checkpw-1.02 is a simple and flexible checkpassword interface package.
checkpw checks password which is stored in a file in the Maildir directory. The file has read and write permissions to the user only. checkpw checks real user's password. For virtual users, vucheckpw is available as a separate package.
Before invoking following program, checkpw and checkapoppw set up $USER, $EXT, $HOME, $SHELL, its supplementary groups, its gid, its uid, and its working directory.
INSTALL says how to set up.
The code is in the public domain.
The original checkpassword program is written by D.J.Bernstein: http://cr.yp.to/checkpwd.html