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131
</refsynopsisdiv>
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<refsect1 id="description">
125
134
<title>DESCRIPTION</title>
127
136
<command>&COMMANDNAME;</command> is a client program that
128
137
communicates with <citerefentry><refentrytitle
129
138
>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 servers, and TLS with an
132
OpenPGP key to ensure authenticity and confidentiality. It
133
keeps running, trying all servers on the network, until it
134
receives a satisfactory reply or a TERM signal is recieved.
139
to get a password. In slightly more detail, this client program
140
brings up a network interface, uses the interface’s IPv6
141
link-local address to get network connectivity, uses Zeroconf to
142
find servers on the local network, and communicates with servers
143
using TLS with an OpenPGP key to ensure authenticity and
144
confidentiality. This client program keeps running, trying all
145
servers on the network, until it receives a satisfactory reply
146
or a TERM signal. After all servers have been tried, all
147
servers are periodically retried. If no servers are found it
148
will wait indefinitely for new servers to appear.
151
The network interface is selected like this: If an interface is
152
specified using the <option>--interface</option> option, that
153
interface is used. Otherwise, <command>&COMMANDNAME;</command>
154
will choose any interface that is up and running and is not a
155
loopback interface, is not a point-to-point interface, is
156
capable of broadcasting and does not have the NOARP flag (see
157
<citerefentry><refentrytitle>netdevice</refentrytitle>
158
<manvolnum>7</manvolnum></citerefentry>). (If the
159
<option>--connect</option> option is used, point-to-point
160
interfaces and non-broadcast interfaces are accepted.) If no
161
acceptable interfaces are found, re-run the check but without
162
the <quote>up and running</quote> requirement, and manually take
163
the selected interface up (and later take it down on program
167
Before a network interface is 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
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>
228
<term><option>--interface=<replaceable
229
>NAME</replaceable></option></term>
213
231
<replaceable>NAME</replaceable></option></term>
216
234
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>.
235
Mandos servers to connect to. The default is the empty
236
string, which will automatically choose an appropriate
240
If the <option>--connect</option> option is used, this
241
specifies the interface to use to connect to the address
245
Note that since this program will normally run in the
246
initial RAM disk environment, the interface must be an
247
interface which exists at that stage. Thus, the interface
248
can not be a pseudo-interface such as <quote>br0</quote>
249
or <quote>tun0</quote>; such interfaces will not exist
250
until much later in the boot process, and can not be used
251
by this program, unless created by a <quote>network
252
hook</quote> — see <xref linkend="network-hooks"/>.
255
<replaceable>NAME</replaceable> can be the string
256
<quote><literal>none</literal></quote>; this will not use
257
any specific interface, and will not bring up an interface
258
on startup. This is not recommended, and only meant for
448
<refsect1 id="network-hooks">
449
<title>NETWORK HOOKS</title>
451
If a network interface like a bridge or tunnel is required to
452
find a Mandos server, this requires the interface to be up and
453
running before <command>&COMMANDNAME;</command> starts looking
454
for Mandos servers. This can be accomplished by creating a
455
<quote>network hook</quote> program, and placing it in a special
459
Before the network is used (and again before program exit), any
460
runnable programs found in the network hook directory are run
461
with the argument <quote><literal>start</literal></quote> or
462
<quote><literal>stop</literal></quote>. This should bring up or
463
down, respectively, any network interface which
464
<command>&COMMANDNAME;</command> should use.
466
<refsect2 id="hook-requirements">
467
<title>REQUIREMENTS</title>
469
A network hook must be an executable file, and its name must
470
consist entirely of upper and lower case letters, digits,
471
underscores, periods, and hyphens.
474
A network hook will receive one argument, which can be one of
479
<term><literal>start</literal></term>
482
This should make the network hook create (if necessary)
483
and bring up a network interface.
488
<term><literal>stop</literal></term>
491
This should make the network hook take down a network
492
interface, and delete it if it did not exist previously.
497
<term><literal>files</literal></term>
500
This should make the network hook print, <emphasis>one
501
file per line</emphasis>, all the files needed for it to
502
run. (These files will be copied into the initial RAM
503
filesystem.) Typical use is for a network hook which is
504
a shell script to print its needed binaries.
507
It is not necessary to print any non-executable files
508
already in the network hook directory, these will be
509
copied implicitly if they otherwise satisfy the name
515
<term><literal>modules</literal></term>
518
This should make the network hook print, <emphasis>on
519
separate lines</emphasis>, all the kernel modules needed
520
for it to run. (These modules will be copied into the
521
initial RAM filesystem.) For instance, a tunnel
523
<quote><literal>tun</literal></quote> module.
529
The network hook will be provided with a number of environment
534
<term><envar>MANDOSNETHOOKDIR</envar></term>
537
The network hook directory, specified to
538
<command>&COMMANDNAME;</command> by the
539
<option>--network-hook-dir</option> option. Note: this
540
should <emphasis>always</emphasis> be used by the
541
network hook to refer to itself or any files in the hook
542
directory it may require.
547
<term><envar>DEVICE</envar></term>
550
The network interface, as specified to
551
<command>&COMMANDNAME;</command> by the
552
<option>--interface</option> option. If this is not the
553
interface a hook will bring up, there is no reason for a
559
<term><envar>MODE</envar></term>
562
This will be the same as the first argument;
563
i.e. <quote><literal>start</literal></quote>,
564
<quote><literal>stop</literal></quote>,
565
<quote><literal>files</literal></quote>, or
566
<quote><literal>modules</literal></quote>.
571
<term><envar>VERBOSITY</envar></term>
574
This will be the <quote><literal>1</literal></quote> if
575
the <option>--debug</option> option is passed to
576
<command>&COMMANDNAME;</command>, otherwise
577
<quote><literal>0</literal></quote>.
