122
125
</refsynopsisdiv>
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127
<refsect1 id="description">
125
128
<title>DESCRIPTION</title>
127
<command>&COMMANDNAME;</command> is a mandos plugin that works
128
like a client program that through avahi detects mandos servers,
129
sets up a gnutls connect and request a encrypted password. Any
130
passwords given is automaticly decrypted and passed to
130
<command>&COMMANDNAME;</command> is a client program that
131
communicates with <citerefentry><refentrytitle
132
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
133
to get a password. In slightly more detail, this client program
134
brings up a network interface, uses the interface’s IPv6
135
link-local address to get network connectivity, uses Zeroconf to
136
find servers on the local network, and communicates with servers
137
using TLS with an OpenPGP key to ensure authenticity and
138
confidentiality. This client program keeps running, trying all
139
servers on the network, until it receives a satisfactory reply
140
or a TERM signal. After all servers have been tried, all
141
servers are periodically retried. If no servers are found it
142
will wait indefinitely for new servers to appear.
145
This program is not meant to be run directly; it is really meant
146
to run as a plugin of the <application>Mandos</application>
147
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
149
initial <acronym>RAM</acronym> disk environment because it is
150
specified as a <quote>keyscript</quote> in the <citerefentry>
151
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
152
</citerefentry> file.
156
<refsect1 id="purpose">
157
<title>PURPOSE</title>
159
The purpose of this is to enable <emphasis>remote and unattended
160
rebooting</emphasis> of client host computer with an
161
<emphasis>encrypted root file system</emphasis>. See <xref
162
linkend="overview"/> for details.
135
166
<refsect1 id="options">
136
167
<title>OPTIONS</title>
138
Commonly not invoked as command lines but from configuration
139
file of plugin runner.
169
This program is commonly not invoked from the command line; it
170
is normally started by the <application>Mandos</application>
171
plugin runner, see <citerefentry><refentrytitle
172
>plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
173
</citerefentry>. Any command line options this program accepts
174
are therefore normally provided by the plugin runner, and not
144
180
<term><option>--connect=<replaceable
145
>IPADDR</replaceable><literal>:</literal><replaceable
181
>ADDRESS</replaceable><literal>:</literal><replaceable
146
182
>PORT</replaceable></option></term>
148
<replaceable>IPADDR</replaceable><literal>:</literal
184
<replaceable>ADDRESS</replaceable><literal>:</literal
149
185
><replaceable>PORT</replaceable></option></term>
152
Connect directly to a specified mandos server
188
Do not use Zeroconf to locate servers. Connect directly
189
to only one specified <application>Mandos</application>
190
server. Note that an IPv6 address has colon characters in
191
it, so the <emphasis>last</emphasis> colon character is
192
assumed to separate the address from the port number.
158
<term><option>--keydir=<replaceable
159
>DIRECTORY</replaceable></option></term>
161
<replaceable>DIRECTORY</replaceable></option></term>
164
Directory where the openpgp keyring is
195
This option is normally only useful for testing and
170
<term><option>--interface=
171
<replaceable>NAME</replaceable></option></term>
202
<term><option>--interface=<replaceable
203
>NAME</replaceable></option></term>
173
205
<replaceable>NAME</replaceable></option></term>
176
Interface that Avahi will connect through
208
Network interface that will be brought up and scanned for
209
Mandos servers to connect to. The default is the empty
210
string, which will automatically choose an appropriate
214
If the <option>--connect</option> option is used, this
215
specifies the interface to use to connect to the address
219
Note that since this program will normally run in the
220
initial RAM disk environment, the interface must be an
221
interface which exists at that stage. Thus, the interface
222
can not be a pseudo-interface such as <quote>br0</quote>
223
or <quote>tun0</quote>; such interfaces will not exist
224
until much later in the boot process, and can not be used
228
<replaceable>NAME</replaceable> can be the string
229
<quote><literal>none</literal></quote>; this will not use
230
any specific interface, and will not bring up an interface
231
on startup. This is not recommended, and only meant for
182
238
<term><option>--pubkey=<replaceable
183
239
>FILE</replaceable></option></term>
206
266
<term><option>--priority=<replaceable
207
267
>STRING</replaceable></option></term>
269
<xi:include href="../mandos-options.xml"
270
xpointer="priority"/>
216
275
<term><option>--dh-bits=<replaceable
217
276
>BITS</replaceable></option></term>
220
DH bits to use in gnutls communication
279
Sets the number of bits to use for the prime number in the
280
TLS Diffie-Hellman key exchange. Default is 1024.
