The cvm-pgsql Module CVM is a framework for validating a set of credentials against a database using a filter program. The modules act as a filter, taking a set of credentials as input and writing a set of facts as output if those credentials are valid.
Optional input is given to the module through environment variables.
This framework places fewer restrictions on the invoking client than checkpassword does, and is much simpler to implement on both sides than PAM and the authmod framework.