143
122
</refsynopsisdiv>
145
124
<refsect1 id="description">
146
125
<title>DESCRIPTION</title>
148
127
<command>&COMMANDNAME;</command> is a client program that
149
128
communicates with <citerefentry><refentrytitle
150
129
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
151
to get a password. In slightly more detail, this client program
152
brings up network interfaces, uses the interfaces’ IPv6
153
link-local addresses to get network connectivity, uses Zeroconf
154
to find servers on the local network, and communicates with
155
servers using TLS with an OpenPGP key to ensure authenticity and
156
confidentiality. This client program keeps running, trying all
157
servers on the network, until it receives a satisfactory reply
158
or a TERM signal. After all servers have been tried, all
159
servers are periodically retried. If no servers are found it
160
will wait indefinitely for new servers to appear.
163
The network interfaces are selected like this: If any interfaces
164
are specified using the <option>--interface</option> option,
165
those interface are used. Otherwise,
166
<command>&COMMANDNAME;</command> will use all interfaces that
167
are not loopback interfaces, are not point-to-point interfaces,
168
are capable of broadcasting and do not have the NOARP flag (see
169
<citerefentry><refentrytitle>netdevice</refentrytitle>
170
<manvolnum>7</manvolnum></citerefentry>). (If the
171
<option>--connect</option> option is used, point-to-point
172
interfaces and non-broadcast interfaces are accepted.) If any
173
used interfaces are not up and running, they are first taken up
174
(and later taken down again on program exit).
177
Before network interfaces are selected, all <quote>network
178
hooks</quote> are run; see <xref linkend="network-hooks"/>.
130
to get a password. It uses IPv6 link-local addresses to get
131
network connectivity, Zeroconf to find the server, and TLS with
132
an OpenPGP key to ensure authenticity and confidentiality. It
133
keeps running, trying all servers on the network, until it
134
receives a satisfactory reply.
181
137
This program is not meant to be run directly; it is really meant
182
138
to run as a plugin of the <application>Mandos</application>
183
139
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
184
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
185
initial <acronym>RAM</acronym> disk environment because it is
186
specified as a <quote>keyscript</quote> in the <citerefentry>
187
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
188
</citerefentry> file.
140
<manvolnum>8mandos</manvolnum></citerefentry>, which in turn
141
runs as a <quote>keyscript</quote> specified in the
142
<citerefentry><refentrytitle>crypttab</refentrytitle>
143
<manvolnum>5</manvolnum></citerefentry> file.
228
202
assumed to separate the address from the port number.
231
Normally, Zeroconf would be used to locate Mandos servers,
232
in which case this option would only be used when testing
205
This option is normally only useful for debugging.
239
<term><option>--interface=<replaceable
240
>NAME</replaceable><arg rep='repeat'>,<replaceable
241
>NAME</replaceable></arg></option></term>
211
<term><option>--keydir=<replaceable
212
>DIRECTORY</replaceable></option></term>
214
<replaceable>DIRECTORY</replaceable></option></term>
217
Directory to read the OpenPGP key files
218
<filename>pubkey.txt</filename> and
219
<filename>seckey.txt</filename> from. The default is
220
<filename>/conf/conf.d/mandos</filename> (in the initial
221
<acronym>RAM</acronym> disk environment).
227
<term><option>--interface=
228
<replaceable>NAME</replaceable></option></term>
243
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
244
>NAME</replaceable></arg></option></term>
230
<replaceable>NAME</replaceable></option></term>
247
Comma separated list of network interfaces that will be
248
brought up and scanned for Mandos servers to connect to.
249
The default is the empty string, which will automatically
250
use all appropriate interfaces.
253
If the <option>--connect</option> option is used, and
254
exactly one interface name is specified (except
255
<quote><literal>none</literal></quote>), this specifies
256
the interface to use to connect to the address given.
259
Note that since this program will normally run in the
260
initial RAM disk environment, the interface must be an
261
interface which exists at that stage. Thus, the interface
262
can normally not be a pseudo-interface such as
263
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
264
will not exist until much later in the boot process, and
265
can not be used by this program, unless created by a
266
<quote>network hook</quote> — see <xref
267
linkend="network-hooks"/>.
