Re: [DNSOP] Robert Wilton's No Objection on draft-ietf-dnsop-dns-zone-digest-12: (with COMMENT)

Benjamin Kaduk <kaduk@mit.edu> Mon, 12 October 2020 04:07 UTC

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Date: Sun, 11 Oct 2020 21:07:07 -0700
From: Benjamin Kaduk <kaduk@mit.edu>
To: John Levine <johnl@taugh.com>
Cc: dnsop@ietf.org
Message-ID: <20201012040707.GF83747@kduck.mit.edu>
References: <20201010032517.GM89563@kduck.mit.edu> <20201010153411.580CE2336CB2@ary.qy>
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Subject: Re: [DNSOP] Robert Wilton's No Objection on draft-ietf-dnsop-dns-zone-digest-12: (with COMMENT)
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On Sat, Oct 10, 2020 at 11:34:11AM -0400, John Levine wrote:
> In article <20201010032517.GM89563@kduck.mit.edu> you write:
> >There's two general classes of attack to consider: when an external
> >attacker takes an existing ZONEMD and tries to modify the associated zone,
> >or when the zone provider is the malicious entity that wants to provide
> >different content to different people but give them the same digest value ...
>  
> I think there's a third threat, a transcription error due to
> transmission error or other kinds of bitrot. I send zone files between
> my DNS servers over ssh, so the chances of an external attack are low,
> but particularly as zone files continue to grow, the protection of the
> TCP checksum is less effective. On my rather small DNS setup I have a
> 71MB zone and I don't think that's unusual. In many, probably most,
> cases a bit flip or two would produce DNS data that is still valid but
> wrong, e.g., change the address in AAAA or the characters in a name
> anywhere.

At risk of being overly glib, "Murphy is often a very effective attacker".
That is, the analysis for this decomposes into a subset of the first case I
listed.

-Ben

> That's why there are situations where a zone digest can be useful
> even without a DNSSEC validation chain.
> 
> R's,
> John