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.
14
15
16"""Interfaces for credentials."""
17
18import abc
19from enum import Enum
20import os
21from typing import List
22
23from google.auth import _helpers, environment_vars
24from google.auth import exceptions
25from google.auth import metrics
26from google.auth._credentials_base import _BaseCredentials
27from google.auth._default import _LOGGER
28from google.auth._refresh_worker import RefreshThreadManager
29
30DEFAULT_UNIVERSE_DOMAIN = "googleapis.com"
31NO_OP_TRUST_BOUNDARY_LOCATIONS: List[str] = []
32NO_OP_TRUST_BOUNDARY_ENCODED_LOCATIONS = "0x0"
33
34
35class Credentials(_BaseCredentials):
36 """Base class for all credentials.
37
38 All credentials have a :attr:`token` that is used for authentication and
39 may also optionally set an :attr:`expiry` to indicate when the token will
40 no longer be valid.
41
42 Most credentials will be :attr:`invalid` until :meth:`refresh` is called.
43 Credentials can do this automatically before the first HTTP request in
44 :meth:`before_request`.
45
46 Although the token and expiration will change as the credentials are
47 :meth:`refreshed <refresh>` and used, credentials should be considered
48 immutable. Various credentials will accept configuration such as private
49 keys, scopes, and other options. These options are not changeable after
50 construction. Some classes will provide mechanisms to copy the credentials
51 with modifications such as :meth:`ScopedCredentials.with_scopes`.
52 """
53
54 def __init__(self):
55 super(Credentials, self).__init__()
56
57 self.expiry = None
58 """Optional[datetime]: When the token expires and is no longer valid.
59 If this is None, the token is assumed to never expire."""
60 self._quota_project_id = None
61 """Optional[str]: Project to use for quota and billing purposes."""
62 self._trust_boundary = None
63 """Optional[dict]: Cache of a trust boundary response which has a list
64 of allowed regions and an encoded string representation of credentials
65 trust boundary."""
66 self._universe_domain = DEFAULT_UNIVERSE_DOMAIN
67 """Optional[str]: The universe domain value, default is googleapis.com
68 """
69
70 self._use_non_blocking_refresh = False
71 self._refresh_worker = RefreshThreadManager()
72
73 @property
74 def expired(self):
75 """Checks if the credentials are expired.
76
77 Note that credentials can be invalid but not expired because
78 Credentials with :attr:`expiry` set to None is considered to never
79 expire.
80
81 .. deprecated:: v2.24.0
82 Prefer checking :attr:`token_state` instead.
83 """
84 if not self.expiry:
85 return False
86 # Remove some threshold from expiry to err on the side of reporting
87 # expiration early so that we avoid the 401-refresh-retry loop.
88 skewed_expiry = self.expiry - _helpers.REFRESH_THRESHOLD
89 return _helpers.utcnow() >= skewed_expiry
90
91 @property
92 def valid(self):
93 """Checks the validity of the credentials.
94
95 This is True if the credentials have a :attr:`token` and the token
96 is not :attr:`expired`.
97
98 .. deprecated:: v2.24.0
99 Prefer checking :attr:`token_state` instead.
100 """
101 return self.token is not None and not self.expired
102
103 @property
104 def token_state(self):
105 """
106 See `:obj:`TokenState`
107 """
108 if self.token is None:
109 return TokenState.INVALID
110
111 # Credentials that can't expire are always treated as fresh.
112 if self.expiry is None:
113 return TokenState.FRESH
114
115 expired = _helpers.utcnow() >= self.expiry
116 if expired:
117 return TokenState.INVALID
118
119 is_stale = _helpers.utcnow() >= (self.expiry - _helpers.REFRESH_THRESHOLD)
120 if is_stale:
121 return TokenState.STALE
122
123 return TokenState.FRESH
124
125 @property
126 def quota_project_id(self):
127 """Project to use for quota and billing purposes."""
128 return self._quota_project_id
129
130 @property
131 def universe_domain(self):
132 """The universe domain value."""
133 return self._universe_domain
134
135 def get_cred_info(self):
136 """The credential information JSON.
137
138 The credential information will be added to auth related error messages
139 by client library.
140
141 Returns:
142 Mapping[str, str]: The credential information JSON.
143 """
144 return None
145
146 @abc.abstractmethod
147 def refresh(self, request):
148 """Refreshes the access token.
