Currently, when we receive an event whose auth_events differ from those we expect, we state-resolve between the two state sets, and check that the event passes auth based on the resolved state.
This means that it's possible for us to accept events which don't pass auth at their declared auth_events (or where the auth events themselves were rejected), leading to problems down the line like #10083.
This change means we will:
* ignore any events where we cannot find the auth events
* reject any events whose auth events were rejected
* reject any events which do not pass auth at their declared auth_events.
Together with a whole raft of previous work, this is a partial fix to #9595.
Fixes#6643.
Based on #11009.
This fixes a bug where we would accept an event whose `auth_events` include
rejected events, if the rejected event was shadowed by another `auth_event`
with same `(type, state_key)`.
The approach is to pass a list of auth events into
`check_auth_rules_for_event` instead of a dict, which of course means updating
the call sites.
This is an extension of #10956.
Found while working on the Gitter backfill script and noticed
it only happened after we sent 7 batches, https://gitlab.com/gitterHQ/webapp/-/merge_requests/2229#note_665906390
When there are more than 5 backward extremities for a given depth,
backfill will throw an error because we sliced the extremity list
to 5 but then try to iterate over the full list. This causes
us to look for state that we never fetched and we get a `KeyError`.
Before when calling `/messages` when there are more than 5 backward extremities:
```
Traceback (most recent call last):
File "/usr/local/lib/python3.8/site-packages/synapse/http/server.py", line 258, in _async_render_wrapper
callback_return = await self._async_render(request)
File "/usr/local/lib/python3.8/site-packages/synapse/http/server.py", line 446, in _async_render
callback_return = await raw_callback_return
File "/usr/local/lib/python3.8/site-packages/synapse/rest/client/room.py", line 580, in on_GET
msgs = await self.pagination_handler.get_messages(
File "/usr/local/lib/python3.8/site-packages/synapse/handlers/pagination.py", line 396, in get_messages
await self.hs.get_federation_handler().maybe_backfill(
File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 133, in maybe_backfill
return await self._maybe_backfill_inner(room_id, current_depth, limit)
File "/usr/local/lib/python3.8/site-packages/synapse/handlers/federation.py", line 386, in _maybe_backfill_inner
likely_extremeties_domains = get_domains_from_state(states[e_id])
KeyError: '$zpFflMEBtZdgcMQWTakaVItTLMjLFdKcRWUPHbbSZJl'
```
We correctly allowed using the MSC2716 batch endpoint for
the room creator in existing room versions but accidentally didn't track
the events because of a logic flaw.
This prevented you from connecting subsequent chunks together because it would
throw the unknown batch ID error.
We only want to process MSC2716 events when:
- The room version supports MSC2716
- Any room where the homeserver has the `msc2716_enabled` experimental feature enabled and the event is from the room creator
`_check_event_auth` is only called in two places, and only one of those sets
`send_on_behalf_of`. Warming the cache isn't really part of auth anyway, so
moving it out makes a lot more sense.
There's little point in doing a fancy state reconciliation dance if the event
itself is invalid.
Likewise, there's no point checking it again in `_check_for_soft_fail`.
Broadly, the existing `event_auth.check` function has two parts:
* a validation section: checks that the event isn't too big, that it has the rught signatures, etc.
This bit is independent of the rest of the state in the room, and so need only be done once
for each event.
* an auth section: ensures that the event is allowed, given the rest of the state in the room.
This gets done multiple times, against various sets of room state, because it forms part of
the state res algorithm.
Currently, this is implemented with `do_sig_check` and `do_size_check` parameters, but I think
that makes everything hard to follow. Instead, we split the function in two and call each part
separately where it is needed.
* Inline `_check_event_auth` for outliers
When we are persisting an outlier, most of `_check_event_auth` is redundant:
* `_update_auth_events_and_context_for_auth` does nothing, because the
`input_auth_events` are (now) exactly the event's auth_events,
which means that `missing_auth` is empty.
* we don't care about soft-fail, kicking guest users or `send_on_behalf_of`
for outliers
... so the only thing that matters is the auth itself, so let's just do that.
* `_auth_and_persist_fetched_events_inner`: de-async `prep`
`prep` no longer calls any `async` methods, so let's make it synchronous.
* Simplify `_check_event_auth`
We no longer need to support outliers here, which makes things rather simpler.
* changelog
* lint
* Factor more stuff out of `_get_events_and_persist`
It turns out that the event-sorting algorithm in `_get_events_and_persist` is
also useful in other circumstances. Here we move the current
`_auth_and_persist_fetched_events` to `_auth_and_persist_fetched_events_inner`,
and then factor the sorting part out to `_auth_and_persist_fetched_events`.
