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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY COMMANDNAME "mandos-client">
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<!ENTITY TIMESTAMP "2019-02-10">
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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 "2008-09-03">
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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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<refentrytitle>&COMMANDNAME;</refentrytitle>
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<manvolnum>8mandos</manvolnum>
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<refname><command>&COMMANDNAME;</command></refname>
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Client for <application>Mandos</application>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--connect
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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></arg>
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<arg choice="plain"><option>-c
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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></arg>
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<arg choice="plain"><option>--keydir
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg choice="plain"><option>-d
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg choice="plain"><option>--interface
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<replaceable>NAME</replaceable><arg rep='repeat'
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>,<replaceable>NAME</replaceable></arg></option></arg>
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<arg choice="plain"><option>-i <replaceable>NAME</replaceable
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><arg rep='repeat'>,<replaceable>NAME</replaceable></arg
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<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>-i
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<replaceable>NAME</replaceable></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 client program that
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communicates with <citerefentry><refentrytitle
167
129
>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 a raw public key to ensure authenticity
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and confidentiality. This client program keeps running, trying
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all servers on the network, until it receives a satisfactory
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reply 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
181
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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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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This program is not meant to be run directly; it is really meant
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assumed to separate the address from the port number.
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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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This option is normally only useful for testing and
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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>--keydir=<replaceable
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>DIRECTORY</replaceable></option></term>
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<replaceable>DIRECTORY</replaceable></option></term>
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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).
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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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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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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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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 GnuTLS security
369
profile set in its priority string. Note that if the
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<option>--dh-params</option> option is used, the values
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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.
386
Those using servers running under time, power or processor
387
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>
398
After bringing a network interface up, the program waits
399
for the interface to arrive in a <quote>running</quote>
400
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
404
limit of seconds to wait. The default is 2.5 seconds.
410
<term><option>--retry=<replaceable
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>SECONDS</replaceable></option></term>
414
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
417
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
428
<quote><filename class="directory"
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>/lib/mandos/network-hooks.d</filename></quote>.
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TLS Diffie-Hellman key exchange. Default is 1024.
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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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error occurs. Otherwise, it will forever connect to new
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<application>Mandos</application> servers as they appear, trying
353
to get a decryptable password.
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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 purposely
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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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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="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
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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
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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>
657
This will be the same as the first argument;
658
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>.
666
<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>.
677
<term><envar>DELAY</envar></term>
680
This will be the same as the <option>--delay</option>
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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>
692
This will be the same as the <option>--connect</option>
693
option passed to <command>&COMMANDNAME;</command>. Is
694
only set if <option>--connect</option> is passed and
695
<envar>MODE</envar> is
696
<quote><literal>start</literal></quote> or
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<quote><literal>stop</literal></quote>.
703
A hook may not read from standard input, and should be
704
restrictive in printing to standard output or standard error
705
unless <varname>VERBOSITY</varname> is
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<quote><literal>1</literal></quote>.
711
<refsect1 id="files">
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368
<title>FILES</title>
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</informalexample>
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<informalexample>
790
Run in debug mode, and use custom keys:
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Run in debug mode, and use a custom key directory:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --tls-pubkey keydir/tls-pubkey.pem --tls-privkey keydir/tls-privkey.pem</userinput>
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --keydir keydir</userinput>
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</informalexample>
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<informalexample>
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Run in debug mode, with custom keys, and do not use Zeroconf
802
to locate a server; connect directly to the IPv6 link-local
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Run in debug mode, with a custom key directory, and do not use
431
Zeroconf to locate a server; connect directly to the IPv6
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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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>2001:db8:f983:bd0b:30de:ae4a:71f2:f672</systemitem></quote>,
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port 4711, 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 --tls-pubkey keydir/tls-pubkey.pem --tls-privkey keydir/tls-privkey.pem --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
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<userinput>&COMMANDNAME; --debug --keydir keydir --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>
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</informalexample>
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<refsect1 id="security">
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<title>SECURITY</title>
819
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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
821
bringing up the network interface.
449
original user and group after bringing up the network interface.
