122
134
</refsynopsisdiv>
124
136
<refsect1 id="description">
125
137
<title>DESCRIPTION</title>
127
139
<command>&COMMANDNAME;</command> is a client program that
128
140
communicates with <citerefentry><refentrytitle
129
141
>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.
142
to get a password. In slightly more detail, this client program
143
brings up network interfaces, uses the interfaces’ IPv6
144
link-local addresses to get network connectivity, uses Zeroconf
145
to find servers on the local network, and communicates with
146
servers using TLS with an OpenPGP key to ensure authenticity and
147
confidentiality. This client program keeps running, trying all
148
servers on the network, until it receives a satisfactory reply
149
or a TERM signal. After all servers have been tried, all
150
servers are periodically retried. If no servers are found it
151
will wait indefinitely for new servers to appear.
154
The network interfaces are selected like this: If any interfaces
155
are specified using the <option>--interface</option> option,
156
those interface are used. Otherwise,
157
<command>&COMMANDNAME;</command> will use all interfaces that
158
are not loopback interfaces, are not point-to-point interfaces,
159
are capable of broadcasting and do not have the NOARP flag (see
160
<citerefentry><refentrytitle>netdevice</refentrytitle>
161
<manvolnum>7</manvolnum></citerefentry>). (If the
162
<option>--connect</option> option is used, point-to-point
163
interfaces and non-broadcast interfaces are accepted.) If any
164
used interfaces are not up and running, they are first taken up
165
(and later taken down again on program exit).
168
Before network interfaces are selected, all <quote>network
169
hooks</quote> are run; see <xref linkend="network-hooks"/>.
137
172
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>
229
<term><option>--interface=<replaceable
230
>NAME</replaceable><arg rep='repeat'>,<replaceable
231
>NAME</replaceable></arg></option></term>
213
<replaceable>NAME</replaceable></option></term>
233
<replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
234
>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>.
237
Comma separated list of network interfaces that will be
238
brought up and scanned for Mandos servers to connect to.
239
The default is the empty string, which will automatically
240
use all appropriate interfaces.
243
If the <option>--connect</option> option is used, and
244
exactly one interface name is specified (except
245
<quote><literal>none</literal></quote>), this specifies
246
the interface to use to connect to the address given.
249
Note that since this program will normally run in the
250
initial RAM disk environment, the interface must be an
251
interface which exists at that stage. Thus, the interface
252
can normally not be a pseudo-interface such as
253
<quote>br0</quote> or <quote>tun0</quote>; such interfaces
254
will not exist until much later in the boot process, and
255
can not be used by this program, unless created by a
256
<quote>network hook</quote> — see <xref
257
linkend="network-hooks"/>.
260
<replaceable>NAME</replaceable> can be the string
261
<quote><literal>none</literal></quote>; this will make
262
<command>&COMMANDNAME;</command> not bring up
263
<emphasis>any</emphasis> interfaces specified
264
<emphasis>after</emphasis> this string. This is not
265
recommended, and only meant for advanced users.
454
<refsect1 id="network-hooks">
455
<title>NETWORK HOOKS</title>
457
If a network interface like a bridge or tunnel is required to
458
find a Mandos server, this requires the interface to be up and
459
running before <command>&COMMANDNAME;</command> starts looking
460
for Mandos servers. This can be accomplished by creating a
461
<quote>network hook</quote> program, and placing it in a special
465
Before the network is used (and again before program exit), any
466
runnable programs found in the network hook directory are run
467
with the argument <quote><literal>start</literal></quote> or
468
<quote><literal>stop</literal></quote>. This should bring up or
469
down, respectively, any network interface which
470
<command>&COMMANDNAME;</command> should use.
472
<refsect2 id="hook-requirements">
473
<title>REQUIREMENTS</title>
475
A network hook must be an executable file, and its name must
476
consist entirely of upper and lower case letters, digits,
477
underscores, periods, and hyphens.
480
A network hook will receive one argument, which can be one of
485
<term><literal>start</literal></term>
488
This should make the network hook create (if necessary)
489
and bring up a network interface.
