67
67
<refname><command>&COMMANDNAME;</command></refname>
69
Sends encrypted passwords to authenticated mandos clients
69
Sends encrypted passwords to authenticated Mandos clients
75
75
<command>&COMMANDNAME;</command>
76
<arg choice='opt' rep='repeat'>OPTION</arg>
76
<arg>--interface<arg choice="plain">IF</arg></arg>
77
<arg>--address<arg choice="plain">ADDRESS</arg></arg>
78
<arg>--port<arg choice="plain">PORT</arg></arg>
79
<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
80
<arg>--servicename<arg choice="plain">NAME</arg></arg>
81
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
85
<command>&COMMANDNAME;</command>
86
<arg>-i<arg choice="plain">IF</arg></arg>
87
<arg>-a<arg choice="plain">ADDRESS</arg></arg>
88
<arg>-p<arg choice="plain">PORT</arg></arg>
89
<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
90
<arg>--servicename<arg choice="plain">NAME</arg></arg>
91
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
95
<command>&COMMANDNAME;</command>
97
<arg choice="plain">-h</arg>
98
<arg choice="plain">--help</arg>
102
<command>&COMMANDNAME;</command>
103
<arg choice="plain">--version</arg>
106
<command>&COMMANDNAME;</command>
107
<arg choice="plain">--check</arg>
80
111
<refsect1 id="description">
81
112
<title>DESCRIPTION</title>
83
<command>&COMMANDNAME;</command> is a server daemon that handels
84
incomming passwords request for passwords. Mandos use avahi to
85
announce the service, and through gnutls authenticates
86
clients. Any authenticated client is then given its encrypted
114
<command>&COMMANDNAME;</command> is a server daemon which
115
handles incoming request for passwords for a pre-defined list of
116
client host computers. The Mandos server uses Zeroconf to
117
announce itself on the local network, and uses TLS to
118
communicate securely with and to authenticate the clients. The
119
Mandos server uses IPv6 to allow Mandos clients to use IPv6
120
link-local addresses, since the clients will probably not have
121
any other addresses configured (see <xref linkend="overview"/>).
122
Any authenticated client is then given the stored pre-encrypted
123
password for that specific client.
128
<refsect1 id="purpose">
129
<title>PURPOSE</title>
132
The purpose of this is to enable <emphasis>remote and unattended
133
rebooting</emphasis> of client host computer with an
134
<emphasis>encrypted root file system</emphasis>. See <xref
135
linkend="overview"/> for details.
140
<refsect1 id="options">
141
<title>OPTIONS</title>
92
145
<term><literal>-h</literal>, <literal>--help</literal></term>
95
show a help message and exit
148
Show a help message and exit
150
219
PRIORITY</replaceable></literal></term>
153
GnuTLS priority string. See <citerefentry>
154
<refentrytitle>gnutls_priority_init</refentrytitle>
155
<manvolnum>3</manvolnum></citerefentry>
222
GnuTLS priority string for the TLS handshake with the
223
clients. The default is
224
<quote><literal>SECURE256:!CTYPE-X.509:+CTYPE-OPENPGP</literal></quote>.
225
See <citerefentry><refentrytitle>gnutls_priority_init
226
</refentrytitle><manvolnum>3</manvolnum></citerefentry>
227
for the syntax. <emphasis>Warning</emphasis>: changing
228
this may make the TLS handshake fail, making communication
229
with clients impossible.
161
235
<term><literal>--servicename <replaceable>NAME</replaceable>
162
236
</literal></term>
165
Zeroconf service name
239
Zeroconf service name. The default is
240
<quote><literal>Mandos</literal></quote>. This only needs
241
to be changed this if it, for some reason, is necessary to
242
run more than one server on the same
243
<emphasis>host</emphasis>, which would not normally be
244
useful. If there are name collisions on the same
245
<emphasis>network</emphasis>, the newer server will
246
automatically rename itself to <quote><literal>Mandos
247
#2</literal></quote>, and so on; therefore, this option is
248
not needed in that case.
171
254
<term><literal>--configdir <replaceable>DIR</replaceable>
172
255
</literal></term>
175
Directory to search for configuration files
258
Directory to search for configuration files. Default is
259
<quote><literal>/etc/mandos</literal></quote>. See
260
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
261
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
262
<refentrytitle>mandos-clients.conf</refentrytitle>
263
<manvolnum>5</manvolnum></citerefentry>.
