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1# Copyright 2016 Google LLC
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7# http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
15"""Authorization support for gRPC."""
17from __future__ import absolute_import
19import logging
20import os
22from google.auth import environment_vars
23from google.auth import exceptions
24from google.auth.transport import _mtls_helper
25from google.oauth2 import service_account
27try:
28 import grpc # type: ignore
29except ImportError as caught_exc: # pragma: NO COVER
30 raise ImportError(
31 "gRPC is not installed from please install the grpcio package to use the gRPC transport."
32 ) from caught_exc
34_LOGGER = logging.getLogger(__name__)
37class AuthMetadataPlugin(grpc.AuthMetadataPlugin):
38 """A `gRPC AuthMetadataPlugin`_ that inserts the credentials into each
39 request.
41 .. _gRPC AuthMetadataPlugin:
42 http://www.grpc.io/grpc/python/grpc.html#grpc.AuthMetadataPlugin
44 Args:
45 credentials (google.auth.credentials.Credentials): The credentials to
46 add to requests.
47 request (google.auth.transport.Request): A HTTP transport request
48 object used to refresh credentials as needed.
49 default_host (Optional[str]): A host like "pubsub.googleapis.com".
50 This is used when a self-signed JWT is created from service
51 account credentials.
52 """
54 def __init__(self, credentials, request, default_host=None):
55 # pylint: disable=no-value-for-parameter
56 # pylint doesn't realize that the super method takes no arguments
57 # because this class is the same name as the superclass.
58 super(AuthMetadataPlugin, self).__init__()
59 self._credentials = credentials
60 self._request = request
61 self._default_host = default_host
63 def _get_authorization_headers(self, context):
64 """Gets the authorization headers for a request.
66 Returns:
67 Sequence[Tuple[str, str]]: A list of request headers (key, value)
68 to add to the request.
69 """
70 headers = {}
72 # https://google.aip.dev/auth/4111
73 # Attempt to use self-signed JWTs when a service account is used.
74 # A default host must be explicitly provided since it cannot always
75 # be determined from the context.service_url.
76 if isinstance(self._credentials, service_account.Credentials):
77 self._credentials._create_self_signed_jwt(
78 "https://{}/".format(self._default_host) if self._default_host else None
79 )
81 self._credentials.before_request(
82 self._request, context.method_name, context.service_url, headers
83 )
85 return list(headers.items())
87 def __call__(self, context, callback):
88 """Passes authorization metadata into the given callback.
90 Args:
91 context (grpc.AuthMetadataContext): The RPC context.
92 callback (grpc.AuthMetadataPluginCallback): The callback that will
93 be invoked to pass in the authorization metadata.
94 """
95 callback(self._get_authorization_headers(context), None)
98def secure_authorized_channel(
99 credentials,
100 request,
101 target,
102 ssl_credentials=None,
103 client_cert_callback=None,
104 **kwargs
105):
106 """Creates a secure authorized gRPC channel.
108 This creates a channel with SSL and :class:`AuthMetadataPlugin`. This
109 channel can be used to create a stub that can make authorized requests.
110 Users can configure client certificate or rely on device certificates to
111 establish a mutual TLS channel, if the `GOOGLE_API_USE_CLIENT_CERTIFICATE`
112 variable is explicitly set to `true`.
114 Example::
116 import google.auth
117 import google.auth.transport.grpc
118 import google.auth.transport.requests
119 from google.cloud.speech.v1 import cloud_speech_pb2
121 # Get credentials.
122 credentials, _ = google.auth.default()
124 # Get an HTTP request function to refresh credentials.
125 request = google.auth.transport.requests.Request()
127 # Create a channel.
128 channel = google.auth.transport.grpc.secure_authorized_channel(
129 credentials, regular_endpoint, request,
130 ssl_credentials=grpc.ssl_channel_credentials())
132 # Use the channel to create a stub.
133 cloud_speech.create_Speech_stub(channel)
135 Usage:
137 There are actually a couple of options to create a channel, depending on if
138 you want to create a regular or mutual TLS channel.
