structure saas with tools

.venv/lib/python3.10/site-packages/google/auth/compute_engine/__init__.py

@@ -0,0 +1,22 @@
+# Copyright 2016 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.
+
+"""Google Compute Engine authentication."""
+
+from google.auth.compute_engine._metadata import detect_gce_residency_linux
+from google.auth.compute_engine.credentials import Credentials
+from google.auth.compute_engine.credentials import IDTokenCredentials
+
+
+__all__ = ["Credentials", "IDTokenCredentials", "detect_gce_residency_linux"]

.venv/lib/python3.10/site-packages/google/auth/compute_engine/_metadata.py

@@ -0,0 +1,379 @@
+# Copyright 2016 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.
+
+"""Provides helper methods for talking to the Compute Engine metadata server.
+
+See https://cloud.google.com/compute/docs/metadata for more details.
+"""
+
+import datetime
+import http.client as http_client
+import json
+import logging
+import os
+from urllib.parse import urljoin
+
+from google.auth import _helpers
+from google.auth import environment_vars
+from google.auth import exceptions
+from google.auth import metrics
+from google.auth import transport
+from google.auth._exponential_backoff import ExponentialBackoff
+
+_LOGGER = logging.getLogger(__name__)
+
+# Environment variable GCE_METADATA_HOST is originally named
+# GCE_METADATA_ROOT. For compatibility reasons, here it checks
+# the new variable first; if not set, the system falls back
+# to the old variable.
+_GCE_METADATA_HOST = os.getenv(environment_vars.GCE_METADATA_HOST, None)
+if not _GCE_METADATA_HOST:
+    _GCE_METADATA_HOST = os.getenv(
+        environment_vars.GCE_METADATA_ROOT, "metadata.google.internal"
+    )
+_METADATA_ROOT = "http://{}/computeMetadata/v1/".format(_GCE_METADATA_HOST)
+
+# This is used to ping the metadata server, it avoids the cost of a DNS
+# lookup.
+_METADATA_IP_ROOT = "http://{}".format(
+    os.getenv(environment_vars.GCE_METADATA_IP, "169.254.169.254")
+)
+_METADATA_FLAVOR_HEADER = "metadata-flavor"
+_METADATA_FLAVOR_VALUE = "Google"
+_METADATA_HEADERS = {_METADATA_FLAVOR_HEADER: _METADATA_FLAVOR_VALUE}
+
+# Timeout in seconds to wait for the GCE metadata server when detecting the
+# GCE environment.
+try:
+    _METADATA_DEFAULT_TIMEOUT = int(os.getenv("GCE_METADATA_TIMEOUT", 3))
+except ValueError:  # pragma: NO COVER
+    _METADATA_DEFAULT_TIMEOUT = 3
+
+# Detect GCE Residency
+_GOOGLE = "Google"
+_GCE_PRODUCT_NAME_FILE = "/sys/class/dmi/id/product_name"
+
+
+def is_on_gce(request):
+    """Checks to see if the code runs on Google Compute Engine
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+
+    Returns:
+        bool: True if the code runs on Google Compute Engine, False otherwise.
+    """
+    if ping(request):
+        return True
+
+    if os.name == "nt":
+        # TODO: implement GCE residency detection on Windows
+        return False
+
+    # Detect GCE residency on Linux
+    return detect_gce_residency_linux()
+
+
+def detect_gce_residency_linux():
+    """Detect Google Compute Engine residency by smbios check on Linux
+
+    Returns:
+        bool: True if the GCE product name file is detected, False otherwise.
+    """
+    try:
+        with open(_GCE_PRODUCT_NAME_FILE, "r") as file_obj:
+            content = file_obj.read().strip()
+
+    except Exception:
+        return False
+
+    return content.startswith(_GOOGLE)
+
+
+def ping(request, timeout=_METADATA_DEFAULT_TIMEOUT, retry_count=3):
+    """Checks to see if the metadata server is available.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        timeout (int): How long to wait for the metadata server to respond.
+        retry_count (int): How many times to attempt connecting to metadata
+            server using above timeout.
+
+    Returns:
+        bool: True if the metadata server is reachable, False otherwise.
+    """
+    # NOTE: The explicit ``timeout`` is a workaround. The underlying
+    #       issue is that resolving an unknown host on some networks will take
+    #       20-30 seconds; making this timeout short fixes the issue, but
+    #       could lead to false negatives in the event that we are on GCE, but
+    #       the metadata resolution was particularly slow. The latter case is
+    #       "unlikely".
