/mandos/trunk

<?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 "mandos-client">

<!ENTITY TIMESTAMP "2011-11-27">

<!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>2011</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>

      Client for <application>Mandos</application>

    </refpurpose>

  </refnamediv>

  <refsynopsisdiv>

    <cmdsynopsis>

      <command>&COMMANDNAME;</command>

      <group>

	<arg choice="plain"><option>--connect

	<replaceable>ADDRESS</replaceable><literal>:</literal

	><replaceable>PORT</replaceable></option></arg>

	<arg choice="plain"><option>-c

	<replaceable>ADDRESS</replaceable><literal>:</literal

	><replaceable>PORT</replaceable></option></arg>

      </group>

      <sbr/>

      <group>

	<arg choice="plain"><option>--interface

	<replaceable>NAME</replaceable></option></arg>

	<arg choice="plain"><option>-i

	<replaceable>NAME</replaceable></option></arg>

      </group>

      <sbr/>

      <group>

	<arg choice="plain"><option>--pubkey

	<replaceable>FILE</replaceable></option></arg>

	<arg choice="plain"><option>-p

	<replaceable>FILE</replaceable></option></arg>

      </group>

      <sbr/>

      <group>

	<arg choice="plain"><option>--seckey

	<replaceable>FILE</replaceable></option></arg>

	<arg choice="plain"><option>-s

	<replaceable>FILE</replaceable></option></arg>

      </group>

      <sbr/>

      <arg>

	<option>--priority <replaceable>STRING</replaceable></option>

      </arg>

      <sbr/>

      <arg>

	<option>--dh-bits <replaceable>BITS</replaceable></option>

      </arg>

      <sbr/>

      <arg>

	<option>--delay <replaceable>SECONDS</replaceable></option>

      </arg>

      <sbr/>

      <arg>

	<option>--retry <replaceable>SECONDS</replaceable></option>

      </arg>

      <sbr/>

      <arg>

	<option>--network-hook-dir

	<replaceable>DIR</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 client program that

      communicates with <citerefentry><refentrytitle

      >mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>

      to get a password.  In slightly more detail, this client program

      brings up a network interface, uses the interface’s IPv6

      link-local address to get network connectivity, uses Zeroconf to

      find servers on the local network, and communicates with servers

      using TLS with an OpenPGP key to ensure authenticity and

      confidentiality.  This client program keeps running, trying all

      servers on the network, until it receives a satisfactory reply

      or a TERM signal.  After all servers have been tried, all

      servers are periodically retried.  If no servers are found it

      will wait indefinitely for new servers to appear.

    </para>

    <para>

      The network interface is selected like this: If an interface is

      specified using the <option>--interface</option> option, that

      interface is used.  Otherwise, <command>&COMMANDNAME;</command>

      will choose any interface that is up and running and is not a

      loopback interface, is not a point-to-point interface, is

      capable of broadcasting and does not have the NOARP flag (see

      <citerefentry><refentrytitle>netdevice</refentrytitle>

      <manvolnum>7</manvolnum></citerefentry>).  (If the

      <option>--connect</option> option is used, point-to-point

      interfaces and non-broadcast interfaces are accepted.)  If no

      acceptable interfaces are found, re-run the check but without

      the <quote>up and running</quote> requirement, and manually take

      the selected interface up (and later take it down on program

      exit).

    </para>

    <para>

      Before a network interface is selected, all <quote>network

      hooks</quote> are run; see <xref linkend="network-hooks"/>.

    </para>

    <para>

      This program is not meant to be run directly; it is really meant

      to run as a plugin of the <application>Mandos</application>

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

      <manvolnum>8mandos</manvolnum></citerefentry>, which runs in the

      initial <acronym>RAM</acronym> disk environment because it is

      specified as a <quote>keyscript</quote> in the <citerefentry>

      <refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>

      </citerefentry> file.

    </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 id="options">

    <title>OPTIONS</title>

    <para>

      This program is commonly not invoked from the command line; it

      is normally started by the <application>Mandos</application>

      plugin runner, see <citerefentry><refentrytitle

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

      </citerefentry>.  Any command line options this program accepts

      are therefore normally provided by the plugin runner, and not

      directly.

