Pluggable Authentication Module

A pluggable authentication module (PAM) is a mechanism to integrate multiple low-level authentication schemes into a high-level application programming interface (API).

It was first proposed by Sun Microsystems in an Open Software Foundation Request for Comments (RFC) 86.0 dated October 1995.

PAM is currently supported in the AIX operating system, DragonFly BSD,[2] FreeBSD, HP-UX, Linux, macOS, NetBSD and Solaris.

This led to SSO's incorporation as the "primary authentication" portion of the would-be XSSO standard and the advent of technologies such as SPNEGO and SASL.

This lack of functionality is also the reason SSH does its own authentication mechanism negotiation.