269
<term><literal>--version</literal></term>
272
Prints the program version and exit.
279
<refsect1 id="overview">
280
<title>OVERVIEW</title>
283
This program is the server part. It is a normal server program
284
and will run in a normal system environment, not in an initial
285
RAM disk environment.
289
<refsect1 id="protocol">
290
<title>NETWORK PROTOCOL</title>
292
The Mandos server announces itself as a Zeroconf service of type
293
<quote><literal>_mandos._tcp</literal></quote>. The Mandos
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client connects to the announced address and port, and sends a
295
line of text where the first whitespace-separated field is the
296
protocol version, which currently is
297
<quote><literal>1</literal></quote>. The client and server then
298
start a TLS protocol handshake with a slight quirk: the Mandos
299
server program acts as a TLS <quote>client</quote> while the
300
connecting Mandos client acts as a TLS <quote>server</quote>.
301
The Mandos client must supply an OpenPGP certificate, and the
302
fingerprint of this certificate is used by the Mandos server to
303
look up (in a list read from <filename>clients.conf</filename>
304
at start time) which binary blob to give the client. No other
305
authentication or authorization is done by the server.
308
<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
310
<entry>Mandos Client</entry>
311
<entry>Direction</entry>
312
<entry>Mandos Server</entry>
316
<entry>Connect</entry>
317
<entry>-><!-- → --></entry>
320
<entry><quote><literal>1\r\en</literal></quote></entry>
321
<entry>-><!-- → --></entry>
324
<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
326
<entry><-><!-- ⟷ --></entry>
327
<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
331
<entry>OpenPGP public key (part of TLS handshake)</entry>
332
<entry>-><!-- → --></entry>
336
<entry><-<!-- ← --></entry>
337
<entry>Binary blob (client will assume OpenPGP data)</entry>
341
<entry><-<!-- ← --></entry>
344
</tbody></tgroup></table>
347
<refsect1 id="checking">
348
<title>CHECKING</title>
350
The server will, by default, continually check that the clients
351
are still up. If a client has not been confirmed as being up
352
for some time, the client is assumed to be compromised and is no
353
longer eligible to receive the encrypted password. The timeout,
354
checker program, and interval between checks can be configured
355
both globally and per client; see <citerefentry>
356
<refentrytitle>mandos.conf</refentrytitle>
357
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
358
<refentrytitle>mandos-clients.conf</refentrytitle>
359
<manvolnum>5</manvolnum></citerefentry>.
363
<refsect1 id="logging">
364
<title>LOGGING</title>
366
The server will send log messaged with various severity levels
367
to <filename>/dev/log</filename>. With the
368
<option>--debug</option> option, it will log even more messages,
369
and also show them on the console.
373
<refsect1 id="exit_status">
374
<title>EXIT STATUS</title>
376
The server will exit with a non-zero exit status only when a
377
critical error is encountered.
381
<refsect1 id="environment">
382
<title>ENVIRONMENT</title>
385
<term><varname>PATH</varname></term>
388
To start the configured checker (see <xref
389
linkend="checking"/>), the server uses
390
<filename>/bin/sh</filename>, which in turn uses
391
<varname>PATH</varname> to search for matching commands if
392
an absolute path is not given. See <citerefentry>
393
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
404
Use the <option>--configdir</option> option to change where
405
<command>&COMMANDNAME;</command> looks for its configurations
406
files. The default file names are listed here.
410
<term><filename>/etc/mandos/mandos.conf</filename></term>
413
Server-global settings. See
414
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
415
<manvolnum>5</manvolnum></citerefentry> for details.
420
<term><filename>/etc/mandos/clients.conf</filename></term>
423
List of clients and client-specific settings. See
424
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
425
<manvolnum>5</manvolnum></citerefentry> for details.
430
<term><filename>/var/run/mandos/mandos.pid</filename></term>
433
The file containing the process id of
434
<command>&COMMANDNAME;</command>.
439
<term><filename>/dev/log</filename></term>
442
The Unix domain socket to where local syslog messages are
448
<term><filename>/bin/sh</filename></term>
451
This is used to start the configured checker command for
452
each client. See <citerefentry>
453
<refentrytitle>mandos-clients.conf</refentrytitle>
454
<manvolnum>5</manvolnum></citerefentry> for details.
464
This server might, on especially fatal errors, emit a Python
465
backtrace. This could be considered a feature.
