +77,10 @@ class ThumbnailResource(DirectServeResource):
                 )
             self.media_repo.mark_recently_accessed(server_name, media_id)
 
-    @defer.inlineCallbacks
-    def _respond_local_thumbnail(
+    async def _respond_local_thumbnail(
         self, request, media_id, width, height, method, m_type
     ):
-        media_info = yield self.store.get_local_media(media_id)
+        media_info = await self.store.get_local_media(media_id)
 
         if not media_info:
             respond_404(request)
@@ -93,7 +90,7 @@ class ThumbnailResource(DirectServeResource):
             respond_404(request)
             return
 
-        thumbnail_infos = yield self.store.get_local_media_thumbnails(media_id)
+        thumbnail_infos = await self.store.get_local_media_thumbnails(media_id)
 
         if thumbnail_infos:
             thumbnail_info = self._select_thumbnail(
@@ -114,14 +111,13 @@ class ThumbnailResource(DirectServeResource):
             t_type = file_info.thumbnail_type
             t_length = thumbnail_info["thumbnail_length"]
 
-            responder = yield self.media_storage.fetch_media(file_info)
-            yield respond_with_responder(request, responder, t_type, t_length)
+            responder = await self.media_storage.fetch_media(file_info)
+            await respond_with_responder(request, responder, t_type, t_length)
         else:
             logger.info("Couldn't find any generated thumbnails")
             respond_404(request)
 
-    @defer.inlineCallbacks
-    def _select_or_generate_local_thumbnail(
+    async def _select_or_generate_local_thumbnail(
         self,
         request,
         media_id,
@@ -130,7 +126,7 @@ class ThumbnailResource(DirectServeResource):
         desired_method,
         desired_type,
     ):
-        media_info = yield self.store.get_local_media(media_id)
+        media_info = await self.store.get_local_media(media_id)
 
         if not media_info:
             respond_404(request)
@@ -140,7 +136,7 @@ class ThumbnailResource(DirectServeResource):
             respond_404(request)
             return
 
-        thumbnail_infos = yield self.store.get_local_media_thumbnails(media_id)
+        thumbnail_infos = await self.store.get_local_media_thumbnails(media_id)
         for info in thumbnail_infos:
             t_w = info["thumbnail_width"] == desired_width
             t_h = info["thumbnail_height"] == desired_height
@@ -162,15 +158,15 @@ class ThumbnailResource(DirectServeResource):
                 t_type = file_info.thumbnail_type
                 t_length = info["thumbnail_length"]
 
-                responder = yield self.media_storage.fetch_media(file_info)
+                responder = await self.media_storage.fetch_media(file_info)
                 if responder:
-                    yield respond_with_responder(request, responder, t_type, t_length)
+                    await respond_with_responder(request, responder, t_type, t_length)
                     return
 
         logger.debug("We don't have a thumbnail of that size. Generating")
 
         # Okay, so we generate one.
-        file_path = yield self.media_repo.generate_local_exact_thumbnail(
+        file_path = await self.media_repo.generate_local_exact_thumbnail(
             media_id,
             desired_width,
             desired_height,
@@ -180,13 +176,12 @@ class ThumbnailResource(DirectServeResource):
         )
 
         if file_path:
-            yield respond_with_file(request, desired_type, file_path)
+            await respond_with_file(request, desired_type, file_path)
         else:
             logger.warning("Failed to generate thumbnail")
             respond_404(request)
 
-    @defer.inlineCallbacks
-    def _select_or_generate_remote_thumbnail(
+    async def _select_or_generate_remote_thumbnail(
         self,
         request,
         server_name,
@@ -196,9 +191,9 @@ class ThumbnailResource(DirectServeResource):
         desired_method,
         desired_type,
     ):
-        media_info = yield self.media_repo.get_remote_media_info(server_name, media_id)
+        media_info = await self.media_repo.get_remote_media_info(server_name, media_id)
 
-        thumbnail_infos = yield self.store.get_remote_media_thumbnails(
+        thumbnail_infos = await self.store.get_remote_media_thumbnails(
             server_name, media_id
         )
 
@@ -224,15 +219,15 @@ class ThumbnailResource(DirectServeResource):
                 t_type = file_info.thumbnail_type
                 t_length = info["thumbnail_length"]
 
-                responder = yield self.media_storage.fetch_media(file_info)
+                responder = await self.media_storage.fetch_media(file_info)
                 if responder:
-                    yield respond_with_responder(request, responder, t_type, t_length)
+                    await respond_with_responder(request, responder, t_type, t_length)
                     return
 
         logger.debug("We don't have a thumbnail of that size. Generating")
 
         # Okay, so we generate one.
-        file_path = yield self.media_repo.generate_remote_exact_thumbnail(
+        file_path = await self.media_repo.generate_remote_exact_thumbnail(
             server_name,
             file_id,
             media_id,
@@ -243,21 +238,20 @@ class ThumbnailResource(DirectServeResource):
         )
 
         if file_path:
-            yield respond_with_file(request, desired_type, file_path)
+            await respond_with_file(request, desired_type, file_path)
         else:
             logger.warning("Failed to generate thumbnail")
             respond_404(request)
 
-    @defer.inlineCallbacks
-    def _respond_remote_thumbnail(
+    async def _respond_remote_thumbnail(
         self, request, server_name, media_id, width, height, method, m_type
     ):
         # TODO: Don't download the whole remote file
         # We should proxy the thumbnail from the remote server instead of
         # downloading the remote file and generating our own thumbnails.
-        media_info = yield self.media_repo.get_remote_media_info(server_name, media_id)
+        media_info = await self.media_repo.get_remote_media_info(server_name, media_id)
 
-        thumbnail_infos = yield self.store.get_remote_media_thumbnails(
+        thumbnail_infos = await self.store.get_remote_media_thumbnails(
             server_name, media_id
         )
 
@@ -278,8 +272,8 @@ class ThumbnailResource(DirectServeResource):
             t_type = file_info.thumbnail_type
             t_length = thumbnail_info["thumbnail_length"]
 
-            responder = yield self.media_storage.fetch_media(file_info)
-            yield respond_with_responder(request, responder, t_type, t_length)
+            responder = await self.media_storage.fetch_media(file_info)
+            await respond_with_responder(request, responder, t_type, t_length)
         else:
             logger.info("Failed to find any generated thumbnails")
             respond_404(request)