攻防世界web进阶区web2详解

<?php
$miwen="a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";

function encode($str){
    $_o=strrev($str);
    // echo $_o;
        
    for($_0=0;$_0<strlen($_o);$_0++){
       
        $_c=substr($_o,$_0,1);
        $__=ord($_c)+1;
        $_c=chr($__);
        $_=$_.$_c;   
    } 
    return str_rot13(strrev(base64_encode($_)));
}

highlight_file(__FILE__);
/*
   逆向加密算法，解密$miwen就是flag
*/
?>

<?php
$miwen="a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws";
$miwen=base64_decode(strrev(str_rot13($miwen)));

//echo $miwen;

$m=$miwen;

for($i=0;$i<strlen($m);$i++){
        
    $_c=substr($m,$i,1);
    $__=ord($_c)-1;    # 字符转数字，在减1
    $__=chr($__);      # 数字转字符 

    $_=$_.$__;         # 拼接字符串

    }

echo strrev($_);        # 反转字符串