aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/python/google-auth/py3/google/auth/impersonated_credentials.py
blob: 3c6f8712a9b879fa12ecb8edcf29af4607945987 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
# Copyright 2018 Google Inc.
#
# 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.

"""Google Cloud Impersonated credentials.

This module provides authentication for applications where local credentials
impersonates a remote service account using `IAM Credentials API`_.

This class can be used to impersonate a service account as long as the original
Credential object has the "Service Account Token Creator" role on the target
service account.

    .. _IAM Credentials API:
        https://cloud.google.com/iam/credentials/reference/rest/
"""

import base64
import copy
from datetime import datetime
import http.client as http_client
import json

from google.auth import _helpers
from google.auth import credentials
from google.auth import exceptions
from google.auth import iam
from google.auth import jwt
from google.auth import metrics


_REFRESH_ERROR = "Unable to acquire impersonated credentials"

_DEFAULT_TOKEN_LIFETIME_SECS = 3600  # 1 hour in seconds


def _make_iam_token_request(
    request, principal, headers, body, iam_endpoint_override=None
):
    """Makes a request to the Google Cloud IAM service for an access token.
    Args:
        request (Request): The Request object to use.
        principal (str): The principal to request an access token for.
        headers (Mapping[str, str]): Map of headers to transmit.
        body (Mapping[str, str]): JSON Payload body for the iamcredentials
            API call.
        iam_endpoint_override (Optiona[str]): The full IAM endpoint override
            with the target_principal embedded. This is useful when supporting
            impersonation with regional endpoints.

    Raises:
        google.auth.exceptions.TransportError: Raised if there is an underlying
            HTTP connection error
        google.auth.exceptions.RefreshError: Raised if the impersonated
            credentials are not available.  Common reasons are
            `iamcredentials.googleapis.com` is not enabled or the
            `Service Account Token Creator` is not assigned
    """
    iam_endpoint = iam_endpoint_override or iam._IAM_ENDPOINT.format(principal)

    body = json.dumps(body).encode("utf-8")

    response = request(url=iam_endpoint, method="POST", headers=headers, body=body)

    # support both string and bytes type response.data
    response_body = (
        response.data.decode("utf-8")
        if hasattr(response.data, "decode")
        else response.data
    )

    if response.status != http_client.OK:
        raise exceptions.RefreshError(_REFRESH_ERROR, response_body)

    try:
        token_response = json.loads(response_body)
        token = token_response["accessToken"]
        expiry = datetime.strptime(token_response["expireTime"], "%Y-%m-%dT%H:%M:%SZ")

        return token, expiry

    except (KeyError, ValueError) as caught_exc:
        new_exc = exceptions.RefreshError(
            "{}: No access token or invalid expiration in response.".format(
                _REFRESH_ERROR
            ),
            response_body,
        )
        raise new_exc from caught_exc


class Credentials(
    credentials.Scoped, credentials.CredentialsWithQuotaProject, credentials.Signing
):
    """This module defines impersonated credentials which are essentially
    impersonated identities.

    Impersonated Credentials allows credentials issued to a user or
    service account to impersonate another. The target service account must
    grant the originating credential principal the
    `Service Account Token Creator`_ IAM role:

    For more information about Token Creator IAM role and
    IAMCredentials API, see
    `Creating Short-Lived Service Account Credentials`_.

    .. _Service Account Token Creator:
        https://cloud.google.com/iam/docs/service-accounts#the_service_account_token_creator_role

    .. _Creating Short-Lived Service Account Credentials:
        https://cloud.google.com/iam/docs/creating-short-lived-service-account-credentials

    Usage:

    First grant source_credentials the `Service Account Token Creator`
    role on the target account to impersonate.   In this example, the
    service account represented by svc_account.json has the
    token creator role on
    `impersonated-account@_project_.iam.gserviceaccount.com`.

    Enable the IAMCredentials API on the source project:
    `gcloud services enable iamcredentials.googleapis.com`.

