[GKCTF 2021]签到

附件是一个流量包，追踪TCP流发现编码过的信息

首先是十六进制转字符

发现是base64编码，然后对其进行解码发现是倒序的文件名

将http数据全部导出，找到2KB的tmpshell(19).php打开

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

转为字符

base64解码

保存为txt后到kali中输入命令进行倒序解码

rev tmp.txt > tmpshell.txt
cat tmpshell.txt | base64 -d > result.txt

打开后发现flag

去重，得到flag{Welc0me_GkC4F_m1siCCCCCC!}

flag{Welc0me_GkC4F_m1siCCCCCC!}