Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/oauthlib/oauth1/rfc5849/request_validator.py: 54%
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1"""
2oauthlib.oauth1.rfc5849
3~~~~~~~~~~~~~~
5This module is an implementation of various logic needed
6for signing and checking OAuth 1.0 RFC 5849 requests.
7"""
8from . import SIGNATURE_METHODS, utils
11class RequestValidator:
13 """A validator/datastore interaction base class for OAuth 1 providers.
15 OAuth providers should inherit from RequestValidator and implement the
16 methods and properties outlined below. Further details are provided in the
17 documentation for each method and property.
19 Methods used to check the format of input parameters. Common tests include
20 length, character set, membership, range or pattern. These tests are
21 referred to as `whitelisting or blacklisting`_. Whitelisting is better
22 but blacklisting can be useful to spot malicious activity.
23 The following have methods a default implementation:
25 - check_client_key
26 - check_request_token
27 - check_access_token
28 - check_nonce
29 - check_verifier
30 - check_realms
32 The methods above default to whitelist input parameters, checking that they
33 are alphanumerical and between a minimum and maximum length. Rather than
34 overloading the methods a few properties can be used to configure these
35 methods.
37 * @safe_characters -> (character set)
38 * @client_key_length -> (min, max)
39 * @request_token_length -> (min, max)
40 * @access_token_length -> (min, max)
41 * @nonce_length -> (min, max)
42 * @verifier_length -> (min, max)
43 * @realms -> [list, of, realms]
45 Methods used to validate/invalidate input parameters. These checks usually
46 hit either persistent or temporary storage such as databases or the
47 filesystem. See each methods documentation for detailed usage.
48 The following methods must be implemented:
50 - validate_client_key
51 - validate_request_token
52 - validate_access_token
53 - validate_timestamp_and_nonce
54 - validate_redirect_uri
55 - validate_requested_realms
56 - validate_realms
57 - validate_verifier
58 - invalidate_request_token
60 Methods used to retrieve sensitive information from storage.
61 The following methods must be implemented:
63 - get_client_secret
64 - get_request_token_secret
65 - get_access_token_secret
66 - get_rsa_key
67 - get_realms
68 - get_default_realms
69 - get_redirect_uri
71 Methods used to save credentials.
72 The following methods must be implemented:
74 - save_request_token
75 - save_verifier
76 - save_access_token
78 Methods used to verify input parameters. This methods are used during
79 authorizing request token by user (AuthorizationEndpoint), to check if
80 parameters are valid. During token authorization request is not signed,
81 thus 'validation' methods can not be used. The following methods must be
82 implemented:
84 - verify_realms
85 - verify_request_token
87 To prevent timing attacks it is necessary to not exit early even if the
88 client key or resource owner key is invalid. Instead dummy values should
89 be used during the remaining verification process. It is very important
90 that the dummy client and token are valid input parameters to the methods
91 get_client_secret, get_rsa_key and get_(access/request)_token_secret and
92 that the running time of those methods when given a dummy value remain
93 equivalent to the running time when given a valid client/resource owner.
94 The following properties must be implemented:
96 * @dummy_client
97 * @dummy_request_token
98 * @dummy_access_token
100 Example implementations have been provided, note that the database used is
101 a simple dictionary and serves only an illustrative purpose. Use whichever
102 database suits your project and how to access it is entirely up to you.
103 The methods are introduced in an order which should make understanding
104 their use more straightforward and as such it could be worth reading what
105 follows in chronological order.
107 .. _`whitelisting or blacklisting`: https://www.schneier.com/blog/archives/2011/01/whitelisting_vs.html
108 """
110 def __init__(self):
111 pass
113 @property
114 def allowed_signature_methods(self):
115 return SIGNATURE_METHODS
117 @property
118 def safe_characters(self):
119 return set(utils.UNICODE_ASCII_CHARACTER_SET)
121 @property
122 def client_key_length(self):
123 return 20, 30
125 @property
126 def request_token_length(self):
127 return 20, 30
129 @property
130 def access_token_length(self):
131 return 20, 30
133 @property
134 def timestamp_lifetime(self):
135 return 600
137 @property
138 def nonce_length(self):
139 return 20, 30
141 @property
142 def verifier_length(self):
143 return 20, 30
145 @property
146 def realms(self):
147 return []
149 @property
150 def enforce_ssl(self):
151 return True
153 def check_client_key(self, client_key):
154 """Check that the client key only contains safe characters
155 and is no shorter than lower and no longer than upper.
