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Committer: Teddy Hogeborn
Date: 2008-09-03 17:34:29 UTC
Revision ID: teddy@fukt.bsnet.se-20080903173429-db2mjtddf7mgbx8z

* plugins.d/password-request.xml (OVERVIEW): Refer to
                                             password-prompt(8) by
                                             name.
  (SECURITY): Improved wording.  Add paragraph about insecurity of
              ping.
  (SEE ALSO): Add references to cryptsetup(8) and crypttab(5).
              Changed to be a <variablelist> and added text.

files added:
.bzrignore

COPYING

initramfs-tools-hook

initramfs-tools-hook-conf

initramfs-tools-script

legalnotice.xml

mandos-clients.conf.xml

mandos-keygen

mandos-keygen.xml

mandos-options.xml

mandos.conf.xml

mandos.xml

overview.xml

plugin-runner.xml

plugins.d/password-prompt.xml

plugins.d/password-request.xml

plugins.d/usplash

files removed:
ca.pem

cert.pem

client-cert.pem

client-key.pem

crl.pem

key.pem

files renamed:
server.py => mandos

server.conf => mandos.conf

plugbasedclient.c => plugin-runner.c

plugins.d/passprompt.c => plugins.d/password-prompt.c

plugins.d/mandosclient.c => plugins.d/password-request.c

files modified:
Makefile

TODO

clients.conf

Show diffs side-by-side

added added

removed removed

plugins.d/password-request.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 VERSION "1.0">

<!ENTITY COMMANDNAME "password-request">

<!ENTITY TIMESTAMP "2008-09-03">

<title>Mandos Manual</title>

<productname>Mandos</productname>

<productnumber>&VERSION;</productnumber>

<date>&TIMESTAMP;</date>

<firstname>Björn</firstname>

<surname>Påhlsson</surname>

<email>belorn@fukt.bsnet.se</email>

</address>

</author>

<firstname>Teddy</firstname>

<surname>Hogeborn</surname>

<email>teddy@fukt.bsnet.se</email>

</address>

</author>

</authorgroup>

<holder>Teddy Hogeborn</holder>

<holder>Björn Påhlsson</holder>

</copyright>

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

</refentryinfo>

<refentrytitle>&COMMANDNAME;</refentrytitle>

<manvolnum>8mandos</manvolnum>

</refmeta>

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

Client for mandos

</refpurpose>

</refnamediv>

<command>&COMMANDNAME;</command>

<group>

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

<replaceable>IPADDR</replaceable><literal>:</literal

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

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

<replaceable>IPADDR</replaceable><literal>:</literal

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

</group>

<sbr/>

<group>

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

<replaceable>DIRECTORY</replaceable></option></arg>

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

<replaceable>DIRECTORY</replaceable></option></arg>

</group>

<sbr/>

<group>

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

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

</group>

<sbr/>

<group>

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

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

</group>

<sbr/>

<group>

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

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

</group>

<sbr/>

<arg>

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

</arg>

<sbr/>

<arg>

</arg>

<sbr/>

100

<arg>

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<option>--debug</option>

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</arg>

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</cmdsynopsis>

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<command>&COMMANDNAME;</command>

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</group>

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</cmdsynopsis>

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<command>&COMMANDNAME;</command>

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<arg choice="plain"><option>--usage</option></arg>

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</cmdsynopsis>

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<command>&COMMANDNAME;</command>

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<arg choice="plain"><option>--version</option></arg>

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</group>

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</cmdsynopsis>

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</refsynopsisdiv>

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<title>DESCRIPTION</title>

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<para>

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<command>&COMMANDNAME;</command> is a client program that

128

communicates with <citerefentry><refentrytitle

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

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to get a password. It uses IPv6 link-local addresses to get

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network connectivity, Zeroconf to find servers, and TLS with an

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OpenPGP key to ensure authenticity and confidentiality. It

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keeps running, trying all servers on the network, until it

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receives a satisfactory reply or a TERM signal is recieved.

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</para>

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<para>

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

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

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

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

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

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

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

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</citerefentry> file.

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</para>

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</refsect1>

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<title>PURPOSE</title>

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<para>

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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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</para>

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</refsect1>

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<title>OPTIONS</title>

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<para>

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

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

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plugin runner, see <citerefentry><refentrytitle

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

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

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are therefore normally provided by the plugin runner, and not

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directly.

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</para>

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

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

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

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<term><option>-c

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

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

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<para>

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Do not use Zeroconf to locate servers. Connect directly

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

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server. Note that an IPv6 address has colon characters in

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

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assumed to separate the address from the port number.

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</para>

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<para>

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This option is normally only useful for testing and

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debugging.

