Re: [DNSOP] [Ext] Re: Resolver behaviour with multiple trust anchors

Petr Špaček <> Mon, 06 November 2017 10:25 UTC

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From: Petr Špaček <>
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Date: Mon, 06 Nov 2017 11:25:15 +0100
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Subject: Re: [DNSOP] [Ext] Re: Resolver behaviour with multiple trust anchors
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On 1.11.2017 12:11, Edward Lewis wrote:
> On 10/31/17, 20:50, "DNSOP on behalf of Mark Andrews" < on behalf of> wrote:
>> Secondly doing deepest match on trust anchors is the only secure way to prevent a parent overriding the child zone's security policy.

Even though Knot Resolver implements "use any" (DS or trust anchor,
whichever matches), I think we should move to "deepest match on trust
anchors", i.e. I agree with Mark.

"Use any" strategy is insecure and will surprise people, as ilustrated
by reaction from Edward quoted below:

> By this, do you mean choice of cryptographic algorithm and/or length?
> To achieve "independence" in this way, the child can simply refuse to
> have a DS record at the parent and then lean on managing trust anchors
> at all relying resolvers.

With current implementation of "use any" nothing prevents the parent
from publishing a DS and thus hijacking the domain without clients
noticing even if there was a local TA installed for given subdomain on

For this reason I propose to document that "deepest match" is mandated

Petr Špaček  @  CZ.NIC