Implement JWT token auth with transparent auto-renewal.

Replace per-call SSH signing with a two-layer auth system:

Server: AuthInterceptor verifies JWT tokens (HMAC-SHA256 signed with
repo-local jwt.key). Authenticate RPC accepts SSH-signed challenges
and issues 30-day JWTs. Expired-but-valid tokens return a
ReauthChallenge in error details (server-provided nonce for fast
re-auth). Authenticate RPC is exempt from token requirement.

Client: TokenCredentials replaces SSHCredentials as the primary
PerRPCCredentials. NewWithAuth creates clients with auto-renewal —
EnsureAuth obtains initial token, retryOnAuth catches Unauthenticated
errors and re-authenticates transparently. Token cached at
$XDG_STATE_HOME/sgard/token (0600).

CLI: dialRemote() helper handles token loading, connection setup,
and initial auth. Push/pull/prune commands simplified to use it.

Proto: Added Authenticate RPC, AuthenticateRequest/Response,
ReauthChallenge messages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
2026-03-24 00:52:16 -07:00
parent b7b1b27064
commit edef642025
18 changed files with 890 additions and 283 deletions

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@@ -1,4 +1,6 @@
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github.com/golang-jwt/jwt/v5 v5.3.1 h1:kYf81DTWFe7t+1VvL7eS+jKFVWaUnK9cB1qbwn63YCY=
github.com/golang-jwt/jwt/v5 v5.3.1/go.mod h1:fxCRLWMO43lRc8nhHWY6LGqRcf+1gQWArsqaEUEa5bE=
github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
github.com/jonboulle/clockwork v0.5.0 h1:Hyh9A8u51kptdkR+cqRpT1EebBwTn1oK9YfGYbdFz6I=