There is a corner in `_check_event_auth` (long known as "the weird corner") where, if we get an event with auth_events which don't match those we were expecting, we attempt to resolve the diffence between our state and the remote's with a state resolution.
This isn't specced, and there's general agreement we shouldn't be doing it.
However, it turns out that the faster-joins code was relying on it, so we need to introduce something similar (but rather simpler) for that.
Whenever we want to persist an event, we first compute an event context,
which includes the state at the event and a flag indicating whether the
state is partial. After a lot of processing, we finally try to store the
event in the database, which can fail for partial state events when the
containing room has been un-partial stated in the meantime.
We detect the race as a foreign key constraint failure in the data store
layer and turn it into a special `PartialStateConflictError` exception,
which makes its way up to the method in which we computed the event
context.
To make things difficult, the exception needs to cross a replication
request: `/fed_send_events` for events coming over federation and
`/send_event` for events from clients. We transport the
`PartialStateConflictError` as a `409 Conflict` over replication and
turn `409`s back into `PartialStateConflictError`s on the worker making
the request.
All client events go through
`EventCreationHandler.handle_new_client_event`, which is called in
*a lot* of places. Instead of trying to update all the code which
creates client events, we turn the `PartialStateConflictError` into a
`429 Too Many Requests` in
`EventCreationHandler.handle_new_client_event` and hope that clients
take it as a hint to retry their request.
On the federation event side, there are 7 places which compute event
contexts. 4 of them use outlier event contexts:
`FederationEventHandler._auth_and_persist_outliers_inner`,
`FederationHandler.do_knock`, `FederationHandler.on_invite_request` and
`FederationHandler.do_remotely_reject_invite`. These events won't have
the partial state flag, so we do not need to do anything for then.
The remaining 3 paths which create events are
`FederationEventHandler.process_remote_join`,
`FederationEventHandler.on_send_membership_event` and
`FederationEventHandler._process_received_pdu`.
We can't experience the race in `process_remote_join`, unless we're
handling an additional join into a partial state room, which currently
blocks, so we make no attempt to handle it correctly.
`on_send_membership_event` is only called by
`FederationServer._on_send_membership_event`, so we catch the
`PartialStateConflictError` there and retry just once.
`_process_received_pdu` is called by `on_receive_pdu` for incoming
events and `_process_pulled_event` for backfill. The latter should never
try to persist partial state events, so we ignore it. We catch the
`PartialStateConflictError` in `on_receive_pdu` and retry just once.
Refering to the graph of code paths in
https://github.com/matrix-org/synapse/issues/12988#issuecomment-1156857648
may make the above make more sense.
Signed-off-by: Sean Quah <seanq@matrix.org>
When we fail to persist a federation event, we kick off a task to remove
its push actions in the background, using the current logging context.
Since we don't `await` that task, we may finish our logging context
before the task finishes. There's no reason to not `await` the task, so
let's do that.
Signed-off-by: Sean Quah <seanq@matrix.org>
* Add auth events to events used in tests
* Move some event auth checks out to a different method
Some of the event auth checks apply to an event's auth_events, rather than the
state at the event - which means they can play no part in state
resolution. Move them out to a separate method.
* Rename check_auth_rules_for_event
Now it only checks the state-dependent auth rules, it needs a better name.
Instead, use the `room_version` property of the event we're checking.
The `room_version` was originally added as a parameter somewhere around #4482,
but really it's been redundant since #6875 added a `room_version` field to `EventBase`.
Instead, use the `room_version` property of the event we're validating.
The `room_version` was originally added as a parameter somewhere around #4482,
but really it's been redundant since #6875 added a `room_version` field to `EventBase`.
Refactor how the `EventContext` class works, with the intention of reducing the amount of state we fetch from the DB during event processing.
The idea here is to get rid of the cached `current_state_ids` and `prev_state_ids` that live in the `EventContext`, and instead defer straight to the database (and its caching).
One change that may have a noticeable effect is that we now no longer prefill the `get_current_state_ids` cache on a state change. However, that query is relatively light, since its just a case of reading a table from the DB (unlike fetching state at an event which is more heavyweight). For deployments with workers this cache isn't even used.
Part of #12684
When we join a room via the faster-joins mechanism, we end up with "partial
state" at some points on the event DAG. Many parts of the codebase need to
wait for the full state to load. So, we implement a mechanism to keep track of
which events have partial state, and wait for them to be fully-populated.
We work through all the events with partial state, updating the state at each
of them. Once it's done, we recalculate the state for the whole room, and then
mark the room as having complete state.
