[BUUCTF]REVERSE——[GWCTF 2019]pyre

[GWCTF 2019]pyre

附件

步骤：
1.附件是pyc文件，用python打不开，百度后得知用python反编译工具打开，分享一个python反编译在线网站

反编译后是这段代码

#!/usr/bin/env python
# visit http://tool.lu/pyc/ for more information
print 'Welcome to Re World!'
print 'Your input1 is your flag~'
l = len(input1)              #输入字符串的长度
for i in range(l):           
    num = ((input1[i] + i) % 128 + 128) % 128  #对字符串的每一位进行加密，确保在128的范围内
    code += num

for i in range(l - 1):
    code[i] = code[i] ^ code[i + 1]   #字符串的前一位与后一为进行异或运算后赋值给前一位

print code
code = [
    'x1f',
    'x12',
    'x1d',
    '(',
    '0',
    '4',
    'x01',
    'x06',
    'x14',
    '4',
    ',',
    'x1b',
    'U',
    '?',
    'o',
    '6',
    '*',
    ':',
    'x01',
    'D',
    ';',
    '%',
    'x13']

程序很简单，将code字符串逆向一下上方的两个算法即可

exp

code = ['x1f','x12','x1d','(','0','4','x01','x06','x14','4',
        ',','x1b','U','?','o','6','*',':','x01','D',';','%','x13']

for i in range(len(code)-2,-1,-1):
    code[i]=chr(ord(code[i])^ord(code[i+1]))

for i in range(len(code)):
    print(chr((ord(code[i])-i)%128),end="")