diff options
Diffstat (limited to 'synapse')
| -rw-r--r-- | synapse/federation/federation_server.py | 2 | ||||
| -rw-r--r-- | synapse/handlers/federation.py | 69 |
2 files changed, 47 insertions, 24 deletions
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py index dbee404ea7..9a571e4fc7 100644 --- a/synapse/federation/federation_server.py +++ b/synapse/federation/federation_server.py @@ -618,7 +618,7 @@ class FederationServer(FederationBase): ) yield self.handler.on_receive_pdu( - origin, pdu, get_missing=True, sent_to_us_directly=True, + origin, pdu, sent_to_us_directly=True, ) def __str__(self): diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index 8d6bd7976d..2ccdc3bfa7 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -136,7 +136,7 @@ class FederationHandler(BaseHandler): @defer.inlineCallbacks def on_receive_pdu( - self, origin, pdu, get_missing=True, sent_to_us_directly=False, + self, origin, pdu, sent_to_us_directly=False, ): """ Process a PDU received via a federation /send/ transaction, or via backfill of missing prev_events @@ -145,7 +145,8 @@ class FederationHandler(BaseHandler): origin (str): server which initiated the /send/ transaction. Will be used to fetch missing events or state. pdu (FrozenEvent): received PDU - get_missing (bool): True if we should fetch missing prev_events + sent_to_us_directly (bool): True if this event was pushed to us; False if + we pulled it as the result of a missing prev_event. Returns (Deferred): completes with None """ @@ -250,7 +251,7 @@ class FederationHandler(BaseHandler): pdu.internal_metadata.outlier = True elif min_depth and pdu.depth > min_depth: missing_prevs = prevs - seen - if get_missing and missing_prevs: + if sent_to_us_directly and missing_prevs: # If we're missing stuff, ensure we only fetch stuff one # at a time. logger.info( @@ -282,24 +283,46 @@ class FederationHandler(BaseHandler): room_id, event_id, len(missing_prevs), shortstr(missing_prevs), ) - if sent_to_us_directly and prevs - seen: - # If they have sent it to us directly, and the server - # isn't telling us about the auth events that it's - # made a message referencing, we explode - logger.warn( - "[%s %s] Failed to fetch %d prev events: rejecting", - room_id, event_id, len(prevs - seen), - ) - raise FederationError( - "ERROR", - 403, - ( - "Your server isn't divulging details about prev_events " - "referenced in this event." - ), - affected=pdu.event_id, - ) - elif prevs - seen: + if prevs - seen: + # We've still not been able to get all of the prev_events for this event. + # + # In this case, we need to fall back to asking another server in the + # federation for the state at this event. That's ok provided we then + # resolve the state against other bits of the DAG before using it (which + # will ensure that you can't just take over a room by sending an event, + # withholding its prev_events, and declaring yourself to be an admin in + # the subsequent state request). + # + # Now, if we're pulling this event as a missing prev_event, then clearly + # this event is not going to become the only forward-extremity and we are + # guaranteed to resolve its state against our existing forward + # extremities, so that should be fine. + # + # On the other hand, if this event was pushed to us, it is possible for + # it to become the only forward-extremity in the room, and we would then + # trust its state to be the state for the whole room. This is very bad. + # Further, if the event was pushed to us, there is no excuse for us not to + # have all the prev_events. We therefore reject any such events. + # + # XXX this really feels like it could/should be merged with the above, + # but there is an interaction with min_depth that I'm not really + # following. + + if sent_to_us_directly: + logger.warn( + "[%s %s] Failed to fetch %d prev events: rejecting", + room_id, event_id, len(prevs - seen), + ) + raise FederationError( + "ERROR", + 403, + ( + "Your server isn't divulging details about prev_events " + "referenced in this event." + ), + affected=pdu.event_id, + ) + # Calculate the state of the previous events, and # de-conflict them to find the current state. state_groups = [] @@ -464,7 +487,7 @@ class FederationHandler(BaseHandler): yield self.on_receive_pdu( origin, ev, - get_missing=False + sent_to_us_directly=False, ) except FederationError as e: if e.code == 403: @@ -1112,7 +1135,7 @@ class FederationHandler(BaseHandler): try: logger.info("Processing queued PDU %s which was received " "while we were joining %s", p.event_id, p.room_id) - yield self.on_receive_pdu(origin, p) + yield self.on_receive_pdu(origin, p, sent_to_us_directly=True) except Exception as e: logger.warn( "Error handling queued PDU %s from %s: %s", |