Function _ZipDecrypter

Lib/zipfile/__init__.py:713–748

(pwd)

#     plain_bytes = zd(cypher_bytes)

def _ZipDecrypter(pwd):
    key0 = 305419896
    key1 = 591751049
    key2 = 878082192

    global _crctable
    if _crctable is None:
        _crctable = list(map(_gen_crc, range(256)))
    crctable = _crctable

    def crc32(ch, crc):
        """Compute the CRC32 primitive on one byte."""
        return (crc >> 8) ^ crctable[(crc ^ ch) & 0xFF]

    def update_keys(c):
        nonlocal key0, key1, key2
        key0 = crc32(c, key0)
        key1 = (key1 + (key0 & 0xFF)) & 0xFFFFFFFF
        key1 = (key1 * 134775813 + 1) & 0xFFFFFFFF
        key2 = crc32(key1 >> 24, key2)

    for p in pwd:
        update_keys(p)

    def decrypter(data):
        """Decrypt a bytes object."""
        result = bytearray()
        append = result.append
        for c in data:
            k = key2 | 2
            c ^= ((k * (k^1)) >> 8) & 0xFF
            update_keys(c)
            append(c)
        return bytes(result)

    return decrypter


class LZMACompressor: