checkpassword-pam is an implementation of checkpassword-compatible authentication program.
The checkpassword interface is described here: http://cr.yp.to/checkpwd.html
You could use the checkpassword-pam together with:
checkpassword-pam(8) manual page. README. NEWS.
Version 1.00rc is available for download from the project page.
Source repository is hosted at http://github.com/squadette/checkpassword-pam/tree/master.
The checkpassword-pam project is being hosted on
SourceForge.net.