+    headers = _METADATA_HEADERS.copy()
+    headers[metrics.API_CLIENT_HEADER] = metrics.mds_ping()
+
+    backoff = ExponentialBackoff(total_attempts=retry_count)
+
+    for attempt in backoff:
+        try:
+            response = request(
+                url=_METADATA_IP_ROOT, method="GET", headers=headers, timeout=timeout
+            )
+
+            metadata_flavor = response.headers.get(_METADATA_FLAVOR_HEADER)
+            return (
+                response.status == http_client.OK
+                and metadata_flavor == _METADATA_FLAVOR_VALUE
+            )
+
+        except exceptions.TransportError as e:
+            _LOGGER.warning(
+                "Compute Engine Metadata server unavailable on "
+                "attempt %s of %s. Reason: %s",
+                attempt,
+                retry_count,
+                e,
+            )
+
+    return False
+
+
+def get(
+    request,
+    path,
+    root=_METADATA_ROOT,
+    params=None,
+    recursive=False,
+    retry_count=5,
+    headers=None,
+    return_none_for_not_found_error=False,
+    timeout=_METADATA_DEFAULT_TIMEOUT,
+):
+    """Fetch a resource from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        path (str): The resource to retrieve. For example,
+            ``'instance/service-accounts/default'``.
+        root (str): The full path to the metadata server root.
+        params (Optional[Mapping[str, str]]): A mapping of query parameter
+            keys to values.
+        recursive (bool): Whether to do a recursive query of metadata. See
+            https://cloud.google.com/compute/docs/metadata#aggcontents for more
+            details.
+        retry_count (int): How many times to attempt connecting to metadata
+            server using above timeout.
+        headers (Optional[Mapping[str, str]]): Headers for the request.
+        return_none_for_not_found_error (Optional[bool]): If True, returns None
+            for 404 error instead of throwing an exception.
+        timeout (int): How long to wait, in seconds for the metadata server to respond.
+
+    Returns:
+        Union[Mapping, str]: If the metadata server returns JSON, a mapping of
+            the decoded JSON is returned. Otherwise, the response content is
+            returned as a string.
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    base_url = urljoin(root, path)
+    query_params = {} if params is None else params
+
+    headers_to_use = _METADATA_HEADERS.copy()
+    if headers:
+        headers_to_use.update(headers)
+
+    if recursive:
+        query_params["recursive"] = "true"
+
+    url = _helpers.update_query(base_url, query_params)
+
+    backoff = ExponentialBackoff(total_attempts=retry_count)
+    failure_reason = None
+    for attempt in backoff:
+        try:
+            response = request(
+                url=url, method="GET", headers=headers_to_use, timeout=timeout
+            )
+            if response.status in transport.DEFAULT_RETRYABLE_STATUS_CODES:
+                _LOGGER.warning(
+                    "Compute Engine Metadata server unavailable on "
+                    "attempt %s of %s. Response status: %s",
+                    attempt,
+                    retry_count,
+                    response.status,
+                )
+                failure_reason = (
+                    response.data.decode("utf-8")
+                    if hasattr(response.data, "decode")
+                    else response.data
+                )
+                continue
+            else:
+                break
+
+        except exceptions.TransportError as e:
+            _LOGGER.warning(
+                "Compute Engine Metadata server unavailable on "
+                "attempt %s of %s. Reason: %s",
+                attempt,
+                retry_count,
+                e,
+            )
+            failure_reason = e
+    else:
+        raise exceptions.TransportError(
+            "Failed to retrieve {} from the Google Compute Engine "
+            "metadata service. Compute Engine Metadata server unavailable due to {}".format(
+                url, failure_reason
+            )
+        )
+
+    content = _helpers.from_bytes(response.data)
+
+    if response.status == http_client.NOT_FOUND and return_none_for_not_found_error:
+        return None
+
+    if response.status == http_client.OK:
+        if (
+            _helpers.parse_content_type(response.headers["content-type"])
+            == "application/json"
+        ):
+            try:
+                return json.loads(content)
+            except ValueError as caught_exc:
+                new_exc = exceptions.TransportError(
+                    "Received invalid JSON from the Google Compute Engine "
+                    "metadata service: {:.20}".format(content)
+                )
+                raise new_exc from caught_exc
+        else:
+            return content
+
+    raise exceptions.TransportError(
+        "Failed to retrieve {} from the Google Compute Engine "
+        "metadata service. Status: {} Response:\n{}".format(
+            url, response.status, response.data
+        ),
+        response,
+    )
+
+
+def get_project_id(request):
+    """Get the Google Cloud Project ID from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+
+    Returns:
+        str: The project ID
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    return get(request, "project/project-id")
+
+
+def get_universe_domain(request):
+    """Get the universe domain value from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+
+    Returns:
+        str: The universe domain value. If the universe domain endpoint is not
+        not found, return the default value, which is googleapis.com
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error other than
+            404 occurs while retrieving metadata.
