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Selective DNS Caching/Forwarding

Posted by ryuzaki0 on from the resolve-only-what-you-want-it-to dept.

MaestroRC asks: "I've been looking around online, and I have found several people wanting to do the same thing, but no one seems to have figured it out yet. What I am wanting to do (and before you go further, understand this is for work, i.e.: no innocent people will be harmed in the implementation) is to set up a name server that selectively forwards queries. For example, I would like to create a list of acceptable domains (less than 20) using wildcards such as *.google.com, that the name server will forward a query on to and reply to normally. For anything not in the list, I want it to reply NXDOMAIN or some such. I've looked at BIND, and there doesn't appear to be a way to do what I'm wanting; it can either have recursion on or off, and any specific zones of type forward still do not forward if it is off. The solution doesn't have to be pretty, and it can just be a simple DNS proxy, but I'm not adept at coding, so it needs to be installable by a regular sysadmin on Linux. Has anyone heard of something like this?"

4 of 61 comments (clear)

  1. Can be done with W2K3 DNS Server... by ErMaC · · Score: 4, Informative

    I'm not a Linux person, but I know a way you could do this with Windows Server 2003 DNS Server...
    It has an option called "conditional forwarding" where you can forward anything ending with "example.com" to the DNS server x.x.x.x - just set up the DNS server and then set conditional forwarding of the domains you want to allow to a real DNS server.
    We use this for setting up trusts between separate Active Directories but it could conceivably be used for this purpose as well.

    --
    "I want to get more into theory, because everything works in theory." -John Cash
    1. Re:Can be done with W2K3 DNS Server... by Phormion · · Score: 5, Informative

      BIND also provides exactly this through forward zones, nothing spectacular here.

  2. Re:Straight to the packet filtering? by arivanov · · Score: 5, Informative

    No need to drop.

    Selectively change the destination name server using DNAT and send it to a fake name server. I use a similar hack for other less nefarious purposes. It used to be (before wireless hotspot ops got inventive) a very good way of supplying roaming clients with a well behaved and working DNS. You set the nameservers in the client to two well known, well behaved nameservers so it works with the VPN down. You also set the firewall/VPN gw to hijack all traffic to these well known nameservers coming down the VPN and direct it to your nameservers. As a result the clients consistently get good DNS after the VPN gets brought up and you do not get any silly split DNS scenarios.

    Alternatively, besides master and slave there are several less known zone types. You should be able to achieve results similar to what you are looking for by using forward or stub type zones. This will give you a "bind-only" solution without playing silly firewall games.

    --
    Baker's Law: Misery no longer loves company. Nowadays it insists on it
    http://www.sigsegv.cx/
  3. Re:BIND can kind of do what you want. So can perl. by dmayle · · Score: 4, Informative

    Forget the whole 127.0.0.1 game playing, this is VERY simple with BIND

    Simply create zones for the domains you want to forward on to be looked up as type forward and disable the "." zone

    And since when did Ask Slashdot become an IT troubleshooting forum?