270
<replaceable>NAME</replaceable> can be the string
271
<quote><literal>none</literal></quote>; this will make
272
<command>&COMMANDNAME;</command> only bring up interfaces
273
specified <emphasis>before</emphasis> this string. This
274
is not recommended, and only meant for advanced users.
233
Network interface that will be brought up and scanned for
234
Mandos servers to connect to. The default it
235
<quote><literal>eth0</literal></quote>.
308
271
<term><option>--priority=<replaceable
309
272
>STRING</replaceable></option></term>
311
<xi:include href="../mandos-options.xml"
312
xpointer="priority"/>
274
<xi:include href="mandos-options.xml" xpointer="priority"/>
317
279
<term><option>--dh-bits=<replaceable
318
280
>BITS</replaceable></option></term>
321
283
Sets the number of bits to use for the prime number in the
322
TLS Diffie-Hellman key exchange. The default value is
323
selected automatically based on the OpenPGP key. Note
324
that if the <option>--dh-params</option> option is used,
325
the values from that file will be used instead.
331
<term><option>--dh-params=<replaceable
332
>FILE</replaceable></option></term>
335
Specifies a PEM-encoded PKCS#3 file to read the parameters
336
needed by the TLS Diffie-Hellman key exchange from. If
337
this option is not given, or if the file for some reason
338
could not be used, the parameters will be generated on
339
startup, which will take some time and processing power.
340
Those using servers running under time, power or processor
341
constraints may want to generate such a file in advance
348
<term><option>--delay=<replaceable
349
>SECONDS</replaceable></option></term>
352
After bringing a network interface up, the program waits
353
for the interface to arrive in a <quote>running</quote>
354
state before proceeding. During this time, the kernel log
355
level will be lowered to reduce clutter on the system
356
console, alleviating any other plugins which might be
357
using the system console. This option sets the upper
358
limit of seconds to wait. The default is 2.5 seconds.
364
<term><option>--retry=<replaceable
365
>SECONDS</replaceable></option></term>
368
All Mandos servers are tried repeatedly until a password
369
is received. This value specifies, in seconds, how long
370
between each successive try <emphasis>for the same
371
server</emphasis>. The default is 10 seconds.
377
<term><option>--network-hook-dir=<replaceable
378
>DIR</replaceable></option></term>
381
Network hook directory. The default directory is
382
<quote><filename class="directory"
383
>/lib/mandos/network-hooks.d</filename></quote>.
284
TLS Diffie-Hellman key exchange. Default is 1024.
464
340
server could be found and the password received from it could be
465
341
successfully decrypted and output on standard output. The
466
342
program will exit with a non-zero exit status only if a critical
467
error occurs. Otherwise, it will forever connect to any
468
discovered <application>Mandos</application> servers, trying to
469
get a decryptable password and print it.
473
<refsect1 id="environment">
474
<title>ENVIRONMENT</title>
477
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
480
This environment variable will be assumed to contain the
481
directory containing any helper executables. The use and
482
nature of these helper executables, if any, is
483
purposefully not documented.
489
This program does not use any other environment variables, not
490
even the ones provided by <citerefentry><refentrytitle
491
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
496
<refsect1 id="network-hooks">
497
<title>NETWORK HOOKS</title>
499
If a network interface like a bridge or tunnel is required to
500
find a Mandos server, this requires the interface to be up and
501
running before <command>&COMMANDNAME;</command> starts looking
502
for Mandos servers. This can be accomplished by creating a
503
<quote>network hook</quote> program, and placing it in a special
507
Before the network is used (and again before program exit), any
508
runnable programs found in the network hook directory are run
509
with the argument <quote><literal>start</literal></quote> or
510
<quote><literal>stop</literal></quote>. This should bring up or
511
down, respectively, any network interface which
512
<command>&COMMANDNAME;</command> should use.
514
<refsect2 id="hook-requirements">
515
<title>REQUIREMENTS</title>
517
A network hook must be an executable file, and its name must
518
consist entirely of upper and lower case letters, digits,
519
underscores, periods, and hyphens.
