diff --git a/changelog.d/10910.feature b/changelog.d/10910.feature
new file mode 100644
index 0000000000..aee139f8b6
--- /dev/null
+++ b/changelog.d/10910.feature
@@ -0,0 +1 @@
+Add a spam checker callback to allow or deny room joins.
diff --git a/docs/modules/spam_checker_callbacks.md b/docs/modules/spam_checker_callbacks.md
index 7920ac5f8f..92376df993 100644
--- a/docs/modules/spam_checker_callbacks.md
+++ b/docs/modules/spam_checker_callbacks.md
@@ -19,6 +19,21 @@ either a `bool` to indicate whether the event must be rejected because of spam,
to indicate the event must be rejected because of spam and to give a rejection reason to
forward to clients.
+### `user_may_join_room`
+
+```python
+async def user_may_join_room(user: str, room: str, is_invited: bool) -> bool
+```
+
+Called when a user is trying to join a room. The module must return a `bool` to indicate
+whether the user can join the room. The user is represented by their Matrix user ID (e.g.
+`@alice:example.com`) and the room is represented by its Matrix ID (e.g.
+`!room:example.com`). The module is also given a boolean to indicate whether the user
+currently has a pending invite in the room.
+
+This callback isn't called if the join is performed by a server administrator, or in the
+context of a room creation.
+
### `user_may_invite`
```python
diff --git a/synapse/events/spamcheck.py b/synapse/events/spamcheck.py
index c389f70b8d..ec8863e397 100644
--- a/synapse/events/spamcheck.py
+++ b/synapse/events/spamcheck.py
@@ -44,6 +44,7 @@ CHECK_EVENT_FOR_SPAM_CALLBACK = Callable[
["synapse.events.EventBase"],
Awaitable[Union[bool, str]],
]
+USER_MAY_JOIN_ROOM_CALLBACK = Callable[[str, str, bool], Awaitable[bool]]
USER_MAY_INVITE_CALLBACK = Callable[[str, str, str], Awaitable[bool]]
USER_MAY_CREATE_ROOM_CALLBACK = Callable[[str], Awaitable[bool]]
USER_MAY_CREATE_ROOM_WITH_INVITES_CALLBACK = Callable[
@@ -165,6 +166,7 @@ def load_legacy_spam_checkers(hs: "synapse.server.HomeServer"):
class SpamChecker:
def __init__(self):
self._check_event_for_spam_callbacks: List[CHECK_EVENT_FOR_SPAM_CALLBACK] = []
+ self._user_may_join_room_callbacks: List[USER_MAY_JOIN_ROOM_CALLBACK] = []
self._user_may_invite_callbacks: List[USER_MAY_INVITE_CALLBACK] = []
self._user_may_create_room_callbacks: List[USER_MAY_CREATE_ROOM_CALLBACK] = []
self._user_may_create_room_with_invites_callbacks: List[
@@ -187,6 +189,7 @@ class SpamChecker:
def register_callbacks(
self,
check_event_for_spam: Optional[CHECK_EVENT_FOR_SPAM_CALLBACK] = None,
+ user_may_join_room: Optional[USER_MAY_JOIN_ROOM_CALLBACK] = None,
user_may_invite: Optional[USER_MAY_INVITE_CALLBACK] = None,
user_may_create_room: Optional[USER_MAY_CREATE_ROOM_CALLBACK] = None,
user_may_create_room_with_invites: Optional[
@@ -206,6 +209,9 @@ class SpamChecker:
if check_event_for_spam is not None:
self._check_event_for_spam_callbacks.append(check_event_for_spam)
+ if user_may_join_room is not None:
+ self._user_may_join_room_callbacks.append(user_may_join_room)
+
if user_may_invite is not None:
self._user_may_invite_callbacks.append(user_may_invite)
@@ -259,6 +265,24 @@ class SpamChecker:
return False
+ async def user_may_join_room(self, user_id: str, room_id: str, is_invited: bool):
+ """Checks if a given users is allowed to join a room.
