# Copyright 2021 The Matrix.org Foundation C.I.C. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. import logging from http import HTTPStatus from typing import ( TYPE_CHECKING, Collection, Container, Dict, Iterable, List, Optional, Sequence, Set, Tuple, ) import attr from prometheus_client import Counter from twisted.internet import defer from synapse import event_auth from synapse.api.constants import ( EventContentFields, EventTypes, GuestAccess, Membership, RejectedReason, RoomEncryptionAlgorithms, ) from synapse.api.errors import ( AuthError, Codes, FederationError, HttpResponseException, RequestSendFailed, SynapseError, ) from synapse.api.room_versions import KNOWN_ROOM_VERSIONS from synapse.event_auth import auth_types_for_event from synapse.events import EventBase from synapse.events.snapshot import EventContext from synapse.federation.federation_client import InvalidResponseError from synapse.logging.context import ( make_deferred_yieldable, nested_logging_context, run_in_background, ) from synapse.logging.utils import log_function from synapse.metrics.background_process_metrics import run_as_background_process from synapse.replication.http.devices import ReplicationUserDevicesResyncRestServlet from synapse.replication.http.federation import ( ReplicationFederationSendEventsRestServlet, ) from synapse.state import StateResolutionStore from synapse.storage.databases.main.events_worker import EventRedactBehaviour from synapse.types import ( MutableStateMap, PersistedEventPosition, RoomStreamToken, StateMap, UserID, get_domain_from_id, ) from synapse.util.async_helpers import Linearizer, concurrently_execute from synapse.util.iterutils import batch_iter from synapse.util.retryutils import NotRetryingDestination from synapse.util.stringutils import shortstr if TYPE_CHECKING: from synapse.server import HomeServer logger = logging.getLogger(__name__) soft_failed_event_counter = Counter( "synapse_federation_soft_failed_events_total", "Events received over federation that we marked as soft_failed", ) @attr.s(slots=True, frozen=True, auto_attribs=True) class _NewEventInfo: """Holds information about a received event, ready for passing to _auth_and_persist_events Attributes: event: the received event claimed_auth_event_map: a map of (type, state_key) => event for the event's claimed auth_events. This can include events which have not yet been persisted, in the case that we are backfilling a batch of events. Note: May be incomplete: if we were unable to find all of the claimed auth events. Also, treat the contents with caution: the events might also have been rejected, might not yet have been authorized themselves, or they might be in the wrong room. """ event: EventBase claimed_auth_event_map: StateMap[EventBase] class FederationEventHandler: """Handles events that originated from federation. Responsible for handing incoming events and passing them on to the rest of the homeserver (including auth and state conflict resolutions) """ def __init__(self, hs: "HomeServer"): self._store = hs.get_datastore() self._storage = hs.get_storage() self._state_store = self._storage.state self._state_handler = hs.get_state_handler() self._event_creation_handler = hs.get_event_creation_handler() self._event_auth_handler = hs.get_event_auth_handler() self._message_handler = hs.get_message_handler() self._action_generator = hs.get_action_generator() self._state_resolution_handler = hs.get_state_resolution_handler() # avoid a circular dependency by deferring execution here self._get_room_member_handler = hs.get_room_member_handler self._federation_client = hs.get_federation_client() self._third_party_event_rules = hs.get_third_party_event_rules() self._notifier = hs.get_notifier() self._is_mine_id = hs.is_mine_id self._server_name = hs.hostname self._instance_name = hs.get_instance_name() self._config = hs.config self._ephemeral_messages_enabled = hs.config.server.enable_ephemeral_messages self._send_events = ReplicationFederationSendEventsRestServlet.make_client(hs) if hs.config.worker.worker_app: self._user_device_resync = ( ReplicationUserDevicesResyncRestServlet.make_client(hs) ) else: self._device_list_updater = hs.get_device_handler().device_list_updater # When joining a room we need to queue any events for that room up. # For each room, a list of (pdu, origin) tuples. # TODO: replace this with something more elegant, probably based around the # federation event staging area. self.room_queues: Dict[str, List[Tuple[EventBase, str]]] = {} self._room_pdu_linearizer = Linearizer("fed_room_pdu") async def on_receive_pdu(self, origin: str, pdu: EventBase) -> None: """Process a PDU received via a federation /send/ transaction Args: origin: server which initiated the /send/ transaction. Will be used to fetch missing events or state. pdu: received PDU """ # We should never see any outliers here. assert not pdu.internal_metadata.outlier room_id = pdu.room_id event_id = pdu.event_id # We reprocess pdus when we have seen them only as outliers existing = await self._store.get_event( event_id, allow_none=True, allow_rejected=True ) # FIXME: Currently we fetch an event again when we already have it # if it has been marked as an outlier. if existing: if not existing.internal_metadata.is_outlier(): logger.info( "Ignoring received event %s which we have already seen", event_id ) return if pdu.internal_metadata.is_outlier(): logger.info( "Ignoring received outlier %s which we already have as an outlier", event_id, ) return logger.info("De-outliering event %s", event_id) # do some initial sanity-checking of the event. In particular, make # sure it doesn't have hundreds of prev_events or auth_events, which # could cause a huge state resolution or cascade of event fetches. try: self._sanity_check_event(pdu) except SynapseError as err: logger.warning("Received event failed sanity checks") raise FederationError("ERROR", err.code, err.msg, affected=pdu.event_id) # If we are currently in the process of joining this room, then we # queue up events for later processing. if room_id in self.room_queues: logger.info( "Queuing PDU from %s for now: join in progress", origin, ) self.room_queues[room_id].append((pdu, origin)) return # If we're not in the room just ditch the event entirely. This is # probably an old server that has come back and thinks we're still in # the room (or we've been rejoined to the room by a state reset). # # Note that if we were never in the room then we would have already # dropped the event, since we wouldn't know the room version. is_in_room = await self._event_auth_handler.check_host_in_room( room_id, self._server_name ) if not is_in_room: logger.info( "Ignoring PDU from %s as we're not in the room", origin, ) return None # Try to fetch any missing prev events to fill in gaps in the graph prevs = set(pdu.prev_event_ids()) seen = await self._store.have_events_in_timeline(prevs) missing_prevs = prevs - seen if missing_prevs: # We only backfill backwards to the min depth. min_depth = await self.get_min_depth_for_context(pdu.room_id) logger.debug("min_depth: %d", min_depth) if min_depth is not None and pdu.depth > min_depth: # If we're missing stuff, ensure we only fetch stuff one # at a time. logger.info( "Acquiring room lock to fetch %d missing prev_events: %s", len(missing_prevs), shortstr(missing_prevs), ) with (await self._room_pdu_linearizer.queue(pdu.room_id)): logger.info( "Acquired room lock to fetch %d missing prev_events", len(missing_prevs), ) try: await self._get_missing_events_for_pdu( origin, pdu, prevs, min_depth ) except Exception as e: raise Exception( "Error fetching missing prev_events for %s: %s" % (event_id, e) ) from e # Update the set of things we've seen after trying to # fetch the missing stuff seen = await self._store.have_events_in_timeline(prevs) missing_prevs = prevs - seen if not missing_prevs: logger.info("Found all missing prev_events") if missing_prevs: # since 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. (XXX: apart from # min_depth?) # # We therefore reject any such events. logger.warning( "Rejecting: failed to fetch %d prev events: %s", len(missing_prevs), shortstr(missing_prevs), ) raise FederationError( "ERROR", 403, ( "Your server isn't divulging details about prev_events " "referenced in this event." ), affected=pdu.event_id, ) await self._process_received_pdu(origin, pdu, state=None) @log_function async def on_send_membership_event( self, origin: str, event: EventBase ) -> Tuple[EventBase, EventContext]: """ We have received a join/leave/knock event for a room via send_join/leave/knock. Verify that event and send it into the room on the remote homeserver's behalf. This is quite similar to on_receive_pdu, with the following principal differences: * only membership events are permitted (and only events with sender==state_key -- ie, no kicks or bans) * *We* send out the event on behalf of the remote server. * We enforce the membership restrictions of restricted rooms. * Rejected events result in an exception rather than being stored. There are also other differences, however it is not clear if these are by design or omission. In particular, we do not attempt to backfill any missing prev_events. Args: origin: The homeserver of the remote (joining/invited/knocking) user. event: The member event that has been signed by the remote homeserver. Returns: The event and context of the event after inserting it into the room graph. Raises: SynapseError if the event is not accepted into the room """ logger.debug( "on_send_membership_event: Got event: %s, signatures: %s", event.event_id, event.signatures, ) if get_domain_from_id(event.sender) != origin: logger.info( "Got send_membership request for user %r from different origin %s", event.sender, origin, ) raise SynapseError(403, "User not from origin", Codes.FORBIDDEN) if event.sender != event.state_key: raise SynapseError(400, "state_key and sender must match", Codes.BAD_JSON) assert not event.internal_metadata.outlier # Send this event on behalf of the other server. # # The remote server isn't a full participant in the room at this point, so # may not have an up-to-date list of the other homeservers participating in # the room, so we send it on their behalf. event.internal_metadata.send_on_behalf_of = origin context = await self._state_handler.compute_event_context(event) context = await self._check_event_auth(origin, event, context) if context.rejected: raise SynapseError( 403, f"{event.membership} event was rejected", Codes.FORBIDDEN ) # for joins, we need to check the restrictions of restricted rooms if event.membership == Membership.JOIN: await self.check_join_restrictions(context, event) # for knock events, we run the third-party event rules. It's not entirely clear # why we don't do this for other sorts of membership events. if event.membership == Membership.KNOCK: event_allowed, _ = await self._third_party_event_rules.check_event_allowed( event, context ) if not event_allowed: logger.info("Sending of knock %s forbidden by third-party rules", event) raise SynapseError( 403, "This event is not allowed in this context", Codes.FORBIDDEN ) # all looks good, we can persist the event. await self._run_push_actions_and_persist_event(event, context) return event, context async def check_join_restrictions( self, context: EventContext, event: EventBase ) -> None: """Check that restrictions in restricted join rules are matched Called when we receive a join event via send_join. Raises an auth error if the restrictions are not matched. """ prev_state_ids = await context.get_prev_state_ids() # Check if the user is already in the room or invited to the room. user_id = event.state_key prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None) prev_member_event = None if prev_member_event_id: prev_member_event = await self._store.get_event(prev_member_event_id) # Check if the member should be allowed access via membership in a space. await self._event_auth_handler.check_restricted_join_rules( prev_state_ids, event.room_version, user_id, prev_member_event, ) @log_function async def backfill( self, dest: str, room_id: str, limit: int, extremities: List[str] ) -> None: """Trigger a backfill request to `dest` for the given `room_id` This will attempt to get more events from the remote. If the other side has no new events to offer, this will return an empty list. As the events are received, we check their signatures, and also do some sanity-checking on them. If any of the backfilled events are invalid, this method throws a SynapseError. We might also raise an InvalidResponseError if the response from the remote server is just bogus. TODO: make this more useful to distinguish failures of the remote server from invalid events (there is probably no point in trying to re-fetch invalid events from every other HS in the room.) """ if dest == self._server_name: raise SynapseError(400, "Can't backfill from self.") events = await self._federation_client.backfill( dest, room_id, limit=limit, extremities=extremities ) if not events: return # if there are any events in the wrong room, the remote server is buggy and # should not be trusted. for ev in events: if ev.room_id != room_id: raise InvalidResponseError( f"Remote server {dest} returned event {ev.event_id} which is in " f"room {ev.room_id}, when we were backfilling in {room_id}" ) await self._process_pulled_events(dest, events, backfilled=True) async def _get_missing_events_for_pdu( self, origin: str, pdu: EventBase, prevs: Set[str], min_depth: int ) -> None: """ Args: origin: Origin of the pdu. Will be called to get the missing events pdu: received pdu prevs: