[攻防世界 - reverse - 新手区] python-trade

python在线反编译把.pyc反编译为伪代码

#!/usr/bin/env python
# visit https://tool.lu/pyc/ for more information
import base64

def encode(message):
    s = ''
    for i in message:
        x = ord(i) ^ 32
        x = x + 16
        s += chr(x)
    
    return base64.b64encode(s)

correct = 'XlNkVmtUI1MgXWBZXCFeKY+AaXNt'
flag = ''
print 'Input flag:'
flag = raw_input()
if encode(flag) == correct:
    print 'correct'
else:
    print 'wrong'

观察得知，调用encode函数对输入的flag进行加密后，得到的密文应为correct, 即"XlNkVmtUI1MgXWBZXCFeKY+AaXNt"
则可根据encode函数编写程序进行解密

import base64

s = 'XlNkVmtUI1MgXWBZXCFeKY+AaXNt'
get_flag = ''
dec = base64.b64decode(s)
for i in dec:
    i = i - 16
    i = i ^ 32
    get_flag = get_flag + chr(i)
print(get_flag)

得到flag：

nctf{d3c0mpil1n9_PyC}