From 4251928aed58f60c2211a1aa9322f6d680989282 Mon Sep 17 00:00:00 2001 From: Johannes Marbach Date: Mon, 19 Aug 2024 13:33:47 +0200 Subject: [PATCH] MSC4156: Migrate server_name to via (#4156) --- proposals/4156-server-name-to-via.md | 64 ++++++++++++++++++++++++++++ 1 file changed, 64 insertions(+) create mode 100644 proposals/4156-server-name-to-via.md diff --git a/proposals/4156-server-name-to-via.md b/proposals/4156-server-name-to-via.md new file mode 100644 index 00000000..d8719de3 --- /dev/null +++ b/proposals/4156-server-name-to-via.md @@ -0,0 +1,64 @@ +# MSC4156: Migrate `server_name` to `via` + +Room IDs in Matrix are generally not routable on their own. In the [room ID grammar] `!opaque_id:domain`, +the `domain` is the server that created the room. There is, however, no guarantee that this server is +still joined to the room at a later time. Therefore, room IDs don't provide a reliable resident server +to send requests to. Critically, the `domain` is not to be used as a routing server. It is purely a namespace. + +The spec partially addresses this issue by defining a [`via`] query parameter on room URIs that can be +used to list servers that have a high probability of being in the room in the distant future. Additionally, +some APIs such as [`/_matrix/client/v3/join/{roomIdOrAlias}`] can take a `server_name` query parameter +that has the same effect as `via`. + +The terminology difference between `server_name` and `via` can be slightly confusing which is why this +proposal attempts to standardize on `via`. + + +## Proposal + +The `server_name` query parameter on [`/_matrix/client/v3/join/{roomIdOrAlias}`] and +[`/_matrix/client/v3/knock/{roomIdOrAlias}`] is deprecated and a new parameter `via: [string]` is +introduced. + +Clients SHOULD use `via` when the homeserver they're talking to supports it. To do this, they MAY either +detect server support through the supported spec versions in [`/_matrix/client/versions`] or always include +both parameters (with identical values). + +Homeservers MUST ignore all `server_name` parameters if any `via` parameters are supplied. + + +## Potential issues + +As with any migration, some effort will be required to update client and server implementations. Additionally, +while the transitions isn't completed, the concurrent existence of both query parameters might lead to further +confusion. + + +## Alternatives + +None other than accepting status quo. + + +## Security considerations + +A client that supplies different `via` and `server_name` parameters could be served a different room depending +on which set of parameters the server uses to resolve the room ID. Tricking a client into doing this seems very +difficult though because [Matrix URIs], for instance, only have a single documented `via` parameter. + + +## Unstable prefix + +Until this proposal is accepted into the spec, implementations SHOULD refer to `via` as `org.matrix.msc4156.via`. + + +## Dependencies + +None. + + +[Matrix URIs]: https://spec.matrix.org/v1.11/appendices/#matrix-uri-scheme +[room ID grammar]: https://spec.matrix.org/v1.10/appendices/#room-ids +[`via`]: https://spec.matrix.org/v1.10/appendices/#routing +[`/_matrix/client/v3/join/{roomIdOrAlias}`]: https://spec.matrix.org/v1.10/client-server-api/#post_matrixclientv3joinroomidoralias +[`/_matrix/client/v3/knock/{roomIdOrAlias}`]: https://spec.matrix.org/v1.10/client-server-api/#post_matrixclientv3knockroomidoralias +[`/_matrix/client/versions`]: https://spec.matrix.org/v1.10/client-server-api/#get_matrixclientversions