Re: [TLS] tls 1.3: renegotiation

Martin Thomson <martin.thomson@gmail.com> Mon, 28 July 2014 21:17 UTC

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Date: Mon, 28 Jul 2014 14:17:46 -0700
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From: Martin Thomson <martin.thomson@gmail.com>
To: Robert Ransom <rransom.8774@gmail.com>
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Subject: Re: [TLS] tls 1.3: renegotiation
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On 25 July 2014 12:27, Robert Ransom <rransom.8774@gmail.com> wrote:
> In addition, I believe that it is not possible for the WG to make an
> informed decision as to whether renegotiation should be removed at
> this time:
>
> * The rekeying feature and client-initiated client authentication
>   feature have not been specified yet, even to the point of stating
>   the requirements which each feature will meet.  It is not possible
>   for the WG to determine whether the features intended to replace
>   these two uses of renegotiation will be fit for their intended
>   purposes at this time.

We had a good discussion about these in Toronto.  On rekeying, there
are concerns about how much we might want to make changeable; offline
discussions about the complexity/value trade-off space between simple
rekeying (as I have proposed) and something more complete like a full
DH exchange was quite enlightening.

We've talked quite a bit about spontaneous client authentication
(though we might talk about client-initiated authentication, that
implies a solution and so I think that is the wrong focus for the
discussion).

The problem as always is that the defense of renegotiation is largely
based on its existence alone.  That defense would be stronger if there
it were based on use cases.  I don't find arguments from inertia ("it
exists", or "it's easy") to be at all persuasive.  Saying "it can be
fixed" is actively detrimental to the case.

Arguments in the form "I need to do X and in order to do X I need
renegotiation" are far better.  They are testable.  Andrei's concerns
are a good example of this.  We might disagree on the subjective
elements, but that's a good starting point.