membershipd never called Server.UseReplicatedNonces, so every node kept a
per-process anti-replay cache and a signed request accepted on node A could be
replayed to node B (200+200). This wires the shared JetStream KV nonce bucket on
any clustered node, closing the cross-node replay hole.
Bootstrap: under enforce the service needs JetStream on its own embedded server,
but the data plane only accepts allowlisted clients. Resolved with an ephemeral
internal service identity the authenticator recognizes and grants full
permissions (NewNkeyAuthenticatorACLInternal), connected over the in-process
transport (no TLS/CA needed for the self-connection).
Hard rule: --cluster-name != "" means the replicated nonce bucket is mandatory;
if it cannot be created the node refuses to start (wireReplicatedNonces returns a
fatal error) rather than run insecurely. Standalone nodes keep the in-memory
cache unchanged (branch-by-abstraction: no JetStream dependency added).
Changes:
- busauth: NewNkeyAuthenticatorACLInternal + fullPermissions for the internal id.
- cmd/membershipd: connectInternalJS (in-process, privileged) / connectExternalJS;
wireReplicatedNonces helper; main wires it when clustered; --kv-replicas flag.
Tests (regression of audit 0008 N3):
- TestAttack0008_N3: 2 clustered nodes share the bucket, cross-node replay -> 401.
- TestAttack0008_N3_StandaloneKeepsLocalCache: standalone needs no JetStream,
same-node replay still 401.
- TestAttack0008_N3_ClusteredRequiresJetStream: clustered + no JetStream -> fatal.
- TestInternalConnPrivilegedUnderEnforce / ...OutsiderRejected: the privileged
self-connection works under enforce and no other identity can claim it.
CGO_ENABLED=0 go build/vet/test green; govulncheck 0 reachable.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Closes the residual the 0004 hardening deferred: the NATS authenticator
can now confine a registered peer to the subjects of the rooms it
belongs to, instead of letting any registered identity sub/pub on any
subject. The dynamic-membership reconnection model the audit named is
provided by client.RefreshSession.
pkg/busauth:
- verifyNkey factors out the shared nkey verification.
- NewNkeyAuthenticatorACL + PermissionsFunc: an authenticator that, after
authorizing, derives and RegisterUser()s per-subject permissions. A
derivation error denies the connection (fail closed).
pkg/membership:
- SubjectACLFor(store) maps a signing pubkey to the subjects it may use:
the subject of every room it belongs to, plus the client infrastructure
subjects (_INBOX.>, $JS.API.> for request/reply and the persisted plane).
pkg/client:
- RefreshSession() rebuilds the data-plane connection so the authenticator
re-derives permissions after a membership change (NATS freezes
permissions at connect time). It retains the seeds/options to reconnect;
active subscriptions are dropped and must be re-made (documented).
Tests (DoD: isolation + refresh):
- TestSubjectACLIsolation: alice (member of room.A) may sub/pub room.A but
is DENIED sub and pub on room.B (permissions violation), and never reads
bob's room.B traffic; bob never receives alice's cross-room publish.
- TestRefreshSessionGainsNewRoom: alice has no permission for room B until
she is added and calls RefreshSession; the reconnect grants the subject
and she then receives room B traffic.
Scope note: the per-subject ACL authenticator is opt-in (NewServer/
membershipd keep the open authenticator by default) and is wired in with
the decentralized boot path; auto-RefreshSession on every membership
change (fully transparent) remains for 0003f. Master behavior unchanged.
busauth.NewNkeyAuthenticator verifies a client's nkey signature over the
server nonce (decoding like nats-server: raw-url then std base64), maps the
nkey to its Ed25519 hex, and consults an injected IsAuthorized predicate.
Checking on every connection (rather than a static Options.Nkeys map) means
revoking a user denies its next connection with no restart. embeddednats
gains StartHostAuth(auth) and sets AlwaysEnableNonce so the server advertises
the nonce nkey clients need; Start/StartHost stay open (auth=nil) for dev.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
egutierrez
agent