+    """
+    universe_domain = get(
+        request, "universe/universe-domain", return_none_for_not_found_error=True
+    )
+    if not universe_domain:
+        return "googleapis.com"
+    return universe_domain
+
+
+def get_service_account_info(request, service_account="default"):
+    """Get information about a service account from the metadata server.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        service_account (str): The string 'default' or a service account email
+            address. The determines which service account for which to acquire
+            information.
+
+    Returns:
+        Mapping: The service account's information, for example::
+
+            {
+                'email': '...',
+                'scopes': ['scope', ...],
+                'aliases': ['default', '...']
+            }
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    path = "instance/service-accounts/{0}/".format(service_account)
+    # See https://cloud.google.com/compute/docs/metadata#aggcontents
+    # for more on the use of 'recursive'.
+    return get(request, path, params={"recursive": "true"})
+
+
+def get_service_account_token(request, service_account="default", scopes=None):
+    """Get the OAuth 2.0 access token for a service account.
+
+    Args:
+        request (google.auth.transport.Request): A callable used to make
+            HTTP requests.
+        service_account (str): The string 'default' or a service account email
+            address. The determines which service account for which to acquire
+            an access token.
+        scopes (Optional[Union[str, List[str]]]): Optional string or list of
+            strings with auth scopes.
+    Returns:
+        Tuple[str, datetime]: The access token and its expiration.
+
+    Raises:
+        google.auth.exceptions.TransportError: if an error occurred while
+            retrieving metadata.
+    """
+    if scopes:
+        if not isinstance(scopes, str):
+            scopes = ",".join(scopes)
+        params = {"scopes": scopes}
+    else:
+        params = None
+
+    metrics_header = {
+        metrics.API_CLIENT_HEADER: metrics.token_request_access_token_mds()
+    }
+
+    path = "instance/service-accounts/{0}/token".format(service_account)
+    token_json = get(request, path, params=params, headers=metrics_header)
+    token_expiry = _helpers.utcnow() + datetime.timedelta(
+        seconds=token_json["expires_in"]
+    )
+    return token_json["access_token"], token_expiry

.venv/lib/python3.10/site-packages/google/auth/compute_engine/credentials.py

@@ -0,0 +1,496 @@
+# Copyright 2016 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.
+
+"""Google Compute Engine credentials.
+
+This module provides authentication for an application running on Google
+Compute Engine using the Compute Engine metadata server.
+
+"""
+
+import datetime
+
+from google.auth import _helpers
+from google.auth import credentials
+from google.auth import exceptions
+from google.auth import iam
+from google.auth import jwt
+from google.auth import metrics
+from google.auth.compute_engine import _metadata
+from google.oauth2 import _client
+
+
+class Credentials(
+    credentials.Scoped,
+    credentials.CredentialsWithQuotaProject,
+    credentials.CredentialsWithUniverseDomain,
+):
+    """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,
+    and are also used for Cloud Run, Flex and App Engine (except for the Python
+    2.7 runtime, which is supported only on older versions of this library).
+
+    For more information about Compute Engine authentication, including how
+    to configure scopes, see the `Compute Engine authentication
+    documentation`_.
+
+    .. note:: On Compute Engine the metadata server ignores requested scopes.
+        On Cloud Run, Flex and App Engine the server honours requested scopes.
+
+    .. _Compute Engine authentication documentation:
+        https://cloud.google.com/compute/docs/authentication#using
+    """
+
+    def __init__(
+        self,
+        service_account_email="default",
+        quota_project_id=None,
+        scopes=None,
+        default_scopes=None,
+        universe_domain=None,
+    ):
+        """
+        Args:
+            service_account_email (str): The service account email to use, or
+                'default'. A Compute Engine instance may have multiple service
+                accounts.
+            quota_project_id (Optional[str]): The project ID used for quota and
+                billing.
+            scopes (Optional[Sequence[str]]): The list of scopes for the credentials.
