plugin-runner.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
	"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY COMMANDNAME "plugin-runner">
<!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>2008</year>
      <year>2009</year>
      <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>
      Run Mandos plugins, pass data from first to succeed.
    </refpurpose>
  </refnamediv>
  
  <refsynopsisdiv>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <group rep="repeat">
	<arg choice="plain"><option>--global-env=<replaceable
	>ENV</replaceable><literal>=</literal><replaceable
	>value</replaceable></option></arg>
	<arg choice="plain"><option>-G
	<replaceable>ENV</replaceable><literal>=</literal><replaceable
	>value</replaceable> </option></arg>
      </group>
      <sbr/>
      <group rep="repeat">
	<arg choice="plain"><option>--env-for=<replaceable
	>PLUGIN</replaceable><literal>:</literal><replaceable
	>ENV</replaceable><literal>=</literal><replaceable
	>value</replaceable></option></arg>
	<arg choice="plain"><option>-E<replaceable>
	PLUGIN</replaceable><literal>:</literal><replaceable
	>ENV</replaceable><literal>=</literal><replaceable
	>value</replaceable> </option></arg>
      </group>
      <sbr/>
      <group rep="repeat">
	<arg choice="plain"><option>--global-options=<replaceable
	>OPTIONS</replaceable></option></arg>
	<arg choice="plain"><option>-g<replaceable>
	OPTIONS</replaceable> </option></arg>
      </group>
      <sbr/>
      <group rep="repeat">
	<arg choice="plain"><option>--options-for=<replaceable
	>PLUGIN</replaceable><literal>:</literal><replaceable
	>OPTIONS</replaceable></option></arg>
	<arg choice="plain"><option>-o<replaceable>
	PLUGIN</replaceable><literal>:</literal><replaceable
	>OPTIONS</replaceable> </option></arg>
      </group>
      <sbr/>
      <group rep="repeat">
	<arg choice="plain"><option>--disable=<replaceable
	>PLUGIN</replaceable></option></arg>
	<arg choice="plain"><option>-d
	<replaceable>PLUGIN</replaceable> </option></arg>
      </group>
      <sbr/>
      <group rep="repeat">
	<arg choice="plain"><option>--enable=<replaceable
	>PLUGIN</replaceable></option></arg>
	<arg choice="plain"><option>-e
	<replaceable>PLUGIN</replaceable> </option></arg>
      </group>
      <sbr/>
      <arg><option>--groupid=<replaceable
      >ID</replaceable></option></arg>
      <sbr/>
      <arg><option>--userid=<replaceable
      >ID</replaceable></option></arg>
      <sbr/>
      <arg><option>--plugin-dir=<replaceable
      >DIRECTORY</replaceable></option></arg>
      <sbr/>
      <arg><option>--plugin-helper-dir=<replaceable
      >DIRECTORY</replaceable></option></arg>
      <sbr/>
      <arg><option>--config-file=<replaceable
      >FILE</replaceable></option></arg>
      <sbr/>
      <arg><option>--debug</option></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <group choice="req">
	<arg choice="plain"><option>--help</option></arg>
	<arg choice="plain"><option>-?</option></arg>
      </group>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <arg choice="plain"><option>--usage</option></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <group choice="req">
	<arg choice="plain"><option>--version</option></arg>
	<arg choice="plain"><option>-V</option></arg>
      </group>
    </cmdsynopsis>
  </refsynopsisdiv>
  
  <refsect1 id="description">
    <title>DESCRIPTION</title>
    <para>
      <command>&COMMANDNAME;</command> is a program which is meant to
      be specified as a <quote>keyscript</quote> for the root disk in
      <citerefentry><refentrytitle>crypttab</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry>.  The aim of this
      program is therefore to output a password, which then
      <citerefentry><refentrytitle>cryptsetup</refentrytitle>
      <manvolnum>8</manvolnum></citerefentry> will use to unlock the
      root disk.
    </para>
    <para>
      This program is not meant to be invoked directly, but can be in
      order to test it.  Note that any password obtained will simply
      be output on standard output.
    </para>
  </refsect1>
  
  <refsect1 id="purpose">
    <title>PURPOSE</title>
    <para>
      The purpose of this is to enable <emphasis>remote and unattended
      rebooting</emphasis> of client host computer with an
      <emphasis>encrypted root file system</emphasis>.  See <xref
      linkend="overview"/> for details.
    </para>
  </refsect1>
  
