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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY VERSION "1.0">
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<!ENTITY COMMANDNAME "plugin-runner">
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<!ENTITY TIMESTAMP "2008-08-31">
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<!ENTITY TIMESTAMP "2016-02-28">
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<!ENTITY % common SYSTEM "common.ent">
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<refentry xmlns:xi="http://www.w3.org/2001/XInclude">
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<title>Mandos Manual</title>
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<!-- Nwalsh’s docbook scripts use this to generate the footer: -->
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<productname>Mandos</productname>
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<productnumber>&VERSION;</productnumber>
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<productnumber>&version;</productnumber>
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<date>&TIMESTAMP;</date>
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<firstname>Björn</firstname>
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<surname>Påhlsson</surname>
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<email>belorn@fukt.bsnet.se</email>
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<email>belorn@recompile.se</email>
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<firstname>Teddy</firstname>
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<surname>Hogeborn</surname>
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<email>teddy@fukt.bsnet.se</email>
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<email>teddy@recompile.se</email>
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<holder>Teddy Hogeborn</holder>
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<holder>Björn Påhlsson</holder>
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This manual page is free software: you can redistribute it
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and/or modify it under the terms of the GNU General Public
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License as published by the Free Software Foundation,
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either version 3 of the License, or (at your option) any
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This manual page is distributed in the hope that it will
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be useful, but WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A
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PARTICULAR PURPOSE. See the GNU General Public License
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You should have received a copy of the GNU General Public
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License along with this program; If not, see
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<ulink url="http://www.gnu.org/licenses/"/>.
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<xi:include href="legalnotice.xml"/>
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<refentrytitle>&COMMANDNAME;</refentrytitle>
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<manvolnum>8mandos</manvolnum>
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</refsynopsisdiv>
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<refsect1 id="description">
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<title>DESCRIPTION</title>
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<command>&COMMANDNAME;</command> is a plugin runner that waits
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for any of its plugins to return sucessfull with a password, and
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passes it to cryptsetup as stdout message. This command is not
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meant to be invoked directly, but is instead meant to be run by
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cryptsetup by being specified in /etc/crypttab as a keyscript
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and subsequlently started in the initrd environment. See
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<command>&COMMANDNAME;</command> is a program which is meant to
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be specified as a <quote>keyscript</quote> for the root disk in
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<citerefentry><refentrytitle>crypttab</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry> for more information on
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plugins is looked for in the plugins directory which by default will be
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/conf/conf.d/mandos/plugins.d if not changed by option --plugin-dir.
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<manvolnum>5</manvolnum></citerefentry>. The aim of this
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program is therefore to output a password, which then
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<citerefentry><refentrytitle>cryptsetup</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry> will use to unlock the
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This program is not meant to be invoked directly, but can be in
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order to test it. Note that any password obtained will simply
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be output on standard output.
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<refsect1 id="purpose">
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<title>PURPOSE</title>
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The purpose of this is to enable <emphasis>remote and unattended
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rebooting</emphasis> of client host computer with an
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<emphasis>encrypted root file system</emphasis>. See <xref
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linkend="overview"/> for details.
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<title>OPTIONS</title>
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<term><option>--global-env
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<replaceable>ENV</replaceable><literal>=</literal><replaceable
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>value</replaceable></option></term>
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<replaceable>ENV</replaceable><literal>=</literal><replaceable
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>value</replaceable></option></term>
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This option will add an environment variable setting to
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all plugins. This will override any inherited environment
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<term><option>--env-for
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<replaceable>PLUGIN</replaceable><literal>:</literal
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><replaceable>ENV</replaceable><literal>=</literal
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><replaceable>value</replaceable></option></term>
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<replaceable>PLUGIN</replaceable><literal>:</literal
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><replaceable>ENV</replaceable><literal>=</literal
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><replaceable>value</replaceable></option></term>
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This option will add an environment variable setting to
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the <replaceable>PLUGIN</replaceable> plugin. This will
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override any inherited environment variables or
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environment variables specified using
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<option>--global-env</option>.
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<term><option>--global-options
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<replaceable>OPTIONS</replaceable></option></term>
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<replaceable>OPTIONS</replaceable></option></term>
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Global options given to all plugins as additional start
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arguments. Options are specified with a -o flag followed
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by a comma separated string of options.
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Pass some options to <emphasis>all</emphasis> plugins.
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<replaceable>OPTIONS</replaceable> is a comma separated
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list of options. This is not a very useful option, except
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for specifying the <quote><option>--debug</option></quote>
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option to all plugins.
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<term><option>--options-for
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<replaceable>PLUGIN</replaceable><literal>:</literal
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><replaceable>OPTION</replaceable></option></term>
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Plugin specific options given to the plugin as additional
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start arguments. Options are specified with a -o flag
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followed by a comma separated string of options.
