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-rw-r--r--changelog.d/10658.bugfix1
-rw-r--r--changelog.d/10707.misc1
-rw-r--r--changelog.d/10712.feature1
-rw-r--r--changelog.d/10714.feature1
-rw-r--r--docs/sample_config.yaml21
-rw-r--r--synapse/app/_base.py7
-rw-r--r--synapse/config/homeserver.py2
-rw-r--r--synapse/config/oembed.py180
-rw-r--r--synapse/push/mailer.py24
-rw-r--r--synapse/res/providers.json17
-rw-r--r--synapse/rest/client/account_data.py37
-rw-r--r--synapse/rest/client/groups.py12
-rw-r--r--synapse/rest/client/receipts.py15
-rw-r--r--synapse/rest/client/register.py78
-rw-r--r--synapse/rest/client/relations.py80
-rw-r--r--synapse/rest/client/room.py233
-rw-r--r--synapse/rest/media/v1/oembed.py135
-rw-r--r--synapse/rest/media/v1/preview_url_resource.py147
-rw-r--r--tests/push/test_email.py52
-rw-r--r--tests/rest/media/v1/test_url_preview.py212
20 files changed, 848 insertions, 408 deletions
diff --git a/changelog.d/10658.bugfix b/changelog.d/10658.bugfix
new file mode 100644
index 0000000000..a59d402933
--- /dev/null
+++ b/changelog.d/10658.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where room avatars were not included in email notifications.
diff --git a/changelog.d/10707.misc b/changelog.d/10707.misc
new file mode 100644
index 0000000000..39a37b90b1
--- /dev/null
+++ b/changelog.d/10707.misc
@@ -0,0 +1 @@
+Add missing type hints to REST servlets.
diff --git a/changelog.d/10712.feature b/changelog.d/10712.feature
new file mode 100644
index 0000000000..d04db6f26f
--- /dev/null
+++ b/changelog.d/10712.feature
@@ -0,0 +1 @@
+Skip final GC at shutdown to improve restart performance.
diff --git a/changelog.d/10714.feature b/changelog.d/10714.feature
new file mode 100644
index 0000000000..7d18f5c133
--- /dev/null
+++ b/changelog.d/10714.feature
@@ -0,0 +1 @@
+Allow configuration of the oEmbed URLs used for URL previews.
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index 935841dbfa..e155b978d8 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -1075,6 +1075,27 @@ url_preview_accept_language:
 #   - en
 
 
+# oEmbed allows for easier embedding content from a website. It can be
+# used for generating URLs previews of services which support it.
+#
+oembed:
+  # A default list of oEmbed providers is included with Synapse.
+  #
+  # Uncomment the following to disable using these default oEmbed URLs.
+  # Defaults to 'false'.
+  #
+  #disable_default_providers: true
+
+  # Additional files with oEmbed configuration (each should be in the
+  # form of providers.json).
+  #
+  # By default, this list is empty (so only the default providers.json
+  # is used).
+  #
+  #additional_providers:
+  #  - oembed/my_providers.json
+
+
 ## Captcha ##
 # See docs/CAPTCHA_SETUP.md for full details of configuring this.
 
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index 39e28aff9f..6fc14930d1 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -12,6 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import atexit
 import gc
 import logging
 import os
@@ -403,6 +404,12 @@ async def start(hs: "HomeServer"):
         gc.collect()
         gc.freeze()
 
+    # Speed up shutdowns by freezing all allocated objects. This moves everything
+    # into the permanent generation and excludes them from the final GC.
+    # Unfortunately only works on Python 3.7
+    if platform.python_implementation() == "CPython" and sys.version_info >= (3, 7):
+        atexit.register(gc.freeze)
+
 
 def setup_sentry(hs):
     """Enable sentry integration, if enabled in configuration
diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index 1f42a51857..442f1b9ac0 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -30,6 +30,7 @@ from .key import KeyConfig
 from .logger import LoggingConfig
 from .metrics import MetricsConfig
 from .modules import ModulesConfig
+from .oembed import OembedConfig
 from .oidc import OIDCConfig
 from .password_auth_providers import PasswordAuthProviderConfig
 from .push import PushConfig
@@ -65,6 +66,7 @@ class HomeServerConfig(RootConfig):
         LoggingConfig,
         RatelimitConfig,
         ContentRepositoryConfig,
+        OembedConfig,
         CaptchaConfig,
         VoipConfig,
         RegistrationConfig,
diff --git a/synapse/config/oembed.py b/synapse/config/oembed.py
new file mode 100644
index 0000000000..09267b5eef
--- /dev/null
+++ b/synapse/config/oembed.py
@@ -0,0 +1,180 @@
+# Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import json
+import re
+from typing import Any, Dict, Iterable, List, Pattern
+from urllib import parse as urlparse
+
+import attr
+import pkg_resources
+
+from synapse.types import JsonDict
+
+from ._base import Config, ConfigError
+from ._util import validate_config
+
+
+@attr.s(slots=True, frozen=True, auto_attribs=True)
+class OEmbedEndpointConfig:
+    # The API endpoint to fetch.
+    api_endpoint: str
+    # The patterns to match.
+    url_patterns: List[Pattern]
+
+
+class OembedConfig(Config):
+    """oEmbed Configuration"""
+
+    section = "oembed"
+
+    def read_config(self, config, **kwargs):
+        oembed_config: Dict[str, Any] = config.get("oembed") or {}
+
+        # A list of patterns which will be used.
+        self.oembed_patterns: List[OEmbedEndpointConfig] = list(
+            self._parse_and_validate_providers(oembed_config)
+        )
+
+    def _parse_and_validate_providers(
+        self, oembed_config: dict
+    ) -> Iterable[OEmbedEndpointConfig]:
+        """Extract and parse the oEmbed providers from the given JSON file.
+
+        Returns a generator which yields the OidcProviderConfig objects
+        """
+        # Whether to use the packaged providers.json file.
+        if not oembed_config.get("disable_default_providers") or False:
+            providers = json.load(
+                pkg_resources.resource_stream("synapse", "res/providers.json")
+            )
+            yield from self._parse_and_validate_provider(
+                providers, config_path=("oembed",)
+            )
+
+        # The JSON files which includes additional provider information.
+        for i, file in enumerate(oembed_config.get("additional_providers") or []):
+            # TODO Error checking.
+            with open(file) as f:
+                providers = json.load(f)
+
+            yield from self._parse_and_validate_provider(
+                providers,
+                config_path=(
+                    "oembed",
+                    "additional_providers",
+                    f"<item {i}>",
+                ),
+            )
+
+    def _parse_and_validate_provider(
+        self, providers: List[JsonDict], config_path: Iterable[str]
+    ) -> Iterable[OEmbedEndpointConfig]:
+        # Ensure it is the proper form.
+        validate_config(
+            _OEMBED_PROVIDER_SCHEMA,
+            providers,
+            config_path=config_path,
+        )
+
+        # Parse it and yield each result.
+        for provider in providers:
+            # Each provider might have multiple API endpoints, each which
+            # might have multiple patterns to match.
+            for endpoint in provider["endpoints"]:
+                api_endpoint = endpoint["url"]
+                patterns = [
+                    self._glob_to_pattern(glob, config_path)
+                    for glob in endpoint["schemes"]
+                ]
+                yield OEmbedEndpointConfig(api_endpoint, patterns)
+
+    def _glob_to_pattern(self, glob: str, config_path: Iterable[str]) -> Pattern:
+        """
+        Convert the glob into a sane regular expression to match against. The
+        rules followed will be slightly different for the domain portion vs.
+        the rest.
+
+        1. The scheme must be one of HTTP / HTTPS (and have no globs).
+        2. The domain can have globs, but we limit it to characters that can
+           reasonably be a domain part.
+           TODO: This does not attempt to handle Unicode domain names.
+           TODO: The domain should not allow wildcard TLDs.
+        3. Other parts allow a glob to be any one, or more, characters.
+        """
+        results = urlparse.urlparse(glob)
+
+        # Ensure the scheme does not have wildcards (and is a sane scheme).
+        if results.scheme not in {"http", "https"}:
+            raise ConfigError(f"Insecure oEmbed scheme: {results.scheme}", config_path)
+
+        pattern = urlparse.urlunparse(
+            [
+                results.scheme,
+                re.escape(results.netloc).replace("\\*", "[a-zA-Z0-9_-]+"),
+            ]
+            + [re.escape(part).replace("\\*", ".+") for part in results[2:]]
+        )
+        return re.compile(pattern)
+
+    def generate_config_section(self, **kwargs):
+        return """\
+        # oEmbed allows for easier embedding content from a website. It can be
+        # used for generating URLs previews of services which support it.
+        #
+        oembed:
+          # A default list of oEmbed providers is included with Synapse.
+          #
+          # Uncomment the following to disable using these default oEmbed URLs.
+          # Defaults to 'false'.
+          #
+          #disable_default_providers: true
+
+          # Additional files with oEmbed configuration (each should be in the
+          # form of providers.json).
+          #
+          # By default, this list is empty (so only the default providers.json
+          # is used).
+          #
+          #additional_providers:
+          #  - oembed/my_providers.json
+        """
+
+
+_OEMBED_PROVIDER_SCHEMA = {
+    "type": "array",
+    "items": {
+        "type": "object",
+        "properties": {
+            "provider_name": {"type": "string"},
+            "provider_url": {"type": "string"},
+            "endpoints": {
+                "type": "array",
+                "items": {
+                    "type": "object",
+                    "properties": {
+                        "schemes": {
+                            "type": "array",
+                            "items": {"type": "string"},
+                        },
+                        "url": {"type": "string"},
+                        "formats": {"type": "array", "items": {"type": "string"}},
+                        "discovery": {"type": "boolean"},
+                    },
+                    "required": ["schemes", "url"],
+                },
+            },
+        },
+        "required": ["provider_name", "provider_url", "endpoints"],
+    },
+}
diff --git a/synapse/push/mailer.py b/synapse/push/mailer.py
index 941fb238b7..b0834720ad 100644
--- a/synapse/push/mailer.py
+++ b/synapse/push/mailer.py
@@ -258,7 +258,7 @@ class Mailer:
         # actually sort our so-called rooms_in_order list, most recent room first
         rooms_in_order.sort(key=lambda r: -(notifs_by_room[r][-1]["received_ts"] or 0))
 
