68 lines
2.3 KiB
Diff
68 lines
2.3 KiB
Diff
From d2655d370586cb830e49acfb450f87598da60be8 Mon Sep 17 00:00:00 2001
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From: Simo Sorce <simo@redhat.com>
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Date: Thu, 7 Dec 2023 12:49:07 -0500
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Subject: [PATCH] Fix potential DoS issue with p2c header
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Unbounded p2c headers may be used to cause an application that accept
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PBES algorithms to spend alot of resources running PBKDF2 with a very
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high number of iterations.
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Clamp the default maximum to 16384 (double the default of 8192).
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An application that wants to use more iterations will have to chenge the
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jwa default max.
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Fixes CVE-2023-6681
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Signed-off-by: Simo Sorce <simo@redhat.com>
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---
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jwcrypto/jwa.py | 5 +++++
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jwcrypto/tests.py | 12 ++++++++++++
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2 files changed, 17 insertions(+)
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diff --git a/jwcrypto/jwa.py b/jwcrypto/jwa.py
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index de7a79f..ca4568e 100644
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--- a/jwcrypto/jwa.py
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+++ b/jwcrypto/jwa.py
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@@ -28,6 +28,8 @@
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# Implements RFC 7518 - JSON Web Algorithms (JWA)
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+default_max_pbkdf2_iterations = 16384
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+
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class JWAAlgorithm(metaclass=ABCMeta):
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@@ -588,6 +590,9 @@ def __init__(self):
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self.aeskwmap = {128: _A128KW, 192: _A192KW, 256: _A256KW}
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def _get_key(self, alg, key, p2s, p2c):
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+ if p2c > default_max_pbkdf2_iterations:
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+ raise ValueError('Invalid p2c value, too large')
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+
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if not isinstance(key, JWK):
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# backwards compatibility for old interface
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if isinstance(key, bytes):
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diff --git a/jwcrypto/tests.py b/jwcrypto/tests.py
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index 6069fab..bb2ff10 100644
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--- a/jwcrypto/tests.py
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+++ b/jwcrypto/tests.py
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@@ -2099,6 +2099,18 @@ def test_pbes2_hs256_aeskw_custom_params(self):
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key = jwk.JWK.from_password('password')
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self.assertRaises(ValueError, enc.add_recipient, key)
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+ # Test p2c iteration checks
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+ maxiter = jwa.default_max_pbkdf2_iterations
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+ p2cenc = jwe.JWE(plaintext='plain',
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+ protected={"alg": "PBES2-HS256+A128KW",
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+ "enc": "A256CBC-HS512",
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+ "p2c": maxiter + 1,
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+ "p2s": base64url_encode("A" * 16)})
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+ with self.assertRaisesRegex(ValueError, 'too large'):
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+ p2cenc.add_recipient(key)
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+ jwa.default_max_pbkdf2_iterations += 2
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+ p2cenc.add_recipient(key)
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+
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class JWATests(unittest.TestCase):
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def test_jwa_create(self):
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