160
122
</refsynopsisdiv>
162
124
<refsect1 id="description">
163
125
<title>DESCRIPTION</title>
165
127
<command>&COMMANDNAME;</command> is a client program that
166
128
communicates with <citerefentry><refentrytitle
167
129
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
168
to get a password. In slightly more detail, this client program
169
brings up network interfaces, uses the interfaces’ IPv6
170
link-local addresses to get network connectivity, uses Zeroconf
171
to find servers on the local network, and communicates with
172
servers using TLS with a raw public key to ensure authenticity
173
and confidentiality. This client program keeps running, trying
174
all servers on the network, until it receives a satisfactory
175
reply or a TERM signal. After all servers have been tried, all
176
servers are periodically retried. If no servers are found it
177
will wait indefinitely for new servers to appear.
180
The network interfaces are selected like this: If any interfaces
181
are specified using the <option>--interface</option> option,
182
those interface are used. Otherwise,
183
<command>&COMMANDNAME;</command> will use all interfaces that
184
are not loopback interfaces, are not point-to-point interfaces,
185
are capable of broadcasting and do not have the NOARP flag (see
186
<citerefentry><refentrytitle>netdevice</refentrytitle>
187
<manvolnum>7</manvolnum></citerefentry>). (If the
188
<option>--connect</option> option is used, point-to-point
189
interfaces and non-broadcast interfaces are accepted.) If any
190
used interfaces are not up and running, they are first taken up
191
(and later taken down again on program exit).
194
Before network interfaces are selected, all <quote>network
195
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.
198
137
This program is not meant to be run directly; it is really meant
245
184
assumed to separate the address from the port number.
248
Normally, Zeroconf would be used to locate Mandos servers,
249
in which case this option would only be used when testing
187
This option is normally only useful for testing and
256
<term><option>--interface=<replaceable
257
>NAME</replaceable><arg rep='repeat'>,<replaceable
258
>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>
260
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
261
>NAME</replaceable></arg></option></term>
213
<replaceable>NAME</replaceable></option></term>
264
Comma separated list of network interfaces that will be
265
brought up and scanned for Mandos servers to connect to.
266
The default is the empty string, which will automatically
267
use all appropriate interfaces.
270
If the <option>--connect</option> option is used, and
271
exactly one interface name is specified (except
272
<quote><literal>none</literal></quote>), this specifies
273
the interface to use to connect to the address given.
276
Note that since this program will normally run in the
277
initial RAM disk environment, the interface must be an
278
interface which exists at that stage. Thus, the interface
279
can normally not be a pseudo-interface such as
280
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
281
will not exist until much later in the boot process, and
282
can not be used by this program, unless created by a
283
<quote>network hook</quote> — see <xref
284
linkend="network-hooks"/>.
287
<replaceable>NAME</replaceable> can be the string
288
<quote><literal>none</literal></quote>; this will make
289
<command>&COMMANDNAME;</command> only bring up interfaces
290
specified <emphasis>before</emphasis> this string. This
291
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>.
357
258
xpointer="priority"/>
362
263
<term><option>--dh-bits=<replaceable
363
264
>BITS</replaceable></option></term>
366
267
Sets the number of bits to use for the prime number in the
367
TLS Diffie-Hellman key exchange. The default value is
368
selected automatically based on the GnuTLS security
369
profile set in its priority string. Note that if the
370
<option>--dh-params</option> option is used, the values
371
from that file will be used instead.
377
<term><option>--dh-params=<replaceable
378
>FILE</replaceable></option></term>
381
Specifies a PEM-encoded PKCS#3 file to read the parameters
382
needed by the TLS Diffie-Hellman key exchange from. If
383
this option is not given, or if the file for some reason
384
could not be used, the parameters will be generated on
385
startup, which will take some time and processing power.