-        rooms = []
+        rooms: List[Dict[str, Any]] = []
 
         for r in rooms_in_order:
             roomvars = await self._get_room_vars(
@@ -362,6 +362,7 @@ class Mailer:
             "notifs": [],
             "invite": is_invite,
             "link": self._make_room_link(room_id),
+            "avatar_url": await self._get_room_avatar(room_state_ids),
         }
 
         if not is_invite:
@@ -393,6 +394,27 @@ class Mailer:
 
         return room_vars
 
+    async def _get_room_avatar(
+        self,
+        room_state_ids: StateMap[str],
+    ) -> Optional[str]:
+        """
+        Retrieve the avatar url for this room---if it exists.
+
+        Args:
+            room_state_ids: The event IDs of the current room state.
+
+        Returns:
+             room's avatar url if it's present and a string; otherwise None.
+        """
+        event_id = room_state_ids.get((EventTypes.RoomAvatar, ""))
+        if event_id:
+            ev = await self.store.get_event(event_id)
+            url = ev.content.get("url")
+            if isinstance(url, str):
+                return url
+        return None
+
     async def _get_notif_vars(
         self,
         notif: Dict[str, Any],
diff --git a/synapse/res/providers.json b/synapse/res/providers.json
new file mode 100644
index 0000000000..f1838f9559
--- /dev/null
+++ b/synapse/res/providers.json
@@ -0,0 +1,17 @@
+[
+    {
+        "provider_name": "Twitter",
+        "provider_url": "http://www.twitter.com/",
+        "endpoints": [
+            {
+                "schemes": [
+                    "https://twitter.com/*/status/*",
+                    "https://*.twitter.com/*/status/*",
+                    "https://twitter.com/*/moments/*",
+                    "https://*.twitter.com/*/moments/*"
+                ],
+                "url": "https://publish.twitter.com/oembed"
+            }
+        ]
+    }
+]
\ No newline at end of file
diff --git a/synapse/rest/client/account_data.py b/synapse/rest/client/account_data.py
index 7517e9304e..d1badbdf3b 100644
--- a/synapse/rest/client/account_data.py
+++ b/synapse/rest/client/account_data.py
@@ -13,12 +13,19 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING, Tuple
 
 from synapse.api.errors import AuthError, NotFoundError, SynapseError
+from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
+from synapse.types import JsonDict
 
 from ._base import client_patterns
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -32,13 +39,15 @@ class AccountDataServlet(RestServlet):
         "/user/(?P<user_id>[^/]*)/account_data/(?P<account_data_type>[^/]*)"
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
         self.handler = hs.get_account_data_handler()
 
-    async def on_PUT(self, request, user_id, account_data_type):
+    async def on_PUT(
+        self, request: SynapseRequest, user_id: str, account_data_type: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         if user_id != requester.user.to_string():
             raise AuthError(403, "Cannot add account data for other users.")
@@ -49,7 +58,9 @@ class AccountDataServlet(RestServlet):
 
         return 200, {}
 
-    async def on_GET(self, request, user_id, account_data_type):
+    async def on_GET(
+        self, request: SynapseRequest, user_id: str, account_data_type: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         if user_id != requester.user.to_string():
             raise AuthError(403, "Cannot get account data for other users.")
@@ -76,13 +87,19 @@ class RoomAccountDataServlet(RestServlet):
         "/account_data/(?P<account_data_type>[^/]*)"
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
         self.handler = hs.get_account_data_handler()
 
-    async def on_PUT(self, request, user_id, room_id, account_data_type):
+    async def on_PUT(
+        self,
+        request: SynapseRequest,
+        user_id: str,
+        room_id: str,
+        account_data_type: str,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         if user_id != requester.user.to_string():
             raise AuthError(403, "Cannot add account data for other users.")
@@ -102,7 +119,13 @@ class RoomAccountDataServlet(RestServlet):
 
         return 200, {}
 
-    async def on_GET(self, request, user_id, room_id, account_data_type):
+    async def on_GET(
+        self,
+        request: SynapseRequest,
+        user_id: str,
+        room_id: str,
+        account_data_type: str,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         if user_id != requester.user.to_string():
             raise AuthError(403, "Cannot get account data for other users.")
@@ -117,6 +140,6 @@ class RoomAccountDataServlet(RestServlet):
         return 200, event
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     AccountDataServlet(hs).register(http_server)
     RoomAccountDataServlet(hs).register(http_server)
diff --git a/synapse/rest/client/groups.py b/synapse/rest/client/groups.py
index c3667ff8aa..0950f43f2f 100644
--- a/synapse/rest/client/groups.py
+++ b/synapse/rest/client/groups.py
@@ -156,7 +156,7 @@ class GroupSummaryRoomsCatServlet(RestServlet):
         group_id: str,
         category_id: Optional[str],
         room_id: str,
-    ):
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         requester_user_id = requester.user.to_string()
 
@@ -188,7 +188,7 @@ class GroupSummaryRoomsCatServlet(RestServlet):
     @_validate_group_id
     async def on_DELETE(
         self, request: SynapseRequest, group_id: str, category_id: str, room_id: str
-    ):
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         requester_user_id = requester.user.to_string()
 
@@ -451,7 +451,7 @@ class GroupSummaryUsersRoleServlet(RestServlet):
     @_validate_group_id
     async def on_DELETE(
         self, request: SynapseRequest, group_id: str, role_id: str, user_id: str
-    ):
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         requester_user_id = requester.user.to_string()
 
@@ -674,7 +674,7 @@ class GroupAdminRoomsConfigServlet(RestServlet):
     @_validate_group_id
     async def on_PUT(
         self, request: SynapseRequest, group_id: str, room_id: str, config_key: str
-    ):
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         requester_user_id = requester.user.to_string()
 
@@ -706,7 +706,7 @@ class GroupAdminUsersInviteServlet(RestServlet):
 
     @_validate_group_id
     async def on_PUT(
-        self, request: SynapseRequest, group_id, user_id
+        self, request: SynapseRequest, group_id: str, user_id: str
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         requester_user_id = requester.user.to_string()
@@ -738,7 +738,7 @@ class GroupAdminUsersKickServlet(RestServlet):
 
     @_validate_group_id
     async def on_PUT(
-        self, request: SynapseRequest, group_id, user_id
+        self, request: SynapseRequest, group_id: str, user_id: str
     ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         requester_user_id = requester.user.to_string()
diff --git a/synapse/rest/client/receipts.py b/synapse/rest/client/receipts.py
index d9ab836cd8..9770413c61 100644
--- a/synapse/rest/client/receipts.py
+++ b/synapse/rest/client/receipts.py
@@ -13,13 +13,20 @@
 # limitations under the License.
 
 import logging
+from typing import TYPE_CHECKING, Tuple
 
 from synapse.api.constants import ReadReceiptEventFields
 from synapse.api.errors import Codes, SynapseError
+from synapse.http.server import HttpServer
 from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.http.site import SynapseRequest
+from synapse.types import JsonDict
 
 from ._base import client_patterns
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -30,14 +37,16 @@ class ReceiptRestServlet(RestServlet):
         "/(?P<event_id>[^/]*)$"
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
         self.receipts_handler = hs.get_receipts_handler()
         self.presence_handler = hs.get_presence_handler()
 
