Asterisk in RRs?

[Chris Buxton]

On Jul 10, 2008, at 1:01 PM, Peter Laws wrote:
> OK, so not *strictly speaking* a BIND question, but y'all are smart  
> people.
> Is a * legal in a resource record?  I'm thinking not, but I can't  
> find a
> canonical source.  I assume it would be in an RFC, but which one?   
> One of
> the oldies from the 1980s?

The asterisk character is special in domain names and is used to  
create wildcard nodes in the namespace. Go back to RFC 1034, sections  
4.3.2 and 4.3.3.

Briefly, the * must be a label unto itself, and it must be the  
leftmost label in the name. It can only appear in the owner name of a  
record, not in the RData. Any other use (in a domain name) is invalid.

The rules for wildcard matching are sometimes a bit counterintuitive.  
However, the RFC lays them out cleanly.

Chris Buxton
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