# Copyright 2014-2022 The Matrix.org Foundation C.I.C. # Copyright 2020 Sorunome # # 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. """Contains handlers for federation events.""" import enum import itertools import logging from enum import Enum from http import HTTPStatus from typing import TYPE_CHECKING, Dict, Iterable, List, Optional, Tuple, Union import attr from signedjson.key import decode_verify_key_bytes from signedjson.sign import verify_signed_json from unpaddedbase64 import decode_base64 from synapse import event_auth from synapse.api.constants import EventContentFields, EventTypes, Membership from synapse.api.errors import ( AuthError, CodeMessageException, Codes, FederationDeniedError, HttpResponseException, NotFoundError, RequestSendFailed, SynapseError, ) from synapse.api.room_versions import KNOWN_ROOM_VERSIONS, RoomVersion from synapse.crypto.event_signing import compute_event_signature from synapse.event_auth import validate_event_for_room_version from synapse.events import EventBase from synapse.events.snapshot import EventContext from synapse.events.validator import EventValidator from synapse.federation.federation_client import InvalidResponseError from synapse.http.servlet import assert_params_in_dict from synapse.logging.context import nested_logging_context from synapse.metrics.background_process_metrics import run_as_background_process from synapse.replication.http.federation import ( ReplicationCleanRoomRestServlet, ReplicationStoreRoomOnOutlierMembershipRestServlet, ) from synapse.storage.databases.main.events_worker import EventRedactBehaviour from synapse.types import JsonDict, StateMap, get_domain_from_id from synapse.util.async_helpers import Linearizer from synapse.util.retryutils import NotRetryingDestination from synapse.visibility import filter_events_for_server if TYPE_CHECKING: from synapse.server import HomeServer logger = logging.getLogger(__name__) def get_domains_from_state(state: StateMap[EventBase]) -> List[Tuple[str, int]]: """Get joined domains from state Args: state: State map from type/state key to event. Returns: Returns a list of servers with the lowest depth of their joins. Sorted by lowest depth first. """ joined_users = [ (state_key, int(event.depth)) for (e_type, state_key), event in state.items() if e_type == EventTypes.Member and event.membership == Membership.JOIN ] joined_domains: Dict[str, int] = {} for u, d in joined_users: try: dom = get_domain_from_id(u) old_d = joined_domains.get(dom) if old_d: joined_domains[dom] = min(d, old_d) else: joined_domains[dom] = d except Exception: pass return sorted(joined_domains.items(), key=lambda d: d[1]) class _BackfillPointType(Enum): # a regular backwards extremity (ie, an event which we don't yet have, but which # is referred to by other events in the DAG) BACKWARDS_EXTREMITY = enum.auto() # an MSC2716 "insertion event" INSERTION_PONT = enum.auto() @attr.s(slots=True, auto_attribs=True, frozen=True) class _BackfillPoint: """A potential point we might backfill from""" event_id: str depth: int type: _BackfillPointType class FederationHandler: """Handles general incoming federation requests Incoming events are *not* handled here, for which see FederationEventHandler. """ def __init__(self, hs: "HomeServer"): self.hs = hs self.store = hs.get_datastores().main self.storage = hs.get_storage() self.state_store = self.storage.state self.federation_client = hs.get_federation_client() self.state_handler = hs.get_state_handler() self.server_name = hs.hostname self.keyring = hs.get_keyring() self.is_mine_id = hs.is_mine_id self.spam_checker = hs.get_spam_checker() self.event_creation_handler = hs.get_event_creation_handler() self.event_builder_factory = hs.get_event_builder_factory() self._event_auth_handler = hs.get_event_auth_handler() self._server_notices_mxid = hs.config.servernotices.server_notices_mxid self.config = hs.config self.http_client = hs.get_proxied_blacklisted_http_client() self._replication = hs.get_replication_data_handler() self._federation_event_handler = hs.get_federation_event_handler() self._clean_room_for_join_client = ReplicationCleanRoomRestServlet.make_client( hs ) if hs.config.worker.worker_app: self._maybe_store_room_on_outlier_membership = ( ReplicationStoreRoomOnOutlierMembershipRestServlet.make_client(hs) ) else: self._maybe_store_room_on_outlier_membership = ( self.store.maybe_store_room_on_outlier_membership ) self._room_backfill = Linearizer("room_backfill") self.third_party_event_rules = hs.get_third_party_event_rules() async def maybe_backfill( self, room_id: str, current_depth: int, limit: int ) -> bool: """Checks the database to see if we should backfill before paginating, and if so do. Args: room_id current_depth: The depth from which we're paginating from. This is used to decide if we should backfill and what extremities to use. limit: The number of events that the pagination request will return. This is used as part of the heuristic to decide if we should back paginate. """ async with self._room_backfill.queue(room_id): return await self._maybe_backfill_inner(room_id, current_depth, limit) async def _maybe_backfill_inner( self, room_id: str, current_depth: int, limit: int ) -> bool: backwards_extremities = [ _BackfillPoint(event_id, depth, _BackfillPointType.BACKWARDS_EXTREMITY) for event_id, depth in await self.store.get_oldest_event_ids_with_depth_in_room( room_id ) ] insertion_events_to_be_backfilled: List[_BackfillPoint] = [] if self.hs.config.experimental.msc2716_enabled: insertion_events_to_be_backfilled = [ _BackfillPoint(event_id, depth, _BackfillPointType.INSERTION_PONT) for event_id, depth in await