CDNSKEY / CDS for key is now published - but why?
Matthijs Mekking
matthijs at isc.org
Wed Oct 2 11:10:04 UTC 2024
Hi Danilo,
When you enable DNSSEC for the first time, first the DNSKEY and the
signatures need to be introduced in the zone, and propagated to the
world. The propagation depends on the TTL values, and these are derived
from the dnssec-policy configuration. By default it takes more than a
day because of max-zone-ttl is set to 86400.
Only then it is fully safe to publish the DS, so at that point BIND will
publish the CDS/CDNSKEY records.
Note that this long delay is only when you enable DNSSEC, key rollovers
only need to take the DNSKEY TTL into account (plus some safety and
propagation values).
So you submitted the DS too soon. Luckily the delay on the first sign is
pretty conservative and your zones appear to be fine after publishing
the DS. But in an automated way (CDS polling), the DS would have been
submitted later than you did.
Three more comments:
1.
> I thought that Bind checks the DS on the parent and only publishes
CDS > / CDNSKEY if DS doesn't exist or is in some way different.
No. The CDS/CDNSKEY RRset is published and won't be removed from the zone.
The RFC says that when the Parent DS is in sync with the CDS/CDNSKEY
RRset, the Child DNS Operator MAY delete the CDS/CDNSKEY RRset.
We chose not to do so, because it can be handy to see what the DS
records in the parent should be given what CDS/CDNSKEY RRset is
published in the child zone.
2.
Depending on your configuration, BIND will check if the DS is actually
in the parent zone. If it does not, you have to check it manually and
tell BIND with the 'rndc dnssec -checkds' command. Otherwise, the DS may
stay in the "Rumoured" state indefinitely, and this can influence future
key rollovers.
3.
You can use the options 'cds-digest-types' and 'cdnskey' to set what
RRsets need to be published.
Hope this helps, best regards,
Matthijs
On 10/2/24 12:42, Danilo Godec via bind-users wrote:
> Hi Greg,
>
> thanks for the answer.
>
> I knew that CDS and CDNSKEY are just in my own zone and (as far as I
> understand), serve to inform the parent DNS about (upcoming?) changes in
> DS / DNSKEY records. I'm not quite sure about establishing the initial
> trust with the parent, but as our ccTLD parent DNS doesn't support CDS /
> CDNSKEY it's not a big deal anyway.
>
>
> What I don't understand is why Bind published CDS / CDNSKEY just for one
> of two very similar domains? Initially I thought that Bind checks the DS
> on the parent and only publishes CDS / CDNSKEY if DS doesn't exist or is
> in some way different.
>
>
>
> Regards,
>
> Danilo
>
>
>
> On 2. 10. 24 12:19, Greg Choules wrote:
>> Hi Danilo.
>> The CDS and CDNSKEY are published in your own zone, not anywhere else.
>> You can confirm this by doing a dig for them directly, or AXFR if you
>> permit transfers on your server.
>>
>> They are intended for use with registrars that *do* support automatic
>> DS creation using one of them. If yours doesn't and you already
>> published your DS in the parent, then no big deal. The CDS and CDNSKEY
>> will just sit in your zone and you don't have to do anything with them.
>>
>> Does that help?
>> Cheers, Greg
>>
>> On Wed, 2 Oct 2024 at 10:58, Danilo Godec via bind-users
>> <bind-users at lists.isc.org> wrote:
>>
>> Hi all,
>>
>> yesterday I filled my day fiddling with DNSSEC for a couple of my
>> test domains - both have been signed 'manually' before, but I
>> haven't published the DS record.
>>
>>
>> So yesterday I setup both for dnssec-policy, while also changing
>> the signing algorithm and keys (basically started from scratch):
>>
>> dnssec-policy "nsec3_no_rotate" {
>> keys {
>> ksk key-directory lifetime unlimited algorithm 13;
>> zsk key-directory lifetime unlimited algorithm 13;
>> };
>> nsec3param iterations 0 optout false;
>> };
>>
>> ...
>>
>> zone "sociopat.si <http://sociopat.si>" {
>> type master;
>> file "master/Danci/sociopat.si.hosts";
>> key-directory "master/Danci/keys";
>> dnssec-policy "nsec3_no_rotate";
>> inline-signing yes;
>> };
>>
>> zone "psihopat.si <http://psihopat.si>" {
>> type master;
>> file "master/Danci/psihopat.si.hosts";
>> key-directory "master/Danci/keys";
>> dnssec-policy "nsec3_no_rotate";
>> inline-signing yes;
>> };
>> ...
>>
>>
>> I published DS records through my registrar and after a couple of
>> hours all seemed fine - both Verisign dnssec-analyzer and DNSViz
>> show no errors or warnings for them.
>>
>>
>> However, today bind logged this:
>>
>> named[17379]: general: info: CDNSKEY for keysociopat.si/ECDSAP256SHA256/61220 <http://sociopat.si/ECDSAP256SHA256/61220> is now published
>> named[17379]: general: info: CDS for keysociopat.si/ECDSAP256SHA256/61220 <http://sociopat.si/ECDSAP256SHA256/61220> is now published
>>
>>
>> I'm pretty sure this is not bad or wrong, but I would like to
>> sort-of understand, why Bind decided it needs to publish CDS /
>> CDNSKEY for this one and not the other one, given that DS records
>> are published in ccTLDs:
>>
>> # dig dssociopat.si <http://sociopat.si>
>> ;; QUESTION SECTION:
>> ;sociopat.si <http://sociopat.si>. IN DS
>>
>> ;; ANSWER SECTION:
>> sociopat.si <http://sociopat.si>. 5826 IN DS 61220 13 2 D8C1553B3D6BCF7A704A3D821069F57B6946DCA1D198D303E3B4C730 616F92AD
>>
>>
>> # dig dspsihopat.si <http://psihopat.si>
>>
>> ;; QUESTION SECTION:
>> ;psihopat.si <http://psihopat.si>. IN DS
>>
>> ;; ANSWER SECTION:
>> psihopat.si <http://psihopat.si>. 7200 IN DS 7162 13 2 3C5A5625F848DBCF99A0B85017AFE04FD1F681037B61BE970D57AE9F 90F21CD8
>>
>>
>> Also, as far as I know, .si DNS servers don't support CDS /
>> CDNSKEY, so publishing them might be futile.
>>
>>
>> Regards,
>>
>> Danilo
>>
>>
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>
>
> Lep pozdrav / Best regards,
> --
> Danilo Godec | Sistemska podpora / System Administration
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> E: danilo.godec at agenda.si | T: +386 (0)2 421 61 31
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