Tightened DNS security question re: DNS amplification attacks.

jay at miscreant.org jay at miscreant.org
Tue Jan 27 15:42:39 CST 2009


Quoting Matthew Huff <mhuff at ox.com>:

> Given the recent DNS amplification attacks, I've audit and updated our
> authoritative servers. We are using 9.6.0-P1 now. I've been using the cyrmu
> templates, but one thing I see is that the dns queries to the . hint file
> are still occuring and are not being denied by our servers. For example:
>
> 27-Jan-2009 15:00:22.963 queries: client 64.57.246.146#64176: view
> external-in: query: . IN NS +
> 27-Jan-2009 15:00:23.118 queries: client 64.57.246.146#33146: view
> external-in: query: . IN NS +
>
> the named.conf has:
>
> ...
> ...
> ...
>
> view "external-in" in {
>   match-clients { any; };
>   recursion no;
>   additional-from-auth no;
>   additional-from-cache no;
>
>   zone "." in {
>     type hint;
>     file "db.cache";
>   };
> ...
> ...
>
> since you can't put a "allow-query { none; };" in a hint zone, what can I do
> to deny the query to the . zone file?
>
>
>
> ----
> Matthew Huff       | One Manhattanville Rd
> OTA Management LLC | Purchase, NY 10577
> http://www.ox.com  | Phone: 914-460-4039
> aim: matthewbhuff  | Fax:   914-460-4139
>

Hi Matthew,

I'm using the following with 9.5.1:

view    "external" {
     recursion no;
     allow-query-cache { none; };
     zone "." IN {
         type hint;
         file "/var/named/named.ca";

And my logs indicate that the requests for . IN NS are being denied:

Jan 28 08:40:38 web1 named[12337]: client 64.57.246.146#33453: view  
external: query (cache) './NS/IN' denied
Jan 28 08:40:39 web1 named[12337]: client 67.192.144.0#41794: view  
external: query (cache) './NS/IN' denied

Cheers,

Jay





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