Resolve some hosts thats are dnssec signed differently
Nick Tait
nick at tait.net.nz
Tue Feb 7 07:54:08 UTC 2023
Hi Matthias.
Using a Response Policy Zone on your internal DNS resolver, to change
the answers to DNS queries for your domain from 195.30.95.36 to
192.168.0.1, sounds like the solution that most closely matches what
you've described. Just be aware though, if you have any internal clients
that rely explicitly on DNSSEC (such as a mail server that needs to
apply DANE) then, by default, those queries (that contain DO=1) won't be
rewritten. (See response-policy option, and in particular the
break-dnssec sub-option for more information.)
Another advantage that RPZ has over split-views, is that you don't need
to maintain a separate duplicate zone file.
OTOH if the DNSSEC thing is an issue, you may want to look at other
alternatives, including:
* The split-view thing I mentioned below.
* IP-layer network trickery, such as mangle rules (or similar) so that
the internal machines continue to use the public address, but the
packets don't actually get routed out to the Internet.
Nick.
On 7/02/23 19:45, Matthias Fechner wrote:
> Hi Darren, Hi Nick,
>
> at first thanks a lot for your answer.
> I see that I have not explained my use-case detailed enough.
> I have bind running for domain fechner.net, but not at home and this
> server I think is here completely out of discussion.
> If I must not touch it, I do not want to touch it as it would see the
> traffic from my local computer from home like any other computer in
> the internet and I do not want to open it in any way and it should not
> know the setup of my local network at home.
>
> At home I have a bind running. It serves some local zones I use here
> internally and is forwarding all requests to the DNS server my
> provider is providing.
> It is not connected in any way to my bind servers running for domain
> fechner.net.
>
> The public IP address (idefix.fechner.net) is due to this routing, NAT
> and openvpn not visible on any of my interfaces on my home server.
>
> So if I would like to access idefix.fechner.net it makes a DNS lookup
> which returns the A record for idefix.fechner.net and it sees it does
> not belong to my interface so it uses the default gateway to go to my
> internet provider. It reaches my server in the internet, is routed
> into the openvpn tunnel and goes through my local firewall through a
> policy based NAT to a local IP (192.168.200.x). So you see that is not
> very efficient.
>
> My idea was to hook into the DNS and make sure to not return the IPv4
> address 195.30.95.36, but 192.168.0.1 (as all my devices at home are
> using my local bind here for lookup).
>
> I hope that explain it better what I would like to solve.
>
> Matthias
>
> Am 07.02.2023 um 07:48 schrieb Nick Tait via bind-users:
>>
>> Hi Matthias.
>>
>> It isn't clear whether the issue you're trying to solve is (a)
>> avoiding DNS resolution going out then in to get to your
>> authoritative servers, or (b) with resolved addresses of your servers
>> being the public address which means that data packets sent to/from
>> those servers are going out then in to get to them?
>>
>> It looks like Darren has assumed (a)? If that is correct then it is
>> worth noting that using forwarders like this will require your
>> authoritative servers to answer recursive queries. If that is
>> undesirable, you might want to look at using "mirror" zones on your
>> recursive resolvers? I haven't personally used zones of this type,
>> but according to the documentation, this has following advantage over
>> using "secondary" zones to achieve the same thing: /Answers coming
>> from a mirror zone look almost exactly like answers from a zone of
>> type //|secondary|//, with the notable exceptions that the AA bit
>> (“authoritative answer”) is not set, and the AD bit (“authenticated
>> data”) is./
>>
>> However I suspect your issue is actually (b), in which case I'd
>> suggest using views to serve two versions of your zone file - one
>> with public IP addresses that is served to external clients, and one
>> with private IP addresses that is served to internal clients only,
>> along the lines of the following:
>>
>> # View containing zone with public IP addresses.
>> view "public" {
>> match-clients { ... };
>>
>> zone "fechner.net" {
>> type primary;
>> file "../master/fechner.net/*public-*fechner.net";
>> dnssec-policy "one-year-zsk";
>> inline-signing yes;
>> };
>> };
>>
>> # View containing zone with private IP addresses.
>> view "private" {
>> match-clients { ... };
>>
>> zone "fechner.net" {
>> type primary;
>> file "../master/fechner.net/*private-*fechner.net";
>> dnssec-policy "one-year-zsk";
>> inline-signing yes;
>> };
>> };
>>
>> The two copies of the zone are signed using the same keys.
>>
>> For the sake of simplicity I've glossed over the details of
>> replicating the two different copies of the zone to your secondary
>> DNS servers, but the general idea is to have the secondaries use
>> different TSIG signatures for transferring each copy, and have the
>> "match-clients" use the TSIG key to figure out which view they are
>> talking to. Let me know if you need more info about how to set this up?
>>
>> Nick.
>>
>>
>> On 6/02/23 01:08, Darren Ankney wrote:
>>> Matthias,
>>>
>>> This is what I did to force my resolver bind instance to lookup my
>>> internal domain directly on my authoritative bind instance without
>>> asking any other servers (would have failed anyway as it is a fake
>>> domain "mylocal"):
>>>
>>> // on resolver (or caching name server)
>>> zone "mylocal" {
>>> type forward;
>>> forwarders {
>>> 192.168.40.142; // authoritative server 1
>>> 192.168.40.182; // authoritative server 2
>>> };
>>> forward only; // don't ask any other server
>>> };
>>>
>>> Not sure if that will break dnssec for you. There are probably other
>>> way(s) to accomplish this, especially for a real domain on real IP
>>> address(s). But maybe its somewhere to start.
>>>
>>> -Darren
>>>
>>> On Sun, Feb 5, 2023 at 1:21 AM Matthias Fechner<idefix at fechner.net> wrote:
>>>> Dear all,
>>>>
>>>> I have a question regarding a setup I use at home.
>>>> It is for domain idefix.fechner.net.
>>>>
>>>> I have at home a small server running with some services at it. As I do
>>>> not have a public IP, I tunnel traffic using pf on FreeBSD and openvpn
>>>> to route a public IP to my server at home.
>>>> This works nice but if I now access idefix.fechner.net it will always go
>>>> outside to the internet and then back through the tunnel to my local
>>>> server which is a real performance problem, as the internet connection
>>>> here is really slow.
>>>>
>>>> The complete domain is dnssec signed using the following configuration:
>>>> zone "fechner.net" {
>>>> type master;
>>>> file "../master/fechner.net/fechner.net";
>>>> dnssec-policy "one-year-zsk";
>>>> inline-signing yes;
>>>> };
>>>>
>>>> Now I want to make sure if I access idefix.fechner.net that it does not
>>>> use the tunnel but access it directly using the local address.
>>>>
>>>> So the idea was to configure my named running at home to resolve some
>>>> host names differently.
>>>>
>>>> What is here recommended best practice doing it?
>>>>
>>>> Just added a new domain fechner.net and overwrite some A records? I
>>>> think that will break dnssec or?
>>>>
>>>> Thanks for any pointer into the right direction.
>>>>
>>>> Gruß
>>>> Matthias
>>>>
>>>> --
>>>>
>>>> "Programming today is a race between software engineers striving to
>>>> build bigger and better idiot-proof programs, and the universe trying to
>>>> produce bigger and better idiots. So far, the universe is winning." --
>>>> Rich Cook
>>>>
>>>> --
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>
> Gruß
> Matthias
>
> --
>
> "Programming today is a race between software engineers striving to
> build bigger and better idiot-proof programs, and the universe trying to
> produce bigger and better idiots. So far, the universe is winning." --
> Rich Cook
>
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