8000 [3.11] gh-123067: Fix quadratic complexity in parsing "-quoted cookie values with backslashes (GH-123075) by miss-islington · Pull Request #123105 · python/cpython · GitHub
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[3.11] gh-123067: Fix quadratic complexity in parsing "-quoted cookie values with backslashes (GH-123075) #123105

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merged 1 commit into from
Sep 4, 2024
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[3.11] gh-123067: Fix quadratic complexity in parsing "-quoted cookie values with backslashes (GH-123075) #123105

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gh-123067: Fix quadratic complexity in parsing "-quoted cookie values… 
… with backslashes (GH-123075)

This fixes CVE-2024-7592.
(cherry picked from commit 44e4583)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
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@serhiy-storchaka @miss-islington
serhiy-storchaka authored and miss-islington committed Aug 17, 2024
commit dcfd909737995b948b99810a28205835a6c2848e
34 changes: 8 additions & 26 deletions Lib/http/cookies.py
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Original file line number Diff line number Diff line change
Expand Up @@ -184,8 +184,13 @@ def _quote(str):
return '"' + str.translate(_Translator) + '"'


_OctalPatt = re.compile(r"\\[0-3][0-7][0-7]")
_QuotePatt = re.compile(r"[\\].")
_unquote_sub = re.compile(r'\\(?:([0-3][0-7][0-7])|(.))').sub

def _unquote_replace(m):
if m[1]:
return chr(int(m[1], 8))
else:
return m[2]

def _unquote(str):
# If there aren't any doublequotes,
Expand All @@ -205,30 +210,7 @@ def _unquote(str):
# \012 --> \n
# \" --> "
#
i = 0
n = len(str)
res = []
while 0 <= i < n:
o_match = _OctalPatt.search(str, i)
q_match = _QuotePatt.search(str, i)
if not o_match and not q_match: # Neither matched
res.append(str[i:])
break
# else:
j = k = -1
if o_match:
j = o_match.start(0)
if q_match:
k = q_match.start(0)
if q_match and (not o_match or k < j): # QuotePatt matched
res.append(str[i:k])
res.append(str[k+1])
i = k + 2
else: # OctalPatt matched
res.append(str[i:j])
res.append(chr(int(str[j+1:j+4], 8)))
i = j + 4
return _nulljoin(res)
return _unquote_sub(_unquote_replace, str)

# The _getdate() routine is used to set the expiration time in the cookie's HTTP
# header. By default, _getdate() returns the current time in the appropriate
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38 changes: 38 additions & 0 deletions Lib/test/test_http_cookies.py
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Expand Up @@ -5,6 +5,7 @@
import doctest
from http import cookies
import pickle
from test import support


class CookieTests(unittest.TestCase):
Expand Down Expand Up @@ -58,6 +59,43 @@ def test_basic(self):
for k, v in sorted(case['dict'].items()):
self.assertEqual(C[k].value, v)

def test_unquote(self):
cases = [
(r'a="b=\""', 'b="'),
(r'a="b=\\"', 'b=\\'),
(r'a="b=\="', 'b=='),
(r'a="b=\n"', 'b=n'),
(r'a="b=\042"', 'b="'),
(r'a="b=\134"', 'b=\\'),
(r'a="b=\377"', 'b=\xff'),
(r'a="b=\400"', 'b=400'),
(r'a="b=\42"', 'b=42'),
(r'a="b=\\042"', 'b=\\042'),
(r'a="b=\\134"', 'b=\\134'),
(r'a="b=\\\""', 'b=\\"'),
(r'a="b=\\\042"', 'b=\\"'),
(r'a="b=\134\""', 'b=\\"'),
(r'a="b=\134\042"', 'b=\\"'),
]
for encoded, decoded in cases:
with self.subTest(encoded):
C = cookies.SimpleCookie()
C.load(encoded)
self.assertEqual(C['a'].value, decoded)

@support.requires_resource('cpu')
def test_unquote_large(self):
n = 10**6
for encoded in r'\\', r'\134':
with self.subTest(encoded):
data = 'a="b=' + encoded*n + ';"'
C = cookies.SimpleCookie()
C.load(data)
value = C['a'].value
self.assertEqual(value[:3], 'b=\\')
self.assertEqual(value[-2:], '\\;')
self.assertEqual(len(value), n + 3)

def test_load(self):
C = cookies.SimpleCookie()
C.load('Customer="WILE_E_COYOTE"; Version=1; Path=/acme')
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2024-08-16-19-13-21.gh-issue-123067.Nx9O4R.rst
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@@ -0,0 +1 @@
Fix quadratic complexity in parsing ``"``-quoted cookie values with backslashes by :mod:`http.cookies`.
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