bkcrack wrapper (https://github.com/kimci86/bkcrack)

inflate.py

#!/usr/bin/env python3

"""inflate.py: full archive decompression helper for bkcrack

usage: %s path/to/encrypted.zip kx ky kz
"""

import os
import subprocess
import sys
import time
import zipfile
import zlib


BKCRACK_BINARY_PATH = "bkcrack"
ZIP_FLAG_BIT_ENCRYPTED = 0x01


def recover_timestamp(info: zipfile.ZipInfo):
    """Set the file modification time based on zip headers."""
    timestamp = time.mktime((*info.date_time, 0, 0, 0))
    os.utime(info.filename, (timestamp, timestamp))


def inflate(path: str):
    """Decompress the deflated file in-place."""
    with open(path, "rb+") as f:
        inflated = zlib.decompress(f.read(), -zlib.MAX_WBITS)
        f.seek(0)
        f.write(inflated)
        f.truncate()


def decrypt(archive: zipfile.ZipFile, item: zipfile.ZipInfo, master_keys):
    """Call bkcrack with master keys to extract an encrypted file."""
    command = [
        BKCRACK_BINARY_PATH,
        '-C', archive.filename,
        '-c', item.filename,
        '-d', item.filename,
        '-k'] + master_keys
    subprocess.run(command, check=True)


def process(archive: zipfile.ZipFile, item: zipfile.ZipInfo, master_keys):
    """Extract a single entry from the zip archive."""

    # directory entry
    if item.is_dir():
        os.makedirs(
            item.filename,
            mode=item.external_attr >> 16,
            exist_ok=True)

    # cipher text: maybe compressed, maybe not
    elif item.flag_bits & ZIP_FLAG_BIT_ENCRYPTED:
        decrypt(archive, item, master_keys)

        if item.compress_type == zipfile.ZIP_STORED:
            pass
        elif item.compress_type == zipfile.ZIP_DEFLATED:
            inflate(item.filename)
        else:  # other algorithms are rarely used, but technically possible
            raise ValueError("unsupported compress type", item.compress_type)

    # plain text
    else:
        archive.extract(item.filename)

    recover_timestamp(item)


def main():
    if len(sys.argv) != 5:
        return print(__doc__ % sys.argv[0])

    _, archive_path, *master_keys = sys.argv
    with zipfile.ZipFile(archive_path) as archive:
        for item in archive.infolist():
            process(archive, item, master_keys)


if __name__ == "__main__":
    main()