145
122
</refsynopsisdiv>
147
124
<refsect1 id="description">
148
125
<title>DESCRIPTION</title>
150
127
<command>&COMMANDNAME;</command> is a client program that
151
128
communicates with <citerefentry><refentrytitle
152
129
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
153
to get a password. In slightly more detail, this client program
154
brings up network interfaces, uses the interfaces’ IPv6
155
link-local addresses to get network connectivity, uses Zeroconf
156
to find servers on the local network, and communicates with
157
servers using TLS with an OpenPGP key to ensure authenticity and
158
confidentiality. This client program keeps running, trying all
159
servers on the network, until it receives a satisfactory reply
160
or a TERM signal. After all servers have been tried, all
161
servers are periodically retried. If no servers are found it
162
will wait indefinitely for new servers to appear.
165
The network interfaces are selected like this: If any interfaces
166
are specified using the <option>--interface</option> option,
167
those interface are used. Otherwise,
168
<command>&COMMANDNAME;</command> will use all interfaces that
169
are not loopback interfaces, are not point-to-point interfaces,
170
are capable of broadcasting and do not have the NOARP flag (see
171
<citerefentry><refentrytitle>netdevice</refentrytitle>
172
<manvolnum>7</manvolnum></citerefentry>). (If the
173
<option>--connect</option> option is used, point-to-point
174
interfaces and non-broadcast interfaces are accepted.) If any
175
used interfaces are not up and running, they are first taken up
176
(and later taken down again on program exit).
179
Before network interfaces are selected, all <quote>network
180
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.
183
137
This program is not meant to be run directly; it is really meant
230
184
assumed to separate the address from the port number.
233
Normally, Zeroconf would be used to locate Mandos servers,
234
in which case this option would only be used when testing
187
This option is normally only useful for testing and
241
<term><option>--interface=<replaceable
242
>NAME</replaceable><arg rep='repeat'>,<replaceable
243
>NAME</replaceable></arg></option></term>
194
<term><option>--keydir=<replaceable
195
>DIRECTORY</replaceable></option></term>
197
<replaceable>DIRECTORY</replaceable></option></term>
200
Directory to read the OpenPGP key files
201
<filename>pubkey.txt</filename> and
202
<filename>seckey.txt</filename> from. The default is
203
<filename>/conf/conf.d/mandos</filename> (in the initial
204
<acronym>RAM</acronym> disk environment).
210
<term><option>--interface=
211
<replaceable>NAME</replaceable></option></term>
245
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
246
>NAME</replaceable></arg></option></term>
213
<replaceable>NAME</replaceable></option></term>
249
Comma separated list of network interfaces that will be
250
brought up and scanned for Mandos servers to connect to.
251
The default is the empty string, which will automatically
252
use all appropriate interfaces.
255
If the <option>--connect</option> option is used, and
256
exactly one interface name is specified (except
257
<quote><literal>none</literal></quote>), this specifies
258
the interface to use to connect to the address given.
261
Note that since this program will normally run in the
262
initial RAM disk environment, the interface must be an
263
interface which exists at that stage. Thus, the interface
264
can normally not be a pseudo-interface such as
265
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
266
will not exist until much later in the boot process, and
267
can not be used by this program, unless created by a
268
<quote>network hook</quote> — see <xref
269
linkend="network-hooks"/>.
272
<replaceable>NAME</replaceable> can be the string
273
<quote><literal>none</literal></quote>; this will make
274
<command>&COMMANDNAME;</command> only bring up interfaces
275
specified <emphasis>before</emphasis> this string. This
276
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>.
314
258
xpointer="priority"/>
319
263
<term><option>--dh-bits=<replaceable
320
264
>BITS</replaceable></option></term>
323
267
Sets the number of bits to use for the prime number in the
324
TLS Diffie-Hellman key exchange. The default value is
325
selected automatically based on the OpenPGP key. Note
326
that if the <option>--dh-params</option> option is used,
327
the values from that file will be used instead.
