problem with 'pwd_mkdb' when trying to reset user's password to zero value

[Andrey Smagin <andrey@smagin.com>]

Hello.

I created a user anoncvs with adduser and set the password to 'bbb'.
Then I edited the entry with vipw, so it looks like this:

anoncvs::30000:30000::0:0:Anonymous CVS
User:/build/repository/anoncvs:/build/repository/anoncvssh

When I try to ssh from another machine, it asks me for the password
and only password 'bbb' works.

I did 'passwd anoncvs' and changed the password to 'aaa'. Then I used
vipw to reset the password to zero value again. Connecting from
another machine confirms that the password is still 'aaa'.

I deleted user anoncvs (tried it couple times using vipw and userdel
for that). Connecting as anoncvs from another machine now fails and
everything seems to be OK. /etc/master.passwd does not have any
records for anoncvs user.

Final step: I use vipw to add this line back:
anoncvs::30000:30000::0:0:Anonymous CVS
User:/build/repository/anoncvs:/build/repository/anoncvssh

Connecting as anoncvs from another machine reveals that the password
is again 'aaa'! Where did it come from? I tried doing it several
times, tried invoking pwd_mkdb directly and rebooting the machine
several times - that 'aaa' password seems to survive somehow if I add
previously deleted user with empty password.

So, two questions I have now:
How to reset user's password to zero value and what is the proper
way to add a new user with empty password?

It's on i386, -current as of Feb 27. The problem is most likely
between the keyboard and the chair, but I would appreciate if somebody
could confirm that. Thank you.

-- 
Andrey