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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 "2019-02-09">
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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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127
<command>&COMMANDNAME;</command> is a client program that
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128
communicates with <citerefentry><refentrytitle
166
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
180
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
189
used interfaces are not up and running, they are first taken up
190
(and later taken down again on program exit).
193
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
131
network connectivity, Zeroconf to find servers, and TLS with an
132
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.
247
Normally, Zeroconf would be used to locate Mandos servers,
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in which case this option would only be used when testing
187
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.
265
The default is the empty string, which will automatically
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use all appropriate interfaces.
269
If the <option>--connect</option> option is used, and
270
exactly one interface name is specified (except
271
<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
276
initial RAM disk environment, the interface must be an
277
interface which exists at that stage. Thus, the interface
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can normally not be a pseudo-interface such as
279
<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"/>.
286
<replaceable>NAME</replaceable> can be the string
287
<quote><literal>none</literal></quote>; this will make
288
<command>&COMMANDNAME;</command> only bring up interfaces
289
specified <emphasis>before</emphasis> this string. This
290
is not recommended, and only meant for advanced users.
216
Network interface that will be brought up and scanned for
217
Mandos servers to connect to. The default it
218
<quote><literal>eth0</literal></quote>.
221
If the <option>--connect</option> option is used, this
222
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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269
>BITS</replaceable></option></term>
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Sets the number of bits to use for the prime number in the
366
TLS Diffie-Hellman key exchange. The default value is
367
selected automatically based on the GnuTLS security
368
profile set in its priority string. Note that if the
369
<option>--dh-params</option> option is used, the values
370
from that file will be used instead.
376
<term><option>--dh-params=<replaceable
377
>FILE</replaceable></option></term>
380
Specifies a PEM-encoded PKCS#3 file to read the parameters
381
needed by the TLS Diffie-Hellman key exchange from. If
382
this option is not given, or if the file for some reason
383
could not be used, the parameters will be generated on
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startup, which will take some time and processing power.
385
Those using servers running under time, power or processor
386
constraints may want to generate such a file in advance
393
<term><option>--delay=<replaceable
394
>SECONDS</replaceable></option></term>
397
After bringing a network interface up, the program waits
398
for the interface to arrive in a <quote>running</quote>
399
state before proceeding. During this time, the kernel log
400
level will be lowered to reduce clutter on the system
401
console, alleviating any other plugins which might be
402
using the system console. This option sets the upper
403
limit of seconds to wait. The default is 2.5 seconds.
409
<term><option>--retry=<replaceable
410
>SECONDS</replaceable></option></term>
413
All Mandos servers are tried repeatedly until a password
414
is received. This value specifies, in seconds, how long
415
between each successive try <emphasis>for the same
416
server</emphasis>. The default is 10 seconds.
422
<term><option>--network-hook-dir=<replaceable
423
>DIR</replaceable></option></term>
426
Network hook directory. The default directory is
427
<quote><filename class="directory"
428
>/lib/mandos/network-hooks.d</filename></quote>.
273
TLS Diffie-Hellman key exchange. Default is 1024.
509
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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
513
discovered <application>Mandos</application> servers, trying to
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get a decryptable password and print it.
351
error occurs. Otherwise, it will forever connect to new
352
<application>Mandos</application> servers as they appear, trying
353
to get a decryptable password.
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357
<refsect1 id="environment">
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<title>ENVIRONMENT</title>
522
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
525
This environment variable will be assumed to contain the
526
directory containing any helper executables. The use and
527
nature of these helper executables, if any, is
528
purposefully not documented.
534
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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362
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
541
<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
547
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
554
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
563
consist entirely of upper and lower case letters, digits,
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underscores, periods, and hyphens.
567
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)
576
and bring up a network interface.
581
<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.
590
<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
595
run. (These files will be copied into the initial RAM
596
filesystem.) Typical use is for a network hook which is
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a shell script to print its needed binaries.
