`_update_auth_events_and_context_for_auth`: add some comments (#10987)
Add some more comments about wtf is going on here.
2 files changed, 27 insertions, 0 deletions
diff --git a/changelog.d/10987.misc b/changelog.d/10987.misc
new file mode 100644
index 0000000000..9a765435db
--- /dev/null
+++ b/changelog.d/10987.misc
@@ -0,0 +1 @@
+Clean up some of the federation event authentication code for clarity.
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index 5938654338..aa20d75550 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -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
|
