* Don't check whether a 3pid is allowed to register during password reset

This endpoint should only deal with emails that have already been approved, and
are attached with user's account. There's no need to re-check them here.

* Changelog

* Fix table scan of events on worker startup.

This happened because we assumed "new" writers had an initial stream
position of 0, so the replication code tried to fetch all events written
by the instance between 0 and the current position.

Instead, set the initial position of new writers to the current
persisted up to position, on the assumption that new writers won't have
written anything before that point.

* Consider old writers coming back as "new".

Otherwise we'd try and fetch entries between the old stale token and the
current position, even though it won't have written any rows.

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

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

For some reason, an apparently unrelated PR upset mypy about this module. Here are a number of little fixes.

Merge branch 'develop' of github.com:matrix-org/synapse into anoa/info-mainline-no-check-password-reset

This PR adds a script that:

* Builds the local Synapse checkout using our existing `docker/Dockerfile` image.
* Downloads [Complement](https://github.com/matrix-org/complement/)'s source code.
* Builds the [Synapse.Dockerfile](https://github.com/matrix-org/complement/blob/master/dockerfiles/Synapse.Dockerfile) using the above dockerfile as a base.
* Builds and runs Complement against it.

This set up differs slightly from [that of the dendrite repo](https://github.com/matrix-org/dendrite/blob/master/build/scripts/complement.sh) (`complement.sh`, `Complement.Dockerfile`), which instead stores a separate, but slightly modified, dockerfile in Dendrite's repo rather than running the one stored in Complement's repo. That synapse equivalent to that dockerfile (`Synapse.Dockerfile`) in Complement's repo is just based on top of `matrixdotorg/synapse:latest`, which we opt to build here locally.

Thus copying over the files from Complement's repo wouldn't change any functionality, and would result in two instances of the same files. So just using the dockerfile in Complement's repo was decided upon instead.

This is an attempt to fix #8403.

Broken in https://github.com/matrix-org/synapse/pull/8275 and has yet to be put in a release. Fixes https://github.com/matrix-org/synapse/issues/8418.

`next_link` is an optional parameter. However, we were checking whether the `next_link` param was valid, even if it wasn't provided. In that case, `next_link` was `None`, which would clearly not be a valid URL.

This would prevent password reset and other operations if `next_link` was not provided, and the `next_link_domain_whitelist` config option was set.

One hope is that this might provide some insights into #3365.

* Remove `on_timeout_cancel` from `timeout_deferred`

The `on_timeout_cancel` param to `timeout_deferred` wasn't always called on a
timeout (in particular if the canceller raised an exception), so it was
unreliable. It was also only used in one place, and to be honest it's easier to
do what it does a different way.

* Fix handling of connection timeouts in outgoing http requests

Turns out that if we get a timeout during connection, then a different
exception is raised, which wasn't always handled correctly.

To fix it, catch the exception in SimpleHttpClient and turn it into a
RequestTimedOutError (which is already a documented exception).

Also add a description to RequestTimedOutError so that we can see which stage
it failed at.

* Fix incorrect handling of timeouts reading federation responses

This was trapping the wrong sort of TimeoutError, so was never being hit.

The effect was relatively minor, but we should fix this so that it does the
expected thing.

* Fix inconsistent handling of `timeout` param between methods

`get_json`, `put_json` and `delete_json` were applying a different timeout to
the response body to `post_json`; bring them in line and test.

Co-authored-by: Patrick Cloke <clokep@users.noreply.github.com>
Co-authored-by: Erik Johnston <erik@matrix.org>

This endpoint should only deal with emails that have already been approved, and
are attached with user's account. There's no need to re-check them here.

This table was created in #8034 (1.20.0).  It references
`ui_auth_sessions`, which is ignored, so this one should be too.

Signed-off-by: Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

* Fix test_verify_json_objects_for_server_awaits_previous_requests

It turns out that this wasn't really testing what it thought it was testing
(in particular, `check_context` was turning failures into success, which was
making the tests pass even though it wasn't clear they should have been.

It was also somewhat overcomplex - we can test what it was trying to test
without mocking out perspectives servers.

* Fix warnings about finished logcontexts in the keyring

We need to make sure that we finish the key fetching magic before we run the
verifying code, to ensure that we don't mess up our logcontexts.

Co-authored-by: Benjamin Koch <bbbsnowball@gmail.com>

This adds configuration flags that will match a user to pre-existing users
when logging in via OpenID Connect. This is useful when switching to
an existing SSO system.

Fixes #8395.

On startup `MultiWriteIdGenerator` fetches the maximum stream ID for
each instance from the table and uses that as its initial "current
position" for each writer. This is problematic as a) it involves either
a scan of events table or an index (neither of which is ideal), and b)
if rows are being persisted out of order elsewhere while the process
restarts then using the maximum stream ID is not correct. This could
theoretically lead to race conditions where e.g. events that are
persisted out of order are not sent down sync streams.

We fix this by creating a new table that tracks the current positions of
each writer to the stream, and update it each time we finish persisting
a new entry. This is a relatively small overhead when persisting events.
However for the cache invalidation stream this is a much bigger relative
overhead, so instead we note that for invalidation we don't actually
care about reliability over restarts (as there's no caches to
invalidate) and simply don't bother reading and writing to the new table
in that particular case.

#8037 changed the default `autoescape` option when rendering Jinja2 templates from `False` to `True`. This caused some bugs, noticeably around redirect URLs being escaped in SAML2 auth confirmation templates, causing those URLs to break for users.

This change returns the previous behaviour as it stood. We may want to look at each template individually and see whether autoescaping is a good idea at some point, but for now lets just fix the breakage.

The idea is to remove some of the places we pass around `int`, where it can represent one of two things:

1. the position of an event in the stream; or
2. a token that partitions the stream, used as part of the stream tokens.

The valid operations are then:

1. did a position happen before or after a token;
2. get all events that happened before or after a token; and
3. get all events between two tokens.

(Note that we don't want to allow other operations as we want to change the tokens to be vector clocks rather than simple ints)

this makes it possible to use from the manhole, and seems cleaner anyway.

I'd like to get a better insight into what we are doing with respect to state
res. The list of state groups we are resolving across should be short (if it
isn't, that's a massive problem in itself), so it should be fine to log it in
ite entiretly.

I've done some grepping and found approximately zero cases in which the
"shortcut" code delivered the result, so I've ripped that out too.

This will allow us to hit the DB after we've finished using the generated stream ID.

When updating the `room_stats_state` table, we try to check for null bytes slipping in to the content for state events. It turns out we had added `guest_access` as a field to room_stats_state without including it in the null byte check.

Lo and behold, a null byte in a `m.room.guest_access` event then breaks `room_stats_state` updates.

This PR adds the check for `guest_access`.