386
Those using servers running under time, power or processor
387
constraints may want to generate such a file in advance
394
<term><option>--delay=<replaceable
395
>SECONDS</replaceable></option></term>
398
After bringing a network interface up, the program waits
399
for the interface to arrive in a <quote>running</quote>
400
state before proceeding. During this time, the kernel log
401
level will be lowered to reduce clutter on the system
402
console, alleviating any other plugins which might be
403
using the system console. This option sets the upper
404
limit of seconds to wait. The default is 2.5 seconds.
410
<term><option>--retry=<replaceable
411
>SECONDS</replaceable></option></term>
414
All Mandos servers are tried repeatedly until a password
415
is received. This value specifies, in seconds, how long
416
between each successive try <emphasis>for the same
417
server</emphasis>. The default is 10 seconds.
423
<term><option>--network-hook-dir=<replaceable
424
>DIR</replaceable></option></term>
427
Network hook directory. The default directory is
428
<quote><filename class="directory"
429
>/lib/mandos/network-hooks.d</filename></quote>.
268
TLS Diffie-Hellman key exchange. Default is 1024.
510
343
server could be found and the password received from it could be
511
344
successfully decrypted and output on standard output. The
512
345
program will exit with a non-zero exit status only if a critical
513
error occurs. Otherwise, it will forever connect to any
514
discovered <application>Mandos</application> servers, trying to
515
get a decryptable password and print it.
346
error occurs. Otherwise, it will forever connect to new
347
<application>Mandosservers</application> servers as they appear,
348
trying to get a decryptable password.
519
352
<refsect1 id="environment">
520
353
<title>ENVIRONMENT</title>
523
<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
526
This environment variable will be assumed to contain the
527
directory containing any helper executables. The use and
528
nature of these helper executables, if any, is purposely
535
This program does not use any other environment variables, not
536
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
537
357
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
542
<refsect1 id="network-hooks">
543
<title>NETWORK HOOKS</title>
545
If a network interface like a bridge or tunnel is required to
546
find a Mandos server, this requires the interface to be up and
547
running before <command>&COMMANDNAME;</command> starts looking
548
for Mandos servers. This can be accomplished by creating a
549
<quote>network hook</quote> program, and placing it in a special
553
Before the network is used (and again before program exit), any
554
runnable programs found in the network hook directory are run
555
with the argument <quote><literal>start</literal></quote> or
556
<quote><literal>stop</literal></quote>. This should bring up or
557
down, respectively, any network interface which
558
<command>&COMMANDNAME;</command> should use.
560
<refsect2 id="hook-requirements">
561
<title>REQUIREMENTS</title>
563
A network hook must be an executable file, and its name must
564
consist entirely of upper and lower case letters, digits,
565
underscores, periods, and hyphens.
568
A network hook will receive one argument, which can be one of
573
<term><literal>start</literal></term>
576
This should make the network hook create (if necessary)
577
and bring up a network interface.
582
<term><literal>stop</literal></term>
585
This should make the network hook take down a network
586
interface, and delete it if it did not exist previously.
591
<term><literal>files</literal></term>
594
This should make the network hook print, <emphasis>one
595
file per line</emphasis>, all the files needed for it to
596
run. (These files will be copied into the initial RAM
597
filesystem.) Typical use is for a network hook which is
598
a shell script to print its needed binaries.
601
It is not necessary to print any non-executable files
602
already in the network hook directory, these will be
603
copied implicitly if they otherwise satisfy the name
609
<term><literal>modules</literal></term>
612
This should make the network hook print, <emphasis>on
613
separate lines</emphasis>, all the kernel modules needed
614
for it to run. (These modules will be copied into the
615
initial RAM filesystem.) For instance, a tunnel
617
<quote><literal>tun</literal></quote> module.
623
The network hook will be provided with a number of environment
628
<term><envar>MANDOSNETHOOKDIR</envar></term>
631
The network hook directory, specified to
632
<command>&COMMANDNAME;</command> by the
633
<option>--network-hook-dir</option> option. Note: this
634
should <emphasis>always</emphasis> be used by the
635
network hook to refer to itself or any files in the hook
636
directory it may require.
