Automates some of the legwork for dealing with ZiX-12B archives with unrpa.

decoder.py

#!/usr/bin/env python2

import subprocess
import re
import os
import sys
import platform
import StringIO

try:
    import uncompyle6
except ImportError:
    print("You need uncompyle6 - do a 'pip install uncompyle6' in your python 2.x environment.")
    sys.exit(1)

try:
    import _string
except ImportError:
    print("You need the '_string' module from the source. Find '_string.pyd'/'_string.so' for your platform.")
    sys.exit(1)

archive, extraction_path, loader = sys.argv[1:]

if platform.system() == "Windows":
    python3 = ["py", "-3"]
else:
    python3 = ["python3"]

with open(archive, "rb") as f:
    line = f.readline()
    parts = line.split()
    raw_offset = parts[-1]

decompiled = StringIO.StringIO()
uncompyle6.decompile_file(loader, outstream=decompiled)
match = re.search(r"verificationcode = _string.sha1\('(.*)'\)", decompiled.getvalue())
verification_code = match.group(1).encode("ascii", "ignore")
decompiled.close()

offset = _string.offset(raw_offset)
key = _string.sha1(verification_code)

paths = subprocess.check_output(
    python3 + ["unrpa", "-mp", extraction_path, archive, "-o", str(offset), "-k", str(key), "-v"])

for path in paths.split(os.linesep):
    if path:
        path = os.path.join(extraction_path, path)
        with open(path, "rb") as f:
            decoded = _string.run(f.read(64), key) + f.read()
        with open(path, "wb") as f:
            f.write(decoded)

Please note this is a Python 2 script - it will need to be run in the same directory as _string.pyd/_string.so, and on a version of Python compatible with the one used for the Ren'Py project that module was originally from.

To run, place alongside _string, unrpa and then run, providing the path to the archive, the path to the extraction folder, and the path to the loader.pyo file from the Ren'Py project the archive is from. E.g:

On Linux:
python2 decoder.py archive.rpa extracted loader.pyo

On Windows:
py -2 decoder.py archive.rpa extracted loader.pyo