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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 """
53 def __init__(self, credentials, request, default_host=None):
54 # pylint: disable=no-value-for-parameter
55 # pylint doesn't realize that the super method takes no arguments
56 # because this class is the same name as the superclass.
57 super(AuthMetadataPlugin, self).__init__()
58 self._credentials = credentials
59 self._request = request
60 self._default_host = default_host
62 def _get_authorization_headers(self, context):
63 """Gets the authorization headers for a request.
65 Returns:
66 Sequence[Tuple[str, str]]: A list of request headers (key, value)
67 to add to the request.
68 """
69 headers = {}
71 # https://google.aip.dev/auth/4111
72 # Attempt to use self-signed JWTs when a service account is used.
73 # A default host must be explicitly provided since it cannot always
74 # be determined from the context.service_url.
75 if isinstance(self._credentials, service_account.Credentials):
76 self._credentials._create_self_signed_jwt(
77 "https://{}/".format(self._default_host) if self._default_host else None
78 )
80 self._credentials.before_request(
81 self._request, context.method_name, context.service_url, headers
82 )
84 return list(headers.items())
86 def __call__(self, context, callback):
87 """Passes authorization metadata into the given callback.
89 Args:
90 context (grpc.AuthMetadataContext): The RPC context.
91 callback (grpc.AuthMetadataPluginCallback): The callback that will
92 be invoked to pass in the authorization metadata.
93 """
94 callback(self._get_authorization_headers(context), None)
97def secure_authorized_channel(
98 credentials,
99 request,
100 target,
101 ssl_credentials=None,
102 client_cert_callback=None,
103 **kwargs
104):
105 """Creates a secure authorized gRPC channel.
107 This creates a channel with SSL and :class:`AuthMetadataPlugin`. This
108 channel can be used to create a stub that can make authorized requests.
109 Users can configure client certificate or rely on device certificates to
110 establish a mutual TLS channel, if the `GOOGLE_API_USE_CLIENT_CERTIFICATE`
111 variable is explicitly set to `true`.
113 Example::
115 import google.auth
116 import google.auth.transport.grpc
117 import google.auth.transport.requests
118 from google.cloud.speech.v1 import cloud_speech_pb2
120 # Get credentials.
121 credentials, _ = google.auth.default()
123 # Get an HTTP request function to refresh credentials.
124 request = google.auth.transport.requests.Request()
126 # Create a channel.
127 channel = google.auth.transport.grpc.secure_authorized_channel(
128 credentials, regular_endpoint, request,
129 ssl_credentials=grpc.ssl_channel_credentials())
131 # Use the channel to create a stub.
132 cloud_speech.create_Speech_stub(channel)
134 Usage:
136 There are actually a couple of options to create a channel, depending on if
137 you want to create a regular or mutual TLS channel.
139 First let's list the endpoints (regular vs mutual TLS) to choose from::
141 regular_endpoint = 'speech.googleapis.com:443'
142 mtls_endpoint = 'speech.mtls.googleapis.com:443'
144 Option 1: create a regular (non-mutual) TLS channel by explicitly setting
145 the ssl_credentials::
147 regular_ssl_credentials = grpc.ssl_channel_credentials()
149 channel = google.auth.transport.grpc.secure_authorized_channel(
150 credentials, request, regular_endpoint,
151 ssl_credentials=regular_ssl_credentials)
153 Option 2: create a mutual TLS channel by calling a callback which returns
154 the client side certificate and the key (Note that
155 `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
156 set to `true`)::
158 def my_client_cert_callback():
159 code_to_load_client_cert_and_key()
160 if loaded:
161 return (pem_cert_bytes, pem_key_bytes)
162 raise MyClientCertFailureException()
164 try:
165 channel = google.auth.transport.grpc.secure_authorized_channel(
166 credentials, request, mtls_endpoint,
167 client_cert_callback=my_client_cert_callback)
168 except MyClientCertFailureException:
169 # handle the exception
171 Option 3: use application default SSL credentials. It searches and uses
172 the command in a context aware metadata file, which is available on devices
173 with endpoint verification support (Note that
174 `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable must be explicitly
175 set to `true`).
176 See https://cloud.google.com/endpoint-verification/docs/overview::
178 try:
179 default_ssl_credentials = SslCredentials()
180 except:
181 # Exception can be raised if the context aware metadata is malformed.
182 # See :class:`SslCredentials` for the possible exceptions.
184 # Choose the endpoint based on the SSL credentials type.
185 if default_ssl_credentials.is_mtls:
186 endpoint_to_use = mtls_endpoint
187 else:
188 endpoint_to_use = regular_endpoint
189 channel = google.auth.transport.grpc.secure_authorized_channel(
190 credentials, request, endpoint_to_use,
191 ssl_credentials=default_ssl_credentials)
193 Option 4: not setting ssl_credentials and client_cert_callback. For devices
194 without endpoint verification support or `GOOGLE_API_USE_CLIENT_CERTIFICATE`
195 environment variable is not `true`, a regular TLS channel is created;
196 otherwise, a mutual TLS channel is created, however, the call should be
197 wrapped in a try/except block in case of malformed context aware metadata.
