Password authentication through /etc/passwd

I'm in the process of writting a client/server application (purely in C) as a pseudo-frontend to administer various aspects of Debian 2.2 from remote locations over TCP/IP. What libraries do I need to look at in order to allow client authentication against /etc/passwd? Authentication is currently

Password authentication through /etc/passwd

I'm in the process of writting a client/server application (purely in C) as a pseudo-frontend to administer various aspects of Debian 2.2 from remote locations over TCP/IP. What libraries do I need to look at in order to allow client authentication against /etc/passwd? Authentication is currentl