CTF--CRC宽高爆破脚本

import zlib
import struct
filename = 'abc.png'          # 这个文件放入要爆破的图片
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                                                # 理论上0xffffffff,但考虑到屏幕实际/cpu，0x0fff就差不多了
    for w in range(n):                                      # 高和宽一起爆破
        width = bytearray(struct.pack('>i', w))             #q为8字节，i为4字节，h为2字节
        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)
                exit(0)