+            default_scopes (Optional[Sequence[str]]): Default scopes passed by a
+                Google client library. Use 'scopes' for user-defined scopes.
+            universe_domain (Optional[str]): The universe domain. If not
+                provided or None, credential will attempt to fetch the value
+                from metadata server. If metadata server doesn't have universe
+                domain endpoint, then the default googleapis.com will be used.
+        """
+        super(Credentials, self).__init__()
+        self._service_account_email = service_account_email
+        self._quota_project_id = quota_project_id
+        self._scopes = scopes
+        self._default_scopes = default_scopes
+        self._universe_domain_cached = False
+        if universe_domain:
+            self._universe_domain = universe_domain
+            self._universe_domain_cached = True
+
+    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"]
+
+        # Don't override scopes requested by the user.
+        if self._scopes is None:
+            self._scopes = info["scopes"]
+
+    def _metric_header_for_usage(self):
+        return metrics.CRED_TYPE_SA_MDS
+
+    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.
+        """
+        scopes = self._scopes if self._scopes is not None else self._default_scopes
+        try:
+            self._retrieve_info(request)
+            self.token, self.expiry = _metadata.get_service_account_token(
+                request, service_account=self._service_account_email, scopes=scopes
+            )
+        except exceptions.TransportError as caught_exc:
+            new_exc = exceptions.RefreshError(caught_exc)
+            raise new_exc from caught_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):
+        return not self._scopes
+
+    @property
+    def universe_domain(self):
+        if self._universe_domain_cached:
+            return self._universe_domain
+
+        from google.auth.transport import requests as google_auth_requests
+
+        self._universe_domain = _metadata.get_universe_domain(
+            google_auth_requests.Request()
+        )
+        self._universe_domain_cached = True
+        return self._universe_domain
+
+    @_helpers.copy_docstring(credentials.Credentials)
+    def get_cred_info(self):
+        return {
+            "credential_source": "metadata server",
+            "credential_type": "VM credentials",
+            "principal": self.service_account_email,
+        }
+
+    @_helpers.copy_docstring(credentials.CredentialsWithQuotaProject)
+    def with_quota_project(self, quota_project_id):
+        creds = self.__class__(
+            service_account_email=self._service_account_email,
+            quota_project_id=quota_project_id,
+            scopes=self._scopes,
+            default_scopes=self._default_scopes,
+        )
+        creds._universe_domain = self._universe_domain
+        creds._universe_domain_cached = self._universe_domain_cached
+        return creds
+
+    @_helpers.copy_docstring(credentials.Scoped)
+    def with_scopes(self, scopes, default_scopes=None):
+        # Compute Engine credentials can not be scoped (the metadata service
+        # ignores the scopes parameter). App Engine, Cloud Run and Flex support
+        # requesting scopes.
+        creds = self.__class__(
+            scopes=scopes,
+            default_scopes=default_scopes,
+            service_account_email=self._service_account_email,
+            quota_project_id=self._quota_project_id,
+        )
+        creds._universe_domain = self._universe_domain
+        creds._universe_domain_cached = self._universe_domain_cached
+        return creds
+
+    @_helpers.copy_docstring(credentials.CredentialsWithUniverseDomain)
+    def with_universe_domain(self, universe_domain):
+        return self.__class__(
+            scopes=self._scopes,
+            default_scopes=self._default_scopes,
+            service_account_email=self._service_account_email,
+            quota_project_id=self._quota_project_id,
+            universe_domain=universe_domain,
+        )
+
+
+_DEFAULT_TOKEN_LIFETIME_SECS = 3600  # 1 hour in seconds
+_DEFAULT_TOKEN_URI = "https://www.googleapis.com/oauth2/v4/token"
+
+
+class IDTokenCredentials(
+    credentials.CredentialsWithQuotaProject,
+    credentials.Signing,
+    credentials.CredentialsWithTokenUri,
+):
+    """Open ID Connect ID Token-based service account credentials.
+
+    These credentials relies on the default service account of a GCE instance.
+
+    ID token can be requested from `GCE metadata server identity endpoint`_, IAM
+    token endpoint or other token endpoints you specify. If metadata server
+    identity endpoint is not used, the GCE instance must have been started with
+    a service account that has access to the IAM Cloud API.