-    async def on_POST(self, request, room_id, receipt_type, event_id):
+    async def on_POST(
+        self, request: SynapseRequest, room_id: str, receipt_type: str, event_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         if receipt_type != "m.read":
@@ -67,5 +76,5 @@ class ReceiptRestServlet(RestServlet):
         return 200, {}
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     ReceiptRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/register.py b/synapse/rest/client/register.py
index 7b5f49d635..a28acd4041 100644
--- a/synapse/rest/client/register.py
+++ b/synapse/rest/client/register.py
@@ -14,7 +14,9 @@
 # limitations under the License.
 import logging
 import random
-from typing import List, Union
+from typing import TYPE_CHECKING, List, Optional, Tuple
+
+from twisted.web.server import Request
 
 import synapse
 import synapse.api.auth
@@ -29,15 +31,13 @@ from synapse.api.errors import (
 )
 from synapse.api.ratelimiting import Ratelimiter
 from synapse.config import ConfigError
-from synapse.config.captcha import CaptchaConfig
-from synapse.config.consent import ConsentConfig
 from synapse.config.emailconfig import ThreepidBehaviour
+from synapse.config.homeserver import HomeServerConfig
 from synapse.config.ratelimiting import FederationRateLimitConfig
-from synapse.config.registration import RegistrationConfig
 from synapse.config.server import is_threepid_reserved
 from synapse.handlers.auth import AuthHandler
 from synapse.handlers.ui_auth import UIAuthSessionDataConstants
-from synapse.http.server import finish_request, respond_with_html
+from synapse.http.server import HttpServer, finish_request, respond_with_html
 from synapse.http.servlet import (
     RestServlet,
     assert_params_in_dict,
@@ -45,6 +45,7 @@ from synapse.http.servlet import (
     parse_json_object_from_request,
     parse_string,
 )
+from synapse.http.site import SynapseRequest
 from synapse.metrics import threepid_send_requests
 from synapse.push.mailer import Mailer
 from synapse.types import JsonDict
@@ -59,17 +60,16 @@ from synapse.util.threepids import (
 
 from ._base import client_patterns, interactive_auth_handler
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
 class EmailRegisterRequestTokenRestServlet(RestServlet):
     PATTERNS = client_patterns("/register/email/requestToken$")
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.identity_handler = hs.get_identity_handler()
@@ -83,7 +83,7 @@ class EmailRegisterRequestTokenRestServlet(RestServlet):
                 template_text=self.config.email_registration_template_text,
             )
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         if self.hs.config.threepid_behaviour_email == ThreepidBehaviour.OFF:
             if self.hs.config.local_threepid_handling_disabled_due_to_email_config:
                 logger.warning(
@@ -171,16 +171,12 @@ class EmailRegisterRequestTokenRestServlet(RestServlet):
 class MsisdnRegisterRequestTokenRestServlet(RestServlet):
     PATTERNS = client_patterns("/register/msisdn/requestToken$")
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.identity_handler = hs.get_identity_handler()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         body = parse_json_object_from_request(request)
 
         assert_params_in_dict(
@@ -255,11 +251,7 @@ class RegistrationSubmitTokenServlet(RestServlet):
         "/registration/(?P<medium>[^/]*)/submit_token$", releases=(), unstable=True
     )
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.auth = hs.get_auth()
@@ -272,7 +264,7 @@ class RegistrationSubmitTokenServlet(RestServlet):
                 self.config.email_registration_template_failure_html
             )
 
-    async def on_GET(self, request, medium):
+    async def on_GET(self, request: Request, medium: str) -> None:
         if medium != "email":
             raise SynapseError(
                 400, "This medium is currently not supported for registration"
@@ -326,11 +318,7 @@ class RegistrationSubmitTokenServlet(RestServlet):
 class UsernameAvailabilityRestServlet(RestServlet):
     PATTERNS = client_patterns("/register/available")
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.hs = hs
         self.registration_handler = hs.get_registration_handler()
@@ -350,7 +338,7 @@ class UsernameAvailabilityRestServlet(RestServlet):
             ),
         )
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: Request) -> Tuple[int, JsonDict]:
         if not self.hs.config.enable_registration:
             raise SynapseError(
                 403, "Registration has been disabled", errcode=Codes.FORBIDDEN
@@ -419,11 +407,7 @@ class RegistrationTokenValidityRestServlet(RestServlet):
 class RegisterRestServlet(RestServlet):
     PATTERNS = client_patterns("/register$")
 
-    def __init__(self, hs):
-        """
-        Args:
-            hs (synapse.server.HomeServer): server
-        """
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
 
         self.hs = hs
@@ -445,23 +429,21 @@ class RegisterRestServlet(RestServlet):
         )
 
     @interactive_auth_handler
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         body = parse_json_object_from_request(request)
 
         client_addr = request.getClientIP()
 
         await self.ratelimiter.ratelimit(None, client_addr, update=False)
 
-        kind = b"user"
-        if b"kind" in request.args:
-            kind = request.args[b"kind"][0]
+        kind = parse_string(request, "kind", default="user")
 
-        if kind == b"guest":
+        if kind == "guest":
             ret = await self._do_guest_registration(body, address=client_addr)
             return ret
-        elif kind != b"user":
+        elif kind != "user":
             raise UnrecognizedRequestError(
-                "Do not understand membership kind: %s" % (kind.decode("utf8"),)
+                f"Do not understand membership kind: {kind}",
             )
 
         if self._msc2918_enabled:
@@ -749,7 +731,7 @@ class RegisterRestServlet(RestServlet):
 
     async def _do_appservice_registration(
         self, username, as_token, body, should_issue_refresh_token: bool = False
-    ):
+    ) -> JsonDict:
         user_id = await self.registration_handler.appservice_register(
             username, as_token
         )
@@ -766,7 +748,7 @@ class RegisterRestServlet(RestServlet):
         params: JsonDict,
         is_appservice_ghost: bool = False,
         should_issue_refresh_token: bool = False,
-    ):
+    ) -> JsonDict:
         """Complete registration of newly-registered user
 
         Allocates device_id if one was not given; also creates access_token.
@@ -810,7 +792,9 @@ class RegisterRestServlet(RestServlet):
 
         return result
 
-    async def _do_guest_registration(self, params, address=None):
+    async def _do_guest_registration(
+        self, params: JsonDict, address: Optional[str] = None
+    ) -> Tuple[int, JsonDict]:
         if not self.hs.config.allow_guest_access:
             raise SynapseError(403, "Guest access is disabled")
         user_id = await self.registration_handler.register_user(
@@ -848,9 +832,7 @@ class RegisterRestServlet(RestServlet):
 
 
 def _calculate_registration_flows(
-    # technically `config` has to provide *all* of these interfaces, not just one
-    config: Union[RegistrationConfig, ConsentConfig, CaptchaConfig],
-    auth_handler: AuthHandler,
+    config: HomeServerConfig, auth_handler: AuthHandler
 ) -> List[List[str]]:
     """Get a suitable flows list for registration
 
@@ -929,7 +911,7 @@ def _calculate_registration_flows(
     return flows
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     EmailRegisterRequestTokenRestServlet(hs).register(http_server)
     MsisdnRegisterRequestTokenRestServlet(hs).register(http_server)
     UsernameAvailabilityRestServlet(hs).register(http_server)
diff --git a/synapse/rest/client/relations.py b/synapse/rest/client/relations.py
index 0821cd285f..0b0711c03c 100644
--- a/synapse/rest/client/relations.py
+++ b/synapse/rest/client/relations.py
@@ -19,25 +19,32 @@ any time to reflect changes in the MSC.
 """
 
 import logging
+from typing import TYPE_CHECKING, Awaitable, Optional, Tuple
 
 from synapse.api.constants import EventTypes, RelationTypes
 from synapse.api.errors import ShadowBanError, SynapseError
+from synapse.http.server import HttpServer
 from synapse.http.servlet import (
     RestServlet,
     parse_integer,
     parse_json_object_from_request,
     parse_string,
 )
+from synapse.http.site import SynapseRequest
 from synapse.rest.client.transactions import HttpTransactionCache
 from synapse.storage.relations import (
     AggregationPaginationToken,
     PaginationChunk,
     RelationPaginationToken,
 )
+from synapse.types import JsonDict
 from synapse.util.stringutils import random_string
 
 from ._base import client_patterns
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 
@@ -59,13 +66,13 @@ class RelationSendServlet(RestServlet):
         "/(?P<parent_id>[^/]*)/(?P<relation_type>[^/]*)/(?P<event_type>[^/]*)"
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.event_creation_handler = hs.get_event_creation_handler()
         self.txns = HttpTransactionCache(hs)
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         http_server.register_paths(
             "POST",
             client_patterns(self.PATTERN + "$", releases=()),
@@ -79,14 +86,35 @@ class RelationSendServlet(RestServlet):
             self.__class__.__name__,
         )
 
