[dns-operations] underline in TXT's host

[Fred Morris]

On Fri, 14 Dec 2012, Feng He wrote:
> does the TXT record allow a underline in its hostname?

There is some conflation there. A "hostname" is a particular kind of
label, historically chosen from a limited character set to avoid untoward
interactions with runtime environments. For example, what might occur
running this under bash?:

  dig `rm -rf *`.m3047.net

Properly escaped you could get away with it:

  dig '`rm -rf *`.m3047.net'

Nonetheless it's considered a bad idea to allow labels which could be used
to resolve a host to contain characters which might not be a good idea for
a hostname, and therefore delegating zones should not contain non-hostname
labels in their FQDNs.

However the Domain Name System per se imposes no such restrictions on
labels.


Khazakhstan issued domain names starting with a dash for a limited period
of time... DAMHIK!

--

Fred Morris