    Initialize a source credential which does not have access to
    list bucket::

        from google.oauth2 import service_account

        target_scopes = [
            'https://www.googleapis.com/auth/devstorage.read_only']

        source_credentials = (
            service_account.Credentials.from_service_account_file(
                '/path/to/svc_account.json',
                scopes=target_scopes))

    Now use the source credentials to acquire credentials to impersonate
    another service account::

        from google.auth import impersonated_credentials

        target_credentials = impersonated_credentials.Credentials(
          source_credentials=source_credentials,
          target_principal='impersonated-account@_project_.iam.gserviceaccount.com',
          target_scopes = target_scopes,
          lifetime=500)

    Resource access is granted::

        client = storage.Client(credentials=target_credentials)
        buckets = client.list_buckets(project='your_project')
        for bucket in buckets:
          print(bucket.name)
    """

    def __init__(
        self,
        source_credentials,
        target_principal,
        target_scopes,
        delegates=None,
        lifetime=_DEFAULT_TOKEN_LIFETIME_SECS,
        quota_project_id=None,
        iam_endpoint_override=None,
    ):
        """
        Args:
            source_credentials (google.auth.Credentials): The source credential
                used as to acquire the impersonated credentials.
            target_principal (str): The service account to impersonate.
            target_scopes (Sequence[str]): Scopes to request during the
                authorization grant.
            delegates (Sequence[str]): The chained list of delegates required
                to grant the final access_token.  If set, the sequence of
                identities must have "Service Account Token Creator" capability
                granted to the prceeding identity.  For example, if set to
                [serviceAccountB, serviceAccountC], the source_credential
                must have the Token Creator role on serviceAccountB.
                serviceAccountB must have the Token Creator on
                serviceAccountC.
                Finally, C must have Token Creator on target_principal.
                If left unset, source_credential must have that role on
                target_principal.
            lifetime (int): Number of seconds the delegated credential should
                be valid for (upto 3600).
            quota_project_id (Optional[str]): The project ID used for quota and billing.
                This project may be different from the project used to
                create the credentials.
            iam_endpoint_override (Optiona[str]): The full IAM endpoint override
                with the target_principal embedded. This is useful when supporting
                impersonation with regional endpoints.
        """

        super(Credentials, self).__init__()

        self._source_credentials = copy.copy(source_credentials)
        # Service account source credentials must have the _IAM_SCOPE
        # added to refresh correctly. User credentials cannot have
        # their original scopes modified.
        if isinstance(self._source_credentials, credentials.Scoped):
            self._source_credentials = self._source_credentials.with_scopes(
                iam._IAM_SCOPE
            )
            # If the source credential is service account and self signed jwt
            # is needed, we need to create a jwt credential inside it
            if (
                hasattr(self._source_credentials, "_create_self_signed_jwt")
                and self._source_credentials._always_use_jwt_access
            ):
                self._source_credentials._create_self_signed_jwt(None)
        self._target_principal = target_principal
        self._target_scopes = target_scopes
        self._delegates = delegates
        self._lifetime = lifetime or _DEFAULT_TOKEN_LIFETIME_SECS
        self.token = None
        self.expiry = _helpers.utcnow()
        self._quota_project_id = quota_project_id
        self._iam_endpoint_override = iam_endpoint_override

    def _metric_header_for_usage(self):
        return metrics.CRED_TYPE_SA_IMPERSONATE

    @_helpers.copy_docstring(credentials.Credentials)
    def refresh(self, request):
        self._update_token(request)

    def _update_token(self, request):
        """Updates credentials with a new access_token representing
        the impersonated account.

        Args:
            request (google.auth.transport.requests.Request): Request object
                to use for refreshing credentials.
        """

        # Refresh our source credentials if it is not valid.
        if (
            self._source_credentials.token_state == credentials.TokenState.STALE
            or self._source_credentials.token_state == credentials.TokenState.INVALID
        ):
            self._source_credentials.refresh(request)

        body = {
            "delegates": self._delegates,
            "scope": self._target_scopes,
            "lifetime": str(self._lifetime) + "s",
        }

        headers = {
            "Content-Type": "application/json",
            metrics.API_CLIENT_HEADER: metrics.token_request_access_token_impersonate(),
        }

        # Apply the source credentials authentication info.
        self._source_credentials.apply(headers)

        self.token, self.expiry = _make_iam_token_request(
            request=request,
            principal=self._target_principal,
            headers=headers,
            body=body,
            iam_endpoint_override=self._iam_endpoint_override,
        )

    def sign_bytes(self, message):
        from google.auth.transport.requests import AuthorizedSession

        iam_sign_endpoint = iam._IAM_SIGN_ENDPOINT.format(self._target_principal)

        body = {
            "payload": base64.b64encode(message).decode("utf-8"),
            "delegates": self._delegates,
        }

        headers = {"Content-Type": "application/json"}

        authed_session = AuthorizedSession(self._source_credentials)

        try:
            response = authed_session.post(
                url=iam_sign_endpoint, headers=headers, json=body
            )
        finally:
            authed_session.close()

        if response.status_code != http_client.OK:
            raise exceptions.TransportError(
                "Error calling sign_bytes: {}".format(response.json())
            )

        return base64.b64decode(response.json()["signedBlob"])

