Re: [DNSOP] draft-fanf-dnsop-trust-anchor-witnesses-00.txt

Tony Finch <dot@dotat.at> Sun, 02 March 2014 12:11 UTC

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Date: Sun, 2 Mar 2014 12:11:25 +0000
From: Tony Finch <dot@dotat.at>
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Subject: Re: [DNSOP] draft-fanf-dnsop-trust-anchor-witnesses-00.txt
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Tony Finch <dot@dotat.at>; wrote:
> Joe Abley <jabley@hopcount.ca>; wrote:
> >
> > I think validation categorically needs to be off until the validator has
> > been bootstrapped (not just for this proposal, but in general). No
> > validation is possible before you have a stable sense of time and a
> > trusted set of local DNSSEC trust anchors. Acting as though you are
> > validating when you can't possibly be seems like a bad idea, since if
> > you can game validators to get stuck in that state you've defeated
> > DNSSEC.
>
> We-e-e-e-ell yes, except that you seem to have missed the fact that a
> witness trust anchor DOES allow you to validate that witness's zone, using
> normal validation logic. It is the combination of multiple witnesses that
> allows you to update the root trust anchor, after which you can validate
> the rest of the DNS. The root-witnesses.arpa zone is carefully designed to
> make it possible to resolve and validate the witnesses when the rest of
> the DNS cannot be validated.
>
> Time is an interesting point.

Sorry, I got distracted by children when writing my previous message...

When establishing the current time, it is necessary to run in a special
validating mode which checks everything except for signature and
certificate validity times. You have to authenticate your time servers,
otherwise you are vulnerable to MitM attack.

Given that, a MitM is able to spoof old signatures from a compromised
witness (say), but that is not enough to compromise the whole process
unless the MitM has a whole quorum of compromised witnesses. Make the
quorum big enough and that will be vanishingly unlikely.

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>;  http://dotat.at/
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