  <refsect1>
    <title>OPTIONS</title>
    <variablelist>
      <varlistentry>
	<term><option>--global-env
	<replaceable>ENV</replaceable><literal>=</literal><replaceable
	>value</replaceable></option></term>
	<term><option>-G
	<replaceable>ENV</replaceable><literal>=</literal><replaceable
	>value</replaceable></option></term>
	<listitem>
	  <para>
	    This option will add an environment variable setting to
	    all plugins.  This will override any inherited environment
	    variable.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--env-for
	<replaceable>PLUGIN</replaceable><literal>:</literal
	><replaceable>ENV</replaceable><literal>=</literal
	><replaceable>value</replaceable></option></term>
	<term><option>-E
	<replaceable>PLUGIN</replaceable><literal>:</literal
	><replaceable>ENV</replaceable><literal>=</literal
	><replaceable>value</replaceable></option></term>
	<listitem>
	  <para>
	    This option will add an environment variable setting to
	    the <replaceable>PLUGIN</replaceable> plugin.  This will
	    override any inherited environment variables or
	    environment variables specified using
	    <option>--global-env</option>.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--global-options
	<replaceable>OPTIONS</replaceable></option></term>
	<term><option>-g
	<replaceable>OPTIONS</replaceable></option></term>
	<listitem>
	  <para>
	    Pass some options to <emphasis>all</emphasis> plugins.
	    <replaceable>OPTIONS</replaceable> is a comma separated
	    list of options.  This is not a very useful option, except
	    for specifying the <quote><option>--debug</option></quote>
	    option to all plugins.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--options-for
	<replaceable>PLUGIN</replaceable><literal>:</literal
	><replaceable>OPTION</replaceable></option></term>
	<term><option>-o
	<replaceable>PLUGIN</replaceable><literal>:</literal
	><replaceable>OPTION</replaceable></option></term>
	<listitem>
	  <para>
	    Pass some options to a specific plugin.  <replaceable
	    >PLUGIN</replaceable> is the name (file basename) of a
	    plugin, and <replaceable>OPTIONS</replaceable> is a comma
	    separated list of options.
	  </para>
	  <para>
	    Note that since options are not split on whitespace, the
	    way to pass, to the plugin
	    <quote><filename>foo</filename></quote>, the option
	    <option>--bar</option> with the option argument
	    <quote>baz</quote> is either
	    <userinput>--options-for=foo:--bar=baz</userinput> or
	    <userinput>--options-for=foo:--bar,baz</userinput>.  Using
	    <userinput>--options-for="foo:--bar baz"</userinput>. will
	    <emphasis>not</emphasis> work.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--disable
	<replaceable>PLUGIN</replaceable></option></term>
	<term><option>-d
	<replaceable>PLUGIN</replaceable></option></term>
	<listitem>
	  <para>
	    Disable the plugin named
	    <replaceable>PLUGIN</replaceable>.  The plugin will not be
	    started.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--enable
	<replaceable>PLUGIN</replaceable></option></term>
	<term><option>-e
	<replaceable>PLUGIN</replaceable></option></term>
	<listitem>
	  <para>
	    Re-enable the plugin named
	    <replaceable>PLUGIN</replaceable>.  This is only useful to
	    undo a previous <option>--disable</option> option, maybe
	    from the configuration file.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--groupid
	<replaceable>ID</replaceable></option></term>
	<listitem>
	  <para>
	    Change to group ID <replaceable>ID</replaceable> on
	    startup.  The default is 65534.  All plugins will be
	    started using this group ID.  <emphasis>Note:</emphasis>
	    This must be a number, not a name.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--userid
	<replaceable>ID</replaceable></option></term>
	<listitem>
	  <para>
	    Change to user ID <replaceable>ID</replaceable> on
	    startup.  The default is 65534.  All plugins will be
	    started using this user ID.  <emphasis>Note:</emphasis>
	    This must be a number, not a name.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--plugin-dir
	<replaceable>DIRECTORY</replaceable></option></term>
	<listitem>
	  <para>
	    Specify a different plugin directory.  The default is
	    <filename>/lib/mandos/plugins.d</filename>, which will
	    exist in the initial <acronym>RAM</acronym> disk
	    environment.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--plugin-helper-dir
	<replaceable>DIRECTORY</replaceable></option></term>
	<listitem>
	  <para>
	    Specify a different plugin helper directory.  The default
	    is <filename>/lib/mandos/plugin-helpers</filename>, which
	    will exist in the initial <acronym>RAM</acronym> disk
	    environment.  (This will simply be passed to all plugins
	    via the <envar>MANDOSPLUGINHELPERDIR</envar> environment
	    variable.  See <xref linkend="writing_plugins"/>)
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--config-file
	<replaceable>FILE</replaceable></option></term>
	<listitem>
	  <para>
	    Specify a different file to read additional options from.
	    See <xref linkend="files"/>.  Other command line options
	    will override options specified in the file.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--debug</option></term>
	<listitem>
	  <para>
	    Enable debug mode.  This will enable a lot of output to
	    standard error about what the program is doing.  The
	    program will still perform all other functions normally.
	    The default is to <emphasis>not</emphasis> run in debug
	    mode.
	  </para>
	  <para>
	    The plugins will <emphasis>not</emphasis> be affected by
	    this option.  Use
	    <userinput><option>--global-options=--debug</option></userinput>
	    if complete debugging eruption is desired.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--help</option></term>
	<term><option>-?</option></term>
	<listitem>
	  <para>
	    Gives a help message about options and their meanings.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--usage</option></term>
	<listitem>
	  <para>
	    Gives a short usage message.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--version</option></term>
	<term><option>-V</option></term>
	<listitem>
	  <para>
	    Prints the program version.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
  
