1
<?xml version="1.0" encoding="UTF-8"?>
2
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4
<!ENTITY COMMANDNAME "mandos-client">
5
<!ENTITY TIMESTAMP "2015-07-06">
6
<!ENTITY % common SYSTEM "../common.ent">
10
<refentry xmlns:xi="http://www.w3.org/2001/XInclude">
12
<title>Mandos Manual</title>
13
<!-- NWalsh’s docbook scripts use this to generate the footer: -->
14
<productname>Mandos</productname>
15
<productnumber>&version;</productnumber>
16
<date>&TIMESTAMP;</date>
19
<firstname>Björn</firstname>
20
<surname>Påhlsson</surname>
22
<email>belorn@recompile.se</email>
26
<firstname>Teddy</firstname>
27
<surname>Hogeborn</surname>
29
<email>teddy@recompile.se</email>
40
<holder>Teddy Hogeborn</holder>
41
<holder>Björn Påhlsson</holder>
43
<xi:include href="../legalnotice.xml"/>
47
<refentrytitle>&COMMANDNAME;</refentrytitle>
48
<manvolnum>8mandos</manvolnum>
52
<refname><command>&COMMANDNAME;</command></refname>
54
Client for <application>Mandos</application>
60
<command>&COMMANDNAME;</command>
62
<arg choice="plain"><option>--connect
63
<replaceable>ADDRESS</replaceable><literal>:</literal
64
><replaceable>PORT</replaceable></option></arg>
65
<arg choice="plain"><option>-c
66
<replaceable>ADDRESS</replaceable><literal>:</literal
67
><replaceable>PORT</replaceable></option></arg>
71
<arg choice="plain"><option>--interface
72
<replaceable>NAME</replaceable><arg rep='repeat'
73
>,<replaceable>NAME</replaceable></arg></option></arg>
74
<arg choice="plain"><option>-i <replaceable>NAME</replaceable
75
><arg rep='repeat'>,<replaceable>NAME</replaceable></arg
80
<arg choice="plain"><option>--pubkey
81
<replaceable>FILE</replaceable></option></arg>
82
<arg choice="plain"><option>-p
83
<replaceable>FILE</replaceable></option></arg>
87
<arg choice="plain"><option>--seckey
88
<replaceable>FILE</replaceable></option></arg>
89
<arg choice="plain"><option>-s
90
<replaceable>FILE</replaceable></option></arg>
94
<option>--priority <replaceable>STRING</replaceable></option>
98
<option>--dh-bits <replaceable>BITS</replaceable></option>
102
<option>--delay <replaceable>SECONDS</replaceable></option>
106
<option>--retry <replaceable>SECONDS</replaceable></option>
110
<option>--network-hook-dir
111
<replaceable>DIR</replaceable></option>
115
<option>--debug</option>
119
<command>&COMMANDNAME;</command>
121
<arg choice="plain"><option>--help</option></arg>
122
<arg choice="plain"><option>-?</option></arg>
126
<command>&COMMANDNAME;</command>
127
<arg choice="plain"><option>--usage</option></arg>
130
<command>&COMMANDNAME;</command>
132
<arg choice="plain"><option>--version</option></arg>
133
<arg choice="plain"><option>-V</option></arg>
138
<refsect1 id="description">
139
<title>DESCRIPTION</title>
141
<command>&COMMANDNAME;</command> is a client program that
142
communicates with <citerefentry><refentrytitle
143
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
144
to get a password. In slightly more detail, this client program
145
brings up network interfaces, uses the interfaces’ IPv6
146
link-local addresses to get network connectivity, uses Zeroconf
147
to find servers on the local network, and communicates with
148
servers using TLS with an OpenPGP key to ensure authenticity and
149
confidentiality. This client program keeps running, trying all
150
servers on the network, until it receives a satisfactory reply
151
or a TERM signal. After all servers have been tried, all
152
servers are periodically retried. If no servers are found it
153
will wait indefinitely for new servers to appear.