140 First let's list the endpoints (regular vs mutual TLS) to choose from::
142 regular_endpoint = 'speech.googleapis.com:443'
143 mtls_endpoint = 'speech.mtls.googleapis.com:443'
145 Option 1: create a regular (non-mutual) TLS channel by explicitly setting
146 the ssl_credentials::
148 regular_ssl_credentials = grpc.ssl_channel_credentials()
150 channel = google.auth.transport.grpc.secure_authorized_channel(
151 credentials, regular_endpoint, request,
152 ssl_credentials=regular_ssl_credentials)
154 Option 2: create a mutual TLS channel by calling a callback which returns
155 the client side certificate and the key (Note that
156 `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
157 set to `true`)::
159 def my_client_cert_callback():
160 code_to_load_client_cert_and_key()
161 if loaded:
162 return (pem_cert_bytes, pem_key_bytes)
163 raise MyClientCertFailureException()
165 try:
166 channel = google.auth.transport.grpc.secure_authorized_channel(
167 credentials, mtls_endpoint, request,
168 client_cert_callback=my_client_cert_callback)
169 except MyClientCertFailureException:
170 # handle the exception
172 Option 3: use application default SSL credentials. It searches and uses
173 the command in a context aware metadata file, which is available on devices
174 with endpoint verification support (Note that
175 `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
176 set to `true`).
177 See https://cloud.google.com/endpoint-verification/docs/overview::
179 try:
180 default_ssl_credentials = SslCredentials()
181 except:
182 # Exception can be raised if the context aware metadata is malformed.
183 # See :class:`SslCredentials` for the possible exceptions.
185 # Choose the endpoint based on the SSL credentials type.
186 if default_ssl_credentials.is_mtls:
187 endpoint_to_use = mtls_endpoint
188 else:
189 endpoint_to_use = regular_endpoint
190 channel = google.auth.transport.grpc.secure_authorized_channel(
191 credentials, endpoint_to_use, request,
192 ssl_credentials=default_ssl_credentials)
194 Option 4: not setting ssl_credentials and client_cert_callback. For devices
195 without endpoint verification support or `GOOGLE_API_USE_CLIENT_CERTIFICATE`
196 environment variable is not `true`, a regular TLS channel is created;
197 otherwise, a mutual TLS channel is created, however, the call should be
198 wrapped in a try/except block in case of malformed context aware metadata.
200 The following code uses regular_endpoint, it works the same no matter the
201 created channle is regular or mutual TLS. Regular endpoint ignores client
202 certificate and key::
204 channel = google.auth.transport.grpc.secure_authorized_channel(
205 credentials, regular_endpoint, request)
207 The following code uses mtls_endpoint, if the created channle is regular,
208 and API mtls_endpoint is confgured to require client SSL credentials, API
209 calls using this channel will be rejected::
211 channel = google.auth.transport.grpc.secure_authorized_channel(
212 credentials, mtls_endpoint, request)
214 Args:
215 credentials (google.auth.credentials.Credentials): The credentials to
216 add to requests.
217 request (google.auth.transport.Request): A HTTP transport request
218 object used to refresh credentials as needed. Even though gRPC
219 is a separate transport, there's no way to refresh the credentials
220 without using a standard http transport.
221 target (str): The host and port of the service.
222 ssl_credentials (grpc.ChannelCredentials): Optional SSL channel
223 credentials. This can be used to specify different certificates.
224 This argument is mutually exclusive with client_cert_callback;
225 providing both will raise an exception.
226 If ssl_credentials and client_cert_callback are None, application
227 default SSL credentials are used if `GOOGLE_API_USE_CLIENT_CERTIFICATE`
228 environment variable is explicitly set to `true`, otherwise one way TLS
229 SSL credentials are used.
230 client_cert_callback (Callable[[], (bytes, bytes)]): Optional
231 callback function to obtain client certicate and key for mutual TLS
232 connection. This argument is mutually exclusive with
233 ssl_credentials; providing both will raise an exception.