+ Not called when a user creates a room.
+
+ Args:
+ userid: The ID of the user wanting to join the room
+ room_id: The ID of the room the user wants to join
+ is_invited: Whether the user is invited into the room
+
+ Returns:
+ bool: Whether the user may join the room
+ """
+ for callback in self._user_may_join_room_callbacks:
+ if await callback(user_id, room_id, is_invited) is False:
+ return False
+
+ return True
+
async def user_may_invite(
self, inviter_userid: str, invitee_userid: str, room_id: str
) -> bool:
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 873e08258e..d40dbd761d 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -860,6 +860,7 @@ class RoomCreationHandler(BaseHandler):
"invite",
ratelimit=False,
content=content,
+ new_room=True,
)
for invite_3pid in invite_3pid_list:
@@ -962,6 +963,7 @@ class RoomCreationHandler(BaseHandler):
"join",
ratelimit=ratelimit,
content=creator_join_profile,
+ new_room=True,
)
# We treat the power levels override specially as this needs to be one
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index c8fb24a20c..0b79dbcf8d 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -434,6 +434,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
third_party_signed: Optional[dict] = None,
ratelimit: bool = True,
content: Optional[dict] = None,
+ new_room: bool = False,
require_consent: bool = True,
outlier: bool = False,
prev_event_ids: Optional[List[str]] = None,
@@ -451,6 +452,8 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
third_party_signed: Information from a 3PID invite.
ratelimit: Whether to rate limit the request.
content: The content of the created event.
+ new_room: Whether the membership update is happening in the context of a room
+ creation.
require_consent: Whether consent is required.
outlier: Indicates whether the event is an `outlier`, i.e. if
it's from an arbitrary point and floating in the DAG as
@@ -485,6 +488,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
third_party_signed=third_party_signed,
ratelimit=ratelimit,
content=content,
+ new_room=new_room,
require_consent=require_consent,
outlier=outlier,
prev_event_ids=prev_event_ids,
@@ -504,6 +508,7 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
third_party_signed: Optional[dict] = None,
ratelimit: bool = True,
content: Optional[dict] = None,
+ new_room: bool = False,
require_consent: bool = True,
outlier: bool = False,
prev_event_ids: Optional[List[str]] = None,
@@ -523,6 +528,8 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
third_party_signed:
ratelimit:
content:
+ new_room: Whether the membership update is happening in the context of a room
+ creation.
require_consent:
outlier: Indicates whether the event is an `outlier`, i.e. if
it's from an arbitrary point and floating in the DAG as
@@ -726,6 +733,30 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
# so don't really fit into the general auth process.
raise AuthError(403, "Guest access not allowed")
+ # Figure out whether the user is a server admin to determine whether they
+ # should be able to bypass the spam checker.
+ if (
+ self._server_notices_mxid is not None
+ and requester.user.to_string() == self._server_notices_mxid
+ ):
+ # allow the server notices mxid to join rooms
+ bypass_spam_checker = True
+
+ else:
+ bypass_spam_checker = await self.auth.is_server_admin(requester.user)
+
+ inviter = await self._get_inviter(target.to_string(), room_id)
+ if (
+ not bypass_spam_checker
+ # We assume that if the spam checker allowed the user to create
+ # a room then they're allowed to join it.
+ and not new_room
+ and not await self.spam_checker.user_may_join_room(
+ target.to_string(), room_id, is_invited=inviter is not None
+ )
+ ):
+ raise SynapseError(403, "Not allowed to join this room")
+
# Check if a remote join should be performed.
remote_join, remote_room_hosts = await self._should_perform_remote_join(
target.to_string(), room_id, remote_room_hosts, content, is_host_in_room
diff --git a/tests/rest/client/test_rooms.py b/tests/rest/client/test_rooms.py
index 30bdaa9c27..a41ec6a98f 100644
--- a/tests/rest/client/test_rooms.py
+++ b/tests/rest/client/test_rooms.py
@@ -784,6 +784,30 @@ class RoomsCreateTestCase(RoomBase):
# Check that do_3pid_invite wasn't called this time.
self.assertEquals(do_3pid_invite_mock.call_count, len(invited_3pids))
+ def test_spam_checker_may_join_room(self):
+ """Tests that the user_may_join_room spam checker callback is correctly bypassed
+ when creating a new room.