    @property
    def signer_email(self):
        return self._target_principal

    @property
    def service_account_email(self):
        return self._target_principal

    @property
    def signer(self):
        return self

    @property
    def requires_scopes(self):
        return not self._target_scopes

    @_helpers.copy_docstring(credentials.CredentialsWithQuotaProject)
    def with_quota_project(self, quota_project_id):
        return self.__class__(
            self._source_credentials,
            target_principal=self._target_principal,
            target_scopes=self._target_scopes,
            delegates=self._delegates,
            lifetime=self._lifetime,
            quota_project_id=quota_project_id,
            iam_endpoint_override=self._iam_endpoint_override,
        )

    @_helpers.copy_docstring(credentials.Scoped)
    def with_scopes(self, scopes, default_scopes=None):
        return self.__class__(
            self._source_credentials,
            target_principal=self._target_principal,
            target_scopes=scopes or default_scopes,
            delegates=self._delegates,
            lifetime=self._lifetime,
            quota_project_id=self._quota_project_id,
            iam_endpoint_override=self._iam_endpoint_override,
        )


class IDTokenCredentials(credentials.CredentialsWithQuotaProject):
    """Open ID Connect ID Token-based service account credentials.

    """

    def __init__(
        self,
        target_credentials,
        target_audience=None,
        include_email=False,
        quota_project_id=None,
    ):
        """
        Args:
            target_credentials (google.auth.Credentials): The target
                credential used as to acquire the id tokens for.
            target_audience (string): Audience to issue the token for.
            include_email (bool): Include email in IdToken
            quota_project_id (Optional[str]):  The project ID used for
                quota and billing.
        """
        super(IDTokenCredentials, self).__init__()

        if not isinstance(target_credentials, Credentials):
            raise exceptions.GoogleAuthError(
                "Provided Credential must be " "impersonated_credentials"
            )
        self._target_credentials = target_credentials
        self._target_audience = target_audience
        self._include_email = include_email
        self._quota_project_id = quota_project_id

    def from_credentials(self, target_credentials, target_audience=None):
        return self.__class__(
            target_credentials=target_credentials,
            target_audience=target_audience,
            include_email=self._include_email,
            quota_project_id=self._quota_project_id,
        )

    def with_target_audience(self, target_audience):
        return self.__class__(
            target_credentials=self._target_credentials,
            target_audience=target_audience,
            include_email=self._include_email,
            quota_project_id=self._quota_project_id,
        )

    def with_include_email(self, include_email):
        return self.__class__(
            target_credentials=self._target_credentials,
            target_audience=self._target_audience,
            include_email=include_email,
            quota_project_id=self._quota_project_id,
        )

    @_helpers.copy_docstring(credentials.CredentialsWithQuotaProject)
    def with_quota_project(self, quota_project_id):
        return self.__class__(
            target_credentials=self._target_credentials,
            target_audience=self._target_audience,
            include_email=self._include_email,
            quota_project_id=quota_project_id,
        )

    @_helpers.copy_docstring(credentials.Credentials)
    def refresh(self, request):
        from google.auth.transport.requests import AuthorizedSession

        iam_sign_endpoint = iam._IAM_IDTOKEN_ENDPOINT.format(
            self._target_credentials.signer_email
        )

        body = {
            "audience": self._target_audience,
            "delegates": self._target_credentials._delegates,
            "includeEmail": self._include_email,
        }

        headers = {
            "Content-Type": "application/json",
            metrics.API_CLIENT_HEADER: metrics.token_request_id_token_impersonate(),
        }

        authed_session = AuthorizedSession(
            self._target_credentials._source_credentials, auth_request=request
        )

        try:
            response = authed_session.post(
                url=iam_sign_endpoint,
                headers=headers,
                data=json.dumps(body).encode("utf-8"),
            )
        finally:
            authed_session.close()

        if response.status_code != http_client.OK:
            raise exceptions.RefreshError(
                "Error getting ID token: {}".format(response.json())
            )

        id_token = response.json()["token"]
        self.token = id_token
        self.expiry = datetime.utcfromtimestamp(
            jwt.decode(id_token, verify=False)["exp"]
        )