busauth.LoadCATLSConfig turns a ca.crt path into a *tls.Config trusting only
that private CA (clients must pin it; the system roots would reject a
self-signed server cert). busauth.ServerTLSConfig loads the server keypair.
client.Options gains TLS; NewWithOptions calls nats.Secure when set, so the
data-plane connection is encrypted and the server pinned.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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>
A NATS nkey is an Ed25519 keypair, so the bus reuses each peer's signing
identity for the data plane instead of minting new key material. ClientNkey
derives the user nkey public string and a nonce-signing callback from the
peer's Ed25519 private key (its first 32 bytes are the nkey seed);
SignPubHexFromNkey maps a presented nkey back to the allowlist's hex key;
NkeyPublicFromSignPub is the public-only derivation.
This is NATS-specific transport glue kept in the app, not promoted to the
registry, to avoid pulling nats-io/nkeys into the multi-domain registry
module. The dedicated round-trip test runs first (spec requirement): it
proves the nkey signature equals the identity's raw Ed25519 signature and
that the nkey maps back to the identity's hex.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
egutierrez