286
<term><option>--delay=<replaceable
287
>SECONDS</replaceable></option></term>
290
After bringing the network interface up, the program waits
291
for the interface to arrive in a <quote>running</quote>
292
state before proceeding. During this time, the kernel log
293
level will be lowered to reduce clutter on the system
294
console, alleviating any other plugins which might be
295
using the system console. This option sets the upper
296
limit of seconds to wait. The default is 2.5 seconds.
302
<term><option>--retry=<replaceable
303
>SECONDS</replaceable></option></term>
306
All Mandos servers are tried repeatedly until a password
307
is received. This value specifies, in seconds, how long
308
between each successive try <emphasis>for the same
309
server</emphasis>. The default is 10 seconds.
245
341
<term><option>--usage</option></term>
248
Gives a short usage message
344
Gives a short usage message.
254
350
<term><option>--version</option></term>
255
351
<term><option>-V</option></term>
258
Prints the program version
354
Prints the program version.
361
<refsect1 id="overview">
362
<title>OVERVIEW</title>
363
<xi:include href="../overview.xml"/>
365
This program is the client part. It is a plugin started by
366
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
367
<manvolnum>8mandos</manvolnum></citerefentry> which will run in
368
an initial <acronym>RAM</acronym> disk environment.
371
This program could, theoretically, be used as a keyscript in
372
<filename>/etc/crypttab</filename>, but it would then be
373
impossible to enter a password for the encrypted root disk at
374
the console, since this program does not read from the console
375
at all. This is why a separate plugin runner (<citerefentry>
376
<refentrytitle>plugin-runner</refentrytitle>
377
<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
378
both this program and others in in parallel,
379
<emphasis>one</emphasis> of which will prompt for passwords on
265
384
<refsect1 id="exit_status">
266
385
<title>EXIT STATUS</title>
387
This program will exit with a successful (zero) exit status if a
388
server could be found and the password received from it could be
389
successfully decrypted and output on standard output. The
390
program will exit with a non-zero exit status only if a critical
391
error occurs. Otherwise, it will forever connect to any
392
discovered <application>Mandos</application> servers, trying to
393
get a decryptable password and print it.
271
397
<refsect1 id="environment">
272
398
<title>ENVIRONMENT</title>
400
This program does not use any environment variables, not even
401
the ones provided by <citerefentry><refentrytitle
402
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
407
<refsect1 id="files">
278
408
<title>FILES</title>
411
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
413
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
417
OpenPGP public and private key files, in <quote>ASCII
418
Armor</quote> format. These are the default file names,
419
they can be changed with the <option>--pubkey</option> and
420
<option>--seckey</option> options.
427
<!-- <refsect1 id="bugs"> -->
428
<!-- <title>BUGS</title> -->
289
433
<refsect1 id="example">
290
434
<title>EXAMPLE</title>
436
Note that normally, command line options will not be given
437
directly, but via options for the Mandos <citerefentry
438
><refentrytitle>plugin-runner</refentrytitle>
439
<manvolnum>8mandos</manvolnum></citerefentry>.
443
Normal invocation needs no options, if the network interface
444
is <quote>eth0</quote>:
447
<userinput>&COMMANDNAME;</userinput>
452
Search for Mandos servers (and connect to them) using another
456
<!-- do not wrap this line -->
457
<userinput>&COMMANDNAME; --interface eth1</userinput>
462
Run in debug mode, and use a custom key:
466
<!-- do not wrap this line -->
467
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
473
Run in debug mode, with a custom key, and do not use Zeroconf
474
to locate a server; connect directly to the IPv6 link-local
475
address <quote><systemitem class="ipaddress"
476
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
477
using interface eth2:
481
<!-- do not wrap this line -->
482
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
295
488
<refsect1 id="security">
296
489
<title>SECURITY</title>
491
This program is set-uid to root, but will switch back to the
492
original (and presumably non-privileged) user and group after
493
bringing up the network interface.
