122
133
</refsynopsisdiv>
124
135
<refsect1 id="description">
125
136
<title>DESCRIPTION</title>
127
138
<command>&COMMANDNAME;</command> is a client program that
128
139
communicates with <citerefentry><refentrytitle
129
140
>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.
141
to get a password. In slightly more detail, this client program
142
brings up network interfaces, uses the interfaces’ IPv6
143
link-local addresses to get network connectivity, uses Zeroconf
144
to find servers on the local network, and communicates with
145
servers using TLS with an OpenPGP key to ensure authenticity and
146
confidentiality. This client program keeps running, trying all
147
servers on the network, until it receives a satisfactory reply
148
or a TERM signal. After all servers have been tried, all
149
servers are periodically retried. If no servers are found it
150
will wait indefinitely for new servers to appear.
153
The network interfaces are selected like this: If any interfaces
154
are specified using the <option>--interface</option> option,
155
those interface are used. Otherwise,
156
<command>&COMMANDNAME;</command> will use all interfaces that
157
are not loopback interfaces, are not point-to-point interfaces,
158
are capable of broadcasting and do not have the NOARP flag (see
159
<citerefentry><refentrytitle>netdevice</refentrytitle>
160
<manvolnum>7</manvolnum></citerefentry>). (If the
161
<option>--connect</option> option is used, point-to-point
162
interfaces and non-broadcast interfaces are accepted.) If any
163
used interfaces are not up and running, they are first taken up
164
(and later taken down again on program exit).
167
Before network interfaces are selected, all <quote>network
168
hooks</quote> are run; see <xref linkend="network-hooks"/>.
137
171
This program is not meant to be run directly; it is really meant
138
172
to run as a plugin of the <application>Mandos</application>
139
173
<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.
174
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
175
initial <acronym>RAM</acronym> disk environment because it is
176
specified as a <quote>keyscript</quote> in the <citerefentry>
177
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
178
</citerefentry> file.
202
218
assumed to separate the address from the port number.
205
This option is normally only useful for debugging.
221
This option is normally only useful for testing and
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>
228
<term><option>--interface=<replaceable
229
>NAME</replaceable><arg rep='repeat'>,<replaceable
230
>NAME</replaceable></arg></option></term>
230
<replaceable>NAME</replaceable></option></term>
232
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
233
>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>.
236
Comma separated list of network interfaces that will be
237
brought up and scanned for Mandos servers to connect to.
238
The default is the empty string, which will automatically
239
use all appropriate interfaces.
242
If the <option>--connect</option> option is used, and
243
exactly one interface name is specified (except
244
<quote><literal>none</literal></quote>), this specifies
245
the interface to use to connect to the address given.
248
Note that since this program will normally run in the
249
initial RAM disk environment, the interface must be an
250
interface which exists at that stage. Thus, the interface
251
can normally not be a pseudo-interface such as
252
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
253
will not exist until much later in the boot process, and
254
can not be used by this program, unless created by a
255
<quote>network hook</quote> — see <xref
256
linkend="network-hooks"/>.
259
<replaceable>NAME</replaceable> can be the string
260
<quote><literal>none</literal></quote>; this will make
261
<command>&COMMANDNAME;</command> not bring up
262
<emphasis>any</emphasis> interfaces specified
263
<emphasis>after</emphasis> this string. This is not
264
recommended, and only meant for advanced users.
340
434
server could be found and the password received from it could be
341
435
successfully decrypted and output on standard output. The
342
436
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> -->
437
error occurs. Otherwise, it will forever connect to any
438
discovered <application>Mandos</application> servers, trying to
439
get a decryptable password and print it.
443
<refsect1 id="environment">
444
<title>ENVIRONMENT</title>
446
This program does not use any environment variables, not even
447
the ones provided by <citerefentry><refentrytitle
448
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
453
<refsect1 id="network-hooks">
454
<title>NETWORK HOOKS</title>
456
If a network interface like a bridge or tunnel is required to
457
find a Mandos server, this requires the interface to be up and
458
running before <command>&COMMANDNAME;</command> starts looking
459
for Mandos servers. This can be accomplished by creating a
460
<quote>network hook</quote> program, and placing it in a special
464
Before the network is used (and again before program exit), any
465
runnable programs found in the network hook directory are run
466
with the argument <quote><literal>start</literal></quote> or
467
<quote><literal>stop</literal></quote>. This should bring up or
468
down, respectively, any network interface which
469
<command>&COMMANDNAME;</command> should use.
