File CVE-2025-6075-expandvars-perf-degrad.patch of Package python3.41872
From 8b8e68d3dc95f454f58fdd8aac10848facb1491d Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Fri, 31 Oct 2025 15:49:51 +0200
Subject: [PATCH 1/2] [3.9] gh-136065: Fix quadratic complexity in
os.path.expandvars() (GH-134952) (cherry picked from commit
f029e8db626ddc6e3a3beea4eff511a71aaceb5c)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>
Co-authored-by: Łukasz Langa <lukasz@langa.pl>
---
Lib/ntpath.py | 126 +++-------
Lib/posixpath.py | 43 +--
Lib/test/test_genericpath.py | 19 +
Lib/test/test_ntpath.py | 23 +
Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst | 1
5 files changed, 96 insertions(+), 116 deletions(-)
create mode 100644 Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst
Index: Python-3.6.15/Lib/ntpath.py
===================================================================
--- Python-3.6.15.orig/Lib/ntpath.py 2025-11-20 21:43:57.831558361 +0100
+++ Python-3.6.15/Lib/ntpath.py 2025-11-20 21:44:05.762396341 +0100
@@ -356,17 +356,23 @@
# XXX With COMMAND.COM you can use any characters in a variable name,
# XXX except '^|<>='.
+_varpattern = r"'[^']*'?|%(%|[^%]*%?)|\$(\$|[-\w]+|\{[^}]*\}?)"
+_varsub = None
+_varsubb = None
+
def expandvars(path):
"""Expand shell variables of the forms $var, ${var} and %var%.
Unknown variables are left unchanged."""
path = os.fspath(path)
+ global _varsub, _varsubb
if isinstance(path, bytes):
if b'$' not in path and b'%' not in path:
return path
- import string
- varchars = bytes(string.ascii_letters + string.digits + '_-', 'ascii')
- quote = b'\''
+ if not _varsubb:
+ import re
+ _varsubb = re.compile(_varpattern.encode(), re.ASCII).sub
+ sub = _varsubb
percent = b'%'
brace = b'{'
rbrace = b'}'
@@ -375,94 +381,44 @@
else:
if '$' not in path and '%' not in path:
return path
- import string
- varchars = string.ascii_letters + string.digits + '_-'
- quote = '\''
+ if not _varsub:
+ import re
+ _varsub = re.compile(_varpattern, re.ASCII).sub
+ sub = _varsub
percent = '%'
brace = '{'
rbrace = '}'
dollar = '$'
environ = os.environ
- res = path[:0]
- index = 0
- pathlen = len(path)
- while index < pathlen:
- c = path[index:index+1]
- if c == quote: # no expansion within single quotes
- path = path[index + 1:]
- pathlen = len(path)
- try:
- index = path.index(c)
- res += c + path[:index + 1]
- except ValueError:
- res += c + path
- index = pathlen - 1
- elif c == percent: # variable or '%'
- if path[index + 1:index + 2] == percent:
- res += c
- index += 1
- else:
- path = path[index+1:]
- pathlen = len(path)
- try:
- index = path.index(percent)
- except ValueError:
- res += percent + path
- index = pathlen - 1
- else:
- var = path[:index]
- try:
- if environ is None:
- value = os.fsencode(os.environ[os.fsdecode(var)])
- else:
- value = environ[var]
- except KeyError:
- value = percent + var + percent
- res += value
- elif c == dollar: # variable or '$$'
- if path[index + 1:index + 2] == dollar:
- res += c
- index += 1
- elif path[index + 1:index + 2] == brace:
- path = path[index+2:]
- pathlen = len(path)
- try:
- index = path.index(rbrace)
- except ValueError:
- res += dollar + brace + path
- index = pathlen - 1
- else:
- var = path[:index]
- try:
- if environ is None:
- value = os.fsencode(os.environ[os.fsdecode(var)])
- else:
- value = environ[var]
- except KeyError:
- value = dollar + brace + var + rbrace
- res += value
- else:
- var = path[:0]
- index += 1
- c = path[index:index + 1]
- while c and c in varchars:
- var += c
- index += 1
- c = path[index:index + 1]
- try:
- if environ is None:
- value = os.fsencode(os.environ[os.fsdecode(var)])
- else:
- value = environ[var]
- except KeyError:
- value = dollar + var
- res += value
- if c:
- index -= 1
+
+ def repl(m):
+ lastindex = m.lastindex
+ if lastindex is None:
+ return m[0]
+ name = m[lastindex]
+ if lastindex == 1:
+ if name == percent:
+ return name
+ if not name.endswith(percent):
+ return m[0]
+ name = name[:-1]
else:
- res += c
- index += 1
- return res
+ if name == dollar:
+ return name
+ if name.startswith(brace):
+ if not name.endswith(rbrace):
+ return m[0]
+ name = name[1:-1]
+
+ try:
+ if environ is None:
+ return os.fsencode(os.environ[os.fsdecode(name)])
+ else:
+ return environ[name]
+ except KeyError:
+ return m[0]
+
+ return sub(repl, path)
# Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A\B.
