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Re: ACTION-240 :TLS errors...

From: Serge Egelman <egelman@cs.cmu.edu>
Date: Sat, 21 Jul 2007 17:32:15 -0400
Message-ID: <46A27B5F.5040404@cs.cmu.edu>
To: Mary Ellen Zurko <Mary_Ellen_Zurko@notesdev.ibm.com>
CC: "'W3C WSC Public'" <public-wsc-wg@w3.org>

Umm, yeah, that's the exact same paper that I sent out :)

serge

Mary Ellen Zurko wrote:
> 
> I would also recommend:
> 
> http://cups.cs.cmu.edu/soups/2005/2005proceedings/p13-garfinkel.pdf
> 
> to see it's use in a context (email), and get a sense of its strengths
> and weaknesses (not so hot for bootstrapping attacks, but great for the
> continuity thing it's named after).
> 
>           Mez
> 
> 
> 
> public-wsc-wg-request@w3.org wrote on 07/19/2007 11:39:00 AM:
> 
>> [image removed]
>>
>> Re: ACTION-240 :TLS errors...
>>
>> Serge Egelman
>>
>> to:
>>
>> Dan Schutzer
>>
>> 07/19/2007 11:44 AM
>>
>> Sent by:
>>
>> public-wsc-wg-request@w3.org
>>
>> Cc:
>>
>> "'Johnathan Nightingale'", "'W3C WSC Public'"
>>
>>
>> I haven't done any work on it.  But this might help:
>>
>> http://portal.acm.org/citation.cfm?id=1073003
>>
>> Read the references as well, if you're not familiar with them.  I'm sure
>> you can download the paper elsewhere if you google for it.
>>
>> serge
>>
>>
>> Dan Schutzer wrote:
>> > Can you send me some references to your work in Key continuity
> management?
>> > Thanks
>> >
>> > Dan
>> >
>> > -----Original Message-----
>> > From: public-wsc-wg-request@w3.org
> [mailto:public-wsc-wg-request@w3.org] On
>> > Behalf Of Serge Egelman
>> > Sent: Wednesday, July 18, 2007 10:11 AM
>> > To: Johnathan Nightingale
>> > Cc: W3C WSC Public
>> > Subject: Re: ACTION-240 :TLS errors...
>> >
>> >
>> > Righto, I now see what he meant and am in complete agreement.  This is
>> > delving into not just keeping track of root certificates (which I think
>> > you all know my opinion on), to keeping track of every certificate.
>> > Peter Gutmann and Simson Garfinkel have done some work on this-- "key
>> > continuity management", and I think this would be a good recommendation
>> > for us to make.  It's trivial to keep track of every host/certificate
>> > tuple, just as browsers already keep track of form information.
>> >
>> > serge
>> >
>> > Johnathan Nightingale wrote:
>> >> On 18-Jul-07, at 9:48 AM, Serge Egelman wrote:
>> >>
>> >>> Well, you said that this "is the poster child for exploiting browser
>> >>> state."  For it to be a serious threat that warrants
> consideration, you
>> >>> must assume that most users read certificate data (regardless of
> whether
>> >>> the browser is actually throwing a warning).  If we can assume
> that most
>> >>> users do *not* read this information, then there's a plethora of much
>> >>> easier/likelier attacks.
>> >>>
>> >>> That is, it's a waste of time worrying about how a burglar might pick
>> >>> your fancy new lock when you regularly leave all the windows open.
>> >> Serge,
>> >>
>> >> I might be wrong here, but I think you are talking past each other
>> >> because I think you are misunderstanding Thomas' use of the word
>> >> "exploiting".  His original quote, in response to the discussion about
>> >> using a self-signed cert to facilitate a man in the middle attack, was:
>> >>
>> >>> Isn't this a poster child use case for exploiting browser state?
>> >>> E.g., exploiting the knowledge that a certain domain in connection
>> >>> with HTTPS used to have a CA-based cert, and warning when that
>> >>> changes?
>> >> By which I believe he meant:  "This nicely illustrates why it would be
>> >> useful for browsers to maintain state about prior SSL connections so
>> >> that, in the event - however unlikely - that you visit a site which
> used
>> >> to have a CA-signed cert, but which now instead presents a self-signed
>> >> one, the browser can make all manner of noise/aggressive blockage,
> since
>> >> that scenario is magnificently unlikely for any legitimate bank,
>> >> webstore, etc."
>> >>
>> >> I think he meant "exploiting browser state" as "leveraging browser
> state
>> >> to do good things for users" not "attacking browser state, here's a new
>> >> threat for us to consider."
>> >>
>> >> As I say, maybe I'm wrong, and you're reacting to the idea as I
>> >> (re-)expressed it, but one of us is being tripped up by email-fail,
>> >> because I'm having trouble following your arguments against (what I
>> >> understand to be) his point.
>> >>
>> >> Cheers,
>> >>
>> >> Johnathan
>> >>
>> >> ---
>> >> Johnathan Nightingale
>> >> Human Shield
>> >> johnath@mozilla.com
>> >>
>> >>
>> >>
>> >
>>
>> --
>> /*
>> Serge Egelman
>>
>> PhD Candidate
>> Vice President for External Affairs, Graduate Student Assembly
>> Carnegie Mellon University
>>
>> Legislative Concerns Chair
>> National Association of Graduate-Professional Students
>> */
>>
> 

-- 
/*
Serge Egelman

PhD Candidate
Vice President for External Affairs, Graduate Student Assembly
Carnegie Mellon University

Legislative Concerns Chair
National Association of Graduate-Professional Students
*/
Received on Saturday, 21 July 2007 21:32:47 GMT

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