122
135
</refsynopsisdiv>
124
137
<refsect1 id="description">
125
138
<title>DESCRIPTION</title>
127
140
<command>&COMMANDNAME;</command> is a client program that
128
141
communicates with <citerefentry><refentrytitle
129
142
>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.
143
to get a password. In slightly more detail, this client program
144
brings up network interfaces, uses the interfaces’ IPv6
145
link-local addresses to get network connectivity, uses Zeroconf
146
to find servers on the local network, and communicates with
147
servers using TLS with an OpenPGP key to ensure authenticity and
148
confidentiality. This client program keeps running, trying all
149
servers on the network, until it receives a satisfactory reply
150
or a TERM signal. After all servers have been tried, all
151
servers are periodically retried. If no servers are found it
152
will wait indefinitely for new servers to appear.
155
The network interfaces are selected like this: If any interfaces
156
are specified using the <option>--interface</option> option,
157
those interface are used. Otherwise,
158
<command>&COMMANDNAME;</command> will use all interfaces that
159
are not loopback interfaces, are not point-to-point interfaces,
160
are capable of broadcasting and do not have the NOARP flag (see
161
<citerefentry><refentrytitle>netdevice</refentrytitle>
162
<manvolnum>7</manvolnum></citerefentry>). (If the
163
<option>--connect</option> option is used, point-to-point
164
interfaces and non-broadcast interfaces are accepted.) If any
165
used interfaces are not up and running, they are first taken up
166
(and later taken down again on program exit).
169
Before network interfaces are selected, all <quote>network
170
hooks</quote> are run; see <xref linkend="network-hooks"/>.
137
173
This program is not meant to be run directly; it is really meant
138
174
to run as a plugin of the <application>Mandos</application>
139
175
<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.
176
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
177
initial <acronym>RAM</acronym> disk environment because it is
178
specified as a <quote>keyscript</quote> in the <citerefentry>
179
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
180
</citerefentry> file.
202
220
assumed to separate the address from the port number.
205
This option is normally only useful for debugging.
223
Normally, Zeroconf would be used to locate Mandos servers,
224
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>
231
<term><option>--interface=<replaceable
232
>NAME</replaceable><arg rep='repeat'>,<replaceable
233
>NAME</replaceable></arg></option></term>
230
<replaceable>NAME</replaceable></option></term>
235
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
236
>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>.
239
Comma separated list of network interfaces that will be
240
brought up and scanned for Mandos servers to connect to.
241
The default is the empty string, which will automatically
242
use all appropriate interfaces.
245
If the <option>--connect</option> option is used, and
246
exactly one interface name is specified (except
247
<quote><literal>none</literal></quote>), this specifies
248
the interface to use to connect to the address given.
251
Note that since this program will normally run in the
252
initial RAM disk environment, the interface must be an
253
interface which exists at that stage. Thus, the interface
254
can normally not be a pseudo-interface such as
255
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
256
will not exist until much later in the boot process, and
257
can not be used by this program, unless created by a
258
<quote>network hook</quote> — see <xref
259
linkend="network-hooks"/>.
262
<replaceable>NAME</replaceable> can be the string
263
<quote><literal>none</literal></quote>; this will make
264
<command>&COMMANDNAME;</command> not bring up
265
<emphasis>any</emphasis> interfaces specified
266
<emphasis>after</emphasis> this string. This is not
267
recommended, and only meant for advanced users.
340
437
server could be found and the password received from it could be
341
438
successfully decrypted and output on standard output. The
342
439
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> -->
440
error occurs. Otherwise, it will forever connect to any
441
discovered <application>Mandos</application> servers, trying to
442
get a decryptable password and print it.
446
<refsect1 id="environment">
447
<title>ENVIRONMENT</title>
449
This program does not use any environment variables, not even
450
the ones provided by <citerefentry><refentrytitle
451
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
456
<refsect1 id="network-hooks">
457
<title>NETWORK HOOKS</title>
459
If a network interface like a bridge or tunnel is required to
460
find a Mandos server, this requires the interface to be up and
461
running before <command>&COMMANDNAME;</command> starts looking
462
for Mandos servers. This can be accomplished by creating a
463
<quote>network hook</quote> program, and placing it in a special
467
Before the network is used (and again before program exit), any
468
runnable programs found in the network hook directory are run
469
with the argument <quote><literal>start</literal></quote> or
470
<quote><literal>stop</literal></quote>. This should bring up or
471
down, respectively, any network interface which
472
<command>&COMMANDNAME;</command> should use.
