2.1 KiB
Set v3 to be the default room version
Homeservers support multiple room versions, though one version is the default. All new rooms created by a server are of the default version.
Room v3 uses the new state resolution algorithm, and replaces event IDs with hashes, thereby closing a raft of security issues.
This MSC proposes changing the recommended default from v1 to v3.
Proposal
The default room should be updated to be room v3 from v1.
Until we have greater confidence in the room upgrade UX v1 will continue to be marked as 'stable'.
By contrast, very few rooms will be of version v2, and this version can be safely marked as 'unstable' to denote that it is deprecated.
This means that new rooms will be created as v3 rooms, but existing rooms will not prompt admins to upgrade. Separately we intend to deprecate v1, but doing so will come as part of a separate MSC.
Tradeoffs
It is likely that the imminent Matrix 1.0 release will require a new room version. However, before this version can become the default there must be sufficient take up in the federation so as to avoid locking out old servers.
Therefore it is worth realising the value of v3 rooms immediately rather than waiting for the new room version to arrive and proliferate.
Potential issues
If new rooms are to be v3 some old servers will not be able to participate since they will not support v3. For context, v3 was introduced in Synapse 0.99.0 on 5th Feb 2019.
Ignoring a long tail of of pre 0.30.0 servers (0.30.0 was released in May 2018) ~2/3 servers support v3, and practically speaking ~90% of users are on v3 compatible servers.
It does not seem unreasonable to expect Synapse admins to update to > 0.99.0 server as a means to mitigate any difficulties caused by not supporting v3 rooms.
Security considerations
The primary driver for this MSC is to address known security vulnerabilities.
Conclusion
Marking v3 as the default room version is a pragmatic means to improve security in the Matrix federation. Future MSCs will propose further changing the default to v4 as well marking v1 and v2 as 'unstable' to encourage all rooms to upgrade.