122
142
</refsynopsisdiv>
124
144
<refsect1 id="description">
125
145
<title>DESCRIPTION</title>
127
147
<command>&COMMANDNAME;</command> is a client program that
128
148
communicates with <citerefentry><refentrytitle
129
149
>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.
150
to get a password. In slightly more detail, this client program
151
brings up network interfaces, uses the interfaces’ IPv6
152
link-local addresses to get network connectivity, uses Zeroconf
153
to find servers on the local network, and communicates with
154
servers using TLS with an OpenPGP key to ensure authenticity and
155
confidentiality. This client program keeps running, trying all
156
servers on the network, until it receives a satisfactory reply
157
or a TERM signal. After all servers have been tried, all
158
servers are periodically retried. If no servers are found it
159
will wait indefinitely for new servers to appear.
162
The network interfaces are selected like this: If any interfaces
163
are specified using the <option>--interface</option> option,
164
those interface are used. Otherwise,
165
<command>&COMMANDNAME;</command> will use all interfaces that
166
are not loopback interfaces, are not point-to-point interfaces,
167
are capable of broadcasting and do not have the NOARP flag (see
168
<citerefentry><refentrytitle>netdevice</refentrytitle>
169
<manvolnum>7</manvolnum></citerefentry>). (If the
170
<option>--connect</option> option is used, point-to-point
171
interfaces and non-broadcast interfaces are accepted.) If any
172
used interfaces are not up and running, they are first taken up
173
(and later taken down again on program exit).
176
Before network interfaces are selected, all <quote>network
177
hooks</quote> are run; see <xref linkend="network-hooks"/>.
137
180
This program is not meant to be run directly; it is really meant
184
227
assumed to separate the address from the port number.
187
This option is normally only useful for testing and
230
Normally, Zeroconf would be used to locate Mandos servers,
231
in which case this option would only be used when testing
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>
238
<term><option>--interface=<replaceable
239
>NAME</replaceable><arg rep='repeat'>,<replaceable
240
>NAME</replaceable></arg></option></term>
213
<replaceable>NAME</replaceable></option></term>
242
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
243
>NAME</replaceable></arg></option></term>
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>.
246
Comma separated list of network interfaces that will be
247
brought up and scanned for Mandos servers to connect to.
248
The default is the empty string, which will automatically
249
use all appropriate interfaces.
252
If the <option>--connect</option> option is used, and
253
exactly one interface name is specified (except
254
<quote><literal>none</literal></quote>), this specifies
255
the interface to use to connect to the address given.
258
Note that since this program will normally run in the
259
initial RAM disk environment, the interface must be an
260
interface which exists at that stage. Thus, the interface
261
can normally not be a pseudo-interface such as
262
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
263
will not exist until much later in the boot process, and
264
can not be used by this program, unless created by a
265
<quote>network hook</quote> — see <xref
266
linkend="network-hooks"/>.
269
<replaceable>NAME</replaceable> can be the string
270
<quote><literal>none</literal></quote>; this will make
271
<command>&COMMANDNAME;</command> only bring up interfaces
272
specified <emphasis>before</emphasis> this string. This
273
is not recommended, and only meant for advanced users.
258
311
xpointer="priority"/>
263
316
<term><option>--dh-bits=<replaceable
264
317
>BITS</replaceable></option></term>
267
320
Sets the number of bits to use for the prime number in the
268
TLS Diffie-Hellman key exchange. Default is 1024.
321
TLS Diffie-Hellman key exchange. The default value is
322
selected automatically based on the OpenPGP key. Note
323
that if the <option>--dh-params</option> option is used,
324
the values from that file will be used instead.
330
<term><option>--dh-params=<replaceable
331
>FILE</replaceable></option></term>
334
Specifies a PEM-encoded PKCS#3 file to read the parameters
335
needed by the TLS Diffie-Hellman key exchange from. If
336
this option is not given, or if the file for some reason
337
could not be used, the parameters will be generated on
338
startup, which will take some time and processing power.
339
Those using servers running under time, power or processor
340
constraints may want to generate such a file in advance
347
<term><option>--delay=<replaceable
348
>SECONDS</replaceable></option></term>
351
After bringing a network interface up, the program waits
352
for the interface to arrive in a <quote>running</quote>
353
state before proceeding. During this time, the kernel log
354
level will be lowered to reduce clutter on the system
355
console, alleviating any other plugins which might be
356
using the system console. This option sets the upper
357
limit of seconds to wait. The default is 2.5 seconds.
363
<term><option>--retry=<replaceable
364
>SECONDS</replaceable></option></term>
367
All Mandos servers are tried repeatedly until a password
368
is received. This value specifies, in seconds, how long
369
between each successive try <emphasis>for the same
370
server</emphasis>. The default is 10 seconds.
