#!/usr/bin/env python3
# Copyright (c) 2008-11 Qtrac Ltd. All rights reserved.
# This program or module is free software: you can redistribute it and/or
# modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version. It is provided for educational
# purposes and is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.

# Useful on Windows where tar isn't supplied as standard

BZ2_AVAILABLE = True
try:
    import bz2
except ImportError:
    BZ2_AVAILABLE = False
import os
import string
import sys
import tarfile


UNTRUSTED_PREFIXES = tuple(["/", "\\"] +
        [c + ":" for c in string.ascii_letters])


def main():
    if len(sys.argv) != 2 or sys.argv[1] in {"-h", "--help"}:
        error("usage: untar.py archive.{{tar,{0}tar.gz}}".format(
              "tar.bz2," if BZ2_AVAILABLE else ""), 2)

    archive = sys.argv[1]
    if not archive.lower().endswith((".tar", ".tar.gz", ".tar.bz2")):
        error("{0} doesn't appear to be a tarball".format(archive))
    if not BZ2_AVAILABLE and archive.lower().endswith(".bz2"):
        error("bzip2 decompression is not available")
    if not os.path.exists(archive):
        error("{0} doesn't appear to exist".format(archive))
    untar(archive)


def untar(archive):
    tar = None
    try:
        tar = tarfile.open(archive)
        for member in tar.getmembers():
            if member.name.startswith(UNTRUSTED_PREFIXES):
                print("untrusted prefix, ignoring", member.name)
            elif ".." in member.name:
                print("suspect path, ignoring", member.name)
            else:
                tar.extract(member)
                print("unpacked", member.name)
    except (tarfile.TarError, EnvironmentError) as err:
        error(err)
    finally:
        if tar is not None:
            tar.close()


def error(message, exit_status=1):
    print(message)
    sys.exit(exit_status)


main()