Weakness in auth chain indexing allows DoS from remote room members
through disk fill and high CPU usage.
A remote Matrix user with malicious intent, sharing a room with Synapse
instances before 1.104.1, can dispatch specially crafted events to
exploit a weakness in how the auth chain cover index is calculated. This
can induce high CPU consumption and accumulate excessive data in the
database of such instances, resulting in a denial of service.
Servers in private federations, or those that do not federate, are not
affected.
Resurrecting https://github.com/matrix-org/synapse/pull/13918.
This should reduce IOPs incurred by joining to the events table to
lookup stream ordering, which happens in many receipt handling code
paths. Like the previous PR I believe sufficient time has passed between
the original migration in DB schema 72 and now to merge this as-is. It's
highly unlikely that both the migration is still ongoing AND (active)
users still have any receipts prior to that date.
In the unlikely event there is a receipt without a populated
`event_stream_ordering` synapse will behave just as it does now when
receipts exist for events that don't (yet): for push action calculation
the receipts are just ignored.
I've removed the validation on event IDs as this is already covered
here:
59ceabcb97/synapse/handlers/receipts.py (L189-L192)
PR #16942 removed an invalid optimisation that avoided pulling out state
for non-gappy syncs. This causes a large increase in DB usage. c.f.
#16941 for why that optimisation was wrong.
However, we can still optimise in the simple case where the events in
the timeline are a linear chain without any branching/merging of the
DAG.
cc. @richvdh
Before we were pulling out *all* read receipts for a user for every
event we pushed. Instead let's only pull out the relevant receipts.
This also pulled out the event rows for each receipt, causing load on
the events table.
This PR fixes a very, very niche edge-case, but I've got some more work
coming which will otherwise make the problem worse.
The bug happens when the syncing user leaves a room, and has a sync
filter which includes "left" rooms, but sets the timeline limit to 0. In
that case, the state returned in the `state` section is calculated
incorrectly.
The fix is to pass a token corresponding to the point that the user
leaves the room through to `compute_state_delta`.
Requests may require a User-Agent header, and the change in #16972
accidentally removed it, resulting in requests getting rejected causing
login to fail.
Fixes https://github.com/element-hq/synapse/issues/16680, as well as a
related bug, where servers which we had *never* successfully sent an
event to would not be retried.
In order to fix the case of pending to-device messages, we hook into the
existing `wake_destinations_needing_catchup` process, by extending it to
look for destinations that have pending to-device messages. The
federation transmission loop then attempts to send the pending to-device
messages as normal.
When a lot of locks are waiting for a single lock, notifying all locks
independently with `call_later` on each release is really costly and
incurs some kind of async contention, where the CPU is spinning a lot
for not much.
The included test is taking around 30s before the change, and 0.5s
after.
It was found following failing tests with
https://github.com/element-hq/synapse/pull/16827.
This PR aims to fix#16895, caused by a regression in #7 and not fixed
by #16903. The PR #16903 only fixes a starvation issue, where the CPU
isn't released. There is a second issue, where the execution is blocked.
This theory is supported by the flame graphs provided in #16895 and the
fact that I see the CPU usage reducing and far below the limit.
Since the changes in #7, the method `check_state_independent_auth_rules`
is called with the additional parameter `batched_auth_events`:
6fa13b4f92/synapse/handlers/federation_event.py (L1741-L1743)
It makes the execution enter this if clause, introduced with #151956fa13b4f92/synapse/event_auth.py (L178-L189)
There are two issues in the above code snippet.
First, there is the blocking issue. I'm not entirely sure if this is a
deadlock, starvation, or something different. In the beginning, I
thought the copy operation was responsible. It wasn't. Then I
investigated the nested `store.get_events` inside the function `update`.
This was also not causing the blocking issue. Only when I replaced the
set difference operation (`-` ) with a list comprehension, the blocking
was resolved. Creating and comparing sets with a very large amount of
events seems to be problematic.
This is how the flamegraph looks now while persisting outliers. As you
can see, the execution no longer locks up in the above function.
