122
144
</refsynopsisdiv>
124
146
<refsect1 id="description">
125
147
<title>DESCRIPTION</title>
127
149
<command>&COMMANDNAME;</command> is a client program that
128
150
communicates with <citerefentry><refentrytitle
129
151
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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.
152
to get a password. In slightly more detail, this client program
153
brings up network interfaces, uses the interfaces’ IPv6
154
link-local addresses to get network connectivity, uses Zeroconf
155
to find servers on the local network, and communicates with
156
servers using TLS with an OpenPGP key to ensure authenticity and
157
confidentiality. This client program keeps running, trying all
158
servers on the network, until it receives a satisfactory reply
159
or a TERM signal. After all servers have been tried, all
160
servers are periodically retried. If no servers are found it
161
will wait indefinitely for new servers to appear.
164
The network interfaces are selected like this: If any interfaces
165
are specified using the <option>--interface</option> option,
166
those interface are used. Otherwise,
167
<command>&COMMANDNAME;</command> will use all interfaces that
168
are not loopback interfaces, are not point-to-point interfaces,
169
are capable of broadcasting and do not have the NOARP flag (see
170
<citerefentry><refentrytitle>netdevice</refentrytitle>
171
<manvolnum>7</manvolnum></citerefentry>). (If the
172
<option>--connect</option> option is used, point-to-point
173
interfaces and non-broadcast interfaces are accepted.) If any
174
used interfaces are not up and running, they are first taken up
175
(and later taken down again on program exit).
178
Before network interfaces are selected, all <quote>network
179
hooks</quote> are run; see <xref linkend="network-hooks"/>.
137
182
This program is not meant to be run directly; it is really meant
138
183
to run as a plugin of the <application>Mandos</application>
139
184
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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.
185
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
186
initial <acronym>RAM</acronym> disk environment because it is
187
specified as a <quote>keyscript</quote> in the <citerefentry>
188
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
189
</citerefentry> file.
202
229
assumed to separate the address from the port number.
205
This option is normally only useful for debugging.
232
Normally, Zeroconf would be used to locate Mandos servers,
233
in which case this option would only be used when testing
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>
240
<term><option>--interface=<replaceable
241
>NAME</replaceable><arg rep='repeat'>,<replaceable
242
>NAME</replaceable></arg></option></term>
230
<replaceable>NAME</replaceable></option></term>
244
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
245
>NAME</replaceable></arg></option></term>
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>.
248
Comma separated list of network interfaces that will be
249
brought up and scanned for Mandos servers to connect to.
250
The default is the empty string, which will automatically
251
use all appropriate interfaces.
254
If the <option>--connect</option> option is used, and
255
exactly one interface name is specified (except
256
<quote><literal>none</literal></quote>), this specifies
257
the interface to use to connect to the address given.
260
Note that since this program will normally run in the
261
initial RAM disk environment, the interface must be an
262
interface which exists at that stage. Thus, the interface
263
can normally not be a pseudo-interface such as
264
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
265
will not exist until much later in the boot process, and
266
can not be used by this program, unless created by a
267
<quote>network hook</quote> — see <xref
268
linkend="network-hooks"/>.
271
<replaceable>NAME</replaceable> can be the string
272
<quote><literal>none</literal></quote>; this will make
273
<command>&COMMANDNAME;</command> only bring up interfaces
274
specified <emphasis>before</emphasis> this string. This
275
is not recommended, and only meant for advanced users.
271
309
<term><option>--priority=<replaceable
272
310
>STRING</replaceable></option></term>
274
<xi:include href="mandos-options.xml" xpointer="priority"/>
312
<xi:include href="../mandos-options.xml"
313
xpointer="priority"/>
279
318
<term><option>--dh-bits=<replaceable
280
319
>BITS</replaceable></option></term>
283
322
Sets the number of bits to use for the prime number in the
284
TLS Diffie-Hellman key exchange. Default is 1024.
323
TLS Diffie-Hellman key exchange. The default value is
324
selected automatically based on the OpenPGP key. Note
325
that if the <option>--dh-params</option> option is used,
326
the values from that file will be used instead.
