Re: [DNSOP] NSEC/NSEC3 for unsigned zones and aggressive use

Petr Špaček <petr.spacek@nic.cz> Fri, 21 July 2017 08:24 UTC

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Subject: Re: [DNSOP] NSEC/NSEC3 for unsigned zones and aggressive use
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On 19.7.2017 10:50, Francis Dupont wrote:
>  In your previous mail you wrote:
> 
>>  NSEC needs no keys, only their RRSIGs would which wouldn't exist in
>>  unsigned zones. In this case the unsigned NSEC would also not be part of
>>  the zone (it would have to be synthesized and maintained outside the
>>  zone).
> 
> => but it is created by an authoritative server, isn't it?
> And as it is synthesized I can't see a good reason to use NSEC3 instead.
> 
>>  Because an unsigned/unauthenticated NSEC/NSEC3 has the potential to nix
>>  entire zones, when it was discussed, Mark Andrews suggested that
>>  requiring DNS COOKIE to further reduce the chance of cache poisoning
>>  (more than source port randomization and random message ID) could be a
>>  reasonable idea to think about.
> 
> => it adds a nonce so another (short) bunch of unpredictable bits.
> As NSEC is not signed it is more than vulnerable to on-the-path attacks.
> I am afraid it is first a massive zone destruction weapon and after
> perhaps an optimization...

Oh yes, very good point Francis. Let me repeat that I'm against this
proposal.

Petr Špaček  @  CZ.NIC

> 
>>  > It seems easier to remember that DNSSEC offers proofs for denial of
>>  > existence.
> 
> => still applies...
> 
> Regards
> 
> Francis.Dupont@fdupont.fr
> 
> PS: really if this is deployed I can see more "interesting" ways for misuses
> than real benefits. Of course it can be a mean to make zone managers