From 74664d3fe037a354e180e305135c6bab1747a6b0 Mon Sep 17 00:00:00 2001 From: Jonathan Huot Date: Sat, 11 Jul 2026 13:15:29 +0200 Subject: [PATCH] Improve PKCE code comparison --- CHANGELOG.rst | 3 ++- oauthlib/oauth2/rfc6749/grant_types/authorization_code.py | 8 +++++--- 2 files changed, 7 insertions(+), 4 deletions(-) diff --git a/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py b/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py index 6c4bfce4..1806cee8 100644 --- a/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py +++ b/oauthlib/oauth2/rfc6749/grant_types/authorization_code.py @@ -4,6 +4,7 @@ """ import base64 import hashlib +import hmac import json import logging @@ -44,9 +45,10 @@ def code_challenge_method_s256(verifier, challenge): .. _`Section 4.3`: https://tools.ietf.org/html/rfc7636#section-4.3 """ - return base64.urlsafe_b64encode( + expected = base64.urlsafe_b64encode( hashlib.sha256(verifier.encode()).digest() - ).decode().rstrip('=') == challenge + ).decode().rstrip('=') + return hmac.compare_digest(expected, challenge) def code_challenge_method_plain(verifier, challenge): @@ -58,7 +60,7 @@ def code_challenge_method_plain(verifier, challenge): .. _`Section 4.3`: https://tools.ietf.org/html/rfc7636#section-4.3 """ - return verifier == challenge + return hmac.compare_digest(verifier, challenge) class AuthorizationCodeGrant(GrantTypeBase):