335 lines
13 KiB
Python
335 lines
13 KiB
Python
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# Copyright 2016 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Authorization support for gRPC."""
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from __future__ import absolute_import
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import logging
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import os
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import six
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from google.auth import environment_vars
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from google.auth import exceptions
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from google.auth.transport import _mtls_helper
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try:
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import grpc
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except ImportError as caught_exc: # pragma: NO COVER
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six.raise_from(
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ImportError(
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"gRPC is not installed, please install the grpcio package "
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"to use the gRPC transport."
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),
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caught_exc,
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)
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_LOGGER = logging.getLogger(__name__)
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class AuthMetadataPlugin(grpc.AuthMetadataPlugin):
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"""A `gRPC AuthMetadataPlugin`_ that inserts the credentials into each
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request.
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.. _gRPC AuthMetadataPlugin:
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http://www.grpc.io/grpc/python/grpc.html#grpc.AuthMetadataPlugin
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Args:
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credentials (google.auth.credentials.Credentials): The credentials to
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add to requests.
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request (google.auth.transport.Request): A HTTP transport request
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object used to refresh credentials as needed.
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"""
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def __init__(self, credentials, request):
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# pylint: disable=no-value-for-parameter
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# pylint doesn't realize that the super method takes no arguments
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# because this class is the same name as the superclass.
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super(AuthMetadataPlugin, self).__init__()
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self._credentials = credentials
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self._request = request
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def _get_authorization_headers(self, context):
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"""Gets the authorization headers for a request.
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Returns:
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Sequence[Tuple[str, str]]: A list of request headers (key, value)
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to add to the request.
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"""
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headers = {}
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self._credentials.before_request(
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self._request, context.method_name, context.service_url, headers
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)
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return list(six.iteritems(headers))
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def __call__(self, context, callback):
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"""Passes authorization metadata into the given callback.
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Args:
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context (grpc.AuthMetadataContext): The RPC context.
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callback (grpc.AuthMetadataPluginCallback): The callback that will
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be invoked to pass in the authorization metadata.
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"""
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callback(self._get_authorization_headers(context), None)
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def secure_authorized_channel(
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credentials,
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request,
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target,
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ssl_credentials=None,
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client_cert_callback=None,
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**kwargs
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):
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"""Creates a secure authorized gRPC channel.
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This creates a channel with SSL and :class:`AuthMetadataPlugin`. This
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channel can be used to create a stub that can make authorized requests.
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Users can configure client certificate or rely on device certificates to
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establish a mutual TLS channel, if the `GOOGLE_API_USE_CLIENT_CERTIFICATE`
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variable is explicitly set to `true`.
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Example::
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import google.auth
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import google.auth.transport.grpc
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import google.auth.transport.requests
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from google.cloud.speech.v1 import cloud_speech_pb2
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# Get credentials.
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credentials, _ = google.auth.default()
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# Get an HTTP request function to refresh credentials.
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request = google.auth.transport.requests.Request()
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# Create a channel.
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channel = google.auth.transport.grpc.secure_authorized_channel(
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credentials, regular_endpoint, request,
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ssl_credentials=grpc.ssl_channel_credentials())
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# Use the channel to create a stub.
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cloud_speech.create_Speech_stub(channel)
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Usage:
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There are actually a couple of options to create a channel, depending on if
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you want to create a regular or mutual TLS channel.
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First let's list the endpoints (regular vs mutual TLS) to choose from::
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regular_endpoint = 'speech.googleapis.com:443'
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mtls_endpoint = 'speech.mtls.googleapis.com:443'
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Option 1: create a regular (non-mutual) TLS channel by explicitly setting
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the ssl_credentials::
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regular_ssl_credentials = grpc.ssl_channel_credentials()
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channel = google.auth.transport.grpc.secure_authorized_channel(
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credentials, regular_endpoint, request,
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ssl_credentials=regular_ssl_credentials)
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Option 2: create a mutual TLS channel by calling a callback which returns
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the client side certificate and the key (Note that
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`GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
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set to `true`)::
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def my_client_cert_callback():
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code_to_load_client_cert_and_key()
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if loaded:
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return (pem_cert_bytes, pem_key_bytes)
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raise MyClientCertFailureException()
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try:
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channel = google.auth.transport.grpc.secure_authorized_channel(
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credentials, mtls_endpoint, request,
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client_cert_callback=my_client_cert_callback)
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except MyClientCertFailureException:
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# handle the exception
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Option 3: use application default SSL credentials. It searches and uses
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the command in a context aware metadata file, which is available on devices
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with endpoint verification support (Note that
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`GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
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set to `true`).
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See https://cloud.google.com/endpoint-verification/docs/overview::
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try:
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default_ssl_credentials = SslCredentials()
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except:
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# Exception can be raised if the context aware metadata is malformed.
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# See :class:`SslCredentials` for the possible exceptions.
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# Choose the endpoint based on the SSL credentials type.
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if default_ssl_credentials.is_mtls:
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endpoint_to_use = mtls_endpoint
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else:
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endpoint_to_use = regular_endpoint
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channel = google.auth.transport.grpc.secure_authorized_channel(
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credentials, endpoint_to_use, request,
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ssl_credentials=default_ssl_credentials)
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Option 4: not setting ssl_credentials and client_cert_callback. For devices
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without endpoint verification support or `GOOGLE_API_USE_CLIENT_CERTIFICATE`
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environment variable is not `true`, a regular TLS channel is created;
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otherwise, a mutual TLS channel is created, however, the call should be
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wrapped in a try/except block in case of malformed context aware metadata.