376
<term><option>--network-hook-dir=<replaceable
377
>DIR</replaceable></option></term>
380
Network hook directory. The default directory is
381
<quote><filename class="directory"
382
>/lib/mandos/network-hooks.d</filename></quote>.
343
463
server could be found and the password received from it could be
344
464
successfully decrypted and output on standard output. The
345
465
program will exit with a non-zero exit status only if a critical
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.
466
error occurs. Otherwise, it will forever connect to any
467
discovered <application>Mandos</application> servers, trying to
468
get a decryptable password and print it.
352
472
<refsect1 id="environment">
353
473
<title>ENVIRONMENT</title>
476
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
479
This environment variable will be assumed to contain the
480
directory containing any helper executables. The use and
481
nature of these helper executables, if any, is
482
purposefully not documented.
355
This program does not use any environment variables, not even
356
the ones provided by <citerefentry><refentrytitle
488
This program does not use any other environment variables, not
489
even the ones provided by <citerefentry><refentrytitle
357
490
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
495
<refsect1 id="network-hooks">
496
<title>NETWORK HOOKS</title>
498
If a network interface like a bridge or tunnel is required to
499
find a Mandos server, this requires the interface to be up and
500
running before <command>&COMMANDNAME;</command> starts looking
501
for Mandos servers. This can be accomplished by creating a
502
<quote>network hook</quote> program, and placing it in a special
506
Before the network is used (and again before program exit), any
507
runnable programs found in the network hook directory are run
508
with the argument <quote><literal>start</literal></quote> or
509
<quote><literal>stop</literal></quote>. This should bring up or
510
down, respectively, any network interface which
511
<command>&COMMANDNAME;</command> should use.
513
<refsect2 id="hook-requirements">
514
<title>REQUIREMENTS</title>
516
A network hook must be an executable file, and its name must
517
consist entirely of upper and lower case letters, digits,
518
underscores, periods, and hyphens.
521
A network hook will receive one argument, which can be one of
526
<term><literal>start</literal></term>
529
This should make the network hook create (if necessary)
530
and bring up a network interface.
535
<term><literal>stop</literal></term>
538
This should make the network hook take down a network
539
interface, and delete it if it did not exist previously.
544
<term><literal>files</literal></term>
547
This should make the network hook print, <emphasis>one
548
file per line</emphasis>, all the files needed for it to
549
run. (These files will be copied into the initial RAM
550
filesystem.) Typical use is for a network hook which is
551
a shell script to print its needed binaries.
554
It is not necessary to print any non-executable files
555
already in the network hook directory, these will be
556
copied implicitly if they otherwise satisfy the name
562
<term><literal>modules</literal></term>
565
This should make the network hook print, <emphasis>on
566
separate lines</emphasis>, all the kernel modules needed
567
for it to run. (These modules will be copied into the
568
initial RAM filesystem.) For instance, a tunnel
570
<quote><literal>tun</literal></quote> module.
576
The network hook will be provided with a number of environment
581
<term><envar>MANDOSNETHOOKDIR</envar></term>
584
The network hook directory, specified to
585
<command>&COMMANDNAME;</command> by the
586
<option>--network-hook-dir</option> option. Note: this
587
should <emphasis>always</emphasis> be used by the
588
network hook to refer to itself or any files in the hook
589
directory it may require.
594
<term><envar>DEVICE</envar></term>
597
The network interfaces, as specified to
598
<command>&COMMANDNAME;</command> by the
599
<option>--interface</option> option, combined to one
600
string and separated by commas. If this is set, and
601
does not contain the interface a hook will bring up,
602
there is no reason for a hook to continue.
607
<term><envar>MODE</envar></term>
610
This will be the same as the first argument;
611
i.e. <quote><literal>start</literal></quote>,
612
<quote><literal>stop</literal></quote>,
613
<quote><literal>files</literal></quote>, or
614
<quote><literal>modules</literal></quote>.
619
<term><envar>VERBOSITY</envar></term>
622
This will be the <quote><literal>1</literal></quote> if
623
the <option>--debug</option> option is passed to
624
<command>&COMMANDNAME;</command>, otherwise
625
<quote><literal>0</literal></quote>.
630
<term><envar>DELAY</envar></term>
633
This will be the same as the <option>--delay</option>
634
option passed to <command>&COMMANDNAME;</command>. Is
635
only set if <envar>MODE</envar> is
636
<quote><literal>start</literal></quote> or
637
<quote><literal>stop</literal></quote>.
642
<term><envar>CONNECT</envar></term>
645
This will be the same as the <option>--connect</option>
646
option passed to <command>&COMMANDNAME;</command>. Is
647
only set if <option>--connect</option> is passed and
648
<envar>MODE</envar> is
649
<quote><literal>start</literal></quote> or
650
<quote><literal>stop</literal></quote>.
