From d2655d370586cb830e49acfb450f87598da60be8 Mon Sep 17 00:00:00 2001 From: Simo Sorce Date: Thu, 7 Dec 2023 12:49:07 -0500 Subject: [PATCH] Fix potential DoS issue with p2c header Unbounded p2c headers may be used to cause an application that accept PBES algorithms to spend alot of resources running PBKDF2 with a very high number of iterations. Clamp the default maximum to 16384 (double the default of 8192). An application that wants to use more iterations will have to chenge the jwa default max. Fixes CVE-2023-6681 Signed-off-by: Simo Sorce --- jwcrypto/jwa.py | 5 +++++ jwcrypto/tests.py | 12 ++++++++++++ 2 files changed, 17 insertions(+) diff --git a/jwcrypto/jwa.py b/jwcrypto/jwa.py index de7a79f..ca4568e 100644 --- a/jwcrypto/jwa.py +++ b/jwcrypto/jwa.py @@ -29,6 +29,8 @@ # Implements RFC 7518 - JSON Web Algorithms (JWA) +default_max_pbkdf2_iterations = 16384 + @six.add_metaclass(abc.ABCMeta) class JWAAlgorithm(object): @@ -588,6 +590,9 @@ def __init__(self): self.aeskwmap = {128: _A128KW, 192: _A192KW, 256: _A256KW} def _get_key(self, alg, key, p2s, p2c): + if p2c > default_max_pbkdf2_iterations: + raise ValueError('Invalid p2c value, too large') + if isinstance(key, bytes): plain = key else: