lsasecrets.py 文件源码

def decrypt_secret(secret, key):
    """Python implementation of SystemFunction005.

    Decrypts a block of data with DES using given key.
    Note that key can be longer than 7 bytes."""
    decrypted_data = ''
    j = 0   # key index
    for i in range(0, len(secret), 8):
        enc_block = secret[i:i + 8]
        block_key = key[j:j + 7]
        des_key = hashdump.str_to_key(block_key)

        des = DES.new(des_key, DES.MODE_ECB)
        enc_block = enc_block + "\x00" * int(abs(8 - len(enc_block)) % 8)
        decrypted_data += des.decrypt(enc_block)

        j += 7
        if len(key[j:j + 7]) < 7:
            j = len(key[j:j + 7])

    (dec_data_len,) = struct.unpack("<L", decrypted_data[:4])
    return decrypted_data[8:8 + dec_data_len]