474
<refsect2 id="hook-requirements">
475
<title>REQUIREMENTS</title>
477
A network hook must be an executable file, and its name must
478
consist entirely of upper and lower case letters, digits,
479
underscores, periods, and hyphens.
482
A network hook will receive one argument, which can be one of
487
<term><literal>start</literal></term>
490
This should make the network hook create (if necessary)
491
and bring up a network interface.
496
<term><literal>stop</literal></term>
499
This should make the network hook take down a network
500
interface, and delete it if it did not exist previously.
505
<term><literal>files</literal></term>
508
This should make the network hook print, <emphasis>one
509
file per line</emphasis>, all the files needed for it to
510
run. (These files will be copied into the initial RAM
511
filesystem.) Typical use is for a network hook which is
512
a shell script to print its needed binaries.
515
It is not necessary to print any non-executable files
516
already in the network hook directory, these will be
517
copied implicitly if they otherwise satisfy the name
523
<term><literal>modules</literal></term>
526
This should make the network hook print, <emphasis>on
527
separate lines</emphasis>, all the kernel modules needed
528
for it to run. (These modules will be copied into the
529
initial RAM filesystem.) For instance, a tunnel
531
<quote><literal>tun</literal></quote> module.
537
The network hook will be provided with a number of environment
542
<term><envar>MANDOSNETHOOKDIR</envar></term>
545
The network hook directory, specified to
546
<command>&COMMANDNAME;</command> by the
547
<option>--network-hook-dir</option> option. Note: this
548
should <emphasis>always</emphasis> be used by the
549
network hook to refer to itself or any files in the hook
550
directory it may require.
555
<term><envar>DEVICE</envar></term>
558
The network interfaces, as specified to
559
<command>&COMMANDNAME;</command> by the
560
<option>--interface</option> option, combined to one
561
string and separated by commas. If this is set, and
562
does not contain the interface a hook will bring up,
563
there is no reason for a hook to continue.
568
<term><envar>MODE</envar></term>
571
This will be the same as the first argument;
572
i.e. <quote><literal>start</literal></quote>,
573
<quote><literal>stop</literal></quote>,
574
<quote><literal>files</literal></quote>, or
575
<quote><literal>modules</literal></quote>.
580
<term><envar>VERBOSITY</envar></term>
583
This will be the <quote><literal>1</literal></quote> if
584
the <option>--debug</option> option is passed to
585
<command>&COMMANDNAME;</command>, otherwise
586
<quote><literal>0</literal></quote>.
591
<term><envar>DELAY</envar></term>
594
This will be the same as the <option>--delay</option>
595
option passed to <command>&COMMANDNAME;</command>. Is
596
only set if <envar>MODE</envar> is
597
<quote><literal>start</literal></quote> or
598
<quote><literal>stop</literal></quote>.
603
<term><envar>CONNECT</envar></term>
606
This will be the same as the <option>--connect</option>
607
option passed to <command>&COMMANDNAME;</command>. Is
608
only set if <option>--connect</option> is passed and
609
<envar>MODE</envar> is
610
<quote><literal>start</literal></quote> or
611
<quote><literal>stop</literal></quote>.
617
A hook may not read from standard input, and should be
618
restrictive in printing to standard output or standard error
619
unless <varname>VERBOSITY</varname> is
620
<quote><literal>1</literal></quote>.
625
<refsect1 id="files">
629
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
631
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
635
OpenPGP public and private key files, in <quote>ASCII
636
Armor</quote> format. These are the default file names,
637
they can be changed with the <option>--pubkey</option> and
638
<option>--seckey</option> options.
644
class="directory">/lib/mandos/network-hooks.d</filename></term>
647
Directory where network hooks are located. Change this
648
with the <option>--network-hook-dir</option> option. See
649
<xref linkend="network-hooks"/>.
656
<!-- <refsect1 id="bugs"> -->
657
<!-- <title>BUGS</title> -->
352
<!-- This program does not use any environment variables. -->
354
660
<!-- </refsect1> -->
368
662
<refsect1 id="example">
369
663
<title>EXAMPLE</title>
665
Note that normally, command line options will not be given
666
directly, but via options for the Mandos <citerefentry
667
><refentrytitle>plugin-runner</refentrytitle>
668
<manvolnum>8mandos</manvolnum></citerefentry>.