471
<refsect2 id="hook-requirements">
472
<title>REQUIREMENTS</title>
474
A network hook must be an executable file, and its name must
475
consist entirely of upper and lower case letters, digits,
476
underscores, periods, and hyphens.
479
A network hook will receive one argument, which can be one of
484
<term><literal>start</literal></term>
487
This should make the network hook create (if necessary)
488
and bring up a network interface.
493
<term><literal>stop</literal></term>
496
This should make the network hook take down a network
497
interface, and delete it if it did not exist previously.
502
<term><literal>files</literal></term>
505
This should make the network hook print, <emphasis>one
506
file per line</emphasis>, all the files needed for it to
507
run. (These files will be copied into the initial RAM
508
filesystem.) Typical use is for a network hook which is
509
a shell script to print its needed binaries.
512
It is not necessary to print any non-executable files
513
already in the network hook directory, these will be
514
copied implicitly if they otherwise satisfy the name
520
<term><literal>modules</literal></term>
523
This should make the network hook print, <emphasis>on
524
separate lines</emphasis>, all the kernel modules needed
525
for it to run. (These modules will be copied into the
526
initial RAM filesystem.) For instance, a tunnel
528
<quote><literal>tun</literal></quote> module.
534
The network hook will be provided with a number of environment
539
<term><envar>MANDOSNETHOOKDIR</envar></term>
542
The network hook directory, specified to
543
<command>&COMMANDNAME;</command> by the
544
<option>--network-hook-dir</option> option. Note: this
545
should <emphasis>always</emphasis> be used by the
546
network hook to refer to itself or any files in the hook
547
directory it may require.
552
<term><envar>DEVICE</envar></term>
555
The network interfaces, as specified to
556
<command>&COMMANDNAME;</command> by the
557
<option>--interface</option> option, combined to one
558
string and separated by commas. If this is set, and
559
does not contain the interface a hook will bring up,
560
there is no reason for a hook to continue.
565
<term><envar>MODE</envar></term>
568
This will be the same as the first argument;
569
i.e. <quote><literal>start</literal></quote>,
570
<quote><literal>stop</literal></quote>,
571
<quote><literal>files</literal></quote>, or
572
<quote><literal>modules</literal></quote>.
577
<term><envar>VERBOSITY</envar></term>
580
This will be the <quote><literal>1</literal></quote> if
581
the <option>--debug</option> option is passed to
582
<command>&COMMANDNAME;</command>, otherwise
583
<quote><literal>0</literal></quote>.
588
<term><envar>DELAY</envar></term>
591
This will be the same as the <option>--delay</option>
592
option passed to <command>&COMMANDNAME;</command>. Is
593
only set if <envar>MODE</envar> is
594
<quote><literal>start</literal></quote> or
595
<quote><literal>stop</literal></quote>.
600
<term><envar>CONNECT</envar></term>
603
This will be the same as the <option>--connect</option>
604
option passed to <command>&COMMANDNAME;</command>. Is
605
only set if <option>--connect</option> is passed and
606
<envar>MODE</envar> is
607
<quote><literal>start</literal></quote> or
608
<quote><literal>stop</literal></quote>.
614
A hook may not read from standard input, and should be
615
restrictive in printing to standard output or standard error
616
unless <varname>VERBOSITY</varname> is
617
<quote><literal>1</literal></quote>.
622
<refsect1 id="files">
626
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
628
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
632
OpenPGP public and private key files, in <quote>ASCII
633
Armor</quote> format. These are the default file names,
634
they can be changed with the <option>--pubkey</option> and
635
<option>--seckey</option> options.
641
class="directory">/lib/mandos/network-hooks.d</filename></term>
644
Directory where network hooks are located. Change this
645
with the <option>--network-hook-dir</option> option. See
646
<xref linkend="network-hooks"/>.
653
<!-- <refsect1 id="bugs"> -->
654
<!-- <title>BUGS</title> -->
352
<!-- This program does not use any environment variables. -->
354
657
<!-- </refsect1> -->
368
659
<refsect1 id="example">
369
660
<title>EXAMPLE</title>
662
Note that normally, command line options will not be given
663
directly, but via options for the Mandos <citerefentry
664
><refentrytitle>plugin-runner</refentrytitle>
665
<manvolnum>8mandos</manvolnum></citerefentry>.
