User wanting to use a .local domain to host DNS

btb btb at
Thu Nov 15 16:35:08 UTC 2012

On 2012.11.15 10.14, Novosielski, Ryan wrote:
>> Failing to operate a private TLD correctly is causing internal
>> data leaking to the Internet, which could be a security risk but in
>> all cases is a burden on the root server system.
> Not that I think that I'm doing this (and as I'd said, the only place
> I use this is at home on a NAT'd network where there is no public DNS
> at all), but what are some common ways to let this happen if you
> happen to know?

a nat'd network is a prime example of exactly the sort of place this 
kind of thing happens.  what it usually boils down to is non public 
namespace being used [be it invented tlds or rfc1918/5735/etc address 
space] with no nameserver on the local network with those zones 
configured as authoritative.

for example, someone decides it would be fun to have a play domain name 
on their private network, but doesn't set up a nameserver [aside from 
the simple caching nameserver built into their access device [dsl/cable 
modem, router, whatever]].  naturally, hosts on the network are 
constantly doing dns lookups which reference this domain name, and as 
such, the access device tries to resolve said hostname, likely passing 
the query on to some upstream resolver.  regardless of it a forwarder is 
used or traditional iterative queries are used by the access device, now 
the query ends up getting shopped around in some capacity to various 
nameservers, all on the public internet, to see if it can be resolved.

queries for dns data which will never exist on the public internet 
should never make it beyond the borders of a private network.  running 
an authoritative nameserver with the proper zones loaded [and bind makes 
this even easier with empty zones] is what prevents this from happening. 
  unfortunately, it is exceedingly common, as carsten points out, and in 
some contexts has become bad enough - e.g. rfc1918 arpa space - that 
separate nameservers have been set up to deal with the problem [rfc 6305].


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