189

</para>

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</listitem>

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</varlistentry>

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<term><option>--keydir=<replaceable

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>DIRECTORY</replaceable></option></term>

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<term><option>-d

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<replaceable>DIRECTORY</replaceable></option></term>

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199

<para>

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Directory to read the OpenPGP key files

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<filename>pubkey.txt</filename> and

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<filename>seckey.txt</filename> from. The default is

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<filename>/conf/conf.d/mandos</filename> (in the initial

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<acronym>RAM</acronym> disk environment).

205

</para>

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</listitem>

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</varlistentry>

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<term><option>--interface=

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<term><option>-i

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<para>

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Network interface that will be brought up and scanned for

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Mandos servers to connect to. The default it

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<quote><literal>eth0</literal></quote>.

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</para>

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<para>

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

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specifies the interface to use to connect to the address

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given.

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</para>

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</listitem>

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</varlistentry>

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

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

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<term><option>-p

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<para>

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OpenPGP public key file base name. This will be combined

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with the directory from the <option>--keydir</option>

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option to form an absolute file name. The default name is

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<quote><literal>pubkey.txt</literal></quote>.

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</para>

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</listitem>

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</varlistentry>

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

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

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<term><option>-s

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<para>

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OpenPGP secret key file base name. This will be combined

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with the directory from the <option>--keydir</option>

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option to form an absolute file name. The default name is

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<quote><literal>seckey.txt</literal></quote>.

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</para>

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</listitem>

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</varlistentry>

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

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

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

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xpointer="priority"/>

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</listitem>

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</varlistentry>

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

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

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<para>

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

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TLS Diffie-Hellman key exchange. Default is 1024.

274

</para>

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</listitem>

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</varlistentry>

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<term><option>--debug</option></term>

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<para>

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Enable debug mode. This will enable a lot of output to

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standard error about what the program is doing. The

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program will still perform all other functions normally.

285

</para>

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<para>

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It will also enable debug mode in the Avahi and GnuTLS

288

libraries, making them print large amounts of debugging

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output.

290

</para>

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</listitem>

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</varlistentry>

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<para>

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Gives a help message about options and their meanings.

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</para>

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</listitem>

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</varlistentry>

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<term><option>--usage</option></term>

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<para>

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Gives a short usage message.

309

</para>

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</listitem>

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</varlistentry>

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<term><option>--version</option></term>

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<para>

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Prints the program version.

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</refsect1>

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<title>OVERVIEW</title>

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

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<para>

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This program is the client part. It is a plugin started by

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

331

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

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

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</para>

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<para>

335

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

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

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impossible to enter a password for the encrypted root disk at

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

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

340

<refentrytitle>password-prompt</refentrytitle>

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<manvolnum>8mandos</manvolnum></citerefentry>) does that, which

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will be run in parallell to this one by the plugin runner.

343

</para>

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</refsect1>

345

346

347

<title>EXIT STATUS</title>

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<para>

349

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

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

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successfully decrypted and output on standard output. The

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

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error occurs. Otherwise, it will forever connect to new

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<application>Mandos</application> servers as they appear, trying

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to get a decryptable password.

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</para>

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</refsect1>

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<title>ENVIRONMENT</title>

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<para>

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This program does not use any environment variables, not even

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the ones provided by <citerefentry><refentrytitle

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

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</citerefentry>.

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</para>

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</refsect1>

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<title>FILES</title>

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

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></term>

375

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

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></term>

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<para>

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

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

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

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

383

</para>

384

</listitem>

385

</varlistentry>

386

</variablelist>

387

</refsect1>

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<title>EXAMPLE</title>

397

<para>

398

Note that normally, command line options will not be given

399

directly, but via options for the Mandos <citerefentry

400

><refentrytitle>plugin-runner</refentrytitle>

401

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

402

</para>

403

404

<para>

405

Normal invocation needs no options, if the network interface

406

is <quote>eth0</quote>:

407

</para>

408

<para>

409

<userinput>&COMMANDNAME;</userinput>

410

</para>

411

</informalexample>

412

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<para>

414

Search for Mandos servers on another interface:

415

</para>

416

<para>

417

418

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

419

</para>

420

</informalexample>

421

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<para>

423

Run in debug mode, and use a custom key directory:

424

</para>

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<para>

426

427

<userinput>&COMMANDNAME; --debug --keydir keydir</userinput>

428

</para>

429

</informalexample>

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431

<para>

432

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

433

Zeroconf to locate a server; connect directly to the IPv6

434

address <quote><systemitem class="ipaddress"

435

>2001:db8:f983:bd0b:30de:ae4a:71f2:f672</systemitem></quote>,

436

port 4711, using interface eth2:

437

</para>

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<para>

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441

<userinput>&COMMANDNAME; --debug --keydir keydir --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>

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</para>

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</informalexample>

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</refsect1>

446

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<title>SECURITY</title>

449

<para>

450

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

451

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

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bringing up the network interface.

