# Copyright 2016 Google Inc. # # 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. """Google Compute Engine credentials. This module provides authentication for application running on Google Compute Engine using the Compute Engine metadata server. """ from google.auth import credentials from google.auth import exceptions from google.auth.compute_engine import _metadata class Credentials(credentials.ReadOnlyScoped, credentials.Credentials): """Compute Engine Credentials. These credentials use the Google Compute Engine metadata server to obtain OAuth 2.0 access tokens associated with the instance's service account. For more information about Compute Engine authentication, including how to configure scopes, see the `Compute Engine authentication documentation`_. .. note:: Compute Engine instances can be created with scopes and therefore these credentials are considered to be 'scoped'. However, you can not use :meth:`~google.auth.credentials.ScopedCredentials.with_scopes` because it is not possible to change the scopes that the instance has. Also note that :meth:`~google.auth.credentials.ScopedCredentials.has_scopes` will not work until the credentials have been refreshed. .. _Compute Engine authentication documentation: https://cloud.google.com/compute/docs/authentication#using """ def __init__(self, service_account_email='default'): """ Args: service_account_email (str): The service account email to use, or 'default'. A Compute Engine instance may have multiple service accounts. """ super(Credentials, self).__init__() self._service_account_email = service_account_email def _retrieve_info(self, request): """Retrieve information about the service account. Updates the scopes and retrieves the full service account email. Args: request (google.auth.transport.Request): The object used to make HTTP requests. """ info = _metadata.get_service_account_info( request, service_account=self._service_account_email) self._service_account_email = info['email'] self._scopes = info['scopes'] def refresh(self, request): """Refresh the access token and scopes. Args: request (google.auth.transport.Request): The object used to make HTTP requests. Raises: google.auth.exceptions.RefreshError: If the Compute Engine metadata service can't be reached if if the instance has not credentials. """ try: self._retrieve_info(request) self.token, self.expiry = _metadata.get_service_account_token( request, service_account=self._service_account_email) except exceptions.TransportError as exc: raise exceptions.RefreshError(exc) @property def service_account_email(self): """The service account email. .. note: This is not guaranteed to be set until :meth`refresh` has been called. """ return self._service_account_email @property def requires_scopes(self): """False: Compute Engine credentials can not be scoped.""" return False