google/auth/_default.py - platform/external/python/google-auth-library-python - Git at Google

 # Copyright 2015 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.

 """Application default credentials.

 Implements application default credentials and project ID detection.
 """

 import io
 import json
 import logging
 import os
 import warnings

 import six

 from google.auth import environment_vars
 from google.auth import exceptions
 import google.auth.transport._http_client

 _LOGGER = logging.getLogger(__name__)

 # Valid types accepted for file-based credentials.
 _AUTHORIZED_USER_TYPE = "authorized_user"
 _SERVICE_ACCOUNT_TYPE = "service_account"
 _EXTERNAL_ACCOUNT_TYPE = "external_account"
 _VALID_TYPES = (_AUTHORIZED_USER_TYPE, _SERVICE_ACCOUNT_TYPE, _EXTERNAL_ACCOUNT_TYPE)

 # Help message when no credentials can be found.
 _HELP_MESSAGE = """\
 Could not automatically determine credentials. Please set {env} or \
 explicitly create credentials and re-run the application. For more \
 information, please see \
 https://cloud.google.com/docs/authentication/getting-started
 """.format(
     env=environment_vars.CREDENTIALS
 ).strip()

 # Warning when using Cloud SDK user credentials
 _CLOUD_SDK_CREDENTIALS_WARNING = """\
 Your application has authenticated using end user credentials from Google \
 Cloud SDK without a quota project. You might receive a "quota exceeded" \
 or "API not enabled" error. We recommend you rerun \
 `gcloud auth application-default login` and make sure a quota project is \
 added. Or you can use service accounts instead. For more information \
 about service accounts, see https://cloud.google.com/docs/authentication/"""

 # The subject token type used for AWS external_account credentials.
 _AWS_SUBJECT_TOKEN_TYPE = "urn:ietf:params:aws:token-type:aws4_request"


 def _warn_about_problematic_credentials(credentials):
     """Determines if the credentials are problematic.

     Credentials from the Cloud SDK that are associated with Cloud SDK's project
     are problematic because they may not have APIs enabled and have limited
     quota. If this is the case, warn about it.
     """
     from google.auth import _cloud_sdk

     if credentials.client_id == _cloud_sdk.CLOUD_SDK_CLIENT_ID:
         warnings.warn(_CLOUD_SDK_CREDENTIALS_WARNING)


 def load_credentials_from_file(
     filename, scopes=None, default_scopes=None, quota_project_id=None, request=None
 ):
     """Loads Google credentials from a file.

     The credentials file must be a service account key, stored authorized
     user credentials or external account credentials.

     Args:
         filename (str): The full path to the credentials file.
         scopes (Optional[Sequence[str]]): The list of scopes for the credentials. If
             specified, the credentials will automatically be scoped if
             necessary
         default_scopes (Optional[Sequence[str]]): Default scopes passed by a
             Google client library. Use 'scopes' for user-defined scopes.
         quota_project_id (Optional[str]):  The project ID used for
             quota and billing.
         request (Optional[google.auth.transport.Request]): An object used to make
             HTTP requests. This is used to determine the associated project ID
             for a workload identity pool resource (external account credentials).
             If not specified, then it will use a
             google.auth.transport.requests.Request client to make requests.

     Returns:
         Tuple[google.auth.credentials.Credentials, Optional[str]]: Loaded
             credentials and the project ID. Authorized user credentials do not
             have the project ID information. External account credentials project
             IDs may not always be determined.

     Raises:
         google.auth.exceptions.DefaultCredentialsError: if the file is in the
             wrong format or is missing.
     """
     if not os.path.exists(filename):
         raise exceptions.DefaultCredentialsError(
             "File {} was not found.".format(filename)
         )

     with io.open(filename, "r") as file_obj:
         try:
             info = json.load(file_obj)
         except ValueError as caught_exc:
             new_exc = exceptions.DefaultCredentialsError(
                 "File {} is not a valid json file.".format(filename), caught_exc
             )
             six.raise_from(new_exc, caught_exc)

