Re: [TLS] Secdir last call review of draft-ietf-tls-exported-authenticator-09

Benjamin Kaduk <bkaduk@akamai.com> Mon, 18 November 2019 22:50 UTC

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Date: Mon, 18 Nov 2019 14:50:35 -0800
From: Benjamin Kaduk <bkaduk@akamai.com>
To: Nick Sullivan <nick=40cloudflare.com@dmarc.ietf.org>
Cc: Yaron Sheffer <yaronf.ietf@gmail.com>, "<tls@ietf.org>" <tls@ietf.org>, draft-ietf-tls-exported-authenticator.all@ietf.org, ietf@ietf.org, secdir@ietf.org
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Subject: Re: [TLS] Secdir last call review of draft-ietf-tls-exported-authenticator-09
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On Sun, Nov 17, 2019 at 04:42:05PM +0800, Nick Sullivan wrote:
> Hi Yaron,
> 
> Thanks for reminding me about the codepoint issue. It's a sticky one.
> 
> As far as I see it, there are three options:
> 
> a) Change the document to UPDATE RFC 8446
> This feels like a heavyweight option and may complicate things since it
> will mean that SNI is allowed but undefined for CertificateVerify in the
> TLS handshake.
> 
> b) Ask for a new extension point for SNI sent in a client-generated
> authenticator request.
> This has the downside of not scaling to future client hello extensions that
> could be useful in exported authenticator requests -- it forces the
> definition of a new code point for each new extension.
> 
> c) Explicitly state that the CertificateRequest-like construction in
> client-generated exported authenticator requests is a new type of message
> (analogous to a ClientHello) and clarify the rules about which extensions
> can be used when it is client-generated (specifically, say that any
> extension supported in CH is allowed)
> This is my preferred solution.

Just to check: this would be adding a new possible value for the "TLS 1.3"
column at https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-values.xhtml#tls-extensiontype-values-1 ?

Thanks,

Ben

> I'm interested to hear what the working group thinks, and I'll happily
> present the options at IETF 106 if there's time.
>