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Go proxy allows websocket attach (GET /containers/{name}/attach/ws), giving stdin access to containers

Aperta
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Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
48/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
docker, go, rust, typescript
Ambito
api, backend, security

Direzione di ricerca

Start with the Go router and go/internal/proxy/transport.go, then compare the Rust and TypeScript transports. Read spec/router.qnt and the existing execNeverAllowed rule; add coverage in the three router tables and an integration check for the websocket upgrade. Done means attach paths are denied across methods and the upgrade receives the proxy's 403 in all three implementations.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Priority: P0 Type: Bug

Describe the bug
The Go proxy lets a client write to a container's stdin through a websocket attach: GET /containers/{name}/attach/ws?stdin=1&stream=1 with Upgrade: websocket. The router treats it as a read (GET passthrough), and go/internal/proxy/transport.go (httputil.ReverseProxy) passes the protocol upgrade through, so the client gets a bidirectional stream to the container. Attaching to a container whose main process is a shell is equivalent to exec, which the proxy exists to deny. This holds with and without --readonly.

Found in the review of the #75 fix (fix/readonly-router-75); not introduced by it.

Affected implementation(s)

  • Go: exploitable (reproduced)
  • Rust: forwards the upgrade request and relays the daemon's 101, but the connection breaks right after; no stdin reached the container
  • TypeScript: the request timed out; no stdin reached the container

Rust and TS are not exploitable in this probe, but both forward an attach request they should deny.

To Reproduce

  1. docker run -d -i --name zzws busybox sh -c 'while read l; do echo "GOT:$l" >> /tmp/in.txt; done'
  2. Run the Go proxy (--readonly or not) with --config-dir=deploy/config.
  3. Over the proxy socket, send GET /containers/zzws/attach/ws?stdin=1&stream=1 HTTP/1.1 with Upgrade: websocket, Connection: Upgrade, Sec-WebSocket-Key, Sec-WebSocket-Version: 13, then one masked text frame pwned-via-readonly-proxy.
  4. Result: HTTP/1.1 101 Switching Protocols; docker exec zzws cat /tmp/in.txt prints GOT:pwned-via-readonly-proxy. Audit log: "decision":"ALLOW" … "path":"/containers/zzws/attach/ws".

Expected behavior

  • Deny attach in the router for every method, like exec: attach as a whole segment after /containers/{name} (covering /attach and /attach/ws), with a message such as attach is not allowed. (POST /containers/{name}/attach is already default-denied as a non-lifecycle POST; the GET …/attach/ws form is the gap.)
  • Refuse protocol upgrades in all three transports: strip or reject requests carrying Upgrade/Connection: Upgrade, so no endpoint can be turned into a raw stream. Defence in depth; the Docker CLI's legitimate uses of upgrade (attach, exec start) are already denied.
  • Spec: an attach deny rule and property in spec/router.qnt mirroring execNeverAllowed; table rows in all three; an integration check that the upgrade is refused with the proxy's 403.

Alternatives considered:

  • Only block upgrades in the transport. Rejected alone: the plain (non-upgrade) POST /containers/{id}/attach hijack path should stay denied by the router too, and the router is where the spec lives.
  • Treat --readonly specially. Rejected: the gap exists in every mode.

Environment

  • Docker 29.4.0 (OrbStack); Go binary from fix/readonly-router-75 (same router/transport as main for this path).

Additional context
Consider a security advisory for the Go releases once fixed.

Lingua principale
Rust
Stelle
2
Fork
0
Merge medio
16h 14m
PR unite (30g)
25

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