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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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<!ENTITY COMMANDNAME "mandos-client">
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<!ENTITY TIMESTAMP "2018-02-08">
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<!ENTITY % common SYSTEM "../common.ent">
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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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<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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<!-- 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@recompile.se</email>
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<email>belorn@fukt.bsnet.se</email>
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<firstname>Teddy</firstname>
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<surname>Hogeborn</surname>
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<email>teddy@recompile.se</email>
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<email>teddy@fukt.bsnet.se</email>
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<holder>Teddy Hogeborn</holder>
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<holder>Björn Påhlsson</holder>
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<xi:include href="../legalnotice.xml"/>
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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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<refentrytitle>&COMMANDNAME;</refentrytitle>
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<manvolnum>8mandos</manvolnum>
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</refsynopsisdiv>
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<refsect1 id="description">
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<title>DESCRIPTION</title>
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<command>&COMMANDNAME;</command> is a 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 network interfaces, uses the interfaces’ IPv6
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link-local addresses to get network connectivity, uses Zeroconf
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to find servers on the local network, and communicates with
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servers 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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The network interfaces are selected like this: If any interfaces
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are specified using the <option>--interface</option> option,
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those interface are used. Otherwise,
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<command>&COMMANDNAME;</command> will use all interfaces that
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are not loopback interfaces, are not point-to-point interfaces,
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are capable of broadcasting and do not have the NOARP flag (see
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<citerefentry><refentrytitle>netdevice</refentrytitle>
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<manvolnum>7</manvolnum></citerefentry>). (If the
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<option>--connect</option> option is used, point-to-point
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interfaces and non-broadcast interfaces are accepted.) If any
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used interfaces are not up and running, they are first taken up
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(and later taken down again on program exit).
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Before network interfaces are selected, all <quote>network
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hooks</quote> are run; see <xref linkend="network-hooks"/>.
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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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<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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<refsect1 id="options">
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<title>OPTIONS</title>
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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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Commonly not invoked as command lines but from configuration
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file of plugin runner.
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<term><option>--connect=<replaceable
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>ADDRESS</replaceable><literal>:</literal><replaceable
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>IPADDR</replaceable><literal>:</literal><replaceable
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>PORT</replaceable></option></term>
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<replaceable>ADDRESS</replaceable><literal>:</literal
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<replaceable>IPADDR</replaceable><literal>:</literal
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><replaceable>PORT</replaceable></option></term>
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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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Connect directly to a specified mandos server
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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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Normally, Zeroconf would be used to locate Mandos servers,
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in which case this option would only be used when testing
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Directory where the openpgp keyring is
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<term><option>--interface=<replaceable
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>NAME</replaceable><arg rep='repeat'>,<replaceable
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>NAME</replaceable></arg></option></term>
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<term><option>--interface=
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<replaceable>NAME</replaceable></option></term>
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<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
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>NAME</replaceable></arg></option></term>
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<replaceable>NAME</replaceable></option></term>
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Comma separated list of network interfaces that will be
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brought up and scanned for Mandos servers to connect to.
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The default is the empty string, which will automatically
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use all appropriate interfaces.
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If the <option>--connect</option> option is used, and
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exactly one interface name is specified (except
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<quote><literal>none</literal></quote>), this specifies
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the interface to use to connect to the address given.
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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 normally not be a pseudo-interface such as
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<quote>br0</quote> or <quote>tun0</quote>; such interfaces
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will not exist until much later in the boot process, and
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can not be used by this program, unless created by a
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<quote>network hook</quote> — see <xref
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linkend="network-hooks"/>.
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<replaceable>NAME</replaceable> can be the string
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<quote><literal>none</literal></quote>; this will make
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<command>&COMMANDNAME;</command> only bring up interfaces
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specified <emphasis>before</emphasis> this string. This
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is not recommended, and only meant for advanced users.
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Interface that Avahi will connect through
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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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Sets the number of bits to use for the prime number in the
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TLS Diffie-Hellman key exchange. The default value is
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selected automatically based on the OpenPGP key. Note
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that if the <option>--dh-params</option> option is used,
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the values from that file will be used instead.
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<term><option>--dh-params=<replaceable
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>FILE</replaceable></option></term>
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Specifies a PEM-encoded PKCS#3 file to read the parameters
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needed by the TLS Diffie-Hellman key exchange from. If
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this option is not given, or if the file for some reason
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could not be used, the parameters will be generated on
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startup, which will take some time and processing power.
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Those using servers running under time, power or processor
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constraints may want to generate such a file in advance
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<term><option>--delay=<replaceable
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>SECONDS</replaceable></option></term>
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After bringing a 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>--network-hook-dir=<replaceable
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>DIR</replaceable></option></term>
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Network hook directory. The default directory is
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<quote><filename class="directory"
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>/lib/mandos/network-hooks.d</filename></quote>.