332
<term><option>--dh-params=<replaceable
333
>FILE</replaceable></option></term>
336
Specifies a PEM-encoded PKCS#3 file to read the parameters
337
needed by the TLS Diffie-Hellman key exchange from. If
338
this option is not given, or if the file for some reason
339
could not be used, the parameters will be generated on
340
startup, which will take some time and processing power.
341
Those using servers running under time, power or processor
342
constraints may want to generate such a file in advance
349
<term><option>--delay=<replaceable
350
>SECONDS</replaceable></option></term>
353
After bringing a network interface up, the program waits
354
for the interface to arrive in a <quote>running</quote>
355
state before proceeding. During this time, the kernel log
356
level will be lowered to reduce clutter on the system
357
console, alleviating any other plugins which might be
358
using the system console. This option sets the upper
359
limit of seconds to wait. The default is 2.5 seconds.
365
<term><option>--retry=<replaceable
366
>SECONDS</replaceable></option></term>
369
All Mandos servers are tried repeatedly until a password
370
is received. This value specifies, in seconds, how long
371
between each successive try <emphasis>for the same
372
server</emphasis>. The default is 10 seconds.
378
<term><option>--network-hook-dir=<replaceable
379
>DIR</replaceable></option></term>
382
Network hook directory. The default directory is
383
<quote><filename class="directory"
384
>/lib/mandos/network-hooks.d</filename></quote>.
340
465
server could be found and the password received from it could be
341
466
successfully decrypted and output on standard output. The
342
467
program will exit with a non-zero exit status only if a critical
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. -->
468
error occurs. Otherwise, it will forever connect to any
469
discovered <application>Mandos</application> servers, trying to
470
get a decryptable password and print it.
474
<refsect1 id="environment">
475
<title>ENVIRONMENT</title>
478
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
481
This environment variable will be assumed to contain the
482
directory containing any helper executables. The use and
483
nature of these helper executables, if any, is
484
purposefully not documented.
490
This program does not use any other environment variables, not
491
even the ones provided by <citerefentry><refentrytitle
492
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
497
<refsect1 id="network-hooks">
498
<title>NETWORK HOOKS</title>
500
If a network interface like a bridge or tunnel is required to
501
find a Mandos server, this requires the interface to be up and
502
running before <command>&COMMANDNAME;</command> starts looking
503
for Mandos servers. This can be accomplished by creating a
504
<quote>network hook</quote> program, and placing it in a special
508
Before the network is used (and again before program exit), any
509
runnable programs found in the network hook directory are run
510
with the argument <quote><literal>start</literal></quote> or
511
<quote><literal>stop</literal></quote>. This should bring up or
512
down, respectively, any network interface which
513
<command>&COMMANDNAME;</command> should use.
515
<refsect2 id="hook-requirements">
516
<title>REQUIREMENTS</title>
518
A network hook must be an executable file, and its name must
519
consist entirely of upper and lower case letters, digits,
520
underscores, periods, and hyphens.
523
A network hook will receive one argument, which can be one of
528
<term><literal>start</literal></term>
531
This should make the network hook create (if necessary)
532
and bring up a network interface.
537
<term><literal>stop</literal></term>
540
This should make the network hook take down a network
541
interface, and delete it if it did not exist previously.
546
<term><literal>files</literal></term>
549
This should make the network hook print, <emphasis>one
550
file per line</emphasis>, all the files needed for it to
551
run. (These files will be copied into the initial RAM
552
filesystem.) Typical use is for a network hook which is
553
a shell script to print its needed binaries.
556
It is not necessary to print any non-executable files
557
already in the network hook directory, these will be
558
copied implicitly if they otherwise satisfy the name
564
<term><literal>modules</literal></term>
567
This should make the network hook print, <emphasis>on
568
separate lines</emphasis>, all the kernel modules needed
569
for it to run. (These modules will be copied into the
570
initial RAM filesystem.) For instance, a tunnel
572
<quote><literal>tun</literal></quote> module.
578
The network hook will be provided with a number of environment
583
<term><envar>MANDOSNETHOOKDIR</envar></term>
586
The network hook directory, specified to
587
<command>&COMMANDNAME;</command> by the
588
<option>--network-hook-dir</option> option. Note: this
589
should <emphasis>always</emphasis> be used by the
590
network hook to refer to itself or any files in the hook
591
directory it may require.