self.store.get_insertion_event_backward_extremities_in_room( room_id ) ] logger.debug( "_maybe_backfill_inner: backwards_extremities=%s insertion_events_to_be_backfilled=%s", backwards_extremities, insertion_events_to_be_backfilled, ) if not backwards_extremities and not insertion_events_to_be_backfilled: logger.debug("Not backfilling as no extremeties found.") return False # we now have a list of potential places to backpaginate from. We prefer to # start with the most recent (ie, max depth), so let's sort the list. sorted_backfill_points: List[_BackfillPoint] = sorted( itertools.chain( backwards_extremities, insertion_events_to_be_backfilled, ), key=lambda e: -int(e.depth), ) logger.debug( "_maybe_backfill_inner: room_id: %s: current_depth: %s, limit: %s, " "backfill points (%d): %s", room_id, current_depth, limit, len(sorted_backfill_points), sorted_backfill_points, ) # If we're approaching an extremity we trigger a backfill, otherwise we # no-op. # # We chose twice the limit here as then clients paginating backwards # will send pagination requests that trigger backfill at least twice # using the most recent extremity before it gets removed (see below). We # chose more than one times the limit in case of failure, but choosing a # much larger factor will result in triggering a backfill request much # earlier than necessary. # # XXX: shouldn't we do this *after* the filter by depth below? Again, we don't # care about events that have happened after our current position. # max_depth = sorted_backfill_points[0].depth if current_depth - 2 * limit > max_depth: logger.debug( "Not backfilling as we don't need to. %d < %d - 2 * %d", max_depth, current_depth, limit, ) return False # We ignore extremities that have a greater depth than our current depth # as: # 1. we don't really care about getting events that have happened # after our current position; and # 2. we have likely previously tried and failed to backfill from that # extremity, so to avoid getting "stuck" requesting the same # backfill repeatedly we drop those extremities. # # However, we need to check that the filtered extremities are non-empty. # If they are empty then either we can a) bail or b) still attempt to # backfill. We opt to try backfilling anyway just in case we do get # relevant events. # filtered_sorted_backfill_points = [ t for t in sorted_backfill_points if t.depth <= current_depth ] if filtered_sorted_backfill_points: logger.debug( "_maybe_backfill_inner: backfill points before current depth: %s", filtered_sorted_backfill_points, ) sorted_backfill_points = filtered_sorted_backfill_points else: logger.debug( "_maybe_backfill_inner: all backfill points are *after* current depth. Backfilling anyway." ) # For performance's sake, we only want to paginate from a particular extremity # if we can actually see the events we'll get. Otherwise, we'd just spend a lot # of resources to get redacted events. We check each extremity in turn and # ignore those which users on our server wouldn't be able to see. # # Additionally, we limit ourselves to backfilling from at most 5 extremities, # for two reasons: # # - The check which determines if we can see an extremity's events can be # expensive (we load the full state for the room at each of the backfill # points, or (worse) their successors) # - We want to avoid the server-server API request URI becoming too long. # # *Note*: the spec wants us to keep backfilling until we reach the start # of the room in case we are allowed to see some of the history. However, # in practice that causes more issues than its worth, as (a) it's # relatively rare for there to be any visible history and (b) even when # there is it's often sufficiently long ago that clients would stop # attempting to paginate before backfill reached the visible history. extremities_to_request: List[str] = [] for bp in sorted_backfill_points: if len(extremities_to_request) >= 5: break # For regular backwards extremities, we don't have the extremity events # themselves, so we need to actually check the events that reference them - # their "successor" events. # # TODO: Correctly handle the case where we are allowed to see the # successor event but not the backward extremity, e.g. in the case of # initial join of the server where we are allowed to see the join # event but not anything before it. This would require looking at the # state *before* the event, ignoring the special casing certain event # types have. if bp.type == _BackfillPointType.INSERTION_PONT: event_ids_to_check = [bp.event_id] else: event_ids_to_check = await self.store.get_successor_events(bp.event_id) events_to_check = await self.store.get_events_as_list( event_ids_to_check, redact_behaviour=EventRedactBehaviour.as_is, get_prev_content=False, ) # We set `check_history_visibility_only` as we might otherwise get false # positives from users having been erased. filtered_extremities = await filter_events_for_server( self.storage, self.server_name, events_to_check, redact=False, check_history_visibility_only=True, ) if filtered_extremities: extremities_to_request.append(bp.event_id) else: logger.debug( "_maybe_backfill_inner: skipping extremity %s as it would not be visible", bp, ) if not extremities_to_request: logger.debug( "_maybe_backfill_inner: found no extremities which would be visible" ) return False logger.debug( "_maybe_backfill_inner: extremities_to_request %s", extremities_to_request ) # Now we need to decide which hosts to hit first. # First we try hosts that are already in the room # TODO: HEURISTIC ALERT. curr_state = await self.state_handler.get_current_state(room_id) curr_domains = get_domains_from_state(curr_state) likely_domains = [ domain for domain, depth in curr_domains if domain != self.server_name ] async def try_backfill(domains: List[str]) -> bool: # TODO: Should we try multiple of these at a time? for dom in domains: try: await self._federation_event_handler.backfill( dom, room_id, limit=100, extremities=extremities_to_request ) # If this succeeded then we probably already have the # appropriate stuff. # TODO: We can probably do something more intelligent here. return True except (SynapseError, InvalidResponseError) as e: logger.info("Failed to backfill from %s because %s", dom, e) continue except HttpResponseException as e: if 400 <= e.code < 500: raise e.to_synapse_error() logger.info("Failed to backfill from %s because %s", dom, e) continue except CodeMessageException as e: if 400 <= e.code < 500: raise logger.info("Failed to backfill from %s because %s", dom, e) continue except NotRetryingDestination as e: logger.info(str(e)) continue except RequestSendFailed as e: logger.info("Failed to get backfill from %s because %s", dom, e) continue except FederationDeniedError as e: logger.info(e) continue except Exception as e: logger.exception("Failed to backfill from %s because %s", dom, e) continue return False success = await try_backfill(likely_domains) if success: return True # TODO: we could also try servers which were previously in the room, but # are no longer. return False async def send_invite(self, target_host: str, event: EventBase) -> EventBase: """Sends the invite to the remote server for signing. Invites must be signed by the invitee's server before distribution. """ try: pdu = await self.federation_client.send_invite( destination=target_host, room_id=event.room_id, event_id=event.event_id, pdu=event, ) except RequestSendFailed: raise SynapseError(502, f"Can't connect to server {target_host}") return pdu async def on_event_auth(self, event_id: str) -> List[EventBase]: event = await self.store.get_event(event_id) auth = await self.store.get_auth_chain( event.room_id, list(event.auth_event_ids()), include_given=True ) return list(auth) async def do_invite_join( self, target_hosts: Iterable[str], room_id: str, joinee: str, content: JsonDict ) -> Tuple[str, int]: """Attempts to join the `joinee` to the room `room_id` via the servers contained in `target_hosts`. This first triggers a /make_join/ request that returns a partial event that we can fill out and sign. This is then sent to the remote server via /send_join/ which responds with the state at that event and the auth_chains. We suspend processing of any received events from this room until we have finished processing the join. Args: target_hosts: List of servers to attempt to join the room with. room_id: The ID of the room to join. joinee: The User ID of the joining user. content: The event content to use for the join event. """ # TODO: We should be able to call this on workers, but the upgrading of # room stuff after join currently doesn't work on workers. assert self.config.worker.worker_app is None logger.debug("Joining %s to %s", joinee, room_id) origin, event, room_version_obj = await self._make_and_verify_event( target_hosts, room_id, joinee, "join", content, params={"ver": KNOWN_ROOM_VERSIONS}, ) # This shouldn't happen, because the RoomMemberHandler has a # linearizer lock which only allows one operation per user per room # at a time - so this is just paranoia. assert room_id not in self._federation_event_handler.room_queues self._federation_event_handler.room_queues[room_id] = [] await self._clean_room_for_join(room_id) try: # Try the host we successfully got a response to /make_join/ # request first. host_list = list(target_hosts) try: host_list.remove(origin) host_list.insert(0, origin) except ValueError: pass ret = await self.federation_client.send_join( host_list, event, room_version_obj ) event = ret.event origin = ret.origin state = ret.state auth_chain = ret.auth_chain auth_chain.sort(key=lambda e: e.depth) logger.debug("do_invite_join auth_chain: %s", auth_chain) logger.debug("do_invite_join state: %s", state) logger.debug("do_invite_join event: %s", event) # if this is the first time we've joined this room, it's time to add # a row to `rooms` with the correct room version. If there's already a # row there, we should override it, since it may have been populated # based on an invite request which lied about the room version. # # federation_client.send_join has already checked that the room # version in the received create event is the same as room_version_obj, # so we can rely on it now. # await self.store.upsert_room_on_join( room_id=room_id, room_version=room_version_obj, state_events=state, ) if ret.partial_state: # TODO(faster_joins): roll this back if we don't manage to start the # background resync (eg process_remote_join fails) await self.store.store_partial_state_room(room_id, ret.servers_in_room) max_stream_id = await self._federation_event_handler.process_remote_join( origin, room_id, auth_chain, state, event, room_version_obj, partial_state=ret.partial_state, ) if ret.partial_state: # Kick off the process of asynchronously fetching the state for this # room. # # TODO(faster_joins): pick this up again on restart run_as_background_process( desc="sync_partial_state_room", func=self._sync_partial_state_room, destination=origin, room_id=room_id, ) # We wait here until this instance has seen the events come down # replication (if we're using replication) as the below uses caches. await self._replication.wait_for_stream_position( self.config.worker.events_shard_config.get_instance(room_id), "events", max_stream_id, ) # Check whether this room is the result of an upgrade of a room we