Merge pull request #4166 from matrix-org/erikj/drop_unknown_events

Drop incoming events from federation for unknown rooms

changelog.d/4165.misc

@@ -0,0 +1 @@
+Drop incoming events from federation for unknown rooms

synapse/federation/federation_server.py

@@ -162,8 +162,30 @@ class FederationServer(FederationBase):
                 p["age_ts"] = request_time - int(p["age"])
                 del p["age"]
 
+            # We try and pull out an event ID so that if later checks fail we
+            # can log something sensible. We don't mandate an event ID here in
+            # case future event formats get rid of the key.
+            possible_event_id = p.get("event_id", "<Unknown>")
+
+            # Now we get the room ID so that we can check that we know the
+            # version of the room.
+            room_id = p.get("room_id")
+            if not room_id:
+                logger.info(
+                    "Ignoring PDU as does not have a room_id. Event ID: %s",
+                    possible_event_id,
+                )
+                continue
+
+            try:
+                # In future we will actually use the room version to parse the
+                # PDU into an event.
+                yield self.store.get_room_version(room_id)
+            except NotFoundError:
+                logger.info("Ignoring PDU for unknown room_id: %s", room_id)
+                continue
+
             event = event_from_pdu_json(p)
-            room_id = event.room_id
             pdus_by_room.setdefault(room_id, []).append(event)
 
         pdu_results = {}

synapse/handlers/federation.py

@@ -202,24 +202,19 @@ class FederationHandler(BaseHandler):
             self.room_queues[room_id].append((pdu, origin))
             return
 
-        # If we're no longer in the room just ditch the event entirely. This
+        # If we're not in the room just ditch the event entirely. This is
-        # is probably an old server that has come back and thinks we're still
+        # probably an old server that has come back and thinks we're still in
-        # in the room (or we've been rejoined to the room by a state reset).
+        # the room (or we've been rejoined to the room by a state reset).
         #
-        # If we were never in the room then maybe our database got vaped and
+        # Note that if we were never in the room then we would have already
-        # we should check if we *are* in fact in the room. If we are then we
+        # dropped the event, since we wouldn't know the room version.
-        # can magically rejoin the room.
         is_in_room = yield self.auth.check_host_in_room(
             room_id,
             self.server_name
         )
         if not is_in_room:
-            was_in_room = yield self.store.was_host_joined(
-                pdu.room_id, self.server_name,
-            )
-            if was_in_room:
             logger.info(
-                    "[%s %s] Ignoring PDU from %s as we've left the room",
+                "[%s %s] Ignoring PDU from %s as we're not in the room",
                 room_id, event_id, origin,
             )
             defer.returnValue(None)
@@ -557,38 +552,6 @@ class FederationHandler(BaseHandler):
             room_id, event_id, event,
         )
 
-        # FIXME (erikj): Awful hack to make the case where we are not currently
-        # in the room work
-        # If state and auth_chain are None, then we don't need to do this check
-        # as we already know we have enough state in the DB to handle this
-        # event.
-        if state and auth_chain and not event.internal_metadata.is_outlier():
-            is_in_room = yield self.auth.check_host_in_room(
-                room_id,
-                self.server_name
-            )
-        else:
-            is_in_room = True
-
-        if not is_in_room:
-            logger.info(
-                "[%s %s] Got event for room we're not in",
-                room_id, event_id,
-            )
-
-            try:
-                yield self._persist_auth_tree(
-                    origin, auth_chain, state, event
-                )
-            except AuthError as e:
-                raise FederationError(
-                    "ERROR",
-                    e.code,
-                    e.msg,
-                    affected=event_id,
-                )
-
-        else:
         event_ids = set()
         if state:
             event_ids |= {e.event_id for e in state}