     # The type key should indicate that the file is either a service account
     # credentials file or an authorized user credentials file.
     credential_type = info.get("type")

     if credential_type == _AUTHORIZED_USER_TYPE:
         from google.oauth2 import credentials

         try:
             credentials = credentials.Credentials.from_authorized_user_info(
                 info, scopes=scopes
             )
         except ValueError as caught_exc:
             msg = "Failed to load authorized user credentials from {}".format(filename)
             new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
             six.raise_from(new_exc, caught_exc)
         if quota_project_id:
             credentials = credentials.with_quota_project(quota_project_id)
         if not credentials.quota_project_id:
             _warn_about_problematic_credentials(credentials)
         return credentials, None

     elif credential_type == _SERVICE_ACCOUNT_TYPE:
         from google.oauth2 import service_account

         try:
             credentials = service_account.Credentials.from_service_account_info(
                 info, scopes=scopes, default_scopes=default_scopes
             )
         except ValueError as caught_exc:
             msg = "Failed to load service account credentials from {}".format(filename)
             new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
             six.raise_from(new_exc, caught_exc)
         if quota_project_id:
             credentials = credentials.with_quota_project(quota_project_id)
         return credentials, info.get("project_id")

     elif credential_type == _EXTERNAL_ACCOUNT_TYPE:
         credentials, project_id = _get_external_account_credentials(
             info,
             filename,
             scopes=scopes,
             default_scopes=default_scopes,
             request=request,
         )
         if quota_project_id:
             credentials = credentials.with_quota_project(quota_project_id)
         return credentials, project_id

     else:
         raise exceptions.DefaultCredentialsError(
             "The file {file} does not have a valid type. "
             "Type is {type}, expected one of {valid_types}.".format(
                 file=filename, type=credential_type, valid_types=_VALID_TYPES
             )
         )


 def _get_gcloud_sdk_credentials(quota_project_id=None):
     """Gets the credentials and project ID from the Cloud SDK."""
     from google.auth import _cloud_sdk

     _LOGGER.debug("Checking Cloud SDK credentials as part of auth process...")

     # Check if application default credentials exist.
     credentials_filename = _cloud_sdk.get_application_default_credentials_path()

     if not os.path.isfile(credentials_filename):
         _LOGGER.debug("Cloud SDK credentials not found on disk; not using them")
         return None, None

     credentials, project_id = load_credentials_from_file(
         credentials_filename, quota_project_id=quota_project_id
     )

     if not project_id:
         project_id = _cloud_sdk.get_project_id()

     return credentials, project_id


 def _get_explicit_environ_credentials(quota_project_id=None):
     """Gets credentials from the GOOGLE_APPLICATION_CREDENTIALS environment
     variable."""
     from google.auth import _cloud_sdk

     cloud_sdk_adc_path = _cloud_sdk.get_application_default_credentials_path()
     explicit_file = os.environ.get(environment_vars.CREDENTIALS)

     _LOGGER.debug(
         "Checking %s for explicit credentials as part of auth process...", explicit_file
     )

     if explicit_file is not None and explicit_file == cloud_sdk_adc_path:
         # Cloud sdk flow calls gcloud to fetch project id, so if the explicit
         # file path is cloud sdk credentials path, then we should fall back
         # to cloud sdk flow, otherwise project id cannot be obtained.
         _LOGGER.debug(
             "Explicit credentials path %s is the same as Cloud SDK credentials path, fall back to Cloud SDK credentials flow...",
             explicit_file,
         )
         return _get_gcloud_sdk_credentials(quota_project_id=quota_project_id)

     if explicit_file is not None:
         credentials, project_id = load_credentials_from_file(
             os.environ[environment_vars.CREDENTIALS], quota_project_id=quota_project_id
         )

         return credentials, project_id

     else:
         return None, None


 def _get_gae_credentials():
     """Gets Google App Engine App Identity credentials and project ID."""
     # If not GAE gen1, prefer the metadata service even if the GAE APIs are
     # available as per https://google.aip.dev/auth/4115.
     if os.environ.get(environment_vars.LEGACY_APPENGINE_RUNTIME) != "python27":
         return None, None

     # While this library is normally bundled with app_engine, there are
     # some cases where it's not available, so we tolerate ImportError.
     try:
         _LOGGER.debug("Checking for App Engine runtime as part of auth process...")
         import google.auth.app_engine as app_engine
     except ImportError:
         _LOGGER.warning("Import of App Engine auth library failed.")
         return None, None

     try:
         credentials = app_engine.Credentials()
         project_id = app_engine.get_project_id()
         return credentials, project_id
     except EnvironmentError:
         _LOGGER.debug(
             "No App Engine library was found so cannot authentication via App Engine Identity Credentials."
         )
         return None, None


 def _get_gce_credentials(request=None):
     """Gets credentials and project ID from the GCE Metadata Service."""
     # Ping requires a transport, but we want application default credentials
     # to require no arguments. So, we'll use the _http_client transport which
     # uses http.client. This is only acceptable because the metadata server
     # doesn't do SSL and never requires proxies.

