NAME

       pam_filter - PAM filter module

SYNOPSIS

       pam_filter.so [debug] [new_term] [non_term] run1|run2 filter [...]

DESCRIPTION

       This module is intended to be a platform for providing access to all of the input/output
       that passes between the user and the application. It is only suitable for tty-based and
       (stdin/stdout) applications.

       To function this module requires filters to be installed on the system. The single filter
       provided with the module simply transposes upper and lower case letters in the input and
       output streams. (This can be very annoying and is not kind to termcap based editors).

       Each component of the module has the potential to invoke the desired filter. The filter is
       always execv(2) with the privilege of the calling application and not that of the user.
       For this reason it cannot usually be killed by the user without closing their session.

OPTIONS

       debug
           Print debug information.

       new_term
           The default action of the filter is to set the PAM_TTY item to indicate the terminal
           that the user is using to connect to the application. This argument indicates that the
           filter should set PAM_TTY to the filtered pseudo-terminal.

       non_term
           don't try to set the PAM_TTY item.

       runX
           In order that the module can invoke a filter it should know when to invoke it. This
           argument is required to tell the filter when to do this.

           Permitted values for X are 1 and 2. These indicate the precise time that the filter is
           to be run. To understand this concept it will be useful to have read the pam(3) manual
           page. Basically, for each management group there are up to two ways of calling the
           module's functions. In the case of the authentication and session components there are
           actually two separate functions. For the case of authentication, these functions are
           pam_authenticate(3) and pam_setcred(3), here run1 means run the filter from the
           pam_authenticate function and run2 means run the filter from pam_setcred. In the case
           of the session modules, run1 implies that the filter is invoked at the
           pam_open_session(3) stage, and run2 for pam_close_session(3).

           For the case of the account component. Either run1 or run2 may be used.

           For the case of the password component, run1 is used to indicate that the filter is
           run on the first occasion of pam_chauthtok(3) (the PAM_PRELIM_CHECK phase) and run2 is
           used to indicate that the filter is run on the second occasion (the PAM_UPDATE_AUTHTOK
           phase).

       filter
           The full pathname of the filter to be run and any command line arguments that the
           filter might expect.

MODULE TYPES PROVIDED

       All module types (auth, account, password and session) are provided.

RETURN VALUES

       PAM_SUCCESS
           The new filter was set successfully.

       PAM_ABORT
           Critical error, immediate abort.

EXAMPLES

       Add the following line to /etc/pam.d/login to see how to configure login to transpose
       upper and lower case letters once the user has logged in:

                   session required pam_filter.so run1 /lib/security/pam_filter/upperLOWER

SEE ALSO

       pam.conf(5), pam.d(5), pam(7)

AUTHOR

       pam_filter was written by Andrew G. Morgan <morgan@kernel.org>.