496
To use this program for its intended purpose (see <xref
497
linkend="purpose"/>), the password for the root file system will
498
have to be given out to be stored in a server computer, after
499
having been encrypted using an OpenPGP key. This encrypted data
500
which will be stored in a server can only be decrypted by the
501
OpenPGP key, and the data will only be given out to those
502
clients who can prove they actually have that key. This key,
503
however, is stored unencrypted on the client side in its initial
504
<acronym>RAM</acronym> disk image file system. This is normally
505
readable by all, but this is normally fixed during installation
506
of this program; file permissions are set so that no-one is able
510
The only remaining weak point is that someone with physical
511
access to the client hard drive might turn off the client
512
computer, read the OpenPGP keys directly from the hard drive,
513
and communicate with the server. To safeguard against this, the
514
server is supposed to notice the client disappearing and stop
515
giving out the encrypted data. Therefore, it is important to
516
set the timeout and checker interval values tightly on the
517
server. See <citerefentry><refentrytitle
518
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
521
It will also help if the checker program on the server is
522
configured to request something from the client which can not be
523
spoofed by someone else on the network, unlike unencrypted
524
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
527
<emphasis>Note</emphasis>: This makes it completely insecure to
528
have <application >Mandos</application> clients which dual-boot
529
to another operating system which is <emphasis>not</emphasis>
530
trusted to keep the initial <acronym>RAM</acronym> disk image
301
535
<refsect1 id="see_also">
302
536
<title>SEE ALSO</title>
538
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
539
<manvolnum>8</manvolnum></citerefentry>,
540
<citerefentry><refentrytitle>crypttab</refentrytitle>
541
<manvolnum>5</manvolnum></citerefentry>,
304
542
<citerefentry><refentrytitle>mandos</refentrytitle>
305
543
<manvolnum>8</manvolnum></citerefentry>,
306
544
<citerefentry><refentrytitle>password-prompt</refentrytitle>
308
546
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
309
547
<manvolnum>8mandos</manvolnum></citerefentry>
313
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
317
<ulink url="http://www.avahi.org/">Avahi</ulink>
322
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
327
url="http://www.gnupg.org/related_software/gpgme/">
332
<citation>RFC 4880: <citetitle>OpenPGP Message
333
Format</citetitle></citation>
337
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
338
Transport Layer Security</citetitle></citation>
342
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
343
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
344
Unicast Addresses</citation>
552
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
556
Zeroconf is the network protocol standard used for finding
557
Mandos servers on the local network.
563
<ulink url="http://www.avahi.org/">Avahi</ulink>
567
Avahi is the library this program calls to find Zeroconf
574
<ulink url="http://www.gnu.org/software/gnutls/"
579
GnuTLS is the library this client uses to implement TLS for
580
communicating securely with the server, and at the same time
581
send the public OpenPGP key to the server.
587
<ulink url="http://www.gnupg.org/related_software/gpgme/"
592
GPGME is the library used to decrypt the OpenPGP data sent
599
RFC 4291: <citetitle>IP Version 6 Addressing
600
Architecture</citetitle>
605
<term>Section 2.2: <citetitle>Text Representation of
606
Addresses</citetitle></term>
607
<listitem><para/></listitem>
610
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
611
Address</citetitle></term>
612
<listitem><para/></listitem>
615
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
616
Addresses</citetitle></term>
619
This client uses IPv6 link-local addresses, which are
620
immediately usable since a link-local addresses is
621
automatically assigned to a network interfaces when it
631
RFC 4346: <citetitle>The Transport Layer Security (TLS)
632
Protocol Version 1.1</citetitle>
636
TLS 1.1 is the protocol implemented by GnuTLS.
642
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
646
The data received from the server is binary encrypted
653
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
658
This is implemented by GnuTLS and used by this program so
659
that OpenPGP keys can be used.
350
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<!-- Local Variables: -->
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<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
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<!-- time-stamp-end: "[\"']>" -->