Manual: pam_filter

PAM_FILTER(8)					      Linux-PAM Manual					       PAM_FILTER(8)

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 .

Linux-PAM						 07/16/2026					       PAM_FILTER(8)