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The following code uses regular_endpoint, it works the same no matter the
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created channle is regular or mutual TLS. Regular endpoint ignores client
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certificate and key::
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channel = google.auth.transport.grpc.secure_authorized_channel(
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credentials, regular_endpoint, request)
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The following code uses mtls_endpoint, if the created channle is regular,
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and API mtls_endpoint is confgured to require client SSL credentials, API
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calls using this channel will be rejected::
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channel = google.auth.transport.grpc.secure_authorized_channel(
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credentials, mtls_endpoint, request)
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Args:
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credentials (google.auth.credentials.Credentials): The credentials to
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add to requests.
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request (google.auth.transport.Request): A HTTP transport request
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object used to refresh credentials as needed. Even though gRPC
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is a separate transport, there's no way to refresh the credentials
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without using a standard http transport.
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target (str): The host and port of the service.
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ssl_credentials (grpc.ChannelCredentials): Optional SSL channel
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credentials. This can be used to specify different certificates.
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This argument is mutually exclusive with client_cert_callback;
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providing both will raise an exception.
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If ssl_credentials and client_cert_callback are None, application
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default SSL credentials are used if `GOOGLE_API_USE_CLIENT_CERTIFICATE`
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environment variable is explicitly set to `true`, otherwise one way TLS
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SSL credentials are used.
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client_cert_callback (Callable[[], (bytes, bytes)]): Optional
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callback function to obtain client certicate and key for mutual TLS
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connection. This argument is mutually exclusive with
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ssl_credentials; providing both will raise an exception.
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This argument does nothing unless `GOOGLE_API_USE_CLIENT_CERTIFICATE`
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environment variable is explicitly set to `true`.
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kwargs: Additional arguments to pass to :func:`grpc.secure_channel`.
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Returns:
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grpc.Channel: The created gRPC channel.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
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creation failed for any reason.
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"""
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# Create the metadata plugin for inserting the authorization header.
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metadata_plugin = AuthMetadataPlugin(credentials, request)
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# Create a set of grpc.CallCredentials using the metadata plugin.
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google_auth_credentials = grpc.metadata_call_credentials(metadata_plugin)
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if ssl_credentials and client_cert_callback:
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raise ValueError(
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"Received both ssl_credentials and client_cert_callback; "
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"these are mutually exclusive."
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)
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# If SSL credentials are not explicitly set, try client_cert_callback and ADC.
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if not ssl_credentials:
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use_client_cert = os.getenv(
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environment_vars.GOOGLE_API_USE_CLIENT_CERTIFICATE, "false"
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)
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if use_client_cert == "true" and client_cert_callback:
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# Use the callback if provided.
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cert, key = client_cert_callback()
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ssl_credentials = grpc.ssl_channel_credentials(
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certificate_chain=cert, private_key=key
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)
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elif use_client_cert == "true":
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# Use application default SSL credentials.
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adc_ssl_credentils = SslCredentials()
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ssl_credentials = adc_ssl_credentils.ssl_credentials
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else:
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ssl_credentials = grpc.ssl_channel_credentials()
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# Combine the ssl credentials and the authorization credentials.
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composite_credentials = grpc.composite_channel_credentials(
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ssl_credentials, google_auth_credentials
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)
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return grpc.secure_channel(target, composite_credentials, **kwargs)
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class SslCredentials:
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"""Class for application default SSL credentials.
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The behavior is controlled by `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment
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variable whose default value is `false`. Client certificate will not be used
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unless the environment variable is explicitly set to `true`. See
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https://google.aip.dev/auth/4114
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If the environment variable is `true`, then for devices with endpoint verification
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support, a device certificate will be automatically loaded and mutual TLS will
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be established.
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See https://cloud.google.com/endpoint-verification/docs/overview.
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"""
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def __init__(self):
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use_client_cert = os.getenv(
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environment_vars.GOOGLE_API_USE_CLIENT_CERTIFICATE, "false"
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)
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if use_client_cert != "true":
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self._is_mtls = False
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else:
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# Load client SSL credentials.
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metadata_path = _mtls_helper._check_dca_metadata_path(
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_mtls_helper.CONTEXT_AWARE_METADATA_PATH
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)
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self._is_mtls = metadata_path is not None
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@property
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def ssl_credentials(self):
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"""Get the created SSL channel credentials.
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For devices with endpoint verification support, if the device certificate
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loading has any problems, corresponding exceptions will be raised. For
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a device without endpoint verification support, no exceptions will be
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raised.
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Returns:
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grpc.ChannelCredentials: The created grpc channel credentials.
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Raises:
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google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
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creation failed for any reason.
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"""
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if self._is_mtls:
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try:
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_, cert, key, _ = _mtls_helper.get_client_ssl_credentials()
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self._ssl_credentials = grpc.ssl_channel_credentials(
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certificate_chain=cert, private_key=key
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)
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except exceptions.ClientCertError as caught_exc:
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new_exc = exceptions.MutualTLSChannelError(caught_exc)
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six.raise_from(new_exc, caught_exc)
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else:
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self._ssl_credentials = grpc.ssl_channel_credentials()
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return self._ssl_credentials
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@property
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def is_mtls(self):
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"""Indicates if the created SSL channel credentials is mutual TLS."""
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return self._is_mtls
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