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Fix 404 on `/sync` when the last event is a redaction of an unknown/purged event (#12905) 

Currently, we try to pull the event corresponding to a sync token from the database. However, when
we fetch redaction events, we check the target of that redaction (because we aren't allowed to send
redactions to clients without validating them). So, if the sync token points to a redaction of an event
that we don't have, we have a problem.

It turns out we don't really need that event, and can just work with its ID and metadata, which
sidesteps the whole problem.
This commit is contained in:
Richard van der Hoff 2022-06-01 12:29:51 +01:00 committed by GitHub
parent 5949ab86f8
commit 79dadf7216
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6 changed files with 129 additions and 65 deletions
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1
changelog.d/12905.bugfix Normal file
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@ -0,0 +1 @@
Fix a bug introduced in Synapse 1.58.0 where `/sync` would fail if the most recent event in a room was a redaction of an event that has since been purged.

110
synapse/handlers/message.py
View File

@ -28,6 +28,7 @@ from synapse.api.constants import (
EventContentFields,
EventTypes,
GuestAccess,
HistoryVisibility,
Membership,
RelationTypes,
UserTypes,
@ -66,7 +67,7 @@ from synapse.util import json_decoder, json_encoder, log_failure, unwrapFirstErr
from synapse.util.async_helpers import Linearizer, gather_results
from synapse.util.caches.expiringcache import ExpiringCache
from synapse.util.metrics import measure_func
from synapse.visibility import filter_events_for_client
from synapse.visibility import get_effective_room_visibility_from_state
if TYPE_CHECKING:
from synapse.events.third_party_rules import ThirdPartyEventRules
@ -182,51 +183,31 @@ class MessageHandler:
state_filter = state_filter or StateFilter.all()
if at_token:
last_event = await self.store.get_last_event_in_room_before_stream_ordering(
last_event_id = (
await self.store.get_last_event_in_room_before_stream_ordering(
room_id,
end_token=at_token.room_key,
)
)
if not last_event:
if not last_event_id:
raise NotFoundError("Can't find event for token %s" % (at_token,))
# check whether the user is in the room at that time to determine
# whether they should be treated as peeking.
state_map = await self._state_storage_controller.get_state_for_event(
last_event.event_id,
StateFilter.from_types([(EventTypes.Member, user_id)]),
)
joined = False
membership_event = state_map.get((EventTypes.Member, user_id))
if membership_event:
joined = membership_event.membership == Membership.JOIN
is_peeking = not joined
visible_events = await filter_events_for_client(
self._storage_controllers,
user_id,
[last_event],
filter_send_to_client=False,
is_peeking=is_peeking,
)
if visible_events:
room_state_events = (
await self._state_storage_controller.get_state_for_events(
[last_event.event_id], state_filter=state_filter
)
)
room_state: Mapping[Any, EventBase] = room_state_events[
last_event.event_id
]
else:
if not await self._user_can_see_state_at_event(
user_id, room_id, last_event_id
):
raise AuthError(
403,
"User %s not allowed to view events in room %s at token %s"
% (user_id, room_id, at_token),
)
room_state_events = (
await self._state_storage_controller.get_state_for_events(
[last_event_id], state_filter=state_filter
)
)
room_state: Mapping[Any, EventBase] = room_state_events[last_event_id]
else:
(
membership,
@ -256,6 +237,65 @@ class MessageHandler:
events = self._event_serializer.serialize_events(room_state.values(), now)
return events
async def _user_can_see_state_at_event(
self, user_id: str, room_id: str, event_id: str
) -> bool:
# check whether the user was in the room, and the history visibility,
# at that time.
state_map = await self._state_storage_controller.get_state_for_event(
event_id,
StateFilter.from_types(
[
(EventTypes.Member, user_id),
(EventTypes.RoomHistoryVisibility, ""),
]
),
)
membership = None
membership_event = state_map.get((EventTypes.Member, user_id))
if membership_event:
membership = membership_event.membership
# if the user was a member of the room at the time of the event,
# they can see it.
if membership == Membership.JOIN:
return True
# otherwise, it depends on the history visibility.
visibility = get_effective_room_visibility_from_state(state_map)
if visibility == HistoryVisibility.JOINED:
# we weren't a member at the time of the event, so we can't see this event.
return False
# otherwise *invited* is good enough
if membership == Membership.INVITE:
return True
if visibility == HistoryVisibility.INVITED:
# we weren't invited, so we can't see this event.
return False
if visibility == HistoryVisibility.WORLD_READABLE:
return True
# So it's SHARED, and the user was not a member at the time. The user cannot
# see history, unless they have *subsequently* joined the room.
#
# XXX: if the user has subsequently joined and then left again,
# ideally we would share history up to the point they left. But
# we don't know when they left. We just treat it as though they
# never joined, and restrict access.
(
current_membership,
_,
) = await self.store.get_local_current_membership_for_user_in_room(
user_id, event_id
)
return current_membership == Membership.JOIN
async def get_joined_members(self, requester: Requester, room_id: str) -> dict:
"""Get all the joined members in the room and their profile information.

