Two isolated hardenings of the opt-in remote/diagnostics WS server, surfaced by
the session-wide diagnostics audit:
1. WebSocketServer was created with no maxPayload, so ws defaults to 100 MiB per
message. The connection handler runs JSON.parse(raw) on the FIRST message
(the auth frame) before authentication, so any peer past the IP allowlist
could send a huge payload and force a synchronous multi-MB JSON.parse on the
main-process event loop — an unbounded freeze/DoS sink. Diag, auth and WebRTC
signaling messages are all small; cap maxPayload at 256 KiB to close it.
2. sendToClient did ws.send(JSON.stringify(data)) with no readyState/try guard
(unlike broadcast, which checks ws.readyState === 1). A send on a closing
socket, or a stringify throw, escaped the diag-response callback as an
uncaughtException — a potential crash. Mirror broadcast: send only when
readyState === 1, wrapped in try/catch.
Both are isolated to the transport layer with zero redaction surface. The audit's
larger finding — server_health doing O(historySize) synchronous work per request
(6-7 full-config clones + unbounded history walks) — is a real freeze, but ONLY on
the cold opt-in diagnostics path with a large history (this user: 23 rows), and the
safe fix cuts into the credential-redaction collectors (which have leaked twice);
deferred and documented in tasks/todo.md rather than operated under risk.
397/397 tests pass, eslint clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Matches the Real-Debrid-Downloader's rd-diagnostics-mcp model so the read-only
diagnostics agent is reachable over Tailscale (or any private tunnel) the same way
the downloader is, instead of requiring an SSH local-forward.
- lib/ip-allowlist.js (NEW): fail-closed IP allowlist — normalizeIp strips
::ffff:, loopback is always allowed, an empty allowlist accepts loopback ONLY
(fail-closed), exact IP + CIDR (incl. the Tailscale CGNAT range 100.64.0.0/10) +
wildcard rules. The real socket peer IP is the authority (never a forwarded header).
- remote-server.js: rejects non-allowlisted peers at connection (close 4005). Opt-in
via config.allowlist (the existing remote-control server, which passes none, is
unaffected). Loopback always passes, so local + SSH-forward use keeps working.
- Two bind modes (config diagnostics.bindMode): "local" -> 127.0.0.1 (default),
"network" -> 0.0.0.0 but ONLY when a non-empty allowlist is set (else it stays
loopback, fail-closed). The allowlist + token gate access; the tunnel
(Tailscale/WireGuard) is the confidentiality layer (transport is still plaintext ws://).
- The connection code now carries the host: mhu1_<base64url{v,h,p,t,n,fp?,s?}>. The
gateway decode is tolerant of the legacy {port,token,label} keys; connect_server
takes the host from the code (host arg is an optional override). Proven end-to-end:
the integration harness now connects with NO host arg and resolves it from the code.
- Renderer: Sichtbarkeit selector (local/network), public-host input with
suggested-host chips (os.networkInterfaces — the Tailscale IP shows up there),
allowlist textarea (network mode), and network-requires-allowlist validation.
- main.js: bindMode->host, getSuggestedRemoteHosts, host-in-code, allowlist plumbed
into startDiagnosticAgent + the diagnostics IPC (get/save/status).
- docs: rewritten for Tailscale (set the allowlist to your tailnet, put the Tailscale
IP/MagicDNS in the code address — no SSH forward needed).
This supersedes the v3.3.85 hard loopback-lock with the downloader's allowlist model.
Tests: lib/ip-allowlist (8) + remote-server allowlist wiring/loopback (2) + gateway
decode (host short-key + legacy tolerance). 393 app tests + 9 gateway tests + e2e +
host-in-code integration + adversarial all green; lint 0 errors.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Adds the server/app half of a remote-diagnostics system so Claude (via a local
MCP gateway, added separately) can read a server's full state to diagnose
problems: logs, errors, queue/app state, redacted config, system health. All
read-only; security review folded in as hard requirements.
Architecture (design-verified):
- A SECOND, independent RemoteServer instance (diagnosticMode) on its own port
(default 9110, bind 127.0.0.1) with NO capture/input callbacks, so screen
capture and sendInputEvent are structurally unreachable from the diagnostic
path. The existing screen-share server (port 9100) is byte-for-byte unchanged.
- lib/remote-server.js: a `host` bind option, a post-auth `diag-request` branch
that delegates to onDiagnosticRequest and replies with a reqId-correlated
`diag-response`, a `diagnosticMode` guard (capture never spawns), a
timing-safe token compare (length-guarded), and getLastAccess().
- lib/diagnostics-agent.js: handle(op,args) enforces a HARDCODED read-only op
whitelist as the sole authority — no write/exec op, no run_health_check.
- lib/diagnostics-collectors.js: pure, dependency-injected collectors
(server_health one-shot hub, read_log, list_errors, get_queue_state,
get_history, get_config_redacted, get_system_info, list_logs, get_app_events,
get_rotation_state, get_health) reusing support-bundle + stats.
Security (all mandatory, implemented):
- Redaction gates every off-box payload. support-bundle now adds webhookUrl +
diagToken to CRED_KEYS, and exports redactLogText (value-scrub of live secret
strings + pattern-scrub of Discord webhooks / Bearer / api_key= / cookies /
sess ids) + valueScrub + collectSecretValues. read_log takes a logical NAME
(no path traversal); doodstream-debug.log is excluded from the readable set
(it logs live api-key-bearing HTML). grep is length-capped (ReDoS guard).
- diagnostics config subtree (enabled/port/token/label/codeIssuedAt/bindAddress)
defaults OFF, bind 127.0.0.1; deep-merge makes it migration-free. The
server-owned token is preserved against renderer clobber in both
save-global-settings handlers; the diagnostics:* IPC is the only mutator.
- app.requestSingleInstanceLock() (also the approved fix#6) so a relaunch can't
EADDRINUSE-kill the agent and two instances can't clobber the config.
main.js: buildDiagnosticCode (mhu1_ base64url, no host embedded), start/stop +
auto-start-on-launch + stop-on-quit, the four diagnostics:* IPC handlers.
renderer: a "Diagnose-Zugriff" settings subtab (toggle, port, bind-address,
copyable connection code + regenerate, status, read-only security note).
382 tests pass (incl. 11 new: collectors+redaction, agent whitelist, and a live
RemoteServer protocol test proving auth->diag-response correlation, that a
diagnostic client never triggers the capture window, and brute-force lockout).
Lint clean (0 errors). Smoke boots identically to baseline. The standalone MCP
gateway package + operator setup docs land in a follow-up commit.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The error handler was missing clearTimeout for the auth timeout timer
and didn't clean up authenticated client state (signaling disconnect,
destroying capture window when last client drops).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
