2023-10-13 No.11 is gone2

下载题目得到流量包No.11 is gone2.pcapng，打开过滤ftp-data发现很多压缩包

1.png

直接导出所有压缩包，发现除了11.zip其他都是4字节，采用crc爆破

import zipfile
import string
import binascii
def CrackCrc(crc):
    for a in dic:
        for b in dic:
            for c in dic:
                for d in dic:
                    s = a + b + c + d
                    s = s.encode()
                    if crc == (binascii.crc32(s) & 0xffffffff):
                        print(s)
                        return s
dic=string.printable
result=''
for i in range(1,69):
    if i==11:
        continue
    file = str(i)+'.zip' # 爆破的压缩包
    f = zipfile.ZipFile(file, 'r')
    tmp = str(i)+'.txt' # 压缩包中的小字节文件
    GetCrc = f.getinfo(tmp)
    crc = GetCrc.CRC
    #print("Trying crack",tmp," \nIt has the value of crc ",crc)
    result+=CrackCrc(crc).decode()
print(result)

爆破得到

UEsDBBQACQAIAHoGa1UEgkKgNgAAACgAAAAIAAAAZy50eHQnPL9D20a0sgfK5QEzCtDJWrot+ljdYIPzWkybokUz57zIc8u0DCUTyQHa02X8M5IAviVj/fZQSwECFAAUAAkACAB6BmtVBIJCoDYAAAAoAAAACAAkAAAAAAAAACAAAAAAAAAAZmxhZy50eHQKACAAAAAAAAEAGABZOca6JPXYAdHi/Qsl9dgBILcWtyT12AFQSwUGAAAAAAEAAQBaAAAAXAAAAAAA

用CyberChef的base64解码后，发现PK，另存为压缩包flag.zip

2.png

不能正常打开，发现g.txt'<?字符，猜测需要修复

3.png

4.png

修复完后可以正常打开，但是有密码。根据题目名称查看11.zip，发现需要密码

5.png

p@33w07D1sE4sy

猜测是flag.zip密码，解压得到flag：DASCTF{69a7c3f8eae457779f53be70a7e14a87}

6.png