  <refsect1 id="overview">
    <title>OVERVIEW</title>
    <xi:include href="overview.xml"/>
    <para>
      This program will run on the client side in the initial
      <acronym>RAM</acronym> disk environment, and is responsible for
      getting a password.  It does this by running plugins, one of
      which will normally be the actual client program communicating
      with the server.
    </para>
  </refsect1>
  <refsect1 id="plugins">
    <title>PLUGINS</title>
    <para>
      This program will get a password by running a number of
      <firstterm>plugins</firstterm>, which are simply executable
      programs in a directory in the initial <acronym>RAM</acronym>
      disk environment.  The default directory is
      <filename>/lib/mandos/plugins.d</filename>, but this can be
      changed with the <option>--plugin-dir</option> option.  The
      plugins are started in parallel, and the first plugin to output
      a password <emphasis>and</emphasis> exit with a successful exit
      code will make this plugin-runner output the password from that
      plugin, stop any other plugins, and exit.
    </para>
    
    <refsect2 id="writing_plugins">
      <title>WRITING PLUGINS</title>
      <para>
	A plugin is simply a program which prints a password to its
	standard output and then exits with a successful (zero) exit
	status.  If the exit status is not zero, any output on
	standard output will be ignored by the plugin runner.  Any
	output on its standard error channel will simply be passed to
	the standard error of the plugin runner, usually the system
	console.
      </para>
      <para>
	If the password is a single-line, manually entered passprase,
	a final trailing newline character should
	<emphasis>not</emphasis> be printed.
      </para>
      <para>
	The plugin will run in the initial RAM disk environment, so
	care must be taken not to depend on any files or running
	services not available there.  Any helper executables required
	by the plugin (which are not in the <envar>PATH</envar>) can
	be placed in the plugin helper directory, the name of which
	will be made available to the plugin via the
	<envar>MANDOSPLUGINHELPERDIR</envar> environment variable.
      </para>
      <para>
	The plugin must exit cleanly and free all allocated resources
	upon getting the TERM signal, since this is what the plugin
	runner uses to stop all other plugins when one plugin has
	output a password and exited cleanly.
      </para>
      <para>
	The plugin must not use resources, like for instance reading
	from the standard input, without knowing that no other plugin
	is also using it.
      </para>
      <para>
	It is useful, but not required, for the plugin to take the
	<option>--debug</option> option.
      </para>
    </refsect2>
  </refsect1>
  
  <refsect1 id="fallback">
    <title>FALLBACK</title>
    <para>
      If no plugins succeed, this program will, as a fallback, ask for
      a password on the console using <citerefentry><refentrytitle
      >getpass</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
      and output it.  This is not meant to be the normal mode of
      operation, as there is a separate plugin for getting a password
      from the console.
    </para>
  </refsect1>
  
  <refsect1 id="exit_status">
    <title>EXIT STATUS</title>
    <para>
      Exit status of this program is zero if no errors were
      encountered, and otherwise not.  The fallback (see <xref
      linkend="fallback"/>) may or may not have succeeded in either
      case.
    </para>
  </refsect1>
  
  <refsect1 id="environment">
    <title>ENVIRONMENT</title>
    <para>
      This program does not use any environment variables itself, it
      only passes on its environment to all the plugins.  The
      environment passed to plugins can be modified using the
      <option>--global-env</option> and <option>--env-for</option>
      options.  Also, the <option>--plugin-helper-dir</option> option
      will affect the environment variable
      <envar>MANDOSPLUGINHELPERDIR</envar> for the plugins.
    </para>
  </refsect1>
  