* `_get_remote_auth_chain_for_event`: remove redundant `outlier` assignment
`get_event_auth` returns events with the outlier flag already set, so this is
redundant (though we need to update a test where `get_event_auth` is mocked).
* `_get_remote_auth_chain_for_event`: move existing-event tests earlier
Move a couple of tests outside the loop. This is a bit inefficient for now, but
a future commit will make it better. It should be functionally identical.
* `_get_remote_auth_chain_for_event`: use `_auth_and_persist_fetched_events`
We can use the same codepath for persisting the events fetched as part of an
auth chain as for those fetched individually by `_get_events_and_persist` for
building the state at a backwards extremity.
* `_get_remote_auth_chain_for_event`: use a dict for efficiency
`_auth_and_persist_fetched_events` sorts the events itself, so we no longer
need to care about maintaining the ordering from `get_event_auth` (and no
longer need to sort by depth in `get_event_auth`).
That means that we can use a map, making it easier to filter out events we
already have, etc.
* changelog
* `_auth_and_persist_fetched_events`: improve docstring
Combine the two loops over the list of events, and hence get rid of
`_NewEventInfo`. Also pass the event back alongside the context, so that it's
easier to process the result.
* Reload auth events from db after fetching and persisting
In `_update_auth_events_and_context_for_auth`, when we fetch the remote auth
tree and persist the returned events: load the missing events from the database
rather than using the copies we got from the remote server.
This is mostly in preparation for additional refactors, but does have an
advantage in that if we later get around to checking the rejected status, we'll
be able to make use of it.
* Factor out `_get_remote_auth_chain_for_event` from `_update_auth_events_and_context_for_auth`
* changelog
Constructing an EventContext for an outlier is actually really simple, and
there's no sense in going via an `async` method in the `StateHandler`.
This also means that we can resolve a bunch of FIXMEs.
Adds missing type hints to methods in the synapse.handlers
module and requires all methods to have type hints there.
This also removes the unused construct_auth_difference method
from the FederationHandler.
I think I have finally teased apart the codepaths which handle outliers, and those that handle non-outliers.
Let's add some assertions to demonstrate my newfound knowledge.
If we're persisting an event E which has auth_events A1, A2, then we ought to make sure that we correctly auth
and persist A1 and A2, before we blindly accept E.
This PR does part of that - it persists the auth events first - but it does not fully solve the problem, because we
still don't check that the auth events weren't rejected.
This is part of my ongoing war against BaseHandler. I've moved kick_guest_users into RoomMemberHandler (since it calls out to that handler anyway), and split maybe_kick_guest_users into the two places it is called.
* Allow room creator to send MSC2716 related events in existing room versions
Discussed at https://github.com/matrix-org/matrix-doc/pull/2716/#discussion_r682474869
Restoring `get_create_event_for_room_txn` from,
44bb3f0cf5
* Add changelog
* Stop people from trying to redact MSC2716 events in unsupported room versions
* Populate rooms.creator column for easy lookup
> From some [out of band discussion](https://matrix.to/#/!UytJQHLQYfvYWsGrGY:jki.re/$p2fKESoFst038x6pOOmsY0C49S2gLKMr0jhNMz_JJz0?via=jki.re&via=matrix.org), my plan is to use `rooms.creator`. But currently, we don't fill in `creator` for remote rooms when a user is invited to a room for example. So we need to add some code to fill in `creator` wherever we add to the `rooms` table. And also add a background update to fill in the rows missing `creator` (we can use the same logic that `get_create_event_for_room_txn` is doing by looking in the state events to get the `creator`).
>
> https://github.com/matrix-org/synapse/pull/10566#issuecomment-901616642
* Remove and switch away from get_create_event_for_room_txn
* Fix no create event being found because no state events persisted yet
* Fix and add tests for rooms creator bg update
* Populate rooms.creator field for easy lookup
Part of https://github.com/matrix-org/synapse/pull/10566
- Fill in creator whenever we insert into the rooms table
- Add background update to backfill any missing creator values
* Add changelog
* Fix usage
* Remove extra delta already included in #10697
* Don't worry about setting creator for invite
* Only iterate over rows missing the creator
See https://github.com/matrix-org/synapse/pull/10697#discussion_r695940898
* Use constant to fetch room creator field
See https://github.com/matrix-org/synapse/pull/10697#discussion_r696803029
* More protection from other random types
See https://github.com/matrix-org/synapse/pull/10697#discussion_r696806853
* Move new background update to end of list
See https://github.com/matrix-org/synapse/pull/10697#discussion_r696814181
* Fix query casing
* Fix ambiguity iterating over cursor instead of list
Fix `psycopg2.ProgrammingError: no results to fetch` error
when tests run with Postgres.