156 """
157 lower, upper = self.client_key_length
158 return (set(client_key) <= self.safe_characters and
159 lower <= len(client_key) <= upper)
161 def check_request_token(self, request_token):
162 """Checks that the request token contains only safe characters
163 and is no shorter than lower and no longer than upper.
164 """
165 lower, upper = self.request_token_length
166 return (set(request_token) <= self.safe_characters and
167 lower <= len(request_token) <= upper)
169 def check_access_token(self, request_token):
170 """Checks that the token contains only safe characters
171 and is no shorter than lower and no longer than upper.
172 """
173 lower, upper = self.access_token_length
174 return (set(request_token) <= self.safe_characters and
175 lower <= len(request_token) <= upper)
177 def check_nonce(self, nonce):
178 """Checks that the nonce only contains only safe characters
179 and is no shorter than lower and no longer than upper.
180 """
181 lower, upper = self.nonce_length
182 return (set(nonce) <= self.safe_characters and
183 lower <= len(nonce) <= upper)
185 def check_verifier(self, verifier):
186 """Checks that the verifier contains only safe characters
187 and is no shorter than lower and no longer than upper.
188 """
189 lower, upper = self.verifier_length
190 return (set(verifier) <= self.safe_characters and
191 lower <= len(verifier) <= upper)
193 def check_realms(self, realms):
194 """Check that the realm is one of a set allowed realms."""
195 return all(r in self.realms for r in realms)
197 def _subclass_must_implement(self, fn):
198 """
199 Returns a NotImplementedError for a function that should be implemented.
200 :param fn: name of the function
201 """
202 m = "Missing function implementation in {}: {}".format(type(self), fn)
203 return NotImplementedError(m)
205 @property
206 def dummy_client(self):
207 """Dummy client used when an invalid client key is supplied.
209 :returns: The dummy client key string.
211 The dummy client should be associated with either a client secret,
212 a rsa key or both depending on which signature methods are supported.
213 Providers should make sure that
215 get_client_secret(dummy_client)
216 get_rsa_key(dummy_client)
218 return a valid secret or key for the dummy client.
220 This method is used by
222 * AccessTokenEndpoint
223 * RequestTokenEndpoint
224 * ResourceEndpoint
225 * SignatureOnlyEndpoint
226 """
227 raise self._subclass_must_implement("dummy_client")
229 @property
230 def dummy_request_token(self):
231 """Dummy request token used when an invalid token was supplied.
233 :returns: The dummy request token string.
235 The dummy request token should be associated with a request token
236 secret such that get_request_token_secret(.., dummy_request_token)
237 returns a valid secret.
239 This method is used by
241 * AccessTokenEndpoint
242 """
243 raise self._subclass_must_implement("dummy_request_token")
245 @property
246 def dummy_access_token(self):
247 """Dummy access token used when an invalid token was supplied.
249 :returns: The dummy access token string.
251 The dummy access token should be associated with an access token
252 secret such that get_access_token_secret(.., dummy_access_token)
253 returns a valid secret.
255 This method is used by
257 * ResourceEndpoint
258 """
259 raise self._subclass_must_implement("dummy_access_token")
261 def get_client_secret(self, client_key, request):
262 """Retrieves the client secret associated with the client key.
264 :param client_key: The client/consumer key.
265 :param request: OAuthlib request.
266 :type request: oauthlib.common.Request
267 :returns: The client secret as a string.
269 This method must allow the use of a dummy client_key value.
270 Fetching the secret using the dummy key must take the same amount of
271 time as fetching a secret for a valid client::
273 # Unlikely to be near constant time as it uses two database
274 # lookups for a valid client, and only one for an invalid.
275 from your_datastore import ClientSecret
276 if ClientSecret.has(client_key):
277 return ClientSecret.get(client_key)
278 else:
279 return 'dummy'
281 # Aim to mimic number of latency inducing operations no matter
282 # whether the client is valid or not.
