Add client_secret_basic authentication support (#1334)

Co-authored-by: Paul Carleton <paulc@anthropic.com>

src/mcp/server/auth/handlers/revoke.py

@@ -39,6 +39,17 @@ class RevocationHandler:
         """
         Handler for the OAuth 2.0 Token Revocation endpoint.
         """
+        try:
+            client = await self.client_authenticator.authenticate_request(request)
+        except AuthenticationError as e:  # pragma: no cover
+            return PydanticJSONResponse(
+                status_code=401,
+                content=RevocationErrorResponse(
+                    error="unauthorized_client",
+                    error_description=e.message,
+                ),
+            )
+
         try:
             form_data = await request.form()
             revocation_request = RevocationRequest.model_validate(dict(form_data))
@@ -51,20 +62,6 @@ class RevocationHandler:
                 ),
             )
 
-        # Authenticate client
-        try:
-            client = await self.client_authenticator.authenticate(
-                revocation_request.client_id, revocation_request.client_secret
-            )
-        except AuthenticationError as e:  # pragma: no cover
-            return PydanticJSONResponse(
-                status_code=401,
-                content=RevocationErrorResponse(
-                    error="unauthorized_client",
-                    error_description=e.message,
-                ),
-            )
-
         loaders = [
             self.provider.load_access_token,
             partial(self.provider.load_refresh_token, client),