156
The network interfaces are selected like this: If any interfaces
157
are specified using the <option>--interface</option> option,
158
those interface are used. Otherwise,
159
<command>&COMMANDNAME;</command> will use all interfaces that
160
are not loopback interfaces, are not point-to-point interfaces,
161
are capable of broadcasting and do not have the NOARP flag (see
162
<citerefentry><refentrytitle>netdevice</refentrytitle>
163
<manvolnum>7</manvolnum></citerefentry>). (If the
164
<option>--connect</option> option is used, point-to-point
165
interfaces and non-broadcast interfaces are accepted.) If any
166
used interfaces are not up and running, they are first taken up
167
(and later taken down again on program exit).
170
Before network interfaces are selected, all <quote>network
171
hooks</quote> are run; see <xref linkend="network-hooks"/>.
174
This program is not meant to be run directly; it is really meant
175
to run as a plugin of the <application>Mandos</application>
176
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
177
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
178
initial <acronym>RAM</acronym> disk environment because it is
179
specified as a <quote>keyscript</quote> in the <citerefentry>
180
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
181
</citerefentry> file.
185
<refsect1 id="purpose">
186
<title>PURPOSE</title>
188
The purpose of this is to enable <emphasis>remote and unattended
189
rebooting</emphasis> of client host computer with an
190
<emphasis>encrypted root file system</emphasis>. See <xref
191
linkend="overview"/> for details.
195
<refsect1 id="options">
196
<title>OPTIONS</title>
198
This program is commonly not invoked from the command line; it
199
is normally started by the <application>Mandos</application>
200
plugin runner, see <citerefentry><refentrytitle
201
>plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
202
</citerefentry>. Any command line options this program accepts
203
are therefore normally provided by the plugin runner, and not
209
<term><option>--connect=<replaceable
210
>ADDRESS</replaceable><literal>:</literal><replaceable
211
>PORT</replaceable></option></term>
213
<replaceable>ADDRESS</replaceable><literal>:</literal
214
><replaceable>PORT</replaceable></option></term>
217
Do not use Zeroconf to locate servers. Connect directly
218
to only one specified <application>Mandos</application>
219
server. Note that an IPv6 address has colon characters in
220
it, so the <emphasis>last</emphasis> colon character is
221
assumed to separate the address from the port number.
224
Normally, Zeroconf would be used to locate Mandos servers,
225
in which case this option would only be used when testing
232
<term><option>--interface=<replaceable
233
>NAME</replaceable><arg rep='repeat'>,<replaceable
234
>NAME</replaceable></arg></option></term>
236
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
237
>NAME</replaceable></arg></option></term>
240
Comma separated list of network interfaces that will be
241
brought up and scanned for Mandos servers to connect to.
242
The default is the empty string, which will automatically
243
use all appropriate interfaces.
246
If the <option>--connect</option> option is used, and
247
exactly one interface name is specified (except
248
<quote><literal>none</literal></quote>), this specifies
249
the interface to use to connect to the address given.
252
Note that since this program will normally run in the
253
initial RAM disk environment, the interface must be an
254
interface which exists at that stage. Thus, the interface
255
can normally not be a pseudo-interface such as
256
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
257
will not exist until much later in the boot process, and
258
can not be used by this program, unless created by a
259
<quote>network hook</quote> — see <xref
260
linkend="network-hooks"/>.
263
<replaceable>NAME</replaceable> can be the string
264
<quote><literal>none</literal></quote>; this will make
265
<command>&COMMANDNAME;</command> only bring up interfaces
266
specified <emphasis>before</emphasis> this string. This
267
is not recommended, and only meant for advanced users.
273
<term><option>--pubkey=<replaceable
274
>FILE</replaceable></option></term>
276
<replaceable>FILE</replaceable></option></term>
279
OpenPGP public key file name. The default name is
280
<quote><filename>/conf/conf.d/mandos/pubkey.txt</filename
287
<term><option>--seckey=<replaceable
288
>FILE</replaceable></option></term>
290
<replaceable>FILE</replaceable></option></term>
293
OpenPGP secret key file name. The default name is
294
<quote><filename>/conf/conf.d/mandos/seckey.txt</filename
301
<term><option>--priority=<replaceable
302
>STRING</replaceable></option></term>
304
<xi:include href="../mandos-options.xml"
305
xpointer="priority"/>
310
<term><option>--dh-bits=<replaceable
311
>BITS</replaceable></option></term>
314
Sets the number of bits to use for the prime number in the
315
TLS Diffie-Hellman key exchange. The default value is
316
selected automatically based on the OpenPGP key.