+
+    .. _GCE metadata server identity endpoint:
+        https://cloud.google.com/compute/docs/instances/verifying-instance-identity
+    """
+
+    def __init__(
+        self,
+        request,
+        target_audience,
+        token_uri=None,
+        additional_claims=None,
+        service_account_email=None,
+        signer=None,
+        use_metadata_identity_endpoint=False,
+        quota_project_id=None,
+    ):
+        """
+        Args:
+            request (google.auth.transport.Request): The object used to make
+                HTTP requests.
+            target_audience (str): The intended audience for these credentials,
+                used when requesting the ID Token. The ID Token's ``aud`` claim
+                will be set to this string.
+            token_uri (str): The OAuth 2.0 Token URI.
+            additional_claims (Mapping[str, str]): Any additional claims for
+                the JWT assertion used in the authorization grant.
+            service_account_email (str): Optional explicit service account to
+                use to sign JWT tokens.
+                By default, this is the default GCE service account.
+            signer (google.auth.crypt.Signer): The signer used to sign JWTs.
+                In case the signer is specified, the request argument will be
+                ignored.
+            use_metadata_identity_endpoint (bool): Whether to use GCE metadata
+                identity endpoint. For backward compatibility the default value
+                is False. If set to True, ``token_uri``, ``additional_claims``,
+                ``service_account_email``, ``signer`` argument should not be set;
+                otherwise ValueError will be raised.
+            quota_project_id (Optional[str]): The project ID used for quota and
+                billing.
+
+        Raises:
+            ValueError:
+                If ``use_metadata_identity_endpoint`` is set to True, and one of
+                ``token_uri``, ``additional_claims``, ``service_account_email``,
+                 ``signer`` arguments is set.
+        """
+        super(IDTokenCredentials, self).__init__()
+
+        self._quota_project_id = quota_project_id
+        self._use_metadata_identity_endpoint = use_metadata_identity_endpoint
+        self._target_audience = target_audience
+
+        if use_metadata_identity_endpoint:
+            if token_uri or additional_claims or service_account_email or signer:
+                raise exceptions.MalformedError(
+                    "If use_metadata_identity_endpoint is set, token_uri, "
+                    "additional_claims, service_account_email, signer arguments"
+                    " must not be set"
+                )
+            self._token_uri = None
+            self._additional_claims = None
+            self._signer = None
+
+        if service_account_email is None:
+            sa_info = _metadata.get_service_account_info(request)
+            self._service_account_email = sa_info["email"]
+        else:
+            self._service_account_email = service_account_email
+
+        if not use_metadata_identity_endpoint:
+            if signer is None:
+                signer = iam.Signer(
+                    request=request,
+                    credentials=Credentials(),
+                    service_account_email=self._service_account_email,
+                )
+            self._signer = signer
+            self._token_uri = token_uri or _DEFAULT_TOKEN_URI
+
+            if additional_claims is not None:
+                self._additional_claims = additional_claims
+            else:
+                self._additional_claims = {}
+
+    def with_target_audience(self, target_audience):
+        """Create a copy of these credentials with the specified target
+        audience.
+        Args:
+            target_audience (str): The intended audience for these credentials,
+            used when requesting the ID Token.
+        Returns:
+            google.auth.service_account.IDTokenCredentials: A new credentials
+                instance.
+        """
+        # since the signer is already instantiated,
+        # the request is not needed
+        if self._use_metadata_identity_endpoint:
+            return self.__class__(
+                None,
+                target_audience=target_audience,
+                use_metadata_identity_endpoint=True,
+                quota_project_id=self._quota_project_id,
+            )
+        else:
+            return self.__class__(
+                None,
+                service_account_email=self._service_account_email,
+                token_uri=self._token_uri,
+                target_audience=target_audience,
+                additional_claims=self._additional_claims.copy(),
+                signer=self.signer,
+                use_metadata_identity_endpoint=False,
+                quota_project_id=self._quota_project_id,
+            )
+
+    @_helpers.copy_docstring(credentials.CredentialsWithQuotaProject)
+    def with_quota_project(self, quota_project_id):
+
+        # since the signer is already instantiated,
+        # the request is not needed
+        if self._use_metadata_identity_endpoint:
+            return self.__class__(
+                None,
+                target_audience=self._target_audience,
+                use_metadata_identity_endpoint=True,
+                quota_project_id=quota_project_id,
+            )
+        else:
+            return self.__class__(
+                None,
+                service_account_email=self._service_account_email,
+                token_uri=self._token_uri,
+                target_audience=self._target_audience,
+                additional_claims=self._additional_claims.copy(),
+                signer=self.signer,
+                use_metadata_identity_endpoint=False,
+                quota_project_id=quota_project_id,
+            )
+
+    @_helpers.copy_docstring(credentials.CredentialsWithTokenUri)
+    def with_token_uri(self, token_uri):
+
+        # since the signer is already instantiated,
+        # the request is not needed
+        if self._use_metadata_identity_endpoint:
+            raise exceptions.MalformedError(
+                "If use_metadata_identity_endpoint is set, token_uri" " must not be set"
+            )
+        else:
+            return self.__class__(
+                None,
+                service_account_email=self._service_account_email,
+                token_uri=token_uri,
+                target_audience=self._target_audience,
+                additional_claims=self._additional_claims.copy(),
+                signer=self.signer,
+                use_metadata_identity_endpoint=False,
+                quota_project_id=self.quota_project_id,
+            )
+
+    def _make_authorization_grant_assertion(self):
+        """Create the OAuth 2.0 assertion.