  <refsect1 id="files">
    <title>FILES</title>
    <para>
      <variablelist>
	<varlistentry>
	  <term><filename
	  >/conf/conf.d/mandos/plugin-runner.conf</filename></term>
	  <listitem>
	    <para>
	      Since this program will be run as a keyscript, there is
	      little to no opportunity to pass command line arguments
	      to it.  Therefore, it will <emphasis>also</emphasis>
	      read this file and use its contents as
	      whitespace-separated command line options.  Also,
	      everything from a <quote>#</quote> character to the end
	      of a line is ignored.
	    </para>
	    <para>
	      This program is meant to run in the initial RAM disk
	      environment, so that is where this file is assumed to
	      exist.  The file does not need to exist in the normal
	      file system.
	    </para>
	    <para>
	      This file will be processed <emphasis>before</emphasis>
	      the normal command line options, so the latter can
	      override the former, if need be.
	    </para>
	    <para>
	      This file name is the default; the file to read for
	      arguments can be changed using the
	      <option>--config-file</option> option.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><filename class="directory"
	  >/lib/mandos/plugins.d</filename></term>
	  <listitem>
	    <para>
	      The default plugin directory; can be changed by the
	      <option>--plugin-dir</option> option.
	    </para>
	  </listitem>
	</varlistentry>
	<varlistentry>
	  <term><filename class="directory"
	  >/lib/mandos/plugin-helpers</filename></term>
	  <listitem>
	    <para>
	      The default plugin helper directory; can be changed by
	      the <option>--plugin-helper-dir</option> option.
	    </para>
	  </listitem>
	</varlistentry>
      </variablelist>
    </para>
  </refsect1>
  
  <refsect1 id="bugs">
    <title>BUGS</title>
    <para>
      The <option>--config-file</option> option is ignored when
      specified from within a configuration file.
    </para>
    <xi:include href="bugs.xml"/>
  </refsect1>
  
  <refsect1 id="examples">
    <title>EXAMPLE</title>
    <informalexample>
      <para>
	Normal invocation needs no options:
      </para>
      <para>
	<userinput>&COMMANDNAME;</userinput>
      </para>
    </informalexample>
    <informalexample>
      <para>
	Run the program, but not the plugins, in debug mode:
      </para>
      <para>
	
	<!-- do not wrap this line -->
	<userinput>&COMMANDNAME; --debug</userinput>
	
      </para>
    </informalexample>
    <informalexample>
      <para>
	Run all plugins, but run the <quote>foo</quote> plugin in
	debug mode:
      </para>
      <para>
	
	<!-- do not wrap this line -->
	<userinput>&COMMANDNAME; --options-for=foo:--debug</userinput>
	
      </para>
    </informalexample>
    <informalexample>
      <para>
	Run all plugins, but not the program, in debug mode:
      </para>
      <para>
	
	<!-- do not wrap this line -->
	<userinput>&COMMANDNAME; --global-options=--debug</userinput>
	
      </para>
    </informalexample>
    <informalexample>
      <para>
	Read a different configuration file, run plugins from a
	different directory, specify an alternate plugin helper
	directory and add two options to the
	<citerefentry><refentrytitle >mandos-client</refentrytitle>
	<manvolnum>8mandos</manvolnum></citerefentry> plugin:
      </para>
      <para>

<!-- do not wrap this line -->
<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>

      </para>
    </informalexample>
  </refsect1>
  <refsect1 id="security">
    <title>SECURITY</title>
    <para>
      This program will, when starting, try to switch to another user.
      If it is started as root, it will succeed, and will by default
      switch to user and group 65534, which are assumed to be
      non-privileged.  This user and group is then what all plugins
      will be started as.  Therefore, the only way to run a plugin as
      a privileged user is to have the set-user-ID or set-group-ID bit
      set on the plugin executable file (see <citerefentry>
      <refentrytitle>execve</refentrytitle><manvolnum>2</manvolnum>
      </citerefentry>).
    </para>
    <para>
      If this program is used as a keyscript in <citerefentry
      ><refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
      </citerefentry>, there is a slight risk that if this program
      fails to work, there might be no way to boot the system except
      for booting from another media and editing the initial RAM disk
      image to not run this program.  This is, however, unlikely,
      since the <citerefentry><refentrytitle
      >password-prompt</refentrytitle><manvolnum>8mandos</manvolnum>
      </citerefentry> plugin will read a password from the console in
      case of failure of the other plugins, and this plugin runner
      will also, in case of catastrophic failure, itself fall back to
      asking and outputting a password on the console (see <xref
      linkend="fallback"/>).
    </para>
  </refsect1>
  
  <refsect1 id="see_also">
    <title>SEE ALSO</title>
    <para>
      <citerefentry><refentrytitle>intro</refentrytitle>
      <manvolnum>8mandos</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>cryptsetup</refentrytitle>
      <manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>crypttab</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>execve</refentrytitle>
      <manvolnum>2</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>mandos</refentrytitle>
      <manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>password-prompt</refentrytitle>
      <manvolnum>8mandos</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>mandos-client</refentrytitle>
      <manvolnum>8mandos</manvolnum></citerefentry>
    </para>
  </refsect1>
  
</refentry>
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