2 files changed, 19 insertions, 5 deletions
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 510a176821..bc20b9c201 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -146,11 +146,15 @@ class FederationServer(FederationBase):
# check that it's actually being sent from a valid destination to
# workaround bug #1753 in 0.18.5 and 0.18.6
if transaction.origin != get_domain_from_id(pdu.event_id):
+ # We continue to accept join events from any server; this is
+ # necessary for the federation join dance to work correctly.
+ # (When we join over federation, the "helper" server is
+ # responsible for sending out the join event, rather than the
+ # origin. See bug #1893).
if not (
pdu.type == 'm.room.member' and
pdu.content and
- pdu.content.get("membership", None) == 'join' and
- self.hs.is_mine_id(pdu.state_key)
+ pdu.content.get("membership", None) == 'join'
):
logger.info(
"Discarding PDU %s from invalid origin %s",
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 888dd01240..2ecc0087b8 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1004,9 +1004,19 @@ class FederationHandler(BaseHandler):
)
event.internal_metadata.outlier = False
- # Send this event on behalf of the origin server since they may not
- # have an up to data view of the state of the room at this event so
- # will not know which servers to send the event to.
+ # Send this event on behalf of the origin server.
+ #
+ # The reasons we have the destination server rather than the origin
+ # server send it are slightly mysterious: the origin server should have
+ # all the neccessary state once it gets the response to the send_join,
+ # so it could send the event itself if it wanted to. It may be that
+ # doing it this way reduces failure modes, or avoids certain attacks
+ # where a new server selectively tells a subset of the federation that
+ # it has joined.
+ #
+ # The fact is that, as of the current writing, Synapse doesn't send out
+ # the join event over federation after joining, and changing it now
+ # would introduce the danger of backwards-compatibility problems.
event.internal_metadata.send_on_behalf_of = origin
context, event_stream_id, max_stream_id = yield self._handle_new_event(
|
