fix(auth): handle missing client-credentials scopes safely

sqsge · sqsge · commit f73e34792c61 · 2026-06-16T11:03:28.000+08:00
diff --git a/src/google/adk/auth/auth_handler.py b/src/google/adk/auth/auth_handler.py
@@ -36,6 +36,17 @@
   AUTHLIB_AVAILABLE = False
 
 
+def _normalize_oauth_scopes(
+    scopes: dict[str, str] | list[str] | None,
+) -> list[str]:
+  """Normalize OAuth scopes into the list shape expected by authlib."""
+  if not scopes:
+    return []
+  if isinstance(scopes, dict):
+    return list(scopes.keys())
+  return list(scopes)
+
+
 class AuthHandler:
   """A handler that handles the auth flow in Agent Development Kit to help
   orchestrate the credential request and response flow (e.g. OAuth flow)
@@ -164,7 +175,7 @@ def generate_auth_uri(
 
     if isinstance(auth_scheme, OpenIdConnectWithConfig):
       authorization_endpoint = auth_scheme.authorization_endpoint
-      scopes = auth_scheme.scopes
+      scopes = _normalize_oauth_scopes(auth_scheme.scopes)
     else:
       authorization_endpoint = (
           auth_scheme.flows.implicit
@@ -176,17 +187,20 @@ def generate_auth_uri(
           or auth_scheme.flows.password
           and auth_scheme.flows.password.tokenUrl
       )
-      scopes = (
-          auth_scheme.flows.implicit
-          and auth_scheme.flows.implicit.scopes
-          or auth_scheme.flows.authorizationCode
-          and auth_scheme.flows.authorizationCode.scopes
-          or auth_scheme.flows.clientCredentials
-          and auth_scheme.flows.clientCredentials.scopes
-          or auth_scheme.flows.password
-          and auth_scheme.flows.password.scopes
-      )
-      scopes = list(scopes.keys())
+      if auth_scheme.flows.implicit:
+        scopes = _normalize_oauth_scopes(auth_scheme.flows.implicit.scopes)
+      elif auth_scheme.flows.authorizationCode:
+        scopes = _normalize_oauth_scopes(
+            auth_scheme.flows.authorizationCode.scopes
+        )
+      elif auth_scheme.flows.clientCredentials:
+        scopes = _normalize_oauth_scopes(
+            auth_scheme.flows.clientCredentials.scopes
+        )
+      elif auth_scheme.flows.password:
+        scopes = _normalize_oauth_scopes(auth_scheme.flows.password.scopes)
+      else:
+        scopes = []
 
     client = OAuth2Session(
         auth_credential.oauth2.client_id,
diff --git a/tests/unittests/auth/test_auth_handler.py b/tests/unittests/auth/test_auth_handler.py
@@ -22,6 +22,7 @@
 from fastapi.openapi.models import APIKeyIn
 from fastapi.openapi.models import OAuth2
 from fastapi.openapi.models import OAuthFlowAuthorizationCode
+from fastapi.openapi.models import OAuthFlowClientCredentials
 from fastapi.openapi.models import OAuthFlows
 from google.adk.auth.auth_credential import AuthCredential
 from google.adk.auth.auth_credential import AuthCredentialTypes
@@ -273,6 +274,35 @@ def test_generate_auth_uri_openid(
     assert "client_id=mock_client_id" in result.oauth2.auth_uri
     assert result.oauth2.state == "mock_state"
 
+  @patch("google.adk.auth.auth_handler.OAuth2Session", MockOAuth2Session)
+  def test_generate_auth_uri_client_credentials_with_missing_scopes(
+      self, oauth2_credentials
+  ):
+    """Test client credentials flow tolerates missing scopes."""
+    auth_scheme = OAuth2(
+        flows=OAuthFlows(
+            clientCredentials=OAuthFlowClientCredentials(
+                tokenUrl="https://example.com/oauth2/token"
+            )
+        )
+    )
+    auth_scheme.flows.clientCredentials.scopes = None
+
+    config = AuthConfig(
+        auth_scheme=auth_scheme,
+        raw_auth_credential=oauth2_credentials,
+        exchanged_auth_credential=oauth2_credentials.model_copy(deep=True),
+    )
+
+    handler = AuthHandler(config)
+    result = handler.generate_auth_uri()
+
+    assert (
+        result.oauth2.auth_uri
+        == "https://example.com/oauth2/token?client_id=mock_client_id&scope="
+    )
+    assert result.oauth2.state == "mock_state"
+
   @patch("google.adk.auth.auth_handler.OAuth2Session")
   def test_generate_auth_uri_pkce(
       self, mock_oauth2_session, oauth2_auth_scheme, oauth2_credentials