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Pass some options to a specific plugin. <replaceable
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>PLUGIN</replaceable> is the name (file basename) of a
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plugin, and <replaceable>OPTIONS</replaceable> is a comma
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separated list of options.
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Note that since options are not split on whitespace, the
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way to pass, to the plugin
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<quote><filename>foo</filename></quote>, the option
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<option>--bar</option> with the option argument
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<quote>baz</quote> is either
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<userinput>--options-for=foo:--bar=baz</userinput> or
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<userinput>--options-for=foo:--bar,baz</userinput>. Using
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<userinput>--options-for="foo:--bar baz"</userinput>. will
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<emphasis>not</emphasis> work.
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<term><option> --disable
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<term><option>--disable
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<replaceable>PLUGIN</replaceable></option></term>
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<replaceable>PLUGIN</replaceable></option></term>
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Disable a specific plugin
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Disable the plugin named
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<replaceable>PLUGIN</replaceable>. The plugin will not be
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<term><option>--enable
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<replaceable>PLUGIN</replaceable></option></term>
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<replaceable>PLUGIN</replaceable></option></term>
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Re-enable the plugin named
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<replaceable>PLUGIN</replaceable>. This is only useful to
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undo a previous <option>--disable</option> option, maybe
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from the configuration file.
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<term><option>--groupid
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<replaceable>ID</replaceable></option></term>
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Group ID the plugins will run as
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Change to group ID <replaceable>ID</replaceable> on
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startup. The default is 65534. All plugins will be
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started using this group ID. <emphasis>Note:</emphasis>
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This must be a number, not a name.
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<term><option>--userid
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<replaceable>ID</replaceable></option></term>
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User ID the plugins will run as
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Change to user ID <replaceable>ID</replaceable> on
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startup. The default is 65534. All plugins will be
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started using this user ID. <emphasis>Note:</emphasis>
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This must be a number, not a name.
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<term><option>--plugin-dir
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<replaceable>DIRECTORY</replaceable></option></term>
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Specify a different plugin directory
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Specify a different plugin directory. The default is
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<filename>/lib/mandos/plugins.d</filename>, which will
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exist in the initial <acronym>RAM</acronym> disk
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<term><option>--plugin-helper-dir
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<replaceable>DIRECTORY</replaceable></option></term>
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Specify a different plugin helper directory. The default
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is <filename>/lib/mandos/plugin-helpers</filename>, which
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will exist in the initial <acronym>RAM</acronym> disk
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environment. (This will simply be passed to all plugins
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via the <envar>MANDOSPLUGINHELPERDIR</envar> environment
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variable. See <xref linkend="writing_plugins"/>)
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<term><option>--config-file
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<replaceable>FILE</replaceable></option></term>
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Specify a different file to read additional options from.
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See <xref linkend="files"/>. Other command line options
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will override options specified in the file.
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<term><option>--usage</option></term>
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Gives a short usage message
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Gives a short usage message.
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<term><option>--version</option></term>
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<term><option>-V</option></term>
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Prints the program version
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Prints the program version.
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<refsect1 id="overview">
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<title>OVERVIEW</title>
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<xi:include href="overview.xml"/>
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This program will run on the client side in the initial
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<acronym>RAM</acronym> disk environment, and is responsible for
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getting a password. It does this by running plugins, one of
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which will normally be the actual client program communicating
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<refsect1 id="plugins">
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<title>PLUGINS</title>
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This program will get a password by running a number of
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<firstterm>plugins</firstterm>, which are simply executable
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programs in a directory in the initial <acronym>RAM</acronym>
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disk environment. The default directory is
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<filename>/lib/mandos/plugins.d</filename>, but this can be
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changed with the <option>--plugin-dir</option> option. The
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plugins are started in parallel, and the first plugin to output
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a password <emphasis>and</emphasis> exit with a successful exit
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code will make this plugin-runner output the password from that
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plugin, stop any other plugins, and exit.
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<refsect2 id="writing_plugins">
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<title>WRITING PLUGINS</title>
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A plugin is simply a program which prints a password to its
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standard output and then exits with a successful (zero) exit
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status. If the exit status is not zero, any output on
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standard output will be ignored by the plugin runner. Any
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output on its standard error channel will simply be passed to
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the standard error of the plugin runner, usually the system
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If the password is a single-line, manually entered passprase,
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a final trailing newline character should
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<emphasis>not</emphasis> be printed.
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The plugin will run in the initial RAM disk environment, so
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care must be taken not to depend on any files or running
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services not available there. Any helper executables required
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by the plugin (which are not in the <envar>PATH</envar>) can
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be placed in the plugin helper directory, the name of which
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will be made available to the plugin via the
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<envar>MANDOSPLUGINHELPERDIR</envar> environment variable.
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The plugin must exit cleanly and free all allocated resources
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upon getting the TERM signal, since this is what the plugin
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runner uses to stop all other plugins when one plugin has
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output a password and exited cleanly.
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The plugin must not use resources, like for instance reading
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from the standard input, without knowing that no other plugin
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It is useful, but not required, for the plugin to take the
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<option>--debug</option> option.
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<refsect1 id="fallback">
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<title>FALLBACK</title>
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If no plugins succeed, this program will, as a fallback, ask for
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a password on the console using <citerefentry><refentrytitle
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>getpass</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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and output it. This is not meant to be the normal mode of
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operation, as there is a separate plugin for getting a password
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<refsect1 id="exit_status">
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<title>EXIT STATUS</title>
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Exit status of this program is zero if no errors were
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encountered, and otherwise not. The fallback (see <xref
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linkend="fallback"/>) may or may not have succeeded in either
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<refsect1 id="environment">
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<title>ENVIRONMENT</title>
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This program does not use any environment variables itself, it
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only passes on its environment to all the plugins. The
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environment passed to plugins can be modified using the
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<option>--global-env</option> and <option>--env-for</option>
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options. Also, the <option>--plugin-helper-dir</option> option
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will affect the environment variable
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<envar>MANDOSPLUGINHELPERDIR</envar> for the plugins.
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<refsect1 id="files">
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<title>FILES</title>
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<refsect1 id="notes">
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>/conf/conf.d/mandos/plugin-runner.conf</filename></term>
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Since this program will be run as a keyscript, there is
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little to no opportunity to pass command line arguments
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to it. Therefore, it will <emphasis>also</emphasis>
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read this file and use its contents as
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whitespace-separated command line options. Also,
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everything from a <quote>#</quote> character to the end
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of a line is ignored.
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This program is meant to run in the initial RAM disk
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environment, so that is where this file is assumed to
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exist. The file does not need to exist in the normal
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This file will be processed <emphasis>before</emphasis>
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the normal command line options, so the latter can
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override the former, if need be.
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This file name is the default; the file to read for
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arguments can be changed using the
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<option>--config-file</option> option.
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<refsect1 id="bugs">
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<title>BUGS</title>
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The <option>--config-file</option> option is ignored when
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specified from within a configuration file.
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<refsect1 id="examples">
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<title>EXAMPLE</title>
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Normal invocation needs no options:
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<userinput>&COMMANDNAME;</userinput>
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Run the program, but not the plugins, in debug mode:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug</userinput>
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Run all plugins, but run the <quote>foo</quote> plugin in
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --options-for=foo:--debug</userinput>
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Run all plugins, but not the program, in debug mode:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --global-options=--debug</userinput>
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Read a different configuration file, run plugins from a
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different directory, specify an alternate plugin helper
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directory and add two options to the
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<citerefentry><refentrytitle >mandos-client</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry> plugin:
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<!-- do not wrap this line -->
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<userinput>cd /etc/keys/mandos; &COMMANDNAME; --config-file=/etc/mandos/plugin-runner.conf --plugin-dir /usr/lib/x86_64-linux-gnu/mandos/plugins.d --plugin-helper-dir /usr/lib/x86_64-linux-gnu/mandos/plugin-helpers --options-for=mandos-client:--pubkey=pubkey.txt,--seckey=seckey.txt</userinput>
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<refsect1 id="security">
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<title>SECURITY</title>
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This program will, when starting, try to switch to another user.
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If it is started as root, it will succeed, and will by default
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switch to user and group 65534, which are assumed to be
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non-privileged. This user and group is then what all plugins
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will be started as. Therefore, the only way to run a plugin as
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a privileged user is to have the set-user-ID or set-group-ID bit
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set on the plugin executable file (see <citerefentry>
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<refentrytitle>execve</refentrytitle><manvolnum>2</manvolnum>
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If this program is used as a keyscript in <citerefentry
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><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry>, there is a slight risk that if this program
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fails to work, there might be no way to boot the system except
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for booting from another media and editing the initial RAM disk
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image to not run this program. This is, however, unlikely,
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since the <citerefentry><refentrytitle
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>password-prompt</refentrytitle><manvolnum>8mandos</manvolnum>
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</citerefentry> plugin will read a password from the console in
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case of failure of the other plugins, and this plugin runner
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will also, in case of catastrophic failure, itself fall back to
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asking and outputting a password on the console (see <xref
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linkend="fallback"/>).
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<refsect1 id="see_also">
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<title>SEE ALSO</title>
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<citerefentry><refentrytitle>intro</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>cryptsetup</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>crypttab</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>execve</refentrytitle>
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<manvolnum>2</manvolnum></citerefentry>,
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660
<citerefentry><refentrytitle>mandos</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>password-prompt</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>password-request</refentrytitle>
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<citerefentry><refentrytitle>mandos-client</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>
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