From f5d16483f3abfd33e301fb5c2005b80bd6d05aaf Mon Sep 17 00:00:00 2001
From: Michael Manfre <mike@manfre.net>
Date: Fri, 14 Jun 2024 22:12:58 -0400
Subject: [PATCH] [5.1.x] Fixed CVE-2024-39329 -- Standarized timing of
verify_password() when checking unusuable passwords.
Refs #20760.
Thanks Michael Manfre for the fix and to Adam Johnson for the review.
---
django/contrib/auth/hashers.py | 10 ++++++++--
docs/releases/4.2.14.txt | 7 +++++++
docs/releases/5.0.7.txt | 7 +++++++
tests/auth_tests/test_hashers.py | 32 ++++++++++++++++++++++++++++++++
4 files changed, 54 insertions(+), 2 deletions(-)
diff --git a/django/contrib/auth/hashers.py b/django/contrib/auth/hashers.py
index b539747561..4c22c20795 100644
--- a/django/contrib/auth/hashers.py
+++ b/django/contrib/auth/hashers.py
@@ -39,14 +39,20 @@ def verify_password(password, encoded, preferred="default"):
three part encoded digest, and the second whether to regenerate the
password.
"""
- if password is None or not is_password_usable(encoded):
- return False, False
+ fake_runtime = password is None or not is_password_usable(encoded)
preferred = get_hasher(preferred)
try:
hasher = identify_hasher(encoded)
except ValueError:
# encoded is gibberish or uses a hasher that's no longer installed.
+ fake_runtime = True
+
+ if fake_runtime:
+ # Run the default password hasher once to reduce the timing difference
+ # between an existing user with an unusable password and a nonexistent
+ # user or missing hasher (similar to #20760).
+ make_password(get_random_string(UNUSABLE_PASSWORD_SUFFIX_LENGTH))
return False, False
hasher_changed = hasher.algorithm != preferred.algorithm
diff --git a/docs/releases/4.2.14.txt b/docs/releases/4.2.14.txt
index f32c0cf8d4..556cff4437 100644
--- a/docs/releases/4.2.14.txt
+++ b/docs/releases/4.2.14.txt
@@ -13,3 +13,10 @@ CVE-2024-38875: Potential denial-of-service vulnerability in ``django.utils.html
:tfilter:`urlize` and :tfilter:`urlizetrunc` were subject to a potential
denial-of-service attack via certain inputs with a very large number of
brackets.
+
+CVE-2024-39329: Username enumeration through timing difference for users with unusable passwords
+================================================================================================
+
+The :meth:`~django.contrib.auth.backends.ModelBackend.authenticate()` method
+allowed remote attackers to enumerate users via a timing attack involving login
+requests for users with unusable passwords.
diff --git a/docs/releases/5.0.7.txt b/docs/releases/5.0.7.txt
index f25bc1f37d..53efe3766b 100644
--- a/docs/releases/5.0.7.txt
+++ b/docs/releases/5.0.7.txt
@@ -14,6 +14,13 @@ CVE-2024-38875: Potential denial-of-service vulnerability in ``django.utils.html
denial-of-service attack via certain inputs with a very large number of
brackets.
+CVE-2024-39329: Username enumeration through timing difference for users with unusable passwords
+================================================================================================
+
+The :meth:`~django.contrib.auth.backends.ModelBackend.authenticate()` method
+allowed remote attackers to enumerate users via a timing attack involving login
+requests for users with unusable passwords.
+
Bugfixes
========
diff --git a/tests/auth_tests/test_hashers.py b/tests/auth_tests/test_hashers.py
index bec298cc3a..ee7b3f8e47 100644
--- a/tests/auth_tests/test_hashers.py
+++ b/tests/auth_tests/test_hashers.py
@@ -451,6 +451,38 @@ class TestUtilsHashPass(SimpleTestCase):
check_password("wrong_password", encoded)
self.assertEqual(hasher.harden_runtime.call_count, 1)
+ def test_check_password_calls_make_password_to_fake_runtime(self):
+ hasher = get_hasher("default")
+ cases = [
+ (None, None, None), # no plain text password provided
+ ("foo", make_password(password=None), None), # unusable encoded
+ ("letmein", make_password(password="letmein"), ValueError), # valid encoded
+ ]
+ for password, encoded, hasher_side_effect in cases:
+ with (
+ self.subTest(encoded=encoded),
+ mock.patch(
+ "django.contrib.auth.hashers.identify_hasher",
+ side_effect=hasher_side_effect,
+ ) as mock_identify_hasher,
+ mock.patch(
+ "django.contrib.auth.hashers.make_password"
+ ) as mock_make_password,
+ mock.patch(
+ "django.contrib.auth.hashers.get_random_string",
+ side_effect=lambda size: "x" * size,
+ ),
+ mock.patch.object(hasher, "verify"),
+ ):
+ # Ensure make_password is called to standardize timing.
+ check_password(password, encoded)
+ self.assertEqual(hasher.verify.call_count, 0)
+ self.assertEqual(mock_identify_hasher.mock_calls, [mock.call(encoded)])
+ self.assertEqual(
+ mock_make_password.mock_calls,
+ [mock.call("x" * UNUSABLE_PASSWORD_SUFFIX_LENGTH)],
+ )
+
def test_encode_invalid_salt(self):
hasher_classes = [
MD5PasswordHasher,