672
Normal invocation needs no options, if the network interfaces
673
can be automatically determined:
676
<userinput>&COMMANDNAME;</userinput>
681
Search for Mandos servers (and connect to them) using one
685
<!-- do not wrap this line -->
686
<userinput>&COMMANDNAME; --interface eth1</userinput>
691
Run in debug mode, and use a custom key:
695
<!-- do not wrap this line -->
696
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
702
Run in debug mode, with a custom key, and do not use Zeroconf
703
to locate a server; connect directly to the IPv6 link-local
704
address <quote><systemitem class="ipaddress"
705
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
706
using interface eth2:
710
<!-- do not wrap this line -->
711
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
374
717
<refsect1 id="security">
375
718
<title>SECURITY</title>
720
This program is set-uid to root, but will switch back to the
721
original (and presumably non-privileged) user and group after
722
bringing up the network interface.
725
To use this program for its intended purpose (see <xref
726
linkend="purpose"/>), the password for the root file system will
727
have to be given out to be stored in a server computer, after
728
having been encrypted using an OpenPGP key. This encrypted data
729
which will be stored in a server can only be decrypted by the
730
OpenPGP key, and the data will only be given out to those
731
clients who can prove they actually have that key. This key,
732
however, is stored unencrypted on the client side in its initial
733
<acronym>RAM</acronym> disk image file system. This is normally
734
readable by all, but this is normally fixed during installation
735
of this program; file permissions are set so that no-one is able
739
The only remaining weak point is that someone with physical
740
access to the client hard drive might turn off the client
741
computer, read the OpenPGP keys directly from the hard drive,
742
and communicate with the server. To safeguard against this, the
743
server is supposed to notice the client disappearing and stop
744
giving out the encrypted data. Therefore, it is important to
745
set the timeout and checker interval values tightly on the
746
server. See <citerefentry><refentrytitle
747
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
750
It will also help if the checker program on the server is
751
configured to request something from the client which can not be
752
spoofed by someone else on the network, unlike unencrypted
753
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
756
<emphasis>Note</emphasis>: This makes it completely insecure to
757
have <application >Mandos</application> clients which dual-boot
758
to another operating system which is <emphasis>not</emphasis>
759
trusted to keep the initial <acronym>RAM</acronym> disk image
380
764
<refsect1 id="see_also">
381
765
<title>SEE ALSO</title>
767
<citerefentry><refentrytitle>intro</refentrytitle>
768
<manvolnum>8mandos</manvolnum></citerefentry>,
769
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
770
<manvolnum>8</manvolnum></citerefentry>,
771
<citerefentry><refentrytitle>crypttab</refentrytitle>
772
<manvolnum>5</manvolnum></citerefentry>,
383
773
<citerefentry><refentrytitle>mandos</refentrytitle>
384
774
<manvolnum>8</manvolnum></citerefentry>,
385
775
<citerefentry><refentrytitle>password-prompt</refentrytitle>
387
777
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
388
778
<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>
783
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
787
Zeroconf is the network protocol standard used for finding
788
Mandos servers on the local network.
794
<ulink url="http://www.avahi.org/">Avahi</ulink>
798
Avahi is the library this program calls to find Zeroconf
805
<ulink url="http://www.gnu.org/software/gnutls/"
810
GnuTLS is the library this client uses to implement TLS for
811
communicating securely with the server, and at the same time
812
send the public OpenPGP key to the server.
818
<ulink url="http://www.gnupg.org/related_software/gpgme/"
823
GPGME is the library used to decrypt the OpenPGP data sent
830
RFC 4291: <citetitle>IP Version 6 Addressing
831
Architecture</citetitle>
836
<term>Section 2.2: <citetitle>Text Representation of
837
Addresses</citetitle></term>
838
<listitem><para/></listitem>
841
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
842
Address</citetitle></term>
843
<listitem><para/></listitem>
846
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
847
Addresses</citetitle></term>
850
This client uses IPv6 link-local addresses, which are
851
immediately usable since a link-local addresses is
852
automatically assigned to a network interface when it
862
RFC 4346: <citetitle>The Transport Layer Security (TLS)
863
Protocol Version 1.1</citetitle>
867
TLS 1.1 is the protocol implemented by GnuTLS.
873
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
877
The data received from the server is binary encrypted
884
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
889
This is implemented by GnuTLS and used by this program so
890
that OpenPGP keys can be used.
429
898
<!-- Local Variables: -->
430
899
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
431
900
<!-- time-stamp-end: "[\"']>" -->