494
<term><literal>stop</literal></term>
497
This should make the network hook take down a network
498
interface, and delete it if it did not exist previously.
503
<term><literal>files</literal></term>
506
This should make the network hook print, <emphasis>one
507
file per line</emphasis>, all the files needed for it to
508
run. (These files will be copied into the initial RAM
509
filesystem.) Typical use is for a network hook which is
510
a shell script to print its needed binaries.
513
It is not necessary to print any non-executable files
514
already in the network hook directory, these will be
515
copied implicitly if they otherwise satisfy the name
521
<term><literal>modules</literal></term>
524
This should make the network hook print, <emphasis>on
525
separate lines</emphasis>, all the kernel modules needed
526
for it to run. (These modules will be copied into the
527
initial RAM filesystem.) For instance, a tunnel
529
<quote><literal>tun</literal></quote> module.
535
The network hook will be provided with a number of environment
540
<term><envar>MANDOSNETHOOKDIR</envar></term>
543
The network hook directory, specified to
544
<command>&COMMANDNAME;</command> by the
545
<option>--network-hook-dir</option> option. Note: this
546
should <emphasis>always</emphasis> be used by the
547
network hook to refer to itself or any files in the hook
548
directory it may require.
553
<term><envar>DEVICE</envar></term>
556
The network interfaces, as specified to
557
<command>&COMMANDNAME;</command> by the
558
<option>--interface</option> option, combined to one
559
string and separated by commas. If this is set, and
560
does not contain the interface a hook will bring up,
561
there is no reason for a hook to continue.
566
<term><envar>MODE</envar></term>
569
This will be the same as the first argument;
570
i.e. <quote><literal>start</literal></quote>,
571
<quote><literal>stop</literal></quote>,
572
<quote><literal>files</literal></quote>, or
573
<quote><literal>modules</literal></quote>.
578
<term><envar>VERBOSITY</envar></term>
581
This will be the <quote><literal>1</literal></quote> if
582
the <option>--debug</option> option is passed to
583
<command>&COMMANDNAME;</command>, otherwise
584
<quote><literal>0</literal></quote>.
589
<term><envar>DELAY</envar></term>
592
This will be the same as the <option>--delay</option>
593
option passed to <command>&COMMANDNAME;</command>. Is
594
only set if <envar>MODE</envar> is
595
<quote><literal>start</literal></quote> or
596
<quote><literal>stop</literal></quote>.
601
<term><envar>CONNECT</envar></term>
604
This will be the same as the <option>--connect</option>
605
option passed to <command>&COMMANDNAME;</command>. Is
606
only set if <option>--connect</option> is passed and
607
<envar>MODE</envar> is
608
<quote><literal>start</literal></quote> or
609
<quote><literal>stop</literal></quote>.
615
A hook may not read from standard input, and should be
616
restrictive in printing to standard output or standard error
617
unless <varname>VERBOSITY</varname> is
618
<quote><literal>1</literal></quote>.
623
<refsect1 id="files">
363
624
<title>FILES</title>
627
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
629
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
633
OpenPGP public and private key files, in <quote>ASCII
634
Armor</quote> format. These are the default file names,
635
they can be changed with the <option>--pubkey</option> and
636
<option>--seckey</option> options.
642
class="directory">/lib/mandos/network-hooks.d</filename></term>
645
Directory where network hooks are located. Change this
646
with the <option>--network-hook-dir</option> option. See
647
<xref linkend="network-hooks"/>.
654
<!-- <refsect1 id="bugs"> -->
655
<!-- <title>BUGS</title> -->
374
660
<refsect1 id="example">
375
661
<title>EXAMPLE</title>
663
Note that normally, command line options will not be given
664
directly, but via options for the Mandos <citerefentry
665
><refentrytitle>plugin-runner</refentrytitle>
666
<manvolnum>8mandos</manvolnum></citerefentry>.
