Re: HTTP Parameter Pollution

[Ivan Ristic <ivan.ristic () gmail com>]

I don't think the two issues are "married", as you imply. For example,
let's assume that my application uses a backend subrequest whose query
string is constructed out of the value of the paramter "param":

http://backend.server/doSomething?key=$param

and that you inject "value&injectedKey=injectedValue" (URL-encoded)
into "param". The resulting backend request would thus be

http://backend.server/doSomething?key=value&injectedKey=injectedValue

So you have managed to pull off an attack using just query string
injection. Depending on the backend service, that alone may be enough
for exploitation.

Thus, I think HPP is the injection part alone.

I think your presentation would benefit from moving the discussion of
parameter processing inconsistencies into the second half, positioning
it as an additional technique that is needed to maximise the effect of
the injection vulnerability.


On Wed, May 20, 2009 at 2:13 PM, Stefano Di Paola
<stefano.dipaola () wisec it> wrote:
> Hi Ivan,
>
> HPP is an input validation vulnerability and, consequentially a
> possible attack, triggered by injection flaws in the context of
> generating QueryStrings/POST payloads.
>
> If you have only an injection (server or client side) in the context of
> query string construction, it doesn't mean you can actually override
> hardcoded parameters' values because of web server behaviour.
> On the other hand, if you know the web server/application behaviour and
> you cannot inject any parameter then you are obviously safe.
>
> So you need both hypothesis in order to exploit the issue.
>
> The main topic is that after identifying the application behaviour in
> managing multiple occurrences and considering which are the layers data
> passes through, an attacker could exploit the parameter injection
> vulnerability. And this is HPP.
>
> I hope we answered your question.
> However within the whitepaper, we are going to explain everything in
> detail and likely, we will be able to show the essence of this flaw.
>
> Cheers,
> Stefano & Luca
>
> Il giorno mer, 20/05/2009 alle 10.06 +0200, Ivan Ristic ha scritto:
> > Hi Stefano,
> >
> > Your presentation discusses two separate issues:
> >
> > 1. The differences in how various components handle multiple request
> > parameters with the same name when an application expects only one
> > (parameter).
> > 2. Attacks against query string construction flaws in applications.
> >
> > Just from reading the slides I couldn't determine which is the main
> > topic, and which is the one you named HPP?
> >
> >
> > On Tue, May 19, 2009 at 1:52 PM, Stefano Di Paola
> > <stefano.dipaola () wisec it> wrote:
> > > Hi guys,
> > >
> > > during OWASP AppSec Poland 2009 we presented a newly discovered input
> > > validation vulnerability called "HTTP Parameter Pollution" (HPP).
> > >
> > > Basically, it can be defined as the feasibility to override or add HTTP
> > > GET/POST parameters by injecting query string delimiters.
> > >
> > > In the last months, we have discovered several real world flaws in which
> > > HPP can be used to modify the application behaviors, access
> > > uncontrollable variables and even bypass input validation checkpoints
> > > and WAFs rules.
> > >
> > > Exploiting such HPP vulnerabilities, we have found several problems in
> > > some Google Search Appliance front-end scripts, Ask.com, Yahoo! Mail
> > > Classic and many other products.
> > >
> > > If you are interested, you are kindly invited to have a look at:
> > > http://www.owasp.org/images/b/ba/AppsecEU09_CarettoniDiPaola_v0.8.pdf
> > >
> > > We're going to release additional materials in the next future,
> > > including a video of the Yahoo! attack vector.
> > >
> > > Stay tuned on http://blog.mindedsecurity.com and
> > > http://blog.nibblesec.org
> > >
> > > Cheers,
> > > Stefano Di Paola and Luca Carettoni
> > >
> > > --
> > > Stefano Di Paola
> > > Chief Technology Officer, LA/ISO27001
> > > Minded Security Research Labs Director
> > >
> > > Minded Security - Application Security Consulting
> > >
> > > Official Site: www.mindedsecurity.com
> > >
> > > Personal Blog: www.wisec.it/sectou.php
> > > ..................
> --
> ...oOOo...oOOo....
> Stefano Di Paola
> Software & Security Engineer
>
> Owasp Italy R&D Director
>
> Web: www.wisec.it
> ..................



-- 
Ivan Ristic