641
<term><envar>DEVICE</envar></term>
644
The network interfaces, as specified to
645
<command>&COMMANDNAME;</command> by the
646
<option>--interface</option> option, combined to one
647
string and separated by commas. If this is set, and
648
does not contain the interface a hook will bring up,
649
there is no reason for a hook to continue.
654
<term><envar>MODE</envar></term>
657
This will be the same as the first argument;
658
i.e. <quote><literal>start</literal></quote>,
659
<quote><literal>stop</literal></quote>,
660
<quote><literal>files</literal></quote>, or
661
<quote><literal>modules</literal></quote>.
666
<term><envar>VERBOSITY</envar></term>
669
This will be the <quote><literal>1</literal></quote> if
670
the <option>--debug</option> option is passed to
671
<command>&COMMANDNAME;</command>, otherwise
672
<quote><literal>0</literal></quote>.
677
<term><envar>DELAY</envar></term>
680
This will be the same as the <option>--delay</option>
681
option passed to <command>&COMMANDNAME;</command>. Is
682
only set if <envar>MODE</envar> is
683
<quote><literal>start</literal></quote> or
684
<quote><literal>stop</literal></quote>.
689
<term><envar>CONNECT</envar></term>
692
This will be the same as the <option>--connect</option>
693
option passed to <command>&COMMANDNAME;</command>. Is
694
only set if <option>--connect</option> is passed and
695
<envar>MODE</envar> is
696
<quote><literal>start</literal></quote> or
697
<quote><literal>stop</literal></quote>.
703
A hook may not read from standard input, and should be
704
restrictive in printing to standard output or standard error
705
unless <varname>VERBOSITY</varname> is
706
<quote><literal>1</literal></quote>.
711
<refsect1 id="files">
712
363
<title>FILES</title>
715
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
717
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
721
OpenPGP public and private key files, in <quote>ASCII
722
Armor</quote> format. These are the default file names,
723
they can be changed with the <option>--pubkey</option> and
724
<option>--seckey</option> options.
729
<term><filename>/conf/conf.d/mandos/tls-pubkey.pem</filename
731
<term><filename>/conf/conf.d/mandos/tls-privkey.pem</filename
735
Public and private raw key files, in <quote>PEM</quote>
736
format. These are the default file names, they can be
737
changed with the <option>--tls-pubkey</option> and
738
<option>--tls-privkey</option> options.
744
class="directory">/lib/mandos/network-hooks.d</filename></term>
747
Directory where network hooks are located. Change this
748
with the <option>--network-hook-dir</option> option. See
749
<xref linkend="network-hooks"/>.
756
368
<refsect1 id="bugs">
757
369
<title>BUGS</title>
758
<xi:include href="../bugs.xml"/>
761
374
<refsect1 id="example">
762
375
<title>EXAMPLE</title>
764
Note that normally, command line options will not be given
765
directly, but via options for the Mandos <citerefentry
766
><refentrytitle>plugin-runner</refentrytitle>
767
<manvolnum>8mandos</manvolnum></citerefentry>.
771
Normal invocation needs no options, if the network interfaces
772
can be automatically determined:
775
<userinput>&COMMANDNAME;</userinput>
780
Search for Mandos servers (and connect to them) using one
784
<!-- do not wrap this line -->
785
<userinput>&COMMANDNAME; --interface eth1</userinput>
790
Run in debug mode, and use custom keys:
794
<!-- do not wrap this line -->
795
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --tls-pubkey keydir/tls-pubkey.pem --tls-privkey keydir/tls-privkey.pem</userinput>
801
Run in debug mode, with custom keys, and do not use Zeroconf
802
to locate a server; connect directly to the IPv6 link-local
803
address <quote><systemitem class="ipaddress"
804
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
805
using interface eth2:
809
<!-- do not wrap this line -->
810
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --tls-pubkey keydir/tls-pubkey.pem --tls-privkey keydir/tls-privkey.pem --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
816
380
<refsect1 id="security">
817
381
<title>SECURITY</title>
819
This program assumes that it is set-uid to root, and will switch
820
back to the original (and presumably non-privileged) user and
821
group after bringing up the network interface.