333
<term><option>--dh-params=<replaceable
334
>FILE</replaceable></option></term>
337
Specifies a PEM-encoded PKCS#3 file to read the parameters
338
needed by the TLS Diffie-Hellman key exchange from. If
339
this option is not given, or if the file for some reason
340
could not be used, the parameters will be generated on
341
startup, which will take some time and processing power.
342
Those using servers running under time, power or processor
343
constraints may want to generate such a file in advance
350
<term><option>--delay=<replaceable
351
>SECONDS</replaceable></option></term>
354
After bringing a network interface up, the program waits
355
for the interface to arrive in a <quote>running</quote>
356
state before proceeding. During this time, the kernel log
357
level will be lowered to reduce clutter on the system
358
console, alleviating any other plugins which might be
359
using the system console. This option sets the upper
360
limit of seconds to wait. The default is 2.5 seconds.
366
<term><option>--retry=<replaceable
367
>SECONDS</replaceable></option></term>
370
All Mandos servers are tried repeatedly until a password
371
is received. This value specifies, in seconds, how long
372
between each successive try <emphasis>for the same
373
server</emphasis>. The default is 10 seconds.
379
<term><option>--network-hook-dir=<replaceable
380
>DIR</replaceable></option></term>
383
Network hook directory. The default directory is
384
<quote><filename class="directory"
385
>/lib/mandos/network-hooks.d</filename></quote>.
268
TLS Diffie-Hellman key exchange. Default is 1024.
466
343
server could be found and the password received from it could be
467
344
successfully decrypted and output on standard output. The
468
345
program will exit with a non-zero exit status only if a critical
469
error occurs. Otherwise, it will forever connect to any
470
discovered <application>Mandos</application> servers, trying to
471
get a decryptable password and print it.
346
error occurs. Otherwise, it will forever connect to new
347
<application>Mandos</application> servers as they appear, trying
348
to get a decryptable password.
475
352
<refsect1 id="environment">
476
353
<title>ENVIRONMENT</title>
479
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
482
This environment variable will be assumed to contain the
483
directory containing any helper executables. The use and
484
nature of these helper executables, if any, is
485
purposefully not documented.
491
This program does not use any other environment variables, not
492
even the ones provided by <citerefentry><refentrytitle
355
This program does not use any environment variables, not even
356
the ones provided by <citerefentry><refentrytitle
493
357
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
498
<refsect1 id="network-hooks">
499
<title>NETWORK HOOKS</title>
501
If a network interface like a bridge or tunnel is required to
502
find a Mandos server, this requires the interface to be up and
503
running before <command>&COMMANDNAME;</command> starts looking
504
for Mandos servers. This can be accomplished by creating a
505
<quote>network hook</quote> program, and placing it in a special
509
Before the network is used (and again before program exit), any
510
runnable programs found in the network hook directory are run
511
with the argument <quote><literal>start</literal></quote> or
512
<quote><literal>stop</literal></quote>. This should bring up or
513
down, respectively, any network interface which
514
<command>&COMMANDNAME;</command> should use.
516
<refsect2 id="hook-requirements">
517
<title>REQUIREMENTS</title>
519
A network hook must be an executable file, and its name must
520
consist entirely of upper and lower case letters, digits,
521
underscores, periods, and hyphens.
524
A network hook will receive one argument, which can be one of
529
<term><literal>start</literal></term>
532
This should make the network hook create (if necessary)
533
and bring up a network interface.
538
<term><literal>stop</literal></term>
541
This should make the network hook take down a network
542
interface, and delete it if it did not exist previously.
547
<term><literal>files</literal></term>
550
This should make the network hook print, <emphasis>one
551
file per line</emphasis>, all the files needed for it to
552
run. (These files will be copied into the initial RAM
553
filesystem.) Typical use is for a network hook which is
554
a shell script to print its needed binaries.
557
It is not necessary to print any non-executable files
558
already in the network hook directory, these will be
559
copied implicitly if they otherwise satisfy the name
565
<term><literal>modules</literal></term>
568
This should make the network hook print, <emphasis>on
569
separate lines</emphasis>, all the kernel modules needed
570
for it to run. (These modules will be copied into the
571
initial RAM filesystem.) For instance, a tunnel
573
<quote><literal>tun</literal></quote> module.
