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<!ENTITY VERSION "1.0">
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<!ENTITY COMMANDNAME "password-request">
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<!ENTITY TIMESTAMP "2008-08-31">
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<!ENTITY COMMANDNAME "mandos-client">
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<!ENTITY TIMESTAMP "2011-10-03">
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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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<option>--delay <replaceable>SECONDS</replaceable></option>
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<option>--retry <replaceable>SECONDS</replaceable></option>
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<option>--debug</option>
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<command>&COMMANDNAME;</command>
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<group choice="req">
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<arg choice='plain'><option>--help</option></arg>
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<arg choice='plain'><option>-?</option></arg>
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<arg choice="plain"><option>--help</option></arg>
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<arg choice="plain"><option>-?</option></arg>
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<command>&COMMANDNAME;</command>
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<arg choice='plain'><option>--usage</option></arg>
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<arg choice="plain"><option>--usage</option></arg>
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<command>&COMMANDNAME;</command>
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<group choice="req">
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<arg choice='plain'><option>--version</option></arg>
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<arg choice='plain'><option>-V</option></arg>
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<arg choice="plain"><option>--version</option></arg>
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<arg choice="plain"><option>-V</option></arg>
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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 mandos plugin that works
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like a client program that through avahi detects mandos servers,
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sets up a gnutls connect and request a encrypted password. Any
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passwords given is automaticly decrypted and passed to
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<command>&COMMANDNAME;</command> is a client program that
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communicates with <citerefentry><refentrytitle
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>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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to get a password. In slightly more detail, this client program
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brings up a network interface, uses the interface’s IPv6
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link-local address to get network connectivity, uses Zeroconf to
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find servers on the local network, and communicates with servers
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using TLS with an OpenPGP key to ensure authenticity and
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confidentiality. This client program keeps running, trying all
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servers on the network, until it receives a satisfactory reply
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or a TERM signal. After all servers have been tried, all
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servers are periodically retried. If no servers are found it
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will wait indefinitely for new servers to appear.
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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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<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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<refsect1 id="options">
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<title>OPTIONS</title>
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Commonly not invoked as command lines but from configuration
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file of plugin runner.
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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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<term><option>--connect=<replaceable
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>IPADDR</replaceable><literal>:</literal><replaceable
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>ADDRESS</replaceable><literal>:</literal><replaceable
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>PORT</replaceable></option></term>
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<replaceable>IPADDR</replaceable><literal>:</literal
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<replaceable>ADDRESS</replaceable><literal>:</literal
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><replaceable>PORT</replaceable></option></term>
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Connect directly to a specified mandos server
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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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<term><option>--keydir=<replaceable
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>DIRECTORY</replaceable></option></term>
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<replaceable>DIRECTORY</replaceable></option></term>
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Directory where the openpgp keyring is
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This option is normally only useful for testing and
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<term><option>--interface=
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<replaceable>NAME</replaceable></option></term>
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<term><option>--interface=<replaceable
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>NAME</replaceable></option></term>
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<replaceable>NAME</replaceable></option></term>
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Interface that Avahi will connect through
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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 is the empty
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string, which will automatically choose an appropriate
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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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Note that since this program will normally run in the
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initial RAM disk environment, the interface must be an
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interface which exists at that stage. Thus, the interface
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can not be a pseudo-interface such as <quote>br0</quote>
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or <quote>tun0</quote>; such interfaces will not exist
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until much later in the boot process, and can not be used
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<replaceable>NAME</replaceable> can be the string
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<quote><literal>none</literal></quote>; this will not use
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any specific interface, and will not bring up an interface
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on startup. This is not recommended, and only meant for
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<term><option>--pubkey=<replaceable
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>FILE</replaceable></option></term>
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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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<term><option>--dh-bits=<replaceable
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>BITS</replaceable></option></term>
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DH bits to use in gnutls communication
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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.
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<term><option>--delay=<replaceable
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>SECONDS</replaceable></option></term>
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After bringing the network interface up, the program waits
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for the interface to arrive in a <quote>running</quote>
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state before proceeding. During this time, the kernel log
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level will be lowered to reduce clutter on the system
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console, alleviating any other plugins which might be
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using the system console. This option sets the upper
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limit of seconds to wait. The default is 2.5 seconds.
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<term><option>--retry=<replaceable
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>SECONDS</replaceable></option></term>
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All Mandos servers are tried repeatedly until a password
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is received. This value specifies, in seconds, how long
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between each successive try <emphasis>for the same
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server</emphasis>. The default is 10 seconds.
