Source code for google.auth.transport.grpc

# 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
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# See the License for the specific language governing permissions and
# limitations under the License.

"""Authorization support for gRPC."""

from __future__ import absolute_import

import logging
import os

from google.auth import environment_vars
from google.auth import exceptions
from google.auth.transport import _mtls_helper
from google.oauth2 import service_account

    import grpc  # type: ignore
except ImportError as caught_exc:  # pragma: NO COVER
    raise ImportError(
        "gRPC is not installed from please install the grpcio package to use the gRPC transport."
    ) from caught_exc

_LOGGER = logging.getLogger(__name__)

[docs] class AuthMetadataPlugin(grpc.AuthMetadataPlugin): """A `gRPC AuthMetadataPlugin`_ that inserts the credentials into each request. .. _gRPC AuthMetadataPlugin: Args: credentials (google.auth.credentials.Credentials): The credentials to add to requests. request (google.auth.transport.Request): A HTTP transport request object used to refresh credentials as needed. default_host (Optional[str]): A host like "". This is used when a self-signed JWT is created from service account credentials. """ def __init__(self, credentials, request, default_host=None): # pylint: disable=no-value-for-parameter # pylint doesn't realize that the super method takes no arguments # because this class is the same name as the superclass. super(AuthMetadataPlugin, self).__init__() self._credentials = credentials self._request = request self._default_host = default_host def _get_authorization_headers(self, context): """Gets the authorization headers for a request. Returns: Sequence[Tuple[str, str]]: A list of request headers (key, value) to add to the request. """ headers = {} # # Attempt to use self-signed JWTs when a service account is used. # A default host must be explicitly provided since it cannot always # be determined from the context.service_url. if isinstance(self._credentials, service_account.Credentials): self._credentials._create_self_signed_jwt( "https://{}/".format(self._default_host) if self._default_host else None ) self._credentials.before_request( self._request, context.method_name, context.service_url, headers ) return list(headers.items()) def __call__(self, context, callback): """Passes authorization metadata into the given callback. Args: context (grpc.AuthMetadataContext): The RPC context. callback (grpc.AuthMetadataPluginCallback): The callback that will be invoked to pass in the authorization metadata. """ callback(self._get_authorization_headers(context), None)
[docs] def secure_authorized_channel( credentials, request, target, ssl_credentials=None, client_cert_callback=None, **kwargs ): """Creates a secure authorized gRPC channel. This creates a channel with SSL and :class:`AuthMetadataPlugin`. This channel can be used to create a stub that can make authorized requests. Users can configure client certificate or rely on device certificates to establish a mutual TLS channel, if the `GOOGLE_API_USE_CLIENT_CERTIFICATE` variable is explicitly set to `true`. Example:: import google.auth import google.auth.transport.grpc import google.auth.transport.requests from import cloud_speech_pb2 # Get credentials. credentials, _ = google.auth.default() # Get an HTTP request function to refresh credentials. request = google.auth.transport.requests.Request() # Create a channel. channel = google.auth.transport.grpc.secure_authorized_channel( credentials, regular_endpoint, request, ssl_credentials=grpc.ssl_channel_credentials()) # Use the channel to create a stub. cloud_speech.create_Speech_stub(channel) Usage: There are actually a couple of options to create a channel, depending on if you want to create a regular or mutual TLS channel. First let's list the endpoints (regular vs mutual TLS) to choose from:: regular_endpoint = '' mtls_endpoint = '' Option 1: create a regular (non-mutual) TLS channel by explicitly setting the ssl_credentials:: regular_ssl_credentials = grpc.ssl_channel_credentials() channel = google.auth.transport.grpc.secure_authorized_channel( credentials, regular_endpoint, request, ssl_credentials=regular_ssl_credentials) Option 2: create a mutual TLS channel by calling a callback which returns the client side certificate and the key (Note that `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly set to `true`):: def my_client_cert_callback(): code_to_load_client_cert_and_key() if loaded: return (pem_cert_bytes, pem_key_bytes) raise MyClientCertFailureException() try: channel = google.auth.transport.grpc.secure_authorized_channel( credentials, mtls_endpoint, request, client_cert_callback=my_client_cert_callback) except MyClientCertFailureException: # handle the exception Option 3: use application default SSL credentials. It searches and uses the command in a context aware metadata file, which is available on devices with endpoint verification support (Note that `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly set to `true`). See try: default_ssl_credentials = SslCredentials() except: # Exception can be raised if the context aware metadata is malformed. # See :class:`SslCredentials` for the possible exceptions. # Choose the endpoint based on the SSL credentials type. if default_ssl_credentials.is_mtls: endpoint_to_use = mtls_endpoint else: endpoint_to_use = regular_endpoint channel = google.auth.transport.grpc.secure_authorized_channel( credentials, endpoint_to_use, request, ssl_credentials=default_ssl_credentials) Option 