List of event ids which we are missing min_depth: Minimum depth of events to return. """ room_id = pdu.room_id event_id = pdu.event_id seen = await self._store.have_events_in_timeline(prevs) if not prevs - seen: return latest_list = await self._store.get_latest_event_ids_in_room(room_id) # We add the prev events that we have seen to the latest # list to ensure the remote server doesn't give them to us latest = set(latest_list) latest |= seen logger.info( "Requesting missing events between %s and %s", shortstr(latest), event_id, ) # XXX: we set timeout to 10s to help workaround # https://github.com/matrix-org/synapse/issues/1733. # The reason is to avoid holding the linearizer lock # whilst processing inbound /send transactions, causing # FDs to stack up and block other inbound transactions # which empirically can currently take up to 30 minutes. # # N.B. this explicitly disables retry attempts. # # N.B. this also increases our chances of falling back to # fetching fresh state for the room if the missing event # can't be found, which slightly reduces our security. # it may also increase our DAG extremity count for the room, # causing additional state resolution? See #1760. # However, fetching state doesn't hold the linearizer lock # apparently. # # see https://github.com/matrix-org/synapse/pull/1744 # # ---- # # Update richvdh 2018/09/18: There are a number of problems with timing this # request out aggressively on the client side: # # - it plays badly with the server-side rate-limiter, which starts tarpitting you # if you send too many requests at once, so you end up with the server carefully # working through the backlog of your requests, which you have already timed # out. # # - for this request in particular, we now (as of # https://github.com/matrix-org/synapse/pull/3456) reject any PDUs where the # server can't produce a plausible-looking set of prev_events - so we becone # much more likely to reject the event. # # - contrary to what it says above, we do *not* fall back to fetching fresh state # for the room if get_missing_events times out. Rather, we give up processing # the PDU whose prevs we are missing, which then makes it much more likely that # we'll end up back here for the *next* PDU in the list, which exacerbates the # problem. # # - the aggressive 10s timeout was introduced to deal with incoming federation # requests taking 8 hours to process. It's not entirely clear why that was going # on; certainly there were other issues causing traffic storms which are now # resolved, and I think in any case we may be more sensible about our locking # now. We're *certainly* more sensible about our logging. # # All that said: Let's try increasing the timeout to 60s and see what happens. try: missing_events = await self._federation_client.get_missing_events( origin, room_id, earliest_events_ids=list(latest), latest_events=[pdu], limit=10, min_depth=min_depth, timeout=60000, ) except (RequestSendFailed, HttpResponseException, NotRetryingDestination) as e: # We failed to get the missing events, but since we need to handle # the case of `get_missing_events` not returning the necessary # events anyway, it is safe to simply log the error and continue. logger.warning("Failed to get prev_events: %s", e) return logger.info("Got %d prev_events", len(missing_events)) await self._process_pulled_events(origin, missing_events, backfilled=False) async def _process_pulled_events( self, origin: str, events: Iterable[EventBase], backfilled: bool ) -> None: """Process a batch of events we have pulled from a remote server Pulls in any events required to auth the events, persists the received events, and notifies clients, if appropriate. Assumes the events have already had their signatures and hashes checked. Params: origin: The server we received these events from events: The received events. backfilled: True if this is part of a historical batch of events (inhibits notification to clients, and validation of device keys.) """ # We want to sort these by depth so we process them and # tell clients about them in order. sorted_events = sorted(events, key=lambda x: x.depth) for ev in sorted_events: with nested_logging_context(ev.event_id): await self._process_pulled_event(origin, ev, backfilled=backfilled) async def _process_pulled_event( self, origin: str, event: EventBase, backfilled: bool ) -> None: """Process a single event that we have pulled from a remote server Pulls in any events required to auth the event, persists the received event, and notifies clients, if appropriate. Assumes the event has already had its signatures and hashes checked. This is somewhat equivalent to on_receive_pdu, but applies somewhat different logic in the case that we are missing prev_events (in particular, it just requests the state at that point, rather than triggering a get_missing_events) - so is appropriate when we have pulled the event from a remote server, rather than having it pushed to us. Params: origin: The server we received this event from events: The received event backfilled: True if this is part of a historical batch of events (inhibits notification to clients, and validation of device keys.) """ logger.info("Processing pulled event %s", event) # these should not be outliers. assert not event.internal_metadata.is_outlier() event_id = event.event_id existing = await self._store.get_event( event_id, allow_none=True, allow_rejected=True ) if existing: if not existing.internal_metadata.is_outlier(): logger.info( "Ignoring received event %s which we have already seen", event_id, ) return logger.info("De-outliering event %s", event_id) try: self._sanity_check_event(event) except SynapseError as err: logger.warning("Event %s failed sanity check: %s", event_id, err) return try: state = await self._resolve_state_at_missing_prevs(origin, event) await self._process_received_pdu( origin, event, state=state, backfilled=backfilled ) except FederationError as e: if e.code == 403: logger.warning("Pulled event %s failed history check.", event_id) else: raise async def _resolve_state_at_missing_prevs( self, dest: str, event: EventBase ) -> Optional[Iterable[EventBase]]: """Calculate the state at an event with missing prev_events. This is used when we have pulled a batch of events from a remote server, and still don't have all the prev_events. If we already have all the prev_events for `event`, this method does nothing. Otherwise, the missing prevs become new backwards extremities, and we fall back to asking the remote server for the state after each missing `prev_event`, and resolving across them. That's ok provided we then resolve the state against other bits of the DAG before using it - in other words, that the received event `event` is not going to become the only forwards_extremity in the room (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). In other words: we should only call this method if `event` has been *pulled* as part of a batch of missing prev events, or similar. Params: dest: the remote server to ask for state at the missing prevs. Typically, this will be the server we got `event` from. event: an event to check for missing prevs. Returns: if we already had all the prev events, `None`. Otherwise, returns a list of the events in the state at `event`. """ room_id = event.room_id event_id = event.event_id prevs = set(event.prev_event_ids()) seen = await self._store.have_events_in_timeline(prevs) missing_prevs = prevs - seen if not missing_prevs: return None logger.info( "Event %s is missing prev_events %s: calculating state for a " "backwards extremity", event_id, shortstr(missing_prevs), ) # Calculate the state after each of the previous events, and # resolve them to find the correct state at the current event. event_map = {event_id: event} try: # Get the state of the events we know about ours = await self._state_store.get_state_groups_ids(room_id, seen) # state_maps is a list of mappings from (type, state_key) to event_id state_maps: List[StateMap[str]] = list(ours.values()) # we don't need this any more, let's delete it. del ours # Ask the remote server for the states we don't # know about for p in missing_prevs: logger.info("Requesting state after missing prev_event %s", p) with nested_logging_context(p): # note that if any of the missing prevs share missing state or # auth events, the requests to fetch those events are deduped # by the get_pdu_cache in federation_client. remote_state = await self._get_state_after_missing_prev_event( dest, room_id, p ) remote_state_map = { (x.type, x.state_key): x.event_id for x in remote_state } state_maps.append(remote_state_map) for x in remote_state: event_map[x.event_id] = x room_version = await self._store.get_room_version_id(room_id) state_map = await self._state_resolution_handler.resolve_events_with_store( room_id, room_version, state_maps, event_map, state_res_store=StateResolutionStore(self._store), ) # We need to give _process_received_pdu the actual state events # rather than event ids, so generate that now. # First though we need to fetch all the events that are in # state_map, so we can build up the state below. evs = await self._store.get_events( list(state_map.values()), get_prev_content=False, redact_behaviour=EventRedactBehaviour.AS_IS, ) event_map.update(evs) state = [event_map[e] for e in state_map.values()] except Exception: logger.warning( "Error attempting to resolve state at missing prev_events", exc_info=True, ) raise FederationError( "ERROR", 403, "We can't get valid state history.", affected=event_id, ) return state async def _get_state_after_missing_prev_event( self, destination: str, room_id: str, event_id: str, ) -> List[EventBase]: """Requests all of the room state at a given event from a remote homeserver. Args: destination: The remote homeserver to query for the state. room_id: The id of the room we're interested in. event_id: The id of the event we want the state at. Returns: A list of events in the state, including the event itself """ ( state_event_ids, auth_event_ids, ) = await self._federation_client.get_room_state_ids( destination, room_id, event_id=event_id ) logger.debug( "state_ids returned %i state events, %i auth events", len(state_event_ids), len(auth_event_ids), ) # start by just trying to fetch the events from the store desired_events = set(state_event_ids) desired_events.add(event_id) logger.debug("Fetching %i events from cache/store", len(desired_events)) fetched_events = await self._store.get_events( desired_events, allow_rejected=True ) missing_desired_events = desired_events - fetched_events.keys() logger.debug( "We are missing %i events (got %i)", len(missing_desired_events), len(fetched_events), ) # We probably won't need most of the auth events, so let's just check which # we have for now, rather than thrashing the event cache with them all # unnecessarily. # TODO: we probably won't actually need all of the auth events, since we # already have a bunch of the state events. It would be nice if the # federation api gave us a way of finding out which we actually need. missing_auth_events = set(auth_event_ids) - fetched_events.keys() missing_auth_events.difference_update( await self._store.have_seen_events(room_id, missing_auth_events) ) logger.debug("We are also missing %i auth events", len(missing_auth_events)) missing_events = missing_desired_events | missing_auth_events logger.debug("Fetching %i events from remote", len(missing_events)) await self._get_events_and_persist( destination=destination, room_id=room_id, event_ids=missing_events ) # we need to make sure we re-load from the database to get the rejected # state correct. fetched_events.update( await self._store.get_events(missing_desired_events, allow_rejected=True) ) # check for events which were in the wrong room. # # this can happen if a remote server claims that the state or # auth_events at an event in room A are actually events in room B bad_events = [ (event_id, event.room_id) for event_id, event in fetched_events.items() if event.room_id != room_id ] for bad_event_id, bad_room_id in bad_events: # This is a bogus situation, but since we may only discover it a long time # after it happened, we try our best to carry on, by just omitting the # bad events from the returned state set. logger.warning( "Remote server %s claims event %s in room %s is an auth/state " "event in room %s", destination, bad_event_id, bad_room_id, room_id, ) del fetched_events[bad_event_id] # if we couldn't get the prev event in question, that's a problem. remote_event = fetched_events.get(event_id) if not remote_event: raise Exception("Unable to get missing prev_event %s" % (event_id,)) # missing state at that event is a warning, not a blocker # XXX: this doesn't sound right? it means that we'll end up with incomplete # state. failed_to_fetch = desired_events - fetched_events.keys() if failed_to_fetch: logger.warning( "Failed to fetch missing state events for %s %s", event_id, failed_to_fetch, ) remote_state = [ fetched_events[e_id] for e_id in state_event_ids if e_id in fetched_events ] if remote_event.is_state() and remote_event.rejected_reason is None: remote_state.append(remote_event) return remote_state async def _process_received_pdu( self, origin: str, event: EventBase, state: Optional[Iterable[EventBase]], backfilled: bool = False, ) -> None: """Called when we have a new non-outlier event. This is called when we have a new event to add to the room DAG - either directly via a /send request, retrieved via get_missing_events after a /send request, or backfilled after a client request. We need to do auth checks and put it through the StateHandler. Args: origin: server sending the event event: event to be persisted state: Normally None, but if we are handling a gap in the graph (ie, we are missing one or more prev_events), the resolved state at the event backfilled: True if this is part of a historical batch of events (inhibits notification to clients, and validation of device keys.) """ logger.debug("Processing event: %s", event) assert not event.internal_metadata.outlier try: context = await self._state_handler.compute_event_context( event, old_state=state ) context = await self._check_event_auth( origin, event, context, state=state, backfilled=backfilled, ) except AuthError as e: raise FederationError("ERROR", e.code, e.msg, affected=event.event_id) await self._run_push_actions_and_persist_event(event, context, backfilled) if backfilled: return # For encrypted messages we check that we know about the sending device, # if we don't then we mark the device cache for that user as stale. if event.type == EventTypes.Encrypted: device_id = event.content.get("device_id") sender_key = event.content.get("sender_key") cached_devices = await self._store.get_cached_devices_for_user(event.sender) resync = False # Whether we should resync device lists. device = None if device_id is not None: device = cached_devices.get(device_id) if device is None: logger.info( "Received event from remote device not in our cache: %s %s", event.sender, device_id, ) resync = True # We also check if the `sender_key` matches what we expect. if sender_key is not None: # Figure out what sender key we're expecting. If we know the # device and recognize the algorithm then we can work out the # exact key to expect. Otherwise check it matches any key we # have for that device. current_keys: Container[str] = [] if device: keys = device.get("keys", {}).get("keys", {}) if ( event.content.get("algorithm") == RoomEncryptionAlgorithms.MEGOLM_V1_AES_SHA2 ): # For this algorithm we expect a curve25519 key. key_name = "curve25519:%s" % (device_id,) current_keys = [keys.get(key_name)] else: # We don't know understand the algorithm, so we just # check it matches a key for the device. current_keys = keys.values() elif device_id: # We don't have any keys for the device ID. pass else: # The event didn't include a device ID, so we just look for # keys across all devices. current_keys = [ key for device in cached_devices.values() for key in device.get("keys", {}).get("keys", {}).values() ] # We now check that the sender key matches (one of) the expected # keys. if sender_key not in current_keys: logger.info( "Received event from remote device with unexpected sender key: %s %s: %s", event.sender, device_id or "", sender_key, ) resync = True if resync: run_as_background_process( "resync_device_due_to_pdu", self._resync_device, event.sender, ) await self._handle_marker_event(origin, event) async def _resync_device(self, sender: str) -> None: """We have detected that the device list for the given user may be out of sync, so we try and resync them. """ try: await self._store.mark_remote_user_device_cache_as_stale(sender) # Immediately attempt a resync in the background if self._config.worker.worker_app: await self._user_device_resync(user_id=sender) else: await self._device_list_updater.user_device_resync(sender) except Exception: logger.exception("Failed to resync device for %s", sender) async def _handle_marker_event(self, origin: str, marker_event: EventBase) -> None: """Handles backfilling the insertion event when we receive a marker event that points to one. Args: origin: Origin of the event. Will be called to get the insertion event marker_event: The event to process """ if marker_event.type != EventTypes.MSC2716_MARKER: # Not a marker event return if marker_event.rejected_reason is not None: # Rejected event return # Skip processing a marker event if the room version doesn't # support it or the event is not from the room creator. room_version = await self._store.get_room_version(marker_event.room_id) create_event = await self._store.get_create_event_for_room(marker_event.room_id) room_creator = create_event.content.get(EventContentFields.ROOM_CREATOR) if ( not room_version.msc2716_historical or not self._config.experimental.msc2716_enabled or marker_event.sender != room_creator ): return logger.debug("_handle_marker_event: received %s", marker_event) insertion_event_id = marker_event.content.get( EventContentFields.MSC2716_MARKER_INSERTION ) if insertion_event_id is None: # Nothing to retrieve then (invalid marker) return logger.debug( "_handle_marker_event: backfilling insertion event %s", insertion_event_id ) await self._get_events_and_persist( origin, marker_event.room_id, [insertion_event_id], ) insertion_event = await self._store.get_event( insertion_event_id, allow_none=True ) if insertion_event is None: logger.warning( "_handle_marker_event: server %s didn't return insertion event %s for marker %s", origin, insertion_event_id, marker_event.event_id, ) return logger.debug( "_handle_marker_event: succesfully backfilled insertion event %s from marker event %s", insertion_event, marker_event, ) await self._store.insert_insertion_extremity( insertion_event_id, marker_event.room_id ) logger.debug( "_handle_marker_event: insertion extremity added for %s from marker event %s", insertion_event, marker_event, ) async def _get_events_and_persist( self, destination: str, room_id: str, event_ids: Collection[str] ) -> None: """Fetch the given events from a server, and persist them as outliers. This function *does not* recursively get missing auth events of the newly fetched events. Callers must include in the `event_ids` argument any missing events from the auth chain. Logs a warning if we can't find the given event. """ room_version = await self._store.get_room_version(room_id) event_map: Dict[str, EventBase] = {} async def get_event(event_id: str) -> None: with nested_logging_context(event_id): try: event = await self._federation_client.get_pdu( [destination], event_id, room_version, outlier=True, ) if event is None: logger.warning( "Server %s didn't return event %s", destination, event_id, ) return event_map[event.event_id] = event except Exception as e: logger.warning( "Error fetching missing state/auth event %s: %s %s", event_id, type(e), e, ) await concurrently_execute(get_event, event_ids, 5) logger.info("Fetched %i events of %i requested", len(event_map), len(event_ids)) # we now need to auth the events in an order which ensures that each event's # auth_events are authed before the event itself. # # XXX: it might be possible to kick this process off in parallel with fetching # the events. while event_map: # build a list of events whose auth events are not in the queue. roots = tuple( ev for ev in event_map.values() if not any(aid in event_map for aid in ev.auth_event_ids()) ) if not