656
A hook may not read from standard input, and should be
657
restrictive in printing to standard output or standard error
658
unless <varname>VERBOSITY</varname> is
659
<quote><literal>1</literal></quote>.
664
<refsect1 id="files">
363
665
<title>FILES</title>
668
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
670
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
674
OpenPGP public and private key files, in <quote>ASCII
675
Armor</quote> format. These are the default file names,
676
they can be changed with the <option>--pubkey</option> and
677
<option>--seckey</option> options.
683
class="directory">/lib/mandos/network-hooks.d</filename></term>
686
Directory where network hooks are located. Change this
687
with the <option>--network-hook-dir</option> option. See
688
<xref linkend="network-hooks"/>.
695
<!-- <refsect1 id="bugs"> -->
696
<!-- <title>BUGS</title> -->
374
701
<refsect1 id="example">
375
702
<title>EXAMPLE</title>
704
Note that normally, command line options will not be given
705
directly, but via options for the Mandos <citerefentry
706
><refentrytitle>plugin-runner</refentrytitle>
707
<manvolnum>8mandos</manvolnum></citerefentry>.
711
Normal invocation needs no options, if the network interfaces
712
can be automatically determined:
715
<userinput>&COMMANDNAME;</userinput>
720
Search for Mandos servers (and connect to them) using one
724
<!-- do not wrap this line -->
725
<userinput>&COMMANDNAME; --interface eth1</userinput>
730
Run in debug mode, and use a custom key:
734
<!-- do not wrap this line -->
735
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
741
Run in debug mode, with a custom key, and do not use Zeroconf
742
to locate a server; connect directly to the IPv6 link-local
743
address <quote><systemitem class="ipaddress"
744
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
745
using interface eth2:
749
<!-- do not wrap this line -->
750
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
380
756
<refsect1 id="security">
381
757
<title>SECURITY</title>
759
This program is set-uid to root, but will switch back to the
760
original (and presumably non-privileged) user and group after
761
bringing up the network interface.
764
To use this program for its intended purpose (see <xref
765
linkend="purpose"/>), the password for the root file system will
766
have to be given out to be stored in a server computer, after
767
having been encrypted using an OpenPGP key. This encrypted data
768
which will be stored in a server can only be decrypted by the
769
OpenPGP key, and the data will only be given out to those
770
clients who can prove they actually have that key. This key,
771
however, is stored unencrypted on the client side in its initial
772
<acronym>RAM</acronym> disk image file system. This is normally
773
readable by all, but this is normally fixed during installation
774
of this program; file permissions are set so that no-one is able
778
The only remaining weak point is that someone with physical
779
access to the client hard drive might turn off the client
780
computer, read the OpenPGP keys directly from the hard drive,
781
and communicate with the server. To safeguard against this, the
782
server is supposed to notice the client disappearing and stop
783
giving out the encrypted data. Therefore, it is important to
784
set the timeout and checker interval values tightly on the
785
server. See <citerefentry><refentrytitle
786
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
789
It will also help if the checker program on the server is
790
configured to request something from the client which can not be
791
spoofed by someone else on the network, like SSH server key
792
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
793
echo (<quote>ping</quote>) replies.
796
<emphasis>Note</emphasis>: This makes it completely insecure to
797
have <application >Mandos</application> clients which dual-boot
798
to another operating system which is <emphasis>not</emphasis>
799
trusted to keep the initial <acronym>RAM</acronym> disk image
386
804
<refsect1 id="see_also">
387
805
<title>SEE ALSO</title>
807
<citerefentry><refentrytitle>intro</refentrytitle>
808
<manvolnum>8mandos</manvolnum></citerefentry>,
809
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
810
<manvolnum>8</manvolnum></citerefentry>,
811
<citerefentry><refentrytitle>crypttab</refentrytitle>
812
<manvolnum>5</manvolnum></citerefentry>,
389
813
<citerefentry><refentrytitle>mandos</refentrytitle>
390
814
<manvolnum>8</manvolnum></citerefentry>,
391
815
<citerefentry><refentrytitle>password-prompt</refentrytitle>
393
817
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
394
818
<manvolnum>8mandos</manvolnum></citerefentry>
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>
823
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
827
Zeroconf is the network protocol standard used for finding
828
Mandos servers on the local network.
834
<ulink url="http://www.avahi.org/">Avahi</ulink>
838
Avahi is the library this program calls to find Zeroconf
845
<ulink url="http://www.gnu.org/software/gnutls/"
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="http://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 4346: <citetitle>The Transport Layer Security (TLS)
903
Protocol Version 1.1</citetitle>
907
TLS 1.1 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 5081: <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.
435
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