Index: Python-3.6.15/Lib/posixpath.py
===================================================================
--- Python-3.6.15.orig/Lib/posixpath.py 2025-11-20 21:44:05.728166488 +0100
+++ Python-3.6.15/Lib/posixpath.py 2025-11-20 21:44:05.762640972 +0100
@@ -279,42 +279,41 @@
# This expands the forms $variable and ${variable} only.
# Non-existent variables are left unchanged.
-_varprog = None
-_varprogb = None
+_varpattern = r'\$(\w+|\{[^}]*\}?)'
+_varsub = None
+_varsubb = None
def expandvars(path):
"""Expand shell variables of form $var and ${var}. Unknown variables
are left unchanged."""
path = os.fspath(path)
- global _varprog, _varprogb
+ global _varsub, _varsubb
if isinstance(path, bytes):
if b'$' not in path:
return path
- if not _varprogb:
+ if not _varsubb:
import re
- _varprogb = re.compile(br'\$(\w+|\{[^}]*\})', re.ASCII)
- search = _varprogb.search
+ _varsubb = re.compile(_varpattern.encode(), re.ASCII).sub
+ sub = _varsubb
start = b'{'
end = b'}'
environ = getattr(os, 'environb', None)
else:
if '$' not in path:
return path
- if not _varprog:
+ if not _varsub:
import re
- _varprog = re.compile(r'\$(\w+|\{[^}]*\})', re.ASCII)
- search = _varprog.search
+ _varsub = re.compile(_varpattern, re.ASCII).sub
+ sub = _varsub
start = '{'
end = '}'
environ = os.environ
- i = 0
- while True:
- m = search(path, i)
- if not m:
- break
- i, j = m.span(0)
- name = m.group(1)
- if name.startswith(start) and name.endswith(end):
+
+ def repl(m):
+ name = m[1]
+ if name.startswith(start):
+ if not name.endswith(end):
+ return m[0]
name = name[1:-1]
try:
if environ is None:
@@ -322,13 +321,11 @@
else:
value = environ[name]
except KeyError:
- i = j
+ return m[0]
else:
- tail = path[j:]
- path = path[:i] + value
- i = len(path)
- path += tail
- return path
+ return value
+
+ return sub(repl, path)
# Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B.
