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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
21from google.auth import exceptions
22from google.auth.transport import _mtls_helper
23from google.auth.transport import mtls
24from google.oauth2 import service_account
26try:
27 import grpc # type: ignore
28except ImportError as caught_exc: # pragma: NO COVER
29 raise ImportError(
30 "gRPC is not installed from please install the grpcio package to use the gRPC transport."
31 ) from caught_exc
33_LOGGER = logging.getLogger(__name__)
36class AuthMetadataPlugin(grpc.AuthMetadataPlugin):
37 """A `gRPC AuthMetadataPlugin`_ that inserts the credentials into each
38 request.
40 .. _gRPC AuthMetadataPlugin:
41 http://www.grpc.io/grpc/python/grpc.html#grpc.AuthMetadataPlugin
43 Args:
44 credentials (google.auth.credentials.Credentials): The credentials to
45 add to requests.
46 request (google.auth.transport.Request): A HTTP transport request
47 object used to refresh credentials as needed.
48 default_host (Optional[str]): A host like "pubsub.googleapis.com".
49 This is used when a self-signed JWT is created from service
50 account credentials.
51 suppress_metrics_header (bool): When enabled, ``x-goog-api-client``
52 will be stripped from authorization headers.
53 """
55 def __init__(
56 self, credentials, request, default_host=None, *, suppress_metrics_header=False
57 ):
58 # pylint: disable=no-value-for-parameter
59 # pylint doesn't realize that the super method takes no arguments
60 # because this class is the same name as the superclass.
61 super(AuthMetadataPlugin, self).__init__()
62 self._credentials = credentials
63 self._request = request
64 self._default_host = default_host
65 self._suppress_metrics_header = suppress_metrics_header
67 def _get_authorization_headers(self, context):
68 """Gets the authorization headers for a request.
70 Returns:
71 Sequence[Tuple[str, str]]: A list of request headers (key, value)
72 to add to the request.
73 """
74 headers = {}
76 # https://google.aip.dev/auth/4111
77 # Attempt to use self-signed JWTs when a service account is used.
78 # A default host must be explicitly provided since it cannot always
79 # be determined from the context.service_url.
80 if isinstance(self._credentials, service_account.Credentials):
81 self._credentials._create_self_signed_jwt(
82 "https://{}/".format(self._default_host) if self._default_host else None
83 )
85 self._credentials.before_request(
86 self._request, context.method_name, context.service_url, headers
87 )
89 if self._suppress_metrics_header and "x-goog-api-client" in headers:
90 del headers["x-goog-api-client"]
92 return list(headers.items())
94 def __call__(self, context, callback):
95 """Passes authorization metadata into the given callback.
97 Args:
98 context (grpc.AuthMetadataContext): The RPC context.
99 callback (grpc.AuthMetadataPluginCallback): The callback that will
100 be invoked to pass in the authorization metadata.
101 """
102 callback(self._get_authorization_headers(context), None)
105def secure_authorized_channel(
106 credentials,
107 request,
108 target,
109 ssl_credentials=None,
110 client_cert_callback=None,
111 **kwargs
112):
113 """Creates a secure authorized gRPC channel.
115 This creates a channel with SSL and :class:`AuthMetadataPlugin`. This
116 channel can be used to create a stub that can make authorized requests.
117 Users can configure client certificate or rely on device certificates to
118 establish a mutual TLS channel, if the `GOOGLE_API_USE_CLIENT_CERTIFICATE`
119 variable is explicitly set to `true`.
121 Example::
123 import google.auth
124 import google.auth.transport.grpc
125 import google.auth.transport.requests
126 from google.cloud.speech.v1 import cloud_speech_pb2
128 # Get credentials.
129 credentials, _ = google.auth.default()
131 # Get an HTTP request function to refresh credentials.
132 request = google.auth.transport.requests.Request()
134 # Create a channel.
135 channel = google.auth.transport.grpc.secure_authorized_channel(
136 credentials, regular_endpoint, request,
137 ssl_credentials=grpc.ssl_channel_credentials())
139 # Use the channel to create a stub.