Second, the copying here doesn't serve any purpose, because only a
shallow copy is created. This means the same objects from the original
dict are referenced. This fails the intention of protecting these
objects from mutation. The review of the original PR
https://github.com/matrix-org/synapse/pull/15195 had an extensive
discussion about this matter.
Various approaches to copying the auth_events were attempted:
1) Implementing a deepcopy caused issues due to
builtins.EventInternalMetadata not being pickleable.
2) Creating a dict with new objects akin to a deepcopy.
3) Creating a dict with new objects containing only necessary
attributes.
Concluding, there is no easy way to create an actual copy of the
objects. Opting for a deepcopy can significantly strain memory and CPU
resources, making it an inefficient choice. I don't see why the copy is
necessary in the first place. Therefore I'm proposing to remove it
altogether.
After these changes, I was able to successfully join these rooms,
without the main worker locking up:
- #synapse:matrix.org
- #element-android:matrix.org
- #element-web:matrix.org
- #ecips:matrix.org
- #ipfs-chatter:ipfs.io
- #python:matrix.org
- #matrix:matrix.org
Since Synapse 1.76.0, any module which registers a `on_new_event`
callback would brick the ability to join remote rooms.
This is because this callback tried to get the full state of the room,
which would end up in a deadlock.
Related:
https://github.com/matrix-org/synapse-auto-accept-invite/issues/18
The following module would brick the ability to join remote rooms:
```python
from typing import Any, Dict, Literal, Union
import logging
from synapse.module_api import ModuleApi, EventBase
logger = logging.getLogger(__name__)
class MyModule:
def __init__(self, config: None, api: ModuleApi):
self._api = api
self._config = config
self._api.register_third_party_rules_callbacks(
on_new_event=self.on_new_event,
)
async def on_new_event(self, event: EventBase, _state_map: Any) -> None:
logger.info(f"Received new event: {event}")
@staticmethod
def parse_config(_config: Dict[str, Any]) -> None:
return None
```
This is technically a breaking change, as we are now passing partial
state on the `on_new_event` callback.
However, this callback was broken for federated rooms since 1.76.0, and
local rooms have full state anyway, so it's unlikely that it would
change anything.
This adds a counter `synapse_emails_sent_total` for emails sent. They
are broken down by `type`, which are `password_reset`, `registration`,
`add_threepid`, `notification` (matching the methods of `Mailer`).
We do this by adding support to the LRU cache for "extra indices" based
on the cached value. This allows us to efficiently map from room ID to
the cached events and only invalidate those.
List of users not to send out device list updates for when they register
new devices. This is useful to handle bot accounts.
This is undocumented as its mostly a hack to test on matrix.org.
Note: This will still send out device list updates if the device is
later updated, e.g. end to end keys are added.
This basically reverts a change that was in
https://github.com/element-hq/synapse/pull/16833, where we reduced the
batching.
The smaller batching can cause performance issues on busy servers and
databases.
During the migration the automated script to update the copyright
headers accidentally got rid of some of the existing copyright lines.
Reinstate them.
Prior to this PR, if a request to create a public (public as in
published to the rooms directory) room violated the room list
publication rules set in the
[config](https://matrix-org.github.io/synapse/latest/usage/configuration/config_documentation.html#room_list_publication_rules),
the request to create the room was denied and the room was not created.
This PR changes the behavior such that when a request to create a room
published to the directory violates room list publication rules, the
room is still created but the room is not published to the directory.
The current query supports passing in a list of users, which generates a
query using `user_id = ANY(..)`. This is generates a less efficient
query plan that is notably slower than a simple `user_id = ?` condition.
Note: The new function is mostly a copy and paste and then a
simplification of the existing function.
The crux of the change is to try and make the queries simpler and pull
out fewer rows. Before, there were quite a few joins against subqueries,
which caused postgres to pull out more rows than necessary.
Instead, let's simplify the query and do some of the filtering out in
Python instead, letting Postgres do better optimizations now that it
doesn't have to deal with joins against subqueries.