322
<term><option>--delay=<replaceable
323
>SECONDS</replaceable></option></term>
326
After bringing a network interface up, the program waits
327
for the interface to arrive in a <quote>running</quote>
328
state before proceeding. During this time, the kernel log
329
level will be lowered to reduce clutter on the system
330
console, alleviating any other plugins which might be
331
using the system console. This option sets the upper
332
limit of seconds to wait. The default is 2.5 seconds.
338
<term><option>--retry=<replaceable
339
>SECONDS</replaceable></option></term>
342
All Mandos servers are tried repeatedly until a password
343
is received. This value specifies, in seconds, how long
344
between each successive try <emphasis>for the same
345
server</emphasis>. The default is 10 seconds.
351
<term><option>--network-hook-dir=<replaceable
352
>DIR</replaceable></option></term>
355
Network hook directory. The default directory is
356
<quote><filename class="directory"
357
>/lib/mandos/network-hooks.d</filename></quote>.
363
<term><option>--debug</option></term>
366
Enable debug mode. This will enable a lot of output to
367
standard error about what the program is doing. The
368
program will still perform all other functions normally.
371
It will also enable debug mode in the Avahi and GnuTLS
372
libraries, making them print large amounts of debugging
379
<term><option>--help</option></term>
380
<term><option>-?</option></term>
383
Gives a help message about options and their meanings.
389
<term><option>--usage</option></term>
392
Gives a short usage message.
398
<term><option>--version</option></term>
399
<term><option>-V</option></term>
402
Prints the program version.
409
<refsect1 id="overview">
410
<title>OVERVIEW</title>
411
<xi:include href="../overview.xml"/>
413
This program is the client part. It is a plugin started by
414
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
415
<manvolnum>8mandos</manvolnum></citerefentry> which will run in
416
an initial <acronym>RAM</acronym> disk environment.
419
This program could, theoretically, be used as a keyscript in
420
<filename>/etc/crypttab</filename>, but it would then be
421
impossible to enter a password for the encrypted root disk at
422
the console, since this program does not read from the console
423
at all. This is why a separate plugin runner (<citerefentry>
424
<refentrytitle>plugin-runner</refentrytitle>
425
<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
426
both this program and others in in parallel,
427
<emphasis>one</emphasis> of which (<citerefentry>
428
<refentrytitle>password-prompt</refentrytitle>
429
<manvolnum>8mandos</manvolnum></citerefentry>) will prompt for
430
passwords on the system console.
434
<refsect1 id="exit_status">
435
<title>EXIT STATUS</title>
437
This program will exit with a successful (zero) exit status if a
438
server could be found and the password received from it could be
439
successfully decrypted and output on standard output. The
440
program will exit with a non-zero exit status only if a critical
441
error occurs. Otherwise, it will forever connect to any
442
discovered <application>Mandos</application> servers, trying to
443
get a decryptable password and print it.
447
<refsect1 id="environment">
448
<title>ENVIRONMENT</title>
451
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
454
This environment variable will be assumed to contain the
455
directory containing any helper executables. The use and
456
nature of these helper executables, if any, is
457
purposefully not documented.
463
This program does not use any other environment variables, not
464
even the ones provided by <citerefentry><refentrytitle
465
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
470
<refsect1 id="network-hooks">
471
<title>NETWORK HOOKS</title>
473
If a network interface like a bridge or tunnel is required to
474
find a Mandos server, this requires the interface to be up and
475
running before <command>&COMMANDNAME;</command> starts looking
476
for Mandos servers. This can be accomplished by creating a
477
<quote>network hook</quote> program, and placing it in a special
481
Before the network is used (and again before program exit), any
482
runnable programs found in the network hook directory are run
483
with the argument <quote><literal>start</literal></quote> or
484
<quote><literal>stop</literal></quote>. This should bring up or
485
down, respectively, any network interface which
486
<command>&COMMANDNAME;</command> should use.
488
<refsect2 id="hook-requirements">
489
<title>REQUIREMENTS</title>
491
A network hook must be an executable file, and its name must
492
consist entirely of upper and lower case letters, digits,
493
underscores, periods, and hyphens.
496
A network hook will receive one argument, which can be one of
501
<term><literal>start</literal></term>
504
This should make the network hook create (if necessary)
505
and bring up a network interface.
