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Re: [TLS] Security review of TLS1.3 0-RTT

Ilari Liusvaara <ilariliusvaara@welho.com> Sat, 20 May 2017 09:33 UTC

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Date: Sat, 20 May 2017 12:33:47 +0300
From: Ilari Liusvaara <ilariliusvaara@welho.com>
To: Colm MacCárthaigh <colm@allcosts.net>
Cc: Eric Rescorla <ekr@rtfm.com>, "tls@ietf.org" <tls@ietf.org>
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Subject: Re: [TLS] Security review of TLS1.3 0-RTT
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On Fri, May 19, 2017 at 01:10:29PM -0700, Colm MacCárthaigh wrote:
> On Fri, May 19, 2017 at 11:40 AM, Ilari Liusvaara <ilariliusvaara@welho.com>
> wrote:
> 
> > > * In order to fully reason about when that message may later get
> > received,
> > > there needs to be an agreed upon time-cap for 0-RTT receipt. Agreed by
> > all
> > > potential middle-boxes in the pipe that may be using 0-RTT.
> >
> > Isn't that potentially multi-party problem if middleboxes are involved?
> >
> 
> Yes; but if we can agree on a hard maximum time-window for the 0RTT
> section, and all of the parties agree, it's possible for a careful client
> to negotiate its way around it. Even if it's 10 seconds, this still has
> some value I think.

I meant what prevents the (say 10 second) windows from stacking up into
(say 20 second windows) if 0-RTT is used on multiple hops (client-
middlebox and middlebox-server)?

One can not assume that the client has knowledge of any middlebox on
the path (e.g. CDNs in HTTP are in general invisible to the client).


-Ilari

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