Re: [TLS] WGLC: draft-ietf-tls-dnssec-chain-extension-04

Shumon Huque <> Tue, 04 July 2017 16:36 UTC

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From: Shumon Huque <>
Date: Tue, 4 Jul 2017 12:35:54 -0400
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Subject: Re: [TLS] WGLC: draft-ietf-tls-dnssec-chain-extension-04
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On Tue, Jul 4, 2017 at 12:14 PM, Viktor Dukhovni <>;

> > On Jul 4, 2017, at 11:33 AM, Shumon Huque <>; wrote:
> >
> > Yes, in fact the previous sentence to the one you quoted did say this
> more or less: " ... return a serialized authentication chain in the
> Certificate message associated with the end entity certificate being
> validated ". I would propose rewording that a bit and removing the last
> quoted sentence entirely:
> >
> >    Servers receiving a "dnssec_chain" extension in the ClientHello, and
> >    which are capable of being authenticated via DANE, SHOULD return a
> >    serialized authentication chain in the extension block of the
> Certificate
> >    message containing the end entity certificate being validated, using
> the
> >    format described below.
> Why the end-entity certificate, and not the final certificate
> sent by the server?  With anything but DANE-EE(3) the TLSA
> records can't be processed against the server's certificate
> message until *all* the server certificates have been received.

I'm not in principle opposed, but intuitively it makes most sense to
associate the DNSSEC chain with the certificate being validated.

The other logical place this might have been placed is  Encrypted
Extensions. But that again precedes the Certificate message, so doesn't
address your buffering up concern.

Also if DANE-EE turned out to be the common use case, it helps right? Cause
the validator doesn't care about the rest of the certificate chain, and can
authenticate the EE cert right away.

> So instead of squirreling away the DNS data while waiting for
> all the server certificates to arrive, it may make more sense
> to receive the TLSA records (and associated signatures, CNAMEs,
> DNAMEs, ...) once all the server certificates have been received.
> Of course either way one still buffers all the server certificates,
> so buffering the TLSA records is not a major issue.  It's just that
> I don't see a compelling argument for sending the TLSA records with
> the EE certificate.  Perhaps send them with any of the server
> certificates, it probably makes no difference which...

Ok. Let's see if anyone else chimes in with opinions on this ..

Shumon Huque