[misc]-压缩包-zip

题目：拼在一起解下base64就有flag

打开附件，发现都是68个小的压缩文件，且是加密的，根据题目提示，考虑crc32碰撞。

import zipfile
import string
import binascii
import base64

d = open('rs.zip', 'wb')
b64 = ''
dic = string.ascii_letters + string.digits + '{}_+/='


def CrackCrc(crc):
    for i in dic:
        for j in dic:
            for k in dic:
                for h in dic:
                    s = i + j + k + h
                    if crc == (binascii.crc32(s.encode())):
                        # b64+=s
                        return s


def CrackZip():
    ts = ''
    for i in range(68):
        print(str(i) + '开始\n')
        fn = '1\\' + 'out' + str(i) + '.zip'
        with open(fn, 'r') as ob:
            crc = zipfile.ZipFile(fn, 'r').getinfo('data.txt').CRC
            # obf=ob.read()
            # crc = ''.join(obf[14:18])
            ts += CrackCrc(crc)
        print(str(i) + 'end\n')
    return ts


b64 = CrackZip()
print("CRC32碰撞完成")
print(b64)
ds = base64.b64decode(b64)
d.write(ds)
d.close()

得到：z5BzAAANAAAAAAAAAKo+egCAIwBJAAAAVAAAAAKGNKv+a2MdSR0zAwABAAAAQ01UCRUUy91BT5UkSNPoj5hFEVFBRvefHSBCfG0ruGnKnygsMyj8SBaZHxsYHY84LEZ24cXtZ01y3k1K1YJ0vpK9HwqUzb6u9z8igEr3dCCQLQAdAAAAHQAAAAJi0efVT2MdSR0wCAAgAAAAZmxhZy50eHQAsDRpZmZpeCB0aGUgZmlsZSBhbmQgZ2V0IHRoZSBmbGFnxD17AEAHAA==

是base64编码，解密后得到乱码，010查看可以发现有flag.txt字样：考虑压缩文件，补齐文件头得到

打开后发现

flag{nev3r_enc0de_t00_sm4ll_fil3_w1th_zip}