fix(mcp): refuse unauthenticated HTTP on non-loopback hosts; optional bearer-token auth

[ruvnet]

Refs #3598.

What was wrong

ruflo mcp start -t http started with no authentication. @claude-flow/mcp's HTTP transport enforces a bearer token only when config.auth is set, and the CLI never set it. On published @claude-flow/cli 3.54.1, with the default --host localhost, a raw initialize followed by tools/call system_info succeeds with no credentials, and a spoofed Host header is accepted. With --host 0.0.0.0 the same is reachable from the network. Browser CSRF and DNS rebinding were blocked only incidentally by the CORS code.

What this PR does

1. Refuses to start on a non-loopback host (0.0.0.0, ::, a LAN IP, ...) unless the server is authenticated or the operator opts out with RUFLO_MCP_ALLOW_UNAUTHENTICATED_HTTP=1. The gate runs first in startHttpServer, before any import or bind.
2. Adds optional bearer-token auth for the HTTP transport:
   • RUFLO_MCP_HTTP_TOKEN=<token> (preferred), --auth-token-file <path>, or --auth-token <token> (visible in argv). Precedence: flag, file, env.
   • Every request needs Authorization: Bearer <token>: /rpc, /mcp (POST and the SSE GET) and /info. A failure is one generic 401 with no detail, no WWW-Authenticate hints beyond Bearer, and nothing about the token in the body or logs.
   • Constant-time comparison (crypto.timingSafeEqual over SHA-256 digests, so length does not leak). Auth runs after CORS and the rate limiter and before the body parser, so an unauthenticated client cannot make the server read a body. The body size cap is unchanged.
   • GET/HEAD /health stays public and returns only {"status":"ok"} when auth is on (no timestamp, no connection count). Look-alike paths still need the token.
   • Token format: 16-512 printable ASCII characters, no spaces. A malformed token is a startup error (never silently "no auth"), and the value is not echoed.
   • A token lifts the non-loopback refusal (no opt-out needed).
3. Fixes a fail-open in the transport: auth enabled with an empty tokens list used to accept any Bearer <anything>. It now accepts nothing.
4. The token is redacted from the manager's starting event. --auth-token with -t websocket is rejected, because the standalone websocket transport has no working token check.

What is NOT closed

• Loopback with no token is still unauthenticated, by design and unchanged: any local process can call every tool, and a web page can reach it via DNS rebinding (there is still no Host allow-list). Set RUFLO_MCP_HTTP_TOKEN whenever the HTTP transport is used; mcp start now prints a warning in that case.
• Loopback spellings other than exactly localhost, 127.0.0.1, ::1 (127.0.0.2, [::1], LOCALHOST, 0:0:0:0:0:0:0:1) fail closed: they need a token or the opt-out.
• The standalone -t websocket transport on a non-loopback host is refused without the opt-out, and a token cannot unlock it.
• The /ws upgrade on the HTTP transport still accepts a ?token= query parameter in addition to the header (existing behaviour, not changed here).
• This is not per-tool authorization: a valid token grants every tool.

The earlier title/description of this PR called this "fail-open by default / CVSS 10". That overstated it: the loopback default was and remains unauthenticated, and the original change only covered non-loopback binds.

Behaviour matrix

--host	no token	token set
localhost, 127.0.0.1, ::1	starts, unauthenticated	starts, token required
0.0.0.0, ::, LAN IP, 127.0.0.2, [::1], LOCALHOST	refuses (exit 1, message names the token and the opt-out)	starts, token required
same, with RUFLO_MCP_ALLOW_UNAUTHENTICATED_HTTP=1	starts, unauthenticated	starts, token required

Breaking change

Anyone binding off loopback, for example Docker with --host 0.0.0.0, must now set RUFLO_MCP_HTTP_TOKEN (and send the header from clients) or set RUFLO_MCP_ALLOW_UNAUTHENTICATED_HTTP=1. Otherwise mcp start exits with an error. Loopback users are unaffected.

Tests

• cli/__tests__/mcp-http-nonloopback-auth-gate.test.ts (34): drives the real MCPServerManager.start() with @claude-flow/mcp mocked. 0.0.0.0, :: and a LAN IP are refused with the documented message and never reach createMCPServer; they start with the opt-out or a token (and the token reaches the transport config); loopback hosts start; token resolution/validation; the full decision matrix. Mutation check: deleting the throw in startHttpServer fails 5 of these tests (the previous version of this PR's tests stayed green).
• mcp/__tests__/http-transport-auth.test.ts (26): no header, wrong token, near-miss tokens, right token, malformed headers, unicode tokens, timingSafeEqual is used, no token in logs, body cap kept, auth before body parse, /health behaviour, CORS preflight unchanged, fail-closed with no tokens, and bypass attempts (method override headers and params, HEAD/OPTIONS, bearer/BEARER, duplicate and comma-joined Authorization, path variants, forged Host/X-Forwarded-*, credentials in query or body).
• Also run: mcp package 107/107; 7 related cli test files 501/501; tsc --noEmit for cli shows the same 5 pre-existing errors as before (none in touched files). One existing test's mcp-server.js mock needed the two new exports.
• Live check through MCPServerManager: token on 0.0.0.0 gives no header 401, wrong token 401, right token 200, /health 200; loopback with no token gives 200 for all three (unchanged).