582
<term><envar>DELAY</envar></term>
585
This will be the same as the <option>--delay</option>
586
option passed to <command>&COMMANDNAME;</command>.
592
A hook may not read from standard input, and should be
593
restrictive in printing to standard output or standard error
594
unless <varname>VERBOSITY</varname> is
595
<quote><literal>1</literal></quote>.
600
<refsect1 id="files">
363
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<title>FILES</title>
604
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
606
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
610
OpenPGP public and private key files, in <quote>ASCII
611
Armor</quote> format. These are the default file names,
612
they can be changed with the <option>--pubkey</option> and
613
<option>--seckey</option> options.
619
class="directory">/lib/mandos/network-hooks.d</filename></term>
622
Directory where network hooks are located. Change this
623
with the <option>--network-hook-dir</option> option. See
624
<xref linkend="network-hooks"/>.
631
<!-- <refsect1 id="bugs"> -->
632
<!-- <title>BUGS</title> -->
374
637
<refsect1 id="example">
375
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<title>EXAMPLE</title>
640
Note that normally, command line options will not be given
641
directly, but via options for the Mandos <citerefentry
642
><refentrytitle>plugin-runner</refentrytitle>
643
<manvolnum>8mandos</manvolnum></citerefentry>.
647
Normal invocation needs no options, if the network interface
648
is <quote>eth0</quote>:
651
<userinput>&COMMANDNAME;</userinput>
656
Search for Mandos servers (and connect to them) using another
660
<!-- do not wrap this line -->
661
<userinput>&COMMANDNAME; --interface eth1</userinput>
666
Run in debug mode, and use a custom key:
670
<!-- do not wrap this line -->
671
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
677
Run in debug mode, with a custom key, and do not use Zeroconf
678
to locate a server; connect directly to the IPv6 link-local
679
address <quote><systemitem class="ipaddress"
680
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
681
using interface eth2:
685
<!-- do not wrap this line -->
686
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
380
692
<refsect1 id="security">
381
693
<title>SECURITY</title>
695
This program is set-uid to root, but will switch back to the
696
original (and presumably non-privileged) user and group after
697
bringing up the network interface.
700
To use this program for its intended purpose (see <xref
701
linkend="purpose"/>), the password for the root file system will
702
have to be given out to be stored in a server computer, after
703
having been encrypted using an OpenPGP key. This encrypted data
704
which will be stored in a server can only be decrypted by the
705
OpenPGP key, and the data will only be given out to those
706
clients who can prove they actually have that key. This key,
707
however, is stored unencrypted on the client side in its initial
708
<acronym>RAM</acronym> disk image file system. This is normally
709
readable by all, but this is normally fixed during installation
710
of this program; file permissions are set so that no-one is able
714
The only remaining weak point is that someone with physical
715
access to the client hard drive might turn off the client
716
computer, read the OpenPGP keys directly from the hard drive,
717
and communicate with the server. To safeguard against this, the
718
server is supposed to notice the client disappearing and stop
719
giving out the encrypted data. Therefore, it is important to
720
set the timeout and checker interval values tightly on the
721
server. See <citerefentry><refentrytitle
722
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
725
It will also help if the checker program on the server is
726
configured to request something from the client which can not be
727
spoofed by someone else on the network, unlike unencrypted
728
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
731
<emphasis>Note</emphasis>: This makes it completely insecure to
732
have <application >Mandos</application> clients which dual-boot
733
to another operating system which is <emphasis>not</emphasis>
734
trusted to keep the initial <acronym>RAM</acronym> disk image
386
739
<refsect1 id="see_also">
387
740
<title>SEE ALSO</title>
742
<citerefentry><refentrytitle>intro</refentrytitle>
743
<manvolnum>8mandos</manvolnum></citerefentry>,
744
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
745
<manvolnum>8</manvolnum></citerefentry>,
746
<citerefentry><refentrytitle>crypttab</refentrytitle>
747
<manvolnum>5</manvolnum></citerefentry>,
389
748
<citerefentry><refentrytitle>mandos</refentrytitle>
390
749
<manvolnum>8</manvolnum></citerefentry>,
391
750
<citerefentry><refentrytitle>password-prompt</refentrytitle>
393
752
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
394
753
<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>
758
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
762
Zeroconf is the network protocol standard used for finding
763
Mandos servers on the local network.
769
<ulink url="http://www.avahi.org/">Avahi</ulink>
773
Avahi is the library this program calls to find Zeroconf
780
<ulink url="http://www.gnu.org/software/gnutls/"
785
GnuTLS is the library this client uses to implement TLS for
786
communicating securely with the server, and at the same time
787
send the public OpenPGP key to the server.
793
<ulink url="http://www.gnupg.org/related_software/gpgme/"
798
GPGME is the library used to decrypt the OpenPGP data sent
805
RFC 4291: <citetitle>IP Version 6 Addressing
806
Architecture</citetitle>
811
<term>Section 2.2: <citetitle>Text Representation of
812
Addresses</citetitle></term>
813
<listitem><para/></listitem>
816
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
817
Address</citetitle></term>
818
<listitem><para/></listitem>
821
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
822
Addresses</citetitle></term>
825
This client uses IPv6 link-local addresses, which are
826
immediately usable since a link-local addresses is
827
automatically assigned to a network interfaces when it
837
RFC 4346: <citetitle>The Transport Layer Security (TLS)
838
Protocol Version 1.1</citetitle>
842
TLS 1.1 is the protocol implemented by GnuTLS.
848
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
852
The data received from the server is binary encrypted
859
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
864
This is implemented by GnuTLS and used by this program so
865
that OpenPGP keys can be used.
435
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