RE: [WEB SECURITY] Bypassing WAF via HTTP Pollution

["Dave Wichers" <dave.wichers () aspectsecurity com>]

Regarding combining parameters, ASP and ASP.NET and a couple of others do this by default by creating a comma separated 
list. This behavior of combining parameters was mentioned in Stefano di Paola and Luca Carettoni's original talk on 
this topic at OWASP AppSec Poland in 2009. They list which specific platforms do/do not do this on slide 9 of their 
talk.  If people are aware of others, I'd love to know about them.

Their presentation is here: https://www.owasp.org/images/b/ba/AppsecEU09_CarettoniDiPaola_v0.8.pdf

I don't know if this slide is also published somewhere on the web, but if it isn't, it should be. It’s a very useful 
reference for this kind of research.

Since it’s a PDF, I can't simply cut / paste the text and include it here. If someone wants to get this info on to a 
public page so its easier to find/use, I'm sure we can get the original presentation from Stefano.

-Dave

-----Original Message-----
From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of Ivan Ristic
Sent: Monday, October 08, 2012 3:55 PM
To: Robin Wood
Cc: Danux; web security; pen-test () securityfocus com; webappsec () securityfocus com
Subject: Re: [WEB SECURITY] Bypassing WAF via HTTP Pollution

On Mon, Oct 8, 2012 at 10:51 AM, Robin Wood <robin () digininja org> wrote:
> On 4 October 2012 10:40, Ivan Ristic <ivan.ristic () gmail com> wrote:
> > I guess this would be a good opportunity for me to mention my 
> > research on the topic:
> >
> > Protocol-level evasion of web application firewalls 
> > http://blog.ivanristic.com/2012/07/protocol-level-evasion-of-web-appl
> > ication-firewalls.html
>
> I like the table Danux has showing what order the various 
> languages/technologies parse the parameters and was wondering if 
> anyone had a table like this for WAFs, that way it would be a lot 
> easier to match the language and the WAF and know what ordering to use 
> to bypass it.

According to my reading of the blog post, the "WAF" in question was a simulation. In reality, I wouldn't expect that 
you'd be able to bypass a WAF by providing multiple instances of the same parameter. The expected behaviour is that all 
such values are inspected.

Where it gets tricky is when you are able to split the payload across two or more parameter instances, and you're 
attacking an application that will combine the values into a single string. That could be handy for bypassing WAFs, but 
it depends entirely on being able to craft a payload that will not be detected in "pieces".


> Robin
>
>
> > On Wed, Oct 3, 2012 at 10:55 AM, Danux <danuxx () gmail com> wrote:
> > > By playing CSAW CTF you always learn something new (at least myself).
> > >
> > > Hope you enjoy it:
> > >
> > > http://danuxx.blogspot.com/2012/10/bypassing-waf-via-http-parameter.
> > > html
> > >
> > > --
> > > DanUx
> > >
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> >
> >
> >
> > --
> > Ivan Ristić
> >
> >
> >
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--
Ivan Ristić



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