This man page is largely a transcription of the article by Dag-Erling Smørgrav, [[ https://docs.freebsd.org/en/articles/pam/ | Pluggable Authentication Modules ]].
I did not include the programming examples, or items covered by pam.conf(5).
This is related to [[ https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=63084 | PR 63084 ]].