    </para>

    <variablelist>

      <varlistentry>

	<term><option>--connect=<replaceable

	>ADDRESS</replaceable><literal>:</literal><replaceable

	>PORT</replaceable></option></term>

	<term><option>-c

	<replaceable>ADDRESS</replaceable><literal>:</literal

	><replaceable>PORT</replaceable></option></term>

	<listitem>

	  <para>

	    Do not use Zeroconf to locate servers.  Connect directly

	    to only one specified <application>Mandos</application>

	    server.  Note that an IPv6 address has colon characters in

	    it, so the <emphasis>last</emphasis> colon character is

	    assumed to separate the address from the port number.

	  </para>

	  <para>

	    This option is normally only useful for testing and

	    debugging.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--interface=<replaceable

	>NAME</replaceable></option></term>

	<term><option>-i

	<replaceable>NAME</replaceable></option></term>

	<listitem>

	  <para>

	    Network interface that will be brought up and scanned for

	    Mandos servers to connect to.  The default is the empty

	    string, which will automatically choose an appropriate

	    interface.

	  </para>

	  <para>

	    If the <option>--connect</option> option is used, this

	    specifies the interface to use to connect to the address

	    given.

	  </para>

	  <para>

	    Note that since this program will normally run in the

	    initial RAM disk environment, the interface must be an

	    interface which exists at that stage.  Thus, the interface

	    can not be a pseudo-interface such as <quote>br0</quote>

	    or <quote>tun0</quote>; such interfaces will not exist

	    until much later in the boot process, and can not be used

	    by this program, unless created by a <quote>network

	    hook</quote> — see <xref linkend="network-hooks"/>.

	  </para>

	  <para>

	    <replaceable>NAME</replaceable> can be the string

	    <quote><literal>none</literal></quote>; this will not use

	    any specific interface, and will not bring up an interface

	    on startup.  This is not recommended, and only meant for

	    advanced users.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--pubkey=<replaceable

	>FILE</replaceable></option></term>

	<term><option>-p

	<replaceable>FILE</replaceable></option></term>

	<listitem>

	  <para>

	    OpenPGP public key file name.  The default name is

	    <quote><filename>/conf/conf.d/mandos/pubkey.txt</filename

	    ></quote>.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--seckey=<replaceable

	>FILE</replaceable></option></term>

	<term><option>-s

	<replaceable>FILE</replaceable></option></term>

	<listitem>

	  <para>

	    OpenPGP secret key file name.  The default name is

	    <quote><filename>/conf/conf.d/mandos/seckey.txt</filename

	    ></quote>.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--priority=<replaceable

	>STRING</replaceable></option></term>

	<listitem>

	  <xi:include href="../mandos-options.xml"

		      xpointer="priority"/>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--dh-bits=<replaceable

	>BITS</replaceable></option></term>

	<listitem>

	  <para>

	    Sets the number of bits to use for the prime number in the

	    TLS Diffie-Hellman key exchange.  Default is 1024.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--delay=<replaceable

	>SECONDS</replaceable></option></term>

	<listitem>

	  <para>

	    After bringing the network interface up, the program waits

	    for the interface to arrive in a <quote>running</quote>

	    state before proceeding.  During this time, the kernel log

	    level will be lowered to reduce clutter on the system

	    console, alleviating any other plugins which might be

	    using the system console.  This option sets the upper

	    limit of seconds to wait.  The default is 2.5 seconds.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--retry=<replaceable

	>SECONDS</replaceable></option></term>

	<listitem>

	  <para>

	    All Mandos servers are tried repeatedly until a password

	    is received.  This value specifies, in seconds, how long

	    between each successive try <emphasis>for the same

	    server</emphasis>.  The default is 10 seconds.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><option>--network-hook-dir=<replaceable

	>DIR</replaceable></option></term>

	<listitem>

	  <para>

	    Network hook directory.  The default directory is

	    <quote><filename class="directory"

	    >/lib/mandos/network-hooks.d</filename></quote>.

	  </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.

	  </para>

	  <para>

	    It will also enable debug mode in the Avahi and GnuTLS

	    libraries, making them print large amounts of debugging

	    output.

	  </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 is the client part.  It is a plugin started by

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

      <manvolnum>8mandos</manvolnum></citerefentry> which will run in

      an initial <acronym>RAM</acronym> disk environment.

