## Summary
- Add an `AllowMissingExpiration bool` field to
`RequireBearerTokenOptions` that opts the middleware out of the existing
`tokenInfo.Expiration.IsZero()` reject.
- Default false preserves the existing strict behaviour: every TokenInfo
must carry an Expiration.
## Motivation
Some IdPs emit session-bound bearer tokens that do not carry a
standalone `exp` claim — the token's lifetime is bounded by an external
session and is not advertised in-band. Resource servers integrating with
such IdPs today have to synthesise a fake Expiration from their
TokenVerifier callback (dishonest data through the auth layer) or fork
`RequireBearerToken` to bypass the check.
This option lets the verifier honestly report "no expiration in the
token" via a zero `Expiration` and have the middleware accept it — while
still applying the elapsed-validity check for tokens that DO carry an
Expiration.
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: Guglielmo Colombo <guglielmoc@google.com>
This change adds support for RFC 9728 (OAuth 2.0 Protected Resource Metadata)
by introducing a `ProtectedResourceMetadataHandler`.
The handler includes built-in CORS support with `Access-Control-Allow-Origin: *`
by default, as OAuth metadata is public information meant for client discovery.
Documentation includes examples for using custom CORS policies with
popular middleware libraries (github.com/rs/cors and github.com/jub0bs/cors).
The implementation follows RFC 9728 §3.1 for OAuth 2.0 Authorization Server
Metadata discovery, enabling clients to discover protected resource capabilities
and authentication requirements.
Add ErrOAuth error type and handling to match TypeScript SDK behavior.
OAuth protocol errors now return HTTP 400 instead of 500, providing
better error classification for authentication issues.
Changes
- Add ErrOAuth variable for OAuth-specific protocol errors
- Update verify function to return 400 for OAuth errors
- Add test case for OAuth error handling
Fixes compatibility with TypeScript SDK error handling patterns.
Add auth.RequireBearerToken and associated types.
This piece of middleware authenticates clients using OAuth 2.0, as
specified in the MCP spec.
For #237.
Usage:
```
st := mcp.NewStreamableServerTransport(...)
http.Handle(path, auth.RequireBearerToken(verifier, nil)(st.ServeHTTP))
```