-    def on_PUT(self, request, *args, **kwargs):
+    def on_PUT(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        parent_id: str,
+        relation_type: str,
+        event_type: str,
+        txn_id: Optional[str] = None,
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         return self.txns.fetch_or_execute_request(
-            request, self.on_PUT_or_POST, request, *args, **kwargs
+            request,
+            self.on_PUT_or_POST,
+            request,
+            room_id,
+            parent_id,
+            relation_type,
+            event_type,
+            txn_id,
         )
 
     async def on_PUT_or_POST(
-        self, request, room_id, parent_id, relation_type, event_type, txn_id=None
-    ):
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        parent_id: str,
+        relation_type: str,
+        event_type: str,
+        txn_id: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         if event_type == EventTypes.Member:
@@ -136,7 +164,7 @@ class RelationPaginationServlet(RestServlet):
         releases=(),
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
@@ -145,8 +173,13 @@ class RelationPaginationServlet(RestServlet):
         self.event_handler = hs.get_event_handler()
 
     async def on_GET(
-        self, request, room_id, parent_id, relation_type=None, event_type=None
-    ):
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        parent_id: str,
+        relation_type: Optional[str] = None,
+        event_type: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         await self.auth.check_user_in_room_or_world_readable(
@@ -156,6 +189,8 @@ class RelationPaginationServlet(RestServlet):
         # This gets the original event and checks that a) the event exists and
         # b) the user is allowed to view it.
         event = await self.event_handler.get_event(requester.user, room_id, parent_id)
+        if event is None:
+            raise SynapseError(404, "Unknown parent event.")
 
         limit = parse_integer(request, "limit", default=5)
         from_token_str = parse_string(request, "from")
@@ -233,15 +268,20 @@ class RelationAggregationPaginationServlet(RestServlet):
         releases=(),
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
         self.event_handler = hs.get_event_handler()
 
     async def on_GET(
-        self, request, room_id, parent_id, relation_type=None, event_type=None
-    ):
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        parent_id: str,
+        relation_type: Optional[str] = None,
+        event_type: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         await self.auth.check_user_in_room_or_world_readable(
@@ -253,6 +293,8 @@ class RelationAggregationPaginationServlet(RestServlet):
         # This checks that a) the event exists and b) the user is allowed to
         # view it.
         event = await self.event_handler.get_event(requester.user, room_id, parent_id)
+        if event is None:
+            raise SynapseError(404, "Unknown parent event.")
 
         if relation_type not in (RelationTypes.ANNOTATION, None):
             raise SynapseError(400, "Relation type must be 'annotation'")
@@ -315,7 +357,7 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
         releases=(),
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
@@ -323,7 +365,15 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
         self._event_serializer = hs.get_event_client_serializer()
         self.event_handler = hs.get_event_handler()
 
-    async def on_GET(self, request, room_id, parent_id, relation_type, event_type, key):
+    async def on_GET(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        parent_id: str,
+        relation_type: str,
+        event_type: str,
+        key: str,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         await self.auth.check_user_in_room_or_world_readable(
@@ -374,7 +424,7 @@ class RelationAggregationGroupPaginationServlet(RestServlet):
         return 200, return_value
 
 
-def register_servlets(hs, http_server):
+def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     RelationSendServlet(hs).register(http_server)
     RelationPaginationServlet(hs).register(http_server)
     RelationAggregationPaginationServlet(hs).register(http_server)
diff --git a/synapse/rest/client/room.py b/synapse/rest/client/room.py
index c5c54564be..9b0c546505 100644
--- a/synapse/rest/client/room.py
+++ b/synapse/rest/client/room.py
@@ -16,9 +16,11 @@
 """ This module contains REST servlets to do with rooms: /rooms/<paths> """
 import logging
 import re
-from typing import TYPE_CHECKING, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Awaitable, Dict, List, Optional, Tuple
 from urllib import parse as urlparse
 
+from twisted.web.server import Request
+
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import (
     AuthError,
@@ -30,6 +32,7 @@ from synapse.api.errors import (
 )
 from synapse.api.filtering import Filter
 from synapse.events.utils import format_event_for_client_v2
+from synapse.http.server import HttpServer
 from synapse.http.servlet import (
     ResolveRoomIdMixin,
     RestServlet,
@@ -57,7 +60,7 @@ logger = logging.getLogger(__name__)
 
 
 class TransactionRestServlet(RestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.txns = HttpTransactionCache(hs)
 
@@ -65,20 +68,22 @@ class TransactionRestServlet(RestServlet):
 class RoomCreateRestServlet(TransactionRestServlet):
     # No PATTERN; we have custom dispatch rules here
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self._room_creation_handler = hs.get_room_creation_handler()
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         PATTERNS = "/createRoom"
         register_txn_path(self, PATTERNS, http_server)
 
-    def on_PUT(self, request, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
         return self.txns.fetch_or_execute_request(request, self.on_POST, request)
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         info, _ = await self._room_creation_handler.create_room(
@@ -87,21 +92,21 @@ class RoomCreateRestServlet(TransactionRestServlet):
 
         return 200, info
 
-    def get_room_config(self, request):
+    def get_room_config(self, request: Request) -> JsonDict:
         user_supplied_config = parse_json_object_from_request(request)
         return user_supplied_config
 
 
 # TODO: Needs unit testing for generic events
 class RoomStateEventRestServlet(TransactionRestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.event_creation_handler = hs.get_event_creation_handler()
         self.room_member_handler = hs.get_room_member_handler()
         self.message_handler = hs.get_message_handler()
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         # /room/$roomid/state/$eventtype
         no_state_key = "/rooms/(?P<room_id>[^/]*)/state/(?P<event_type>[^/]*)$"
 
@@ -136,13 +141,19 @@ class RoomStateEventRestServlet(TransactionRestServlet):
             self.__class__.__name__,
         )
 
-    def on_GET_no_state_key(self, request, room_id, event_type):
+    def on_GET_no_state_key(
+        self, request: SynapseRequest, room_id: str, event_type: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         return self.on_GET(request, room_id, event_type, "")
 
-    def on_PUT_no_state_key(self, request, room_id, event_type):
+    def on_PUT_no_state_key(
+        self, request: SynapseRequest, room_id: str, event_type: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         return self.on_PUT(request, room_id, event_type, "")
 
-    async def on_GET(self, request, room_id, event_type, state_key):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str, event_type: str, state_key: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         format = parse_string(
             request, "format", default="content", allowed_values=["content", "event"]
@@ -165,7 +176,17 @@ class RoomStateEventRestServlet(TransactionRestServlet):
         elif format == "content":
             return 200, data.get_dict()["content"]
 
-    async def on_PUT(self, request, room_id, event_type, state_key, txn_id=None):
+        # Format must be event or content, per the parse_string call above.
+        raise RuntimeError(f"Unknown format: {format:r}.")
+
+    async def on_PUT(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        event_type: str,
+        state_key: str,
+        txn_id: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         if txn_id:
@@ -211,27 +232,35 @@ class RoomStateEventRestServlet(TransactionRestServlet):
 
 # TODO: Needs unit testing for generic events + feedback
 class RoomSendEventRestServlet(TransactionRestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.event_creation_handler = hs.get_event_creation_handler()
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         # /rooms/$roomid/send/$event_type[/$txn_id]
         PATTERNS = "/rooms/(?P<room_id>[^/]*)/send/(?P<event_type>[^/]*)"
         register_txn_path(self, PATTERNS, http_server, with_get=True)
 
-    async def on_POST(self, request, room_id, event_type, txn_id=None):
+    async def on_POST(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        event_type: str,
+        txn_id: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         content = parse_json_object_from_request(request)
 
-        event_dict = {
+        event_dict: JsonDict = {
             "type": event_type,
             "content": content,
             "room_id": room_id,
             "sender": requester.user.to_string(),
         }
 
+        # Twisted will have processed the args by now.
+        assert request.args is not None
         if b"ts" in request.args and requester.app_service:
             event_dict["origin_server_ts"] = parse_integer(request, "ts", 0)
 
@@ -249,10 +278,14 @@ class RoomSendEventRestServlet(TransactionRestServlet):
         set_tag("event_id", event_id)
         return 200, {"event_id": event_id}
 
-    def on_GET(self, request, room_id, event_type, txn_id):
+    def on_GET(
+        self, request: SynapseRequest, room_id: str, event_type: str, txn_id: str
+    ) -> Tuple[int, str]:
         return 200, "Not implemented"
 
-    def on_PUT(self, request, room_id, event_type, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, room_id: str, event_type: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
 
         return self.txns.fetch_or_execute_request(
@@ -262,12 +295,12 @@ class RoomSendEventRestServlet(TransactionRestServlet):
 
