147
117
<refsect1 id="description">
148
118
<title>DESCRIPTION</title>
150
<command>&COMMANDNAME;</command> is a mandos plugin that works
151
like a client program that through avahi detects mandos servers,
152
sets up a gnutls connect and request a encrypted password. Any
153
passwords given is automaticly decrypted and passed to
120
<command>&COMMANDNAME;</command> is a client program that
121
communicates with <citerefentry><refentrytitle
122
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
123
to get a password. It uses IPv6 link-local addresses to get
124
network connectivity, Zeroconf to find servers, and TLS with an
125
OpenPGP key to ensure authenticity and confidentiality. It
126
keeps running, trying all servers on the network, until it
127
receives a satisfactory reply or a TERM signal is received.
130
This program is not meant to be run directly; it is really meant
131
to run as a plugin of the <application>Mandos</application>
132
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
133
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
134
initial <acronym>RAM</acronym> disk environment because it is
135
specified as a <quote>keyscript</quote> in the <citerefentry>
136
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
137
</citerefentry> file.
141
<refsect1 id="purpose">
142
<title>PURPOSE</title>
144
The purpose of this is to enable <emphasis>remote and unattended
145
rebooting</emphasis> of client host computer with an
146
<emphasis>encrypted root file system</emphasis>. See <xref
147
linkend="overview"/> for details.
158
151
<refsect1 id="options">
159
152
<title>OPTIONS</title>
161
Commonly not invoked as command lines but from configuration
162
file of plugin runner.
154
This program is commonly not invoked from the command line; it
155
is normally started by the <application>Mandos</application>
156
plugin runner, see <citerefentry><refentrytitle
157
>plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
158
</citerefentry>. Any command line options this program accepts
159
are therefore normally provided by the plugin runner, and not
167
<term><literal>-c</literal>, <literal>--connect=<replaceable>
168
IP</replaceable></literal></term>
171
Connect directly to a specified mandos server
177
<term><literal>-d</literal>, <literal>--keydir=<replaceable>
178
KEYDIR</replaceable></literal></term>
181
Directory where the openpgp keyring is
187
<term><literal>-i</literal>, <literal>--interface=
188
<replaceable>INTERFACE</replaceable></literal></term>
191
Interface that Avahi will conntect through
197
<term><literal>-p</literal>, <literal>--pubkey=<replaceable>
198
PUBKEY</replaceable></literal></term>
201
Public openpgp key for gnutls authentication
207
<term><literal>-s</literal>, <literal>--seckey=<replaceable>
208
SECKEY</replaceable></literal></term>
211
Secret openpgp key for gnutls authentication
217
<term><literal>--priority=<replaceable>PRIORITY</replaceable>
227
<term><literal>--dh-bits=<replaceable>BITS</replaceable>
231
dh-bits to use in gnutls communication
237
<term><literal>--debug</literal></term>
246
<term><literal>-?</literal>, <literal>--help</literal></term>
255
<term><literal>--usage</literal></term>
258
Gives a short usage message
264
<term><literal>-V</literal>, <literal>--version</literal></term>
267
Prints the program version
165
<term><option>--connect=<replaceable
166
>ADDRESS</replaceable><literal>:</literal><replaceable
167
>PORT</replaceable></option></term>
169
<replaceable>ADDRESS</replaceable><literal>:</literal
170
><replaceable>PORT</replaceable></option></term>
173
Do not use Zeroconf to locate servers. Connect directly
174
to only one specified <application>Mandos</application>
175
server. Note that an IPv6 address has colon characters in
176
it, so the <emphasis>last</emphasis> colon character is
177
assumed to separate the address from the port number.
180
This option is normally only useful for testing and
187
<term><option>--interface=
188
<replaceable>NAME</replaceable></option></term>
190
<replaceable>NAME</replaceable></option></term>
193
Network interface that will be brought up and scanned for
194
Mandos servers to connect to. The default it
195
<quote><literal>eth0</literal></quote>.
