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
打开010Editor修复
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
直接爆破得到密码1234，解压得到
p@33w07D1sE4sy
猜测是flag.zip密码，解压得到flag：DASCTF{69a7c3f8eae457779f53be70a7e14a87}
6.png
