攻防世界 web2 write up

Posted 2020-11-13 欧欧欧欧提大人

攻防世界 web2 write up

minwen=‘a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws‘

#str_rot123()  

minwen-1 = ‘n1mYotDfPRFRVdEYjhDNlZjYld2Y5IjOkdTN3EDNlhzM0gzZiFTZ2MjO4gjf‘

#strrev()

minwen-2 = ‘fjg4OjM2ZTFiZzg0MzhlNDE3NTdkOjI5Y2dlYjZlNDhjYEdVRFRPfDtoYm1n‘

#base64decode()

minwen-3 = ‘~88:36e1bg8438e41757d:29cgeb6e48c`GUDTO|;hbmg‘

for($_0=0;$_0<strlen($_o);$_0++){
       
        $_c=substr($_o,$_0,1);  #单个取字母
        $__=ord($_c)+1;        #将ascii码以此+1
        $_c=chr($__);        #将+1后的ascii码取为字符
        $_=$_.$_c;   #依顺序拼接
       }

#所以只需要将+1改为-1

<?php
echo substr("Hello world",2,1)."<br>";

$_o ="~88:36e1bg8438e41757d:29cgeb6e48c`GUDTO|;hbmg";
$_="";

for($_0=0;$_0<strlen($_o);$_0++){
       
        $_c=substr($_o,$_0,1);
        $__=ord($_c)-1;
        $_c=chr($__);
        $_=$_.$_c;
}
echo $_;

?>


<?php

$flag="}77925d0af7327d30646c918bfda5d37b_FTCSN{:galf "."<br>";

echo strrev($flag);
?>


miwen="flag:{NSCTF_b73d5adfb819c64603d7237fa0d52977}"