[XDCTF-2017] base64

Posted    on 2017, Oct6, Friday 02:12:44
Modified on 2017, Oct6, Friday 02:12:46

分析

题目中给出了一个txt,其内容为

bWFpbigpe2ludCBpLG5bXT17KCgoMSA8PDEpPDwgKDE8PDEpPDwoMTw8Cm==
ICAgICAgIDEpPDwoMTw8KDE+PjEpKSkrKCgxPDwxKTw8KDE8PDEpKSksKCgoMQp=
ICAgICAgIDw8ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAxKQq=
ICAgICAgIDw8ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAoMQp=
ICAgICAgIDw8MSk8PCgxPDwxKTw8ICAgICAgICAgKDE8PDEpKS0oKDE8PDEpPDwoCr==
ICAgIAkxPDwxKTw8KDE8PDEpKSsgICAgICAgICgoMTw8MSk8PCgxPDwoMT4+Ch==
ICAgICAgIDEpKSkrKDE8PCgxPj4xKSkpICAgICAgICAgICAgICAgICAgICAgICAgLAq=
ICAgICAgICgoKDE8PDEpPDwoMTw8MSkgICAgICAgICAgICAgICAgICAgICAgICA8PAo=
ICAgICAgICgxPDwxKTw8KDE8PDEpKS0oKDEgPDwxKTw8KDE8PDEpIDw8KDE8PCgxCl==
ICAgICAgID4+MSkpKS0oKDE8PDEpPDwoMTw8KDE+PjEpKSkpLCgoKDE8PDEpCp==
ICAgICAgIDw8KCAgICAxPDwgICAgICAgICAgICAgICAgICAgICAgICAgIDEpCt==
ICAgICAgIDw8KCAgICAxPDwgICAgICAgICAgICAgICAgICAgICAgICAgIDEpCu==
ICAgICAgIDw8KCAxPDwxKSktKCgxIDw8MSk8PCAoMSA8PDEpPDwoMSA8PAr=
ICAgICAgICgxPj4xKSkpLSgoMTw8MSk8PCgxPDwoMT4+MSkpKSksKCgoMTw8MSk8PAo=
ICAgICAgICgxPDwxKTw8KDE8PDEpPDwoMTw8MSkpLSgoMTw8MSk8PCgxPDwxKTw8KAr=
ICAgICAgIDE8PCgxPj4xKSkpLSgxPDwoMT4+ICAgICAgICAgIDEpKSksKCgoMTw8MSk8PAq=
ICAgICAgICgxPDwxKTw8KDE8PDEpKSsgICAgKCgxPDwxKSAgICA8PCgxPDwxKTw8Ch==
ICAgICAgICgxPDwoMT4+MSkpKS0oKCAgICAgMTw8MSk8PCggICAgICAxPDwoMT4+Co==
ICAgICAgIDEpKSkpLCgoMTw8MSk8PCAgICAgICgxPDwxKSAgICAgICAgPDwoMTw8MSkpCl==
ICAgICAgICwoKCgxPDwxKTw8KDE8PCAgICAgIDEpPDwoICAgICAgIDE8PDEpPDwoMTw8MSkpLQr=
ICAgICAgICgoMTw8MSk8PCgxPDwxKSAgICAgKS0oMTw8KDE+PjEpICAgICAgKSksKCgoCj==
ICAgICAgIDE8PDEpPDwoMTw8MSk8PCggICAgMTw8MSk8PCgxPDwxKSktICAgICgoMQp=
ICAgICAgIDw8ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgMQq=
ICAgICAgICkgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICA8PAp=
ICAgICAgICgxPDwxKTw8KDE8PCgxPj4xKSkpLSgxPDwoMT4+MSkpKSwgKCgoMTw8MQp=
ICAgICAgICk8PCgxPDwxKTw8KDE8PDEpPDwoMTw8MSkpLSgoMTw8MSk8PCAoMSAgCk==
ICAgICAgIDw8ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAxCp==
ICAgICAgICkgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIDw8Cn==
ICAgICAgICggICAgIDE8PCgxPj4xKSkpKyAgICAoMTw8MSkpLCgoKDEgICAgIDw8Cj==
ICAgICAgIDEpICAgIDw8KDE8PDEpPDwgICAgICAoMTw8MSk8PCgxICAgICAgIDw8Ck==
ICAgICAgIDEgICAgICkpLSgoMTw8MSk8PCAgICAoMTw8MSk8PCgxICAgICAgIDw8Cj==
ICAgICAgICggICAgIDE+PjEpKSktKCgxICAgICAgPDwxKTw8KDE8PCAgICAgICAoCj==
ICAgICAgIDEgICAgID4+MSkpKSksKCgoMSAgICAgPDwxKTw8KDEgICAgICAgIDw8Cg==
ICAgICAgIDEgICAgICk8PCgxPDwxKTw8KCAgICAgMTw8MSkpLSgoMSAgICAgIDw8Cm==
ICAgICAgIDEgICAgICk8PCgxPDwxKTw8ICAgICAoMTw8MSkpKygoICAgICAgICAxCv==
ICAgICAgIDw8MSk8PCgxPDwoMT4+MSkpKSksKCgoMTw8MSk8PCgxPDwxKSA8PCgxCm==
ICAgICAgIDw8MSkpKygxPDwoMT4+MSkpKSwoKCgxPDwxKTw8KDE8PDEpKSArKCgxCs==
ICAgICAgIDw8MSk8PCAoMTw8KDE+PjEpKSkgKyAoMTw8ICgxPj4xKSkpfSA7Zm9yCn==
ICAgICAgIChpPSgxPj4xKTtpPCgoKDE8PDEpPDwoMSA8PDEpKSsoKDEgPDwxKTw8KAr=
ICAgICAgIDE8PCgxPj4xKSkpKygxPDwxKSk7aSsrKSAgcHJpbnRmKCIlYyIsbltpXSk7fQp=

很显然里面是很多行base64,由于base64本身可以编码换行符,一般没必要编码成这样,所以考虑这是个base64隐写题,使用脚本一跑即可得到flag

附录

base64隐写: base64详解