The publisher-side dispatcher in handleInboundBidi previously matched
inbound Subscribe bidis on `track` only, never checking whether the
requested `broadcast` field matched the suffix our publisher claimed
on this session. A peer (or buggy relay) could open a Subscribe under
broadcast="otherPubkey" track="audio/data" and we would route OUR
audio frames to them — the dispatcher only filtered on track.
Production never bit because moq-rs's relay routes Subscribe messages
to the specific publisher whose broadcast matches the requested path
upstream of us, so an off-target broadcast never landed on our
inbound bidi pump. But a peer-to-peer connection without a relay
in between would have been able to siphon our audio under any
broadcast string they invented.
The fix: validate `sub.broadcast == publisher.suffix` (both already
path-normalised by the codec) before track matching. On mismatch,
reply `SubscribeDrop(errorCode=BROADCAST_DOES_NOT_EXIST,
reasonPhrase="<requested> not published on this session
(we publish <ours>)")` and FIN. New error code
`MoqLiteSubscribeDropCode.BROADCAST_DOES_NOT_EXIST = 0x05L` mirrors
the IETF MoQ-transport `TRACK_NAMESPACE_DOES_NOT_EXIST` semantic so
a watcher can tell apart "wrong room" from "wrong rendition".
Regression test:
`MoqLiteSessionTest.publisher_replies_subscribeDrop_when_broadcast_does_not_match`.
Audit doc: nestsClient/plans/2026-05-09-moq-lite-rfc-compliance.md (M5).
https://claude.ai/code/session_012TGfo99Ugz7fcCPv85a8Tq
Claude
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