The sensing-server binds to 127.0.0.1 by default with no `Host` header
validation on either router. A foreign page can lower its DNS TTL,
re-resolve to 127.0.0.1 after the browser has accepted the origin, and
then read live pose + vital signs from /api/v1/* + /ws/sensing as
same-origin against the attacker's hostname. When `RUVIEW_API_TOKEN` is
unset (the documented LAN-mode default from #443/#547) the attacker
can also drive state-mutating POSTs (recording/start, models/load,
adaptive/train, calibration/start, sona/activate).
Defense: a small `host_validation` axum middleware that pins the `Host`
header to a configurable allowlist. The loopback names (`localhost`,
`127.0.0.1`, `[::1]`, each with or without a port) are always in the
set, so default 127.0.0.1 deployments keep working from the local
browser without any configuration change. Operators who bind to a
routable address extend the set with one or more `--allowed-host`
flags or a comma-separated `SENSING_ALLOWED_HOSTS` env var.
Reverse-proxy deployments that already canonicalise `Host` opt out
with `--disable-host-validation`.
The layer is wired into both the dedicated WebSocket router on
`--ws-port` (8765) and the main HTTP router on `--http-port` (8080),
so /ws/sensing on either listener is covered. Rejection responses are
`421 Misdirected Request` (the correct status for a request that
arrived at a server that does not consider the supplied `Host`
authoritative); missing `Host` is `400 Bad Request`.
CWE-346 (Origin Validation Error), CWE-350 (Reliance on Reverse DNS).
Severity: high.
Tests: 13 new unit tests on the middleware (loopback defaults,
case-insensitivity, IPv6 bracketing, port stripping, env-var/CLI
merge, foreign-host rejection on /health + /ws/*, disabled-allowlist
escape hatch). Full suite: 220/220 pass under
`cargo test -p wifi-densepose-sensing-server --no-default-features`.
Co-authored-by: Aeon <aeon@aaronjmars.com>
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