openssh authentication for non-system users

[Venelin Mihaylov]

Hello,
  I am trying to write an PAM module for openssh, which should
authenticate users using an MySQL database (it is based on pam_mysql).
The problem is that I do not know what is necessary to authenticate
successfully users, which do not have entries in /etc/passwd, for them I
get invalid user :(.
  I will greatly appreciate any info on the matter. I have been pulling
my hair out for almost two days on this, searched google numerous times,
but without any success.
  I also tried to read the source code, but apparently I am not good
enough to comprehend it.

Thank you.
Venelin Mihaylov