 # TODO: Needs unit testing for room ID + alias joins
 class JoinRoomAliasServlet(ResolveRoomIdMixin, TransactionRestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         super(ResolveRoomIdMixin, self).__init__(hs)  # ensure the Mixin is set up
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         # /join/$room_identifier[/$txn_id]
         PATTERNS = "/join/(?P<room_identifier>[^/]*)"
         register_txn_path(self, PATTERNS, http_server)
@@ -277,7 +310,7 @@ class JoinRoomAliasServlet(ResolveRoomIdMixin, TransactionRestServlet):
         request: SynapseRequest,
         room_identifier: str,
         txn_id: Optional[str] = None,
-    ):
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         try:
@@ -308,7 +341,9 @@ class JoinRoomAliasServlet(ResolveRoomIdMixin, TransactionRestServlet):
 
         return 200, {"room_id": room_id}
 
-    def on_PUT(self, request, room_identifier, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, room_identifier: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
 
         return self.txns.fetch_or_execute_request(
@@ -320,12 +355,12 @@ class JoinRoomAliasServlet(ResolveRoomIdMixin, TransactionRestServlet):
 class PublicRoomListRestServlet(TransactionRestServlet):
     PATTERNS = client_patterns("/publicRooms$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.hs = hs
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         server = parse_string(request, "server")
 
         try:
@@ -374,7 +409,7 @@ class PublicRoomListRestServlet(TransactionRestServlet):
 
         return 200, data
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         await self.auth.get_user_by_req(request, allow_guest=True)
 
         server = parse_string(request, "server")
@@ -438,13 +473,15 @@ class PublicRoomListRestServlet(TransactionRestServlet):
 class RoomMemberListRestServlet(RestServlet):
     PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/members$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.message_handler = hs.get_message_handler()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
 
-    async def on_GET(self, request, room_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
         # TODO support Pagination stream API (limit/tokens)
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         handler = self.message_handler
@@ -490,12 +527,14 @@ class RoomMemberListRestServlet(RestServlet):
 class JoinedRoomMemberListRestServlet(RestServlet):
     PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/joined_members$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.message_handler = hs.get_message_handler()
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request, room_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         users_with_profile = await self.message_handler.get_joined_members(
@@ -509,17 +548,21 @@ class JoinedRoomMemberListRestServlet(RestServlet):
 class RoomMessageListRestServlet(RestServlet):
     PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/messages$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.pagination_handler = hs.get_pagination_handler()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
 
-    async def on_GET(self, request, room_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         pagination_config = await PaginationConfig.from_request(
             self.store, request, default_limit=10
         )
+        # Twisted will have processed the args by now.
+        assert request.args is not None
         as_client_event = b"raw" not in request.args
         filter_str = parse_string(request, "filter", encoding="utf-8")
         if filter_str:
@@ -549,12 +592,14 @@ class RoomMessageListRestServlet(RestServlet):
 class RoomStateRestServlet(RestServlet):
     PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/state$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.message_handler = hs.get_message_handler()
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request, room_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, List[JsonDict]]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         # Get all the current state for this room
         events = await self.message_handler.get_state_events(
@@ -569,13 +614,15 @@ class RoomStateRestServlet(RestServlet):
 class RoomInitialSyncRestServlet(RestServlet):
     PATTERNS = client_patterns("/rooms/(?P<room_id>[^/]*)/initialSync$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.initial_sync_handler = hs.get_initial_sync_handler()
         self.auth = hs.get_auth()
         self.store = hs.get_datastore()
 
-    async def on_GET(self, request, room_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         pagination_config = await PaginationConfig.from_request(self.store, request)
         content = await self.initial_sync_handler.room_initial_sync(
@@ -589,14 +636,16 @@ class RoomEventServlet(RestServlet):
         "/rooms/(?P<room_id>[^/]*)/event/(?P<event_id>[^/]*)$", v1=True
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.clock = hs.get_clock()
         self.event_handler = hs.get_event_handler()
         self._event_serializer = hs.get_event_client_serializer()
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request, room_id, event_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str, event_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
         try:
             event = await self.event_handler.get_event(
@@ -610,10 +659,10 @@ class RoomEventServlet(RestServlet):
 
         time_now = self.clock.time_msec()
         if event:
-            event = await self._event_serializer.serialize_event(event, time_now)
-            return 200, event
+            event_dict = await self._event_serializer.serialize_event(event, time_now)
+            return 200, event_dict
 
-        return SynapseError(404, "Event not found.", errcode=Codes.NOT_FOUND)
+        raise SynapseError(404, "Event not found.", errcode=Codes.NOT_FOUND)
 
 
 class RoomEventContextServlet(RestServlet):
@@ -621,14 +670,16 @@ class RoomEventContextServlet(RestServlet):
         "/rooms/(?P<room_id>[^/]*)/context/(?P<event_id>[^/]*)$", v1=True
     )
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.clock = hs.get_clock()
         self.room_context_handler = hs.get_room_context_handler()
         self._event_serializer = hs.get_event_client_serializer()
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request, room_id, event_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str, event_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         limit = parse_integer(request, "limit", default=10)
@@ -669,23 +720,27 @@ class RoomEventContextServlet(RestServlet):
 
 
 class RoomForgetRestServlet(TransactionRestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.room_member_handler = hs.get_room_member_handler()
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         PATTERNS = "/rooms/(?P<room_id>[^/]*)/forget"
         register_txn_path(self, PATTERNS, http_server)
 
-    async def on_POST(self, request, room_id, txn_id=None):
+    async def on_POST(
+        self, request: SynapseRequest, room_id: str, txn_id: Optional[str] = None
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=False)
 
         await self.room_member_handler.forget(user=requester.user, room_id=room_id)
 
         return 200, {}
 
-    def on_PUT(self, request, room_id, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, room_id: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
 
         return self.txns.fetch_or_execute_request(
@@ -695,12 +750,12 @@ class RoomForgetRestServlet(TransactionRestServlet):
 
 # TODO: Needs unit testing
 class RoomMembershipRestServlet(TransactionRestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.room_member_handler = hs.get_room_member_handler()
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         # /rooms/$roomid/[invite|join|leave]
         PATTERNS = (
             "/rooms/(?P<room_id>[^/]*)/"
@@ -708,7 +763,13 @@ class RoomMembershipRestServlet(TransactionRestServlet):
         )
         register_txn_path(self, PATTERNS, http_server)
 
-    async def on_POST(self, request, room_id, membership_action, txn_id=None):
+    async def on_POST(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        membership_action: str,
+        txn_id: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         if requester.is_guest and membership_action not in {
@@ -771,13 +832,15 @@ class RoomMembershipRestServlet(TransactionRestServlet):
 
         return 200, return_value
 
-    def _has_3pid_invite_keys(self, content):
+    def _has_3pid_invite_keys(self, content: JsonDict) -> bool:
         for key in {"id_server", "medium", "address"}:
             if key not in content:
                 return False
         return True
 
-    def on_PUT(self, request, room_id, membership_action, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, room_id: str, membership_action: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
 
         return self.txns.fetch_or_execute_request(
@@ -786,16 +849,22 @@ class RoomMembershipRestServlet(TransactionRestServlet):
 
 
 class RoomRedactEventRestServlet(TransactionRestServlet):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
         self.event_creation_handler = hs.get_event_creation_handler()
         self.auth = hs.get_auth()
 
-    def register(self, http_server):
+    def register(self, http_server: HttpServer) -> None:
         PATTERNS = "/rooms/(?P<room_id>[^/]*)/redact/(?P<event_id>[^/]*)"
         register_txn_path(self, PATTERNS, http_server)
 
-    async def on_POST(self, request, room_id, event_id, txn_id=None):
+    async def on_POST(
+        self,
+        request: SynapseRequest,
+        room_id: str,
+        event_id: str,
+        txn_id: Optional[str] = None,
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
         content = parse_json_object_from_request(request)
 
@@ -821,7 +890,9 @@ class RoomRedactEventRestServlet(TransactionRestServlet):
         set_tag("event_id", event_id)
         return 200, {"event_id": event_id}
 
-    def on_PUT(self, request, room_id, event_id, txn_id):
+    def on_PUT(
+        self, request: SynapseRequest, room_id: str, event_id: str, txn_id: str
+    ) -> Awaitable[Tuple[int, JsonDict]]:
         set_tag("txn_id", txn_id)
 
         return self.txns.fetch_or_execute_request(
@@ -846,7 +917,9 @@ class RoomTypingRestServlet(RestServlet):
             hs.config.worker.writers.typing == hs.get_instance_name()
         )
 
-    async def on_PUT(self, request, room_id, user_id):
+    async def on_PUT(
+        self, request: SynapseRequest, room_id: str, user_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         if not self._is_typing_writer:
@@ -897,7 +970,9 @@ class RoomAliasListServlet(RestServlet):
         self.auth = hs.get_auth()
         self.directory_handler = hs.get_directory_handler()
 