669
Normal invocation needs no options, if the network interface
670
can be automatically determined:
673
<userinput>&COMMANDNAME;</userinput>
678
Search for Mandos servers (and connect to them) using another
682
<!-- do not wrap this line -->
683
<userinput>&COMMANDNAME; --interface eth1</userinput>
688
Run in debug mode, and use a custom key:
692
<!-- do not wrap this line -->
693
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
699
Run in debug mode, with a custom key, and do not use Zeroconf
700
to locate a server; connect directly to the IPv6 link-local
701
address <quote><systemitem class="ipaddress"
702
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
703
using interface eth2:
707
<!-- do not wrap this line -->
708
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
374
714
<refsect1 id="security">
375
715
<title>SECURITY</title>
717
This program is set-uid to root, but will switch back to the
718
original (and presumably non-privileged) user and group after
719
bringing up the network interface.
722
To use this program for its intended purpose (see <xref
723
linkend="purpose"/>), the password for the root file system will
724
have to be given out to be stored in a server computer, after
725
having been encrypted using an OpenPGP key. This encrypted data
726
which will be stored in a server can only be decrypted by the
727
OpenPGP key, and the data will only be given out to those
728
clients who can prove they actually have that key. This key,
729
however, is stored unencrypted on the client side in its initial
730
<acronym>RAM</acronym> disk image file system. This is normally
731
readable by all, but this is normally fixed during installation
732
of this program; file permissions are set so that no-one is able
736
The only remaining weak point is that someone with physical
737
access to the client hard drive might turn off the client
738
computer, read the OpenPGP keys directly from the hard drive,
739
and communicate with the server. To safeguard against this, the
740
server is supposed to notice the client disappearing and stop
741
giving out the encrypted data. Therefore, it is important to
742
set the timeout and checker interval values tightly on the
743
server. See <citerefentry><refentrytitle
744
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
747
It will also help if the checker program on the server is
748
configured to request something from the client which can not be
749
spoofed by someone else on the network, unlike unencrypted
750
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
753
<emphasis>Note</emphasis>: This makes it completely insecure to
754
have <application >Mandos</application> clients which dual-boot
755
to another operating system which is <emphasis>not</emphasis>
756
trusted to keep the initial <acronym>RAM</acronym> disk image
380
761
<refsect1 id="see_also">
381
762
<title>SEE ALSO</title>
764
<citerefentry><refentrytitle>intro</refentrytitle>
765
<manvolnum>8mandos</manvolnum></citerefentry>,
766
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
767
<manvolnum>8</manvolnum></citerefentry>,
768
<citerefentry><refentrytitle>crypttab</refentrytitle>
769
<manvolnum>5</manvolnum></citerefentry>,
383
770
<citerefentry><refentrytitle>mandos</refentrytitle>
384
771
<manvolnum>8</manvolnum></citerefentry>,
385
772
<citerefentry><refentrytitle>password-prompt</refentrytitle>
387
774
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
388
775
<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>
780
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
784
Zeroconf is the network protocol standard used for finding
785
Mandos servers on the local network.
791
<ulink url="http://www.avahi.org/">Avahi</ulink>
795
Avahi is the library this program calls to find Zeroconf
802
<ulink url="http://www.gnu.org/software/gnutls/"
807
GnuTLS is the library this client uses to implement TLS for
808
communicating securely with the server, and at the same time
809
send the public OpenPGP key to the server.
815
<ulink url="http://www.gnupg.org/related_software/gpgme/"
820
GPGME is the library used to decrypt the OpenPGP data sent
827
RFC 4291: <citetitle>IP Version 6 Addressing
828
Architecture</citetitle>
833
<term>Section 2.2: <citetitle>Text Representation of
834
Addresses</citetitle></term>
835
<listitem><para/></listitem>
838
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
839
Address</citetitle></term>
840
<listitem><para/></listitem>
843
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
844
Addresses</citetitle></term>
847
This client uses IPv6 link-local addresses, which are
848
immediately usable since a link-local addresses is
849
automatically assigned to a network interface when it
859
RFC 4346: <citetitle>The Transport Layer Security (TLS)
860
Protocol Version 1.1</citetitle>
864
TLS 1.1 is the protocol implemented by GnuTLS.
870
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
874
The data received from the server is binary encrypted
881
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
886
This is implemented by GnuTLS and used by this program so
887
that OpenPGP keys can be used.
429
895
<!-- Local Variables: -->
430
896
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
431
897
<!-- time-stamp-end: "[\"']>" -->