199 The following code uses regular_endpoint, it works the same no matter the
200 created channle is regular or mutual TLS. Regular endpoint ignores client
201 certificate and key::
203 channel = google.auth.transport.grpc.secure_authorized_channel(
204 credentials, request, regular_endpoint)
206 The following code uses mtls_endpoint, if the created channle is regular,
207 and API mtls_endpoint is confgured to require client SSL credentials, API
208 calls using this channel will be rejected::
210 channel = google.auth.transport.grpc.secure_authorized_channel(
211 credentials, request, mtls_endpoint)
213 Args:
214 credentials (google.auth.credentials.Credentials): The credentials to
215 add to requests.
216 request (google.auth.transport.Request): A HTTP transport request
217 object used to refresh credentials as needed. Even though gRPC
218 is a separate transport, there's no way to refresh the credentials
219 without using a standard http transport.
220 target (str): The host and port of the service.
221 ssl_credentials (grpc.ChannelCredentials): Optional SSL channel
222 credentials. This can be used to specify different certificates.
223 This argument is mutually exclusive with client_cert_callback;
224 providing both will raise an exception.
225 If ssl_credentials and client_cert_callback are None, application
226 default SSL credentials are used if `GOOGLE_API_USE_CLIENT_CERTIFICATE`
227 environment variable is explicitly set to `true`, otherwise one way TLS
228 SSL credentials are used.
229 client_cert_callback (Callable[[], (bytes, bytes)]): Optional
230 callback function to obtain client certicate and key for mutual TLS
231 connection. This argument is mutually exclusive with
232 ssl_credentials; providing both will raise an exception.
233 This argument does nothing unless `GOOGLE_API_USE_CLIENT_CERTIFICATE`
234 environment variable is explicitly set to `true`.
235 kwargs: Additional arguments to pass to :func:`grpc.secure_channel`.
237 Returns:
238 grpc.Channel: The created gRPC channel.
240 Raises:
241 google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
242 creation failed for any reason.
243 """
244 # Create the metadata plugin for inserting the authorization header.
245 metadata_plugin = AuthMetadataPlugin(credentials, request)
247 # Create a set of grpc.CallCredentials using the metadata plugin.
248 google_auth_credentials = grpc.metadata_call_credentials(metadata_plugin)
250 if ssl_credentials and client_cert_callback:
251 raise exceptions.MalformedError(
252 "Received both ssl_credentials and client_cert_callback; "
253 "these are mutually exclusive."
254 )
256 # If SSL credentials are not explicitly set, try client_cert_callback and ADC.
257 if not ssl_credentials:
258 use_client_cert = _mtls_helper.check_use_client_cert()
259 if use_client_cert and client_cert_callback:
260 # Use the callback if provided.
261 cert, key = client_cert_callback()
262 ssl_credentials = grpc.ssl_channel_credentials(
263 certificate_chain=cert, private_key=key
264 )
265 elif use_client_cert:
266 # Use application default SSL credentials.
267 adc_ssl_credentils = SslCredentials()
268 ssl_credentials = adc_ssl_credentils.ssl_credentials
269 else:
270 ssl_credentials = grpc.ssl_channel_credentials()
272 # Combine the ssl credentials and the authorization credentials.
273 composite_credentials = grpc.composite_channel_credentials(
274 ssl_credentials, google_auth_credentials
275 )
277 return grpc.secure_channel(target, composite_credentials, **kwargs)
280class SslCredentials:
281 """Class for application default SSL credentials.
283 Mutual TLS (mTLS) is enabled if either:
285 1. The `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is explicitly
286 set to `"true"`.
287 2. The `GOOGLE_API_USE_CLIENT_CERTIFICATE` environment variable is unset or empty,
288 but a valid workload certificate configuration is found (e.g., via the
289 `GOOGLE_API_CERTIFICATE_CONFIG` environment variable or the default gcloud config path).
291 See https://google.aip.dev/auth/4114 for client certificate discovery details.
293 If client certificate usage is enabled, then for devices with endpoint
294 verification support, a device certificate will be automatically loaded and
295 mutual TLS will be established.
296 See https://cloud.google.com/endpoint-verification/docs/overview.
297 """
299 def __init__(self):
300 use_client_cert = _mtls_helper.check_use_client_cert()
301 if not use_client_cert:
302 self._is_mtls = False
303 else:
304 self._is_mtls = mtls.has_default_client_cert_source()
306 @property
307 def ssl_credentials(self):
308 """Get the created SSL channel credentials.
310 For devices with endpoint verification support, if the device certificate
311 loading has any problems, corresponding exceptions will be raised. For
312 a device without endpoint verification support, no exceptions will be
313 raised.
315 Returns:
316 grpc.ChannelCredentials: The created grpc channel credentials.
318 Raises:
319 google.auth.exceptions.MutualTLSChannelError: If mutual TLS channel
320 creation failed for any reason.
321 """
322 if self._is_mtls:
323 try:
324 has_cert, cert, key, _ = _mtls_helper.get_client_ssl_credentials()
325 if has_cert:
326 self._ssl_credentials = grpc.ssl_channel_credentials(
327 certificate_chain=cert, private_key=key
328 )
329 else:
330 self._ssl_credentials = grpc.ssl_channel_credentials()
331 self._is_mtls = False
332 except (exceptions.ClientCertError, OSError) 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