149
150 Args:
151 request (google.auth.transport.Request): The object used to make
152 HTTP requests.
153
154 Raises:
155 google.auth.exceptions.RefreshError: If the credentials could
156 not be refreshed.
157 """
158 # pylint: disable=missing-raises-doc
159 # (pylint doesn't recognize that this is abstract)
160 raise NotImplementedError("Refresh must be implemented")
161
162 def _metric_header_for_usage(self):
163 """The x-goog-api-client header for token usage metric.
164
165 This header will be added to the API service requests in before_request
166 method. For example, "cred-type/sa-jwt" means service account self
167 signed jwt access token is used in the API service request
168 authorization header. Children credentials classes need to override
169 this method to provide the header value, if the token usage metric is
170 needed.
171
172 Returns:
173 str: The x-goog-api-client header value.
174 """
175 return None
176
177 def apply(self, headers, token=None):
178 """Apply the token to the authentication header.
179
180 Args:
181 headers (Mapping): The HTTP request headers.
182 token (Optional[str]): If specified, overrides the current access
183 token.
184 """
185 self._apply(headers, token)
186 if self.quota_project_id:
187 headers["x-goog-user-project"] = self.quota_project_id
188
189 def _blocking_refresh(self, request):
190 if not self.valid:
191 self.refresh(request)
192
193 def _non_blocking_refresh(self, request):
194 use_blocking_refresh_fallback = False
195
196 if self.token_state == TokenState.STALE:
197 use_blocking_refresh_fallback = not self._refresh_worker.start_refresh(
198 self, request
199 )
200
201 if self.token_state == TokenState.INVALID or use_blocking_refresh_fallback:
202 self.refresh(request)
203 # If the blocking refresh succeeds then we can clear the error info
204 # on the background refresh worker, and perform refreshes in a
205 # background thread.
206 self._refresh_worker.clear_error()
207
208 def before_request(self, request, method, url, headers):
209 """Performs credential-specific before request logic.
210
211 Refreshes the credentials if necessary, then calls :meth:`apply` to
212 apply the token to the authentication header.
213
214 Args:
215 request (google.auth.transport.Request): The object used to make
216 HTTP requests.
217 method (str): The request's HTTP method or the RPC method being
218 invoked.
219 url (str): The request's URI or the RPC service's URI.
220 headers (Mapping): The request's headers.
221 """
222 # pylint: disable=unused-argument
223 # (Subclasses may use these arguments to ascertain information about
224 # the http request.)
225 if self._use_non_blocking_refresh:
226 self._non_blocking_refresh(request)
227 else:
228 self._blocking_refresh(request)
229
230 metrics.add_metric_header(headers, self._metric_header_for_usage())
231 self.apply(headers)
232
233 def with_non_blocking_refresh(self):
234 self._use_non_blocking_refresh = True
235
236
237class CredentialsWithQuotaProject(Credentials):
238 """Abstract base for credentials supporting ``with_quota_project`` factory"""
239
240 def with_quota_project(self, quota_project_id):
241 """Returns a copy of these credentials with a modified quota project.
242
243 Args:
244 quota_project_id (str): The project to use for quota and
245 billing purposes
246
247 Returns:
248 google.auth.credentials.Credentials: A new credentials instance.
249 """
250 raise NotImplementedError("This credential does not support quota project.")
251
252 def with_quota_project_from_environment(self):
253 quota_from_env = os.environ.get(environment_vars.GOOGLE_CLOUD_QUOTA_PROJECT)
254 if quota_from_env:
255 return self.with_quota_project(quota_from_env)
256 return self
257
258
259class CredentialsWithTokenUri(Credentials):
260 """Abstract base for credentials supporting ``with_token_uri`` factory"""
261
262 def with_token_uri(self, token_uri):
263 """Returns a copy of these credentials with a modified token uri.
264
265 Args:
266 token_uri (str): The uri to use for fetching/exchanging tokens
267
268 Returns:
269 google.auth.credentials.Credentials: A new credentials instance.
270 """
271 raise NotImplementedError("This credential does not use token uri.")
272
273
274class CredentialsWithUniverseDomain(Credentials):
275 """Abstract base for credentials supporting ``with_universe_domain`` factory"""
276
277 def with_universe_domain(self, universe_domain):
278 """Returns a copy of these credentials with a modified universe domain.
279
280 Args:
281 universe_domain (str): The universe domain to use
282
283 Returns:
284 google.auth.credentials.Credentials: A new credentials instance.