already know # about. If so, migrate over user information predecessor = await self.store.get_room_predecessor(room_id) if not predecessor or not isinstance(predecessor.get("room_id"), str): return event.event_id, max_stream_id old_room_id = predecessor["room_id"] logger.debug( "Found predecessor for %s during remote join: %s", room_id, old_room_id ) # We retrieve the room member handler here as to not cause a cyclic dependency member_handler = self.hs.get_room_member_handler() await member_handler.transfer_room_state_on_room_upgrade( old_room_id, room_id ) logger.debug("Finished joining %s to %s", joinee, room_id) return event.event_id, max_stream_id finally: room_queue = self._federation_event_handler.room_queues[room_id] del self._federation_event_handler.room_queues[room_id] # we don't need to wait for the queued events to be processed - # it's just a best-effort thing at this point. We do want to do # them roughly in order, though, otherwise we'll end up making # lots of requests for missing prev_events which we do actually # have. Hence we fire off the background task, but don't wait for it. run_as_background_process( "handle_queued_pdus", self._handle_queued_pdus, room_queue ) async def do_knock( self, target_hosts: List[str], room_id: str, knockee: str, content: JsonDict, ) -> Tuple[str, int]: """Sends the knock to the remote server. This first triggers a make_knock request that returns a partial event that we can fill out and sign. This is then sent to the remote server via send_knock. Knock events must be signed by the knockee's server before distributing. Args: target_hosts: A list of hosts that we want to try knocking through. room_id: The ID of the room to knock on. knockee: The ID of the user who is knocking. content: The content of the knock event. Returns: A tuple of (event ID, stream ID). Raises: SynapseError: If the chosen remote server returns a 3xx/4xx code. RuntimeError: If no servers were reachable. """ logger.debug("Knocking on room %s on behalf of user %s", room_id, knockee) # Inform the remote server of the room versions we support supported_room_versions = list(KNOWN_ROOM_VERSIONS.keys()) # Ask the remote server to create a valid knock event for us. Once received, # we sign the event params: Dict[str, Iterable[str]] = {"ver": supported_room_versions} origin, event, event_format_version = await self._make_and_verify_event( target_hosts, room_id, knockee, Membership.KNOCK, content, params=params ) # Mark the knock as an outlier as we don't yet have the state at this point in # the DAG. event.internal_metadata.outlier = True # ... but tell /sync to send it to clients anyway. event.internal_metadata.out_of_band_membership = True # Record the room ID and its version so that we have a record of the room await self._maybe_store_room_on_outlier_membership( room_id=event.room_id, room_version=event_format_version ) # Initially try the host that we successfully called /make_knock on try: target_hosts.remove(origin) target_hosts.insert(0, origin) except ValueError: pass # Send the signed event back to the room, and potentially receive some # further information about the room in the form of partial state events stripped_room_state = await self.federation_client.send_knock( target_hosts, event ) # Store any stripped room state events in the "unsigned" key of the event. # This is a bit of a hack and is cribbing off of invites. Basically we # store the room state here and retrieve it again when this event appears # in the invitee's sync stream. It is stripped out for all other local users. event.unsigned["knock_room_state"] = stripped_room_state["knock_state_events"] context = EventContext.for_outlier(self.storage) stream_id = await self._federation_event_handler.persist_events_and_notify( event.room_id, [(event, context)] ) return event.event_id, stream_id async def _handle_queued_pdus( self, room_queue: List[Tuple[EventBase, str]] ) -> None: """Process PDUs which got queued up while we were busy send_joining. Args: room_queue: list of PDUs to be processed and the servers that sent them """ for p, origin in room_queue: try: logger.info( "Processing queued PDU %s which was received while we were joining", p, ) with nested_logging_context(p.event_id): await self._federation_event_handler.on_receive_pdu(origin, p) except Exception as e: logger.warning( "Error handling queued PDU %s from %s: %s", p.event_id, origin, e ) async def on_make_join_request( self, origin: str, room_id: str, user_id: str ) -> EventBase: """We've received a /make_join/ request, so we create a partial join event for the room and return that. We do *not* persist or process it until the other server has signed it and sent it back. Args: origin: The (verified) server name of the requesting server. room_id: Room to create join event in user_id: The user to create the join for """ if get_domain_from_id(user_id) != origin: logger.info( "Got /make_join request for user %r from different origin %s, ignoring", user_id, origin, ) raise SynapseError(403, "User not from origin", Codes.FORBIDDEN) # checking the room version will check that we've actually heard of the room # (and return a 404 otherwise) room_version = await self.store.get_room_version(room_id) # now check that we are *still* in the room is_in_room = await self._event_auth_handler.check_host_in_room( room_id, self.server_name ) if not is_in_room: logger.info( "Got /make_join request for room %s we are no longer in", room_id, ) raise NotFoundError("Not an active room on this server") event_content = {"membership": Membership.JOIN} # If the current room is using restricted join rules, additional information # may need to be