Refactor and convert `Linearizer` to async. This makes a `Linearizer`
cancellation bug easier to fix.
Also refactor to use an async context manager, which eliminates an
unlikely footgun where code that doesn't immediately use the context
manager could forget to release the lock.
Signed-off-by: Sean Quah <seanq@element.io>
If we're missing most of the events in the room state, then we may as well call the /state endpoint, instead of individually requesting each and every event.
When we get a partial_state response from send_join, store information in the
database about it:
* store a record about the room as a whole having partial state, and stash the
list of member servers too.
* flag the join event itself as having partial state
* also, for any new events whose prev-events are partial-stated, note that
they will *also* be partial-stated.
We don't yet make any attempt to interpret this data, so API calls (and a bunch
of other things) are just going to get incorrect data.
msc3706 proposes changing the `/send_join` response:
> Any events returned within `state` can be omitted from `auth_chain`.
Currently, we rely on `m.room.create` being returned in `auth_chain`, but since
the `m.room.create` event must necessarily be part of the state, the above
change will break this.
In short, let's look for `m.room.create` in `state` rather than `auth_chain`.
I've never found this terribly useful. I think it was added in the early days
of Synapse, without much thought as to what would actually be useful to log,
and has just been cargo-culted ever since.
Rather, it tends to clutter up debug logs with useless information.
* `_auth_and_persist_outliers`: mark persisted events as outliers
Mark any events that get persisted via `_auth_and_persist_outliers` as, well,
outliers.
Currently this will be a no-op as everything will already be flagged as an
outlier, but I'm going to change that.
* `process_remote_join`: stop flagging as outlier
The events are now flagged as outliers later on, by `_auth_and_persist_outliers`.
* `send_join`: remove `outlier=True`
The events created here are returned in the result of `send_join` to
`FederationHandler.do_invite_join`. From there they are passed into
`FederationEventHandler.process_remote_join`, which passes them to
`_auth_and_persist_outliers`... which sets the `outlier` flag.
* `get_event_auth`: remove `outlier=True`
stop flagging the events returned by `get_event_auth` as outliers. This method
is only called by `_get_remote_auth_chain_for_event`, which passes the results
into `_auth_and_persist_outliers`, which will flag them as outliers.
* `_get_remote_auth_chain_for_event`: remove `outlier=True`
we pass all the events into `_auth_and_persist_outliers`, which will now flag
the events as outliers.
* `_check_sigs_and_hash_and_fetch`: remove unused `outlier` parameter
This param is now never set to True, so we can remove it.
* `_check_sigs_and_hash_and_fetch_one`: remove unused `outlier` param
This is no longer set anywhere, so we can remove it.
* `get_pdu`: remove unused `outlier` parameter
... and chase it down into `get_pdu_from_destination_raw`.
* `event_from_pdu_json`: remove redundant `outlier` param
This is never set to `True`, so can be removed.
* changelog
* update docstring
Events returned by `backfill` should not be flagged as outliers.
Fixes:
```
AssertionError: null
File "synapse/handlers/federation.py", line 313, in try_backfill
dom, room_id, limit=100, extremities=extremities
File "synapse/handlers/federation_event.py", line 517, in backfill
await self._process_pulled_events(dest, events, backfilled=True)
File "synapse/handlers/federation_event.py", line 642, in _process_pulled_events
await self._process_pulled_event(origin, ev, backfilled=backfilled)
File "synapse/handlers/federation_event.py", line 669, in _process_pulled_event
assert not event.internal_metadata.is_outlier()
```
See https://sentry.matrix.org/sentry/synapse-matrixorg/issues/231992Fixes#8894.
* Push `get_room_{min,max_stream_ordering}` into StreamStore
Both implementations of this are identical, so we may as well push it down and
get rid of the abstract base class nonsense.
* Remove redundant `StreamStore` class
This is empty now
* Remove redundant `get_current_events_token`
This was an exact duplicate of `get_room_max_stream_ordering`, so let's get rid
of it.
* newsfile
This is the final piece of the jigsaw for #9595. As with other changes before this one (eg #10771), we need to make sure that we auth the auth events in the right order, and actually check that their predecessors haven't been rejected.
To do this I've reused the existing code we use when persisting outliers elsewhere.
I've removed the code for attempting to fetch missing auth_events - the events should have been present in the send_join response, so the likely reason they are missing is that we couldn't verify them, so requesting them again is unlikely to help. Instead, we simply drop any state which relies on those auth events, as we do at a backwards-extremity. See also matrix-org/complement#216 for a test for this.
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'
```
Eric Eastwood