510
<term><literal>stop</literal></term>
513
This should make the network hook take down a network
514
interface, and delete it if it did not exist previously.
519
<term><literal>files</literal></term>
522
This should make the network hook print, <emphasis>one
523
file per line</emphasis>, all the files needed for it to
524
run. (These files will be copied into the initial RAM
525
filesystem.) Typical use is for a network hook which is
526
a shell script to print its needed binaries.
529
It is not necessary to print any non-executable files
530
already in the network hook directory, these will be
531
copied implicitly if they otherwise satisfy the name
537
<term><literal>modules</literal></term>
540
This should make the network hook print, <emphasis>on
541
separate lines</emphasis>, all the kernel modules needed
542
for it to run. (These modules will be copied into the
543
initial RAM filesystem.) For instance, a tunnel
545
<quote><literal>tun</literal></quote> module.
551
The network hook will be provided with a number of environment
556
<term><envar>MANDOSNETHOOKDIR</envar></term>
559
The network hook directory, specified to
560
<command>&COMMANDNAME;</command> by the
561
<option>--network-hook-dir</option> option. Note: this
562
should <emphasis>always</emphasis> be used by the
563
network hook to refer to itself or any files in the hook
564
directory it may require.
569
<term><envar>DEVICE</envar></term>
572
The network interfaces, as specified to
573
<command>&COMMANDNAME;</command> by the
574
<option>--interface</option> option, combined to one
575
string and separated by commas. If this is set, and
576
does not contain the interface a hook will bring up,
577
there is no reason for a hook to continue.
582
<term><envar>MODE</envar></term>
585
This will be the same as the first argument;
586
i.e. <quote><literal>start</literal></quote>,
587
<quote><literal>stop</literal></quote>,
588
<quote><literal>files</literal></quote>, or
589
<quote><literal>modules</literal></quote>.
594
<term><envar>VERBOSITY</envar></term>
597
This will be the <quote><literal>1</literal></quote> if
598
the <option>--debug</option> option is passed to
599
<command>&COMMANDNAME;</command>, otherwise
600
<quote><literal>0</literal></quote>.
605
<term><envar>DELAY</envar></term>
608
This will be the same as the <option>--delay</option>
609
option passed to <command>&COMMANDNAME;</command>. Is
610
only set if <envar>MODE</envar> is
611
<quote><literal>start</literal></quote> or
612
<quote><literal>stop</literal></quote>.
617
<term><envar>CONNECT</envar></term>
620
This will be the same as the <option>--connect</option>
621
option passed to <command>&COMMANDNAME;</command>. Is
622
only set if <option>--connect</option> is passed and
623
<envar>MODE</envar> is
624
<quote><literal>start</literal></quote> or
625
<quote><literal>stop</literal></quote>.
631
A hook may not read from standard input, and should be
632
restrictive in printing to standard output or standard error
633
unless <varname>VERBOSITY</varname> is
634
<quote><literal>1</literal></quote>.
639
<refsect1 id="files">
643
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
645
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
649
OpenPGP public and private key files, in <quote>ASCII
650
Armor</quote> format. These are the default file names,
651
they can be changed with the <option>--pubkey</option> and
652
<option>--seckey</option> options.
658
class="directory">/lib/mandos/network-hooks.d</filename></term>
661
Directory where network hooks are located. Change this
662
with the <option>--network-hook-dir</option> option. See
663
<xref linkend="network-hooks"/>.
670
<!-- <refsect1 id="bugs"> -->
671
<!-- <title>BUGS</title> -->
676
<refsect1 id="example">
677
<title>EXAMPLE</title>
679
Note that normally, command line options will not be given
680
directly, but via options for the Mandos <citerefentry
681
><refentrytitle>plugin-runner</refentrytitle>
682
<manvolnum>8mandos</manvolnum></citerefentry>.
