Extend voice-limit-guard to enforce a per-room publish-source policy
(io.lotus.room_quality allow_screenshare/allow_camera) for ALL Matrix clients,
alongside the existing participant limit.
- At token issue, re-sign the LiveKit JWT's canPublishSources to drop forbidden
sources (microphone always kept). Verifies our own secret signed the token
first and fails open on mismatch, so a secret drift can never mint a token the
SFU rejects. Limit check and source policy are independent (one's outage can't
skip the other).
- Live (mid-call) enforcement: a background reconcile loop calls LiveKit
UpdateParticipant to revoke a forbidden source from participants who joined
before the policy changed -- which unpublishes their in-progress
screenshare/camera server-side within ~3s and blocks re-publish. Only removes
sources (never grants), preserves other permission flags, fails open, and runs
as a daemon thread that cannot crash or block token issuance.
- Endpoint-specific room-id extraction (/get_token->room_id, /sfu/get->room) so
a client sending both keys can't get a different room's policy applied.
- Auto-deploy the guard on LXC 151 (py_compile-gated, backup + rollback).
- Unit tests: JWT re-sign/verify + tamper, secret-mismatch, source narrowing,
reconcile (never-grant / preserve-flags / disable-on-empty), fail-open.
Numeric bitrate/fps caps are NOT server-enforceable on an SFU (LiveKit forwards,
never transcodes) and remain a Lotus-client-cooperative setting; the
screenshare/camera permission is the hard cross-client lever.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
jared
a06f2c662a