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DH bits to use in gnutls communication
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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 (<citerefentry>
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<refentrytitle>password-prompt</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) will prompt for
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passwords on the system console.
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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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<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
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This environment variable will be assumed to contain the
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directory containing any helper executables. The use and
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nature of these helper executables, if any, is
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purposefully not documented.
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This program does not use any other environment variables, not
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even the ones provided by <citerefentry><refentrytitle
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>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
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<refsect1 id="network-hooks">
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<title>NETWORK HOOKS</title>
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If a network interface like a bridge or tunnel is required to
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find a Mandos server, this requires the interface to be up and
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running before <command>&COMMANDNAME;</command> starts looking
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for Mandos servers. This can be accomplished by creating a
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<quote>network hook</quote> program, and placing it in a special
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Before the network is used (and again before program exit), any
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runnable programs found in the network hook directory are run
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with the argument <quote><literal>start</literal></quote> or
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<quote><literal>stop</literal></quote>. This should bring up or
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down, respectively, any network interface which
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<command>&COMMANDNAME;</command> should use.
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<refsect2 id="hook-requirements">
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<title>REQUIREMENTS</title>
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A network hook must be an executable file, and its name must
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consist entirely of upper and lower case letters, digits,
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underscores, periods, and hyphens.
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A network hook will receive one argument, which can be one of
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<term><literal>start</literal></term>
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This should make the network hook create (if necessary)
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and bring up a network interface.
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<term><literal>stop</literal></term>
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This should make the network hook take down a network
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interface, and delete it if it did not exist previously.
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<term><literal>files</literal></term>
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This should make the network hook print, <emphasis>one
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file per line</emphasis>, all the files needed for it to
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run. (These files will be copied into the initial RAM
553
filesystem.) Typical use is for a network hook which is
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a shell script to print its needed binaries.
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It is not necessary to print any non-executable files
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already in the network hook directory, these will be
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copied implicitly if they otherwise satisfy the name
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<term><literal>modules</literal></term>
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This should make the network hook print, <emphasis>on
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separate lines</emphasis>, all the kernel modules needed
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for it to run. (These modules will be copied into the
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initial RAM filesystem.) For instance, a tunnel
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<quote><literal>tun</literal></quote> module.
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The network hook will be provided with a number of environment
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<term><envar>MANDOSNETHOOKDIR</envar></term>
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The network hook directory, specified to
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<command>&COMMANDNAME;</command> by the
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<option>--network-hook-dir</option> option. Note: this
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should <emphasis>always</emphasis> be used by the
591
network hook to refer to itself or any files in the hook
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directory it may require.
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<term><envar>DEVICE</envar></term>
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The network interfaces, as specified to
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<command>&COMMANDNAME;</command> by the
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<option>--interface</option> option, combined to one
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string and separated by commas. If this is set, and
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does not contain the interface a hook will bring up,
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there is no reason for a hook to continue.
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<term><envar>MODE</envar></term>
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This will be the same as the first argument;
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i.e. <quote><literal>start</literal></quote>,
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<quote><literal>stop</literal></quote>,
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<quote><literal>files</literal></quote>, or
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<quote><literal>modules</literal></quote>.
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<term><envar>VERBOSITY</envar></term>
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This will be the <quote><literal>1</literal></quote> if
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the <option>--debug</option> option is passed to
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<command>&COMMANDNAME;</command>, otherwise
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<quote><literal>0</literal></quote>.
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<term><envar>DELAY</envar></term>
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This will be the same as the <option>--delay</option>
637
option passed to <command>&COMMANDNAME;</command>. Is
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only set if <envar>MODE</envar> is
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<quote><literal>start</literal></quote> or
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<quote><literal>stop</literal></quote>.
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<term><envar>CONNECT</envar></term>
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This will be the same as the <option>--connect</option>
649
option passed to <command>&COMMANDNAME;</command>. Is
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only set if <option>--connect</option> is passed and
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<envar>MODE</envar> is
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<quote><literal>start</literal></quote> or
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<quote><literal>stop</literal></quote>.
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A hook may not read from standard input, and should be
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restrictive in printing to standard output or standard error
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unless <varname>VERBOSITY</varname> is
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<quote><literal>1</literal></quote>.
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<refsect1 id="files">
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<title>FILES</title>
671
<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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class="directory">/lib/mandos/network-hooks.d</filename></term>
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Directory where network hooks are located. Change this
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with the <option>--network-hook-dir</option> option. See
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<xref linkend="network-hooks"/>.