670
Normal invocation needs no options, if the network interfaces
671
can be automatically determined:
674
<userinput>&COMMANDNAME;</userinput>
679
Search for Mandos servers (and connect to them) using one
683
<!-- do not wrap this line -->
684
<userinput>&COMMANDNAME; --interface eth1</userinput>
689
Run in debug mode, and use a custom key:
693
<!-- do not wrap this line -->
694
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
700
Run in debug mode, with a custom key, and do not use Zeroconf
701
to locate a server; connect directly to the IPv6 link-local
702
address <quote><systemitem class="ipaddress"
703
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
704
using interface eth2:
708
<!-- do not wrap this line -->
709
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
380
715
<refsect1 id="security">
381
716
<title>SECURITY</title>
718
This program is set-uid to root, but will switch back to the
719
original (and presumably non-privileged) user and group after
720
bringing up the network interface.
723
To use this program for its intended purpose (see <xref
724
linkend="purpose"/>), the password for the root file system will
725
have to be given out to be stored in a server computer, after
726
having been encrypted using an OpenPGP key. This encrypted data
727
which will be stored in a server can only be decrypted by the
728
OpenPGP key, and the data will only be given out to those
729
clients who can prove they actually have that key. This key,
730
however, is stored unencrypted on the client side in its initial
731
<acronym>RAM</acronym> disk image file system. This is normally
732
readable by all, but this is normally fixed during installation
733
of this program; file permissions are set so that no-one is able
737
The only remaining weak point is that someone with physical
738
access to the client hard drive might turn off the client
739
computer, read the OpenPGP keys directly from the hard drive,
740
and communicate with the server. To safeguard against this, the
741
server is supposed to notice the client disappearing and stop
742
giving out the encrypted data. Therefore, it is important to
743
set the timeout and checker interval values tightly on the
744
server. See <citerefentry><refentrytitle
745
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
748
It will also help if the checker program on the server is
749
configured to request something from the client which can not be
750
spoofed by someone else on the network, unlike unencrypted
751
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
754
<emphasis>Note</emphasis>: This makes it completely insecure to
755
have <application >Mandos</application> clients which dual-boot
756
to another operating system which is <emphasis>not</emphasis>
757
trusted to keep the initial <acronym>RAM</acronym> disk image
386
762
<refsect1 id="see_also">
387
763
<title>SEE ALSO</title>
765
<citerefentry><refentrytitle>intro</refentrytitle>
766
<manvolnum>8mandos</manvolnum></citerefentry>,
767
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
768
<manvolnum>8</manvolnum></citerefentry>,
769
<citerefentry><refentrytitle>crypttab</refentrytitle>
770
<manvolnum>5</manvolnum></citerefentry>,
389
771
<citerefentry><refentrytitle>mandos</refentrytitle>
390
772
<manvolnum>8</manvolnum></citerefentry>,
391
773
<citerefentry><refentrytitle>password-prompt</refentrytitle>
393
775
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
394
776
<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>
781
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
785
Zeroconf is the network protocol standard used for finding
786
Mandos servers on the local network.
792
<ulink url="http://www.avahi.org/">Avahi</ulink>
796
Avahi is the library this program calls to find Zeroconf
803
<ulink url="http://www.gnu.org/software/gnutls/"
808
GnuTLS is the library this client uses to implement TLS for
809
communicating securely with the server, and at the same time
810
send the public OpenPGP key to the server.
816
<ulink url="http://www.gnupg.org/related_software/gpgme/"
821
GPGME is the library used to decrypt the OpenPGP data sent
828
RFC 4291: <citetitle>IP Version 6 Addressing
829
Architecture</citetitle>
834
<term>Section 2.2: <citetitle>Text Representation of
835
Addresses</citetitle></term>
836
<listitem><para/></listitem>
839
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
840
Address</citetitle></term>
841
<listitem><para/></listitem>
844
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
845
Addresses</citetitle></term>
848
This client uses IPv6 link-local addresses, which are
849
immediately usable since a link-local addresses is
850
automatically assigned to a network interface when it
860
RFC 4346: <citetitle>The Transport Layer Security (TLS)
861
Protocol Version 1.1</citetitle>
865
TLS 1.1 is the protocol implemented by GnuTLS.
871
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
875
The data received from the server is binary encrypted
882
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
887
This is implemented by GnuTLS and used by this program so
888
that OpenPGP keys can be used.
435
896
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