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news/2024/5/19 21:26:15 标签: 安全, ctf, 网络

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91最佳Writeup由 Robert_Wei 提供

反馈

难度：2

方向：Web

题解数：108

解出人数：10185

题目来源: CTF

题目描述:

解密

题目场景:

http://61.147.171.105:56591

100%

倒计时: 3时59分18秒

<?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 
*/ 
?>

get the flag

<?php 
$miwen="a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws"; 
echo $miwen;
function encode($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 
*/ 
echo "\n";
echo "test:";
echo encode("123");
$str = "Uryyb Jbeyq!";
    $str_rot13 = str_rot13($str);
    echo "\n";
    echo $str_rot13; // 输出 "Hello World!"

echo "\n";
echo str_rot13($miwen);
echo "\n";
echo strrev(str_rot13($miwen));
echo "\n";
echo base64_decode(  strrev(str_rot13($miwen)) );

$_o=base64_decode(  strrev(str_rot13($miwen)) );

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

echo "\n";
echo $_;
echo "\n";
echo strrev($_);


?>

using vscode

a1zLbgQsCESEIqRLwuQAyMwLyq2L5VwBxqGA3RQAyumZ0tmMvSGM2ZwB4tws
test:321lZQA
Hello World!
n1mYotDfPRFRVdEYjhDNlZjYld2Y5IjOkdTN3EDNlhzM0gzZiFTZ2MjO4gjf
fjg4OjM2ZTFiZzg0MzhlNDE3NTdkOjI5Y2dlYjZlNDhjYEdVRFRPfDtoYm1n
~88:36e1bg8438e41757d:29cgeb6e48c`GUDTO|;hbmg
}77925d0af7327d30646c918bfda5d37b_FTCSN{:galf
flag:{NSCTF_b73d5adfb819c64603d7237fa0d52977}