4: not setting ssl_credentials and client_cert_callback. For devices without endpoint verification support or `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is not `true`, a regular TLS channel is created; otherwise, a mutual TLS channel is created, however, the call should be wrapped in a try/except block in case of malformed context aware metadata. The following code uses regular_endpoint, it works the same no matter the created channle is regular or mutual TLS. Regular endpoint ignores client certificate and key:: channel = google.auth.transport.grpc.secure_authorized_channel( credentials, regular_endpoint, request) The following code uses mtls_endpoint, if the created channle is regular, and API mtls_endpoint is confgured to require client SSL credentials, API calls using this channel will be rejected:: channel = google.auth.transport.grpc.secure_authorized_channel( credentials, mtls_endpoint, request) Args: credentials (google.auth.credentials.Credentials): The credentials to add to requests. request (google.auth.transport.Request): A HTTP transport request object used to refresh credentials as needed. Even though gRPC is a separate transport, there's no way to refresh the credentials without using a standard http transport. target (str): The host and port of the service. ssl_credentials (grpc.ChannelCredentials): Optional SSL channel credentials. This can be used to specify different certificates. This argument is mutually exclusive with client_cert_callback; providing both will raise an exception. If ssl_credentials and client_cert_callback are None, application default SSL credentials are used if `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is explicitly set to `true`, otherwise one way TLS SSL credentials are used. client_cert_callback (Callable[[], (bytes, bytes)]): Optional callback function to obtain client certicate and key for mutual TLS connection. This argument is mutually exclusive with ssl_credentials; providing both will raise an exception. This argument does nothing unless `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is explicitly set to `true`. kwargs: Additional arguments to pass to :func:`grpc.secure_channel`. Returns: grpc.Channel: The created gRPC channel. Raises: google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel creation failed for any reason. """ # Create the metadata plugin for inserting the authorization header. metadata_plugin = AuthMetadataPlugin(credentials, request) # Create a set of grpc.CallCredentials using the metadata plugin. google_auth_credentials = grpc.metadata_call_credentials(metadata_plugin) if ssl_credentials and client_cert_callback: raise exceptions.MalformedError( "Received both ssl_credentials and client_cert_callback; " "these are mutually exclusive." ) # If SSL credentials are not explicitly set, try client_cert_callback and ADC. if not ssl_credentials: use_client_cert = os.getenv( environment_vars.GOOGLE_API_USE_CLIENT_CERTIFICATE, "false" ) if use_client_cert == "true" and client_cert_callback: # Use the callback if provided. cert, key = client_cert_callback() ssl_credentials = grpc.ssl_channel_credentials( certificate_chain=cert, private_key=key ) elif use_client_cert == "true": # Use application default SSL credentials. adc_ssl_credentils = SslCredentials() ssl_credentials = adc_ssl_credentils.ssl_credentials else: ssl_credentials = grpc.ssl_channel_credentials() # Combine the ssl credentials and the authorization credentials. composite_credentials = grpc.composite_channel_credentials( ssl_credentials, google_auth_credentials ) return grpc.secure_channel(target, composite_credentials, **kwargs)
[docs] class SslCredentials: """Class for application default SSL credentials. The behavior is controlled by `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable whose default value is `false`. Client certificate will not be used unless the environment variable is explicitly set to `true`. See If the environment variable is `true`, then for devices with endpoint verification support, a device certificate will be automatically loaded and mutual TLS will be established. See """ def __init__(self): use_client_cert = os.getenv( environment_vars.GOOGLE_API_USE_CLIENT_CERTIFICATE, "false" ) if use_client_cert != "true": self._is_mtls = False else: # Load client SSL credentials. metadata_path = _mtls_helper._check_dca_metadata_path( _mtls_helper.CONTEXT_AWARE_METADATA_PATH ) self._is_mtls = metadata_path is not None @property def ssl_credentials(self): """Get the created SSL channel credentials. For devices with endpoint verification support, if the device certificate loading has any problems, corresponding exceptions will be raised. For a device without endpoint verification support, no exceptions will be raised. Returns: grpc.ChannelCredentials: The created grpc channel credentials. Raises: google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel creation failed for any reason. """ if self._is_mtls: try: _, cert, key, _ = _mtls_helper.get_client_ssl_credentials() self._ssl_credentials = grpc.ssl_channel_credentials( certificate_chain=cert, private_key=key ) except exceptions.ClientCertError as caught_exc: new_exc = exceptions.MutualTLSChannelError(caught_exc) raise new_exc from caught_exc else: self._ssl_credentials = grpc.ssl_channel_credentials() return self._ssl_credentials @property def is_mtls(self): """Indicates if the created SSL channel credentials is mutual TLS.""" return self._is_mtls