     # While this library is normally bundled with compute_engine, there are
     # some cases where it's not available, so we tolerate ImportError.
     try:
         from google.auth import compute_engine
         from google.auth.compute_engine import _metadata
     except ImportError:
         _LOGGER.warning("Import of Compute Engine auth library failed.")
         return None, None

     if request is None:
         request = google.auth.transport._http_client.Request()

     if _metadata.ping(request=request):
         # Get the project ID.
         try:
             project_id = _metadata.get_project_id(request=request)
         except exceptions.TransportError:
             project_id = None

         return compute_engine.Credentials(), project_id
     else:
         _LOGGER.warning(
             "Authentication failed using Compute Engine authentication due to unavailable metadata server."
         )
         return None, None


 def _get_external_account_credentials(
     info, filename, scopes=None, default_scopes=None, request=None
 ):
     """Loads external account Credentials from the parsed external account info.

     The credentials information must correspond to a supported external account
     credentials.

     Args:
         info (Mapping[str, str]): The external account info in Google format.
         filename (str): The full path to the credentials file.
         scopes (Optional[Sequence[str]]): The list of scopes for the credentials. If
             specified, the credentials will automatically be scoped if
             necessary.
         default_scopes (Optional[Sequence[str]]): Default scopes passed by a
             Google client library. Use 'scopes' for user-defined scopes.
         request (Optional[google.auth.transport.Request]): An object used to make
             HTTP requests. This is used to determine the associated project ID
             for a workload identity pool resource (external account credentials).
             If not specified, then it will use a
             google.auth.transport.requests.Request client to make requests.

     Returns:
         Tuple[google.auth.credentials.Credentials, Optional[str]]: Loaded
             credentials and the project ID. External account credentials project
             IDs may not always be determined.

     Raises:
         google.auth.exceptions.DefaultCredentialsError: if the info dictionary
             is in the wrong format or is missing required information.
     """
     # There are currently 2 types of external_account credentials.
     if info.get("subject_token_type") == _AWS_SUBJECT_TOKEN_TYPE:
         # Check if configuration corresponds to an AWS credentials.
         from google.auth import aws

         credentials = aws.Credentials.from_info(
             info, scopes=scopes, default_scopes=default_scopes
         )
     else:
         try:
             # Check if configuration corresponds to an Identity Pool credentials.
             from google.auth import identity_pool

             credentials = identity_pool.Credentials.from_info(
                 info, scopes=scopes, default_scopes=default_scopes
             )
         except ValueError:
             # If the configuration is invalid or does not correspond to any
             # supported external_account credentials, raise an error.
             raise exceptions.DefaultCredentialsError(
                 "Failed to load external account credentials from {}".format(filename)
             )
     if request is None:
         request = google.auth.transport.requests.Request()

     return credentials, credentials.get_project_id(request=request)


 def default(scopes=None, request=None, quota_project_id=None, default_scopes=None):
     """Gets the default credentials for the current environment.

     `Application Default Credentials`_ provides an easy way to obtain
     credentials to call Google APIs for server-to-server or local applications.
     This function acquires credentials from the environment in the following
     order:

     1. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
        to the path of a valid service account JSON private key file, then it is
        loaded and returned. The project ID returned is the project ID defined
        in the service account file if available (some older files do not
        contain project ID information).

        If the environment variable is set to the path of a valid external
        account JSON configuration file (workload identity federation), then the
        configuration file is used to determine and retrieve the external
        credentials from the current environment (AWS, Azure, etc).
        These will then be exchanged for Google access tokens via the Google STS
        endpoint.
        The project ID returned in this case is the one corresponding to the
        underlying workload identity pool resource if determinable.
     2. If the `Google Cloud SDK`_ is installed and has application default
        credentials set they are loaded and returned.

