pam_userpass is a PAM module for use specifically by
services implementing non-interactive protocols and wishing
to verify a username/password pair. It uses Linux-PAM
binary prompts to make it possible for applications to no
longer make the flawed assumption that
PAM_PROMPT_ECHO_ON requests the username and
PAM_PROMPT_ECHO_OFF requests the password. It doesn't
perform any actual user authentication; that is left up to
further modules in the PAM stack (e.g., to pam_tcb or
pam_unix).