NSCTF web200
Topic Link
http://ctf5.shiyanbar.com/web/web200.jpg
1)
分析代码可知a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws字符串经过一系列加密
2)解这道题相当于是逆过程分析
a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws
rot13 : n1mYotDfPRFRVdEYjhDNlZjYld2Y5IjOkdTN3EDNlhzM0gzZiFTZ2MjO4gjf
strrev : fjg4OjM2ZTFiZzg0MzhlNDE3NTdkOjI5Y2dlYjZlNDhjYEdVRFRPfDtoYm1n
base64 : ~88:36e1bg8438e41757d:29cgeb6e48c`GUDTO|;hbmg
3)代码逆过程
- <?php
- $_o="~88:36e1bg8438e41757d:29cgeb6e48c`GUDTO|;hbmg";
- $_="";
- for($_0=0;$_0<strlen($_o);$_0++){
- $_c=substr($_o,$_0,1);
- $__=ord($_c)-1;
- $_c=chr($__);
- $_=$_.$_c;
- }
- $_=strrev($_);
- echo $_;
- ?>