security-and-privacy/mat2
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Add some verification for "dangerous" tarfiles

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This commit is contained in:
jvoisin 2019-04-28 19:25:45 +02:00
parent a7ebb587e1
commit 9516990693
2 changed files with 172 additions and 1 deletions
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53
libmat2/archive.py
View File

@ -15,7 +15,7 @@ from . import abstract, UnknownMemberPolicy, parser_factory
assert Set
assert Pattern
# pylint: disable=not-callable,assignment-from-no-return
# pylint: disable=not-callable,assignment-from-no-return,too-many-branches
# An ArchiveClass is a class representing an archive,
# while an ArchiveMember is a class representing an element
@ -238,6 +238,57 @@ class TarParser(ArchiveBasedAbstractParser):
def is_archive_valid(self):
if tarfile.is_tarfile(self.filename) is False:
raise ValueError
self.__check_tarfile_safety()
def __check_tarfile_safety(self):
"""Checks if the tarfile doesn't have any "suspicious" members.
This is a rewrite of this patch: https://bugs.python.org/file47826/safetarfile-4.diff
inspired by this bug from 2014: https://bugs.python.org/issue21109
because Python's stdlib doesn't provide a way to "safely" extract
things from a tar file.
"""
names = set()
with tarfile.open(self.filename) as f:
members = f.getmembers()
for member in members:
name = member.name
if os.path.isabs(name):
raise ValueError("The archive %s contains a file with an " \
"absolute path: %s" % (self.filename, name))
elif os.path.normpath(name).startswith('../') or '/../' in name:
raise ValueError("The archive %s contains a file with an " \
"path traversal attack: %s" % (self.filename, name))
if name in names:
raise ValueError("The archive %s contains two times the same " \
"file: %s" % (self.filename, name))
else:
names.add(name)
if member.isfile():
if member.mode & stat.S_ISUID:
raise ValueError("The archive %s contains a setuid file: %s" % \
(self.filename, name))
elif member.mode & stat.S_ISGID:
raise ValueError("The archive %s contains a setgid file: %s" % \
(self.filename, name))
elif member.issym():
linkname = member.linkname
if os.path.normpath(linkname).startswith('..'):
raise ValueError('The archive %s contains a symlink pointing' \
'outside of the archive via a path traversal: %s -> %s' % \
(self.filename, name, linkname))
if os.path.isabs(linkname):
raise ValueError('The archive %s contains a symlink pointing' \
'outside of the archive: %s -> %s' % \
(self.filename, name, linkname))
elif member.isdev():
raise ValueError("The archive %s contains a non-regular " \
"file: %s" % (self.filename, name))
elif member.islnk():
raise ValueError("The archive %s contains a hardlink: %s" \
% (self.filename, name))
@staticmethod
def _clean_member(member: ArchiveMember) -> ArchiveMember:

120
tests/test_corrupted_files.py
View File

@ -1,6 +1,7 @@
#!/usr/bin/env python3
import unittest
import stat
import time
import shutil
import os
@ -325,6 +326,7 @@ class TestReadOnlyArchiveMembers(unittest.TestCase):
tarinfo = tarfile.TarInfo('./tests/data/dirty.jpg')
tarinfo.mtime = time.time()
tarinfo.uid = 1337
tarinfo.gid = 0
tarinfo.mode = 0o000
tarinfo.size = os.stat('./tests/data/dirty.jpg').st_size
with open('./tests/data/dirty.jpg', 'rb') as f:
@ -340,3 +342,121 @@ class TestReadOnlyArchiveMembers(unittest.TestCase):
os.remove('./tests/data/clean.tar')
os.remove('./tests/data/clean.cleaned.tar')
class TestPathTraversalArchiveMembers(unittest.TestCase):
def test_tar_traversal(self):
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/dirty.png')
tarinfo = tarfile.TarInfo('./tests/data/dirty.jpg')
tarinfo.name = '../../../../../../../../../../tmp/mat2_test.png'
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
def test_tar_absolute_path(self):
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/dirty.png')
tarinfo = tarfile.TarInfo('./tests/data/dirty.jpg')
tarinfo.name = '/etc/passwd'
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
def test_tar_duplicate_file(self):
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
for _ in range(3):
zout.add('./tests/data/dirty.png')
tarinfo = tarfile.TarInfo('./tests/data/dirty.jpg')
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
def test_tar_setuid(self):
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/dirty.png')
tarinfo = tarfile.TarInfo('./tests/data/dirty.jpg')
tarinfo.mode |= stat.S_ISUID
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
def test_tar_setgid(self):
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/dirty.png')
tarinfo = tarfile.TarInfo('./tests/data/dirty.jpg')
tarinfo.mode |= stat.S_ISGID
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
def test_tar_symlink_absolute(self):
os.symlink('/etc/passwd', './tests/data/symlink')
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/symlink')
tarinfo = tarfile.TarInfo('./tests/data/symlink')
tarinfo.linkname = '/etc/passwd'
tarinfo.type = tarfile.SYMTYPE
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
os.remove('./tests/data/symlink')
def test_tar_symlink_ok(self):
shutil.copy('./tests/data/dirty.png', './tests/data/clean.png')
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/dirty.png')
t = tarfile.TarInfo('mydir')
t.type = tarfile.DIRTYPE
zout.addfile(t)
zout.add('./tests/data/clean.png')
t = tarfile.TarInfo('mylink')
t.type = tarfile.SYMTYPE
t.linkname = './tests/data/clean.png'
zout.addfile(t)
zout.add('./tests/data/dirty.jpg')
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
os.remove('./tests/data/clean.png')
def test_tar_symlink_relative(self):
os.symlink('../../../etc/passwd', './tests/data/symlink')
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('./tests/data/symlink')
tarinfo = tarfile.TarInfo('./tests/data/symlink')
with open('./tests/data/dirty.jpg', 'rb') as f:
zout.addfile(tarinfo=tarinfo, fileobj=f)
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
os.remove('./tests/data/symlink')
def test_tar_device_file(self):
with tarfile.open('./tests/data/clean.tar', 'w') as zout:
zout.add('/dev/null')
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/clean.tar')
os.remove('./tests/data/clean.tar')
def test_tar_hardlink(self):
shutil.copy('./tests/data/dirty.png', './tests/data/clean.png')
os.link('./tests/data/clean.png', './tests/data/hardlink.png')
with tarfile.open('./tests/data/cleaner.tar', 'w') as zout:
zout.add('tests/data/clean.png')
zout.add('tests/data/hardlink.png')
with self.assertRaises(ValueError):
archive.TarParser('./tests/data/cleaner.tar')
os.remove('./tests/data/cleaner.tar')
os.remove('./tests/data/clean.png')
os.remove('./tests/data/hardlink.png')