When we have an event which refers to non-existent auth_events, ignore said events rather than exploding in a ball of fire.

Fixes #6605.

TODO: automate generation of this

s/reverse_proxy.rst/reverse_proxy.md/

Synapse 1.7.2 (2019-12-20)
==========================

This release fixes some regressions introduced in Synapse 1.7.0 and 1.7.1.

Bugfixes
--------

- Fix a regression introduced in Synapse 1.7.1 which caused errors when attempting to backfill rooms over federation. ([\#6576](https://github.com/matrix-org/synapse/issues/6576))
- Fix a bug introduced in Synapse 1.7.0 which caused an error on startup when upgrading from versions before 1.3.0. ([\#6578](https://github.com/matrix-org/synapse/issues/6578))

Only run prepare_database on connection for in-memory databases.

Fixes #6569.

Fixes #6575

Synapse 1.7.1 (2019-12-18)
==========================

This release includes several security fixes as well as a fix to a bug exposed by the security fixes. Administrators are encouraged to upgrade as soon as possible.

Security updates
----------------

- Fix a bug which could cause room events to be incorrectly authorized using events from a different room. ([\#6501](https://github.com/matrix-org/synapse/issues/6501), [\#6503](https://github.com/matrix-org/synapse/issues/6503), [\#6521](https://github.com/matrix-org/synapse/issues/6521), [\#6524](https://github.com/matrix-org/synapse/issues/6524), [\#6530](https://github.com/matrix-org/synapse/issues/6530), [\#6531](https://github.com/matrix-org/synapse/issues/6531))
- Fix a bug causing responses to the `/context` client endpoint to not use the pruned version of the event. ([\#6553](https://github.com/matrix-org/synapse/issues/6553))
- Fix a cause of state resets in room versions 2 onwards. ([\#6556](https://github.com/matrix-org/synapse/issues/6556), [\#6560](https://github.com/matrix-org/synapse/issues/6560))

Bugfixes
--------

- Fix a bug which could cause the federation server to incorrectly return errors when handling certain obscure event graphs. ([\#6526](https://github.com/matrix-org/synapse/issues/6526), [\#6527](https://github.com/matrix-org/synapse/issues/6527))

Previously we tried to be clever and filter out some unnecessary event
IDs to keep the auth chain small, but that had some annoying
interactions with state res v2 so we stop doing that for now.

 Use the filtered version of an event when responding to /context requests for that event

Merge branch 'babolivier/fix-context-filter' of github.com:matrix-org/synapse into babolivier/fix-context-filter

Co-Authored-By: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

This fixes a weird bug where, if you were determined enough, you could end up with a rejected event forming part of the state at a backwards-extremity. Authing that backwards extrem would then lead to us trying to pull the rejected event from the db (with allow_rejected=False), which would fail with a 404.

The main point here is to make sure that the state returned by _get_state_in_room has been authed before we try to use it as state in the room.

When we perform state resolution, check that all of the events involved are in
the right room.

When we do an event auth operation, check that all of the events involved are
in the right room.

When we request the state/auth_events to populate a backwards extremity (on
backfill or in the case of missing events in a transaction push), we should
check that the returned events are in the right room rather than blindly using
them in the room state or auth chain.

Given that _get_events_from_store_or_dest takes a room_id, it seems clear that
it should be sanity-checking the room_id of the requested events, so let's do
it there.

Make it return the state *after* the requested event, rather than the one
before it. This is a bit easier and requires fewer calls to
get_events_from_store_or_dest.

This is a non-functional refactor as a precursor to some other work.

There was a bunch of unnecessary conversion back and forth between dict and
list going on here. We can simplify a bunch of the code.

Sometimes the filtering function can return a pruned version of an event (on top of either the event itself or an empty list), if it thinks the user should be able to see that there's an event there but not the content of that event. Therefore, the previous logic of 'if filtered is empty then we can use the event we retrieved from the database' is flawed, and we should use the event returned by the filtering function.

Synapse 1.7.0 (2019-12-13)
==========================

This release changes the default settings so that only local authenticated users can query the server's room directory. See the [upgrade notes](UPGRADE.rst#upgrading-to-v170) for details.

