Re: [DNSOP] Resolver behaviour with multiple trust anchors

"Paul Hoffman" <paul.hoffman@vpnc.org> Tue, 31 October 2017 14:42 UTC

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From: "Paul Hoffman" <paul.hoffman@vpnc.org>
To: "Moritz Muller" <moritz.muller@sidn.nl>
Cc: "dnsop@ietf.org" <dnsop@ietf.org>
Date: Tue, 31 Oct 2017 07:42:32 -0700
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Subject: Re: [DNSOP] Resolver behaviour with multiple trust anchors
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On 31 Oct 2017, at 2:39, Moritz Muller wrote:

> Together with my colleagues I have been stumbling upon a, for me, 
> unclear case when validating trust anchors.
>
> Assuming that a resolver has enabled DNSSEC validation and has the 
> root keys configured.
> Additionally, it has configured manually a trust anchor for a TLD 
> (that has also published its DS in the root zone).
> Now, for example due to a key rollover at the TLD, the manually 
> configured trust anchor of the TLD does not match the DS in the root 
> anymore.
>
> How should a resolver treat the signatures of this TLD?
> The resolvers of BIND, Unbound, and PowerDNS seem to treat the 
> signatures of the TLD as bogus, but we didn't find any specifics in 
> RFC 4034 and 4035 that describe how resolvers should behave in this 
> case.
> Knot resolver treats them as NOERROR (according to the developers).
> If we interpret section 4.3 of RFC 4035 then we would have assumed 
> that the signature must be treated as secure.
>
> Did we miss something, or is there indeed clarification needed?

It sounds like clarification is needed if even one (much less three) 
systems treat such a signature as Bogus. My reading of RFC 4035 is that 
any chain that successfully leads to a trust anchor should return 
Secure, even if a different chain returns Bogus.

--Paul Hoffman