600
It is not necessary to print any non-executable files
601
already in the network hook directory, these will be
602
copied implicitly if they otherwise satisfy the name
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<term><literal>modules</literal></term>
611
This should make the network hook print, <emphasis>on
612
separate lines</emphasis>, all the kernel modules needed
613
for it to run. (These modules will be copied into the
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initial RAM filesystem.) For instance, a tunnel
616
<quote><literal>tun</literal></quote> module.
622
The network hook will be provided with a number of environment
627
<term><envar>MANDOSNETHOOKDIR</envar></term>
630
The network hook directory, specified to
631
<command>&COMMANDNAME;</command> by the
632
<option>--network-hook-dir</option> option. Note: this
633
should <emphasis>always</emphasis> be used by the
634
network hook to refer to itself or any files in the hook
635
directory it may require.
640
<term><envar>DEVICE</envar></term>
643
The network interfaces, as specified to
644
<command>&COMMANDNAME;</command> by the
645
<option>--interface</option> option, combined to one
646
string and separated by commas. If this is set, and
647
does not contain the interface a hook will bring up,
648
there is no reason for a hook to continue.
653
<term><envar>MODE</envar></term>
656
This will be the same as the first argument;
657
i.e. <quote><literal>start</literal></quote>,
658
<quote><literal>stop</literal></quote>,
659
<quote><literal>files</literal></quote>, or
660
<quote><literal>modules</literal></quote>.
665
<term><envar>VERBOSITY</envar></term>
668
This will be the <quote><literal>1</literal></quote> if
669
the <option>--debug</option> option is passed to
670
<command>&COMMANDNAME;</command>, otherwise
671
<quote><literal>0</literal></quote>.
676
<term><envar>DELAY</envar></term>
679
This will be the same as the <option>--delay</option>
680
option passed to <command>&COMMANDNAME;</command>. Is
681
only set if <envar>MODE</envar> is
682
<quote><literal>start</literal></quote> or
683
<quote><literal>stop</literal></quote>.
688
<term><envar>CONNECT</envar></term>
691
This will be the same as the <option>--connect</option>
692
option passed to <command>&COMMANDNAME;</command>. Is
693
only set if <option>--connect</option> is passed and
694
<envar>MODE</envar> is
695
<quote><literal>start</literal></quote> or
696
<quote><literal>stop</literal></quote>.
702
A hook may not read from standard input, and should be
703
restrictive in printing to standard output or standard error
704
unless <varname>VERBOSITY</varname> is
705
<quote><literal>1</literal></quote>.
710
<refsect1 id="files">
711
368
<title>FILES</title>
786
418
</informalexample>
787
419
<informalexample>
789
Run in debug mode, and use custom keys:
421
Run in debug mode, and use a custom key directory:
793
<!-- do not wrap this line -->
794
<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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427
</informalexample>
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<informalexample>
800
Run in debug mode, with custom keys, and do not use Zeroconf
801
to locate a server; connect directly to the IPv6 link-local
430
Run in debug mode, with a custom key directory, and do not use
431
Zeroconf to locate a server; connect directly to the IPv6
802
432
address <quote><systemitem class="ipaddress"
803
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
804
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>
439
<userinput>&COMMANDNAME; --debug --keydir keydir --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>
812
442
</informalexample>
815
445
<refsect1 id="security">
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<title>SECURITY</title>
818
This program is set-uid to root, but will switch back to the
819
original (and presumably non-privileged) user and group after
820
bringing up the network interface.
