Missing 'origin' field when responding to send_join over federation

[gnieto]

Description

Synapse is not sending origin field on federation send join endpoint as defined on spec: https://matrix.org/docs/spec/server_server/r0.1.4#put-matrix-federation-v2-send-join-roomid-eventid

Origin is missing here:

synapse/synapse/handlers/federation.py

Line 1577 in 79bfe96

return {"state": list(state.values()), "auth_chain": auth_chain}

[richvdh]

I feel like we should remove it from the spec, rather than add it to synapse, since it's redundant to the Authorization header.

Technically that would be a breaking change in the spec, but if synapse has never sent it I'm inclined to simply consider its presence a bug in the spec.

[richvdh]

see: https://github.com/matrix-org/matrix-doc/issues/1664#issuecomment-731153498

[richvdh]

Closing this; I consider it a spec bug, not a Synapse one.

[DMRobertson]

Recently related: matrix-org/sytest#1293

[richvdh]

There seems to have been some broken logic here, though I don't think it changes my conclusions.

I feel like we should remove it from the spec, rather than add it to synapse, since it's redundant to the Authorization header.

The Authorization header is irrelevant here, since that applies to requests, and this issue is about responses.

But still, origin serves no purpose here: we know which server we connected to, and that is the what the spec currently defines the origin field to mean: