/mandos/trunk

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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"

	"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [

<!ENTITY COMMANDNAME "plymouth">

<!ENTITY TIMESTAMP "2018-02-08">

<!ENTITY % common SYSTEM "../common.ent">

%common;

]>

<refentry xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>

    <title>Mandos Manual</title>

    <!-- NWalsh’s docbook scripts use this to generate the footer: -->

    <productname>Mandos</productname>

    <productnumber>&version;</productnumber>

    <date>&TIMESTAMP;</date>

    <authorgroup>

      <author>

	<firstname>Björn</firstname>

	<surname>Påhlsson</surname>

	<address>

	  <email>belorn@recompile.se</email>

	</address>

      </author>

      <author>

	<firstname>Teddy</firstname>

	<surname>Hogeborn</surname>

	<address>

	  <email>teddy@recompile.se</email>

	</address>

      </author>

    </authorgroup>

    <copyright>

      <year>2010</year>

      <year>2011</year>

      <year>2012</year>

      <year>2013</year>

      <year>2014</year>

      <year>2015</year>

      <year>2016</year>

      <year>2017</year>

      <year>2018</year>

      <holder>Teddy Hogeborn</holder>

      <holder>Björn Påhlsson</holder>

    </copyright>

    <xi:include href="../legalnotice.xml"/>

  </refentryinfo>

  <refmeta>

    <refentrytitle>&COMMANDNAME;</refentrytitle>

    <manvolnum>8mandos</manvolnum>

  </refmeta>

  <refnamediv>

    <refname><command>&COMMANDNAME;</command></refname>

    <refpurpose>Mandos plugin to use plymouth to get a

    password.</refpurpose>

  </refnamediv>

  <refsynopsisdiv>

    <cmdsynopsis>

      <command>&COMMANDNAME;</command>

    </cmdsynopsis>

  </refsynopsisdiv>

  <refsect1 id="description">

    <title>DESCRIPTION</title>

    <para>

      This program prompts for a password using <citerefentry>

      <refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum>

      </citerefentry> and outputs any given password to standard

      output.  If no <citerefentry><refentrytitle

      >plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>

      process can be found, this program will immediately exit with an

      exit code indicating failure.

    </para>

    <para>

      This program is not very useful on its own.  This program is

      really meant to run as a plugin in the <application

      >Mandos</application> client-side system, where it is used as a

      fallback and alternative to retrieving passwords from a

      <application >Mandos</application> server.

    </para>

    <para>

      If this program is killed (presumably by

      <citerefentry><refentrytitle>plugin-runner</refentrytitle>

      <manvolnum>8mandos</manvolnum></citerefentry> because some other

      plugin provided the password), it cannot tell <citerefentry>

      <refentrytitle>plymouth</refentrytitle><manvolnum>8</manvolnum>

      </citerefentry> to abort requesting a password, because

      <citerefentry><refentrytitle>plymouth</refentrytitle>

      <manvolnum>8</manvolnum></citerefentry> does not support this.

      Therefore, this program will then <emphasis>kill</emphasis> the

      running <citerefentry><refentrytitle>plymouth</refentrytitle>

      <manvolnum>8</manvolnum></citerefentry> process and start a

      <emphasis>new</emphasis> one using the same command line

      arguments as the old one was using.

    </para>

  </refsect1>

  <refsect1 id="options">

    <title>OPTIONS</title>

    <para>

      This program takes no options.

    </para>

  </refsect1>

  <refsect1 id="exit_status">

    <title>EXIT STATUS</title>

    <para>

      If exit status is 0, the output from the program is the password

      as it was read.  Otherwise, if exit status is other than 0, the

      program was interrupted or encountered an error, and any output

      so far could be corrupt and/or truncated, and should therefore

      be ignored.

    </para>

  </refsect1>

  <refsect1 id="environment">

    <title>ENVIRONMENT</title>

    <variablelist>

      <varlistentry>

	<term><envar>cryptsource</envar></term>

	<term><envar>crypttarget</envar></term>

	<listitem>

	  <para>

	    If set, these environment variables will be assumed to

	    contain the source device name and the target device

	    mapper name, respectively, and will be shown as part of

	    the prompt.

	</para>

	<para>

	  These variables will normally be inherited from

	  <citerefentry><refentrytitle>plugin-runner</refentrytitle>

	  <manvolnum>8mandos</manvolnum></citerefentry>, which will

	  normally have inherited them from

	  <filename>/scripts/local-top/cryptroot</filename> in the

	  initial <acronym>RAM</acronym> disk environment, which will

	  have set them from parsing kernel arguments and

	  <filename>/conf/conf.d/cryptroot</filename> (also in the

	  initial RAM disk environment), which in turn will have been

	  created when the initial RAM disk image was created by

	  <filename

	  >/usr/share/initramfs-tools/hooks/cryptroot</filename>, by

	  extracting the information of the root file system from

	  <filename >/etc/crypttab</filename>.

