Allow admins to proactively block rooms (#11228)

Co-authored-by: Dirk Klimpel <5740567+dklimpel@users.noreply.github.com>
Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

1 files changed, 40 insertions, 11 deletions

diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 7a95e31cbe..11af30eee7 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -12,8 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Contains functions for performing events on rooms."""
-
+"""Contains functions for performing actions on rooms."""
 import itertools
 import logging
 import math
@@ -31,6 +30,8 @@ from typing import (
     Tuple,
 )
 
+from typing_extensions import TypedDict
+
 from synapse.api.constants import (
     EventContentFields,
     EventTypes,
@@ -1277,6 +1278,13 @@ class RoomEventSource(EventSource[RoomStreamToken, EventBase]):
         return self.store.get_room_events_max_id(room_id)
 
 
+class ShutdownRoomResponse(TypedDict):
+    kicked_users: List[str]
+    failed_to_kick_users: List[str]
+    local_aliases: List[str]
+    new_room_id: Optional[str]
+
+
 class RoomShutdownHandler:
 
     DEFAULT_MESSAGE = (
@@ -1302,7 +1310,7 @@ class RoomShutdownHandler:
         new_room_name: Optional[str] = None,
         message: Optional[str] = None,
         block: bool = False,
-    ) -> dict:
+    ) -> ShutdownRoomResponse:
         """
         Shuts down a room. Moves all local users and room aliases automatically
         to a new room if `new_room_user_id` is set. Otherwise local users only
@@ -1336,8 +1344,13 @@ class RoomShutdownHandler:
                 Defaults to `Sharing illegal content on this server is not
                 permitted and rooms in violation will be blocked.`
             block:
-                If set to `true`, this room will be added to a blocking list,
-                preventing future attempts to join the room. Defaults to `false`.
+                If set to `True`, users will be prevented from joining the old
+                room. This option can also be used to pre-emptively block a room,
+                even if it's unknown to this homeserver. In this case, the room
+                will be blocked, and no further action will be taken. If `False`,
+                attempting to delete an unknown room is invalid.
+
+                Defaults to `False`.
 
         Returns: a dict containing the following keys:
             kicked_users: An array of users (`user_id`) that were kicked.
@@ -1346,7 +1359,9 @@ class RoomShutdownHandler:
             local_aliases:
                 An array of strings representing the local aliases that were
                 migrated from the old room to the new.
-            new_room_id: A string representing the room ID of the new room.
+            new_room_id:
+                A string representing the room ID of the new room, or None if
+                no such room was created.
         """
 
         if not new_room_name:
@@ -1357,14 +1372,28 @@ class RoomShutdownHandler:
         if not RoomID.is_valid(room_id):
             raise SynapseError(400, "%s is not a legal room ID" % (room_id,))
 
-        if not await self.store.get_room(room_id):
-            raise NotFoundError("Unknown room id %s" % (room_id,))
-
-        # This will work even if the room is already blocked, but that is
-        # desirable in case the first attempt at blocking the room failed below.
+        # Action the block first (even if the room doesn't exist yet)
         if block:
+            # This will work even if the room is already blocked, but that is
+            # desirable in case the first attempt at blocking the room failed below.
             await self.store.block_room(room_id, requester_user_id)
 
+        if not await self.store.get_room(room_id):
+            if block:
+                # We allow you to block an unknown room.
+                return {
+                    "kicked_users": [],
+                    "failed_to_kick_users": [],
+                    "local_aliases": [],
+                    "new_room_id": None,
+                }
+            else:
+                # But if you don't want to preventatively block another room,
+                # this function can't do anything useful.
+                raise NotFoundError(
+                    "Cannot shut down room: unknown room id %s" % (room_id,)
+                )
+
         if new_room_user_id is not None:
             if not self.hs.is_mine_id(new_room_user_id):
                 raise SynapseError(