522
A network hook will receive one argument, which can be one of
527
<term><literal>start</literal></term>
530
This should make the network hook create (if necessary)
531
and bring up a network interface.
536
<term><literal>stop</literal></term>
539
This should make the network hook take down a network
540
interface, and delete it if it did not exist previously.
545
<term><literal>files</literal></term>
548
This should make the network hook print, <emphasis>one
549
file per line</emphasis>, all the files needed for it to
550
run. (These files will be copied into the initial RAM
551
filesystem.) Typical use is for a network hook which is
552
a shell script to print its needed binaries.
555
It is not necessary to print any non-executable files
556
already in the network hook directory, these will be
557
copied implicitly if they otherwise satisfy the name
563
<term><literal>modules</literal></term>
566
This should make the network hook print, <emphasis>on
567
separate lines</emphasis>, all the kernel modules needed
568
for it to run. (These modules will be copied into the
569
initial RAM filesystem.) For instance, a tunnel
571
<quote><literal>tun</literal></quote> module.
577
The network hook will be provided with a number of environment
582
<term><envar>MANDOSNETHOOKDIR</envar></term>
585
The network hook directory, specified to
586
<command>&COMMANDNAME;</command> by the
587
<option>--network-hook-dir</option> option. Note: this
588
should <emphasis>always</emphasis> be used by the
589
network hook to refer to itself or any files in the hook
590
directory it may require.
595
<term><envar>DEVICE</envar></term>
598
The network interfaces, as specified to
599
<command>&COMMANDNAME;</command> by the
600
<option>--interface</option> option, combined to one
601
string and separated by commas. If this is set, and
602
does not contain the interface a hook will bring up,
603
there is no reason for a hook to continue.
608
<term><envar>MODE</envar></term>
611
This will be the same as the first argument;
612
i.e. <quote><literal>start</literal></quote>,
613
<quote><literal>stop</literal></quote>,
614
<quote><literal>files</literal></quote>, or
615
<quote><literal>modules</literal></quote>.
620
<term><envar>VERBOSITY</envar></term>
623
This will be the <quote><literal>1</literal></quote> if
624
the <option>--debug</option> option is passed to
625
<command>&COMMANDNAME;</command>, otherwise
626
<quote><literal>0</literal></quote>.
631
<term><envar>DELAY</envar></term>
634
This will be the same as the <option>--delay</option>
635
option passed to <command>&COMMANDNAME;</command>. Is
636
only set if <envar>MODE</envar> is
637
<quote><literal>start</literal></quote> or
638
<quote><literal>stop</literal></quote>.
643
<term><envar>CONNECT</envar></term>
646
This will be the same as the <option>--connect</option>
647
option passed to <command>&COMMANDNAME;</command>. Is
648
only set if <option>--connect</option> is passed and
649
<envar>MODE</envar> is
650
<quote><literal>start</literal></quote> or
651
<quote><literal>stop</literal></quote>.
657
A hook may not read from standard input, and should be
658
restrictive in printing to standard output or standard error
659
unless <varname>VERBOSITY</varname> is
660
<quote><literal>1</literal></quote>.
665
<refsect1 id="files">
669
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
671
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
675
OpenPGP public and private key files, in <quote>ASCII
676
Armor</quote> format. These are the default file names,
677
they can be changed with the <option>--pubkey</option> and
678
<option>--seckey</option> options.
684
class="directory">/lib/mandos/network-hooks.d</filename></term>
687
Directory where network hooks are located. Change this
688
with the <option>--network-hook-dir</option> option. See
689
<xref linkend="network-hooks"/>.
696
<!-- <refsect1 id="bugs"> -->
697
<!-- <title>BUGS</title> -->
343
error occurs. Otherwise, it will forever connect to new
344
<application>Mandosservers</application> servers as they appear,
345
trying to get a decryptable password.
349
<!-- <refsect1 id="environment"> -->
350
<!-- <title>ENVIRONMENT</title> -->
352
<!-- This program does not use any environment variables. -->
700
354
<!-- </refsect1> -->
702
368
<refsect1 id="example">
703
369
<title>EXAMPLE</title>
705
Note that normally, command line options will not be given
706
directly, but via options for the Mandos <citerefentry
707
><refentrytitle>plugin-runner</refentrytitle>
708
<manvolnum>8mandos</manvolnum></citerefentry>.