596
<term><envar>DEVICE</envar></term>
599
The network interfaces, as specified to
600
<command>&COMMANDNAME;</command> by the
601
<option>--interface</option> option, combined to one
602
string and separated by commas. If this is set, and
603
does not contain the interface a hook will bring up,
604
there is no reason for a hook to continue.
609
<term><envar>MODE</envar></term>
612
This will be the same as the first argument;
613
i.e. <quote><literal>start</literal></quote>,
614
<quote><literal>stop</literal></quote>,
615
<quote><literal>files</literal></quote>, or
616
<quote><literal>modules</literal></quote>.
621
<term><envar>VERBOSITY</envar></term>
624
This will be the <quote><literal>1</literal></quote> if
625
the <option>--debug</option> option is passed to
626
<command>&COMMANDNAME;</command>, otherwise
627
<quote><literal>0</literal></quote>.
632
<term><envar>DELAY</envar></term>
635
This will be the same as the <option>--delay</option>
636
option passed to <command>&COMMANDNAME;</command>. Is
637
only set if <envar>MODE</envar> is
638
<quote><literal>start</literal></quote> or
639
<quote><literal>stop</literal></quote>.
644
<term><envar>CONNECT</envar></term>
647
This will be the same as the <option>--connect</option>
648
option passed to <command>&COMMANDNAME;</command>. Is
649
only set if <option>--connect</option> is passed and
650
<envar>MODE</envar> is
651
<quote><literal>start</literal></quote> or
652
<quote><literal>stop</literal></quote>.
658
A hook may not read from standard input, and should be
659
restrictive in printing to standard output or standard error
660
unless <varname>VERBOSITY</varname> is
661
<quote><literal>1</literal></quote>.
666
<refsect1 id="files">
357
667
<title>FILES</title>
670
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
672
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
676
OpenPGP public and private key files, in <quote>ASCII
677
Armor</quote> format. These are the default file names,
678
they can be changed with the <option>--pubkey</option> and
679
<option>--seckey</option> options.
685
class="directory">/lib/mandos/network-hooks.d</filename></term>
688
Directory where network hooks are located. Change this
689
with the <option>--network-hook-dir</option> option. See
690
<xref linkend="network-hooks"/>.
362
697
<refsect1 id="bugs">
363
698
<title>BUGS</title>
699
<xi:include href="../bugs.xml"/>
368
702
<refsect1 id="example">
369
703
<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>
374
757
<refsect1 id="security">
375
758
<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
380
805
<refsect1 id="see_also">
381
806
<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>,
383
814
<citerefentry><refentrytitle>mandos</refentrytitle>
384
815
<manvolnum>8</manvolnum></citerefentry>,
385
816
<citerefentry><refentrytitle>password-prompt</refentrytitle>
387
818
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
388
819
<manvolnum>8mandos</manvolnum></citerefentry>
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>
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="https://www.gnutls.org/">GnuTLS</ulink>
850
GnuTLS is the library this client uses to implement TLS for
851
communicating securely with the server, and at the same time
852
send the public OpenPGP key to the server.
858
<ulink url="https://www.gnupg.org/related_software/gpgme/"
863
GPGME is the library used to decrypt the OpenPGP data sent
870
RFC 4291: <citetitle>IP Version 6 Addressing
871
Architecture</citetitle>
876
<term>Section 2.2: <citetitle>Text Representation of
877
Addresses</citetitle></term>
878
<listitem><para/></listitem>
881
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
882
Address</citetitle></term>
883
<listitem><para/></listitem>
886
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
887
Addresses</citetitle></term>
890
This client uses IPv6 link-local addresses, which are
891
immediately usable since a link-local addresses is
892
automatically assigned to a network interface when it
902
RFC 5246: <citetitle>The Transport Layer Security (TLS)
903
Protocol Version 1.2</citetitle>
907
TLS 1.2 is the protocol implemented by GnuTLS.
913
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
917
The data received from the server is binary encrypted
924
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
929
This is implemented by GnuTLS and used by this program so
930
that OpenPGP keys can be used.
429
938
<!-- Local Variables: -->
430
939
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
431
940
<!-- time-stamp-end: "[\"']>" -->