Easy pg_hba.conf question.

I want to add a line in a pg_hba.conf file so that the user 'auser' can
connect to the database 'aDB' via host based authentication: so far for
the line I have:

host       aDB  134.117.76.10  255.255.255.255      md5


However, I'm not sure how to specify only 'auser' can connect to the
database.

Thanks for your help,
Robert Young