140 cloud_speech.create_Speech_stub(channel)
142 Usage:
144 There are actually a couple of options to create a channel, depending on if
145 you want to create a regular or mutual TLS channel.
147 First let's list the endpoints (regular vs mutual TLS) to choose from::
149 regular_endpoint = 'speech.googleapis.com:443'
150 mtls_endpoint = 'speech.mtls.googleapis.com:443'
152 Option 1: create a regular (non-mutual) TLS channel by explicitly setting
153 the ssl_credentials::
155 regular_ssl_credentials = grpc.ssl_channel_credentials()
157 channel = google.auth.transport.grpc.secure_authorized_channel(
158 credentials, request, regular_endpoint,
159 ssl_credentials=regular_ssl_credentials)
161 Option 2: create a mutual TLS channel by calling a callback which returns
162 the client side certificate and the key (Note that
163 `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
164 set to `true`)::
166 def my_client_cert_callback():
167 code_to_load_client_cert_and_key()
168 if loaded:
169 return (pem_cert_bytes, pem_key_bytes)
170 raise MyClientCertFailureException()
172 try:
173 channel = google.auth.transport.grpc.secure_authorized_channel(
174 credentials, request, mtls_endpoint,
175 client_cert_callback=my_client_cert_callback)
176 except MyClientCertFailureException:
177 # handle the exception
179 Option 3: use application default SSL credentials. It searches and uses
180 the command in a context aware metadata file, which is available on devices
181 with endpoint verification support (Note that
182 `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
183 set to `true`).
184 See https://cloud.google.com/endpoint-verification/docs/overview::
186 try:
187 default_ssl_credentials = SslCredentials()
188 except:
189 # Exception can be raised if the context aware metadata is malformed.
190 # See :class:`SslCredentials` for the possible exceptions.
192 # Choose the endpoint based on the SSL credentials type.
193 if default_ssl_credentials.is_mtls:
194 endpoint_to_use = mtls_endpoint
195 else:
196 endpoint_to_use = regular_endpoint
197 channel = google.auth.transport.grpc.secure_authorized_channel(
198 credentials, request, endpoint_to_use,
199 ssl_credentials=default_ssl_credentials)
201 Option 4: not setting ssl_credentials and client_cert_callback. For devices
202 without endpoint verification support or `GOOGLE_API_USE_CLIENT_CERTIFICATE`
203 environment variable is not `true`, a regular TLS channel is created;
204 otherwise, a mutual TLS channel is created, however, the call should be
205 wrapped in a try/except block in case of malformed context aware metadata.
207 The following code uses regular_endpoint, it works the same no matter the
208 created channle is regular or mutual TLS. Regular endpoint ignores client
209 certificate and key::
211 channel = google.auth.transport.grpc.secure_authorized_channel(
212 credentials, request, regular_endpoint)
214 The following code uses mtls_endpoint, if the created channle is regular,
215 and API mtls_endpoint is confgured to require client SSL credentials, API
216 calls using this channel will be rejected::
218 channel = google.auth.transport.grpc.secure_authorized_channel(
219 credentials, request, mtls_endpoint)
221 Args:
222 credentials (google.auth.credentials.Credentials): The credentials to
223 add to requests.
224 request (google.auth.transport.Request): A HTTP transport request
225 object used to refresh credentials as needed. Even though gRPC
226 is a separate transport, there's no way to refresh the credentials
227 without using a standard http transport.
228 target (str): The host and port of the service.
229 ssl_credentials (grpc.ChannelCredentials): Optional SSL channel
230 credentials. This can be used to specify different certificates.
231 This argument is mutually exclusive with client_cert_callback;
232 providing both will raise an exception.
233 If ssl_credentials and client_cert_callback are None, application
234 default SSL credentials are used if `GOOGLE_API_USE_CLIENT_CERTIFICATE`
235 environment variable is explicitly set to `true`, otherwise one way TLS
236 SSL credentials are used.
237 client_cert_callback (Callable[[], (bytes, bytes)]): Optional
238 callback function to obtain client certicate and key for mutual TLS
239 connection. This argument is mutually exclusive with
240 ssl_credentials; providing both will raise an exception.
