BUUCTF [湖南省赛2019]Findme

首先下载之后是5个png文件

第一个打开是很多像素点 应该是宽度和高度被修改了

不会写脚本 附上大佬的脚本

 

                

import zlib
import struct

filename = '1.png'
with open(filename, 'rb') as f:
    all_b = f.read()
    crc32key = int(all_b[29:33].hex(),16)
    data = bytearray(all_b[12:29])
    n = 4095           
    for w in range(n):          
        width = bytearray(struct.pack('>i', w))    
        for h in range(n):
            height = bytearray(struct.pack('>i', h))
            for x in range(4):
                data[x+4] = width[x]
                data[x+8] = height[x]
            crc32result = zlib.crc32(data)
            if crc32result == crc32key:
                print("宽为：",end="")
                print(width)
                print("高为：",end="")
                print(height)