/hierarchy returns 403 when unknown room is accessible through federation

[ajbura]

Description

/hierarchy returns 403 when room is not on server without trying to get it from federation.

Steps to reproduce

• take roomId which is not on your server
• ask for hierarchy
• return 403 without checking over federation(even when it is available through federation)

Homeserver

matrix.org, envs.net

Synapse Version

{"server_version":"1.106.0rc1 (b=matrix-org-hotfixes,b9639065eb)"}

Installation Method

Docker (matrixdotorg/synapse)

Database

N/A

Workers

I don't know

Platform

N/A

Configuration

N/A

Relevant log output

N/A

Anything else that would be useful to know?

problem area:

synapse/synapse/handlers/room_summary.py

Line 187 in 7254015

if not await self._is_local_room_accessible(requested_room_id, requester):

it should also try to _summarize_remote_room_hierarchy before raising error

[anoadragon453]

https://matrix.to/#/!vcyiEtMVHIhWXcJAfl:sw1v.org/$BqX1ysEr7WQZwiZUyz2qDYNtND-LdQhlGst19ExLwks?via=matrix.org&via=element.io&via=envs.net notes that GET /_matrix/client/v1/rooms/{roomId}/hierarchy is not actually intended to be called with non-local rooms as the root room, invalidating this issue. The proper fix would indeed be to provide a via parameter to that endpoint. But doing so would be a separate MSC.