Forward zone inside a view

Timothe Litt litt at acm.org
Tue Feb 12 23:34:01 UTC 2019


All these replies are correct in the details (as usual), but miss the point.

Blocking name resolution, while popular, does not meet the OP's requirement:

"The point is I have several desktops that *must* have access **only**
to internal domains.*"

Let's say that your client's favorite illicit site is facebook.com.

One dig (or host) command reveals that:

  facebook.com has address 157.240.3.35
 facebook.com has IPv6 address 2a03:2880:f101:83:face:b00c:0:25de

Fits on scrap of paper.  Carry in to office.  Connect - with a Host
header for http, SNI for TLS, and off you go.  Or just put it in
hosts.txt/hosts.

Or use a public nameserver.   Or...

If you want to block access, you need a firewall.  If you merely want to
inconvenience people or reduce the risk of clicking on ransomware
hyperlinks, mess with their default nameserver.  RPZ is good for that. 
If you have a private address space & need to resolve some names
differently inside and out, views are good for that. (Or you can have a
different nameserver; tastes vary.)  If you are resource limited and
want to benefit from a public server's larger cache, while serving
authoritatively some local names, forwarding can be a good choice.

But "**must** have access **only**" implies that one expects that the
solution should resist *more* than a cooperative or unmotivated client. 
NO DNS-only based solution will do that.

Governments and political pressure groups think that DNS corruption is
an effective tool for limiting access.  People here know better.  It
deters certain casual problem behavior.  It does not prevent anyone with
a modicum of knowledge and determination from watching cat videos.  (Or
downloading malware, or whatever other behavior a policy maker wishes to
ban.)

It is worth listening to the OP's problem statement and steering him
away from illusory technology.  It's the responsible thing to do.

That there are technical answers to the question asked doesn't mean that
it's the right question.  If it's not (and in this case it does not
appear to be), those answers are not helpful.  Even though they are
correct in other contexts.


Timothe Litt
ACM Distinguished Engineer
--------------------------
This communication may not represent the ACM or my employer's views,
if any, on the matters discussed. 

> On 12-Feb-19 17:45, Kevin Darcy wrote:

> Define root zone. 
>
> Delegate teamviewer.com <http://teamviewer.com> from root zone.
>
> Define teamviewer.com <http://teamviewer.com> as "type forward".
>
> "recursion no" is incompatible with *any* type of forwarding or
> iterative resolution. Should only be used if *everything* you resolve
> is from authoritative data, i.e. for a hosting-only BIND instance.
> Since you want to forward -- selectively -- you need "recursion yes".
> Nothing outside of that part of the namespace will be forwarded, since
> named considers everything else to be contained in the root zone.
>
>                                                                      
>           - Kevin
>
> On Mon, Feb 11, 2019 at 9:06 AM Roberto Carna
> <robertocarna36 at gmail.com <mailto:robertocarna36 at gmail.com>> wrote:
>
>     Matus, I've followed whatyou say:
>
>     view "internet" {
>        match-clients { internet_clients; key "pnet"; };
>
>     recursion yes;
>
>     zone "teamviewer.com <http://teamviewer.com>" {
>             type forward;
>             forward only;
>             forwarders {
>                     8.8.8.8;
>             };
>     };
>
>     };
>
>     but clients can resolve ANY public Internet domain, in addition to
>     teamviewer.com....I think "recursion yes" apply to every public
>     domain and not just for "teamviewer.com <http://teamviewer.com>",
>     but I don't know why.
>
>     Please can yoy give me more details, using forward or not, how can
>     let some clients resolve just teamviewer.com
>     <http://teamviewer.com> ??? I confirm that my BIND is an
>     authorittaive name server for internal domains.
>
>     Thanks a lot again.
>
>     El lun., 11 feb. 2019 a las 10:49, Matus UHLAR - fantomas
>     (<uhlar at fantomas.sk <mailto:uhlar at fantomas.sk>>) escribió:
>
>         On 11.02.19 10:38, Roberto Carna wrote:
>         >Dear Mathus, thanks al lot for your help.
>         >
>         >>> what is the point of running DNS server with only two
>         hostnames allowed
>         >>> to resolve?
>         >
>         >The point is I have several desktops that must have access
>         only to internal
>         >domains. The unique exception is they have access to
>         teamviewer.com <http://teamviewer.com>  in
>         >order to download the Teamviewer client and a pair of
>         operations in this
>         >public domain.
>
>         if you disable recursion, any client using that server will
>         only have access
>         to the domains that are configured on that server internally.
>
>         That also means they won't be allowed to contact any internal
>         domains,
>         unless you configure those internal domains on that server.
>         Also no windows updates, nothing.
>
[Snip, message too large]


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