A modern, updated version of this software can be found here: Secure NFS and NIS via SSH Tunnel
This code allows you to proxy SunRPC services over TCP. This includes NFS, which has traditionally been very hard to proxy (even in its TCP form - it still uses random port numbers and makes several connections for mounting, locking, etc.).
Download the source code: sec-rpc.tar.gz
This code was originally written by Holger Trapp. According to the documentation, this version dates from 26th Feb 1996.
I modified it to add support for autobuild, and to allow RPMs to be built from it.