<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="pam_filter">
<refmeta>
<refentrytitle>pam_filter</refentrytitle>
<manvolnum>8</manvolnum>
<refmiscinfo class="source">Linux-PAM</refmiscinfo>
<refmiscinfo class="manual">Linux-PAM Manual</refmiscinfo>
</refmeta>
<refnamediv xml:id="pam_filter-name">
<refname>pam_filter</refname>
<refpurpose>PAM filter module</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis xml:id="pam_filter-cmdsynopsis" sepchar=" ">
<command>pam_filter.so</command>
<arg choice="opt" rep="norepeat">
debug
</arg>
<arg choice="opt" rep="norepeat">
new_term
</arg>
<arg choice="opt" rep="norepeat">
non_term
</arg>
<arg choice="plain" rep="norepeat">
run1|run2
</arg>
<arg choice="plain" rep="norepeat">
<replaceable>filter</replaceable>
</arg>
<arg choice="opt" rep="norepeat">
<replaceable>...</replaceable>
</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 xml:id="pam_filter-description">
<title>DESCRIPTION</title>
<para>
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.
</para>
<para>
To function this module requires <emphasis>filters</emphasis> 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).
</para>
<para>
Each component of the module has the potential to invoke the
desired filter. The filter is always
<citerefentry>
<refentrytitle>execv</refentrytitle><manvolnum>2</manvolnum>
</citerefentry> with the privilege of the calling application
and <emphasis>not</emphasis> that of the user. For this reason it
cannot usually be killed by the user without closing their session.
</para>
</refsect1>
<refsect1 xml:id="pam_filter-options">
<title>OPTIONS</title>
<para>
<variablelist>
<varlistentry>
<term>
debug
</term>
<listitem>
<para>
Print debug information.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
new_term
</term>
<listitem>
<para>
The default action of the filter is to set the
<emphasis>PAM_TTY</emphasis> item to indicate the
terminal that the user is using to connect to the
application. This argument indicates that the filter
should set <emphasis>PAM_TTY</emphasis> to the filtered
pseudo-terminal.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
non_term
</term>
<listitem>
<para>
don't try to set the <emphasis>PAM_TTY</emphasis> item.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
runX
</term>
<listitem>
<para>
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.
</para>
<para>
Permitted values for <emphasis>X</emphasis> are
<emphasis>1</emphasis> and <emphasis>2</emphasis>. These
indicate the precise time that the filter is to be run.
To understand this concept it will be useful to have read
the <citerefentry>
<refentrytitle>pam</refentrytitle><manvolnum>3</manvolnum>
</citerefentry> manual page.
Basically, for each management group there are up to two ways
of calling the module's functions.
In the case of the <emphasis>authentication</emphasis> and
<emphasis>session</emphasis> components there are actually
two separate functions. For the case of authentication, these
functions are
<citerefentry>
<refentrytitle>pam_authenticate</refentrytitle><manvolnum>3</manvolnum>
</citerefentry> and
<citerefentry>
<refentrytitle>pam_setcred</refentrytitle><manvolnum>3</manvolnum>
</citerefentry>, here <option>run1</option> means run the
filter from the <function>pam_authenticate</function> function
and <option>run2</option> means run the filter from
<function>pam_setcred</function>. In the case of the
session modules, <emphasis>run1</emphasis> implies
that the filter is invoked at the
<citerefentry>
<refentrytitle>pam_open_session</refentrytitle><manvolnum>3</manvolnum>
</citerefentry> stage, and <emphasis>run2</emphasis> for
<citerefentry>
<refentrytitle>pam_close_session</refentrytitle><manvolnum>3</manvolnum>
</citerefentry>.
</para>
<para>
For the case of the account component. Either
<emphasis>run1</emphasis> or <emphasis>run2</emphasis>
may be used.
</para>
<para>
For the case of the password component, <emphasis>run1</emphasis>
is used to indicate that the filter is run on the first
occasion of
<citerefentry>
<refentrytitle>pam_chauthtok</refentrytitle><manvolnum>3</manvolnum>
</citerefentry> (the <emphasis>PAM_PRELIM_CHECK</emphasis>
phase) and <emphasis>run2</emphasis> is used to indicate
that the filter is run on the second occasion (the
<emphasis>PAM_UPDATE_AUTHTOK</emphasis> phase).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
filter
</term>
<listitem>
<para>
The full pathname of the filter to be run and any command line
arguments that the filter might expect.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 xml:id="pam_filter-types">
<title>MODULE TYPES PROVIDED</title>
<para>
All module types (<option>auth</option>, <option>account</option>,
<option>password</option> and <option>session</option>) are provided.
</para>
</refsect1>
<refsect1 xml:id="pam_filter-return_values">
<title>RETURN VALUES</title>
<para>
<variablelist>
<varlistentry>
<term>PAM_SUCCESS</term>
<listitem>
<para>
The new filter was set successfully.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>PAM_ABORT</term>
<listitem>
<para>
Critical error, immediate abort.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 xml:id="pam_filter-examples">
<title>EXAMPLES</title>
<para>
Add the following line to <filename>/etc/pam.d/login</filename> to
see how to configure login to transpose upper and lower case letters
once the user has logged in:
<programlisting>
session required pam_filter.so run1 /lib/security/pam_filter/upperLOWER
</programlisting>
</para>
</refsect1>
<refsect1 xml:id="pam_filter-see_also">
<title>SEE ALSO</title>
<para>
<citerefentry>
<refentrytitle>pam.conf</refentrytitle><manvolnum>5</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>pam.d</refentrytitle><manvolnum>5</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>pam</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>
</para>
</refsect1>
<refsect1 xml:id="pam_filter-author">
<title>AUTHOR</title>
<para>
pam_filter was written by Andrew G. Morgan <morgan@kernel.org>.
</para>
</refsect1>
</refentry>