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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 is the client part. It is a plugin started by
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry> which will run in
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an initial <acronym>RAM</acronym> disk environment.
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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 runner (<citerefentry>
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<refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
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both this program and others in in parallel,
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<emphasis>one</emphasis> of which will prompt for passwords on
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<refsect1 id="exit_status">
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<title>EXIT STATUS</title>
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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 any
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discovered <application>Mandos</application> servers, trying to
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get a decryptable password and print it.
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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, 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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<refsect1 id="files">
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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><filename>/conf/conf.d/mandos/seckey.txt</filename
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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.
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<!-- <refsect1 id="bugs"> -->
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<!-- <title>BUGS</title> -->
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<refsect1 id="example">
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<title>EXAMPLE</title>
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Note that normally, command line options will not be given
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directly, but via options for the Mandos <citerefentry
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><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>.
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Normal invocation needs no options, if the network interface
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is <quote>eth0</quote>:
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<userinput>&COMMANDNAME;</userinput>
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Search for Mandos servers (and connect to them) using another
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --interface eth1</userinput>
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Run in debug mode, and use a custom key:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
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Run in debug mode, with a custom key, and do not use Zeroconf
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to locate a server; connect directly to the IPv6 link-local
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address <quote><systemitem class="ipaddress"
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>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
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using interface eth2:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
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<refsect1 id="security">
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<title>SECURITY</title>
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This program is set-uid to root, but will switch back to the
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original (and presumably non-privileged) user and group after
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bringing up the network interface.
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To use this program for its intended purpose (see <xref
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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
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which will be stored in a server can only be decrypted by the
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OpenPGP key, and the data will only be given out to those
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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
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<acronym>RAM</acronym> disk image file system. This is normally
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readable by all, but this is normally fixed during installation
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of this program; file permissions are set so that no-one is able
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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. To safeguard against this, the
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server is supposed to notice the client disappearing and stop
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giving out the encrypted data. Therefore, it is important to
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set the timeout and checker interval values tightly on the
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server. See <citerefentry><refentrytitle
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>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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It will also help if the checker program on the server is
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configured to request something from the client which can not be
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spoofed by someone else on the network, unlike unencrypted
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<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
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<emphasis>Note</emphasis>: This makes it completely insecure to
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have <application >Mandos</application> clients which dual-boot
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to another operating system which is <emphasis>not</emphasis>
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trusted to keep the initial <acronym>RAM</acronym> disk image
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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>mandos</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>password-prompt</refentrytitle>
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>
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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
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<ulink url="http://www.avahi.org/">Avahi</ulink>
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url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
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url="http://www.gnupg.org/related_software/gpgme/">
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<citation>RFC 4880: <citetitle>OpenPGP Message
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Format</citetitle></citation>
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<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
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Transport Layer Security</citetitle></citation>
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<citation>RFC 4291: <citetitle>IP Version 6 Addressing
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Architecture</citetitle>, section 2.5.6, Link-Local IPv6
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Unicast Addresses</citation>
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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
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Zeroconf is the network protocol standard used for finding
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Mandos servers on the local network.
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<ulink url="http://www.avahi.org/">Avahi</ulink>
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Avahi is the library this program calls to find Zeroconf
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<ulink url="http://www.gnu.org/software/gnutls/"
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GnuTLS is the library this client uses to implement TLS for
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communicating securely with the server, and at the same time
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send the public OpenPGP key to the server.
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<ulink url="http://www.gnupg.org/related_software/gpgme/"
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GPGME is the library used to decrypt the OpenPGP data sent
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RFC 4291: <citetitle>IP Version 6 Addressing
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Architecture</citetitle>
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<term>Section 2.2: <citetitle>Text Representation of
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Addresses</citetitle></term>
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<listitem><para/></listitem>
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<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
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Address</citetitle></term>
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<listitem><para/></listitem>
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<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
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Addresses</citetitle></term>
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This client uses IPv6 link-local addresses, which are
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immediately usable since a link-local addresses is
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automatically assigned to a network interfaces when it
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RFC 4346: <citetitle>The Transport Layer Security (TLS)
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Protocol Version 1.1</citetitle>
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TLS 1.1 is the protocol implemented by GnuTLS.
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RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
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The data received from the server is binary encrypted
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RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
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This is implemented by GnuTLS and used by this program so
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that OpenPGP keys can be used.
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