579
The network hook will be provided with a number of environment
584
<term><envar>MANDOSNETHOOKDIR</envar></term>
587
The network hook directory, specified to
588
<command>&COMMANDNAME;</command> by the
589
<option>--network-hook-dir</option> option. Note: this
590
should <emphasis>always</emphasis> be used by the
591
network hook to refer to itself or any files in the hook
592
directory it may require.
597
<term><envar>DEVICE</envar></term>
600
The network interfaces, as specified to
601
<command>&COMMANDNAME;</command> by the
602
<option>--interface</option> option, combined to one
603
string and separated by commas. If this is set, and
604
does not contain the interface a hook will bring up,
605
there is no reason for a hook to continue.
610
<term><envar>MODE</envar></term>
613
This will be the same as the first argument;
614
i.e. <quote><literal>start</literal></quote>,
615
<quote><literal>stop</literal></quote>,
616
<quote><literal>files</literal></quote>, or
617
<quote><literal>modules</literal></quote>.
622
<term><envar>VERBOSITY</envar></term>
625
This will be the <quote><literal>1</literal></quote> if
626
the <option>--debug</option> option is passed to
627
<command>&COMMANDNAME;</command>, otherwise
628
<quote><literal>0</literal></quote>.
633
<term><envar>DELAY</envar></term>
636
This will be the same as the <option>--delay</option>
637
option passed to <command>&COMMANDNAME;</command>. Is
638
only set if <envar>MODE</envar> is
639
<quote><literal>start</literal></quote> or
640
<quote><literal>stop</literal></quote>.
645
<term><envar>CONNECT</envar></term>
648
This will be the same as the <option>--connect</option>
649
option passed to <command>&COMMANDNAME;</command>. Is
650
only set if <option>--connect</option> is passed and
651
<envar>MODE</envar> is
652
<quote><literal>start</literal></quote> or
653
<quote><literal>stop</literal></quote>.
659
A hook may not read from standard input, and should be
660
restrictive in printing to standard output or standard error
661
unless <varname>VERBOSITY</varname> is
662
<quote><literal>1</literal></quote>.
667
<refsect1 id="files">
668
363
<title>FILES</title>
671
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
673
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
677
OpenPGP public and private key files, in <quote>ASCII
678
Armor</quote> format. These are the default file names,
679
they can be changed with the <option>--pubkey</option> and
680
<option>--seckey</option> options.
686
class="directory">/lib/mandos/network-hooks.d</filename></term>
689
Directory where network hooks are located. Change this
690
with the <option>--network-hook-dir</option> option. See
691
<xref linkend="network-hooks"/>.
698
368
<refsect1 id="bugs">
699
369
<title>BUGS</title>
700
<xi:include href="../bugs.xml"/>
703
374
<refsect1 id="example">
704
375
<title>EXAMPLE</title>
706
Note that normally, command line options will not be given
707
directly, but via options for the Mandos <citerefentry
708
><refentrytitle>plugin-runner</refentrytitle>
709
<manvolnum>8mandos</manvolnum></citerefentry>.
713
Normal invocation needs no options, if the network interfaces
714
can be automatically determined:
717
<userinput>&COMMANDNAME;</userinput>
722
Search for Mandos servers (and connect to them) using one
726
<!-- do not wrap this line -->
727
<userinput>&COMMANDNAME; --interface eth1</userinput>
732
Run in debug mode, and use a custom key:
736
<!-- do not wrap this line -->
737
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
743
Run in debug mode, with a custom key, and do not use Zeroconf
744
to locate a server; connect directly to the IPv6 link-local
745
address <quote><systemitem class="ipaddress"
746
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
747
using interface eth2:
751
<!-- do not wrap this line -->
752
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
758
380
<refsect1 id="security">
759
381
<title>SECURITY</title>
761
This program is set-uid to root, but will switch back to the
762
original (and presumably non-privileged) user and group after
763
bringing up the network interface.
