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synced 2025-05-09 01:15:04 -04:00
Improve validation for send_{join,leave,knock} (#10225)
The idea here is to stop people sending things that aren't joins/leaves/knocks through these endpoints: previously you could send anything you liked through them. I wasn't able to find any security holes from doing so, but it doesn't sound like a good thing.
This commit is contained in:
Richard van der Hoff
GitHub
parent
bd4919fb72
commit
6e8fb42be7
6 changed files with 136 additions and 187 deletions
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@ -1711,80 +1711,6 @@ class FederationHandler(BaseHandler):
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return event
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async def on_send_join_request(self, origin: str, pdu: EventBase) -> JsonDict:
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"""We have received a join event for a room. Fully process it and
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respond with the current state and auth chains.
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"""
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event = pdu
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logger.debug(
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"on_send_join_request from %s: Got event: %s, signatures: %s",
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origin,
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event.event_id,
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event.signatures,
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)
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if get_domain_from_id(event.sender) != origin:
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logger.info(
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"Got /send_join request for user %r from different origin %s",
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event.sender,
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origin,
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)
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raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
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event.internal_metadata.outlier = False
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# Send this event on behalf of the origin server.
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#
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# The reasons we have the destination server rather than the origin
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# server send it are slightly mysterious: the origin server should have
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# all the necessary state once it gets the response to the send_join,
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# so it could send the event itself if it wanted to. It may be that
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# doing it this way reduces failure modes, or avoids certain attacks
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# where a new server selectively tells a subset of the federation that
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# it has joined.
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#
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# The fact is that, as of the current writing, Synapse doesn't send out
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# the join event over federation after joining, and changing it now
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# would introduce the danger of backwards-compatibility problems.
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event.internal_metadata.send_on_behalf_of = origin
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# Calculate the event context.
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context = await self.state_handler.compute_event_context(event)
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# Get the state before the new event.
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prev_state_ids = await context.get_prev_state_ids()
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# Check if the user is already in the room or invited to the room.
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user_id = event.state_key
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prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None)
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prev_member_event = None
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if prev_member_event_id:
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prev_member_event = await self.store.get_event(prev_member_event_id)
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# Check if the member should be allowed access via membership in a space.
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await self._event_auth_handler.check_restricted_join_rules(
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prev_state_ids,
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event.room_version,
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user_id,
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prev_member_event,
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)
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# Persist the event.
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await self._auth_and_persist_event(origin, event, context)
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logger.debug(
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"on_send_join_request: After _auth_and_persist_event: %s, sigs: %s",
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event.event_id,
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event.signatures,
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)
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state_ids = list(prev_state_ids.values())
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auth_chain = await self.store.get_auth_chain(event.room_id, state_ids)
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state = await self.store.get_events(list(prev_state_ids.values()))
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return {"state": list(state.values()), "auth_chain": auth_chain}
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async def on_invite_request(
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self, origin: str, event: EventBase, room_version: RoomVersion
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) -> EventBase:
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@ -1960,44 +1886,6 @@ class FederationHandler(BaseHandler):
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return event
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async def on_send_leave_request(self, origin: str, pdu: EventBase) -> None:
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"""We have received a leave event for a room. Fully process it."""
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event = pdu
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logger.debug(
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"on_send_leave_request: Got event: %s, signatures: %s",
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event.event_id,
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event.signatures,
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)
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if get_domain_from_id(event.sender) != origin:
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logger.info(
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"Got /send_leave request for user %r from different origin %s",
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event.sender,
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origin,
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)
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raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
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event.internal_metadata.outlier = False
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# Send this event on behalf of the other server.
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#
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# The remote server isn't a full participant in the room at this point, so
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# may not have an up-to-date list of the other homeservers participating in
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# the room, so we send it on their behalf.
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event.internal_metadata.send_on_behalf_of = origin
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context = await self.state_handler.compute_event_context(event)
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await self._auth_and_persist_event(origin, event, context)
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logger.debug(
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"on_send_leave_request: After _auth_and_persist_event: %s, sigs: %s",
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event.event_id,
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event.signatures,
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)
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return None
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@log_function
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async def on_make_knock_request(
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self, origin: str, room_id: str, user_id: str
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@ -2061,34 +1949,38 @@ class FederationHandler(BaseHandler):
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return event
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@log_function
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async def on_send_knock_request(
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async def on_send_membership_event(
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self, origin: str, event: EventBase
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) -> EventContext:
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"""
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We have received a knock event for a room. Verify that event and send it into the room
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on the knocking homeserver's behalf.
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We have received a join/leave/knock event for a room.
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Verify that event and send it into the room on the remote homeserver's behalf.
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Args:
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origin: The remote homeserver of the knocking user.
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event: The knocking member event that has been signed by the remote homeserver.
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origin: The homeserver of the remote (joining/invited/knocking) user.
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event: The member event that has been signed by the remote homeserver.
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Returns:
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The context of the event after inserting it into the room graph.
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"""
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logger.debug(
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"on_send_knock_request: Got event: %s, signatures: %s",
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"on_send_membership_event: Got event: %s, signatures: %s",
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event.event_id,
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event.signatures,
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)
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if get_domain_from_id(event.sender) != origin:
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logger.info(
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"Got /send_knock request for user %r from different origin %s",
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"Got send_membership request for user %r from different origin %s",
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event.sender,
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origin,
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)
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raise SynapseError(403, "User not from origin", Codes.FORBIDDEN)
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if event.sender != event.state_key:
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raise SynapseError(400, "state_key and sender must match", Codes.BAD_JSON)
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event.internal_metadata.outlier = False
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# Send this event on behalf of the other server.
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@ -2100,19 +1992,52 @@ class FederationHandler(BaseHandler):
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context = await self.state_handler.compute_event_context(event)
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event_allowed = await self.third_party_event_rules.check_event_allowed(
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event, context
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)
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if not event_allowed:
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logger.info("Sending of knock %s forbidden by third-party rules", event)
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raise SynapseError(
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403, "This event is not allowed in this context", Codes.FORBIDDEN
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# for joins, we need to check the restrictions of restricted rooms
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if event.membership == Membership.JOIN:
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await self._check_join_restrictions(context, event)
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# for knock events, we run the third-party event rules. It's not entirely clear
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# why we don't do this for other sorts of membership events.
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if event.membership == Membership.KNOCK:
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event_allowed = await self.third_party_event_rules.check_event_allowed(
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event, context
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)
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if not event_allowed:
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logger.info("Sending of knock %s forbidden by third-party rules", event)
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raise SynapseError(
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403, "This event is not allowed in this context", Codes.FORBIDDEN
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)
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await self._auth_and_persist_event(origin, event, context)
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return context
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async def _check_join_restrictions(
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self, context: EventContext, event: EventBase
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) -> None:
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"""Check that restrictions in restricted join rules are matched
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Called when we receive a join event via send_join.
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Raises an auth error if the restrictions are not matched.
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"""
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prev_state_ids = await context.get_prev_state_ids()
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# Check if the user is already in the room or invited to the room.
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user_id = event.state_key
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prev_member_event_id = prev_state_ids.get((EventTypes.Member, user_id), None)
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prev_member_event = None
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if prev_member_event_id:
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prev_member_event = await self.store.get_event(prev_member_event_id)
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# Check if the member should be allowed access via membership in a space.
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await self._event_auth_handler.check_restricted_join_rules(
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prev_state_ids,
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event.room_version,
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user_id,
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prev_member_event,
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)
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async def get_state_for_pdu(self, room_id: str, event_id: str) -> List[EventBase]:
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"""Returns the state at the event. i.e. not including said event."""
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