-    async def on_GET(self, request, room_id):
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         alias_list = await self.directory_handler.get_aliases_for_room(
@@ -910,12 +985,12 @@ class RoomAliasListServlet(RestServlet):
 class SearchRestServlet(RestServlet):
     PATTERNS = client_patterns("/search$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.search_handler = hs.get_search_handler()
         self.auth = hs.get_auth()
 
-    async def on_POST(self, request):
+    async def on_POST(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request)
 
         content = parse_json_object_from_request(request)
@@ -929,19 +1004,24 @@ class SearchRestServlet(RestServlet):
 class JoinedRoomsRestServlet(RestServlet):
     PATTERNS = client_patterns("/joined_rooms$", v1=True)
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__()
         self.store = hs.get_datastore()
         self.auth = hs.get_auth()
 
-    async def on_GET(self, request):
+    async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
         requester = await self.auth.get_user_by_req(request, allow_guest=True)
 
         room_ids = await self.store.get_rooms_for_user(requester.user.to_string())
         return 200, {"joined_rooms": list(room_ids)}
 
 
-def register_txn_path(servlet, regex_string, http_server, with_get=False):
+def register_txn_path(
+    servlet: RestServlet,
+    regex_string: str,
+    http_server: HttpServer,
+    with_get: bool = False,
+) -> None:
     """Registers a transaction-based path.
 
     This registers two paths:
@@ -949,28 +1029,37 @@ def register_txn_path(servlet, regex_string, http_server, with_get=False):
         POST regex_string
 
     Args:
-        regex_string (str): The regex string to register. Must NOT have a
-        trailing $ as this string will be appended to.
-        http_server : The http_server to register paths with.
+        regex_string: The regex string to register. Must NOT have a
+            trailing $ as this string will be appended to.
+        http_server: The http_server to register paths with.
         with_get: True to also register respective GET paths for the PUTs.
     """
+    on_POST = getattr(servlet, "on_POST", None)
+    on_PUT = getattr(servlet, "on_PUT", None)
+    if on_POST is None or on_PUT is None:
+        raise RuntimeError("on_POST and on_PUT must exist when using register_txn_path")
     http_server.register_paths(
         "POST",
         client_patterns(regex_string + "$", v1=True),
-        servlet.on_POST,
+        on_POST,
         servlet.__class__.__name__,
     )
     http_server.register_paths(
         "PUT",
         client_patterns(regex_string + "/(?P<txn_id>[^/]*)$", v1=True),
-        servlet.on_PUT,
+        on_PUT,
         servlet.__class__.__name__,
     )
+    on_GET = getattr(servlet, "on_GET", None)
     if with_get:
+        if on_GET is None:
+            raise RuntimeError(
+                "register_txn_path called with with_get = True, but no on_GET method exists"
+            )
         http_server.register_paths(
             "GET",
             client_patterns(regex_string + "/(?P<txn_id>[^/]*)$", v1=True),
-            servlet.on_GET,
+            on_GET,
             servlet.__class__.__name__,
         )
 
@@ -1120,7 +1209,9 @@ class RoomSummaryRestServlet(ResolveRoomIdMixin, RestServlet):
         )
 
 
-def register_servlets(hs: "HomeServer", http_server, is_worker=False):
+def register_servlets(
+    hs: "HomeServer", http_server: HttpServer, is_worker: bool = False
+) -> None:
     RoomStateEventRestServlet(hs).register(http_server)
     RoomMemberListRestServlet(hs).register(http_server)
     JoinedRoomMemberListRestServlet(hs).register(http_server)
@@ -1148,5 +1239,5 @@ def register_servlets(hs: "HomeServer", http_server, is_worker=False):
         RoomForgetRestServlet(hs).register(http_server)
 
 
-def register_deprecated_servlets(hs, http_server):
+def register_deprecated_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
     RoomInitialSyncRestServlet(hs).register(http_server)
diff --git a/synapse/rest/media/v1/oembed.py b/synapse/rest/media/v1/oembed.py
new file mode 100644
index 0000000000..afe41823e4
--- /dev/null
+++ b/synapse/rest/media/v1/oembed.py
@@ -0,0 +1,135 @@
+#  Copyright 2021 The Matrix.org Foundation C.I.C.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+import logging
+from typing import TYPE_CHECKING, Optional
+
+import attr
+
+from synapse.http.client import SimpleHttpClient
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
+logger = logging.getLogger(__name__)
+
+
+@attr.s(slots=True, auto_attribs=True)
+class OEmbedResult:
+    # Either HTML content or URL must be provided.
+    html: Optional[str]
+    url: Optional[str]
+    title: Optional[str]
+    # Number of seconds to cache the content.
+    cache_age: int
+
+
+class OEmbedError(Exception):
+    """An error occurred processing the oEmbed object."""
+
+
+class OEmbedProvider:
+    """
+    A helper for accessing oEmbed content.
+
+    It can be used to check if a URL should be accessed via oEmbed and for
+    requesting/parsing oEmbed content.
+    """
+
+    def __init__(self, hs: "HomeServer", client: SimpleHttpClient):
+        self._oembed_patterns = {}
+        for oembed_endpoint in hs.config.oembed.oembed_patterns:
+            for pattern in oembed_endpoint.url_patterns:
+                self._oembed_patterns[pattern] = oembed_endpoint.api_endpoint
+        self._client = client
+
+    def get_oembed_url(self, url: str) -> Optional[str]:
+        """
+        Check whether the URL should be downloaded as oEmbed content instead.
+
+        Args:
+            url: The URL to check.
+
+        Returns:
+            A URL to use instead or None if the original URL should be used.
+        """
+        for url_pattern, endpoint in self._oembed_patterns.items():
+            if url_pattern.fullmatch(url):
+                return endpoint
+
+        # No match.
+        return None
+
+    async def get_oembed_content(self, endpoint: str, url: str) -> OEmbedResult:
+        """
+        Request content from an oEmbed endpoint.
+
+        Args:
+            endpoint: The oEmbed API endpoint.
+            url: The URL to pass to the API.
+
+        Returns:
+            An object representing the metadata returned.
+
+        Raises:
+            OEmbedError if fetching or parsing of the oEmbed information fails.
+        """
+        try:
+            logger.debug("Trying to get oEmbed content for url '%s'", url)
+            result = await self._client.get_json(
+                endpoint,
+                # TODO Specify max height / width.
+                # Note that only the JSON format is supported.
+                args={"url": url},
+            )
+
+            # Ensure there's a version of 1.0.
+            if result.get("version") != "1.0":
+                raise OEmbedError("Invalid version: %s" % (result.get("version"),))
+
+            oembed_type = result.get("type")
+
+            # Ensure the cache age is None or an int.
+            cache_age = result.get("cache_age")
+            if cache_age:
+                cache_age = int(cache_age)
+
+            oembed_result = OEmbedResult(None, None, result.get("title"), cache_age)
+
+            # HTML content.
+            if oembed_type == "rich":
+                oembed_result.html = result.get("html")
+                return oembed_result
+
+            if oembed_type == "photo":
+                oembed_result.url = result.get("url")
+                return oembed_result
+
+            # TODO Handle link and video types.
+
+            if "thumbnail_url" in result:
+                oembed_result.url = result.get("thumbnail_url")
+                return oembed_result
+
+            raise OEmbedError("Incompatible oEmbed information.")
+
+        except OEmbedError as e:
+            # Trap OEmbedErrors first so we can directly re-raise them.
+            logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
+            raise
+
+        except Exception as e:
+            # Trap any exception and let the code follow as usual.
+            # FIXME: pass through 404s and other error messages nicely
+            logger.warning("Error downloading oEmbed metadata from %s: %r", url, e)
+            raise OEmbedError() from e
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index 0f051d4041..317d333b12 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -25,8 +25,6 @@ import traceback
 from typing import TYPE_CHECKING, Any, Dict, Generator, Iterable, Optional, Union
 from urllib import parse as urlparse
 
-import attr
-
 from twisted.internet.error import DNSLookupError
 from twisted.web.server import Request
 
@@ -43,6 +41,7 @@ from synapse.logging.context import make_deferred_yieldable, run_in_background
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.rest.media.v1._base import get_filename_from_headers
 from synapse.rest.media.v1.media_storage import MediaStorage
+from synapse.rest.media.v1.oembed import OEmbedError, OEmbedProvider
 from synapse.util import json_encoder
 from synapse.util.async_helpers import ObservableDeferred
 from synapse.util.caches.expiringcache import ExpiringCache
@@ -71,63 +70,6 @@ OG_TAG_VALUE_MAXLEN = 1000
 