766
To use this program for its intended purpose (see <xref
767
linkend="purpose"/>), the password for the root file system will
768
have to be given out to be stored in a server computer, after
769
having been encrypted using an OpenPGP key. This encrypted data
770
which will be stored in a server can only be decrypted by the
771
OpenPGP key, and the data will only be given out to those
772
clients who can prove they actually have that key. This key,
773
however, is stored unencrypted on the client side in its initial
774
<acronym>RAM</acronym> disk image file system. This is normally
775
readable by all, but this is normally fixed during installation
776
of this program; file permissions are set so that no-one is able
780
The only remaining weak point is that someone with physical
781
access to the client hard drive might turn off the client
782
computer, read the OpenPGP keys directly from the hard drive,
783
and communicate with the server. To safeguard against this, the
784
server is supposed to notice the client disappearing and stop
785
giving out the encrypted data. Therefore, it is important to
786
set the timeout and checker interval values tightly on the
787
server. See <citerefentry><refentrytitle
788
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
791
It will also help if the checker program on the server is
792
configured to request something from the client which can not be
793
spoofed by someone else on the network, like SSH server key
794
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
795
echo (<quote>ping</quote>) replies.
798
<emphasis>Note</emphasis>: This makes it completely insecure to
799
have <application >Mandos</application> clients which dual-boot
800
to another operating system which is <emphasis>not</emphasis>
801
trusted to keep the initial <acronym>RAM</acronym> disk image
806
386
<refsect1 id="see_also">
807
387
<title>SEE ALSO</title>
809
<citerefentry><refentrytitle>intro</refentrytitle>
810
<manvolnum>8mandos</manvolnum></citerefentry>,
811
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
812
<manvolnum>8</manvolnum></citerefentry>,
813
<citerefentry><refentrytitle>crypttab</refentrytitle>
814
<manvolnum>5</manvolnum></citerefentry>,
815
389
<citerefentry><refentrytitle>mandos</refentrytitle>
816
390
<manvolnum>8</manvolnum></citerefentry>,
817
391
<citerefentry><refentrytitle>password-prompt</refentrytitle>
819
393
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
820
394
<manvolnum>8mandos</manvolnum></citerefentry>
825
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
829
Zeroconf is the network protocol standard used for finding
830
Mandos servers on the local network.
836
<ulink url="http://www.avahi.org/">Avahi</ulink>
840
Avahi is the library this program calls to find Zeroconf
847
<ulink url="https://www.gnutls.org/">GnuTLS</ulink>
851
GnuTLS is the library this client uses to implement TLS for
852
communicating securely with the server, and at the same time
853
send the public OpenPGP key to the server.
859
<ulink url="https://www.gnupg.org/related_software/gpgme/"
864
GPGME is the library used to decrypt the OpenPGP data sent
871
RFC 4291: <citetitle>IP Version 6 Addressing
872
Architecture</citetitle>
877
<term>Section 2.2: <citetitle>Text Representation of
878
Addresses</citetitle></term>
879
<listitem><para/></listitem>
882
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
883
Address</citetitle></term>
884
<listitem><para/></listitem>
887
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
888
Addresses</citetitle></term>
891
This client uses IPv6 link-local addresses, which are
892
immediately usable since a link-local addresses is
893
automatically assigned to a network interface when it
903
RFC 5246: <citetitle>The Transport Layer Security (TLS)
904
Protocol Version 1.2</citetitle>
908
TLS 1.2 is the protocol implemented by GnuTLS.
914
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
918
The data received from the server is binary encrypted
925
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
930
This is implemented by GnuTLS and used by this program so
931
that OpenPGP keys can be used.
398
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
402
<ulink url="http://www.avahi.org/">Avahi</ulink>
407
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
412
url="http://www.gnupg.org/related_software/gpgme/"
417
<citation>RFC 4880: <citetitle>OpenPGP Message
418
Format</citetitle></citation>
422
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
423
Transport Layer Security</citetitle></citation>
427
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
428
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
429
Unicast Addresses</citation>
939
435
<!-- Local Variables: -->
940
436
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
941
437
<!-- time-stamp-end: "[\"']>" -->