    </para>

    <para>

      This program could, theoretically, be used as a keyscript in

      <filename>/etc/crypttab</filename>, but it would then be

      impossible to enter a password for the encrypted root disk at

      the console, since this program does not read from the console

      at all.  This is why a separate plugin runner (<citerefentry>

      <refentrytitle>plugin-runner</refentrytitle>

      <manvolnum>8mandos</manvolnum></citerefentry>) is used to run

      both this program and others in in parallel,

      <emphasis>one</emphasis> of which (<citerefentry>

      <refentrytitle>password-prompt</refentrytitle>

      <manvolnum>8mandos</manvolnum></citerefentry>) will prompt for

      passwords on the system console.

    </para>

  </refsect1>

  <refsect1 id="exit_status">

    <title>EXIT STATUS</title>

    <para>

      This program will exit with a successful (zero) exit status if a

      server could be found and the password received from it could be

      successfully decrypted and output on standard output.  The

      program will exit with a non-zero exit status only if a critical

      error occurs.  Otherwise, it will forever connect to any

      discovered <application>Mandos</application> servers, trying to

      get a decryptable password and print it.

    </para>

  </refsect1>

  <refsect1 id="environment">

    <title>ENVIRONMENT</title>

    <para>

      This program does not use any environment variables, not even

      the ones provided by <citerefentry><refentrytitle

      >cryptsetup</refentrytitle><manvolnum>8</manvolnum>

    </citerefentry>.

    </para>

  </refsect1>

  <refsect1 id="network-hooks">

    <title>NETWORK HOOKS</title>

    <para>

      If a network interface like a bridge or tunnel is required to

      find a Mandos server, this requires the interface to be up and

      running before <command>&COMMANDNAME;</command> starts looking

      for Mandos servers.  This can be accomplished by creating a

      <quote>network hook</quote> program, and placing it in a special

      directory.

    </para>

    <para>

      Before the network is used (and again before program exit), any

      runnable programs found in the network hook directory are run

      with the argument <quote><literal>start</literal></quote> or

      <quote><literal>stop</literal></quote>.  This should bring up or

      down, respectively, any network interface which

      <command>&COMMANDNAME;</command> should use.

    </para>

    <refsect2 id="hook-requirements">

      <title>REQUIREMENTS</title>

      <para>

	A network hook must be an executable file, and its name must

	consist entirely of upper and lower case letters, digits,

	underscores, and hyphens.

      </para>

      <para>

	A network hook will receive one argument, which can be one of

	the following:

      </para>

      <variablelist>

	<varlistentry>

	  <term><literal>start</literal></term>

	  <listitem>

	    <para>

	      This should make the network hook create (if necessary)

	      and bring up a network interface.

	    </para>

	  </listitem>

	</varlistentry>

	<varlistentry>

	  <term><literal>stop</literal></term>

	  <listitem>

	    <para>

	      This should make the network hook take down a network

	      interface, and delete it if it did not exist previously.

	    </para>

	  </listitem>

	</varlistentry>

	<varlistentry>

	  <term><literal>files</literal></term>

	  <listitem>

	    <para>

	      This should make the network hook print, <emphasis>on

	      separate lines</emphasis>, all the files needed for it

	      to run.  (These files will be copied into the initial

	      RAM filesystem.)  Intended use is for a network hook

	      which is a shell script to print its needed binaries.

	    </para>

	    <para>

	      It is not necessary to print any non-executable files

	      already in the network hook directory, these will be

	      copied implicitly if they otherwise satisfy the name

	      requirement.

	    </para>

	  </listitem>

	</varlistentry>

      </variablelist>

      <para>

	The network hook will be provided with a number of environment

	variables:

      </para>

      <variablelist>

	<varlistentry>

	  <term><envar>MANDOSNETHOOKDIR</envar></term>

	  <listitem>

	    <para>

	      The network hook directory, specified to

	      <command>&COMMANDNAME;</command> by the

	      <option>--network-hook-dir</option> option.  Note: this

	      should <emphasis>always</emphasis> be used by the

	      network hook to refer to itself or any files it may

	      require.

	    </para>

	  </listitem>

	</varlistentry>

	<varlistentry>

	  <term><envar>DEVICE</envar></term>

	  <listitem>

	    <para>

	      The network interface, as specified to

	      <command>&COMMANDNAME;</command> by the

	      <option>--interface</option> option.  If this is not the

	      interface a hook will bring up, there is no reason for a

	      hook to continue.

