67
66
<refname><command>&COMMANDNAME;</command></refname>
69
Sends encrypted passwords to authenticated mandos clients
68
Sends encrypted passwords to authenticated Mandos clients
75
74
<command>&COMMANDNAME;</command>
76
<arg choice='opt'>--interface<arg choice='plain'>IF</arg></arg>
77
<arg choice='opt'>--address<arg choice='plain'>ADDRESS</arg></arg>
78
<arg choice='opt'>--port<arg choice='plain'>PORT</arg></arg>
79
<arg choice='opt'>--priority<arg choice='plain'>PRIORITY</arg></arg>
80
<arg choice='opt'>--servicename<arg choice='plain'>NAME</arg></arg>
81
<arg choice='opt'>--configdir<arg choice='plain'>DIRECTORY</arg></arg>
82
<arg choice='opt'>--debug</arg>
85
<command>&COMMANDNAME;</command>
86
<arg choice='plain'>--help</arg>
89
<command>&COMMANDNAME;</command>
90
<arg choice='plain'>--version</arg>
93
<command>&COMMANDNAME;</command>
94
<arg choice='plain'>--check</arg>
75
<arg>--interface<arg choice="plain">IF</arg></arg>
76
<arg>--address<arg choice="plain">ADDRESS</arg></arg>
77
<arg>--port<arg choice="plain">PORT</arg></arg>
78
<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
79
<arg>--servicename<arg choice="plain">NAME</arg></arg>
80
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
84
<command>&COMMANDNAME;</command>
85
<arg>-i<arg choice="plain">IF</arg></arg>
86
<arg>-a<arg choice="plain">ADDRESS</arg></arg>
87
<arg>-p<arg choice="plain">PORT</arg></arg>
88
<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
89
<arg>--servicename<arg choice="plain">NAME</arg></arg>
90
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
94
<command>&COMMANDNAME;</command>
96
<arg choice="plain">-h</arg>
97
<arg choice="plain">--help</arg>
101
<command>&COMMANDNAME;</command>
102
<arg choice="plain">--version</arg>
105
<command>&COMMANDNAME;</command>
106
<arg choice="plain">--check</arg>
98
110
<refsect1 id="description">
99
111
<title>DESCRIPTION</title>
101
<command>&COMMANDNAME;</command> is a server daemon that handels
102
incomming passwords request for passwords. Mandos use avahi to
103
announce the service, and through gnutls authenticates
104
clients. Any authenticated client is then given its encrypted
113
<command>&COMMANDNAME;</command> is a server daemon which
114
handles incoming request for passwords for a pre-defined list of
115
client host computers. The Mandos server uses Zeroconf to
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announce itself on the local network, and uses TLS to
117
communicate securely with and to authenticate the clients. The
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Mandos server uses IPv6 to allow Mandos clients to use IPv6
119
link-local addresses, since the clients will probably not have
120
any other addresses configured (see <xref linkend="overview"/>).
121
Any authenticated client is then given the stored pre-encrypted
122
password for that specific client.
127
<refsect1 id="purpose">
128
<title>PURPOSE</title>
131
The purpose of this is to enable <emphasis>remote and unattended
132
rebooting</emphasis> of client host computer with an
133
<emphasis>encrypted root file system</emphasis>. See <xref
134
linkend="overview"/> for details.
109
139
<refsect1 id="options">
110
140
<title>OPTIONS</title>
203
226
<term><literal>--version</literal></term>
206
Prints the program version
229
Prints the program version and exit.
236
<refsect1 id="overview">
237
<title>OVERVIEW</title>
238
<xi:include href="overview.xml"/>
240
This program is the server part. It is a normal server program
241
and will run in a normal system environment, not in an initial
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RAM disk environment.
246
<refsect1 id="protocol">
247
<title>NETWORK PROTOCOL</title>
249
The Mandos server announces itself as a Zeroconf service of type
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<quote><literal>_mandos._tcp</literal></quote>. The Mandos
251
client connects to the announced address and port, and sends a
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line of text where the first whitespace-separated field is the
253
protocol version, which currently is
254
<quote><literal>1</literal></quote>. The client and server then
255
start a TLS protocol handshake with a slight quirk: the Mandos
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server program acts as a TLS <quote>client</quote> while the
257
connecting Mandos client acts as a TLS <quote>server</quote>.