234 This argument does nothing unless `GOOGLE_API_USE_CLIENT_CERTIFICATE`
235 environment variable is explicitly set to `true`.
236 kwargs: Additional arguments to pass to :func:`grpc.secure_channel`.
238 Returns:
239 grpc.Channel: The created gRPC channel.
241 Raises:
242 google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
243 creation failed for any reason.
244 """
245 # Create the metadata plugin for inserting the authorization header.
246 metadata_plugin = AuthMetadataPlugin(credentials, request)
248 # Create a set of grpc.CallCredentials using the metadata plugin.
249 google_auth_credentials = grpc.metadata_call_credentials(metadata_plugin)
251 if ssl_credentials and client_cert_callback:
252 raise exceptions.MalformedError(
253 "Received both ssl_credentials and client_cert_callback; "
254 "these are mutually exclusive."
255 )
257 # If SSL credentials are not explicitly set, try client_cert_callback and ADC.
258 if not ssl_credentials:
259 use_client_cert = os.getenv(
260 environment_vars.GOOGLE_API_USE_CLIENT_CERTIFICATE, "false"
261 )
262 if use_client_cert == "true" and client_cert_callback:
263 # Use the callback if provided.
264 cert, key = client_cert_callback()
265 ssl_credentials = grpc.ssl_channel_credentials(
266 certificate_chain=cert, private_key=key
267 )
268 elif use_client_cert == "true":
269 # Use application default SSL credentials.
270 adc_ssl_credentils = SslCredentials()
271 ssl_credentials = adc_ssl_credentils.ssl_credentials
272 else:
273 ssl_credentials = grpc.ssl_channel_credentials()
275 # Combine the ssl credentials and the authorization credentials.
276 composite_credentials = grpc.composite_channel_credentials(
277 ssl_credentials, google_auth_credentials
278 )
280 return grpc.secure_channel(target, composite_credentials, **kwargs)
283class SslCredentials:
284 """Class for application default SSL credentials.
286 The behavior is controlled by `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment
287 variable whose default value is `false`. Client certificate will not be used
288 unless the environment variable is explicitly set to `true`. See
289 https://google.aip.dev/auth/4114
291 If the environment variable is `true`, then for devices with endpoint verification
292 support, a device certificate will be automatically loaded and mutual TLS will
293 be established.
294 See https://cloud.google.com/endpoint-verification/docs/overview.
295 """
297 def __init__(self):
298 use_client_cert = os.getenv(
299 environment_vars.GOOGLE_API_USE_CLIENT_CERTIFICATE, "false"
300 )
301 if use_client_cert != "true":
302 self._is_mtls = False
303 else:
304 # Load client SSL credentials.
305 metadata_path = _mtls_helper._check_config_path(
306 _mtls_helper.CONTEXT_AWARE_METADATA_PATH
307 )
308 self._is_mtls = metadata_path is not None
310 @property
311 def ssl_credentials(self):
312 """Get the created SSL channel credentials.
314 For devices with endpoint verification support, if the device certificate
315 loading has any problems, corresponding exceptions will be raised. For
316 a device without endpoint verification support, no exceptions will be
317 raised.
319 Returns:
320 grpc.ChannelCredentials: The created grpc channel credentials.
322 Raises:
323 google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
324 creation failed for any reason.
325 """
326 if self._is_mtls:
327 try:
328 _, cert, key, _ = _mtls_helper.get_client_ssl_credentials()
329 self._ssl_credentials = grpc.ssl_channel_credentials(
330 certificate_chain=cert, private_key=key
331 )
332 except exceptions.ClientCertError as caught_exc:
333 new_exc = exceptions.MutualTLSChannelError(caught_exc)
334 raise new_exc from caught_exc
335 else:
336 self._ssl_credentials = grpc.ssl_channel_credentials()
338 return self._ssl_credentials
340 @property
341 def is_mtls(self):
342 """Indicates if the created SSL channel credentials is mutual TLS."""
343 return self._is_mtls