rbldnsd and DNSSEC compatibility issues - any suggestions?

Mark Andrews marka at isc.org
Thu Sep 10 23:37:43 UTC 2020


.local is for mDNS (RFC 6762).  Do not use it for other purposes as you are hijacking the namespace.

The best solution is to NOT change the name of the zones from those that you use publicly.  That way they have the correct DNSSEC chain of trust down from the root.  If you want to use different zone names then create delegations to empty unsigned zones (SOA and NS records only) like those done for 10.IN-ADDR.ARPA in a zone you control.  That breaks the DNSSEC chain of trust at the delegation point.  If you later decide you want to sign these zones you can do so and link them into the DNSSEC chain of trust.  Just sign both the rbldsnd-formatted files and the empty zones.

If you absolutely must continue to hijack the .local namespace, which is allocated for a different purpose, then add validate-except entries to named.conf

Mark

> On 11 Sep 2020, at 01:56, Rob McEwen <rob at invaluement.com> wrote:
> 
> I manage an anti-spam DNSBL and I've been running into an issue in recent years - that I'm FINALLY getting around to asking about. I just joined this list to ask this question. Also, I checked the archives, but couldn't find an answer - at least, not one I understood.
> 
> So basically, while most of our users do direct queries and don't have this issue - some of our larger subscribers RSYNC the rbldsnd-formatted files, and then they typically run rbldnsd on the same server as their BIND server that is answering their DNSBL queries. Then, their invaluement zone names will all end with "invaluement.local". Typically, their RBLDNSD server is set up to listen on 127.0.0.2 - and then they use BIND for answering their DNSBL queries, and so they tell BIND to get its answers for THOSE invaluement dnsbl queries by doing a DNS forwarder, telling bind to get the answers for THOSE zones from 127.0.0.2 - as shown below:
> 
> zone "invaluement.local" in {
>   type forward;
>   forward only;
>   forwarders { 127.0.0.2; };
> };
> 
> This works perfectly - so long as DNSSEC is turned off. And since most of our subscribers are running a dedicated instance of BIND that is ONLY used for DNSBL queries, they don't mind turning DNSSEC off.
> 
> But, occasionally, we have a customer who cannot turn DNSSEC off. So I was hoping that THIS command would work:
> 
> dnssec-must-be-secure "invaluement.local" no;
> 
> But it doesn't seem to be helping at all. Is that command suppose to disable DNSSEC checking for a particular zone? If yes, what did I do wrong? If not, what does "dnssec-must-be-secure" set to "no" do?
> 
> I've heard that there is NOT a way to get this to work - and that such subscribers much use DNS Delegation, instead. But I really wish         this could be done by simply turning off DNSSEC for a particular zone. That could be useful for MANY various types of internal zones that need this. But if this is that case, how would that DNS Delegation look, to get the above forwarding example to work using delegation instead?
> 
> Thanks in advance for your help!
> 
> -- 
> Rob McEwen, invaluement
>  
> 
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka at isc.org



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