824
To use this program for its intended purpose (see <xref
825
linkend="purpose"/>), the password for the root file system will
826
have to be given out to be stored in a server computer, after
827
having been encrypted using an OpenPGP key. This encrypted data
828
which will be stored in a server can only be decrypted by the
829
OpenPGP key, and the data will only be given out to those
830
clients who can prove they actually have that key. This key,
831
however, is stored unencrypted on the client side in its initial
832
<acronym>RAM</acronym> disk image file system. This is normally
833
readable by all, but this is normally fixed during installation
834
of this program; file permissions are set so that no-one is able
838
The only remaining weak point is that someone with physical
839
access to the client hard drive might turn off the client
840
computer, read the OpenPGP and TLS keys directly from the hard
841
drive, and communicate with the server. To safeguard against
842
this, the server is supposed to notice the client disappearing
843
and stop giving out the encrypted data. Therefore, it is
844
important to set the timeout and checker interval values tightly
845
on the server. See <citerefentry><refentrytitle
846
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
849
It will also help if the checker program on the server is
850
configured to request something from the client which can not be
851
spoofed by someone else on the network, like SSH server key
852
fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
853
echo (<quote>ping</quote>) replies.
856
<emphasis>Note</emphasis>: This makes it completely insecure to
857
have <application >Mandos</application> clients which dual-boot
858
to another operating system which is <emphasis>not</emphasis>
859
trusted to keep the initial <acronym>RAM</acronym> disk image
864
386
<refsect1 id="see_also">
865
387
<title>SEE ALSO</title>
867
<citerefentry><refentrytitle>intro</refentrytitle>
868
<manvolnum>8mandos</manvolnum></citerefentry>,
869
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
870
<manvolnum>8</manvolnum></citerefentry>,
871
<citerefentry><refentrytitle>crypttab</refentrytitle>
872
<manvolnum>5</manvolnum></citerefentry>,
873
389
<citerefentry><refentrytitle>mandos</refentrytitle>
874
390
<manvolnum>8</manvolnum></citerefentry>,
875
391
<citerefentry><refentrytitle>password-prompt</refentrytitle>
877
393
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
878
394
<manvolnum>8mandos</manvolnum></citerefentry>
883
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
887
Zeroconf is the network protocol standard used for finding
888
Mandos servers on the local network.
894
<ulink url="https://www.avahi.org/">Avahi</ulink>
898
Avahi is the library this program calls to find Zeroconf
905
<ulink url="https://www.gnutls.org/">GnuTLS</ulink>
909
GnuTLS is the library this client uses to implement TLS for
910
communicating securely with the server, and at the same time
911
send the public key to the server.
917
<ulink url="https://www.gnupg.org/related_software/gpgme/"
922
GPGME is the library used to decrypt the OpenPGP data sent
929
RFC 4291: <citetitle>IP Version 6 Addressing
930
Architecture</citetitle>
935
<term>Section 2.2: <citetitle>Text Representation of
936
Addresses</citetitle></term>
937
<listitem><para/></listitem>
940
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
941
Address</citetitle></term>
942
<listitem><para/></listitem>
945
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
946
Addresses</citetitle></term>
949
This client uses IPv6 link-local addresses, which are
950
immediately usable since a link-local addresses is
951
automatically assigned to a network interface when it
961
RFC 5246: <citetitle>The Transport Layer Security (TLS)
962
Protocol Version 1.2</citetitle>
966
TLS 1.2 is the protocol implemented by GnuTLS.
972
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
976
The data received from the server is binary encrypted
983
RFC 7250: <citetitle>Using Raw Public Keys in Transport
984
Layer Security (TLS) and Datagram Transport Layer Security
989
This is implemented by GnuTLS in version 3.6.6 and is, if
990
present, used by this program so that raw public keys can be
997
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
1002
This is implemented by GnuTLS before version 3.6.0 and is,
1003
if present, used by this program so that OpenPGP keys can be
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>
1012
435
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