285 """
286 raise NotImplementedError(
287 "This credential does not support with_universe_domain."
288 )
289
290
291class CredentialsWithTrustBoundary(Credentials):
292 """Abstract base for credentials supporting ``with_trust_boundary`` factory"""
293
294 @abc.abstractmethod
295 def _refresh_token(self, request):
296 """Refreshes the access token.
297
298 Args:
299 request (google.auth.transport.Request): The object used to make
300 HTTP requests.
301
302 Raises:
303 google.auth.exceptions.RefreshError: If the credentials could
304 not be refreshed.
305 """
306 raise NotImplementedError("_refresh_token must be implemented")
307
308 def with_trust_boundary(self, trust_boundary):
309 """Returns a copy of these credentials with a modified trust boundary.
310
311 Args:
312 trust_boundary Mapping[str, str]: The trust boundary to use for the
313 credential. This should be a map with a "locations" key that maps to
314 a list of GCP regions, and a "encodedLocations" key that maps to a
315 hex string.
316
317 Returns:
318 google.auth.credentials.Credentials: A new credentials instance.
319 """
320 raise NotImplementedError("This credential does not support trust boundaries.")
321
322 def _is_trust_boundary_lookup_required(self):
323 """Checks if a trust boundary lookup is required.
324
325 A lookup is required if the feature is enabled via an environment
326 variable, the universe domain is supported, and a no-op boundary
327 is not already cached.
328
329 Returns:
330 bool: True if a trust boundary lookup is required, False otherwise.
331 """
332 # 1. Check if the feature is enabled via environment variable.
333 if not _helpers.get_bool_from_env(
334 environment_vars.GOOGLE_AUTH_TRUST_BOUNDARY_ENABLED, default=False
335 ):
336 return False
337
338 # 2. Skip trust boundary flow for non-default universe domains.
339 if self.universe_domain != DEFAULT_UNIVERSE_DOMAIN:
340 return False
341
342 # 3. Do not trigger refresh if credential has a cached no-op trust boundary.
343 return not self._has_no_op_trust_boundary()
344
345 def _get_trust_boundary_header(self):
346 if self._trust_boundary is not None:
347 if self._has_no_op_trust_boundary():
348 # STS expects an empty string if the trust boundary value is no-op.
349 return {"x-allowed-locations": ""}
350 else:
351 return {"x-allowed-locations": self._trust_boundary["encodedLocations"]}
352 return {}
353
354 def apply(self, headers, token=None):
355 """Apply the token to the authentication header."""
356 super().apply(headers, token)
357 headers.update(self._get_trust_boundary_header())
358
359 def refresh(self, request):
360 """Refreshes the access token and the trust boundary.
361
362 This method calls the subclass's token refresh logic and then
363 refreshes the trust boundary if applicable.
364 """
365 self._refresh_token(request)
366 self._refresh_trust_boundary(request)
367
368 def _refresh_trust_boundary(self, request):
369 """Triggers a refresh of the trust boundary and updates the cache if necessary.
370
371 Args:
372 request (google.auth.transport.Request): The object used to make
373 HTTP requests.
374
375 Raises:
376 google.auth.exceptions.RefreshError: If the trust boundary could
377 not be refreshed and no cached value is available.
378 """
379 if not self._is_trust_boundary_lookup_required():
380 return
381 try:
382 self._trust_boundary = self._lookup_trust_boundary(request)
383 except exceptions.RefreshError as error:
384 # If the call to the lookup API failed, check if there is a trust boundary
385 # already cached. If there is, do nothing. If not, then throw the error.
386 if self._trust_boundary is None:
387 raise error
388 if _helpers.is_logging_enabled(_LOGGER):
389 _LOGGER.debug(
390 "Using cached trust boundary due to refresh error: %s", error
391 )
392 return
393
394 def _lookup_trust_boundary(self, request):
395 """Calls the trust boundary lookup API to refresh the trust boundary cache.
396
397 Args:
398 request (google.auth.transport.Request): The object used to make
399 HTTP requests.
400
401 Returns:
402 trust_boundary (dict): The trust boundary object returned by the lookup API.
403
404 Raises:
405 google.auth.exceptions.RefreshError: If the trust boundary could not be
406 retrieved.
407 """
408 from google.oauth2 import _client
409
410 url = self._build_trust_boundary_lookup_url()
411 if not url:
412 raise exceptions.InvalidValue("Failed to build trust boundary lookup URL.")