 ONE_HOUR = 60 * 60 * 1000
 
-# A map of globs to API endpoints.
-_oembed_globs = {
-    # Twitter.
-    "https://publish.twitter.com/oembed": [
-        "https://twitter.com/*/status/*",
-        "https://*.twitter.com/*/status/*",
-        "https://twitter.com/*/moments/*",
-        "https://*.twitter.com/*/moments/*",
-        # Include the HTTP versions too.
-        "http://twitter.com/*/status/*",
-        "http://*.twitter.com/*/status/*",
-        "http://twitter.com/*/moments/*",
-        "http://*.twitter.com/*/moments/*",
-    ],
-}
-# Convert the globs to regular expressions.
-_oembed_patterns = {}
-for endpoint, globs in _oembed_globs.items():
-    for glob in globs:
-        # Convert the glob into a sane regular expression to match against. The
-        # rules followed will be slightly different for the domain portion vs.
-        # the rest.
-        #
-        # 1. The scheme must be one of HTTP / HTTPS (and have no globs).
-        # 2. The domain can have globs, but we limit it to characters that can
-        #    reasonably be a domain part.
-        #    TODO: This does not attempt to handle Unicode domain names.
-        # 3. Other parts allow a glob to be any one, or more, characters.
-        results = urlparse.urlparse(glob)
-
-        # Ensure the scheme does not have wildcards (and is a sane scheme).
-        if results.scheme not in {"http", "https"}:
-            raise ValueError("Insecure oEmbed glob scheme: %s" % (results.scheme,))
-
-        pattern = urlparse.urlunparse(
-            [
-                results.scheme,
-                re.escape(results.netloc).replace("\\*", "[a-zA-Z0-9_-]+"),
-            ]
-            + [re.escape(part).replace("\\*", ".+") for part in results[2:]]
-        )
-        _oembed_patterns[re.compile(pattern)] = endpoint
-
-
-@attr.s(slots=True)
-class OEmbedResult:
-    # Either HTML content or URL must be provided.
-    html = attr.ib(type=Optional[str])
-    url = attr.ib(type=Optional[str])
-    title = attr.ib(type=Optional[str])
-    # Number of seconds to cache the content.
-    cache_age = attr.ib(type=int)
-
-
-class OEmbedError(Exception):
-    """An error occurred processing the oEmbed object."""
-
 
 class PreviewUrlResource(DirectServeJsonResource):
     isLeaf = True
@@ -157,6 +99,8 @@ class PreviewUrlResource(DirectServeJsonResource):
         self.primary_base_path = media_repo.primary_base_path
         self.media_storage = media_storage
 
+        self._oembed = OEmbedProvider(hs, self.client)
+
         # We run the background jobs if we're the instance specified (or no
         # instance is specified, where we assume there is only one instance
         # serving media).
@@ -367,87 +311,6 @@ class PreviewUrlResource(DirectServeJsonResource):
 
         return jsonog.encode("utf8")
 
-    def _get_oembed_url(self, url: str) -> Optional[str]:
-        """
-        Check whether the URL should be downloaded as oEmbed content instead.
-
-        Args:
-            url: The URL to check.
-
-        Returns:
-            A URL to use instead or None if the original URL should be used.
-        """
-        for url_pattern, endpoint in _oembed_patterns.items():
-            if url_pattern.fullmatch(url):
-                return endpoint
-
-        # No match.
-        return None
-
-    async def _get_oembed_content(self, endpoint: str, url: str) -> OEmbedResult:
-        """
-        Request content from an oEmbed endpoint.
-
-        Args:
-            endpoint: The oEmbed API endpoint.
-            url: The URL to pass to the API.
-
-        Returns:
-            An object representing the metadata returned.
-
-        Raises:
-            OEmbedError if fetching or parsing of the oEmbed information fails.
-        """
-        try:
-            logger.debug("Trying to get oEmbed content for url '%s'", url)
-            result = await self.client.get_json(
-                endpoint,
-                # TODO Specify max height / width.
-                # Note that only the JSON format is supported.
-                args={"url": url},
-            )
-
-            # Ensure there's a version of 1.0.
-            if result.get("version") != "1.0":
-                raise OEmbedError("Invalid version: %s" % (result.get("version"),))
-
-            oembed_type = result.get("type")
-
-            # Ensure the cache age is None or an int.
-            cache_age = result.get("cache_age")
-            if cache_age:
-                cache_age = int(cache_age)
-
-            oembed_result = OEmbedResult(None, None, result.get("title"), cache_age)
-
-            # HTML content.
-            if oembed_type == "rich":
-                oembed_result.html = result.get("html")
-                return oembed_result
-
-            if oembed_type == "photo":
-                oembed_result.url = result.get("url")
-                return oembed_result
-
-            # TODO Handle link and video types.
-
-            if "thumbnail_url" in result:
-                oembed_result.url = result.get("thumbnail_url")
-                return oembed_result
-
-            raise OEmbedError("Incompatible oEmbed information.")
-
-        except OEmbedError as e:
-            # Trap OEmbedErrors first so we can directly re-raise them.
-            logger.warning("Error parsing oEmbed metadata from %s: %r", url, e)
-            raise
-
-        except Exception as e:
-            # Trap any exception and let the code follow as usual.
-            # FIXME: pass through 404s and other error messages nicely
-            logger.warning("Error downloading oEmbed metadata from %s: %r", url, e)
-            raise OEmbedError() from e
-
     async def _download_url(self, url: str, user: str) -> Dict[str, Any]:
         # TODO: we should probably honour robots.txt... except in practice
         # we're most likely being explicitly triggered by a human rather than a
@@ -459,11 +322,11 @@ class PreviewUrlResource(DirectServeJsonResource):
 
         # If this URL can be accessed via oEmbed, use that instead.
         url_to_download: Optional[str] = url
-        oembed_url = self._get_oembed_url(url)
+        oembed_url = self._oembed.get_oembed_url(url)
         if oembed_url:
             # The result might be a new URL to download, or it might be HTML content.
             try:
-                oembed_result = await self._get_oembed_content(oembed_url, url)
+                oembed_result = await self._oembed.get_oembed_content(oembed_url, url)
                 if oembed_result.url:
                     url_to_download = oembed_result.url
                 elif oembed_result.html:
diff --git a/tests/push/test_email.py b/tests/push/test_email.py
index c4ba13a6b2..fa8018e5a7 100644
--- a/tests/push/test_email.py
+++ b/tests/push/test_email.py
@@ -11,8 +11,9 @@
 # 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 email.message
 import os
+from typing import Dict, List, Sequence, Tuple
 
 import attr
 import pkg_resources
@@ -70,9 +71,10 @@ class EmailPusherTests(HomeserverTestCase):
         hs = self.setup_test_homeserver(config=config)
 
         # List[Tuple[Deferred, args, kwargs]]
-        self.email_attempts = []
+        self.email_attempts: List[Tuple[Deferred, Sequence, Dict]] = []
 
         def sendmail(*args, **kwargs):
+            # This mocks out synapse.reactor.send_email._sendmail.
             d = Deferred()
             self.email_attempts.append((d, args, kwargs))
             return d
@@ -255,6 +257,39 @@ class EmailPusherTests(HomeserverTestCase):
         # We should get emailed about those messages
         self._check_for_mail()
 
+    def test_room_notifications_include_avatar(self):
+        # Create a room and set its avatar.
+        room = self.helper.create_room_as(self.user_id, tok=self.access_token)
+        self.helper.send_state(
+            room, "m.room.avatar", {"url": "mxc://DUMMY_MEDIA_ID"}, self.access_token
+        )
+
+        # Invite two other uses.
+        for other in self.others:
+            self.helper.invite(
+                room=room, src=self.user_id, tok=self.access_token, targ=other.id
+            )
+            self.helper.join(room=room, user=other.id, tok=other.token)
+
+        # The other users send some messages.
+        # TODO It seems that two messages are required to trigger an email?
+        self.helper.send(room, body="Alpha", tok=self.others[0].token)
+        self.helper.send(room, body="Beta", tok=self.others[1].token)
+
+        # We should get emailed about those messages
+        args, kwargs = self._check_for_mail()
+
+        # That email should contain the room's avatar
+        msg: bytes = args[5]
+        # Multipart: plain text, base 64 encoded; html, base 64 encoded
+        html = (
+            email.message_from_bytes(msg)
+            .get_payload()[1]
+            .get_payload(decode=True)
+            .decode()
+        )
+        self.assertIn("_matrix/media/v1/thumbnail/DUMMY_MEDIA_ID", html)
+
     def test_empty_room(self):
         """All users leaving a room shouldn't cause the pusher to break."""
         # Create a simple room with two users
@@ -388,9 +423,14 @@ class EmailPusherTests(HomeserverTestCase):
         pushers = list(pushers)
         self.assertEqual(len(pushers), 0)
 
-    def _check_for_mail(self):
-        """Check that the user receives an email notification"""
+    def _check_for_mail(self) -> Tuple[Sequence, Dict]:
+        """
+        Assert that synapse sent off exactly one email notification.
 