198
If the <option>--connect</option> option is used, this
199
specifies the interface to use to connect to the address
206
<term><option>--pubkey=<replaceable
207
>FILE</replaceable></option></term>
209
<replaceable>FILE</replaceable></option></term>
212
OpenPGP public key file name. The default name is
213
<quote><filename>/conf/conf.d/mandos/pubkey.txt</filename
220
<term><option>--seckey=<replaceable
221
>FILE</replaceable></option></term>
223
<replaceable>FILE</replaceable></option></term>
226
OpenPGP secret key file name. The default name is
227
<quote><filename>/conf/conf.d/mandos/seckey.txt</filename
234
<term><option>--priority=<replaceable
235
>STRING</replaceable></option></term>
237
<xi:include href="../mandos-options.xml"
238
xpointer="priority"/>
243
<term><option>--dh-bits=<replaceable
244
>BITS</replaceable></option></term>
247
Sets the number of bits to use for the prime number in the
248
TLS Diffie-Hellman key exchange. Default is 1024.
254
<term><option>--debug</option></term>
257
Enable debug mode. This will enable a lot of output to
258
standard error about what the program is doing. The
259
program will still perform all other functions normally.
262
It will also enable debug mode in the Avahi and GnuTLS
263
libraries, making them print large amounts of debugging
270
<term><option>--help</option></term>
271
<term><option>-?</option></term>
274
Gives a help message about options and their meanings.
280
<term><option>--usage</option></term>
283
Gives a short usage message.
289
<term><option>--version</option></term>
290
<term><option>-V</option></term>
293
Prints the program version.
300
<refsect1 id="overview">
301
<title>OVERVIEW</title>
302
<xi:include href="../overview.xml"/>
304
This program is the client part. It is a plugin started by
305
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
306
<manvolnum>8mandos</manvolnum></citerefentry> which will run in
307
an initial <acronym>RAM</acronym> disk environment.
310
This program could, theoretically, be used as a keyscript in
311
<filename>/etc/crypttab</filename>, but it would then be
312
impossible to enter a password for the encrypted root disk at
313
the console, since this program does not read from the console
314
at all. This is why a separate plugin (<citerefentry>
315
<refentrytitle>password-prompt</refentrytitle>
316
<manvolnum>8mandos</manvolnum></citerefentry>) does that, which
317
will be run in parallel to this one by the plugin runner.
274
321
<refsect1 id="exit_status">
275
322
<title>EXIT STATUS</title>
324
This program will exit with a successful (zero) exit status if a
325
server could be found and the password received from it could be
326
successfully decrypted and output on standard output. The
327
program will exit with a non-zero exit status only if a critical
328
error occurs. Otherwise, it will forever connect to new
329
<application>Mandos</application> servers as they appear, trying
330
to get a decryptable password.
280
334
<refsect1 id="environment">
281
335
<title>ENVIRONMENT</title>
337
This program does not use any environment variables, not even
338
the ones provided by <citerefentry><refentrytitle
339
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
286
344
<refsect1 id="file">
287
345
<title>FILES</title>
348
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
350
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
354
OpenPGP public and private key files, in <quote>ASCII
355
Armor</quote> format. These are the default file names,
356
they can be changed with the <option>--pubkey</option> and
357
<option>--seckey</option> options.
364
<!-- <refsect1 id="bugs"> -->
365
<!-- <title>BUGS</title> -->
298
370
<refsect1 id="example">
299
371
<title>EXAMPLE</title>
373
Note that normally, command line options will not be given
374
directly, but via options for the Mandos <citerefentry
375
><refentrytitle>plugin-runner</refentrytitle>
376
<manvolnum>8mandos</manvolnum></citerefentry>.
380
Normal invocation needs no options, if the network interface
381
is <quote>eth0</quote>:
384
<userinput>&COMMANDNAME;</userinput>
389
Search for Mandos servers (and connect to them) using another
393
<!-- do not wrap this line -->
394
<userinput>&COMMANDNAME; --interface eth1</userinput>
399
Run in debug mode, and use a custom key:
403
<!-- do not wrap this line -->
404
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
410
Run in debug mode, with a custom key, and do not use Zeroconf
411
to locate a server; connect directly to the IPv6 address
412
<quote><systemitem class="ipaddress"
413
>2001:db8:f983:bd0b:30de:ae4a:71f2:f672</systemitem></quote>,
414
port 4711, using interface eth2:
418
<!-- do not wrap this line -->
419
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>
304
425
<refsect1 id="security">
305
426
<title>SECURITY</title>
428
This program is set-uid to root, but will switch back to the
429
original (and presumably non-privileged) user and group after
430
bringing up the network interface.
