I don't understand how you can be so confidently wrong about something so easily checked. :D

> You can't run unix_chkpwd against a local account without root because you won't be able to access /etc/shadow to get the hash.

unix_chkpwd can access /etc/shadow because it is suid.

> Otherwise you have to use the setuid version which won't let you run it directly.

Haha you mean this?

  $ unix_chkpwd
  This binary is not designed for running in this way
  -- the system administrator has been informed

> Perhaps try checking something yourself?

I have. You haven't.

  printf 'hunter2\0' | unix_chkpwd yourusername nullok; echo $?