712
Normal invocation needs no options, if the network interfaces
713
can be automatically determined:
716
<userinput>&COMMANDNAME;</userinput>
721
Search for Mandos servers (and connect to them) using one
725
<!-- do not wrap this line -->
726
<userinput>&COMMANDNAME; --interface eth1</userinput>
731
Run in debug mode, and use a custom key:
735
<!-- do not wrap this line -->
736
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
742
Run in debug mode, with a custom key, and do not use Zeroconf
743
to locate a server; connect directly to the IPv6 link-local
744
address <quote><systemitem class="ipaddress"
745
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
746
using interface eth2:
750
<!-- do not wrap this line -->
751
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
757
374
<refsect1 id="security">
758
375
<title>SECURITY</title>
760
This program is set-uid to root, but will switch back to the
761
original (and presumably non-privileged) user and group after
762
bringing up the network interface.
765
To use this program for its intended purpose (see <xref
766
linkend="purpose"/>), the password for the root file system will
767
have to be given out to be stored in a server computer, after
768
having been encrypted using an OpenPGP key. This encrypted data
769
which will be stored in a server can only be decrypted by the
770
OpenPGP key, and the data will only be given out to those
771
clients who can prove they actually have that key. This key,
772
however, is stored unencrypted on the client side in its initial
773
<acronym>RAM</acronym> disk image file system. This is normally
774
readable by all, but this is normally fixed during installation
775
of this program; file permissions are set so that no-one is able
779
The only remaining weak point is that someone with physical
780
access to the client hard drive might turn off the client
781
computer, read the OpenPGP keys directly from the hard drive,
782
and communicate with the server. To safeguard against this, the
783
server is supposed to notice the client disappearing and stop
784
giving out the encrypted data. Therefore, it is important to
785
set the timeout and checker interval values tightly on the
786
server. See <citerefentry><refentrytitle
787
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
790
It will also help if the checker program on the server is
791
configured to request something from the client which can not be
792
spoofed by someone else on the network, like SSH server key
793
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
794
echo (<quote>ping</quote>) replies.
797
<emphasis>Note</emphasis>: This makes it completely insecure to
798
have <application >Mandos</application> clients which dual-boot
799
to another operating system which is <emphasis>not</emphasis>
800
trusted to keep the initial <acronym>RAM</acronym> disk image
805
380
<refsect1 id="see_also">
806
381
<title>SEE ALSO</title>
808
<citerefentry><refentrytitle>intro</refentrytitle>
809
<manvolnum>8mandos</manvolnum></citerefentry>,
810
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
811
<manvolnum>8</manvolnum></citerefentry>,
812
<citerefentry><refentrytitle>crypttab</refentrytitle>
813
<manvolnum>5</manvolnum></citerefentry>,
814
383
<citerefentry><refentrytitle>mandos</refentrytitle>
815
384
<manvolnum>8</manvolnum></citerefentry>,
816
385
<citerefentry><refentrytitle>password-prompt</refentrytitle>
818
387
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
819
388
<manvolnum>8mandos</manvolnum></citerefentry>
824
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
828
Zeroconf is the network protocol standard used for finding
829
Mandos servers on the local network.
835
<ulink url="http://www.avahi.org/">Avahi</ulink>
839
Avahi is the library this program calls to find Zeroconf
846
<ulink url="http://www.gnu.org/software/gnutls/"
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="http://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 4346: <citetitle>The Transport Layer Security (TLS)
904
Protocol Version 1.1</citetitle>
908
TLS 1.1 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 5081: <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.
392
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
396
<ulink url="http://www.avahi.org/">Avahi</ulink>
401
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
406
url="http://www.gnupg.org/related_software/gpgme/">
411
<citation>RFC 4880: <citetitle>OpenPGP Message
412
Format</citetitle></citation>
416
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
417
Transport Layer Security</citetitle></citation>
421
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
422
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
423
Unicast Addresses</citation>
939
429
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