Merge pull request #972 from awork-io/oauth-mcp-metadata

fix: align external OAuth metadata with MCP path

Author: taylorwilsdon

auth/external_oauth_provider.py

@@ -80,6 +80,8 @@ def __init__(
     ):
         """Initialize and store client credentials for token validation."""
         self._resource_server_url = resource_server_url
+        if resource_server_url and "resource_base_url" not in kwargs:
+            kwargs["resource_base_url"] = resource_server_url
         super().__init__(client_id=client_id, client_secret=client_secret, **kwargs)
         # Store credentials as they're not exposed by parent class
         self._client_id = client_id
@@ -150,7 +152,7 @@ async def verify_token(self, token: str) -> Optional[AccessToken]:
         # For JWT tokens, use parent class implementation
         return await super().verify_token(token)
 
-    def get_routes(self, **kwargs) -> list[Route]:
+    def get_routes(self, mcp_path: str | None = None) -> list[Route]:
         """
         Get OAuth routes for external provider mode.
 
@@ -159,7 +161,7 @@ def get_routes(self, **kwargs) -> list[Route]:
         (/authorize, /token, etc.) since tokens are issued by Google directly.
 
         Args:
-            **kwargs: Additional arguments passed by FastMCP (e.g., mcp_path)
+            mcp_path: Path where FastMCP mounts the protected MCP endpoint.
 
         Returns:
             List of routes - only protected resource metadata
@@ -172,10 +174,18 @@ def get_routes(self, **kwargs) -> list[Route]:
             )
             return []
 
+        self.set_mcp_path(mcp_path)
+        resource_url = self._get_resource_url(mcp_path)
+        if not resource_url:
+            logger.warning(
+                "ExternalOAuthProvider: protected resource URL could not be resolved"
+            )
+            return []
+
         # Create protected resource routes that point to Google as the authorization server
         # Pass strings directly - Pydantic validates them during model construction
         protected_routes = create_protected_resource_routes(
-            resource_url=self.resource_server_url,
+            resource_url=resource_url,
             authorization_servers=[GOOGLE_ISSUER_URL],
             scopes_supported=self.required_scopes,
             resource_name="Google Workspace MCP",

tests/core/test_well_known_cache_control_middleware.py

@@ -233,3 +233,53 @@ def test_configured_server_applies_no_cache_to_served_oauth_discovery_routes(
     # Ensure we did not create a shadow route at the wrong path.
     wrong_path = client.get("/.well-known/oauth-protected-resource")
     assert wrong_path.status_code == 404
+
+
+def test_external_oauth_metadata_matches_mcp_resource_and_challenge(monkeypatch):
+    monkeypatch.setenv("MCP_ENABLE_OAUTH21", "true")
+    monkeypatch.setenv("GOOGLE_OAUTH_CLIENT_ID", "dummy-client")
+    monkeypatch.setenv("GOOGLE_OAUTH_CLIENT_SECRET", "dummy-secret")
+    monkeypatch.setenv("WORKSPACE_MCP_BASE_URI", "http://localhost")
+    monkeypatch.setenv("WORKSPACE_MCP_PORT", "8000")
+    monkeypatch.setenv("WORKSPACE_EXTERNAL_URL", "https://workspace.example.com")
+    monkeypatch.setenv("EXTERNAL_OAUTH21_PROVIDER", "true")
+    monkeypatch.setenv("WORKSPACE_MCP_STATELESS_MODE", "true")
+
+    import core.server as core_server
+    from auth.oauth_config import reload_oauth_config
+
+    reload_oauth_config()
+    core_server = importlib.reload(core_server)
+    core_server.set_transport_mode("streamable-http")
+    core_server.configure_server_for_http()
+
+    app = core_server.server.http_app(transport="streamable-http", path="/mcp")
+    client = TestClient(app)
+
+    protected_resource = client.get("/.well-known/oauth-protected-resource/mcp")
+    assert protected_resource.status_code == 200
+    assert protected_resource.json()["resource"] == "https://workspace.example.com/mcp"
+
+    wrong_path = client.get("/.well-known/oauth-protected-resource")
+    assert wrong_path.status_code == 404
+
+    challenge = client.post(
+        "/mcp",
+        headers={"Accept": "application/json, text/event-stream"},
+        json={
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "initialize",
+            "params": {
+                "protocolVersion": "2025-06-18",
+                "capabilities": {},
+                "clientInfo": {"name": "test", "version": "1"},
+            },
+        },
+    )
+    assert challenge.status_code == 401
+    assert (
+        'resource_metadata="https://workspace.example.com/'
+        '.well-known/oauth-protected-resource/mcp"'
+        in challenge.headers["www-authenticate"]
+    )