413
414 headers = {}
415 self._apply(headers)
416 headers.update(self._get_trust_boundary_header())
417 return _client._lookup_trust_boundary(request, url, headers=headers)
418
419 @abc.abstractmethod
420 def _build_trust_boundary_lookup_url(self):
421 """
422 Builds and returns the URL for the trust boundary lookup API.
423
424 This method should be implemented by subclasses to provide the
425 specific URL based on the credential type and its properties.
426
427 Returns:
428 str: The URL for the trust boundary lookup endpoint, or None
429 if lookup should be skipped (e.g., for non-applicable universe domains).
430 """
431 raise NotImplementedError(
432 "_build_trust_boundary_lookup_url must be implemented"
433 )
434
435 def _has_no_op_trust_boundary(self):
436 # A no-op trust boundary is indicated by encodedLocations being "0x0".
437 # The "locations" list may or may not be present as an empty list.
438 if self._trust_boundary is None:
439 return False
440 return (
441 self._trust_boundary.get("encodedLocations")
442 == NO_OP_TRUST_BOUNDARY_ENCODED_LOCATIONS
443 )
444
445
446class AnonymousCredentials(Credentials):
447 """Credentials that do not provide any authentication information.
448
449 These are useful in the case of services that support anonymous access or
450 local service emulators that do not use credentials.
451 """
452
453 @property
454 def expired(self):
455 """Returns `False`, anonymous credentials never expire."""
456 return False
457
458 @property
459 def valid(self):
460 """Returns `True`, anonymous credentials are always valid."""
461 return True
462
463 def refresh(self, request):
464 """Raises :class:``InvalidOperation``, anonymous credentials cannot be
465 refreshed."""
466 raise exceptions.InvalidOperation("Anonymous credentials cannot be refreshed.")
467
468 def apply(self, headers, token=None):
469 """Anonymous credentials do nothing to the request.
470
471 The optional ``token`` argument is not supported.
472
473 Raises:
474 google.auth.exceptions.InvalidValue: If a token was specified.
475 """
476 if token is not None:
477 raise exceptions.InvalidValue("Anonymous credentials don't support tokens.")
478
479 def before_request(self, request, method, url, headers):
480 """Anonymous credentials do nothing to the request."""
481
482
483class ReadOnlyScoped(metaclass=abc.ABCMeta):
484 """Interface for credentials whose scopes can be queried.
485
486 OAuth 2.0-based credentials allow limiting access using scopes as described
487 in `RFC6749 Section 3.3`_.
488 If a credential class implements this interface then the credentials either
489 use scopes in their implementation.
490
491 Some credentials require scopes in order to obtain a token. You can check
492 if scoping is necessary with :attr:`requires_scopes`::
493
494 if credentials.requires_scopes:
495 # Scoping is required.
496 credentials = credentials.with_scopes(scopes=['one', 'two'])
497
498 Credentials that require scopes must either be constructed with scopes::
499
500 credentials = SomeScopedCredentials(scopes=['one', 'two'])
501
502 Or must copy an existing instance using :meth:`with_scopes`::
503
504 scoped_credentials = credentials.with_scopes(scopes=['one', 'two'])
505
506 Some credentials have scopes but do not allow or require scopes to be set,
507 these credentials can be used as-is.
508
509 .. _RFC6749 Section 3.3: https://tools.ietf.org/html/rfc6749#section-3.3
510 """
511
512 def __init__(self):
513 super(ReadOnlyScoped, self).__init__()
514 self._scopes = None
515 self._default_scopes = None
516
517 @property
518 def scopes(self):
519 """Sequence[str]: the credentials' current set of scopes."""
520 return self._scopes
521
522 @property
523 def default_scopes(self):
524 """Sequence[str]: the credentials' current set of default scopes."""
525 return self._default_scopes
526
527 @abc.abstractproperty
528 def requires_scopes(self):
529 """True if these credentials require scopes to obtain an access token."""
530 return False
531
532 def has_scopes(self, scopes):
533 """Checks if the credentials have the given scopes.
534
535 .. warning: This method is not guaranteed to be accurate if the
536 credentials are :attr:`~Credentials.invalid`.
537
538 Args:
539 scopes (Sequence[str]): The list of scopes to check.
540
541 Returns:
542 bool: True if the credentials have the given scopes.
543 """
544 credential_scopes = (
545 self._scopes if self._scopes is not None else self._default_scopes
546 )
547 return set(scopes).issubset(set(credential_scopes or []))
548
549
550class Scoped(ReadOnlyScoped):
551 """Interface for credentials whose scopes can be replaced while copying.
552
553 OAuth 2.0-based credentials allow limiting access using scopes as described
554 in `RFC6749 Section 3.3`_.
555 If a credential class implements this interface then the credentials either
556 use scopes in their implementation.
557
558 Some credentials require scopes in order to obtain a token. You can check
559 if scoping is necessary with :attr:`requires_scopes`::
560
561 if credentials.requires_scopes:
562 # Scoping is required.
563 credentials = credentials.create_scoped(['one', 'two'])
564
565 Credentials that require scopes must either be constructed with scopes::
566
567 credentials = SomeScopedCredentials(scopes=['one', 'two'])
568
569 Or must copy an existing instance using :meth:`with_scopes`::
570
571 scoped_credentials = credentials.with_scopes(scopes=['one', 'two'])
572
573 Some credentials have scopes but do not allow or require scopes to be set,
574 these credentials can be used as-is.
575
576 .. _RFC6749 Section 3.3: https://tools.ietf.org/html/rfc6749#section-3.3
577 """
578
579 @abc.abstractmethod
580 def with_scopes(self, scopes, default_scopes=None):
581 """Create a copy of these credentials with the specified scopes.
582
583 Args:
584 scopes (Sequence[str]): The list of scopes to attach to the
585 current credentials.
586
587 Raises:
588 NotImplementedError: If the credentials' scopes can not be changed.
589 This can be avoided by checking :attr:`requires_scopes` before
590 calling this method.
591 """
592 raise NotImplementedError("This class does not require scoping.")
593
594
595def with_scopes_if_required(credentials, scopes, default_scopes=None):
596 """Creates a copy of the credentials with scopes if scoping is required.
597
598 This helper function is useful when you do not know (or care to know) the
599 specific type of credentials you are using (such as when you use
600 :func:`google.auth.default`). This function will call
601 :meth:`Scoped.with_scopes` if the credentials are scoped credentials and if
602 the credentials require scoping. Otherwise, it will return the credentials
603 as-is.
604
605 Args:
606 credentials (google.auth.credentials.Credentials): The credentials to
607 scope if necessary.
608 scopes (Sequence[str]): The list of scopes to use.
609 default_scopes (Sequence[str]): Default scopes passed by a
610 Google client library. Use 'scopes' for user-defined scopes.
611
612 Returns:
613 google.auth.credentials.Credentials: Either a new set of scoped
614 credentials, or the passed in credentials instance if no scoping
615 was required.
616 """
617 if isinstance(credentials, Scoped) and credentials.requires_scopes:
618 return credentials.with_scopes(scopes, default_scopes=default_scopes)
619 else:
620 return credentials
621
622
623class Signing(metaclass=abc.ABCMeta):
624 """Interface for credentials that can cryptographically sign messages."""
625
626 @abc.abstractmethod
627 def sign_bytes(self, message):
628 """Signs the given message.
629
630 Args:
631 message (bytes): The message to sign.
632
633 Returns:
634 bytes: The message's cryptographic signature.
635 """
636 # pylint: disable=missing-raises-doc,redundant-returns-doc
637 # (pylint doesn't recognize that this is abstract)
638 raise NotImplementedError("Sign bytes must be implemented.")
639
640 @abc.abstractproperty
641 def signer_email(self):
642 """Optional[str]: An email address that identifies the signer."""
643 # pylint: disable=missing-raises-doc
644 # (pylint doesn't recognize that this is abstract)
645 raise NotImplementedError("Signer email must be implemented.")
646
647 @abc.abstractproperty
648 def signer(self):
649 """google.auth.crypt.Signer: The signer used to sign bytes."""
650 # pylint: disable=missing-raises-doc
651 # (pylint doesn't recognize that this is abstract)
652 raise NotImplementedError("Signer must be implemented.")
653
654
655class TokenState(Enum):
656 """
657 Tracks the state of a token.
658 FRESH: The token is valid. It is not expired or close to expired, or the token has no expiry.
659 STALE: The token is close to expired, and should be refreshed. The token can be used normally.
660 INVALID: The token is expired or invalid. The token cannot be used for a normal operation.
661 """
662
663 FRESH = 1
664 STALE = 2
665 INVALID = 3