题目

题目描述： py又cc
附件：（资源已上传）

pyc文件是是py的编译文件，使用反编译工具还原文件

1. 反编译pyc文件

在线工具：http://tools.bugscaner.com/decompyle/
本地工具：uncompyle6
pip install uncompyle6
uncompyle6 xxx.pyc > xxx.py

安装参考链接：https://blog.csdn.net/qq_26328861/article/details/136188163
得到py文件：

# uncompyle6 version 3.9.1
# Python bytecode version base 3.8.0 (3413)
# Decompiled from: Python 3.11.8 (tags/v3.11.8:db85d51, Feb  6 2024, 22:03:32) [MSC v.1937 64 bit (AMD64)]
# Embedded file name: ./pyc.py
# Compiled at: 2024-01-23 16:32:18
# Size of source mod 2**32: 503 bytes
import random

def encrypt_file(file_path):
    random.seed(114514)
    with open(file_path, "rb") as file:
        data = file.read()
    encrypted_data = b''
    for byte in data:
        key = random.randint(0, 128)
        encrypted_data += chr(byte ^ key).encode()
    else:
        encrypted_file_path = file_path + ".enc"
        with open(encrypted_file_path, "wb") as encrypted_file:
            encrypted_file.write(encrypted_data)
        return encrypted_file_path


file_path = "./flag"
encrypt_file(file_path)

# okay decompiling secret.pyc

2. 解密

加密时，对明文每个字节byte与随机key进行异或运算，然后加密
encrypted_data += chr(byte ^ key).encode()
由于随机种子固定，则random得到的随机数固定，直接对字节进行解密：
decrypted_data += bytes([byte ^ key])

import random
def decrypted_file(file_path):
    random.seed(114514)
    with open(file_path, 'rb') as (file):
        data = file.read()
    decrypted_data = b''
    for byte in data:
        key = random.randint(0, 128)
        decrypted_data += bytes([byte ^ key])

    decrypted_file_path = file_path[:-4]
    with open(decrypted_file_path, 'wb') as (decrypted_file):
        decrypted_file.write(decrypted_data)
    return decrypted_file_path

file_path = './flag.enc'
decrypted_file(file_path)

查看解密结果flag{U_R_g00d_at_do1n_pyc}