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CVE-2023-6597-TempDir-cleaning-symlink.patch
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CVE-2023-6597-TempDir-cleaning-symlink.patch
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---
Lib/tempfile.py | 26 +-
Lib/test/test_tempfile.py | 117 +++++++++-
Misc/NEWS.d/next/Library/2022-12-01-16-57-44.gh-issue-91133.LKMVCV.rst | 2
3 files changed, 136 insertions(+), 9 deletions(-)
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -269,6 +269,22 @@ def _mkstemp_inner(dir, pre, suf, flags,
raise FileExistsError(_errno.EEXIST,
"No usable temporary file name found")
+def _dont_follow_symlinks(func, path, *args):
+ # Pass follow_symlinks=False, unless not supported on this platform.
+ if func in _os.supports_follow_symlinks:
+ func(path, *args, follow_symlinks=False)
+ elif _os.name == 'nt' or not _os.path.islink(path):
+ func(path, *args)
+
+def _resetperms(path):
+ try:
+ chflags = _os.chflags
+ except AttributeError:
+ pass
+ else:
+ _dont_follow_symlinks(chflags, path, 0)
+ _dont_follow_symlinks(_os.chmod, path, 0o700)
+
# User visible interfaces.
@@ -827,17 +843,11 @@ class TemporaryDirectory:
def _rmtree(cls, name, ignore_errors=False):
def onerror(func, path, exc_info):
if issubclass(exc_info[0], PermissionError):
- def resetperms(path):
- try:
- _os.chflags(path, 0)
- except AttributeError:
- pass
- _os.chmod(path, 0o700)
try:
if path != name:
- resetperms(_os.path.dirname(path))
- resetperms(path)
+ _resetperms(_os.path.dirname(path))
+ _resetperms(path)
try:
_os.unlink(path)
--- a/Lib/test/test_tempfile.py
+++ b/Lib/test/test_tempfile.py
@@ -1499,6 +1499,103 @@ class TestTemporaryDirectory(BaseTestCas
"were deleted")
d2.cleanup()
+ @os_helper.skip_unless_symlink
+ def test_cleanup_with_symlink_modes(self):
+ # cleanup() should not follow symlinks when fixing mode bits (#91133)
+ with self.do_create(recurse=0) as d2:
+ file1 = os.path.join(d2, 'file1')
+ open(file1, 'wb').close()
+ dir1 = os.path.join(d2, 'dir1')
+ os.mkdir(dir1)
+ for mode in range(8):
+ mode <<= 6
+ with self.subTest(mode=format(mode, '03o')):
+ def test(target, target_is_directory):
+ d1 = self.do_create(recurse=0)
+ symlink = os.path.join(d1.name, 'symlink')
+ os.symlink(target, symlink,
+ target_is_directory=target_is_directory)
+ try:
+ os.chmod(symlink, mode, follow_symlinks=False)
+ except NotImplementedError:
+ pass
+ try:
+ os.chmod(symlink, mode)
+ except FileNotFoundError:
+ pass
+ os.chmod(d1.name, mode)
+ d1.cleanup()
+ self.assertFalse(os.path.exists(d1.name))
+
+ with self.subTest('nonexisting file'):
+ test('nonexisting', target_is_directory=False)
+ with self.subTest('nonexisting dir'):
+ test('nonexisting', target_is_directory=True)
+
+ with self.subTest('existing file'):
+ os.chmod(file1, mode)
+ old_mode = os.stat(file1).st_mode
+ test(file1, target_is_directory=False)
+ new_mode = os.stat(file1).st_mode
+ self.assertEqual(new_mode, old_mode,
+ '%03o != %03o' % (new_mode, old_mode))
+
+ with self.subTest('existing dir'):
+ os.chmod(dir1, mode)
+ old_mode = os.stat(dir1).st_mode
+ test(dir1, target_is_directory=True)
+ new_mode = os.stat(dir1).st_mode
+ self.assertEqual(new_mode, old_mode,
+ '%03o != %03o' % (new_mode, old_mode))
+
+ @unittest.skipUnless(hasattr(os, 'chflags'), 'requires os.chflags')
+ @os_helper.skip_unless_symlink
+ def test_cleanup_with_symlink_flags(self):
+ # cleanup() should not follow symlinks when fixing flags (#91133)
+ flags = stat.UF_IMMUTABLE | stat.UF_NOUNLINK
+ self.check_flags(flags)
+
+ with self.do_create(recurse=0) as d2:
+ file1 = os.path.join(d2, 'file1')
+ open(file1, 'wb').close()
+ dir1 = os.path.join(d2, 'dir1')
+ os.mkdir(dir1)
+ def test(target, target_is_directory):
+ d1 = self.do_create(recurse=0)
+ symlink = os.path.join(d1.name, 'symlink')
+ os.symlink(target, symlink,
+ target_is_directory=target_is_directory)
+ try:
+ os.chflags(symlink, flags, follow_symlinks=False)
+ except NotImplementedError:
+ pass
+ try:
+ os.chflags(symlink, flags)
+ except FileNotFoundError:
+ pass
+ os.chflags(d1.name, flags)
+ d1.cleanup()
+ self.assertFalse(os.path.exists(d1.name))
+
+ with self.subTest('nonexisting file'):
+ test('nonexisting', target_is_directory=False)
+ with self.subTest('nonexisting dir'):
+ test('nonexisting', target_is_directory=True)
+
+ with self.subTest('existing file'):
+ os.chflags(file1, flags)
+ old_flags = os.stat(file1).st_flags
+ test(file1, target_is_directory=False)
+ new_flags = os.stat(file1).st_flags
+ self.assertEqual(new_flags, old_flags)
+
+ with self.subTest('existing dir'):
+ os.chflags(dir1, flags)
+ old_flags = os.stat(dir1).st_flags
+ test(dir1, target_is_directory=True)
+ new_flags = os.stat(dir1).st_flags
+ self.assertEqual(new_flags, old_flags)
+
@support.cpython_only
def test_del_on_collection(self):
# A TemporaryDirectory is deleted when garbage collected
@@ -1671,9 +1768,27 @@ class TestTemporaryDirectory(BaseTestCas
d.cleanup()
self.assertFalse(os.path.exists(d.name))
- @unittest.skipUnless(hasattr(os, 'chflags'), 'requires os.lchflags')
+ def check_flags(self, flags):
+ # skip the test if these flags are not supported (ex: FreeBSD 13)
+ filename = os_helper.TESTFN
+ try:
+ open(filename, "w").close()
+ try:
+ os.chflags(filename, flags)
+ except OSError as exc:
+ # "OSError: [Errno 45] Operation not supported"
+ self.skipTest(f"chflags() doesn't support flags "
+ f"{flags:#b}: {exc}")
+ else:
+ os.chflags(filename, 0)
+ finally:
+ support.unlink(filename)
+
+ @unittest.skipUnless(hasattr(os, 'chflags'), 'requires os.chflags')
def test_flags(self):
flags = stat.UF_IMMUTABLE | stat.UF_NOUNLINK
+ self.check_flags(flags)
+
d = self.do_create(recurse=3, dirs=2, files=2)
with d:
# Change files and directories flags recursively.
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-12-01-16-57-44.gh-issue-91133.LKMVCV.rst
@@ -0,0 +1,2 @@
+Fix a bug in :class:`tempfile.TemporaryDirectory` cleanup, which now no longer
+dereferences symlinks when working around file system permission errors.