453

</para>

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<para>

455

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

456

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

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

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having been encrypted using an OpenPGP key. This encrypted data

459

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

460

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

461

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

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

463

<acronym>RAM</acronym> disk image file system. This is normally

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readable by all, but this is normally fixed during installation

465

of this program; file permissions are set so that no-one is able

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to read that file.

467

</para>

468

<para>

469

The only remaining weak point is that someone with physical

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access to the client hard drive might turn off the client

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computer, read the OpenPGP keys directly from the hard drive,

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and communicate with the server. The defense against this is

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that the server is supposed to notice the client disappearing

474

and will stop giving out the encrypted data. Therefore, it is

475

important to set the timeout and checker interval values tightly

476

on the server. See <citerefentry><refentrytitle

477

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

478

</para>

479

<para>

480

It will also help if the checker program on the server is

481

configured to request something from the client which can not be

482

spoofed by someone else on the network, unlike unencrypted

483

<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.

484

</para>

485

<para>

486

<emphasis>Note</emphasis>: This makes it completely insecure to

487

have <application >Mandos</application> clients which dual-boot

488

to another operating system which is <emphasis>not</emphasis>

489

trusted to keep the initial <acronym>RAM</acronym> disk image

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confidential.

491

</para>

492

</refsect1>

493

494

495

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<para>

497

<citerefentry><refentrytitle>cryptsetup</refentrytitle>

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

499

<citerefentry><refentrytitle>crypttab</refentrytitle>

500

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

501

<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>plugin-runner</refentrytitle>

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

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</para>

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510

<term>

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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>

512

</term>

513

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<para>

515

Zeroconf is the network protocol standard used for finding

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Mandos servers on the local network.

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</para>

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</listitem>

519

</varlistentry>

520

521

<term>

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<ulink url="http://www.avahi.org/">Avahi</ulink>

523

</term>

524

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<para>

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Avahi is the library this program calls to find Zeroconf

527

services.

528

</para>

529

</listitem>

530

</varlistentry>

531

532

<term>

533

<ulink url="http://www.gnu.org/software/gnutls/"

534

>GnuTLS</ulink>

535

</term>

536

537

<para>

538

GnuTLS is the library this client uses to implement TLS for

539

communicating securely with the server, and at the same time

540

send the public OpenPGP key to the server.

541

</para>

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</listitem>

543

</varlistentry>

544

545

<term>

546

<ulink url="http://www.gnupg.org/related_software/gpgme/"

547

>GPGME</ulink>

548

</term>

549

550

<para>

551

GPGME is the library used to decrypt the OpenPGP data sent

552

by the server.

553

</para>

554

</listitem>

555

</varlistentry>

556

557

<term>

558

RFC 4291: <citetitle>IP Version 6 Addressing

559

Architecture</citetitle>

560

</term>

561

562

563

564

<term>Section 2.2: <citetitle>Text Representation of

565

Addresses</citetitle></term>

566

567

</varlistentry>

568

569

<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6

570

Address</citetitle></term>

571

572

</varlistentry>

573

574

<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast

575

Addresses</citetitle></term>

576

577

<para>

578

This client uses IPv6 link-local addresses, which are

579

immediately usable since a link-local addresses is

580

automatically assigned to a network interfaces when it

581

is brought up.

582

</para>

583

</listitem>

584

</varlistentry>

585

</variablelist>

586

</listitem>

587

</varlistentry>

588

589

<term>

590

RFC 4346: <citetitle>The Transport Layer Security (TLS)

591

Protocol Version 1.1</citetitle>

592

</term>

593

594

<para>

595

TLS 1.1 is the protocol implemented by GnuTLS.

596

</para>

597

</listitem>

598

</varlistentry>

599

600

<term>

601

RFC 4880: <citetitle>OpenPGP Message Format</citetitle>

602

</term>

603

604

<para>

605

The data received from the server is binary encrypted

606

OpenPGP data.

607

</para>

608

</listitem>

609

</varlistentry>

610

611

<term>

612

RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer

613

Security</citetitle>

614

</term>

615

616

<para>

617

This is implemented by GnuTLS and used by this program so

618

that OpenPGP keys can be used.

619

</para>

620

</listitem>

621

</varlistentry>

622

</variablelist>

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</refsect1>

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</refentry>

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