[dnsdist] dnsdist 1.7 : allow only A request

[david.neau at orange.com]

Hello all

After some tests I see a potential issue, tell me if I m right please :

It works for A request :
[root at node ~]# dig a www.toto.com @X.X.X.X +short
2.2.2.2

It stays mute more most of the requests ( expected behavior ), ^C is needed to get the prompt back.

[root at node ~]# dig ns www.toto.com @X.X.X.X
^C
[root at node ~]# dig mx www.toto.com @X.X.X.X
^C
[root at node ~]# dig soa www.toto.com @X.X.X.X
^C
[root at node ~]# dig txt www.toto.com @X.X.X.X
^C

BUT : for the "any" request I have this result, and I don't know if it can produce something bad, have you any idea ?

[root at node ~]# dig any www.toto.com @X.X.X.X
;; communications error to X.X.X.X#53: end of file
;; communications error to X.X.X.X#53: end of file

Thanks and regards
/d


Orange Restricted

-----Message d'origine-----
De : NEAU David DTSI/PFS 
Envoyé : lundi 13 mars 2023 14:39
À : Jacob Bunk Nielsen <jbn at one.com>; dnsdist at mailman.powerdns.com
Objet : RE: [dnsdist] dnsdist 1.7 : allow only A request

Hello Jacob,

I did this :

addAction(
        NotRule (
                OrRule {QTypeRule(DNSQType.A), QTypeRule(DNSQType.AAAA)}
                ),
        AllowAction()
)

And it works as expected :

> showRules()
#   Name                             Matches Rule                                                     Action
0                                          0 !((qtype==A) || (qtype==AAAA))                           allow

Thanks for your help

Regards
/d


Orange Restricted

-----Message d'origine-----
De : dnsdist <dnsdist-bounces at mailman.powerdns.com> De la part de Jacob Bunk Nielsen via dnsdist Envoyé : lundi 13 mars 2023 06:41 À : dnsdist at mailman.powerdns.com Objet : Re: [dnsdist] dnsdist 1.7 : allow only A request

On 10/03/2023 09.21, david n via dnsdist wrote:
> I tried to explicitly deny the most current DNS requests like for ex :
>
> -- refused query type :
> 	addAction(QTypeRule(dnsdist.ANY), DropAction())
> 	addAction(QTypeRule(dnsdist.SOA), DropAction())

With dnsdist 1.4 (as far as I remember) those names for the various query types changed, so dnsdist.ANY became DNSQType.ANY.

For your particular case of only wanting to serve A and AAAA records I would probably just do (untested):

addAction(
NotRule(OrRule({QTypeRule(DNSQType.A),QTypeRule(DNSQType.AAAA)})),
RCodeAction(DNSRCode.REFUSED))

With all the warnings that Stephane already gave you about why this is a bad idea.

You can replace RCodeAction(DNSRCode.REFUSED) with DropAction() if you don't even want to reply with a REFUSED response.

Best regards,

Jacob


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