roots: # if *none* of the remaining events are ready, that means # we have a loop. This either means a bug in our logic, or that # somebody has managed to create a loop (which requires finding a # hash collision in room v2 and later). logger.warning( "Loop found in auth events while fetching missing state/auth " "events: %s", shortstr(event_map.keys()), ) return logger.info( "Persisting %i of %i remaining events", len(roots), len(event_map) ) await self._auth_and_persist_fetched_events(destination, room_id, roots) for ev in roots: del event_map[ev.event_id] async def _auth_and_persist_fetched_events( self, origin: str, room_id: str, fetched_events: Collection[EventBase] ) -> None: """Persist the events fetched by _get_events_and_persist. The events should not depend on one another, e.g. this should be used to persist a bunch of outliers, but not a chunk of individual events that depend on each other for state calculations. We also assume that all of the auth events for all of the events have already been persisted. Notifies about the events where appropriate. Params: origin: where the events came from room_id: the room that the events are meant to be in (though this has not yet been checked) event_id: map from event_id -> event for the fetched events """ # get all the auth events for all the events in this batch. By now, they should # have been persisted. auth_events = { aid for event in fetched_events for aid in event.auth_event_ids() } persisted_events = await self._store.get_events( auth_events, allow_rejected=True, ) event_infos = [] for event in fetched_events: auth = {} for auth_event_id in event.auth_event_ids(): ae = persisted_events.get(auth_event_id) if ae: auth[(ae.type, ae.state_key)] = ae else: logger.info("Missing auth event %s", auth_event_id) event_infos.append(_NewEventInfo(event, auth)) if not event_infos: return async def prep(ev_info: _NewEventInfo) -> EventContext: event = ev_info.event with nested_logging_context(suffix=event.event_id): res = EventContext.for_outlier() res = await self._check_event_auth( origin, event, res, claimed_auth_event_map=ev_info.claimed_auth_event_map, ) return res contexts = await make_deferred_yieldable( defer.gatherResults( [run_in_background(prep, ev_info) for ev_info in event_infos], consumeErrors=True, ) ) await self.persist_events_and_notify( room_id, [ (ev_info.event, context) for ev_info, context in zip(event_infos, contexts) ], ) async def _check_event_auth( self, origin: str, event: EventBase, context: EventContext, state: Optional[Iterable[EventBase]] = None, claimed_auth_event_map: Optional[StateMap[EventBase]] = None, backfilled: bool = False, ) -> EventContext: """ Checks whether an event should be rejected (for failing auth checks). Args: origin: The host the event originates from. event: The event itself. context: The event context. state: The state events used to check the event for soft-fail. If this is not provided the current state events will be used. claimed_auth_event_map: A map of (type, state_key) => event for the event's claimed auth_events. Possibly incomplete, and possibly including events that are not yet persisted, or authed, or in the right room. Only populated when populating outliers. backfilled: True if the event was backfilled. Returns: The updated context object. """ # claimed_auth_event_map should be given iff the event is an outlier assert bool(claimed_auth_event_map) == event.internal_metadata.outlier room_version = await self._store.get_room_version_id(event.room_id) room_version_obj = KNOWN_ROOM_VERSIONS[room_version] if claimed_auth_event_map: # if we have a copy of the auth events from the event, use that as the # basis for auth. auth_events = claimed_auth_event_map else: # otherwise, we calculate what the auth events *should* be, and use that prev_state_ids = await context.get_prev_state_ids() auth_events_ids = self._event_auth_handler.compute_auth_events( event, prev_state_ids, for_verification=True ) auth_events_x = await self._store.get_events(auth_events_ids) auth_events = {(e.type, e.state_key): e for e in auth_events_x.values()} try: ( context, auth_events_for_auth, ) = await self._update_auth_events_and_context_for_auth( origin, event, context, auth_events ) except Exception: # We don't really mind if the above fails, so lets not fail # processing if it does. However, it really shouldn't fail so # let's still log as an exception since we'll still want to fix # any bugs. logger.exception( "Failed to double check auth events for %s with remote. " "Ignoring failure and continuing processing of event.", event.event_id, ) auth_events_for_auth = auth_events try: event_auth.check(room_version_obj, event, auth_events=auth_events_for_auth) except AuthError as e: logger.warning("Failed auth resolution for %r because %s", event, e) context.rejected = RejectedReason.AUTH_ERROR if not context.rejected: await self._check_for_soft_fail(event, state, backfilled, origin=origin) await self._maybe_kick_guest_users(event) # If we are going to send this event over federation we precaclculate # the joined hosts. if event.internal_metadata.get_send_on_behalf_of(): await self._event_creation_handler.cache_joined_hosts_for_event( event, context ) return context async def _maybe_kick_guest_users(self, event: EventBase) -> None: if event.type != EventTypes.GuestAccess: return guest_access = event.content.get(EventContentFields.GUEST_ACCESS) if guest_access == GuestAccess.CAN_JOIN: return current_state_map = await self._state_handler.get_current_state(event.room_id) current_state = list(current_state_map.values()) await self._get_room_member_handler().kick_guest_users(current_state) async def _check_for_soft_fail( self, event: EventBase, state: Optional[Iterable[EventBase]], backfilled: bool, origin: str, ) -> None: """Checks if we should soft fail the event; if so, marks the event as such. Args: event state: The state at the event if we don't have all the event's prev events backfilled: Whether the event is from backfill origin: The host the event originates from. """ # For new (non-backfilled and non-outlier) events we check if the event # passes auth based on the current state. If it doesn't then we # "soft-fail" the event. if backfilled or event.internal_metadata.is_outlier(): return extrem_ids_list = await self._store.get_latest_event_ids_in_room(event.room_id) extrem_ids = set(extrem_ids_list) prev_event_ids = set(event.prev_event_ids()) if extrem_ids == prev_event_ids: # If they're the same then the current state is the same as the # state at the event, so no point rechecking auth for soft fail. return room_version = await self._store.get_room_version_id(event.room_id) room_version_obj = KNOWN_ROOM_VERSIONS[room_version] # Calculate the "current state". if state is not None: # If we're explicitly given the