        To enable application default credentials with the Cloud SDK run::

             gcloud auth application-default login

        If the Cloud SDK has an active project, the project ID is returned. The
        active project can be set using::

             gcloud config set project

     3. If the application is running in the `App Engine standard environment`_
        (first generation) then the credentials and project ID from the
        `App Identity Service`_ are used.
     4. If the application is running in `Compute Engine`_ or `Cloud Run`_ or
        the `App Engine flexible environment`_ or the `App Engine standard
        environment`_ (second generation) then the credentials and project ID
        are obtained from the `Metadata Service`_.
     5. If no credentials are found,
        :class:`~google.auth.exceptions.DefaultCredentialsError` will be raised.

     .. _Application Default Credentials: https://developers.google.com\
             /identity/protocols/application-default-credentials
     .. _Google Cloud SDK: https://cloud.google.com/sdk
     .. _App Engine standard environment: https://cloud.google.com/appengine
     .. _App Identity Service: https://cloud.google.com/appengine/docs/python\
             /appidentity/
     .. _Compute Engine: https://cloud.google.com/compute
     .. _App Engine flexible environment: https://cloud.google.com\
             /appengine/flexible
     .. _Metadata Service: https://cloud.google.com/compute/docs\
             /storing-retrieving-metadata
     .. _Cloud Run: https://cloud.google.com/run

     Example::

         import google.auth

         credentials, project_id = google.auth.default()

     Args:
         scopes (Sequence[str]): The list of scopes for the credentials. If
             specified, the credentials will automatically be scoped if
             necessary.
         request (Optional[google.auth.transport.Request]): An object used to make
             HTTP requests. This is used to either detect whether the application
             is running on Compute Engine or to determine the associated project
             ID for a workload identity pool resource (external account
             credentials). If not specified, then it will either use the standard
             library http client to make requests for Compute Engine credentials
             or a google.auth.transport.requests.Request client for external
             account credentials.
         quota_project_id (Optional[str]): The project ID used for
             quota and billing.
         default_scopes (Optional[Sequence[str]]): Default scopes passed by a
             Google client library. Use 'scopes' for user-defined scopes.
     Returns:
         Tuple[~google.auth.credentials.Credentials, Optional[str]]:
             the current environment's credentials and project ID. Project ID
             may be None, which indicates that the Project ID could not be
             ascertained from the environment.

     Raises:
         ~google.auth.exceptions.DefaultCredentialsError:
             If no credentials were found, or if the credentials found were
             invalid.
     """
     from google.auth.credentials import with_scopes_if_required

     explicit_project_id = os.environ.get(
         environment_vars.PROJECT, os.environ.get(environment_vars.LEGACY_PROJECT)
     )

     checkers = (
         # Avoid passing scopes here to prevent passing scopes to user credentials.
         # with_scopes_if_required() below will ensure scopes/default scopes are
         # safely set on the returned credentials since requires_scopes will
         # guard against setting scopes on user credentials.
         lambda: _get_explicit_environ_credentials(quota_project_id=quota_project_id),
         lambda: _get_gcloud_sdk_credentials(quota_project_id=quota_project_id),
         _get_gae_credentials,
         lambda: _get_gce_credentials(request),
     )

     for checker in checkers:
         credentials, project_id = checker()
         if credentials is not None:
             credentials = with_scopes_if_required(
                 credentials, scopes, default_scopes=default_scopes
             )

             # For external account credentials, scopes are required to determine
             # the project ID. Try to get the project ID again if not yet
             # determined.
             if not project_id and callable(
                 getattr(credentials, "get_project_id", None)
             ):
                 if request is None:
                     request = google.auth.transport.requests.Request()
                 project_id = credentials.get_project_id(request=request)

             if quota_project_id:
                 credentials = credentials.with_quota_project(quota_project_id)

             effective_project_id = explicit_project_id or project_id
             if not effective_project_id:
                 _LOGGER.warning(
                     "No project ID could be determined. Consider running "
                     "`gcloud config set project` or setting the %s "
                     "environment variable",
                     environment_vars.PROJECT,
                 )
             return credentials, effective_project_id

     raise exceptions.DefaultCredentialsError(_HELP_MESSAGE)
	# Copyright 2015 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.

