fix(integrations): send api registry credentials only to google api endpoints (v1)

src/google/adk/integrations/api_registry/api_registry.py

@@ -14,18 +14,51 @@
 
 from __future__ import annotations
 
+import os
 from typing import Any
 from typing import Callable
+from urllib.parse import urlparse
 
 from google.adk.agents.readonly_context import ReadonlyContext
 from google.adk.tools.base_toolset import ToolPredicate
 from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
 from google.adk.tools.mcp_tool.mcp_toolset import McpToolset
+from google.adk.utils import _mtls_utils
 import google.auth
-import google.auth.transport.requests
-import httpx
+from google.auth.transport import mtls
+from google.auth.transport import requests as requests_auth
+import requests
 
 API_REGISTRY_URL = "https://cloudapiregistry.googleapis.com"
+API_REGISTRY_MTLS_URL = "https://cloudapiregistry.mtls.googleapis.com"
+
+
+def _get_api_registry_url(client_cert_source: Any | None = None) -> str:
+  """Returns the base URL based on mTLS configuration and cert availability."""
+  use_mtls_endpoint_str = os.getenv(
+      "GOOGLE_API_USE_MTLS_ENDPOINT", _mtls_utils.MtlsEndpoint.AUTO.value
+  ).lower()
+  try:
+    use_mtls_endpoint = _mtls_utils.MtlsEndpoint(use_mtls_endpoint_str)
+  except ValueError:
+    use_mtls_endpoint = _mtls_utils.MtlsEndpoint.AUTO
+  if (use_mtls_endpoint is _mtls_utils.MtlsEndpoint.ALWAYS) or (
+      use_mtls_endpoint is _mtls_utils.MtlsEndpoint.AUTO
+      and client_cert_source is not None
+  ):
+    return API_REGISTRY_MTLS_URL
+  return API_REGISTRY_URL
+
+
+def _is_google_api(url: str) -> bool:
+  """Checks if the given URL points to a Google API endpoint over https."""
+  parsed_url = urlparse(url)
+  if parsed_url.scheme != "https" or not parsed_url.hostname:
+    return False
+  return (
+      parsed_url.hostname == "googleapis.com"
+      or parsed_url.hostname.endswith(".googleapis.com")
+  )
 
 
 class ApiRegistry:
@@ -53,19 +86,38 @@ def __init__(
     self._mcp_servers: dict[str, dict[str, Any]] = {}
     self._header_provider = header_provider
 
-    url = f"{API_REGISTRY_URL}/v1beta/projects/{self.api_registry_project_id}/locations/{self.location}/mcpServers"
+    use_client_cert = _mtls_utils.use_client_cert_effective()
+    client_cert_source = None
+    if use_client_cert:
+      client_cert_source = (
+          mtls.default_client_cert_source()
+          if mtls.has_default_client_cert_source()
+          else None
+      )
+    base_url = _get_api_registry_url(client_cert_source)
+
+    url = f"{base_url}/v1beta/projects/{self.api_registry_project_id}/locations/{self.location}/mcpServers"
 
     try:
-      headers = self._get_auth_headers()
-      headers["Content-Type"] = "application/json"
+      quota_project_id = getattr(self._credentials, "quota_project_id", None)
+      headers = {
+          "Content-Type": "application/json",
+      }
+      if quota_project_id:
+        headers["x-goog-user-project"] = quota_project_id
+
       page_token = None
-      with httpx.Client() as client:
+      with requests_auth.AuthorizedSession(
+          credentials=self._credentials
+      ) as session:
+        if use_client_cert:
+          session.configure_mtls_channel(client_cert_source)
         while True:
           params = {}
           if page_token:
             params["pageToken"] = page_token
 
-          response = client.get(url, headers=headers, params=params)
+          response = session.get(url, headers=headers, params=params)
           response.raise_for_status()
           data = response.json()
           mcp_servers_list = data.get("mcpServers", [])
@@ -77,7 +129,7 @@ def __init__(
           page_token = data.get("nextPageToken")
           if not page_token:
             break
-    except (httpx.HTTPError, ValueError) as e:
+    except (requests.exceptions.RequestException, ValueError) as e:
       # Handle error in fetching or parsing tool definitions
       raise RuntimeError(
           f"Error fetching MCP servers from API Registry: {e}"
@@ -110,12 +162,18 @@ def get_toolset(
       raise ValueError(f"MCP server {mcp_server_name} has no URLs.")
 
     mcp_server_url = server["urls"][0]
-    headers = self._get_auth_headers()
 
     # Only prepend "https://" if the URL doesn't already have a scheme
     if not mcp_server_url.startswith(("http://", "https://")):
       mcp_server_url = "https://" + mcp_server_url
 
+    # A registry entry can name any host, so the caller's own credentials are
+    # only attached to Google API endpoints. Other servers get their headers
+    # from the header_provider.
+    headers = (
+        self._get_auth_headers() if _is_google_api(mcp_server_url) else None
+    )
+
     return McpToolset(
         connection_params=StreamableHTTPConnectionParams(
             url=mcp_server_url,

src/google/adk/utils/_mtls_utils.py

@@ -0,0 +1,41 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Utilities for mTLS regional endpoint resolution."""
+
+from __future__ import annotations
+
+import enum
+import os
+
+from google.auth.transport import mtls
+
+
+class MtlsEndpoint(enum.Enum):
+  """Enum for the mTLS endpoint setting."""
+
+  AUTO = "auto"
+  ALWAYS = "always"
+  NEVER = "never"
+
+
+def use_client_cert_effective() -> bool:
+  """Returns whether client certificate should be used for mTLS."""
+  try:
+    return bool(mtls.should_use_client_cert())
+  except (ImportError, AttributeError):
+    return (
+        os.getenv("GOOGLE_API_USE_CLIENT_CERTIFICATE", "false").lower()
+        == "true"
+    )