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<refsect1 id="bugs">
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<title>BUGS</title>
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<xi:include href="../bugs.xml"/>
703
313
<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 interfaces
714
can be automatically determined:
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<userinput>&COMMANDNAME;</userinput>
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Search for Mandos servers (and connect to them) using one
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<!-- do not wrap this line -->
727
<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"
746
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
747
using interface eth2:
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<!-- do not wrap this line -->
752
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
758
319
<refsect1 id="security">
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320
<title>SECURITY</title>
761
This program is set-uid to root, but will switch back to the
762
original (and presumably non-privileged) user and group after
763
bringing up the network interface.
766
To use this program for its intended purpose (see <xref
767
linkend="purpose"/>), the password for the root file system will
768
have to be given out to be stored in a server computer, after
769
having been encrypted using an OpenPGP key. This encrypted data
770
which will be stored in a server can only be decrypted by the
771
OpenPGP key, and the data will only be given out to those
772
clients who can prove they actually have that key. This key,
773
however, is stored unencrypted on the client side in its initial
774
<acronym>RAM</acronym> disk image file system. This is normally
775
readable by all, but this is normally fixed during installation
776
of this program; file permissions are set so that no-one is able
780
The only remaining weak point is that someone with physical
781
access to the client hard drive might turn off the client
782
computer, read the OpenPGP keys directly from the hard drive,
783
and communicate with the server. To safeguard against this, the
784
server is supposed to notice the client disappearing and stop
785
giving out the encrypted data. Therefore, it is important to
786
set the timeout and checker interval values tightly on the
787
server. See <citerefentry><refentrytitle
788
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
791
It will also help if the checker program on the server is
792
configured to request something from the client which can not be
793
spoofed by someone else on the network, like SSH server key
794
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
795
echo (<quote>ping</quote>) replies.
798
<emphasis>Note</emphasis>: This makes it completely insecure to
799
have <application >Mandos</application> clients which dual-boot
800
to another operating system which is <emphasis>not</emphasis>
801
trusted to keep the initial <acronym>RAM</acronym> disk image
806
325
<refsect1 id="see_also">
807
326
<title>SEE ALSO</title>
809
<citerefentry><refentrytitle>intro</refentrytitle>
810
<manvolnum>8mandos</manvolnum></citerefentry>,
811
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
812
<manvolnum>8</manvolnum></citerefentry>,
813
<citerefentry><refentrytitle>crypttab</refentrytitle>
814
<manvolnum>5</manvolnum></citerefentry>,
815
328
<citerefentry><refentrytitle>mandos</refentrytitle>
816
329
<manvolnum>8</manvolnum></citerefentry>,
817
330
<citerefentry><refentrytitle>password-prompt</refentrytitle>
819
332
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
820
333
<manvolnum>8mandos</manvolnum></citerefentry>
825
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
829
Zeroconf is the network protocol standard used for finding
830
Mandos servers on the local network.
836
<ulink url="http://www.avahi.org/">Avahi</ulink>
840
Avahi is the library this program calls to find Zeroconf
847
<ulink url="https://www.gnutls.org/">GnuTLS</ulink>
851
GnuTLS is the library this client uses to implement TLS for
852
communicating securely with the server, and at the same time
853
send the public OpenPGP key to the server.
859
<ulink url="https://www.gnupg.org/related_software/gpgme/"
864
GPGME is the library used to decrypt the OpenPGP data sent
871
RFC 4291: <citetitle>IP Version 6 Addressing
872
Architecture</citetitle>
877
<term>Section 2.2: <citetitle>Text Representation of
878
Addresses</citetitle></term>
879
<listitem><para/></listitem>
882
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
883
Address</citetitle></term>
884
<listitem><para/></listitem>
887
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
888
Addresses</citetitle></term>
891
This client uses IPv6 link-local addresses, which are
892
immediately usable since a link-local addresses is
893
automatically assigned to a network interface when it
903
RFC 5246: <citetitle>The Transport Layer Security (TLS)
904
Protocol Version 1.2</citetitle>
908
TLS 1.2 is the protocol implemented by GnuTLS.
914
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
918
The data received from the server is binary encrypted
925
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
930
This is implemented by GnuTLS and used by this program so
931
that OpenPGP keys can be used.
337
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
341
<ulink url="http://www.avahi.org/">Avahi</ulink>
346
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
351
url="http://www.gnupg.org/related_software/gpgme/">
356
<citation>RFC 4880: <citetitle>OpenPGP Message
357
Format</citetitle></citation>
361
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
362
Transport Layer Security</citetitle></citation>
366
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
367
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
368
Unicast Addresses</citation>
939
374
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940
375
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941
376
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