	"""Application default credentials.

	Implements application default credentials and project ID detection.
	"""

	import io
	import json
	import logging
	import os
	import warnings

	import six

	from google.auth import environment_vars
	from google.auth import exceptions
	import google.auth.transport._http_client

	_LOGGER = logging.getLogger(__name__)

	# Valid types accepted for file-based credentials.
	_AUTHORIZED_USER_TYPE = "authorized_user"
	_SERVICE_ACCOUNT_TYPE = "service_account"
	_EXTERNAL_ACCOUNT_TYPE = "external_account"
	_VALID_TYPES = (_AUTHORIZED_USER_TYPE, _SERVICE_ACCOUNT_TYPE, _EXTERNAL_ACCOUNT_TYPE)

	# Help message when no credentials can be found.
	_HELP_MESSAGE = """\
	Could not automatically determine credentials. Please set {env} or \
	explicitly create credentials and re-run the application. For more \
	information, please see \
	https://cloud.google.com/docs/authentication/getting-started
	""".format(
	env=environment_vars.CREDENTIALS
	).strip()

	# Warning when using Cloud SDK user credentials
	_CLOUD_SDK_CREDENTIALS_WARNING = """\
	Your application has authenticated using end user credentials from Google \
	Cloud SDK without a quota project. You might receive a "quota exceeded" \
	or "API not enabled" error. We recommend you rerun \
	`gcloud auth application-default login` and make sure a quota project is \
	added. Or you can use service accounts instead. For more information \
	about service accounts, see https://cloud.google.com/docs/authentication/"""

	# The subject token type used for AWS external_account credentials.
	_AWS_SUBJECT_TOKEN_TYPE = "urn:ietf:params:aws:token-type:aws4_request"


	def _warn_about_problematic_credentials(credentials):
	"""Determines if the credentials are problematic.

	Credentials from the Cloud SDK that are associated with Cloud SDK's project
	are problematic because they may not have APIs enabled and have limited
	quota. If this is the case, warn about it.
	"""
	from google.auth import _cloud_sdk

	if credentials.client_id == _cloud_sdk.CLOUD_SDK_CLIENT_ID:
	warnings.warn(_CLOUD_SDK_CREDENTIALS_WARNING)


	def load_credentials_from_file(
	filename, scopes=None, default_scopes=None, quota_project_id=None, request=None
	):
	"""Loads Google credentials from a file.

	The credentials file must be a service account key, stored authorized
	user credentials or external account credentials.

	Args:
	filename (str): The full path to the credentials file.
	scopes (Optional[Sequence[str]]): The list of scopes for the credentials. If
	specified, the credentials will automatically be scoped if
	necessary
	default_scopes (Optional[Sequence[str]]): Default scopes passed by a
	Google client library. Use 'scopes' for user-defined scopes.
	quota_project_id (Optional[str]): The project ID used for
	quota and billing.
	request (Optional[google.auth.transport.Request]): An object used to make
	HTTP requests. This is used to determine the associated project ID
	for a workload identity pool resource (external account credentials).
	If not specified, then it will use a
	google.auth.transport.requests.Request client to make requests.

	Returns:
	Tuple[google.auth.credentials.Credentials, Optional[str]]: Loaded
	credentials and the project ID. Authorized user credentials do not
	have the project ID information. External account credentials project
	IDs may not always be determined.

	Raises:
	google.auth.exceptions.DefaultCredentialsError: if the file is in the
	wrong format or is missing.
	"""
	if not os.path.exists(filename):
	raise exceptions.DefaultCredentialsError(
	"File {} was not found.".format(filename)
	)

	with io.open(filename, "r") as file_obj:
	try:
	info = json.load(file_obj)
	except ValueError as caught_exc:
	new_exc = exceptions.DefaultCredentialsError(
	"File {} is not a valid json file.".format(filename), caught_exc
	)
	six.raise_from(new_exc, caught_exc)

