Re: [dnsext] caches, validating resolvers, CD and DO

Mark Andrews <marka@isc.org> Wed, 30 March 2011 08:09 UTC

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To: Paul Vixie <vixie@isc.org>
From: Mark Andrews <marka@isc.org>
References: <20110330062335.BA8C9DAC3C4@drugs.dv.isc.org> <0CAE569785C163CFE87B957E@nimrod.local><46410.1301468733@nsa.vix.com>
In-reply-to: Your message of "Wed, 30 Mar 2011 07:05:33 -0000." <46410.1301468733@nsa.vix.com>
Date: Wed, 30 Mar 2011 19:10:29 +1100
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Cc: dnsext@ietf.org
Subject: Re: [dnsext] caches, validating resolvers, CD and DO
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In message <46410.1301468733@nsa.vix.com>om>, Paul Vixie writes:
> > Date: Wed, 30 Mar 2011 07:42:32 +0000
> > From: Alex Bligh <alex@alex.org.uk>
> > ...
> > Why "should"? Effectively the validating resolver is handing off
> > DNSSEC validation to the upstream server here isn't it? ...
> 
> i loved it when dan kaminsky said, i'm not going to trust the starbucks
> resolver to introduce me to my bank.  so, to the above, no.  a validating
> resolver has a trust anchor (probably the root key and RFC5011 support)
> and is going to be setting CD and doing its own crypto.

DO=1 is ALL you require to do your own authentication 99.99999999%
of the time.

CD=1 is ONLY needed when the upsteam is doing DNSSEC and its concept
of the current time and/or its set of trust anchors differ to yours.

CD=1 doesn't help you when the upstream is treating the zone the
answer comes from as insecure.

CD=0 DOES NOT mean you are not authenticating.

A validating resolver with direct access to the athoritative servers
can work around a number of operational errors by being able to
retry the query with different servers.

A validating resolver behind a cache does not have this recovery
path.  The EDNS option is designed to give it that recovery path.

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Mark Andrews, ISC
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PHONE: +61 2 9871 4742                 INTERNET: marka@isc.org