	</para>

	<para>

	  This behavior is meant to exactly mirror the behavior of

	  <command>askpass</command>, the default password prompter.

	</para>

	</listitem>

      </varlistentry>

    </variablelist>

  </refsect1>

  <refsect1 id="files">

    <title>FILES</title>

    <variablelist>

      <varlistentry>

	<term><filename>/bin/plymouth</filename></term>

	<listitem>

	  <para>

	    This is the command run to retrieve a password from

	    <citerefentry><refentrytitle>plymouth</refentrytitle>

	    <manvolnum>8</manvolnum></citerefentry>.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><filename class="directory">/proc</filename></term>

	<listitem>

	  <para>

	    To find the running <citerefentry><refentrytitle

	    >plymouth</refentrytitle><manvolnum>8</manvolnum>

	    </citerefentry>, this directory will be searched for

	    numeric entries which will be assumed to be directories.

	    In all those directories, the <filename>exe</filename> and

	    <filename>cmdline</filename> entries will be used to

	    determine the name of the running binary, effective user

	    and group <abbrev>ID</abbrev>, and the command line

	    arguments.  See <citerefentry><refentrytitle

	    >proc</refentrytitle><manvolnum>5</manvolnum>

	    </citerefentry>.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><filename>/sbin/plymouthd</filename></term>

	<listitem>

	  <para>

	    This is the name of the binary which will be searched for

	    in the process list.  See <citerefentry><refentrytitle

	    >plymouth</refentrytitle><manvolnum>8</manvolnum>

	    </citerefentry>.

	  </para>

	</listitem>

      </varlistentry>

    </variablelist>

  </refsect1>

  <refsect1 id="bugs">

    <title>BUGS</title>

    <para>

      Killing the <citerefentry><refentrytitle

      >plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>

      daemon and starting a new one is ugly, but necessary as long as

      it does not support aborting a password request.

    </para>

    <xi:include href="../bugs.xml"/>

  </refsect1>

  <refsect1 id="example">

    <title>EXAMPLE</title>

    <para>

      Note that normally, this program will not be invoked directly,

      but instead started by the Mandos <citerefentry><refentrytitle

      >plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>

      </citerefentry>.

    </para>

    <informalexample>

      <para>

	This program takes no options.

      </para>

      <para>

	<userinput>&COMMANDNAME;</userinput>

      </para>

    </informalexample>

  </refsect1>

  <refsect1 id="security">

    <title>SECURITY</title>

    <para>

      If this program is killed by a signal, it will kill the process

      <abbrev>ID</abbrev> which at the start of this program was

      determined to run <citerefentry><refentrytitle

      >plymouth</refentrytitle><manvolnum>8</manvolnum></citerefentry>

      as root (see also <xref linkend="files"/>).  There is a very

      slight risk that, in the time between those events, that process

      <abbrev>ID</abbrev> was freed and then taken up by another

      process; the wrong process would then be killed.  Now, this

      program can only be killed by the user who started it; see

      <citerefentry><refentrytitle>plugin-runner</refentrytitle>

      <manvolnum>8mandos</manvolnum></citerefentry>.  This program

      should therefore be started by a completely separate

      non-privileged user, and no other programs should be allowed to

      run as that special user.  This means that it is not recommended

      to use the user "nobody" to start this program, as other

      possibly less trusted programs could be running as "nobody", and

      they would then be able to kill this program, triggering the

      killing of the process <abbrev>ID</abbrev> which may or may not

      be <citerefentry><refentrytitle>plymouth</refentrytitle>

      <manvolnum>8</manvolnum></citerefentry>.

    </para>

    <para>

      The only other thing that could be considered worthy of note is

      this:  This program is meant to be run by <citerefentry>

      <refentrytitle>plugin-runner</refentrytitle><manvolnum

      >8mandos</manvolnum></citerefentry>, and will, when run

      standalone, outside, in a normal environment, immediately output

      on its standard output any presumably secret password it just

      received.  Therefore, when running this program standalone

      (which should never normally be done), take care not to type in

      any real secret password by force of habit, since it would then

      immediately be shown as output.

    </para>

  </refsect1>

  <refsect1 id="see_also">

    <title>SEE ALSO</title>

    <para>

      <citerefentry><refentrytitle>intro</refentrytitle>

      <manvolnum>8mandos</manvolnum></citerefentry>,

      <citerefentry><refentrytitle>crypttab</refentrytitle>

      <manvolnum>5</manvolnum></citerefentry>,

      <citerefentry><refentrytitle>plugin-runner</refentrytitle>

      <manvolnum>8mandos</manvolnum></citerefentry>,

      <citerefentry><refentrytitle>proc</refentrytitle>

      <manvolnum>5</manvolnum></citerefentry>,

      <citerefentry><refentrytitle>plymouth</refentrytitle>

      <manvolnum>8</manvolnum></citerefentry>

    </para>

  </refsect1>

</refentry>

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