state then we won't have all the # prev events, and so we have a gap in the graph. In this case # we want to be a little careful as we might have been down for # a while and have an incorrect view of the current state, # however we still want to do checks as gaps are easy to # maliciously manufacture. # # So we use a "current state" that is actually a state # resolution across the current forward extremities and the # given state at the event. This should correctly handle cases # like bans, especially with state res v2. state_sets_d = await self._state_store.get_state_groups( event.room_id, extrem_ids ) state_sets: List[Iterable[EventBase]] = list(state_sets_d.values()) state_sets.append(state) current_states = await self._state_handler.resolve_events( room_version, state_sets, event ) current_state_ids: StateMap[str] = { k: e.event_id for k, e in current_states.items() } else: current_state_ids = await self._state_handler.get_current_state_ids( event.room_id, latest_event_ids=extrem_ids ) logger.debug( "Doing soft-fail check for %s: state %s", event.event_id, current_state_ids, ) # Now check if event pass auth against said current state auth_types = auth_types_for_event(room_version_obj, event) current_state_ids_list = [ e for k, e in current_state_ids.items() if k in auth_types ] auth_events_map = await self._store.get_events(current_state_ids_list) current_auth_events = { (e.type, e.state_key): e for e in auth_events_map.values() } try: event_auth.check(room_version_obj, event, auth_events=current_auth_events) except AuthError as e: logger.warning( "Soft-failing %r (from %s) because %s", event, e, origin, extra={ "room_id": event.room_id, "mxid": event.sender, "hs": origin, }, ) soft_failed_event_counter.inc() event.internal_metadata.soft_failed = True async def _update_auth_events_and_context_for_auth( self, origin: str, event: EventBase, context: EventContext, input_auth_events: StateMap[EventBase], ) -> Tuple[EventContext, StateMap[EventBase]]: """Helper for _check_event_auth. See there for docs. Checks whether a given event has the expected auth events. If it doesn't then we talk to the remote server to compare state to see if we can come to a consensus (e.g. if one server missed some valid state). This attempts to resolve any potential divergence of state between servers, but is not essential and so failures should not block further processing of the event. Args: origin: event: context: input_auth_events: Map from (event_type, state_key) to event Normally, our calculated auth_events based on the state of the room at the event's position in the DAG, though occasionally (eg if the event is an outlier), may be the auth events claimed by the remote server. Returns: updated context, updated auth event map """ # take a copy of input_auth_events before we modify it. auth_events: MutableStateMap[EventBase] = dict(input_auth_events) event_auth_events = set(event.auth_event_ids()) # missing_auth is the set of the event's auth_events which we don't yet have # in auth_events. missing_auth = event_auth_events.difference( e.event_id for e in auth_events.values() ) # if we have missing events, we need to fetch those events from somewhere. # # we start by checking if they are in the store, and then try calling /event_auth/. if missing_auth: have_events = await self._store.have_seen_events( event.room_id, missing_auth ) logger.debug("Events %s are in the store", have_events) missing_auth.difference_update(have_events) if missing_auth: # If we don't have all the auth events, we need to get them. logger.info("auth_events contains unknown events: %s", missing_auth) try: await self._get_remote_auth_chain_for_event( origin, event.room_id, event.event_id ) except Exception: logger.exception("Failed to get auth chain") else: # load any auth events we might have persisted from the database. This # has the side-effect of correctly setting the rejected_reason on them. auth_events.update( { (ae.type, ae.state_key): ae for ae in await self._store.get_events_as_list( missing_auth, allow_rejected=True ) } ) if event.internal_metadata.is_outlier(): # XXX: given that, for an outlier, we'll be working with the # event's *claimed* auth events rather than those we calculated: # (a) is there any point in this test, since different_auth below will # obviously be empty # (b) alternatively, why don't we do it earlier? logger.info("Skipping auth_event fetch for outlier") return context, auth_events different_auth = event_auth_events.difference( e.event_id for e in auth_events.values() ) if not different_auth: return context, auth_events logger.info( "auth_events refers to events which are not in our calculated auth " "chain: %s", different_auth, ) # XXX: currently this checks for redactions but I'm not convinced that is # necessary? different_events = await self._store.get_events_as_list(different_auth) for d in different_events: if d.room_id != event.room_id: logger.warning( "Event %s refers to auth_event %s which is in a different room", event.event_id, d.event_id, ) # don't attempt to resolve the claimed auth events against our own # in this case: just use our own auth events. # # XXX: should we reject the event in this case? It feels like we should, # but then shouldn't we also do so if we've failed to fetch any of the # auth events? return context, auth_events # now we state-resolve between our own idea of the auth events, and the remote's # idea of them. local_state = auth_events.values() remote_auth_events = dict(auth_events) remote_auth_events.update({(d.type, d.state_key): d for d in different_events}) remote_state = remote_auth_events.values() room_version = await self._store.get_room_version_id(event.room_id) new_state = await self._state_handler.resolve_events( room_version, (local_state, remote_state), event ) logger.info( "After state res: updating auth_events with new state %s", { (d.type, d.state_key): d.event_id for d in new_state.values() if auth_events.get((d.type, d.state_key)) != d }, ) auth_events.update(new_state) context = await self._update_context_for_auth_events( event, context, auth_events ) return context, auth_events async def _get_remote_auth_chain_for_event( self, destination: str, room_id: str, event_id: str ) -> None: """If we are missing some of an event's auth events, attempt to request them Args: destination: where to fetch the auth tree from room_id: the room in which we are lacking auth events event_id: the event for which we are lacking auth events """ try: remote_auth_chain = await self._federation_client.get_event_auth( destination, room_id, event_id ) except RequestSendFailed as e1: # The other side isn't around or doesn't implement the # endpoint, so lets just bail out. logger.info("Failed to get event auth from remote: %s", e1) return seen_remotes = await