	    </para>

	  </listitem>

	</varlistentry>

	<varlistentry>

	  <term><envar>MODE</envar></term>

	  <listitem>

	    <para>

	      This will be the same as the first argument;

	      i.e. <quote><literal>start</literal></quote>,

	      <quote><literal>stop</literal></quote>, or

	      <quote><literal>files</literal></quote>.

	    </para>

	  </listitem>

	</varlistentry>

	<varlistentry>

	  <term><envar>VERBOSITY</envar></term>

	  <listitem>

	    <para>

	      This will be the <quote><literal>1</literal></quote> if

	      the <option>--debug</option> option is passed to

	      <command>&COMMANDNAME;</command>, otherwise

	      <quote><literal>0</literal></quote>.

	    </para>

	  </listitem>

	</varlistentry>

	<varlistentry>

	  <term><envar>DELAY</envar></term>

	  <listitem>

	    <para>

	      This will be the same as the <option>--delay</option>

	      option passed to <command>&COMMANDNAME;</command>.

	    </para>

	  </listitem>

	</varlistentry>

      </variablelist>

      <para>

	A hook may not read from standard input, and should be

	restrictive in printing to standard output or standard error

	unless <varname>VERBOSITY</varname> is

	<quote><literal>1</literal></quote>.

      </para>

    </refsect2>

  </refsect1>

  <refsect1 id="files">

    <title>FILES</title>

    <variablelist>

      <varlistentry>

	<term><filename>/conf/conf.d/mandos/pubkey.txt</filename

	></term>

	<term><filename>/conf/conf.d/mandos/seckey.txt</filename

	></term>

	<listitem>

	  <para>

	    OpenPGP public and private key files, in <quote>ASCII

	    Armor</quote> format.  These are the default file names,

	    they can be changed with the <option>--pubkey</option> and

	    <option>--seckey</option> options.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><filename

	class="directory">/lib/mandos/network-hooks.d</filename></term>

	<listitem>

	  <para>

	    Directory where network hooks are located.  Change this

	    with the <option>--network-hook-dir</option> option.  See

	    <xref linkend="network-hooks"/>.

	  </para>

	</listitem>

      </varlistentry>

    </variablelist>

  </refsect1>

<!--   <refsect1 id="bugs"> -->

<!--     <title>BUGS</title> -->

<!--     <para> -->

<!--     </para> -->

<!--   </refsect1> -->

  <refsect1 id="example">

    <title>EXAMPLE</title>

    <para>

      Note that normally, command line options will not be given

      directly, but via options for the Mandos <citerefentry

      ><refentrytitle>plugin-runner</refentrytitle>

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

    </para>

    <informalexample>

      <para>

	Normal invocation needs no options, if the network interface

	is <quote>eth0</quote>:

      </para>

      <para>

	<userinput>&COMMANDNAME;</userinput>

      </para>

    </informalexample>

    <informalexample>

      <para>

	Search for Mandos servers (and connect to them) using another

	interface:

      </para>

      <para>

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

	<userinput>&COMMANDNAME; --interface eth1</userinput>

      </para>

    </informalexample>

    <informalexample>

      <para>

	Run in debug mode, and use a custom key:

      </para>

      <para>

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

<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>

      </para>

    </informalexample>

    <informalexample>

      <para>

	Run in debug mode, with a custom key, and do not use Zeroconf

	to locate a server; connect directly to the IPv6 link-local

	address <quote><systemitem class="ipaddress"

	>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,

	using interface eth2:

      </para>

      <para>

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

<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>

      </para>

    </informalexample>

  </refsect1>

  <refsect1 id="security">

    <title>SECURITY</title>

    <para>

      This program is set-uid to root, but will switch back to the

      original (and presumably non-privileged) user and group after

      bringing up the network interface.

    </para>

    <para>

      To use this program for its intended purpose (see <xref

      linkend="purpose"/>), the password for the root file system will

      have to be given out to be stored in a server computer, after

      having been encrypted using an OpenPGP key.  This encrypted data

      which will be stored in a server can only be decrypted by the

      OpenPGP key, and the data will only be given out to those

      clients who can prove they actually have that key.  This key,

      however, is stored unencrypted on the client side in its initial