241 This argument does nothing unless `GOOGLE_API_USE_CLIENT_CERTIFICATE`
242 environment variable is explicitly set to `true`.
243 kwargs: Additional arguments to pass to :func:`grpc.secure_channel`.
245 Returns:
246 grpc.Channel: The created gRPC channel.
248 Raises:
249 google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
250 creation failed for any reason.
251 """
252 # Create the metadata plugin for inserting the authorization header.
253 metadata_plugin = AuthMetadataPlugin(credentials, request)
255 # Create a set of grpc.CallCredentials using the metadata plugin.
256 google_auth_credentials = grpc.metadata_call_credentials(metadata_plugin)
258 if ssl_credentials and client_cert_callback:
259 raise exceptions.MalformedError(
260 "Received both ssl_credentials and client_cert_callback; "
261 "these are mutually exclusive."
262 )
264 # If SSL credentials are not explicitly set, try client_cert_callback and ADC.
265 if not ssl_credentials:
266 use_client_cert = _mtls_helper.check_use_client_cert()
267 if use_client_cert and client_cert_callback:
268 # Use the callback if provided.
269 cert, key = client_cert_callback()
270 ssl_credentials = grpc.ssl_channel_credentials(
271 certificate_chain=cert, private_key=key
272 )
273 elif use_client_cert:
274 # Use application default SSL credentials.
275 adc_ssl_credentils = SslCredentials()
276 ssl_credentials = adc_ssl_credentils.ssl_credentials
277 else:
278 ssl_credentials = grpc.ssl_channel_credentials()
280 # Combine the ssl credentials and the authorization credentials.
281 composite_credentials = grpc.composite_channel_credentials(
282 ssl_credentials, google_auth_credentials
283 )
285 return grpc.secure_channel(target, composite_credentials, **kwargs)
288class SslCredentials:
289 """Class for application default SSL credentials.
291 Mutual TLS (mTLS) is enabled if either:
293 1. The `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is explicitly
294 set to `"true"`.
295 2. The `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is unset or empty,
296 but a valid workload certificate configuration is found (e.g., via the
297 `GOOGLE_API_CERTIFICATE_CONFIG` environment variable or the default gcloud config path).
299 See https://google.aip.dev/auth/4114 for client certificate discovery details.
301 If client certificate usage is enabled, then for devices with endpoint
302 verification support, a device certificate will be automatically loaded and
303 mutual TLS will be established.
304 See https://cloud.google.com/endpoint-verification/docs/overview.
305 """
307 def __init__(self):
308 use_client_cert = _mtls_helper.check_use_client_cert()
309 if not use_client_cert:
310 self._is_mtls = False
311 else:
312 self._is_mtls = mtls.has_default_client_cert_source()
314 @property
315 def ssl_credentials(self):
316 """Get the created SSL channel credentials.
318 For devices with endpoint verification support, if the device certificate
319 loading has any problems, corresponding exceptions will be raised. For
320 a device without endpoint verification support, no exceptions will be
321 raised.
323 Returns:
324 grpc.ChannelCredentials: The created grpc channel credentials.
326 Raises:
327 google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
328 creation failed for any reason.
329 """
330 if self._is_mtls:
331 try:
332 has_cert, cert, key, _ = _mtls_helper.get_client_ssl_credentials()
333 if has_cert:
334 self._ssl_credentials = grpc.ssl_channel_credentials(
335 certificate_chain=cert, private_key=key
336 )
337 else:
338 self._ssl_credentials = grpc.ssl_channel_credentials()
339 self._is_mtls = False
340 except (exceptions.ClientCertError, OSError) as caught_exc:
341 new_exc = exceptions.MutualTLSChannelError(caught_exc)
342 raise new_exc from caught_exc
343 else:
344 self._ssl_credentials = grpc.ssl_channel_credentials()
346 return self._ssl_credentials
348 @property
349 def is_mtls(self):
350 """Indicates if the created SSL channel credentials is mutual TLS."""
351 return self._is_mtls