included in the event content in order to efficiently # validate the event. # # Note that this requires the /send_join request to come back to the # same server. if room_version.msc3083_join_rules: state_ids = await self.store.get_current_state_ids(room_id) if await self._event_auth_handler.has_restricted_join_rules( state_ids, room_version ): prev_member_event_id = state_ids.get((EventTypes.Member, user_id), None) # If the user is invited or joined to the room already, then # no additional info is needed. include_auth_user_id = True if prev_member_event_id: prev_member_event = await self.store.get_event(prev_member_event_id) include_auth_user_id = prev_member_event.membership not in ( Membership.JOIN, Membership.INVITE, ) if include_auth_user_id: event_content[ EventContentFields.AUTHORISING_USER ] = await self._event_auth_handler.get_user_which_could_invite( room_id, state_ids, ) builder = self.event_builder_factory.for_room_version( room_version, { "type": EventTypes.Member, "content": event_content, "room_id": room_id, "sender": user_id, "state_key": user_id, }, ) try: event, context = await self.event_creation_handler.create_new_client_event( builder=builder ) except SynapseError as e: logger.warning("Failed to create join to %s because %s", room_id, e) raise # Ensure the user can even join the room. await self._federation_event_handler.check_join_restrictions(context, event) # The remote hasn't signed it yet, obviously. We'll do the full checks # when we get the event back in `on_send_join_request` await self._event_auth_handler.check_auth_rules_from_context( room_version, event, context ) return event async def on_invite_request( self, origin: str, event: EventBase, room_version: RoomVersion ) -> EventBase: """We've got an invite event. Process and persist it. Sign it. Respond with the now signed event. """ if event.state_key is None: raise SynapseError(400, "The invite event did not have a state key") is_blocked = await self.store.is_room_blocked(event.room_id) if is_blocked: raise SynapseError(403, "This room has been blocked on this server") if self.hs.config.server.block_non_admin_invites: raise SynapseError(403, "This server does not accept room invites") if not await self.spam_checker.user_may_invite( event.sender, event.state_key, event.room_id ): raise SynapseError( 403, "This user is not permitted to send invites to this server/user" ) membership = event.content.get("membership") if event.type != EventTypes.Member or membership != Membership.INVITE: raise SynapseError(400, "The event was not an m.room.member invite event") sender_domain = get_domain_from_id(event.sender) if sender_domain != origin: raise SynapseError( 400, "The invite event was not from the server sending it" ) if not self.is_mine_id(event.state_key): raise SynapseError(400, "The invite event must be for this server") # block any attempts to invite the server notices mxid if event.state_key == self._server_notices_mxid: raise SynapseError(HTTPStatus.FORBIDDEN, "Cannot invite this user") # We retrieve the room member handler here as to not cause a cyclic dependency member_handler = self.hs.get_room_member_handler() # We don't rate limit based on room ID, as that should be done by # sending server. await member_handler.ratelimit_invite(None, None, event.state_key) # keep a record of the room version, if we don't yet know it. # (this may get overwritten if we later get a different room version in a # join dance). await self._maybe_store_room_on_outlier_membership( room_id=event.room_id, room_version=room_version ) event.internal_metadata.outlier = True event.internal_metadata.out_of_band_membership = True event.signatures.update( compute_event_signature( room_version, event.get_pdu_json(), self.hs.hostname, self.hs.signing_key, ) ) context = EventContext.for_outlier(self.storage) await self._federation_event_handler.persist_events_and_notify( event.room_id, [(event, context)] ) return event async def do_remotely_reject_invite( self, target_hosts: Iterable[str], room_id: str, user_id: str, content: JsonDict ) -> Tuple[EventBase, int]: origin, event, room_version = await self._make_and_verify_event( target_hosts, room_id, user_id, "leave", content=content ) # Mark as outlier as we don't have any state for this event; we're not # even in the room. event.internal_metadata.outlier = True event.internal_metadata.out_of_band_membership = True # Try the host that we successfully called /make_leave/ on first for # the /send_leave/ request. host_list = list(target_hosts) try: host_list.remove(origin) host_list.insert(0, origin) except ValueError: pass await self.federation_client.send_leave(host_list, event) context = EventContext.for_outlier(self.storage) stream_id = await self._federation_event_handler.persist_events_and_notify( event.room_id, [(event, context)] ) return event, stream_id async def _make_and_verify_event( self, target_hosts: Iterable[str], room_id: str, user_id: str, membership: str, content: JsonDict, params: Optional[Dict[str, Union[str, Iterable[str]]]] = None, ) -> Tuple[str, EventBase, RoomVersion]: ( origin, event, room_version, ) = await self.federation_client.make_membership_event( target_hosts, room_id, user_id, membership, content, params=params ) logger.debug("Got response to make_%s: %s", membership, event) # We should assert some things. # FIXME: Do this in a nicer way assert event.type == EventTypes.Member assert event.user_id == user_id assert event.state_key == user_id assert event.room_id == room_id return origin, event, room_version async def on_make_leave_request( self, origin: str, room_id: str, user_id: str ) -> EventBase: """We've received a /make_leave/ request, so we create a partial leave event for the room and return that. We do *not* persist or process it until the other server has signed it and sent it back. Args: origin: The (verified) server name of the requesting server. room_id: Room to create leave event in user_id: The user to create the leave for """ if get_domain_from_id(user_id) != origin: logger.info( "Got /make_leave request for user %r from different origin %s, ignoring", user_id, origin, ) raise SynapseError(403, "User not from origin", Codes.FORBIDDEN) room_version_obj = await self.store.get_room_version(room_id) builder = self.event_builder_factory.for_room_version( room_version_obj, { "type": EventTypes.Member, "content": {"membership": Membership.LEAVE}, "room_id": room_id, "sender": user_id, "state_key": user_id, }, ) event, context = await self.event_creation_handler.create_new_client_event( builder=builder ) try: # The remote hasn't signed it yet, obviously. We'll do the full checks # when we get the event back in `on_send_leave_request` await self._event_auth_handler.check_auth_rules_from_context( room_version_obj, event, context ) except AuthError as e: logger.warning("Failed to create new leave %r because %s", event, e) raise e return event async def on_make_knock_request( self, origin: str, room_id: str, user_id: str ) -> EventBase: """We've received a make_knock request, so we create a partial knock event for the room and return that. We do *not* persist or process it until the other server has signed it and sent it back. Args: origin: The (verified) server name of the requesting server. room_id: The room to create the knock event in. user_id: The user to create the knock for. Returns: The partial knock event. """ if get_domain_from_id(user_id) != origin: logger.info( "Get /make_knock request for user %r from different origin %s, ignoring", user_id, origin, ) raise SynapseError(403, "User not from origin", Codes.FORBIDDEN) room_version_obj = await self.store.get_room_version(room_id) builder = self.event_builder_factory.for_room_version( room_version_obj, { "type": EventTypes.Member, "content": {"membership": Membership.KNOCK}, "room_id": room_id, "sender": user_id, "state_key": user_id, }, ) event, context = await self.event_creation_handler.create_new_client_event( builder=builder ) event_allowed, _ = await self.third_party_event_rules.check_event_allowed( event, context ) if not event_allowed: logger.warning("Creation of knock %s forbidden by third-party rules", event) raise SynapseError( 403, "This event is not allowed in this context", Codes.FORBIDDEN ) try: # The remote hasn't signed it yet, obviously. We'll do the full checks # when we get the event back in `on_send_knock_request` await self._event_auth_handler.check_auth_rules_from_context( room_version_obj, event, context ) except AuthError as e: logger.warning("Failed to create new knock %r because %s", event, e) raise e return event async def get_state_ids_for_pdu(self, room_id: str, event_id: str) -> List[str]: """Returns the state at the event. i.e. not including said event.""" event = await self.store.get_event(event_id, check_room_id=room_id) if event.internal_metadata.outlier: raise NotFoundError("State not known at event %s" % (event_id,)) state_groups = await self.state_store.get_state_groups_ids(room_id, [event_id]) # get_state_groups_ids should return exactly one result assert len(state_groups) == 1 state_map = next(iter(state_groups.values())) state_key = event.get_state_key() if state_key is not None: # the event was not rejected (get_event raises a NotFoundError for rejected # events) so the state at the event should include the event itself. assert ( state_map.get((event.type, state_key)) == event.event_id ), "State at event did not include event itself" # ... but we need the state *before* that event if "replaces_state" in event.unsigned: prev_id = event.unsigned["replaces_state"] state_map[(event.type, state_key)] = prev_id else: del state_map[(event.type, state_key)] return list(state_map.values()) async def on_backfill_request( self, origin: str, room_id: str, pdu_list: List[str], limit: int ) -> List[EventBase]: in_room = await self._event_auth_handler.check_host_in_room(room_id, origin) if not in_room: raise AuthError(403, "Host not in room.") # Synapse asks for 100 events per backfill request. Do not allow more. limit = min(limit, 100) events = await self.store.get_backfill_events(room_id, pdu_list, limit) logger.debug( "on_backfill_request: backfill events=%s", [ "event_id=%s,depth=%d,body=%s,prevs=%s\n" % ( event.event_id, event.depth, event.content.get("body", event.type), event.prev_event_ids(), ) for event in events ], ) events = await filter_events_for_server(self.storage, origin, events) return events async def get_persisted_pdu( self, origin: str, event_id: str ) -> Optional[EventBase]: """Get an event from the database for the given server. Args: origin: hostname of server which is requesting the event; we will check that the server is allowed to see it. event_id: id of the event being requested Returns: None if we know nothing about the event; otherwise the (possibly-redacted) event. Raises: AuthError if the server is not currently in the room """ event = await self.store.get_event( event_id, allow_none=True, allow_rejected=True ) if event: in_room = await self._event_auth_handler.check_host_in_room( event.room_id, origin ) if not in_room: raise AuthError(403, "Host not in room.") events = await filter_events_for_server(self.storage, origin, [event]) event = events[0] return event else: return None async def on_get_missing_events( self, origin: str, room_id: str, earliest_events: List[str], latest_events: List[str], limit: int, ) -> List[EventBase]: in_room = await self._event_auth_handler.check_host_in_room(room_id, origin) if not in_room: raise AuthError(403, "Host not in room.") # Only allow up to 20 events to be retrieved per request. limit = min(limit, 20) missing_events = await self.store.get_missing_events( room_id=room_id, earliest_events=earliest_events, latest_events=latest_events, limit=limit, ) missing_events = await filter_events_for_server( self.storage, origin, missing_events ) return missing_events async def exchange_third_party_invite( self, sender_user_id: str, target_user_id: str, room_id: str, signed: JsonDict ) -> None: third_party_invite = {"signed": signed} event_dict = { "type": EventTypes.Member, "content": { "membership": Membership.INVITE, "third_party_invite": third_party_invite, }, "room_id": room_id, "sender": sender_user_id, "state_key": target_user_id, } if await self._event_auth_handler.check_host_in_room(room_id, self.hs.hostname): room_version_obj = await self.store.get_room_version(room_id) builder = self.event_builder_factory.for_room_version( room_version_obj, event_dict ) EventValidator().validate_builder(builder) event, context = await self.event_creation_handler.create_new_client_event( builder=builder ) event, context = await self.add_display_name_to_third_party_invite( room_version_obj, event_dict, event, context ) EventValidator().validate_new(event, self.config) # We need to tell the transaction queue to send this out, even # though the sender isn't a local user. event.internal_metadata.send_on_behalf_of = self.hs.hostname try: validate_event_for_room_version(room_version_obj, event) await self._event_auth_handler.check_auth_rules_from_context( room_version_obj, event, context ) except AuthError as e: logger.warning("Denying new third party invite %r because %s", event, e) raise e await self._check_signature(event, context) # We retrieve the room member handler here as to not cause a cyclic dependency member_handler = self.hs.get_room_member_handler() await member_handler.send_membership_event(None, event, context) else: destinations = {x.split(":", 1)[-1] for x in (sender_user_id, room_id)} try: await self.federation_client.forward_third_party_invite( destinations, room_id, event_dict ) except (RequestSendFailed, HttpResponseException): raise SynapseError(502, "Failed to forward third party invite") async def on_exchange_third_party_invite_request( self, event_dict: JsonDict ) -> None: """Handle an exchange_third_party_invite request from a remote server The remote server will call this when it wants to turn a 3pid invite into a normal m.room.member invite. Args: event_dict: Dictionary containing the event body. """ assert_params_in_dict(event_dict, ["room_id"]) room_version_obj = await self.store.get_room_version(event_dict["room_id"]) # NB: event_dict has a particular specced format we might need to fudge # if we change event formats too much. builder = self.event_builder_factory.for_room_version( room_version_obj, event_dict ) event, context = await self.event_creation_handler.create_new_client_event( builder=builder ) event, context = await self.add_display_name_to_third_party_invite( room_version_obj, event_dict, event, context ) try: validate_event_for_room_version(room_version_obj, event) await self._event_auth_handler.check_auth_rules_from_context( room_version_obj, event, context ) except AuthError as e: logger.warning("Denying third party invite %r because %s", event, e) raise e await self._check_signature(event, context) # We need to tell the transaction queue to send this out, even # though the sender isn't a local user. event.internal_metadata.send_on_behalf_of = get_domain_from_id(event.sender) # We retrieve the room member handler here as to not cause a cyclic dependency member_handler = self.hs.get_room_member_handler() await member_handler.send_membership_event(None, event, context) async def add_display_name_to_third_party_invite( self, room_version_obj: RoomVersion, event_dict: JsonDict, event: EventBase, context: EventContext, ) -> Tuple[EventBase, EventContext]: key = ( EventTypes.ThirdPartyInvite, event.content["third_party_invite"]["signed"]["token"], ) original_invite = None prev_state_ids = await context.get_prev_state_ids() original_invite_id = prev_state_ids.get(key) if original_invite_id: original_invite = await self.store.get_event( original_invite_id, allow_none=True ) if original_invite: # If the m.room.third_party_invite event's content is empty, it means the # invite has been revoked. In this case, we don't have to raise an error here # because the auth check will fail on the invite (because it's not able to # fetch public keys from the m.room.third_party_invite event's content, which # is empty). display_name = original_invite.content.get("display_name") event_dict["content"]["third_party_invite"]["display_name"] = display_name else: logger.info( "Could not find invite event for third_party_invite: %r", event_dict ) # We don't discard here as this is not the appropriate place to do # auth checks. If we need the invite and don't have it then the # auth check code will explode appropriately. builder = self.event_builder_factory.for_room_version( room_version_obj, event_dict ) EventValidator().validate_builder(builder) event, context = await self.event_creation_handler.create_new_client_event( builder=builder ) EventValidator().validate_new(event, self.config) return event, context async def _check_signature(self, event: EventBase, context: EventContext) -> None: """ Checks that the signature in the event is consistent with its invite. Args: event: The