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zeekay
5ae17289d2
Red round 5 finding B1. The embedded dispatcher on --threshold-listen
was an anonymous local signing oracle:
1. Any process on the host could POST `{"method":"frost.sign",...}`
and obtain signatures with no auth gate (only the API on :9800
enforced MPC_INTERNAL_API_KEY).
2. An operator typo `MPC_THRESHOLD_LISTEN=0.0.0.0:7300` exposed it
cluster-wide.
3. Any SSRF inside mpcd pivoted into the dispatcher.
Fix mirrors the existing internal-API auth pattern (cmd/mpcd/main.go
line ~456):
- Auth token: read MPC_THRESHOLD_AUTH_TOKEN; if unset, derive a
deterministic per-cluster token from the node Ed25519 seed
(SHA-256(seed || "mpc-threshold-rpc") hex). All nodes share the
same key without extra config; log warns when derivation is used.
Server.SetAuthToken installs the gate.
- Loopback bind: refuse non-loopback addr unless
MPC_THRESHOLD_ALLOW_REMOTE=1 — operators must explicitly
acknowledge the exposure. Bare `:port` (= 0.0.0.0) is NOT loopback.
Also picks up luxfi/threshold v1.6.10 which removes the pulsar/corona
in-memory-token surface (Red HIGH B2) — pulsar.*/corona.* now return a
typed "not yet implemented" error.
Tests:
- TestIsThresholdLoopback locks the loopback predicate (8 cases:
127.0.0.1, [::1], localhost OK; 0.0.0.0, :port, RFC1918 refused).
- TestEmbeddedDispatcher_AuthGate proves 401 on missing/wrong token,
200 on valid token through the dispatcher mpcd installs.
4 tests pass in cmd/mpcd (was 2, +2).