pam_guest —
Guest PAM module
[service-name] module-type
  control-flag pam_guest
  [arguments]
The guest service module for PAM allows guest logins. If successful, the
  pam_guest module sets the PAM environment variable
  GUEST to the login name. The application can check
  this variable using
  pam_getenv(3) to
  differentiate guest logins from normal logins.
The following options may be passed to the
    pam_guest module:
  - guests=list
- Comma-separated list of guest account names. The default is
      “guest”. A typical value for
      ftpd(8) would be
      “anonymous,ftp”.
- nopass
- Omits the password prompt if the target account is on the list of guest
      accounts.
- pass_as_ruser
- The password typed in by the user is exported as the
      PAM_RUSERitem. This is useful for applications
      like ftpd(8) where guest users
      are encouraged to use their email address as password.
- pass_is_user
- Requires the guest user to type in the guest account name as
    password.
Thepam_guest module and this manual page were developed
  for the FreeBSD Project by ThinkSec AS and NAI Labs,
  the Security Research Division of Network Associates, Inc. under DARPA/SPAWAR
  contract N66001-01-C-8035 (“CBOSS”), as part of the DARPA CHATS
  research program.