258
The Mandos client must supply an OpenPGP certificate, and the
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fingerprint of this certificate is used by the Mandos server to
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look up (in a list read from <filename>clients.conf</filename>
261
at start time) which binary blob to give the client. No other
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authentication or authorization is done by the server.
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<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
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<entry>Mandos Client</entry>
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<entry>Direction</entry>
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<entry>Mandos Server</entry>
273
<entry>Connect</entry>
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<entry>-><!-- → --></entry>
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<entry><quote><literal>1\r\n</literal></quote></entry>
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<entry>-><!-- → --></entry>
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<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
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<entry><-><!-- ⟷ --></entry>
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<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
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<entry>OpenPGP public key (part of TLS handshake)</entry>
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<entry>-><!-- → --></entry>
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<entry><-<!-- ← --></entry>
294
<entry>Binary blob (client will assume OpenPGP data)</entry>
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<entry><-<!-- ← --></entry>
301
</tbody></tgroup></table>
304
<refsect1 id="checking">
305
<title>CHECKING</title>
307
The server will, by default, continually check that the clients
308
are still up. If a client has not been confirmed as being up
309
for some time, the client is assumed to be compromised and is no
310
longer eligible to receive the encrypted password. The timeout,
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checker program, and interval between checks can be configured
312
both globally and per client; see <citerefentry>
313
<refentrytitle>mandos-clients.conf</refentrytitle>
314
<manvolnum>5</manvolnum></citerefentry>.
318
<refsect1 id="logging">
319
<title>LOGGING</title>
321
The server will send log message with various severity levels to
322
<filename>/dev/log</filename>. With the
323
<option>--debug</option> option, it will log even more messages,
324
and also show them on the console.
213
328
<refsect1 id="exit_status">
214
329
<title>EXIT STATUS</title>
331
The server will exit with a non-zero exit status only when a
332
critical error is encountered.
336
<refsect1 id="environment">
337
<title>ENVIRONMENT</title>
340
<term><varname>PATH</varname></term>
343
To start the configured checker (see <xref
344
linkend="checking"/>), the server uses
345
<filename>/bin/sh</filename>, which in turn uses
346
<varname>PATH</varname> to search for matching commands if
347
an absolute path is not given. See <citerefentry>
348
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
219
356
<refsect1 id="file">
220
357
<title>FILES</title>
225
<refsect1 id="notes">
359
Use the <option>--configdir</option> option to change where
360
<command>&COMMANDNAME;</command> looks for its configurations
361
files. The default file names are listed here.
365
<term><filename>/etc/mandos/mandos.conf</filename></term>
368
Server-global settings. See
369
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
370
<manvolnum>5</manvolnum></citerefentry> for details.
375
<term><filename>/etc/mandos/clients.conf</filename></term>
378
List of clients and client-specific settings. See
379
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
380
<manvolnum>5</manvolnum></citerefentry> for details.
385
<term><filename>/var/run/mandos/mandos.pid</filename></term>
388
The file containing the process id of
389
<command>&COMMANDNAME;</command>.
394
<term><filename>/dev/log</filename></term>
397
The Unix domain socket to where local syslog messages are
403
<term><filename>/bin/sh</filename></term>
406
This is used to start the configured checker command for
407
each client. See <citerefentry>
408
<refentrytitle>mandos-clients.conf</refentrytitle>
409
<manvolnum>5</manvolnum></citerefentry> for details.
231
416
<refsect1 id="bugs">
232
417
<title>BUGS</title>
237
<refsect1 id="examples">
238
<title>EXAMPLES</title>
419
This server might, on especially fatal errors, emit a Python
420
backtrace. This could be considered a feature.
423
Currently, if a client is declared <quote>invalid</quote> due to
424
having timed out, the server does not record this fact onto
425
permanent storage. This has some security implications, see
426
<xref linkend="CLIENTS"/>.
429
There is currently no way of querying the server of the current
430
status of clients, other than analyzing its <systemitem
431
class="service">syslog</systemitem> output.
434
There is no fine-grained control over logging and debug output.
437
Debug mode is conflated with running in the foreground.
440
The console log messages does not show a timestamp.
