Re: [DNSOP] [Ext] future-proofing (Re: Working Group Last Call for: Message Digest for DNS Zones)

Paul Vixie <paul@redbarn.org> Thu, 16 January 2020 02:05 UTC

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To: Michael StJohns <msj@nthpermutation.com>
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From: Paul Vixie <paul@redbarn.org>
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Subject: Re: [DNSOP] [Ext] future-proofing (Re: Working Group Last Call for: Message Digest for DNS Zones)
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Michael StJohns wrote on 2020-01-15 17:28:
> ...  I think its a co-existence issue here.  I don't think you should
> have two different (calculation-wise) ZONEMD-like RRSets in the same 
> zone for the reasons you've mentioned.  I don't think that reserving RR 
> types is the right way of doing things and I'm not sure how you'd write 
> the IANA guidance to cover the later assignment of those type numbers. 
> It's possible that we can tweak this a bit and get around the problem.
> 
> So maybe:
> 
> 1 byte - Scheme - 1 == SIMPLE
> 
> Which has a body of
> 
> 1 byte - digest - 1 == SHA384, a
> 
> followed by N bytes of the appropriate digest length.
> 
> 
> And either "Only one Scheme shall be used per zone.  A receiver shall 
> consider a zone containing multiple schemes as invalid for the purposes 
> of this document".   or "The SIMPLE scheme shall exclude any ZONEMD RR 
> of a non-SIMPLE scheme from the digest calculation for the SIMPLE 
> scheme" or "ZONEMD digest calculations for any scheme shall only include 
> ZONEMD RRs with matching schemes - no placeholder records for non-scheme 
> ZONEMD rrs shall be added to the calculation".
> 
> I think the last of these three is probably the right approach.
+1.

-- 
P Vixie