283 from your_datastore import ClientSecret
284 return ClientSecret.get(client_key, 'dummy')
286 Note that the returned key must be in plaintext.
288 This method is used by
290 * AccessTokenEndpoint
291 * RequestTokenEndpoint
292 * ResourceEndpoint
293 * SignatureOnlyEndpoint
294 """
295 raise self._subclass_must_implement('get_client_secret')
297 def get_request_token_secret(self, client_key, token, request):
298 """Retrieves the shared secret associated with the request token.
300 :param client_key: The client/consumer key.
301 :param token: The request token string.
302 :param request: OAuthlib request.
303 :type request: oauthlib.common.Request
304 :returns: The token secret as a string.
306 This method must allow the use of a dummy values and the running time
307 must be roughly equivalent to that of the running time of valid values::
309 # Unlikely to be near constant time as it uses two database
310 # lookups for a valid client, and only one for an invalid.
311 from your_datastore import RequestTokenSecret
312 if RequestTokenSecret.has(client_key):
313 return RequestTokenSecret.get((client_key, request_token))
314 else:
315 return 'dummy'
317 # Aim to mimic number of latency inducing operations no matter
318 # whether the client is valid or not.
319 from your_datastore import RequestTokenSecret
320 return ClientSecret.get((client_key, request_token), 'dummy')
322 Note that the returned key must be in plaintext.
324 This method is used by
326 * AccessTokenEndpoint
327 """
328 raise self._subclass_must_implement('get_request_token_secret')
330 def get_access_token_secret(self, client_key, token, request):
331 """Retrieves the shared secret associated with the access token.
333 :param client_key: The client/consumer key.
334 :param token: The access token string.
335 :param request: OAuthlib request.
336 :type request: oauthlib.common.Request
337 :returns: The token secret as a string.
339 This method must allow the use of a dummy values and the running time
340 must be roughly equivalent to that of the running time of valid values::
342 # Unlikely to be near constant time as it uses two database
343 # lookups for a valid client, and only one for an invalid.
344 from your_datastore import AccessTokenSecret
345 if AccessTokenSecret.has(client_key):
346 return AccessTokenSecret.get((client_key, request_token))
347 else:
348 return 'dummy'
350 # Aim to mimic number of latency inducing operations no matter
351 # whether the client is valid or not.
352 from your_datastore import AccessTokenSecret
353 return ClientSecret.get((client_key, request_token), 'dummy')
355 Note that the returned key must be in plaintext.
357 This method is used by
359 * ResourceEndpoint
360 """
361 raise self._subclass_must_implement("get_access_token_secret")
363 def get_default_realms(self, client_key, request):
364 """Get the default realms for a client.
366 :param client_key: The client/consumer key.
367 :param request: OAuthlib request.
368 :type request: oauthlib.common.Request
369 :returns: The list of default realms associated with the client.
371 The list of default realms will be set during client registration and
372 is outside the scope of OAuthLib.
374 This method is used by
376 * RequestTokenEndpoint
377 """
378 raise self._subclass_must_implement("get_default_realms")
380 def get_realms(self, token, request):
381 """Get realms associated with a request token.
383 :param token: The request token string.
384 :param request: OAuthlib request.
385 :type request: oauthlib.common.Request
386 :returns: The list of realms associated with the request token.
388 This method is used by
390 * AuthorizationEndpoint
391 * AccessTokenEndpoint
392 """
393 raise self._subclass_must_implement("get_realms")
395 def get_redirect_uri(self, token, request):
396 """Get the redirect URI associated with a request token.
398 :param token: The request token string.
399 :param request: OAuthlib request.
400 :type request: oauthlib.common.Request
401 :returns: The redirect URI associated with the request token.
403 It may be desirable to return a custom URI if the redirect is set to "oob".
404 In this case, the user will be redirected to the returned URI and at that
405 endpoint the verifier can be displayed.
407 This method is used by
409 * AuthorizationEndpoint
410 """
411 raise self._subclass_must_implement("get_redirect_uri")
413 def get_rsa_key(self, client_key, request):
414 """Retrieves a previously stored client provided RSA key.
416 :param client_key: The client/consumer key.
417 :param request: OAuthlib request.
418 :type request: oauthlib.common.Request
419 :returns: The rsa public key as a string.
421 This method must allow the use of a dummy client_key value. Fetching
422 the rsa key using the dummy key must take the same amount of time
423 as fetching a key for a valid client. The dummy key must also be of
424 the same bit length as client keys.
426 Note that the key must be returned in plaintext.
428 This method is used by
430 * AccessTokenEndpoint
431 * RequestTokenEndpoint
432 * ResourceEndpoint
433 * SignatureOnlyEndpoint
434 """
435 raise self._subclass_must_implement("get_rsa_key")
437 def invalidate_request_token(self, client_key, request_token, request):
438 """Invalidates a used request token.
440 :param client_key: The client/consumer key.
441 :param request_token: The request token string.
442 :param request: OAuthlib request.
443 :type request: oauthlib.common.Request
444 :returns: None
446 Per `Section 2.3`_ of the spec:
448 "The server MUST (...) ensure that the temporary
449 credentials have not expired or been used before."
451 .. _`Section 2.3`: https://tools.ietf.org/html/rfc5849#section-2.3
453 This method should ensure that provided token won't validate anymore.
454 It can be simply removing RequestToken from storage or setting
455 specific flag that makes it invalid (note that such flag should be
456 also validated during request token validation).
458 This method is used by
460 * AccessTokenEndpoint
461 """
462 raise self._subclass_must_implement("invalidate_request_token")
464 def validate_client_key(self, client_key, request):
465 """Validates that supplied client key is a registered and valid client.
467 :param client_key: The client/consumer key.
468 :param request: OAuthlib request.
469 :type request: oauthlib.common.Request
470 :returns: True or False
472 Note that if the dummy client is supplied it should validate in same
473 or nearly the same amount of time as a valid one.
475 Ensure latency inducing tasks are mimiced even for dummy clients.
476 For example, use::
478 from your_datastore import Client
479 try:
480 return Client.exists(client_key, access_token)
481 except DoesNotExist:
482 return False
484 Rather than::
486 from your_datastore import Client
487 if access_token == self.dummy_access_token:
488 return False
489 else:
490 return Client.exists(client_key, access_token)
492 This method is used by
494 * AccessTokenEndpoint
495 * RequestTokenEndpoint
496 * ResourceEndpoint
497 * SignatureOnlyEndpoint
498 """
499 raise self._subclass_must_implement("validate_client_key")
501 def validate_request_token(self, client_key, token, request):
502 """Validates that supplied request token is registered and valid.
504 :param client_key: The client/consumer key.
505 :param token: The request token string.
506 :param request: OAuthlib request.
507 :type request: oauthlib.common.Request
508 :returns: True or False
510 Note that if the dummy request_token is supplied it should validate in
511 the same nearly the same amount of time as a valid one.
513 Ensure latency inducing tasks are mimiced even for dummy clients.
514 For example, use::
516 from your_datastore import RequestToken
517 try:
518 return RequestToken.exists(client_key, access_token)
519 except DoesNotExist:
520 return False
522 Rather than::
524 from your_datastore import RequestToken
525 if access_token == self.dummy_access_token:
526 return False
527 else:
528 return RequestToken.exists(client_key, access_token)
530 This method is used by
532 * AccessTokenEndpoint
533 """
534 raise self._subclass_must_implement("validate_request_token")
536 def validate_access_token(self, client_key, token, request):
537 """Validates that supplied access token is registered and valid.
539 :param client_key: The client/consumer key.
540 :param token: The access token string.
541 :param request: OAuthlib request.
542 :type request: oauthlib.common.Request
543 :returns: True or False
545 Note that if the dummy access token is supplied it should validate in
546 the same or nearly the same amount of time as a valid one.
548 Ensure latency inducing tasks are mimiced even for dummy clients.
549 For example, use::
551 from your_datastore import AccessToken
552 try:
553 return AccessToken.exists(client_key, access_token)
554 except DoesNotExist:
555 return False
557 Rather than::
559 from your_datastore import AccessToken
560 if access_token == self.dummy_access_token:
561 return False
562 else:
563 return AccessToken.exists(client_key, access_token)
565 This method is used by
567 * ResourceEndpoint
568 """
569 raise self._subclass_must_implement("validate_access_token")
571 def validate_timestamp_and_nonce(self, client_key, timestamp, nonce,
572 request, request_token=None, access_token=None):
573 """Validates that the nonce has not been used before.
575 :param client_key: The client/consumer key.
576 :param timestamp: The ``oauth_timestamp`` parameter.
577 :param nonce: The ``oauth_nonce`` parameter.
578 :param request_token: Request token string, if any.
579 :param access_token: Access token string, if any.
580 :param request: OAuthlib request.
581 :type request: oauthlib.common.Request
582 :returns: True or False
584 Per `Section 3.3`_ of the spec.
586 "A nonce is a random string, uniquely generated by the client to allow
587 the server to verify that a request has never been made before and
588 helps prevent replay attacks when requests are made over a non-secure
589 channel. The nonce value MUST be unique across all requests with the
590 same timestamp, client credentials, and token combinations."
592 .. _`Section 3.3`: https://tools.ietf.org/html/rfc5849#section-3.3
594 One of the first validation checks that will be made is for the validity
595 of the nonce and timestamp, which are associated with a client key and
596 possibly a token. If invalid then immediately fail the request
597 by returning False. If the nonce/timestamp pair has been used before and
598 you may just have detected a replay attack. Therefore it is an essential
599 part of OAuth security that you not allow nonce/timestamp reuse.
600 Note that this validation check is done before checking the validity of
601 the client and token.::
603 nonces_and_timestamps_database = [
604 (u'foo', 1234567890, u'rannoMstrInghere', u'bar')
605 ]
607 def validate_timestamp_and_nonce(self, client_key, timestamp, nonce,
608 request_token=None, access_token=None):
610 return ((client_key, timestamp, nonce, request_token or access_token)
611 not in self.nonces_and_timestamps_database)
613 This method is used by
615 * AccessTokenEndpoint
616 * RequestTokenEndpoint
617 * ResourceEndpoint
618 * SignatureOnlyEndpoint
619 """
620 raise self._subclass_must_implement("validate_timestamp_and_nonce")
622 def validate_redirect_uri(self, client_key, redirect_uri, request):
623 """Validates the client supplied redirection URI.
625 :param client_key: The client/consumer key.
626 :param redirect_uri: The URI the client which to redirect back to after
627 authorization is successful.
628 :param request: OAuthlib request.
629 :type request: oauthlib.common.Request
630 :returns: True or False
632 It is highly recommended that OAuth providers require their clients
633 to register all redirection URIs prior to using them in requests and
634 register them as absolute URIs. See `CWE-601`_ for more information
635 about open redirection attacks.
637 By requiring registration of all redirection URIs it should be
638 straightforward for the provider to verify whether the supplied
639 redirect_uri is valid or not.
641 Alternatively per `Section 2.1`_ of the spec:
643 "If the client is unable to receive callbacks or a callback URI has
644 been established via other means, the parameter value MUST be set to
645 "oob" (case sensitive), to indicate an out-of-band configuration."
647 .. _`CWE-601`: http://cwe.mitre.org/top25/index.html#CWE-601
648 .. _`Section 2.1`: https://tools.ietf.org/html/rfc5849#section-2.1
650 This method is used by
652 * RequestTokenEndpoint
653 """
654 raise self._subclass_must_implement("validate_redirect_uri")
656 def validate_requested_realms(self, client_key, realms, request):
657 """Validates that the client may request access to the realm.
659 :param client_key: The client/consumer key.
660 :param realms: The list of realms that client is requesting access to.
661 :param request: OAuthlib request.
662 :type request: oauthlib.common.Request
663 :returns: True or False
665 This method is invoked when obtaining a request token and should
666 tie a realm to the request token and after user authorization
667 this realm restriction should transfer to the access token.
669 This method is used by
671 * RequestTokenEndpoint
672 """
673 raise self._subclass_must_implement("validate_requested_realms")
675 def validate_realms(self, client_key, token, request, uri=None,
676 realms=None):
677 """Validates access to the request realm.
679 :param client_key: The client/consumer key.
680 :param token: A request token string.
681 :param request: OAuthlib request.
682 :type request: oauthlib.common.Request
683 :param uri: The URI the realms is protecting.
684 :param realms: A list of realms that must have been granted to
685 the access token.
686 :returns: True or False
688 How providers choose to use the realm parameter is outside the OAuth
689 specification but it is commonly used to restrict access to a subset
690 of protected resources such as "photos".
692 realms is a convenience parameter which can be used to provide
693 a per view method pre-defined list of allowed realms.
695 Can be as simple as::
697 from your_datastore import RequestToken
698 request_token = RequestToken.get(token, None)
700 if not request_token:
701 return False
702 return set(request_token.realms).issuperset(set(realms))
704 This method is used by
706 * ResourceEndpoint
707 """
708 raise self._subclass_must_implement("validate_realms")
710 def validate_verifier(self, client_key, token, verifier, request):
711 """Validates a verification code.
713 :param client_key: The client/consumer key.
714 :param token: A request token string.
715 :param verifier: The authorization verifier string.
716 :param request: OAuthlib request.
717 :type request: oauthlib.common.Request
718 :returns: True or False
720 OAuth providers issue a verification code to clients after the
721 resource owner authorizes access. This code is used by the client to
722 obtain token credentials and the provider must verify that the
723 verifier is valid and associated with the client as well as the
724 resource owner.
726 Verifier validation should be done in near constant time
727 (to avoid verifier enumeration). To achieve this we need a
728 constant time string comparison which is provided by OAuthLib
729 in ``oauthlib.common.safe_string_equals``::
731 from your_datastore import Verifier
732 correct_verifier = Verifier.get(client_key, request_token)
733 from oauthlib.common import safe_string_equals
734 return safe_string_equals(verifier, correct_verifier)
736 This method is used by
738 * AccessTokenEndpoint
739 """
740 raise self._subclass_must_implement("validate_verifier")
742 def verify_request_token(self, token, request):
743 """Verify that the given OAuth1 request token is valid.
745 :param token: A request token string.
746 :param request: OAuthlib request.
747 :type request: oauthlib.common.Request
748 :returns: True or False
750 This method is used only in AuthorizationEndpoint to check whether the
751 oauth_token given in the authorization URL is valid or not.
752 This request is not signed and thus similar ``validate_request_token``
753 method can not be used.
755 This method is used by
757 * AuthorizationEndpoint
758 """
759 raise self._subclass_must_implement("verify_request_token")
761 def verify_realms(self, token, realms, request):
762 """Verify authorized realms to see if they match those given to token.
764 :param token: An access token string.
765 :param realms: A list of realms the client attempts to access.
766 :param request: OAuthlib request.
767 :type request: oauthlib.common.Request
768 :returns: True or False
770 This prevents the list of authorized realms sent by the client during
771 the authorization step to be altered to include realms outside what
772 was bound with the request token.
774 Can be as simple as::
776 valid_realms = self.get_realms(token)
777 return all((r in valid_realms for r in realms))
779 This method is used by
781 * AuthorizationEndpoint
782 """
783 raise self._subclass_must_implement("verify_realms")
785 def save_access_token(self, token, request):
786 """Save an OAuth1 access token.
788 :param token: A dict with token credentials.
789 :param request: OAuthlib request.
790 :type request: oauthlib.common.Request
792 The token dictionary will at minimum include
794 * ``oauth_token`` the access token string.
795 * ``oauth_token_secret`` the token specific secret used in signing.
796 * ``oauth_authorized_realms`` a space separated list of realms.
798 Client key can be obtained from ``request.client_key``.
800 The list of realms (not joined string) can be obtained from
801 ``request.realm``.
803 This method is used by
805 * AccessTokenEndpoint
806 """
807 raise self._subclass_must_implement("save_access_token")
809 def save_request_token(self, token, request):
810 """Save an OAuth1 request token.
812 :param token: A dict with token credentials.
813 :param request: OAuthlib request.
814 :type request: oauthlib.common.Request
816 The token dictionary will at minimum include
818 * ``oauth_token`` the request token string.
819 * ``oauth_token_secret`` the token specific secret used in signing.
820 * ``oauth_callback_confirmed`` the string ``true``.
822 Client key can be obtained from ``request.client_key``.
824 This method is used by
826 * RequestTokenEndpoint
827 """
828 raise self._subclass_must_implement("save_request_token")
830 def save_verifier(self, token, verifier, request):
831 """Associate an authorization verifier with a request token.
833 :param token: A request token string.
834 :param verifier: A dictionary containing the oauth_verifier and
835 oauth_token
836 :param request: OAuthlib request.
837 :type request: oauthlib.common.Request
839 We need to associate verifiers with tokens for validation during the
840 access token request.
842 Note that unlike save_x_token token here is the ``oauth_token`` token
843 string from the request token saved previously.
845 This method is used by
847 * AuthorizationEndpoint
848 """
849 raise self._subclass_must_implement("save_verifier")