Docs: v3/@claude-flow/cli/README.md ("HTTP transport security") and ruflo mcp start --help. No version bumps or lockfile changes.

Human review required; not self-merging.

🤖 Generated with RuFlo

[ruvnet]

CI failure on 87f5441f (Test Suite, ubuntu-latest), fixed in 4212c14f.

Test Suite (ubuntu-latest) failed: the 3 new end-to-end tests in mcp-http-nonloopback-auth-gate.test.ts all errored with ERR_MODULE_NOT_FOUND when spawning bin/cli.js.

Root cause: bin/cli.js is tracked source (always exists) but imports dist/src/index.js at runtime. This repo's Test Suite CI job never builds @claude-flow/cli's own dist/ — only @claude-flow/security and @claude-flow/cli-core get a targeted build step there (see .github/workflows/ci.yml's own comments documenting the same class of gap for those two packages). My test file's CLI_BUILT check only verified bin/cli.js's presence (the same pattern the existing mcp-http-foreground-2984/mcp-http-protocol-tools-2990 e2e tests use), which is always true regardless of build state, so it never actually skipped.

Not this PR's root cause to fix (the CI workflow's build-step gap is pre-existing, shared infra, out of scope for a scoped security patch), but the resulting red test is in code this PR added, so: fixed by checking the real dependency (dist/src/index.js) and skipping the e2e block cleanly via describe.skipIf when it's absent, rather than failing. The 3 unit tests (which don't spawn the CLI, and already independently demonstrate the fix discriminates baseline from candidate) are unaffected.

Verified locally both ways: 6/6 pass when dist/ exists; 3 passed/3 skipped/0 failed when dist/ is removed to simulate CI's actual state. Re-running CI on 4212c14f now.

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[ruvnet]

Follow-up on the CI failure (4212c14f's skip-guard fix still failed identically on the same 3 tests).

Rather than keep guessing at why dist/src/index.js behaves differently in this CI job than in a local repro (and given both pre-existing tests of this exact shape — mcp-http-foreground-2984.test.ts, mcp-http-protocol-tools-2990.test.ts — are already in scripts/ci-test-baseline.txt as known-failing there, whose own header forbids adding a third entry: "Never add entries to make a regression green"), I removed the dependency entirely.

4cc5ca92 extracts the full startHttpServer() gate into pure, synchronous, exported functions (isLoopbackHost, isUnauthenticatedHttpAllowed, composed into shouldRefuseUnauthenticatedHttp) and rewrites the test file to unit-test them directly — no process spawn, no port bind, no build dependency, so it can't hit this or any other CI-environment-specific failure mode. Stash-isolated: 5/8 new tests fail against true baseline, 8/8 pass on the candidate. No behavior change to startHttpServer() beyond the refactor (verified: same inputs → same refuse/allow decision as the inline version). The actual end-to-end behavior (server refuses non-loopback by default, starts with explicit opt-out, loopback unaffected) was already verified manually during development — see the evidence in #3598/this PR's own description — this just makes the committed regression test immune to the CI environment gap rather than fighting it.

Re-running CI on 4cc5ca92 now.

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Generated by Claude Code

[ruvnet]

CI on 4cc5ca92 (the pure-unit-test rewrite): the MCP auth-gate file is now clean — confirmed. The only remaining "unexpected failing file" is v3/@claude-flow/performance/__tests__/benchmarks.test.ts ("Performance Validation should demonstrate consistent speedup": expected 0.3445 to be greater than 0.5).

This is not this PR's: it's a timing-based wall-clock speedup assertion in a package (@claude-flow/performance) this PR never touches, and it's the same shape of resource-contention flake I independently observed locally in this sandbox's full-suite run tonight (an unrelated ONNX-model-loading test intermittently timing out under parallel load — see the Evaluation Receipt in #3598/this PR). Re-running the failed job once now (rerun_failed_jobs on run 36827212929) to confirm, per policy.

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Generated by Claude Code

[ruvnet]

CI is green on 4cc5ca92. The re-run of Test Suite (ubuntu-latest) confirmed the @claude-flow/performance benchmark failure was the flake it looked like (unrelated timing-based speedup assertion, package untouched by this PR) — it now shows success. All other check runs on this head SHA are green/skipped, and the branch is mergeable (mergeable_state: clean).

Updated the PR description to match the final implementation (pure unit tests against the exported gate functions, 8/8 passing, no process spawn) and to document the two CI round-trips for anyone reviewing the commit history.

This PR is ready for human review per standing Dream Cycle policy (draft, no self-merge). I'll keep watching for review comments or any future CI regression.

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Generated by Claude Code