m.room.member event to check context: Raises: AuthError: if signature didn't match any keys, or key has been revoked, SynapseError: if a transient error meant a key couldn't be checked for revocation. """ signed = event.content["third_party_invite"]["signed"] token = signed["token"] prev_state_ids = await context.get_prev_state_ids() invite_event_id = prev_state_ids.get((EventTypes.ThirdPartyInvite, token)) invite_event = None if invite_event_id: invite_event = await self.store.get_event(invite_event_id, allow_none=True) if not invite_event: raise AuthError(403, "Could not find invite") logger.debug("Checking auth on event %r", event.content) last_exception: Optional[Exception] = None # for each public key in the 3pid invite event for public_key_object in event_auth.get_public_keys(invite_event): try: # for each sig on the third_party_invite block of the actual invite for server, signature_block in signed["signatures"].items(): for key_name in signature_block.keys(): if not key_name.startswith("ed25519:"): continue logger.debug( "Attempting to verify sig with key %s from %r " "against pubkey %r", key_name, server, public_key_object, ) try: public_key = public_key_object["public_key"] verify_key = decode_verify_key_bytes( key_name, decode_base64(public_key) ) verify_signed_json(signed, server, verify_key) logger.debug( "Successfully verified sig with key %s from %r " "against pubkey %r", key_name, server, public_key_object, ) except Exception: logger.info( "Failed to verify sig with key %s from %r " "against pubkey %r", key_name, server, public_key_object, ) raise try: if "key_validity_url" in public_key_object: await self._check_key_revocation( public_key, public_key_object["key_validity_url"] ) except Exception: logger.info( "Failed to query key_validity_url %s", public_key_object["key_validity_url"], ) raise return except Exception as e: last_exception = e if last_exception is None: # we can only get here if get_public_keys() returned an empty list # TODO: make this better raise RuntimeError("no public key in invite event") raise last_exception async def _check_key_revocation(self, public_key: str, url: str) -> None: """ Checks whether public_key has been revoked. Args: public_key: base-64 encoded public key. url: Key revocation URL. Raises: AuthError: if they key has been revoked. SynapseError: if a transient error meant a key couldn't be checked for revocation. """ try: response = await self.http_client.get_json(url, {"public_key": public_key}) except Exception: raise SynapseError(502, "Third party certificate could not be checked") if "valid" not in response or not response["valid"]: raise AuthError(403, "Third party certificate was invalid") async def _clean_room_for_join(self, room_id: str) -> None: """Called to clean up any data in DB for a given room, ready for the server to join the room. Args: room_id """ if self.config.worker.worker_app: await self._clean_room_for_join_client(room_id) else: await self.store.clean_room_for_join(room_id) async def get_room_complexity( self, remote_room_hosts: List[str], room_id: str ) -> Optional[dict]: """ Fetch the complexity of a remote room over federation. Args: remote_room_hosts (list[str]): The remote servers to ask. room_id (str): The room ID to ask about. Returns: Dict contains the complexity metric versions, while None means we could not fetch the complexity. """ for host in remote_room_hosts: res = await self.federation_client.get_room_complexity(host, room_id) # We got a result, return it. if res: return res # We fell off the bottom, couldn't get the complexity from anyone. Oh # well. return None async def _sync_partial_state_room( self, destination: str, room_id: str, ) -> None: """Background process to resync the state of a partial-state room Args: destination: homeserver to pull the state from room_id: room to be resynced """ # TODO(faster_joins): do we need to lock to avoid races? What happens if other # worker processes kick off a resync in parallel? Perhaps we should just elect # a single worker to do the resync. # # TODO(faster_joins): what happens if we leave the room during a resync? if we # really leave, that might mean we have difficulty getting the room state over # federation. # # TODO(faster_joins): try other destinations if the one we have fails logger.info("Syncing state for room %s via %s", room_id, destination) # we work through the queue in order of increasing stream ordering. while True: batch = await self.store.get_partial_state_events_batch(room_id) if not batch: # all the events are updated, so we can update current state and # clear the lazy-loading flag. logger.info("Updating current state for %s", room_id) assert ( self.storage.persistence is not None ), "TODO(faster_joins): support for workers" await self.storage.persistence.update_current_state(room_id) logger.info("Clearing partial-state flag for %s", room_id) success = await self.store.clear_partial_state_room(room_id) if success: logger.info("State resync complete for %s", room_id) # TODO(faster_joins) update room stats and user directory? return # we raced against more events arriving with partial state. Go round # the loop again. We've already logged a warning, so no need for more. # TODO(faster_joins): there is still a race here, whereby incoming events which raced # with us will fail to be persisted after the call to `clear_partial_state_room` due to # having partial state. continue events = await self.store.get_events_as_list( batch, redact_behaviour=EventRedactBehaviour.as_is, allow_rejected=True, ) for event in events: await self._federation_event_handler.update_state_for_partial_state_event( destination, event )