	# The type key should indicate that the file is either a service account
	# credentials file or an authorized user credentials file.
	credential_type = info.get("type")

	if credential_type == _AUTHORIZED_USER_TYPE:
	from google.oauth2 import credentials

	try:
	credentials = credentials.Credentials.from_authorized_user_info(
	info, scopes=scopes
	)
	except ValueError as caught_exc:
	msg = "Failed to load authorized user credentials from {}".format(filename)
	new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
	six.raise_from(new_exc, caught_exc)
	if quota_project_id:
	credentials = credentials.with_quota_project(quota_project_id)
	if not credentials.quota_project_id:
	_warn_about_problematic_credentials(credentials)
	return credentials, None

	elif credential_type == _SERVICE_ACCOUNT_TYPE:
	from google.oauth2 import service_account

	try:
	credentials = service_account.Credentials.from_service_account_info(
	info, scopes=scopes, default_scopes=default_scopes
	)
	except ValueError as caught_exc:
	msg = "Failed to load service account credentials from {}".format(filename)
	new_exc = exceptions.DefaultCredentialsError(msg, caught_exc)
	six.raise_from(new_exc, caught_exc)
	if quota_project_id:
	credentials = credentials.with_quota_project(quota_project_id)
	return credentials, info.get("project_id")

	elif credential_type == _EXTERNAL_ACCOUNT_TYPE:
	credentials, project_id = _get_external_account_credentials(
	info,
	filename,
	scopes=scopes,
	default_scopes=default_scopes,
	request=request,
	)
	if quota_project_id:
	credentials = credentials.with_quota_project(quota_project_id)
	return credentials, project_id

	else:
	raise exceptions.DefaultCredentialsError(
	"The file {file} does not have a valid type. "
	"Type is {type}, expected one of {valid_types}.".format(
	file=filename, type=credential_type, valid_types=_VALID_TYPES
	)
	)


	def _get_gcloud_sdk_credentials(quota_project_id=None):
	"""Gets the credentials and project ID from the Cloud SDK."""
	from google.auth import _cloud_sdk

	_LOGGER.debug("Checking Cloud SDK credentials as part of auth process...")

	# Check if application default credentials exist.
	credentials_filename = _cloud_sdk.get_application_default_credentials_path()

	if not os.path.isfile(credentials_filename):
	_LOGGER.debug("Cloud SDK credentials not found on disk; not using them")
	return None, None

	credentials, project_id = load_credentials_from_file(
	credentials_filename, quota_project_id=quota_project_id
	)

	if not project_id:
	project_id = _cloud_sdk.get_project_id()

	return credentials, project_id


	def _get_explicit_environ_credentials(quota_project_id=None):
	"""Gets credentials from the GOOGLE_APPLICATION_CREDENTIALS environment
	variable."""
	from google.auth import _cloud_sdk

	cloud_sdk_adc_path = _cloud_sdk.get_application_default_credentials_path()
	explicit_file = os.environ.get(environment_vars.CREDENTIALS)

	_LOGGER.debug(
	"Checking %s for explicit credentials as part of auth process...", explicit_file
	)

	if explicit_file is not None and explicit_file == cloud_sdk_adc_path:
	# Cloud sdk flow calls gcloud to fetch project id, so if the explicit
	# file path is cloud sdk credentials path, then we should fall back
	# to cloud sdk flow, otherwise project id cannot be obtained.
	_LOGGER.debug(
	"Explicit credentials path %s is the same as Cloud SDK credentials path, fall back to Cloud SDK credentials flow...",
	explicit_file,
	)
	return _get_gcloud_sdk_credentials(quota_project_id=quota_project_id)

	if explicit_file is not None:
	credentials, project_id = load_credentials_from_file(
	os.environ[environment_vars.CREDENTIALS], quota_project_id=quota_project_id
	)

	return credentials, project_id

	else:
	return None, None


	def _get_gae_credentials():
	"""Gets Google App Engine App Identity credentials and project ID."""
	# If not GAE gen1, prefer the metadata service even if the GAE APIs are
	# available as per https://google.aip.dev/auth/4115.
	if os.environ.get(environment_vars.LEGACY_APPENGINE_RUNTIME) != "python27":
	return None, None

	# While this library is normally bundled with app_engine, there are
	# some cases where it's not available, so we tolerate ImportError.
	try:
	_LOGGER.debug("Checking for App Engine runtime as part of auth process...")
	import google.auth.app_engine as app_engine
	except ImportError:
	_LOGGER.warning("Import of App Engine auth library failed.")
	return None, None

	try:
	credentials = app_engine.Credentials()
	project_id = app_engine.get_project_id()
	return credentials, project_id
	except EnvironmentError:
	_LOGGER.debug(
	"No App Engine library was found so cannot authentication via App Engine Identity Credentials."
	)
	return None, None


	def _get_gce_credentials(request=None):
	"""Gets credentials and project ID from the GCE Metadata Service."""
	# Ping requires a transport, but we want application default credentials
	# to require no arguments. So, we'll use the _http_client transport which
	# uses http.client. This is only acceptable because the metadata server
	# doesn't do SSL and never requires proxies.

