diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py index 593932adb..c14ddac69 100644 --- a/synapse/handlers/federation.py +++ b/synapse/handlers/federation.py @@ -50,6 +50,7 @@ from synapse.api.errors import ( ) from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion, RoomVersions from synapse.crypto.event_signing import compute_event_signature +from synapse.federation.federation_base import FederationBase, event_from_pdu_json from synapse.event_auth import auth_types_for_event from synapse.events import EventBase from synapse.events.snapshot import EventContext @@ -99,7 +100,7 @@ class _NewEventInfo: auth_events = attr.ib(type=Optional[StateMap[EventBase]], default=None) -class FederationHandler(BaseHandler): +class FederationHandler(BaseHandler, FederationBase): """Handles events that originated from federation. Responsible for: a) handling received Pdus before handing them on as Events to the rest @@ -677,6 +678,35 @@ class FederationHandler(BaseHandler): return fetched_events + _forwarded_key = "net.maunium.msc2730.forwarded" + + async def _validate_forwarded_event(self, event: EventBase) -> Tuple[bool, Optional[str]]: + try: + source_evt_dict = {**event.content[self._forwarded_key]} + room_version = source_evt_dict["unsigned"]["room_version"] + source_evt_dict["type"] = event.type + source_evt_dict["content"] = {**event.content} + del source_evt_dict["unsigned"] + del source_evt_dict["content"][self._forwarded_key] + except (KeyError, TypeError): + logger.exception("Failed to read forward data") + return False, None + try: + source_evt = event_from_pdu_json(source_evt_dict, room_version) + except SynapseError: + logger.exception("Failed to parse forward data") + return False, None + try: + checked_evt = await self._check_sigs_and_hash(room_version, source_evt) + # _check_sigs_and_hash returns a redacted event if hash validation failed and + # a SynapseError if signature validation failed. In both those cases, we want to + # mark the forward as invalid. + valid = not checked_evt.internal_metadata.is_redacted() + except SynapseError: + logger.exception("Failed to validate forward signature") + valid = False + return valid, source_evt.event_id + async def _process_received_pdu( self, origin: str, event: EventBase, state: Optional[Iterable[EventBase]], ): @@ -697,6 +727,13 @@ class FederationHandler(BaseHandler): logger.debug("[%s %s] Processing event: %s", room_id, event_id, event) + if not event.is_state() and not event.redacts and self._forwarded_key in event.content: + valid, event_id = await self._validate_forwarded_event(event) + event.unsigned[self._forwarded_key] = { + "valid": valid, + "event_id": event_id, + } + try: context = await self._handle_new_event(origin, event, state=state) except AuthError as e: