diff options
Diffstat (limited to 'oauthlib/oauth2/rfc6749/grant_types/authorization_code.py')
| -rw-r--r-- | oauthlib/oauth2/rfc6749/grant_types/authorization_code.py | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py b/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py index 850d70a..d56330a 100644 --- a/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py +++ b/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py @@ -5,6 +5,8 @@ oauthlib.oauth2.rfc6749.grant_types """ from __future__ import absolute_import, unicode_literals +import base64 +import hashlib import json import logging @@ -17,6 +19,52 @@ from .base import GrantTypeBase log = logging.getLogger(__name__) +def code_challenge_method_s256(verifier, challenge): + """ + If the "code_challenge_method" from `Section 4.3`_ was "S256", the + received "code_verifier" is hashed by SHA-256, base64url-encoded, and + then compared to the "code_challenge", i.e.: + + BASE64URL-ENCODE(SHA256(ASCII(code_verifier))) == code_challenge + + How to implement a base64url-encoding + function without padding, based upon the standard base64-encoding + function that uses padding. + + To be concrete, example C# code implementing these functions is shown + below. Similar code could be used in other languages. + + static string base64urlencode(byte [] arg) + { + string s = Convert.ToBase64String(arg); // Regular base64 encoder + s = s.Split('=')[0]; // Remove any trailing '='s + s = s.Replace('+', '-'); // 62nd char of encoding + s = s.Replace('/', '_'); // 63rd char of encoding + return s; + } + + In python urlsafe_b64encode is already replacing '+' and '/', but preserve + the trailing '='. So we have to remove it. + + .. _`Section 4.3`: https://tools.ietf.org/html/rfc7636#section-4.3 + """ + return base64.urlsafe_b64encode( + hashlib.sha256(verifier.encode()).digest() + ).decode().rstrip('=') == challenge + + +def code_challenge_method_plain(verifier, challenge): + """ + If the "code_challenge_method" from `Section 4.3`_ was "plain", they are + compared directly, i.e.: + + code_verifier == code_challenge. + + .. _`Section 4.3`: https://tools.ietf.org/html/rfc7636#section-4.3 + """ + return verifier == challenge + + class AuthorizationCodeGrant(GrantTypeBase): """`Authorization Code Grant`_ @@ -91,12 +139,28 @@ class AuthorizationCodeGrant(GrantTypeBase): step (C). If valid, the authorization server responds back with an access token and, optionally, a refresh token. + OAuth 2.0 public clients utilizing the Authorization Code Grant are + susceptible to the authorization code interception attack. + + A technique to mitigate against the threat through the use of Proof Key for Code + Exchange (PKCE, pronounced "pixy") is implemented in the current oauthlib + implementation. + .. _`Authorization Code Grant`: https://tools.ietf.org/html/rfc6749#section-4.1 + .. _`PKCE`: https://tools.ietf.org/html/rfc7636 """ default_response_mode = 'query' response_types = ['code'] + # This dict below is private because as RFC mention it: + # "S256" is Mandatory To Implement (MTI) on the server. + # + _code_challenge_methods = { + 'plain': code_challenge_method_plain, + 'S256': code_challenge_method_s256 + } + def create_authorization_code(self, request): """ Generates an authorization grant represented as a dictionary. @@ -351,6 +415,20 @@ class AuthorizationCodeGrant(GrantTypeBase): request.client_id, request.response_type) raise errors.UnauthorizedClientError(request=request) + # OPTIONAL. Validate PKCE request or reply with "error"/"invalid_request" + # https://tools.ietf.org/html/rfc6749#section-4.4.1 + if self.request_validator.is_pkce_required(request.client_id, request) is True: + if request.code_challenge is None: + raise errors.MissingCodeChallengeError(request=request) + + if request.code_challenge is not None: + # OPTIONAL, defaults to "plain" if not present in the request. + if request.code_challenge_method is None: + request.code_challenge_method = "plain" + + if request.code_challenge_method not in self._code_challenge_methods: + raise errors.UnsupportedCodeChallengeMethodError(request=request) + # OPTIONAL. The scope of the access request as described by Section 3.3 # https://tools.ietf.org/html/rfc6749#section-3.3 self.validate_scopes(request) @@ -423,6 +501,33 @@ class AuthorizationCodeGrant(GrantTypeBase): request.client_id, request.client, request.scopes) raise errors.InvalidGrantError(request=request) + # OPTIONAL. Validate PKCE code_verifier + challenge = self.request_validator.get_code_challenge(request.code, request) + + if challenge is not None: + if request.code_verifier is None: + raise errors.MissingCodeVerifierError(request=request) + + challenge_method = self.request_validator.get_code_challenge_method(request.code, request) + if challenge_method is None: + raise errors.InvalidGrantError(request=request, description="Challenge method not found") + + if challenge_method not in self._code_challenge_methods: + raise errors.ServerError( + description="code_challenge_method {} is not supported.".format(challenge_method), + request=request + ) + + if not self.validate_code_challenge(challenge, + challenge_method, + request.code_verifier): + log.debug('request provided a invalid code_verifier.') + raise errors.InvalidGrantError(request=request) + elif self.request_validator.is_pkce_required(request.client_id, request) is True: + if request.code_verifier is None: + raise errors.MissingCodeVerifierError(request=request) + raise errors.InvalidGrantError(request=request, description="Challenge not found") + for attr in ('user', 'scopes'): if getattr(request, attr, None) is None: log.debug('request.%s was not set on code validation.', attr) @@ -450,3 +555,8 @@ class AuthorizationCodeGrant(GrantTypeBase): for validator in self.custom_validators.post_token: validator(request) + + def validate_code_challenge(self, challenge, challenge_method, verifier): + if challenge_method in self._code_challenge_methods: + return self._code_challenge_methods[challenge_method](verifier, challenge) + raise NotImplementedError('Unknown challenge_method %s' % challenge_method) |