823
To use this program for its intended purpose (see <xref
824
linkend="purpose"/>), the password for the root file system will
825
have to be given out to be stored in a server computer, after
826
having been encrypted using an OpenPGP key. This encrypted data
827
which will be stored in a server can only be decrypted by the
828
OpenPGP key, and the data will only be given out to those
829
clients who can prove they actually have that key. This key,
830
however, is stored unencrypted on the client side in its initial
831
<acronym>RAM</acronym> disk image file system. This is normally
832
readable by all, but this is normally fixed during installation
833
of this program; file permissions are set so that no-one is able
837
The only remaining weak point is that someone with physical
838
access to the client hard drive might turn off the client
839
computer, read the OpenPGP and TLS keys directly from the hard
840
drive, and communicate with the server. To safeguard against
841
this, the server is supposed to notice the client disappearing
842
and stop giving out the encrypted data. Therefore, it is
843
important to set the timeout and checker interval values tightly
844
on the server. See <citerefentry><refentrytitle
845
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
848
It will also help if the checker program on the server is
849
configured to request something from the client which can not be
850
spoofed by someone else on the network, like SSH server key
851
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
852
echo (<quote>ping</quote>) replies.
855
<emphasis>Note</emphasis>: This makes it completely insecure to
856
have <application >Mandos</application> clients which dual-boot
857
to another operating system which is <emphasis>not</emphasis>
858
trusted to keep the initial <acronym>RAM</acronym> disk image
863
451
<refsect1 id="see_also">
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<title>SEE ALSO</title>
866
<citerefentry><refentrytitle>intro</refentrytitle>
867
<manvolnum>8mandos</manvolnum></citerefentry>,
868
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
869
<manvolnum>8</manvolnum></citerefentry>,
870
<citerefentry><refentrytitle>crypttab</refentrytitle>
871
<manvolnum>5</manvolnum></citerefentry>,
872
454
<citerefentry><refentrytitle>mandos</refentrytitle>
873
455
<manvolnum>8</manvolnum></citerefentry>,
874
456
<citerefentry><refentrytitle>password-prompt</refentrytitle>
876
458
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
877
459
<manvolnum>8mandos</manvolnum></citerefentry>
882
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
886
Zeroconf is the network protocol standard used for finding
887
Mandos servers on the local network.
893
<ulink url="http://www.avahi.org/">Avahi</ulink>
897
Avahi is the library this program calls to find Zeroconf
904
<ulink url="https://www.gnutls.org/">GnuTLS</ulink>
908
GnuTLS is the library this client uses to implement TLS for
909
communicating securely with the server, and at the same time
910
send the public key to the server.
916
<ulink url="https://www.gnupg.org/related_software/gpgme/"
921
GPGME is the library used to decrypt the OpenPGP data sent
928
RFC 4291: <citetitle>IP Version 6 Addressing
929
Architecture</citetitle>
934
<term>Section 2.2: <citetitle>Text Representation of
935
Addresses</citetitle></term>
936
<listitem><para/></listitem>
939
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
940
Address</citetitle></term>
941
<listitem><para/></listitem>
944
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
945
Addresses</citetitle></term>
948
This client uses IPv6 link-local addresses, which are
949
immediately usable since a link-local addresses is
950
automatically assigned to a network interface when it
960
RFC 5246: <citetitle>The Transport Layer Security (TLS)
961
Protocol Version 1.2</citetitle>
965
TLS 1.2 is the protocol implemented by GnuTLS.
971
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
975
The data received from the server is binary encrypted
982
RFC 7250: <citetitle>Using Raw Public Keys in Transport
983
Layer Security (TLS) and Datagram Transport Layer Security
988
This is implemented by GnuTLS in version 3.6.6 and is, if
989
present, used by this program so that raw public keys can be
996
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
1001
This is implemented by GnuTLS before version 3.6.0 and is,
1002
if present, used by this program so that OpenPGP keys can be
463
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
467
<ulink url="http://www.avahi.org/">Avahi</ulink>
472
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
477
url="http://www.gnupg.org/related_software/gpgme/"
482
<citation>RFC 4880: <citetitle>OpenPGP Message
483
Format</citetitle></citation>
487
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
488
Transport Layer Security</citetitle></citation>
492
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
493
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
494
Unicast Addresses</citation>
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