```
SYNAPSE_POSTGRES=1 SYNAPSE_TEST_LOG_LEVEL=INFO python -m twisted.trial tests.storage.databases.main.test_room
```
---
We use `txn.fetchall` because it will return the results as a
list or an empty list when there are no results.
Docs:
> `cursor` objects are iterable, so, instead of calling explicitly fetchone() in a loop, the object itself can be used:
>
> https://www.psycopg.org/docs/cursor.html#cursor-iterable
And I'm guessing iterating over a raw cursor does something weird when there are no results.
---
Test CI failure: https://github.com/matrix-org/synapse/pull/10697/checks?check_run_id=3468916530
```
tests.test_visibility.FilterEventsForServerTestCase.test_large_room
===============================================================================
[FAIL]
Traceback (most recent call last):
File "/home/runner/work/synapse/synapse/tests/storage/databases/main/test_room.py", line 85, in test_background_populate_rooms_creator_column
self.get_success(
File "/home/runner/work/synapse/synapse/tests/unittest.py", line 500, in get_success
return self.successResultOf(d)
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/trial/_synctest.py", line 700, in successResultOf
self.fail(
twisted.trial.unittest.FailTest: Success result expected on <Deferred at 0x7f4022f3eb50 current result: None>, found failure result instead:
Traceback (most recent call last):
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/internet/defer.py", line 701, in errback
self._startRunCallbacks(fail)
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/internet/defer.py", line 764, in _startRunCallbacks
self._runCallbacks()
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/internet/defer.py", line 858, in _runCallbacks
current.result = callback( # type: ignore[misc]
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/internet/defer.py", line 1751, in gotResult
current_context.run(_inlineCallbacks, r, gen, status)
--- <exception caught here> ---
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/internet/defer.py", line 1657, in _inlineCallbacks
result = current_context.run(
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/python/failure.py", line 500, in throwExceptionIntoGenerator
return g.throw(self.type, self.value, self.tb)
File "/home/runner/work/synapse/synapse/synapse/storage/background_updates.py", line 224, in do_next_background_update
await self._do_background_update(desired_duration_ms)
File "/home/runner/work/synapse/synapse/synapse/storage/background_updates.py", line 261, in _do_background_update
items_updated = await update_handler(progress, batch_size)
File "/home/runner/work/synapse/synapse/synapse/storage/databases/main/room.py", line 1399, in _background_populate_rooms_creator_column
end = await self.db_pool.runInteraction(
File "/home/runner/work/synapse/synapse/synapse/storage/database.py", line 686, in runInteraction
result = await self.runWithConnection(
File "/home/runner/work/synapse/synapse/synapse/storage/database.py", line 791, in runWithConnection
return await make_deferred_yieldable(
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/internet/defer.py", line 858, in _runCallbacks
current.result = callback( # type: ignore[misc]
File "/home/runner/work/synapse/synapse/tests/server.py", line 425, in <lambda>
d.addCallback(lambda x: function(*args, **kwargs))
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/enterprise/adbapi.py", line 293, in _runWithConnection
compat.reraise(excValue, excTraceback)
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/python/deprecate.py", line 298, in deprecatedFunction
return function(*args, **kwargs)
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/python/compat.py", line 404, in reraise
raise exception.with_traceback(traceback)
File "/home/runner/work/synapse/synapse/.tox/py/lib/python3.9/site-packages/twisted/enterprise/adbapi.py", line 284, in _runWithConnection
result = func(conn, *args, **kw)
File "/home/runner/work/synapse/synapse/synapse/storage/database.py", line 786, in inner_func
return func(db_conn, *args, **kwargs)
File "/home/runner/work/synapse/synapse/synapse/storage/database.py", line 554, in new_transaction
r = func(cursor, *args, **kwargs)
File "/home/runner/work/synapse/synapse/synapse/storage/databases/main/room.py", line 1375, in _background_populate_rooms_creator_column_txn
for room_id, event_json in txn:
psycopg2.ProgrammingError: no results to fetch
```
* Move code not under the MSC2716 room version underneath an experimental config option
See https://github.com/matrix-org/synapse/pull/10566#issuecomment-906437909
* Add ordering to rooms creator background update
See https://github.com/matrix-org/synapse/pull/10697#discussion_r696815277
* Add comment to better document constant
See https://github.com/matrix-org/synapse/pull/10697#discussion_r699674458
* Use constant field
