Full Disclosure mailing list archives

Re: silly PoCs continue: X-Frame-Options give you less than expected


From: Dave <mrx () propergander org uk>
Date: Sat, 10 Dec 2011 23:29:27 +0000

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On 10/12/2011 22:39, Michal Zalewski wrote:
At the risk of annoying everyone...

I think we greatly underappreciate the extent to which JavaScript
allows you to exploit the limits of human perception. On modern
high-performance systems, windows can be opened, positioned, and
closed; and documents loaded and then navigated away from; so quickly
that we can't even reliably notice that, let alone react consciously.

The PoC I posted here earlier this week
(http://lcamtuf.coredump.cx/switch/) demonstrates one example of page
transitions occurring so fast that you don't register it; and some of
my earlier posts outlined the exploitation of page switching to
exploit browser UIs (e.g. http://lcamtuf.coredump.cx/ffgeo2/). Today,
I wanted to share this brief demonstration of an attack that should
hopefully illustrate why our current way of thinking about
clickjacking (and the possible defenses, such as X-Frame-Options) is
flawed:

http://lcamtuf.coredump.cx/clickit/

The basic idea here is that instead of placing the UI you want to
tamper with in an invisible or only partly-visible <iframe>, you can
achieve a similar effect simply by predicting the time of a
premeditated click (which is fairly easy if you look at mouse velocity
and distance to the expected destination), and then either destroying
the current window, or navigating to a different document (in this
case, a cheesy banking site).

While everything about this exploit is extremely goofy, and I put no
effort into making the transitions less obvious, it should still
demonstrate the issue neatly.

/mz

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Looks Like I won Michal. Where's my prize?

Clever stuff.

This kind of thing has occurred to me as system and indeed network/broadband speed have increased. One time a flashing 
of a neon on a router or
modem or the a flash of a window on a desktop gave some indication of data ingress or egress. Nowadays it's done and 
over with before the user
even realises something is afoot.

I had to enable Javascript though. I guess I trust you not to burn my ass. There are not many links posted on this list 
which I would click with
javascript enabled.

Thanks for your insights and the education

Dave

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