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_update_auth_events_and_context_for_auth: add some comments (#10987)

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Add some more comments about wtf is going on here.
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Richard van der Hoff 2021-10-05 12:50:38 +01:00 committed by GitHub
parent cb88ed912b
commit d099535deb
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changelog.d/10987.misc Normal file
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@ -0,0 +1 @@
Clean up some of the federation event authentication code for clarity.

26
synapse/handlers/federation_event.py
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@ -1476,6 +1476,11 @@ class FederationEventHandler:
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)
@ -1497,10 +1502,31 @@ class FederationEventHandler:
}
)
# 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()
)
# 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