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fix(auth): discover path-appended OAuth metadata #887

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fix(auth): discover path-appended OAuth metadata #887

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40 changes: 27 additions & 13 deletions crates/rmcp/src/transport/auth.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1409,14 +1409,16 @@ impl AuthorizationManager {
push_candidate("/.well-known/oauth-authorization-server".to_string());
push_candidate("/.well-known/openid-configuration".to_string());
} else {
// Path components present: follow spec priority order
// Path components present: prefer OAuth discovery before OpenID Connect fallbacks.
// 1. OAuth 2.0 with path insertion
push_candidate(format!("/.well-known/oauth-authorization-server/{trimmed}"));
// 2. OpenID Connect with path insertion
// 2. OAuth 2.0 with path appending
push_candidate(format!("/{trimmed}/.well-known/oauth-authorization-server"));
// 3. OpenID Connect with path insertion
push_candidate(format!("/.well-known/openid-configuration/{trimmed}"));
// 3. OpenID Connect with path appending
// 4. OpenID Connect with path appending
push_candidate(format!("/{trimmed}/.well-known/openid-configuration"));
// 4. Canonical OAuth fallback (without path suffix)
// 5. Canonical OAuth fallback (without path suffix)
push_candidate("/.well-known/oauth-authorization-server".to_string());
}

Expand Down Expand Up @@ -2684,61 +2686,73 @@ mod tests {

let base_url = Url::parse("https://auth.example.com/tenant1").unwrap();
let urls = AuthorizationManager::generate_discovery_urls(&base_url);
assert_eq!(urls.len(), 4);
assert_eq!(urls.len(), 5);
assert_eq!(
urls[0].as_str(),
"https://auth.example.com/.well-known/oauth-authorization-server/tenant1"
);
assert_eq!(
urls[1].as_str(),
"https://auth.example.com/.well-known/openid-configuration/tenant1"
"https://auth.example.com/tenant1/.well-known/oauth-authorization-server"
);
assert_eq!(
urls[2].as_str(),
"https://auth.example.com/tenant1/.well-known/openid-configuration"
"https://auth.example.com/.well-known/openid-configuration/tenant1"
);
assert_eq!(
urls[3].as_str(),
"https://auth.example.com/tenant1/.well-known/openid-configuration"
);
assert_eq!(
urls[4].as_str(),
"https://auth.example.com/.well-known/oauth-authorization-server"
);

let base_url = Url::parse("https://auth.example.com/v1/mcp/").unwrap();
let urls = AuthorizationManager::generate_discovery_urls(&base_url);
assert_eq!(urls.len(), 4);
assert_eq!(urls.len(), 5);
assert_eq!(
urls[0].as_str(),
"https://auth.example.com/.well-known/oauth-authorization-server/v1/mcp"
);
assert_eq!(
urls[1].as_str(),
"https://auth.example.com/.well-known/openid-configuration/v1/mcp"
"https://auth.example.com/v1/mcp/.well-known/oauth-authorization-server"
);
assert_eq!(
urls[2].as_str(),
"https://auth.example.com/v1/mcp/.well-known/openid-configuration"
"https://auth.example.com/.well-known/openid-configuration/v1/mcp"
);
assert_eq!(
urls[3].as_str(),
"https://auth.example.com/v1/mcp/.well-known/openid-configuration"
);
assert_eq!(
urls[4].as_str(),
"https://auth.example.com/.well-known/oauth-authorization-server"
);

let base_url = Url::parse("https://auth.example.com/tenant1/subtenant").unwrap();
let urls = AuthorizationManager::generate_discovery_urls(&base_url);
assert_eq!(urls.len(), 4);
assert_eq!(urls.len(), 5);
assert_eq!(
urls[0].as_str(),
"https://auth.example.com/.well-known/oauth-authorization-server/tenant1/subtenant"
);
assert_eq!(
urls[1].as_str(),
"https://auth.example.com/.well-known/openid-configuration/tenant1/subtenant"
"https://auth.example.com/tenant1/subtenant/.well-known/oauth-authorization-server"
);
assert_eq!(
urls[2].as_str(),
"https://auth.example.com/tenant1/subtenant/.well-known/openid-configuration"
"https://auth.example.com/.well-known/openid-configuration/tenant1/subtenant"
);
assert_eq!(
urls[3].as_str(),
"https://auth.example.com/tenant1/subtenant/.well-known/openid-configuration"
);
assert_eq!(
urls[4].as_str(),
"https://auth.example.com/.well-known/oauth-authorization-server"
);
}
Expand Down
46 changes: 46 additions & 0 deletions crates/rmcp/tests/test_client_credentials.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,25 @@ async fn start_mock_server() -> (String, SocketAddr) {
(base_url, addr)
}

async fn start_path_append_metadata_server() -> (String, SocketAddr) {
let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
let addr = listener.local_addr().unwrap();
let base_url = format!("http://{}", addr);

let app = Router::new()
.route(
"/mcp/.well-known/oauth-authorization-server",
get(auth_server_metadata_handler),
)
.route("/token", post(token_handler));

tokio::spawn(async move {
axum::serve(listener, app).await.unwrap();
});

(base_url, addr)
}

#[tokio::test]
async fn test_client_credentials_flow_client_secret() {
let (base_url, _addr) = start_mock_server().await;
Expand All @@ -162,6 +181,33 @@ async fn test_client_credentials_flow_client_secret() {
assert_eq!(token, "m2m-access-token-12345");
}

#[tokio::test]
async fn test_client_credentials_discovers_path_append_oauth_metadata() {
let (base_url, _addr) = start_path_append_metadata_server().await;
let resource_url = format!("{base_url}/mcp");

let mut oauth_state = OAuthState::new(&resource_url, None).await.unwrap();

let config = ClientCredentialsConfig::ClientSecret {
client_id: "test-m2m-client".to_string(),
client_secret: "test-m2m-secret".to_string(),
scopes: vec!["read".to_string()],
resource: Some(resource_url),
};

oauth_state
.authenticate_client_credentials(config)
.await
.unwrap();

let manager = oauth_state
.into_authorization_manager()
.expect("Should be in Authorized state");

let token = manager.get_access_token().await.unwrap();
assert_eq!(token, "m2m-access-token-12345");
}

#[tokio::test]
async fn test_client_credentials_invalid_secret() {
let (base_url, _addr) = start_mock_server().await;
Expand Down