ADR-272: WebSocket authentication tickets

• Status: accepted
• Date: 2026-07-22
• Deciders: RuView maintainers
• Tags: auth, websocket, security, sensing-server
• Related: ADR-271 (Cognitum OAuth resource server), ADR-055 (integrated sensing server), PR #1313 (the exemption this supersedes), cognitum-one/dashboard ADR-060

Context

bearer_auth gates /api/v1/*. WebSocket upgrade endpoints were exempt, for a real reason: a browser's WebSocket constructor cannot attach an Authorization header to the handshake, so a gated socket is simply unreachable from page JavaScript. /ws/sensing and /ws/introspection sat outside PROTECTED_PREFIX entirely; /api/v1/stream/pose was added to an explicit EXEMPT_PATHS list by PR #1313.

The reasoning was sound. The consequence was not, and it was measured rather than argued. On a server with RUVIEW_API_TOKEN set — an operator who believes authentication is ON — a real WebSocket handshake carrying no credential at all:

/ws/sensing            -> 101 Switching Protocols
/ws/introspection      -> 101 Switching Protocols
/api/v1/stream/pose    -> 101 Switching Protocols
/api/v1/models         -> 401 Unauthorized        (control)

The control plane was locked and the data plane was open. /ws/sensing carries the live sensing output — presence, pose, breathing and heart rate. /ws/introspection exposes internal pipeline state. For the ADR-055 desktop topology (server bundled in the app, loopback only) that is bounded. For the LAN/hub deployment RuView also supports, anyone who can reach the port can watch the sensor.

ADR-271 sharpened the contrast rather than causing it: the REST surface is now genuinely strong — offline-verified Cognitum tokens, scope-separated destructive routes — which makes an ungated data plane the obvious way in.

Precision about the evidence: the handshake completing was verified. A payload frame was not captured in that window, so the finding is "the connection is established without a credential", not "data was read".

Decision

Gate every WebSocket upgrade. Accept either of two credentials, chosen to match what each kind of client can actually do.

1. Native clients send a bearer on the upgrade

The Python client, the Rust CLI and the TypeScript MCP client are not browsers and have never been subject to the header limitation. They can send a normal Authorization: Bearer on the handshake, so the server accepts one there; routing them through a ticket would add a round-trip and a second credential path for no benefit.

Correction, 2026-07-23. This section previously stated that those clients do send a bearer. The published Python client does not: python/wifi_densepose/client/ws.py calls websockets.connect(url, ping_interval, ping_timeout, max_size) and passes no headers at all — the file contains zero occurrences of extra_headers or Authorization. So every wifi-densepose[client] consumer 401s the moment an operator enables auth, and this ADR told them they would be fine.

The server side of the decision stands — a bearer on the upgrade is accepted, and that is the right contract for a non-browser client. What is missing is the client implementing it, tracked as ruvnet/RuView#1395. Until then the only remedy available to those users is RUVIEW_WS_LEGACY_UNAUTHENTICATED=1, which reopens the exposure this ADR exists to close — so it is a migration aid with a deadline, not an answer.

2. Browsers exchange their credential for a single-use ticket

POST /api/v1/ws-ticket is an ordinary authenticated request — where headers do work — and returns an opaque ticket the page appends as ?ticket=<value> on the socket URL.

A credential in a URL is normally a mistake. URLs reach access logs, Referer headers and browser history. Three properties bound this one, and all three are load-bearing:

The long-lived bearer token is still never placed in a URL.

A ticket inherits the issuing principal's scopes, so a sensing:read session cannot mint one that outranks itself, and a ticket from a token without sensing:read is refused at the upgrade.

3. WebSocket paths are matched by prefix, not by an allowlist

Anything under /ws/ is treated as an upgrade path, plus the one endpoint that lives outside it (/api/v1/stream/pose).

This is the most important detail in the ADR. An allowlist means every WebSocket route added later is ungated until someone remembers to extend it — the same bug, reintroduced on a delay. It is not hypothetical: /ws/train/progress (ADR-186, arriving with PR #1387) is already referenced by ui/services/training.service.js and would have shipped unauthenticated under an allowlist. Prefix matching gates it on arrival.

New WebSocket routes should live under /ws/ and inherit gating for free.

4. A migration escape hatch, deliberately uncomfortable

RUVIEW_WS_LEGACY_UNAUTHENTICATED=1 restores the previous behaviour. Gating these paths breaks a browser UI that has not yet been updated to fetch a ticket, and not every deployment can update server and UI in lockstep.

It is a migration aid, not a supported configuration:

• It logs a warning on every boot naming the actual exposure — "the live sensing stream — presence, pose and vital signs — is readable by anyone who can reach this port" — rather than something an operator can skim past.
• Its blast radius is exactly the WebSocket paths. A test pins that it does not weaken /api/v1/*.
• It is read once at construction, so changing the environment cannot silently open the paths on a running server.

The alternative — a clean break with no hatch — was considered and rejected as sequencing, not principle: a hard break tempts an operator into turning auth off entirely, which is strictly worse than a narrow, loudly-announced exception. The hatch should be removed once the shipped UI fetches tickets.

5. Deployments with auth off are unchanged

No credential configured ⇒ the middleware is the same no-op it has always been. Pinned by a test.

Consequences

• The measured hole is closed: all three paths now return 401 to a credential-less handshake, while a bearer or a valid ticket returns 101.
• Browser UIs need updating. Shipped in the same change for sensing.service.js, websocket-client.js and observatory/js/main.js via a shared withWsTicket() helper; a ticket is minted per connection attempt and never cached, because it is single-use and short-lived.
• A UI running against a server that predates this ADR still works: the helper treats 404 from /api/v1/ws-ticket as "no ticket needed".
• One more round-trip before a browser opens a socket. Negligible against a stream that then runs for minutes.
• Tickets live in memory, capped at 512 outstanding and self-healing as they expire, so an authenticated but misbehaving caller cannot grow the store without bound. In-memory is correct rather than convenient: a ticket surviving a restart would outlive the server that vouched for it.

Supersedes

PR #1313's enabled_exempts_pose_stream_websocket, which asserted the exemption. Its premise about browsers was correct and is preserved here; its conclusion is replaced. The test was renamed and inverted rather than deleted, with the history in its doc comment, and the half that still matters — the WebSocket rule must not leak to other /api/v1/* paths — is kept.

Deliberately not done

• /health* stays ungated. Orchestrator probes hit it anonymously, and that is the point of a liveness endpoint. /health/metrics is included in that exemption; if metrics ever carry occupancy-derived values this should be revisited, because that would make them sensing data wearing an ops label.
• /ui/* stays ungated. It is static assets; the data behind them is gated.
• No revocation of an issued ticket. It expires in seconds and is single-use; a revocation path would be more machinery than the exposure justifies.
• No ticket for native clients. They can send a header, so they should.

Implementation

v2/crates/wifi-densepose-sensing-server/src/ws_ticket.rs (store), src/bearer_auth.rs (gating), src/main.rs (POST /api/v1/ws-ticket), ui/services/ws-ticket.js plus the three call sites.

Tests: 12 store, 9 gating, 4 path-matching. Store coverage includes single-use enforcement, replay refusal, expiry refusal and pruning, 256-bit unpredictability, cap enforcement and self-healing, and ?myticket=x not being read as ?ticket=x. Gating coverage includes every known WS path refusing an unauthenticated upgrade, bearer acceptance, ticket single-use, a ticket being useless against REST, the escape hatch working and not weakening REST, and auth-off behaviour unchanged.