self._store.have_seen_events( room_id, [e.event_id for e in remote_auth_chain] ) for auth_event in remote_auth_chain: if auth_event.event_id in seen_remotes: continue if auth_event.event_id == event_id: continue try: auth_ids = auth_event.auth_event_ids() auth = { (e.type, e.state_key): e for e in remote_auth_chain if e.event_id in auth_ids or e.type == EventTypes.Create } auth_event.internal_metadata.outlier = True logger.debug( "_check_event_auth %s missing_auth: %s", event_id, auth_event.event_id, ) missing_auth_event_context = EventContext.for_outlier() missing_auth_event_context = await self._check_event_auth( destination, auth_event, missing_auth_event_context, claimed_auth_event_map=auth, ) await self.persist_events_and_notify( room_id, [(auth_event, missing_auth_event_context)], ) except AuthError: pass async def _update_context_for_auth_events( self, event: EventBase, context: EventContext, auth_events: StateMap[EventBase] ) -> EventContext: """Update the state_ids in an event context after auth event resolution, storing the changes as a new state group. Args: event: The event we're handling the context for context: initial event context auth_events: Events to update in the event context. Returns: new event context """ # exclude the state key of the new event from the current_state in the context. if event.is_state(): event_key: Optional[Tuple[str, str]] = (event.type, event.state_key) else: event_key = None state_updates = { k: a.event_id for k, a in auth_events.items() if k != event_key } current_state_ids = await context.get_current_state_ids() current_state_ids = dict(current_state_ids) # type: ignore current_state_ids.update(state_updates) prev_state_ids = await context.get_prev_state_ids() prev_state_ids = dict(prev_state_ids) prev_state_ids.update({k: a.event_id for k, a in auth_events.items()}) # create a new state group as a delta from the existing one. prev_group = context.state_group state_group = await self._state_store.store_state_group( event.event_id, event.room_id, prev_group=prev_group, delta_ids=state_updates, current_state_ids=current_state_ids, ) return EventContext.with_state( state_group=state_group, state_group_before_event=context.state_group_before_event, current_state_ids=current_state_ids, prev_state_ids=prev_state_ids, prev_group=prev_group, delta_ids=state_updates, ) async def _run_push_actions_and_persist_event( self, event: EventBase, context: EventContext, backfilled: bool = False ) -> None: """Run the push actions for a received event, and persist it. Args: event: The event itself. context: The event context. backfilled: True if the event was backfilled. """ # this method should not be called on outliers (those code paths call # persist_events_and_notify directly.) assert not event.internal_metadata.outlier try: if ( not backfilled and not context.rejected and (await self._store.get_min_depth(event.room_id)) <= event.depth ): await self._action_generator.handle_push_actions_for_event( event, context ) await self.persist_events_and_notify( event.room_id, [(event, context)], backfilled=backfilled ) except Exception: run_in_background( self._store.remove_push_actions_from_staging, event.event_id ) raise async def persist_events_and_notify( self, room_id: str, event_and_contexts: Sequence[Tuple[EventBase, EventContext]], backfilled: bool = False, ) -> int: """Persists events and tells the notifier/pushers about them, if necessary. Args: room_id: The room ID of events being persisted. event_and_contexts: Sequence of events with their associated context that should be persisted. All events must belong to the same room. backfilled: Whether these events are a result of backfilling or not Returns: The stream ID after which all events have been persisted. """ if not event_and_contexts: return self._store.get_current_events_token() instance = self._config.worker.events_shard_config.get_instance(room_id) if instance != self._instance_name: # Limit the number of events sent over replication. We choose 200 # here as that is what we default to in `max_request_body_size(..)` for batch in batch_iter(event_and_contexts, 200): result = await self._send_events( instance_name=instance, store=self._store, room_id=room_id, event_and_contexts=batch, backfilled=backfilled, ) return result["max_stream_id"] else: assert self._storage.persistence # Note that this returns the events that were persisted, which may not be # the same as were passed in if some were deduplicated due to transaction IDs. events, max_stream_token = await self._storage.persistence.persist_events( event_and_contexts, backfilled=backfilled ) if self._ephemeral_messages_enabled: for event in events: # If there's an expiry timestamp on the event, schedule its expiry. self._message_handler.maybe_schedule_expiry(event) if not backfilled: # Never notify for backfilled events for event in events: await self._notify_persisted_event(event, max_stream_token) return max_stream_token.stream async def _notify_persisted_event( self, event: EventBase, max_stream_token: RoomStreamToken ) -> None: """Checks to see if notifier/pushers should be notified about the event or not. Args: event: max_stream_token: The max_stream_id returned by persist_events """ extra_users = [] if event.type == EventTypes.Member: target_user_id = event.state_key # We notify for memberships if its an invite for one of our # users if event.internal_metadata.is_outlier(): if event.membership != Membership.INVITE: if not self._is_mine_id(target_user_id): return target_user = UserID.from_string(target_user_id) extra_users.append(target_user) elif event.internal_metadata.is_outlier(): return # the event has been persisted so it should have a stream ordering. assert event.internal_metadata.stream_ordering event_pos = PersistedEventPosition( self._instance_name, event.internal_metadata.stream_ordering ) self._notifier.on_new_room_event( event, event_pos, max_stream_token, extra_users=extra_users ) def _sanity_check_event(self, ev: EventBase) -> None: """ Do some early sanity checks of a received event In particular, checks it doesn't have an excessive number of prev_events or auth_events, which could cause a huge state resolution or cascade of event fetches. Args: ev: event to be checked Raises: SynapseError if the event does not pass muster """ if len(ev.prev_event_ids()) > 20: logger.warning( "Rejecting event %s which has %i prev_events", ev.event_id, len(ev.prev_event_ids()), ) raise SynapseError(HTTPStatus.BAD_REQUEST, "Too many prev_events") if len(ev.auth_event_ids()) > 10: logger.warning( "Rejecting event %s which has %i auth_events", ev.event_id, len(ev.auth_event_ids()), ) raise SynapseError(HTTPStatus.BAD_REQUEST, "Too many auth_events") async def get_min_depth_for_context(self, context: str) -> int: return await self._store.get_min_depth(context)