	# While this library is normally bundled with compute_engine, there are
	# some cases where it's not available, so we tolerate ImportError.
	try:
	from google.auth import compute_engine
	from google.auth.compute_engine import _metadata
	except ImportError:
	_LOGGER.warning("Import of Compute Engine auth library failed.")
	return None, None

	if request is None:
	request = google.auth.transport._http_client.Request()

	if _metadata.ping(request=request):
	# Get the project ID.
	try:
	project_id = _metadata.get_project_id(request=request)
	except exceptions.TransportError:
	project_id = None

	return compute_engine.Credentials(), project_id
	else:
	_LOGGER.warning(
	"Authentication failed using Compute Engine authentication due to unavailable metadata server."
	)
	return None, None


	def _get_external_account_credentials(
	info, filename, scopes=None, default_scopes=None, request=None
	):
	"""Loads external account Credentials from the parsed external account info.

	The credentials information must correspond to a supported external account
	credentials.

	Args:
	info (Mapping[str, str]): The external account info in Google format.
	filename (str): The full path to the credentials file.
	scopes (Optional[Sequence[str]]): The list of scopes for the credentials. If
	specified, the credentials will automatically be scoped if
	necessary.
	default_scopes (Optional[Sequence[str]]): Default scopes passed by a
	Google client library. Use 'scopes' for user-defined scopes.
	request (Optional[google.auth.transport.Request]): An object used to make
	HTTP requests. This is used to determine the associated project ID
	for a workload identity pool resource (external account credentials).
	If not specified, then it will use a
	google.auth.transport.requests.Request client to make requests.

	Returns:
	Tuple[google.auth.credentials.Credentials, Optional[str]]: Loaded
	credentials and the project ID. External account credentials project
	IDs may not always be determined.

	Raises:
	google.auth.exceptions.DefaultCredentialsError: if the info dictionary
	is in the wrong format or is missing required information.
	"""
	# There are currently 2 types of external_account credentials.
	if info.get("subject_token_type") == _AWS_SUBJECT_TOKEN_TYPE:
	# Check if configuration corresponds to an AWS credentials.
	from google.auth import aws

	credentials = aws.Credentials.from_info(
	info, scopes=scopes, default_scopes=default_scopes
	)
	else:
	try:
	# Check if configuration corresponds to an Identity Pool credentials.
	from google.auth import identity_pool

	credentials = identity_pool.Credentials.from_info(
	info, scopes=scopes, default_scopes=default_scopes
	)
	except ValueError:
	# If the configuration is invalid or does not correspond to any
	# supported external_account credentials, raise an error.
	raise exceptions.DefaultCredentialsError(
	"Failed to load external account credentials from {}".format(filename)
	)
	if request is None:
	request = google.auth.transport.requests.Request()

	return credentials, credentials.get_project_id(request=request)


	def default(scopes=None, request=None, quota_project_id=None, default_scopes=None):
	"""Gets the default credentials for the current environment.

	`Application Default Credentials`_ provides an easy way to obtain
	credentials to call Google APIs for server-to-server or local applications.
	This function acquires credentials from the environment in the following
	order:

	1. If the environment variable ``GOOGLE_APPLICATION_CREDENTIALS`` is set
	to the path of a valid service account JSON private key file, then it is
	loaded and returned. The project ID returned is the project ID defined
	in the service account file if available (some older files do not
	contain project ID information).

	If the environment variable is set to the path of a valid external
	account JSON configuration file (workload identity federation), then the
	configuration file is used to determine and retrieve the external
	credentials from the current environment (AWS, Azure, etc).
	These will then be exchanged for Google access tokens via the Google STS
	endpoint.
	The project ID returned in this case is the one corresponding to the
	underlying workload identity pool resource if determinable.
	2. If the `Google Cloud SDK`_ is installed and has application default
	credentials set they are loaded and returned.

