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Clean up _update_auth_events_and_context_for_auth (#11122)

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Remove some redundant code, and generally simplify.
This commit is contained in:
Richard van der Hoff 2021-10-20 19:22:40 +02:00 committed by GitHub
parent 2c61a318cc
commit 0930e9ae12
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2 changed files with 38 additions and 114 deletions
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1
changelog.d/11122.misc Normal file
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@ -0,0 +1 @@
Clean up some of the federation event authentication code for clarity.

151
synapse/handlers/federation_event.py
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@ -65,7 +65,6 @@ from synapse.replication.http.federation import (
from synapse.state import StateResolutionStore
from synapse.storage.databases.main.events_worker import EventRedactBehaviour
from synapse.types import (
MutableStateMap,
PersistedEventPosition,
RoomStreamToken,
StateMap,
@ -1417,13 +1416,8 @@ class FederationEventHandler:
}
try:
(
context,
auth_events_for_auth,
) = await self._update_auth_events_and_context_for_auth(
origin,
updated_auth_events = await self._update_auth_events_for_auth(
event,
context,
calculated_auth_event_map=calculated_auth_event_map,
)
except Exception:
@ -1436,6 +1430,14 @@ class FederationEventHandler:
"Ignoring failure and continuing processing of event.",
event.event_id,
)
updated_auth_events = None
if updated_auth_events:
context = await self._update_context_for_auth_events(
event, context, updated_auth_events
)
auth_events_for_auth = updated_auth_events
else:
auth_events_for_auth = calculated_auth_event_map
try:
@ -1560,13 +1562,11 @@ class FederationEventHandler:
soft_failed_event_counter.inc()
event.internal_metadata.soft_failed = True
async def _update_auth_events_and_context_for_auth(
async def _update_auth_events_for_auth(
self,
origin: str,
event: EventBase,
context: EventContext,
calculated_auth_event_map: StateMap[EventBase],
) -> Tuple[EventContext, StateMap[EventBase]]:
) -> Optional[StateMap[EventBase]]:
"""Helper for _check_event_auth. See there for docs.
Checks whether a given event has the expected auth events. If it
@ -1579,96 +1579,27 @@ class FederationEventHandler:
processing of the event.
Args:
origin:
event:
context:
calculated_auth_event_map:
Our calculated auth_events based on the state of the room
at the event's position in the DAG.
Returns:
updated context, updated auth event map
updated auth event map, or None if no changes are needed.
"""
assert not event.internal_metadata.outlier
# take a copy of calculated_auth_event_map before we modify it.
auth_events: MutableStateMap[EventBase] = dict(calculated_auth_event_map)
# check for events which are in the event's claimed auth_events, but not
# in our calculated event map.
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/.
#
# TODO: this code is now redundant, since it should be impossible for us to
# get here without already having the auth events.
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)
# missing_auth is now the set of event_ids which:
# a. are listed in event.auth_events, *and*
# b. are *not* part of our calculated auth events based on room state, *and*
# c. are *not* yet in our database.
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
)
}
)
# auth_events now contains
# 1. our *calculated* auth events based on the room state, plus:
# 2. any events which:
# a. are listed in `event.auth_events`, *and*
# b. are not part of our calculated auth events, *and*
# c. were not in our database before the call to /event_auth
# d. have since been added to our database (most likely by /event_auth).
different_auth = event_auth_events.difference(
e.event_id for e in auth_events.values()
e.event_id for e in calculated_auth_event_map.values()
)
# different_auth is the set of events which *are* in `event.auth_events`, but
# which are *not* in `auth_events`. Comparing with (2.) above, this means
# exclusively the set of `event.auth_events` which we already had in our
# database before any call to /event_auth.
#
# I'm reasonably sure that the fact that events returned by /event_auth are
# blindly added to auth_events (and hence excluded from different_auth) is a bug
# - though it's a very long-standing one (see
# https://github.com/matrix-org/synapse/commit/78015948a7febb18e000651f72f8f58830a55b93#diff-0bc92da3d703202f5b9be2d3f845e375f5b1a6bc6ba61705a8af9be1121f5e42R786
# from Jan 2015 which seems to add it, though it actually just moves it from
# elsewhere (before that, it gets lost in a mess of huge "various bug fixes"
# PRs).
if not different_auth:
return context, auth_events
return None
logger.info(
"auth_events refers to events which are not in our calculated auth "
@ -1680,27 +1611,18 @@ class FederationEventHandler:
# necessary?
different_events = await self._store.get_events_as_list(different_auth)
# double-check they're all in the same room - we should already have checked
# this but it doesn't hurt to check again.
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
assert (
d.room_id == event.room_id
), f"Event {event.event_id} refers to auth_event {d.event_id} which is in a different room"
# 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)
local_state = calculated_auth_event_map.values()
remote_auth_events = dict(calculated_auth_event_map)
remote_auth_events.update({(d.type, d.state_key): d for d in different_events})
remote_state = remote_auth_events.values()
@ -1708,23 +1630,24 @@ class FederationEventHandler:
new_state = await self._state_handler.resolve_events(
room_version, (local_state, remote_state), event
)
different_state = {
(d.type, d.state_key): d
for d in new_state.values()
if calculated_auth_event_map.get((d.type, d.state_key)) != d
}
if not different_state:
logger.info("State res returned no new state")
return None
logger.info(
"After state res: updating auth_events with new state %s",
{
d
for d in new_state.values()
if auth_events.get((d.type, d.state_key)) != d
},
different_state.values(),
)
auth_events.update(new_state)
context = await self._update_context_for_auth_events(
event, context, auth_events
)
return context, auth_events
# take a copy of calculated_auth_event_map before we modify it.
auth_events = dict(calculated_auth_event_map)
auth_events.update(different_state)
return auth_events
async def _load_or_fetch_auth_events_for_event(
self, destination: str, event: EventBase