# man > pam_filter(8)

[PAM_FILTER(8)](https://www.chedong.com/phpMan.php/man/PAMFILTER/8/markdown)                             Linux-PAM Manual                             [PAM_FILTER(8)](https://www.chedong.com/phpMan.php/man/PAMFILTER/8/markdown)



## 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)](https://www.chedong.com/phpMan.php/man/execv/2/markdown) 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)](https://www.chedong.com/phpMan.php/man/pam/3/markdown) 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)](https://www.chedong.com/phpMan.php/man/authenticate/3/markdown) and **pam**___**[setcred**(3)](https://www.chedong.com/phpMan.php/man/setcred/3/markdown), 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)](https://www.chedong.com/phpMan.php/man/session/3/markdown)
           stage, and _run2_ for **pam**___**close**___**[session**(3)](https://www.chedong.com/phpMan.php/man/session/3/markdown).

           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)](https://www.chedong.com/phpMan.php/man/chauthtok/3/markdown) (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)](https://www.chedong.com/phpMan.php/man/pam.conf/5/markdown), [**pam.d**(5)](https://www.chedong.com/phpMan.php/man/pam.d/5/markdown), [**pam**(7)](https://www.chedong.com/phpMan.php/man/pam/7/markdown)

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



Linux-PAM Manual                             06/08/2020                                [PAM_FILTER(8)](https://www.chedong.com/phpMan.php/man/PAMFILTER/8/markdown)