Failures when receiving events/PDUs without the origin field

[gnieto]

Background information

• Dendrite version or git SHA:
• Monolith or Polylith?: Both
• SQLite3 or Postgres?: Both
• Running in Docker?: Yes
• go version:
• Client used (if applicable):

Description

• What is the problem:

After removing origin fields from events in sytest (see matrix-org/sytest#1293), Dendrite builds failed. According to the v1.3 spec release, origin fields in PDUs are not required (matrix-org/matrix-spec#998).

Dendrite and gomatrixserverlib checks this field in several places and leads to failing tests in sytest (after removign the origin field; see the failed GHA runs on sytest's linked PR). For example, CheckFields validation from gometrixserverlib will fail if this field is not present: https://github.com/matrix-org/gomatrixserverlib/blob/2217f6c65ce3ab829b5d103d70be4891e68dc518/event.go#L751-L780

Dendrite is also doing some additional checks. For example, SendJoin is doing some additional checks here :

dendrite/federationapi/routing/join.go

Lines 207 to 212 in 3e87096

	if event.Origin() != request.Origin() {
	return util.JSONResponse{
	Code: http.StatusForbidden,
	JSON: jsonerror.Forbidden("The join must be sent by the server it originated on"),
	}
	}

Steps to reproduce

• Remove origin in any federation endpoint receiving an event (for example, SendJoin)

[gnieto]

This issue has been fixed in: #2737