[WEB SECURITY] Re: Can HTTP Request Smuggling be blocked by Web Application Firewalls?
Amit Klein (AKsecurity)
aksecurity at hotpop.com
Wed Jun 22 03:53:49 EDT 2005
On 22 Jun 2005 at 16:17, Andrew van der Stock wrote:
> I feel that the WAF in this case would increase the likelihood of a
> HTTP smuggling attack as it participates in the flow, and more than
> likely interprets HTTP requests differently than pretty much
> everything else out there.
Yes, that is possible (as I hinted in my message), if the WAF is between the devices, or if
the WAF itself is the object of the attack.
If they RST'd dodgy connections and left
> alone all others, then maybe these devices serve a purpose, but if
> it's a re-writing proxy, it has to affect the flow.
> <rant = on>
> I have been struggling with the point of "security" HTTP proxies
> recently in several of the projects I've been involved with. The
> projects were infected by sales people who say "Buy this widget, and
> all your security problems are over". Nothing could be further from
> the truth. I recently lost a battle to remove a virus scanning web
> proxy on a private leased line which transmitted XML provided by MQ
> Series. The impetus to buy useless things to solve non-existent
> problems is troubling.
> In my view, unless a proxy understands the underlying data and pages,
> or XML DTDs if it is looking at SOAP requests, I feel the additional
> burden of the proxies is rarely worthwhile and just adds one more
> component which may be abused.
Oh, I wouldn't throw the baby out with the bath water. I think that WAFs (at least in
theory) are basically good things. I haven't seen a perfect one yet - they all have their
problems. But I wouldn't dismiss them as useless.
Don't get me wrong - there are certainly cases where buying and deploying WAF is absurd,
and there are probably many cases where WAFs are sold as a solution to world hunger, but
that shouldn't blur our technical view - of what WAFs can and can't do.
I fully agree to the second part of your rant. If a WAF can't understand HTTP, and the
application logic, and SOAP/XML (if it's supposed to handle XML and web services), then
obviously it's missing a core security functionality. Merely deploying a simple (mindless)
HTTP proxy is not going to help in most situations (I believe that's what you're saying).
> Security vendors should perform strict conformance testing and make
> those results available to potential customers. Something like the
> old IPsec and cache bake offs or industry certification that these
> devices are truly RFC compliant would be nice.
Hear! Hear! ;-)
I'll have you know that WASC (Web Application Security Consortium) works on a project
called "Web Application Firewall Evaluation Criteria"
(http://www.webappsec.org/projects/waf_evaluation/) that aims at defining criteria for
evaluating and comapring WAFs.
When it's complete, hopefully it would be able to address people's needs and reduce the
hype levels in the market.
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