CTF CRYPTO 密码学-3

题目名称：反编译

题目描述：

分析

题目给出一个pyc后缀的文件，需要使用uncompyle6模块去还原成py文件

uncompyle6简介

uncompyle6 是一个 Python 反编译器，它能够将 Python 字节码（.pyc 文件）转换回源代码（.py 文件）。

解题过程：

Step1：下载uncompyle6包

pip install uncompyle6

注意 版本问题

uncompyle6默认只支持3.8及以下版本
如何修改？（我这里是python3.11.3）

Python311\Lib\site-packages\uncompyle6\bin\uncompile.py

修改位置：Python311\Lib\site-packages\xdis\magics.py

Step2：在uncompyle6.exe目录下运行反编译命令

Step3：编写逆算法

生成的py文件内容如下：

# uncompyle6 version 3.7.4
# Python bytecode 2.7 (62211)
# Decompiled from: Python 3.11.3 (tags/v3.11.3:f3909b8, Apr  4 2023, 23:49:59) [MSC v.1934 64 bit (AMD64)]
# Embedded file name: b'C:\\Users\\CD\\Desktop\\\xb7\xb4\xb1\xe0\xd2\xeb\\crypto11.py'
# Compiled at: 2019-11-24 10:36:35
import base64

def encode1(ans):
    s = ''
    for i in ans:
        x = ord(i) ^ 18
        x = x + 19
        s += chr(x)

    return s


def encode2(ans):
    s = ''
    for i in ans:
        x = ord(i) + 66
        x = x ^ 32
        s += chr(x)

    return s


def encode3(ans):
    return base64.b16encode(ans)


flag = ' '
print 'Please Input your flag:'
flag = raw_input()
final = 'E9F3E8EA9EECE859E5555BA0A05F555A555CEBE955EC59E5EC5AECE858E9ECE555EB5FE6E8E4'
if encode3(encode2(encode1(flag))) == final:
    print 'correct'
else:
    print 'wrong'

逆运算脚本如下：

import base64
def decode2(ans):
    s = ''
    for i in ans:
        j=ord(i)
        x=j ^ 32
        x-=66
        s += chr(x)

    return s


def decode1(ans):
    s = ''
    for i in ans:
        j=ord(i)
        x=j-19
        x=x^18
        s += chr(x)

    return s

final = 'E9F3E8EA9EECE859E5555BA0A05F555A555CEBE955EC59E5EC5AECE858E9ECE555EB5FE6E8E4'
s = base64.b16decode(final)

s = decode1(decode2(s))

print s

相关资源：

链接：https://pan.baidu.com/s/13S5xdwEvsb1H0nLTlyzMAA
提取码：25fq