Support for SQLite versions before 3.11 is now deprecated. A future release will refuse to start if used with an SQLite version before 3.11.

Administrators are reminded that SQLite should not be used for production instances. Instructions for migrating to Postgres are available [here](docs/postgres.md). A future release of synapse will, by default, disable federation for servers using SQLite.

No significant changes since 1.7.0rc2.

Synapse 1.7.0rc2 (2019-12-11)
=============================

Bugfixes
--------

- Fix incorrect error message for invalid requests when setting user's avatar URL. ([\#6497](https://github.com/matrix-org/synapse/issues/6497))
- Fix support for SQLite 3.7. ([\#6499](https://github.com/matrix-org/synapse/issues/6499))
- Fix regression where sending email push would not work when using a pusher worker. ([\#6507](https://github.com/matrix-org/synapse/issues/6507), [\#6509](https://github.com/matrix-org/synapse/issues/6509))

Synapse 1.7.0rc1 (2019-12-09)
=============================

Features
--------

- Implement per-room message retention policies. ([\#5815](https://github.com/matrix-org/synapse/issues/5815), [\#6436](https://github.com/matrix-org/synapse/issues/6436))
- Add etag and count fields to key backup endpoints to help clients guess if there are new keys. ([\#5858](https://github.com/matrix-org/synapse/issues/5858))
- Add `/admin/v2/users` endpoint with pagination. Contributed by Awesome Technologies Innovationslabor GmbH. ([\#5925](https://github.com/matrix-org/synapse/issues/5925))
- Require User-Interactive Authentication for `/account/3pid/add`, meaning the user's password will be required to add a third-party ID to their account. ([\#6119](https://github.com/matrix-org/synapse/issues/6119))
- Implement the `/_matrix/federation/unstable/net.atleastfornow/state/<context>` API as drafted in MSC2314. ([\#6176](https://github.com/matrix-org/synapse/issues/6176))
- Configure privacy-preserving settings by default for the room directory. ([\#6355](https://github.com/matrix-org/synapse/issues/6355))
- Add ephemeral messages support by partially implementing [MSC2228](https://github.com/matrix-org/matrix-doc/pull/2228). ([\#6409](https://github.com/matrix-org/synapse/issues/6409))
- Add support for [MSC 2367](https://github.com/matrix-org/matrix-doc/pull/2367), which allows specifying a reason on all membership events. ([\#6434](https://github.com/matrix-org/synapse/issues/6434))

Bugfixes
--------

- Transfer non-standard power levels on room upgrade. ([\#6237](https://github.com/matrix-org/synapse/issues/6237))
- Fix error from the Pillow library when uploading RGBA images. ([\#6241](https://github.com/matrix-org/synapse/issues/6241))
- Correctly apply the event filter to the `state`, `events_before` and `events_after` fields in the response to `/context` requests. ([\#6329](https://github.com/matrix-org/synapse/issues/6329))
- Fix caching devices for remote users when using workers, so that we don't attempt to refetch (and potentially fail) each time a user requests devices. ([\#6332](https://github.com/matrix-org/synapse/issues/6332))
- Prevent account data syncs getting lost across TCP replication. ([\#6333](https://github.com/matrix-org/synapse/issues/6333))
- Fix bug: TypeError in `register_user()` while using LDAP auth module. ([\#6406](https://github.com/matrix-org/synapse/issues/6406))
- Fix an intermittent exception when handling read-receipts. ([\#6408](https://github.com/matrix-org/synapse/issues/6408))
- Fix broken guest registration when there are existing blocks of numeric user IDs. ([\#6420](https://github.com/matrix-org/synapse/issues/6420))
- Fix startup error when http proxy is defined. ([\#6421](https://github.com/matrix-org/synapse/issues/6421))
- Fix error when using synapse_port_db on a vanilla synapse db. ([\#6449](https://github.com/matrix-org/synapse/issues/6449))
- Fix uploading multiple cross signing signatures for the same user. ([\#6451](https://github.com/matrix-org/synapse/issues/6451))
- Fix bug which lead to exceptions being thrown in a loop when a cross-signed device is deleted. ([\#6462](https://github.com/matrix-org/synapse/issues/6462))
- Fix `synapse_port_db` not exiting with a 0 code if something went wrong during the port process. ([\#6470](https://github.com/matrix-org/synapse/issues/6470))
- Improve sanity-checking when receiving events over federation. ([\#6472](https://github.com/matrix-org/synapse/issues/6472))
- Fix inaccurate per-block Prometheus metrics. ([\#6491](https://github.com/matrix-org/synapse/issues/6491))
- Fix small performance regression for sending invites. ([\#6493](https://github.com/matrix-org/synapse/issues/6493))
- Back out cross-signing code added in Synapse 1.5.0, which caused a performance regression. ([\#6494](https://github.com/matrix-org/synapse/issues/6494))

Improved Documentation
----------------------

- Update documentation and variables in user contributed systemd reference file. ([\#6369](https://github.com/matrix-org/synapse/issues/6369), [\#6490](https://github.com/matrix-org/synapse/issues/6490))
- Fix link in the user directory documentation. ([\#6388](https://github.com/matrix-org/synapse/issues/6388))
- Add build instructions to the docker readme. ([\#6390](https://github.com/matrix-org/synapse/issues/6390))
- Switch Ubuntu package install recommendation to use python3 packages in INSTALL.md. ([\#6443](https://github.com/matrix-org/synapse/issues/6443))
- Write some docs for the quarantine_media api. ([\#6458](https://github.com/matrix-org/synapse/issues/6458))
- Convert CONTRIBUTING.rst to markdown (among other small fixes). ([\#6461](https://github.com/matrix-org/synapse/issues/6461))

Deprecations and Removals
-------------------------

- Remove admin/v1/users_paginate endpoint. Contributed by Awesome Technologies Innovationslabor GmbH. ([\#5925](https://github.com/matrix-org/synapse/issues/5925))
- Remove fallback for federation with old servers which lack the /federation/v1/state_ids API. ([\#6488](https://github.com/matrix-org/synapse/issues/6488))

Internal Changes
----------------

- Add benchmarks for structured logging and improve output performance. ([\#6266](https://github.com/matrix-org/synapse/issues/6266))
- Improve the performance of outputting structured logging. ([\#6322](https://github.com/matrix-org/synapse/issues/6322))
- Refactor some code in the event authentication path for clarity. ([\#6343](https://github.com/matrix-org/synapse/issues/6343), [\#6468](https://github.com/matrix-org/synapse/issues/6468), [\#6480](https://github.com/matrix-org/synapse/issues/6480))
- Clean up some unnecessary quotation marks around the codebase. ([\#6362](https://github.com/matrix-org/synapse/issues/6362))
- Complain on startup instead of 500'ing during runtime when `public_baseurl` isn't set when necessary. ([\#6379](https://github.com/matrix-org/synapse/issues/6379))
- Add a test scenario to make sure room history purges don't break `/messages` in the future. ([\#6392](https://github.com/matrix-org/synapse/issues/6392))
- Clarifications for the email configuration settings. ([\#6423](https://github.com/matrix-org/synapse/issues/6423))
- Add more tests to the blacklist when running in worker mode. ([\#6429](https://github.com/matrix-org/synapse/issues/6429))
- Refactor data store layer to support multiple databases in the future. ([\#6454](https://github.com/matrix-org/synapse/issues/6454), [\#6464](https://github.com/matrix-org/synapse/issues/6464), [\#6469](https://github.com/matrix-org/synapse/issues/6469), [\#6487](https://github.com/matrix-org/synapse/issues/6487))
- Port synapse.rest.client.v1 to async/await. ([\#6482](https://github.com/matrix-org/synapse/issues/6482))
- Port synapse.rest.client.v2_alpha to async/await. ([\#6483](https://github.com/matrix-org/synapse/issues/6483))
- Port SyncHandler to async/await. ([\#6484](https://github.com/matrix-org/synapse/issues/6484))

Give the server config to the RoomWorkerStore