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Ettore Di Giacinto
a1b5c177bc
GET /api/cluster/peer authenticated with the deployment's shared registration token and took the dialling replica's id from ?id= on trust. Every worker holds that token, so anything holding it could open a peer link as any replica: relay through it to every worker tunnel that replica owns, displace a real replica's inbound link by declaring its id, and point the roughly 31 GiB per-session receive window at one replica. Validating the id against the instances table does not fix this, because the attack declares a real replica's id. So the route now checks two credentials and needs both. The shared token still says the dialler belongs to this deployment; a new per-replica credential says which replica it is. The credential follows the per-node worker credential rather than inventing a second mechanism: crypto/rand.Text, stored only as a hex SHA-256, compared in constant time, with no fallback to the shared token. It differs in the stronger direction. A worker's credential is minted by the frontend and handed over once; a replica writes its own instances row, so it mints its own secret, publishes only the hash in the same statement that publishes its address, and never sends the plaintext anywhere but the peer dial. A peer that presents no credential is refused, not waved through. An old replica and an attacker holding the shared token send the same request, so accepting the first accepts the second; there is no safe downgrade here, only a quiet one. The refusal is made loud instead, on both sides, naming the upgrade rather than the network. On the documented frontend-first order a new replica still dials an old one; an old replica cannot dial a new one, which costs relayed requests that land on a not-yet-restarted replica and surfaces as no route, never as absence. A rejected peer gets its own sentinel, ErrPeerRejected, whose unwrap chain carries ErrPeerUnreachable as well and no absence sentinel at all. Keeping the older sentinel means no existing consumer changes behaviour; the cause stays out of the chain, so absence cannot escape through it and nothing can read an authorization failure as a worker that went away. One consequence beyond the fix: a replica with no advertised address has no instances row, so it now cannot dial out either. It was already unreachable inward. The startup error and the docs say so. Registry.Register, NewMembership, NewPeerPool, PeerHandler and RegisterClusterRoutes all gained required arguments, so the identity cannot be dropped without a compile failure. Assisted-by: Claude Opus 5 [claude-code] Signed-off-by: Ettore Di Giacinto <mudler@localai.io>