27
synapse/handlers/sync.py
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@ -621,21 +621,32 @@ class SyncHandler:
)
async def get_state_after_event(
self, event: EventBase, state_filter: Optional[StateFilter] = None
self, event_id: str, state_filter: Optional[StateFilter] = None
) -> StateMap[str]:
"""
Get the room state after the given event
Args:
event: event of interest
event_id: event of interest
state_filter: The state filter used to fetch state from the database.
"""
state_ids = await self._state_storage_controller.get_state_ids_for_event(
event.event_id, state_filter=state_filter or StateFilter.all()
event_id, state_filter=state_filter or StateFilter.all()
)
if event.is_state():
# using get_metadata_for_events here (instead of get_event) sidesteps an issue
# with redactions: if `event_id` is a redaction event, and we don't have the
# original (possibly because it got purged), get_event will refuse to return
# the redaction event, which isn't terribly helpful here.
#
# (To be fair, in that case we could assume it's *not* a state event, and
# therefore we don't need to worry about it. But still, it seems cleaner just
# to pull the metadata.)
m = (await self.store.get_metadata_for_events([event_id]))[event_id]
if m.state_key is not None and m.rejection_reason is None:
state_ids = dict(state_ids)
state_ids[(event.type, event.state_key)] = event.event_id
state_ids[(m.event_type, m.state_key)] = event_id
return state_ids
async def get_state_at(
@ -654,14 +665,14 @@ class SyncHandler:
# FIXME: This gets the state at the latest event before the stream ordering,
# which might not be the same as the "current state" of the room at the time
# of the stream token if there were multiple forward extremities at the time.
last_event = await self.store.get_last_event_in_room_before_stream_ordering(
last_event_id = await self.store.get_last_event_in_room_before_stream_ordering(
room_id,
end_token=stream_position.room_key,
)
if last_event:
if last_event_id:
state = await self.get_state_after_event(
last_event, state_filter=state_filter or StateFilter.all()
last_event_id, state_filter=state_filter or StateFilter.all()
)
else:

12
synapse/storage/databases/main/state.py
View File

@ -54,6 +54,7 @@ class EventMetadata:
room_id: str
event_type: str
state_key: Optional[str]
rejection_reason: Optional[str]
def _retrieve_and_check_room_version(room_id: str, room_version_id: str) -> RoomVersion:
@ -167,17 +168,22 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
)
sql = f"""
SELECT e.event_id, e.room_id, e.type, se.state_key FROM events AS e
SELECT e.event_id, e.room_id, e.type, se.state_key, r.reason
FROM events AS e
LEFT JOIN state_events se USING (event_id)
LEFT JOIN rejections r USING (event_id)
WHERE {clause}
"""
txn.execute(sql, args)
return {
event_id: EventMetadata(
room_id=room_id, event_type=event_type, state_key=state_key
room_id=room_id,
event_type=event_type,
state_key=state_key,
rejection_reason=rejection_reason,
)
for event_id, room_id, event_type, state_key in txn
for event_id, room_id, event_type, state_key, rejection_reason in txn
}
result_map: Dict[str, EventMetadata] = {}

12
synapse/storage/databases/main/stream.py
View File

@ -765,15 +765,16 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
self,
room_id: str,
end_token: RoomStreamToken,
) -> Optional[EventBase]:
"""Returns the last event in a room at or before a stream ordering
) -> Optional[str]:
"""Returns the ID of the last event in a room at or before a stream ordering
Args:
room_id
end_token: The token used to stream from
Returns:
The most recent event.
The ID of the most recent event, or None if there are no events in the room
before this stream ordering.
"""
last_row = await self.get_room_event_before_stream_ordering(
@ -781,10 +782,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
stream_ordering=end_token.stream,
)
if last_row:
_, _, event_id = last_row
event = await self.get_event(event_id, get_prev_content=True)
return event
return last_row[2]
return None
async def get_current_room_stream_token_for_room_id(

28
synapse/visibility.py
View File

@ -162,16 +162,7 @@ async def filter_events_for_client(
state = event_id_to_state[event.event_id]
# get the room_visibility at the time of the event.
visibility_event = state.get(_HISTORY_VIS_KEY, None)
if visibility_event:
visibility = visibility_event.content.get(
"history_visibility", HistoryVisibility.SHARED
)
else:
visibility = HistoryVisibility.SHARED
if visibility not in VISIBILITY_PRIORITY:
visibility = HistoryVisibility.SHARED
visibility = get_effective_room_visibility_from_state(state)
# Always allow history visibility events on boundaries. This is done
# by setting the effective visibility to the least restrictive
@ -267,6 +258,23 @@ async def filter_events_for_client(
return [ev for ev in filtered_events if ev]
def get_effective_room_visibility_from_state(state: StateMap[EventBase]) -> str:
"""Get the actual history vis, from a state map including the history_visibility event
Handles missing and invalid history visibility events.
"""
visibility_event = state.get(_HISTORY_VIS_KEY, None)
if not visibility_event:
return HistoryVisibility.SHARED
visibility = visibility_event.content.get(
"history_visibility", HistoryVisibility.SHARED
)
if visibility not in VISIBILITY_PRIORITY:
visibility = HistoryVisibility.SHARED
return visibility
async def filter_events_for_server(
storage: StorageControllers,
server_name: str,