444
<refsect1 id="example">
445
<title>EXAMPLE</title>
448
Normal invocation needs no options:
451
<userinput>mandos</userinput>
456
Run the server in debug mode, read configuration files from
457
the <filename>~/mandos</filename> directory, and use the
458
Zeroconf service name <quote>Test</quote> to not collide with
459
any other official Mandos server on this host:
463
<!-- do not wrap this line -->
464
<userinput>mandos --debug --configdir ~/mandos --servicename Test</userinput>
470
Run the server normally, but only listen to one interface and
471
only on the link-local address on that interface:
475
<!-- do not wrap this line -->
476
<userinput>mandos --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
243
482
<refsect1 id="security">
244
483
<title>SECURITY</title>
484
<refsect2 id="SERVER">
485
<title>SERVER</title>
487
Running this <command>&COMMANDNAME;</command> server program
488
should not in itself present any security risk to the host
489
computer running it. The program does not need any special
490
privileges to run, and is designed to run as a non-root user.
493
<refsect2 id="CLIENTS">
494
<title>CLIENTS</title>
496
The server only gives out its stored data to clients which
497
does have the OpenPGP key of the stored fingerprint. This is
498
guaranteed by the fact that the client sends its OpenPGP
499
public key in the TLS handshake; this ensures it to be
500
genuine. The server computes the fingerprint of the key
501
itself and looks up the fingerprint in its list of
502
clients. The <filename>clients.conf</filename> file (see
503
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
504
<manvolnum>5</manvolnum></citerefentry>)
505
<emphasis>must</emphasis> be made non-readable by anyone
506
except the user running the server.
509
As detailed in <xref linkend="checking"/>, the status of all
510
client computers will continually be checked and be assumed
511
compromised if they are gone for too long.
514
If a client is compromised, its downtime should be duly noted
515
by the server which would therefore declare the client
516
invalid. But if the server was ever restarted, it would
517
re-read its client list from its configuration file and again
518
regard all clients therein as valid, and hence eligible to
519
receive their passwords. Therefore, be careful when
520
restarting servers if it is suspected that a client has, in
521
fact, been compromised by parties who may now be running a
522
fake Mandos client with the keys from the non-encrypted
523
initial RAM image of the client host. What should be done in
524
that case (if restarting the server program really is
525
necessary) is to stop the server program, edit the
526
configuration file to omit any suspect clients, and restart
530
For more details on client-side security, see
531
<citerefentry><refentrytitle>password-request</refentrytitle>
532
<manvolnum>8mandos</manvolnum></citerefentry>.
249
537
<refsect1 id="see_also">
250
538
<title>SEE ALSO</title>
252
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
253
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
254
<refentrytitle>password-request</refentrytitle>
255
<manvolnum>8mandos</manvolnum></citerefentry> and <citerefentry>
256
<refentrytitle>password-prompt</refentrytitle>
257
<manvolnum>8mandos</manvolnum></citerefentry>
541
<refentrytitle>mandos.conf</refentrytitle>
542
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
543
<refentrytitle>mandos-clients.conf</refentrytitle>
544
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
545
<refentrytitle>password-request</refentrytitle>
546
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
547
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
553
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
557
Zeroconf is the network protocol standard used by clients
558
for finding this Mandos server on the local network.
564
<ulink url="http://www.avahi.org/">Avahi</ulink>
568
Avahi is the library this server calls to implement
569
Zeroconf service announcements.
576
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
580
GnuTLS is the library this server uses to implement TLS for
581
communicating securely with the client, and at the same time
582
confidently get the client’s public OpenPGP key.
588
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
589
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
590
Unicast Addresses</citation>
594
The clients use IPv6 link-local addresses, which are
595
immediately usable since a link-local addresses is
596
automatically assigned to a network interfaces when it is
603
<citation>RFC 4346: <citetitle>The Transport Layer Security
604
(TLS) Protocol Version 1.1</citetitle></citation>
608
TLS 1.1 is the protocol implemented by GnuTLS.
614
<citation>RFC 4880: <citetitle>OpenPGP Message
615
Format</citetitle></citation>
619
The data sent to clients is binary encrypted OpenPGP data.
625
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
626
Transport Layer Security</citetitle></citation>
630
This is implemented by GnuTLS and used by this server so
631
that OpenPGP keys can be used.