null-user authentication

[Steve French]

Anyone remember whether with null-user authentication it is important to 
send an encrypted password length of 0 (or whether it is simply ok to 
encrypt a password of "\0" normally)?

cifs vfs currently sends non-zero length encrypted password - no matter 
what the username.

I did not see an smb.conf option that would require the client to use 
null-user authentication but based on the users who have asked for the 
change to allow "username=" (null user) presumably there is such a case.