Index: Python-3.6.15/Lib/test/test_genericpath.py
===================================================================
--- Python-3.6.15.orig/Lib/test/test_genericpath.py 2025-11-20 21:43:59.816307517 +0100
+++ Python-3.6.15/Lib/test/test_genericpath.py 2025-11-20 21:44:05.763424227 +0100
@@ -9,7 +9,7 @@
import warnings
from test import support
from test.support.script_helper import assert_python_ok
-from test.support import FakePath
+from test.support import FakePath, EnvironmentVarGuard
def create_file(filename, data=b'foo'):
@@ -354,7 +354,7 @@
if self.pathmodule.__name__ == 'macpath':
self.skipTest('macpath.expandvars is a stub')
expandvars = self.pathmodule.expandvars
- with support.EnvironmentVarGuard() as env:
+ with EnvironmentVarGuard() as env:
env.clear()
env["foo"] = "bar"
env["{foo"] = "baz1"
@@ -390,7 +390,7 @@
expandvars = self.pathmodule.expandvars
def check(value, expected):
self.assertEqual(expandvars(value), expected)
- with support.EnvironmentVarGuard() as env:
+ with EnvironmentVarGuard() as env:
env.clear()
nonascii = support.FS_NONASCII
env['spam'] = nonascii
@@ -411,6 +411,19 @@
os.fsencode('$bar%s bar' % nonascii))
check(b'$spam}bar', os.fsencode('%s}bar' % nonascii))
+ @support.requires_resource('cpu')
+ def test_expandvars_large(self):
+ expandvars = self.pathmodule.expandvars
+ with EnvironmentVarGuard() as env:
+ env.clear()
+ env["A"] = "B"
+ n = 100_000
+ self.assertEqual(expandvars('$A'*n), 'B'*n)
+ self.assertEqual(expandvars('${A}'*n), 'B'*n)
+ self.assertEqual(expandvars('$A!'*n), 'B!'*n)
+ self.assertEqual(expandvars('${A}A'*n), 'BA'*n)
+ self.assertEqual(expandvars('${'*10*n), '${'*10*n)
+
def test_abspath(self):
self.assertIn("foo", self.pathmodule.abspath("foo"))
with warnings.catch_warnings():
Index: Python-3.6.15/Lib/test/test_ntpath.py
===================================================================
--- Python-3.6.15.orig/Lib/test/test_ntpath.py 2025-11-20 21:44:05.728753393 +0100
+++ Python-3.6.15/Lib/test/test_ntpath.py 2025-11-20 21:44:05.763531920 +0100
@@ -1,11 +1,10 @@
import ntpath
import os
-import subprocess
import sys
import unittest
import warnings
from ntpath import ALLOW_MISSING
-from test.support import TestFailed, FakePath
+from test.support import TestFailed, FakePath, EnvironmentVarGuard
from test import support, test_genericpath
from tempfile import TemporaryFile
@@ -216,7 +215,7 @@
tester("ntpath.normpath('\\\\?\\D:/XY\\Z')", r'\\?\D:/XY\Z')
def test_expandvars(self):
- with support.EnvironmentVarGuard() as env:
+ with EnvironmentVarGuard() as env:
env.clear()
env["foo"] = "bar"
env["{foo"] = "baz1"
@@ -245,7 +244,7 @@
def test_expandvars_nonascii(self):
def check(value, expected):
tester('ntpath.expandvars(%r)' % value, expected)
- with support.EnvironmentVarGuard() as env:
+ with EnvironmentVarGuard() as env:
env.clear()
nonascii = support.FS_NONASCII
env['spam'] = nonascii
@@ -261,10 +260,23 @@
check('%spam%bar', '%sbar' % nonascii)
check('%{}%bar'.format(nonascii), 'ham%sbar' % nonascii)
+ @support.requires_resource('cpu')
+ def test_expandvars_large(self):
+ expandvars = ntpath.expandvars
+ with EnvironmentVarGuard() as env:
+ env.clear()
+ env["A"] = "B"
+ n = 100_000
+ self.assertEqual(expandvars('%A%'*n), 'B'*n)
+ self.assertEqual(expandvars('%A%A'*n), 'BA'*n)
+ self.assertEqual(expandvars("''"*n + '%%'), "''"*n + '%')
+ self.assertEqual(expandvars("%%"*n), "%"*n)
+ self.assertEqual(expandvars("$$"*n), "$"*n)
+
def test_expanduser(self):
tester('ntpath.expanduser("test")', 'test')
- with support.EnvironmentVarGuard() as env:
+ with EnvironmentVarGuard() as env:
env.clear()
tester('ntpath.expanduser("~test")', '~test')
@@ -455,6 +467,7 @@
self.assertTrue(ntpath.ismount(b"\\\\localhost\\c$"))
self.assertTrue(ntpath.ismount(b"\\\\localhost\\c$\\"))
+
class NtCommonTest(test_genericpath.CommonTest, unittest.TestCase):
pathmodule = ntpath
attributes = ['relpath', 'splitunc']
Index: Python-3.6.15/Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ Python-3.6.15/Misc/NEWS.d/next/Security/2025-05-30-22-33-27.gh-issue-136065.bu337o.rst 2025-11-20 21:44:05.762962057 +0100
@@ -0,0 +1 @@
+Fix quadratic complexity in :func:`os.path.expandvars`.