686
Normal invocation needs no options, if the network interfaces
687
can be automatically determined:
690
<userinput>&COMMANDNAME;</userinput>
695
Search for Mandos servers (and connect to them) using one
699
<!-- do not wrap this line -->
700
<userinput>&COMMANDNAME; --interface eth1</userinput>
705
Run in debug mode, and use a custom key:
709
<!-- do not wrap this line -->
710
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
716
Run in debug mode, with a custom key, and do not use Zeroconf
717
to locate a server; connect directly to the IPv6 link-local
718
address <quote><systemitem class="ipaddress"
719
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
720
using interface eth2:
724
<!-- do not wrap this line -->
725
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
731
<refsect1 id="security">
732
<title>SECURITY</title>
734
This program is set-uid to root, but will switch back to the
735
original (and presumably non-privileged) user and group after
736
bringing up the network interface.
739
To use this program for its intended purpose (see <xref
740
linkend="purpose"/>), the password for the root file system will
741
have to be given out to be stored in a server computer, after
742
having been encrypted using an OpenPGP key. This encrypted data
743
which will be stored in a server can only be decrypted by the
744
OpenPGP key, and the data will only be given out to those
745
clients who can prove they actually have that key. This key,
746
however, is stored unencrypted on the client side in its initial
747
<acronym>RAM</acronym> disk image file system. This is normally
748
readable by all, but this is normally fixed during installation
749
of this program; file permissions are set so that no-one is able
753
The only remaining weak point is that someone with physical
754
access to the client hard drive might turn off the client
755
computer, read the OpenPGP keys directly from the hard drive,
756
and communicate with the server. To safeguard against this, the
757
server is supposed to notice the client disappearing and stop
758
giving out the encrypted data. Therefore, it is important to
759
set the timeout and checker interval values tightly on the
760
server. See <citerefentry><refentrytitle
761
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
764
It will also help if the checker program on the server is
765
configured to request something from the client which can not be
766
spoofed by someone else on the network, like SSH server key
767
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
768
echo (<quote>ping</quote>) replies.
771
<emphasis>Note</emphasis>: This makes it completely insecure to
772
have <application >Mandos</application> clients which dual-boot
773
to another operating system which is <emphasis>not</emphasis>
774
trusted to keep the initial <acronym>RAM</acronym> disk image
779
<refsect1 id="see_also">
780
<title>SEE ALSO</title>
782
<citerefentry><refentrytitle>intro</refentrytitle>
783
<manvolnum>8mandos</manvolnum></citerefentry>,
784
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
785
<manvolnum>8</manvolnum></citerefentry>,
786
<citerefentry><refentrytitle>crypttab</refentrytitle>
787
<manvolnum>5</manvolnum></citerefentry>,
788
<citerefentry><refentrytitle>mandos</refentrytitle>
789
<manvolnum>8</manvolnum></citerefentry>,
790
<citerefentry><refentrytitle>password-prompt</refentrytitle>
791
<manvolnum>8mandos</manvolnum></citerefentry>,
792
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
793
<manvolnum>8mandos</manvolnum></citerefentry>
798
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
802
Zeroconf is the network protocol standard used for finding
803
Mandos servers on the local network.
809
<ulink url="http://www.avahi.org/">Avahi</ulink>
813
Avahi is the library this program calls to find Zeroconf
820
<ulink url="http://www.gnu.org/software/gnutls/"
825
GnuTLS is the library this client uses to implement TLS for
826
communicating securely with the server, and at the same time
827
send the public OpenPGP key to the server.
833
<ulink url="http://www.gnupg.org/related_software/gpgme/"
838
GPGME is the library used to decrypt the OpenPGP data sent
845
RFC 4291: <citetitle>IP Version 6 Addressing
846
Architecture</citetitle>
851
<term>Section 2.2: <citetitle>Text Representation of
852
Addresses</citetitle></term>
853
<listitem><para/></listitem>
856
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
857
Address</citetitle></term>
858
<listitem><para/></listitem>
861
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
862
Addresses</citetitle></term>
865
This client uses IPv6 link-local addresses, which are
866
immediately usable since a link-local addresses is
867
automatically assigned to a network interface when it
877
RFC 4346: <citetitle>The Transport Layer Security (TLS)
878
Protocol Version 1.1</citetitle>
882
TLS 1.1 is the protocol implemented by GnuTLS.
888
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
892
The data received from the server is binary encrypted
899
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
904
This is implemented by GnuTLS and used by this program so
905
that OpenPGP keys can be used.
913
<!-- Local Variables: -->
914
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
915
<!-- time-stamp-end: "[\"']>" -->
916
<!-- time-stamp-format: "%:y-%02m-%02d" -->