Re: [DNSOP] New Version Notification for draft-wessels-dns-zone-digest-01.txt

Evan Hunt <each@isc.org> Fri, 27 July 2018 04:04 UTC

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Date: Fri, 27 Jul 2018 04:04:06 +0000
From: Evan Hunt <each@isc.org>
To: Davey Song <songlinjian@gmail.com>
Cc: shuque@gmail.com, steve@shinkuro.com, dnsop <dnsop@ietf.org>, mweinberg=40verisign.com@dmarc.ietf.org
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Subject: Re: [DNSOP] New Version Notification for draft-wessels-dns-zone-digest-01.txt
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On Fri, Jul 27, 2018 at 11:24:33AM +0800, Davey Song wrote:
> The draft says zone digest is not for protecting zone transmition.

Where did it say that? I didn't notice it.

> IMHO, the treat model is  MITM attack by malicious editing on on-disk
> data (NS and glue especially) and server the new zone to end user. DNS
> digest intends to enable end users (resolvers)  automatically detect the
> modifation ( and drop the zone?).

I don't think that's entirely correct.

Normal resolvers don't need to transfer in a full zone; they just send
queries for individual records and validate RRSIGs. There's no zone for
for it to check against ZONEMD, or for it to drop if the check fails.

However, a resolver configured with a local copy of the root zone as in RFC
7706 *does* contain the full zone, and has to get it somehow.  Perhaps it
gets it via AXFR, perhaps via some out-of-band mechanism. Either way, once
the local copy is obtained, ZONEMD allows it to be verified.

So, yes, ZONEMD does protect zone transmission. It does so regardless of
channel - TLS, AXFR/IXFR, sneakernet, whatever.

-- 
Evan Hunt -- each@isc.org
Internet Systems Consortium, Inc.