# 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.
"""Authorization support for gRPC."""
from __future__ import absolute_import
import logging
import os
import six
from google.auth import environment_vars
from google.auth import exceptions
from google.auth.transport import _mtls_helper
from google.oauth2 import service_account
try:
import grpc # type: ignore
except ImportError as caught_exc: # pragma: NO COVER
six.raise_from(
ImportError(
"gRPC is not installed, please install the grpcio package "
"to use the gRPC transport."
),
caught_exc,
)
_LOGGER = logging.getLogger(__name__)
[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 google.cloud.speech.v1 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 = 'speech.googleapis.com:443'
mtls_endpoint = 'speech.mtls.googleapis.com:443'
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 https://cloud.google.com/endpoint-verification/docs/overview::
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 ValueError(
"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
https://google.aip.dev/auth/4114
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 https://cloud.google.com/endpoint-verification/docs/overview.
"""
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)
six.raise_from(new_exc, 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