	To enable application default credentials with the Cloud SDK run::

	gcloud auth application-default login

	If the Cloud SDK has an active project, the project ID is returned. The
	active project can be set using::

	gcloud config set project

	3. If the application is running in the `App Engine standard environment`_
	(first generation) then the credentials and project ID from the
	`App Identity Service`_ are used.
	4. If the application is running in `Compute Engine`_ or `Cloud Run`_ or
	the `App Engine flexible environment`_ or the `App Engine standard
	environment`_ (second generation) then the credentials and project ID
	are obtained from the `Metadata Service`_.
	5. If no credentials are found,
	:class:`~google.auth.exceptions.DefaultCredentialsError` will be raised.

	.. _Application Default Credentials: https://developers.google.com\
	/identity/protocols/application-default-credentials
	.. _Google Cloud SDK: https://cloud.google.com/sdk
	.. _App Engine standard environment: https://cloud.google.com/appengine
	.. _App Identity Service: https://cloud.google.com/appengine/docs/python\
	/appidentity/
	.. _Compute Engine: https://cloud.google.com/compute
	.. _App Engine flexible environment: https://cloud.google.com\
	/appengine/flexible
	.. _Metadata Service: https://cloud.google.com/compute/docs\
	/storing-retrieving-metadata
	.. _Cloud Run: https://cloud.google.com/run

	Example::

	import google.auth

	credentials, project_id = google.auth.default()

	Args:
	scopes (Sequence[str]): The list of scopes for the credentials. If
	specified, the credentials will automatically be scoped if
	necessary.
	request (Optional[google.auth.transport.Request]): An object used to make
	HTTP requests. This is used to either detect whether the application
	is running on Compute Engine or to determine the associated project
	ID for a workload identity pool resource (external account
	credentials). If not specified, then it will either use the standard
	library http client to make requests for Compute Engine credentials
	or a google.auth.transport.requests.Request client for external
	account credentials.
	quota_project_id (Optional[str]): The project ID used for
	quota and billing.
	default_scopes (Optional[Sequence[str]]): Default scopes passed by a
	Google client library. Use 'scopes' for user-defined scopes.
	Returns:
	Tuple[~google.auth.credentials.Credentials, Optional[str]]:
	the current environment's credentials and project ID. Project ID
	may be None, which indicates that the Project ID could not be
	ascertained from the environment.

	Raises:
	~google.auth.exceptions.DefaultCredentialsError:
	If no credentials were found, or if the credentials found were
	invalid.
	"""
	from google.auth.credentials import with_scopes_if_required

	explicit_project_id = os.environ.get(
	environment_vars.PROJECT, os.environ.get(environment_vars.LEGACY_PROJECT)
	)

	checkers = (
	# Avoid passing scopes here to prevent passing scopes to user credentials.
	# with_scopes_if_required() below will ensure scopes/default scopes are
	# safely set on the returned credentials since requires_scopes will
	# guard against setting scopes on user credentials.
	lambda: _get_explicit_environ_credentials(quota_project_id=quota_project_id),
	lambda: _get_gcloud_sdk_credentials(quota_project_id=quota_project_id),
	_get_gae_credentials,
	lambda: _get_gce_credentials(request),
	)

	for checker in checkers:
	credentials, project_id = checker()
	if credentials is not None:
	credentials = with_scopes_if_required(
	credentials, scopes, default_scopes=default_scopes
	)

	# For external account credentials, scopes are required to determine
	# the project ID. Try to get the project ID again if not yet
	# determined.
	if not project_id and callable(
	getattr(credentials, "get_project_id", None)
	):
	if request is None:
	request = google.auth.transport.requests.Request()
	project_id = credentials.get_project_id(request=request)

	if quota_project_id:
	credentials = credentials.with_quota_project(quota_project_id)

	effective_project_id = explicit_project_id or project_id
	if not effective_project_id:
	_LOGGER.warning(
	"No project ID could be determined. Consider running "
	"`gcloud config set project` or setting the %s "
	"environment variable",
	environment_vars.PROJECT,
	)
	return credentials, effective_project_id

	raise exceptions.DefaultCredentialsError(_HELP_MESSAGE)