433
To use this program for its intended purpose (see <xref
434
linkend="purpose"/>), the password for the root file system will
435
have to be given out to be stored in a server computer, after
436
having been encrypted using an OpenPGP key. This encrypted data
437
which will be stored in a server can only be decrypted by the
438
OpenPGP key, and the data will only be given out to those
439
clients who can prove they actually have that key. This key,
440
however, is stored unencrypted on the client side in its initial
441
<acronym>RAM</acronym> disk image file system. This is normally
442
readable by all, but this is normally fixed during installation
443
of this program; file permissions are set so that no-one is able
447
The only remaining weak point is that someone with physical
448
access to the client hard drive might turn off the client
449
computer, read the OpenPGP keys directly from the hard drive,
450
and communicate with the server. The defense against this is
451
that the server is supposed to notice the client disappearing
452
and will stop giving out the encrypted data. Therefore, it is
453
important to set the timeout and checker interval values tightly
454
on the server. See <citerefentry><refentrytitle
455
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
458
It will also help if the checker program on the server is
459
configured to request something from the client which can not be
460
spoofed by someone else on the network, unlike unencrypted
461
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
464
<emphasis>Note</emphasis>: This makes it completely insecure to
465
have <application >Mandos</application> clients which dual-boot
466
to another operating system which is <emphasis>not</emphasis>
467
trusted to keep the initial <acronym>RAM</acronym> disk image
310
472
<refsect1 id="see_also">
311
473
<title>SEE ALSO</title>
475
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
476
<manvolnum>8</manvolnum></citerefentry>,
477
<citerefentry><refentrytitle>crypttab</refentrytitle>
478
<manvolnum>5</manvolnum></citerefentry>,
313
479
<citerefentry><refentrytitle>mandos</refentrytitle>
314
480
<manvolnum>8</manvolnum></citerefentry>,
315
481
<citerefentry><refentrytitle>password-prompt</refentrytitle>
317
483
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
318
484
<manvolnum>8mandos</manvolnum></citerefentry>
322
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
326
<ulink url="http://www.avahi.org/">Avahi</ulink>
331
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
336
url="http://www.gnupg.org/related_software/gpgme/">
341
<citation>RFC 4880: <citetitle>OpenPGP Message
342
Format</citetitle></citation>
346
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
347
Transport Layer Security</citetitle></citation>
351
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
352
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
353
Unicast Addresses</citation>
489
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
493
Zeroconf is the network protocol standard used for finding
494
Mandos servers on the local network.
500
<ulink url="http://www.avahi.org/">Avahi</ulink>
504
Avahi is the library this program calls to find Zeroconf
511
<ulink url="http://www.gnu.org/software/gnutls/"
516
GnuTLS is the library this client uses to implement TLS for
517
communicating securely with the server, and at the same time
518
send the public OpenPGP key to the server.
524
<ulink url="http://www.gnupg.org/related_software/gpgme/"
529
GPGME is the library used to decrypt the OpenPGP data sent
536
RFC 4291: <citetitle>IP Version 6 Addressing
537
Architecture</citetitle>
542
<term>Section 2.2: <citetitle>Text Representation of
543
Addresses</citetitle></term>
544
<listitem><para/></listitem>
547
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
548
Address</citetitle></term>
549
<listitem><para/></listitem>
552
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
553
Addresses</citetitle></term>
556
This client uses IPv6 link-local addresses, which are
557
immediately usable since a link-local addresses is
558
automatically assigned to a network interfaces when it
568
RFC 4346: <citetitle>The Transport Layer Security (TLS)
569
Protocol Version 1.1</citetitle>
573
TLS 1.1 is the protocol implemented by GnuTLS.
579
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
583
The data received from the server is binary encrypted
590
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
595
This is implemented by GnuTLS and used by this program so
596
that OpenPGP keys can be used.