+        Returns:
+            args and kwargs passed to synapse.reactor.send_email._sendmail for
+            that notification.
+        """
         # Get the stream ordering before it gets sent
         pushers = self.get_success(
             self.hs.get_datastore().get_pushers_by({"user_name": self.user_id})
@@ -413,8 +453,9 @@ class EmailPusherTests(HomeserverTestCase):
         # One email was attempted to be sent
         self.assertEqual(len(self.email_attempts), 1)
 
+        deferred, sendmail_args, sendmail_kwargs = self.email_attempts[0]
         # Make the email succeed
-        self.email_attempts[0][0].callback(True)
+        deferred.callback(True)
         self.pump()
 
         # One email was attempted to be sent
@@ -430,3 +471,4 @@ class EmailPusherTests(HomeserverTestCase):
 
         # Reset the attempts.
         self.email_attempts = []
+        return sendmail_args, sendmail_kwargs
diff --git a/tests/rest/media/v1/test_url_preview.py b/tests/rest/media/v1/test_url_preview.py
index d3ef7bb4c6..7fa9027227 100644
--- a/tests/rest/media/v1/test_url_preview.py
+++ b/tests/rest/media/v1/test_url_preview.py
@@ -14,13 +14,14 @@
 import json
 import os
 import re
-from unittest.mock import patch
 
 from twisted.internet._resolver import HostResolution
 from twisted.internet.address import IPv4Address, IPv6Address
 from twisted.internet.error import DNSLookupError
 from twisted.test.proto_helpers import AccumulatingProtocol
 
+from synapse.config.oembed import OEmbedEndpointConfig
+
 from tests import unittest
 from tests.server import FakeTransport
 
@@ -81,6 +82,19 @@ class URLPreviewTests(unittest.HomeserverTestCase):
 
         hs = self.setup_test_homeserver(config=config)
 
+        # After the hs is created, modify the parsed oEmbed config (to avoid
+        # messing with files).
+        #
+        # Note that HTTP URLs are used to avoid having to deal with TLS in tests.
+        hs.config.oembed.oembed_patterns = [
+            OEmbedEndpointConfig(
+                api_endpoint="http://publish.twitter.com/oembed",
+                url_patterns=[
+                    re.compile(r"http://twitter\.com/.+/status/.+"),
+                ],
+            )
+        ]
+
         return hs
 
     def prepare(self, reactor, clock, hs):
@@ -544,123 +558,101 @@ class URLPreviewTests(unittest.HomeserverTestCase):
 
     def test_oembed_photo(self):
         """Test an oEmbed endpoint which returns a 'photo' type which redirects the preview to a new URL."""
-        # Route the HTTP version to an HTTP endpoint so that the tests work.
-        with patch.dict(
-            "synapse.rest.media.v1.preview_url_resource._oembed_patterns",
-            {
-                re.compile(
-                    r"http://twitter\.com/.+/status/.+"
-                ): "http://publish.twitter.com/oembed",
-            },
-            clear=True,
-        ):
-
-            self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
-            self.lookups["cdn.twitter.com"] = [(IPv4Address, "10.1.2.3")]
-
-            result = {
-                "version": "1.0",
-                "type": "photo",
-                "url": "http://cdn.twitter.com/matrixdotorg",
-            }
-            oembed_content = json.dumps(result).encode("utf-8")
-
-            end_content = (
-                b"<html><head>"
-                b"<title>Some Title</title>"
-                b'<meta property="og:description" content="hi" />'
-                b"</head></html>"
-            )
+        self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
+        self.lookups["cdn.twitter.com"] = [(IPv4Address, "10.1.2.3")]
 
-            channel = self.make_request(
-                "GET",
-                "preview_url?url=http://twitter.com/matrixdotorg/status/12345",
-                shorthand=False,
-                await_result=False,
-            )
-            self.pump()
-
-            client = self.reactor.tcpClients[0][2].buildProtocol(None)
-            server = AccumulatingProtocol()
-            server.makeConnection(FakeTransport(client, self.reactor))
-            client.makeConnection(FakeTransport(server, self.reactor))
-            client.dataReceived(
-                (
-                    b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
-                    b'Content-Type: application/json; charset="utf8"\r\n\r\n'
-                )
-                % (len(oembed_content),)
-                + oembed_content
-            )
+        result = {
+            "version": "1.0",
+            "type": "photo",
+            "url": "http://cdn.twitter.com/matrixdotorg",
+        }
+        oembed_content = json.dumps(result).encode("utf-8")
 
-            self.pump()
-
-            client = self.reactor.tcpClients[1][2].buildProtocol(None)
-            server = AccumulatingProtocol()
-            server.makeConnection(FakeTransport(client, self.reactor))
-            client.makeConnection(FakeTransport(server, self.reactor))
-            client.dataReceived(
-                (
-                    b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
-                    b'Content-Type: text/html; charset="utf8"\r\n\r\n'
-                )
-                % (len(end_content),)
-                + end_content
+        end_content = (
+            b"<html><head>"
+            b"<title>Some Title</title>"
+            b'<meta property="og:description" content="hi" />'
+            b"</head></html>"
+        )
+
+        channel = self.make_request(
+            "GET",
+            "preview_url?url=http://twitter.com/matrixdotorg/status/12345",
+            shorthand=False,
+            await_result=False,
+        )
+        self.pump()
+
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b'Content-Type: application/json; charset="utf8"\r\n\r\n'
             )
+            % (len(oembed_content),)
+            + oembed_content
+        )
 
-            self.pump()
+        self.pump()
 
-            self.assertEqual(channel.code, 200)
-            self.assertEqual(
-                channel.json_body, {"og:title": "Some Title", "og:description": "hi"}
+        client = self.reactor.tcpClients[1][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b'Content-Type: text/html; charset="utf8"\r\n\r\n'
             )
+            % (len(end_content),)
+            + end_content
+        )
+
+        self.pump()
+
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            channel.json_body, {"og:title": "Some Title", "og:description": "hi"}
+        )
 
     def test_oembed_rich(self):
         """Test an oEmbed endpoint which returns HTML content via the 'rich' type."""
-        # Route the HTTP version to an HTTP endpoint so that the tests work.
-        with patch.dict(
-            "synapse.rest.media.v1.preview_url_resource._oembed_patterns",
-            {
-                re.compile(
-                    r"http://twitter\.com/.+/status/.+"
-                ): "http://publish.twitter.com/oembed",
-            },
-            clear=True,
-        ):
-
-            self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
-
-            result = {
-                "version": "1.0",
-                "type": "rich",
-                "html": "<div>Content Preview</div>",
-            }
-            end_content = json.dumps(result).encode("utf-8")
-
-            channel = self.make_request(
-                "GET",
-                "preview_url?url=http://twitter.com/matrixdotorg/status/12345",
-                shorthand=False,
-                await_result=False,
-            )
-            self.pump()
-
-            client = self.reactor.tcpClients[0][2].buildProtocol(None)
-            server = AccumulatingProtocol()
-            server.makeConnection(FakeTransport(client, self.reactor))
-            client.makeConnection(FakeTransport(server, self.reactor))
-            client.dataReceived(
-                (
-                    b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
-                    b'Content-Type: application/json; charset="utf8"\r\n\r\n'
-                )
-                % (len(end_content),)
-                + end_content
-            )
+        self.lookups["publish.twitter.com"] = [(IPv4Address, "10.1.2.3")]
+
+        result = {
+            "version": "1.0",
+            "type": "rich",
+            "html": "<div>Content Preview</div>",
+        }
+        end_content = json.dumps(result).encode("utf-8")
+
+        channel = self.make_request(
+            "GET",
+            "preview_url?url=http://twitter.com/matrixdotorg/status/12345",
+            shorthand=False,
+            await_result=False,
+        )
+        self.pump()
 
-            self.pump()
-            self.assertEqual(channel.code, 200)
-            self.assertEqual(
-                channel.json_body,
-                {"og:title": None, "og:description": "Content Preview"},
+        client = self.reactor.tcpClients[0][2].buildProtocol(None)
+        server = AccumulatingProtocol()
+        server.makeConnection(FakeTransport(client, self.reactor))
+        client.makeConnection(FakeTransport(server, self.reactor))
+        client.dataReceived(
+            (
+                b"HTTP/1.0 200 OK\r\nContent-Length: %d\r\n"
+                b'Content-Type: application/json; charset="utf8"\r\n\r\n'
             )
+            % (len(end_content),)
+            + end_content
+        )
+
+        self.pump()
+        self.assertEqual(channel.code, 200)
+        self.assertEqual(
+            channel.json_body,
+            {"og:title": None, "og:description": "Content Preview"},
+        )