mod_auth_pam
PAM stands for Pluggable Authentication Modules,
and is used to configure ways for authenticating users. Now
"authenticating" a user usually means comparing a password they
give with some other information, and returning a "yes/no"-style
answer. PAM does not provide all of the other information for a user,
such as UID, GID, home, and shell. This means that mod_auth_pam
cannot be used, by itself, as an auth module for proftpd;
mod_auth_pam is used to supplement other auth modules by
providing access to PAM's additional authentication checks.
Installation instructions for mod_auth_pam can be found
here.
The most current version of mod_auth_pam can be found in the
ProFTPD source distribution:
http://www.proftpd.org/
<VirtualHost>, <Global>
The AuthPAM directive enables or disables the module's runtime
PAM check. If it is set to off this module does not consult PAM
when authenticating a user.
<VirtualHost>, <Global>
The AuthPAMConfig directive is used to specify the name of
the service used when performing the PAM check; PAM configurations can
vary depending on the service. By default, the "ftp" service
is used. Note that on some platforms, e.g. FreeBSD, this may
need to be set to "ftpd", depending on the PAM configuration
involved.
Here's an example of changing the service used:
<IfModule mod_auth_pam.c>
AuthPAMConfig ftpd
</IfModule>
mod_auth_pam module is automatically included when
proftpd is built on a system that supports PAM. To disable
this automatic inclusion, use the --disable-auth-pam configure
option.