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Check the room_id of events when fetching room state/auth (#6524)
When we request the state/auth_events to populate a backwards extremity (on backfill or in the case of missing events in a transaction push), we should check that the returned events are in the right room rather than blindly using them in the room state or auth chain. Given that _get_events_from_store_or_dest takes a room_id, it seems clear that it should be sanity-checking the room_id of the requested events, so let's do it there.
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2 changed files with 58 additions and 26 deletions
2
changelog.d/6524.misc
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2
changelog.d/6524.misc
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Improve sanity-checking when receiving events over federation.
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@ -571,7 +571,9 @@ class FederationHandler(BaseHandler):
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@defer.inlineCallbacks
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@defer.inlineCallbacks
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@log_function
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@log_function
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def _get_state_for_room(self, destination, room_id, event_id, include_event_in_state):
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def _get_state_for_room(
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self, destination, room_id, event_id, include_event_in_state
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):
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"""Requests all of the room state at a given event from a remote homeserver.
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"""Requests all of the room state at a given event from a remote homeserver.
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Args:
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Args:
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@ -635,6 +637,10 @@ class FederationHandler(BaseHandler):
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room_id (str)
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room_id (str)
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event_ids (Iterable[str])
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event_ids (Iterable[str])
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If we fail to fetch any of the events, a warning will be logged, and the event
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will be omitted from the result. Likewise, any events which turn out not to
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be in the given room.
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Returns:
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Returns:
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Deferred[dict[str, EventBase]]: A deferred resolving to a map
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Deferred[dict[str, EventBase]]: A deferred resolving to a map
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from event_id to event
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from event_id to event
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@ -643,35 +649,59 @@ class FederationHandler(BaseHandler):
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missing_events = set(event_ids) - fetched_events.keys()
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missing_events = set(event_ids) - fetched_events.keys()
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if not missing_events:
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if missing_events:
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return fetched_events
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logger.debug(
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"Fetching unknown state/auth events %s for room %s",
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missing_events,
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room_id,
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)
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logger.debug(
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room_version = yield self.store.get_room_version(room_id)
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"Fetching unknown state/auth events %s for room %s",
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missing_events,
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# XXX 20 requests at once? really?
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event_ids,
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for batch in batch_iter(missing_events, 20):
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deferreds = [
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run_in_background(
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self.federation_client.get_pdu,
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destinations=[destination],
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event_id=e_id,
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room_version=room_version,
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)
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for e_id in batch
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]
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res = yield make_deferred_yieldable(
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defer.DeferredList(deferreds, consumeErrors=True)
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)
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for success, result in res:
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if success and result:
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fetched_events[result.event_id] = result
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# check for events which were in the wrong room.
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#
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# this can happen if a remote server claims that the state or
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# auth_events at an event in room A are actually events in room B
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bad_events = list(
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(event_id, event.room_id)
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for event_id, event in fetched_events.items()
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if event.room_id != room_id
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)
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)
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room_version = yield self.store.get_room_version(room_id)
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for bad_event_id, bad_room_id in bad_events:
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# This is a bogus situation, but since we may only discover it a long time
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# XXX 20 requests at once? really?
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# after it happened, we try our best to carry on, by just omitting the
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for batch in batch_iter(missing_events, 20):
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# bad events from the returned auth/state set.
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deferreds = [
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logger.warning(
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run_in_background(
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"Remote server %s claims event %s in room %s is an auth/state "
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self.federation_client.get_pdu,
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"event in room %s",
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destinations=[destination],
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destination,
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event_id=e_id,
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bad_event_id,
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room_version=room_version,
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bad_room_id,
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)
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room_id,
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for e_id in batch
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]
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res = yield make_deferred_yieldable(
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defer.DeferredList(deferreds, consumeErrors=True)
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)
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)
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for success, result in res:
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del fetched_events[bad_event_id]
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if success and result:
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fetched_events[result.event_id] = result
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return fetched_events
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return fetched_events
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