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452
To use this program for its intended purpose (see <xref
838
466
The only remaining weak point is that someone with physical
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467
access to the client hard drive might turn off the client
840
computer, read the OpenPGP and TLS keys directly from the hard
841
drive, and communicate with the server. To safeguard against
842
this, the server is supposed to notice the client disappearing
843
and stop giving out the encrypted data. Therefore, it is
468
computer, read the OpenPGP keys directly from the hard drive,
469
and communicate with the server. The defense against this is
470
that the server is supposed to notice the client disappearing
471
and will stop giving out the encrypted data. Therefore, it is
844
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important to set the timeout and checker interval values tightly
845
473
on the server. See <citerefentry><refentrytitle
846
474
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
849
It will also help if the checker program on the server is
850
configured to request something from the client which can not be
851
spoofed by someone else on the network, like SSH server key
852
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
853
echo (<quote>ping</quote>) replies.
856
<emphasis>Note</emphasis>: This makes it completely insecure to
857
have <application >Mandos</application> clients which dual-boot
858
to another operating system which is <emphasis>not</emphasis>
859
trusted to keep the initial <acronym>RAM</acronym> disk image
477
<emphasis>Note</emphasis>: This makes it impossible to have
478
<application >Mandos</application> clients which dual-boot to
479
another operating system which does <emphasis>not</emphasis> run
480
a <application>Mandos</application> client.
864
484
<refsect1 id="see_also">
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<title>SEE ALSO</title>
867
<citerefentry><refentrytitle>intro</refentrytitle>
868
<manvolnum>8mandos</manvolnum></citerefentry>,
869
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
870
<manvolnum>8</manvolnum></citerefentry>,
871
<citerefentry><refentrytitle>crypttab</refentrytitle>
872
<manvolnum>5</manvolnum></citerefentry>,
873
487
<citerefentry><refentrytitle>mandos</refentrytitle>
874
488
<manvolnum>8</manvolnum></citerefentry>,
875
489
<citerefentry><refentrytitle>password-prompt</refentrytitle>
877
491
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
878
492
<manvolnum>8mandos</manvolnum></citerefentry>
883
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
887
Zeroconf is the network protocol standard used for finding
888
Mandos servers on the local network.
894
<ulink url="http://www.avahi.org/">Avahi</ulink>
898
Avahi is the library this program calls to find Zeroconf
905
<ulink url="https://www.gnutls.org/">GnuTLS</ulink>
909
GnuTLS is the library this client uses to implement TLS for
910
communicating securely with the server, and at the same time
911
send the public key to the server.
917
<ulink url="https://www.gnupg.org/related_software/gpgme/"
922
GPGME is the library used to decrypt the OpenPGP data sent
929
RFC 4291: <citetitle>IP Version 6 Addressing
930
Architecture</citetitle>
935
<term>Section 2.2: <citetitle>Text Representation of
936
Addresses</citetitle></term>
937
<listitem><para/></listitem>
940
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
941
Address</citetitle></term>
942
<listitem><para/></listitem>
945
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
946
Addresses</citetitle></term>
949
This client uses IPv6 link-local addresses, which are
950
immediately usable since a link-local addresses is
951
automatically assigned to a network interface when it
961
RFC 5246: <citetitle>The Transport Layer Security (TLS)
962
Protocol Version 1.2</citetitle>
966
TLS 1.2 is the protocol implemented by GnuTLS.
972
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
976
The data received from the server is binary encrypted
983
RFC 7250: <citetitle>Using Raw Public Keys in Transport
984
Layer Security (TLS) and Datagram Transport Layer Security
989
This is implemented by GnuTLS in version 3.6.6 and is, if
990
present, used by this program so that raw public keys can be
997
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
1002
This is implemented by GnuTLS before version 3.6.0 and is,
1003
if present, used by this program so that OpenPGP keys can be
496
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
500
<ulink url="http://www.avahi.org/">Avahi</ulink>
505
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
510
url="http://www.gnupg.org/related_software/gpgme/"
515
<citation>RFC 4880: <citetitle>OpenPGP Message
516
Format</citetitle></citation>
520
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
521
Transport Layer Security</citetitle></citation>
525
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
526
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
527
Unicast Addresses</citation>
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