468
Currently, if a client is declared <quote>invalid</quote> due to
469
having timed out, the server does not record this fact onto
470
permanent storage. This has some security implications, see
471
<xref linkend="CLIENTS"/>.
474
There is currently no way of querying the server of the current
475
status of clients, other than analyzing its <systemitem
476
class="service">syslog</systemitem> output.
479
There is no fine-grained control over logging and debug output.
482
Debug mode is conflated with running in the foreground.
485
The console log messages does not show a timestamp.
489
<refsect1 id="example">
490
<title>EXAMPLE</title>
493
Normal invocation needs no options:
496
<userinput>mandos</userinput>
501
Run the server in debug mode, read configuration files from
502
the <filename>~/mandos</filename> directory, and use the
503
Zeroconf service name <quote>Test</quote> to not collide with
504
any other official Mandos server on this host:
508
<!-- do not wrap this line -->
509
<userinput>mandos --debug --configdir ~/mandos --servicename Test</userinput>
515
Run the server normally, but only listen to one interface and
516
only on the link-local address on that interface:
520
<!-- do not wrap this line -->
521
<userinput>mandos --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
527
<refsect1 id="security">
528
<title>SECURITY</title>
529
<refsect2 id="SERVER">
530
<title>SERVER</title>
532
Running this <command>&COMMANDNAME;</command> server program
533
should not in itself present any security risk to the host
534
computer running it. The program does not need any special
535
privileges to run, and is designed to run as a non-root user.
538
<refsect2 id="CLIENTS">
539
<title>CLIENTS</title>
541
The server only gives out its stored data to clients which
542
does have the OpenPGP key of the stored fingerprint. This is
543
guaranteed by the fact that the client sends its OpenPGP
544
public key in the TLS handshake; this ensures it to be
545
genuine. The server computes the fingerprint of the key
546
itself and looks up the fingerprint in its list of
547
clients. The <filename>clients.conf</filename> file (see
548
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
549
<manvolnum>5</manvolnum></citerefentry>)
550
<emphasis>must</emphasis> be made non-readable by anyone
551
except the user running the server.
554
As detailed in <xref linkend="checking"/>, the status of all
555
client computers will continually be checked and be assumed
556
compromised if they are gone for too long.
559
If a client is compromised, its downtime should be duly noted
560
by the server which would therefore declare the client
561
invalid. But if the server was ever restarted, it would
562
re-read its client list from its configuration file and again
563
regard all clients therein as valid, and hence eligible to
564
receive their passwords. Therefore, be careful when
565
restarting servers if it is suspected that a client has, in
566
fact, been compromised by parties who may now be running a
567
fake Mandos client with the keys from the non-encrypted
568
initial RAM image of the client host. What should be done in
569
that case (if restarting the server program really is
570
necessary) is to stop the server program, edit the
571
configuration file to omit any suspect clients, and restart
575
For more details on client-side security, see
576
<citerefentry><refentrytitle>password-request</refentrytitle>
577
<manvolnum>8mandos</manvolnum></citerefentry>.
582
<refsect1 id="see_also">
583
<title>SEE ALSO</title>
588
<refentrytitle>password-request</refentrytitle>
589
<manvolnum>8mandos</manvolnum>
594
This is the actual program which talks to this server.
595
Note that it is normally not invoked directly, and is only
596
run in the initial RAM disk environment, and not on a
597
fully started system.
603
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
607
Zeroconf is the network protocol standard used by clients
608
for finding this Mandos server on the local network.
614
<ulink url="http://www.avahi.org/">Avahi</ulink>
618
Avahi is the library this server calls to implement
619
Zeroconf service announcements.
626
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
630
GnuTLS is the library this server uses to implement TLS for
631
communicating securely with the client, and at the same time
632
confidently get the client’s public OpenPGP key.
638
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
639
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
640
Unicast Addresses</citation>
644
The clients use IPv6 link-local addresses, which are
645
immediately usable since a link-local addresses is
646
automatically assigned to a network interfaces when it is
653
<citation>RFC 4346: <citetitle>The Transport Layer Security
654
(TLS) Protocol Version 1.1</citetitle></citation>
658
TLS 1.1 is the protocol implemented by GnuTLS.
664
<citation>RFC 4880: <citetitle>OpenPGP Message
665
Format</citetitle></citation>
669
The data sent to clients is binary encrypted OpenPGP data.
675
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
676
Transport Layer Security</citetitle></citation>
680
This is implemented by GnuTLS and used by this server so
681
that OpenPGP keys can be used.