Review note: this is a complete rewrite of the function, so not sure how
useful the diff is.
---------
Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
In previous versions of authlib using `client_secret_basic` without a
`client_secret` would result in an invalid auth header. Since authlib
1.3 it throws an exception.
The configuration may be accepted in by very lax servers, so we don't
want to deny it outright. Instead, let's default the
`client_auth_method` to `none`, which does the right thing. If the
config specifies `client_auth_method` and no `client_secret` then that
is going to be bogus and we should reject it
Sometimes we fail to fetch events during backfill due to missing state,
and we often end up querying the same bad events periodically (as people
backpaginate). In such cases its likely we will continue to fail to get
the state, and therefore we should try *before* loading the state that
we have from the DB (as otherwise it's wasted DB and memory).
---------
Co-authored-by: reivilibre <oliverw@matrix.org>
There are two changes here:
1. Only pull out the required state when handling the request.
2. Change the get filtered state return type to check that we're only
querying state that was requested
---------
Co-authored-by: reivilibre <oliverw@matrix.org>
Instead of persisting outliers in a bunch of batches, let's just do them
all at once.
This is fine because all `_auth_and_persist_outliers_inner` is doing is
checking the auth rules for each event, which requires the events to be
topologically sorted by the auth graph.
The idea here being that the directory server shouldn't advertise rooms
to a requesting server is the requesting server would not be allowed to
join or participate in the room.
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Original commit schedule, with full messages:
<ol>
<li>
Pass `from_federation_origin` down into room list retrieval code
</li>
<li>
Don't cache /publicRooms response for inbound federated requests
</li>
<li>
fixup! Don't cache /publicRooms response for inbound federated requests
</li>
<li>
Cap the number of /publicRooms entries to 100
</li>
<li>
Simplify code now that you can't request unlimited rooms
</li>
<li>
Filter out rooms from federated requests that don't have the correct ACL
</li>
<li>
Request a handful more when filtering ACLs so that we can try to avoid
shortchanging the requester
</li>
</ol>
---------
Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>
There are a couple of things we need to be careful of here:
1. The current python code does no validation when loading from the DB,
so we need to be careful to ignore such errors (at least on jki.re there
are some old events with internal metadata fields of the wrong type).
2. We want to be memory efficient, as we often have many hundreds of
thousands of events in the cache at a time.
---------
Co-authored-by: Quentin Gliech <quenting@element.io>
We remove these fields as they're just duplicating data the event
already stores, and (for reasons 🤫) I'd like to simplify
the class to only store simple types.
I'm not entirely convinced that we shouldn't instead add helper methods
to the event class to generate stream tokens, but I don't really think
that's where they belong either
This is an extra response parameter just added to MSC3981. In the
current impl, the recursion depth is always 3, so this just returns a
static 3 if the recurse parameter is supplied.
Previously, the response status of `HTMLResource` was hardcoded as
`200`. However, for proper redirection after the user verifies their
email, we require the status to be `302`. This PR addresses that issue
by using `code` as response status.
Closes:
- https://github.com/matrix-org/synapse/issues/10397
- #10397
An administrator should know whether he wants to set a password or not.
There are many uses cases where a blank password is required.
- Use of only some users with SSO.
- Use of bots with password, users with SSO
This reverts two commits:
0bb8e418a4
"Fix postgres schema after dropping old tables (#16730)"
and
51e4e35653
"Add a Postgres `REPLICA IDENTITY` to tables that do not have an implicit one. This should allow use of Postgres logical replication. (take 2, now with no added deadlocks!) (#16658)"
and also amends the changelog.
* Add `ALTER TABLE ... REPLICA IDENTITY ...` for individual tables
We can't combine them into one file as it makes it likely to hit a deadlock
if Synapse is running, as it only takes one other transaction to access two
tables in a different order to the schema delta.
* Add notes
* Newsfile
Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>
* Re-introduce REPLICA IDENTITY test
---------
Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>
