Editing Pluggable Authentication Module (section)

{{Short description|Flexible mechanism for authenticating users}}
{{refimprove|date=May 2011}}
[[File:PAM Diagramm.svg|thumb|right|Structure]]
A '''pluggable authentication module''' ('''PAM''') is a mechanism to integrate multiple low-level [[authentication]] schemes into a high-level [[application programming interface]] (API). PAM allows programs that rely on authentication to be written independently of the underlying authentication scheme. It was first proposed by [[Sun Microsystems]] in an [[Open Software Foundation]] [[Request for Comments]] (RFC) 86.0 dated October 1995.<ref>[https://www.kernel.org/pub/linux/libs/pam/pre/doc/rfc86.0.txt.gz The Original Solaris PAM RFC]</ref> It was adopted as the authentication framework of the [[Common Desktop Environment]]. As a stand-alone [[open-source]] infrastructure, PAM first appeared in [[Red Hat Linux]] 3.0.4 in August 1996 in the [[Linux PAM]] project. PAM is currently supported in the [[AIX operating system]], [[DragonFly BSD]],<ref>[http://leaf.dragonflybsd.org/cgi/web-man?command=pam&section=ANY PAM manual page of DragonFly BSD]</ref> [[FreeBSD]], [[HP-UX]], [[Linux]], [[macOS]], [[NetBSD]] and [[Solaris (operating system)|Solaris]].

Since no central standard of PAM behavior exists, there was a later attempt to standardize PAM as part of the [[X/Open]] UNIX standardization process, resulting in the '''X/Open Single Sign-on''' ('''XSSO''') standard. This standard was not ratified, but the standard draft has served as a reference point for later PAM implementations (for example, [[OpenPAM]]).