+        This assertion is used during the OAuth 2.0 grant to acquire an
+        ID token.
+        Returns:
+            bytes: The authorization grant assertion.
+        """
+        now = _helpers.utcnow()
+        lifetime = datetime.timedelta(seconds=_DEFAULT_TOKEN_LIFETIME_SECS)
+        expiry = now + lifetime
+
+        payload = {
+            "iat": _helpers.datetime_to_secs(now),
+            "exp": _helpers.datetime_to_secs(expiry),
+            # The issuer must be the service account email.
+            "iss": self.service_account_email,
+            # The audience must be the auth token endpoint's URI
+            "aud": self._token_uri,
+            # The target audience specifies which service the ID token is
+            # intended for.
+            "target_audience": self._target_audience,
+        }
+
+        payload.update(self._additional_claims)
+
+        token = jwt.encode(self._signer, payload)
+
+        return token
+
+    def _call_metadata_identity_endpoint(self, request):
+        """Request ID token from metadata identity endpoint.
+
+        Args:
+            request (google.auth.transport.Request): The object used to make
+                HTTP requests.
+
+        Returns:
+            Tuple[str, datetime.datetime]: The ID token and the expiry of the ID token.
+
+        Raises:
+            google.auth.exceptions.RefreshError: If the Compute Engine metadata
+                service can't be reached or if the instance has no credentials.
+            ValueError: If extracting expiry from the obtained ID token fails.
+        """
+        try:
+            path = "instance/service-accounts/default/identity"
+            params = {"audience": self._target_audience, "format": "full"}
+            metrics_header = {
+                metrics.API_CLIENT_HEADER: metrics.token_request_id_token_mds()
+            }
+            id_token = _metadata.get(
+                request, path, params=params, headers=metrics_header
+            )
+        except exceptions.TransportError as caught_exc:
+            new_exc = exceptions.RefreshError(caught_exc)
+            raise new_exc from caught_exc
+
+        _, payload, _, _ = jwt._unverified_decode(id_token)
+        return id_token, datetime.datetime.utcfromtimestamp(payload["exp"])
+
+    def refresh(self, request):
+        """Refreshes the ID token.
+
+        Args:
+            request (google.auth.transport.Request): The object used to make
+                HTTP requests.
+
+        Raises:
+            google.auth.exceptions.RefreshError: If the credentials could
+                not be refreshed.
+            ValueError: If extracting expiry from the obtained ID token fails.
+        """
+        if self._use_metadata_identity_endpoint:
+            self.token, self.expiry = self._call_metadata_identity_endpoint(request)
+        else:
+            assertion = self._make_authorization_grant_assertion()
+            access_token, expiry, _ = _client.id_token_jwt_grant(
+                request, self._token_uri, assertion
+            )
+            self.token = access_token
+            self.expiry = expiry
+
+    @property  # type: ignore
+    @_helpers.copy_docstring(credentials.Signing)
+    def signer(self):
+        return self._signer
+
+    def sign_bytes(self, message):
+        """Signs the given message.
+
+        Args:
+            message (bytes): The message to sign.
+
+        Returns:
+            bytes: The message's cryptographic signature.
+
+        Raises:
+            ValueError:
+                Signer is not available if metadata identity endpoint is used.
+        """
+        if self._use_metadata_identity_endpoint:
+            raise exceptions.InvalidOperation(
+                "Signer is not available if metadata identity endpoint is used"
+            )
+        return self._signer.sign(message)
+
+    @property
+    def service_account_email(self):
+        """The service account email."""
+        return self._service_account_email
+
+    @property
+    def signer_email(self):
+        return self._service_account_email