+ """
+
+ async def user_may_join_room(
+ mxid: str,
+ room_id: str,
+ is_invite: bool,
+ ) -> bool:
+ return False
+
+ join_mock = Mock(side_effect=user_may_join_room)
+ self.hs.get_spam_checker()._user_may_join_room_callbacks.append(join_mock)
+
+ channel = self.make_request(
+ "POST",
+ "/createRoom",
+ {},
+ )
+ self.assertEquals(channel.code, 200, channel.json_body)
+
+ self.assertEquals(join_mock.call_count, 0)
+
class RoomTopicTestCase(RoomBase):
"""Tests /rooms/$room_id/topic REST events."""
@@ -975,6 +999,83 @@ class RoomInviteRatelimitTestCase(RoomBase):
self.helper.invite(room_id, self.user_id, "@other-users:red", expect_code=429)
+class RoomJoinTestCase(RoomBase):
+
+ servlets = [
+ admin.register_servlets,
+ login.register_servlets,
+ room.register_servlets,
+ ]
+
+ def prepare(self, reactor, clock, homeserver):
+ self.user1 = self.register_user("thomas", "hackme")
+ self.tok1 = self.login("thomas", "hackme")
+
+ self.user2 = self.register_user("teresa", "hackme")
+ self.tok2 = self.login("teresa", "hackme")
+
+ self.room1 = self.helper.create_room_as(room_creator=self.user1, tok=self.tok1)
+ self.room2 = self.helper.create_room_as(room_creator=self.user1, tok=self.tok1)
+ self.room3 = self.helper.create_room_as(room_creator=self.user1, tok=self.tok1)
+
+ def test_spam_checker_may_join_room(self):
+ """Tests that the user_may_join_room spam checker callback is correctly called
+ and blocks room joins when needed.
+ """
+
+ # Register a dummy callback. Make it allow all room joins for now.
+ return_value = True
+
+ async def user_may_join_room(
+ userid: str,
+ room_id: str,
+ is_invited: bool,
+ ) -> bool:
+ return return_value
+
+ callback_mock = Mock(side_effect=user_may_join_room)
+ self.hs.get_spam_checker()._user_may_join_room_callbacks.append(callback_mock)
+
+ # Join a first room, without being invited to it.
+ self.helper.join(self.room1, self.user2, tok=self.tok2)
+
+ # Check that the callback was called with the right arguments.
+ expected_call_args = (
+ (
+ self.user2,
+ self.room1,
+ False,
+ ),
+ )
+ self.assertEquals(
+ callback_mock.call_args,
+ expected_call_args,
+ callback_mock.call_args,
+ )
+
+ # Join a second room, this time with an invite for it.
+ self.helper.invite(self.room2, self.user1, self.user2, tok=self.tok1)
+ self.helper.join(self.room2, self.user2, tok=self.tok2)
+
+ # Check that the callback was called with the right arguments.
+ expected_call_args = (
+ (
+ self.user2,
+ self.room2,
+ True,
+ ),
+ )
+ self.assertEquals(
+ callback_mock.call_args,
+ expected_call_args,
+ callback_mock.call_args,
+ )
+
+ # Now make the callback deny all room joins, and check that a join actually fails.
+ return_value = False
+ self.helper.join(self.room3, self.user2, expect_code=403, tok=self.tok2)
+
+
class RoomJoinRatelimitTestCase(RoomBase):
user_id = "@sid1:red"
|
