1. Credential Validation Modules 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. Some of the ideas for CVM came from experience with PAM (pluggable authentication modules), the checkpassword interface used by qmail-pop3d, and the "authmod" interface used by Courier IMAP and POP3. 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. See http://untroubled.org/cvm/cvm.html for more information. From Debian 3.0r0 APT