67
50
<refname><command>&COMMANDNAME;</command></refname>
69
Sends encrypted passwords to authenticated mandos clients
52
Gives encrypted passwords to authenticated Mandos clients
75
58
<command>&COMMANDNAME;</command>
76
<arg choice='opt' rep='repeat'>OPTION</arg>
60
<arg choice="plain"><option>--interface
61
<replaceable>NAME</replaceable></option></arg>
62
<arg choice="plain"><option>-i
63
<replaceable>NAME</replaceable></option></arg>
67
<arg choice="plain"><option>--address
68
<replaceable>ADDRESS</replaceable></option></arg>
69
<arg choice="plain"><option>-a
70
<replaceable>ADDRESS</replaceable></option></arg>
74
<arg choice="plain"><option>--port
75
<replaceable>PORT</replaceable></option></arg>
76
<arg choice="plain"><option>-p
77
<replaceable>PORT</replaceable></option></arg>
80
<arg><option>--priority
81
<replaceable>PRIORITY</replaceable></option></arg>
83
<arg><option>--servicename
84
<replaceable>NAME</replaceable></option></arg>
86
<arg><option>--configdir
87
<replaceable>DIRECTORY</replaceable></option></arg>
89
<arg><option>--debug</option></arg>
91
<arg><option>--debuglevel
92
<replaceable>LEVEL</replaceable></option></arg>
94
<arg><option>--no-dbus</option></arg>
96
<arg><option>--no-ipv6</option></arg>
99
<command>&COMMANDNAME;</command>
101
<arg choice="plain"><option>--help</option></arg>
102
<arg choice="plain"><option>-h</option></arg>
106
<command>&COMMANDNAME;</command>
107
<arg choice="plain"><option>--version</option></arg>
110
<command>&COMMANDNAME;</command>
111
<arg choice="plain"><option>--check</option></arg>
80
115
<refsect1 id="description">
81
116
<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
92
<term><literal>-h</literal>, <literal>--help</literal></term>
95
show a help message and exit
101
<term><literal>-i</literal>, <literal>--interface <replaceable>
102
IF</replaceable></literal></term>
111
<term><literal>-a</literal>, <literal>--address <replaceable>
112
ADDRESS</replaceable></literal></term>
115
Address to listen for requests on
121
<term><literal>-p</literal>, <literal>--port <replaceable>
122
PORT</replaceable></literal></term>
125
Port number to receive requests on
131
<term><literal>--check</literal></term>
134
Run self-test on the server
140
<term><literal>--debug</literal></term>
149
<term><literal>--priority <replaceable>
150
PRIORITY</replaceable></literal></term>
153
GnuTLS priority string. See <citerefentry>
154
<refentrytitle>gnutls_priority_init</refentrytitle>
155
<manvolnum>3</manvolnum></citerefentry>
161
<term><literal>--servicename <replaceable>NAME</replaceable>
165
Zeroconf service name
171
<term><literal>--configdir <replaceable>DIR</replaceable>
175
Directory to search for configuration files
118
<command>&COMMANDNAME;</command> is a server daemon which
119
handles incoming request for passwords for a pre-defined list of
120
client host computers. For an introduction, see
121
<citerefentry><refentrytitle>intro</refentrytitle>
122
<manvolnum>8mandos</manvolnum></citerefentry>. The Mandos server
123
uses Zeroconf to announce itself on the local network, and uses
124
TLS to communicate securely with and to authenticate the
125
clients. The Mandos server uses IPv6 to allow Mandos clients to
126
use IPv6 link-local addresses, since the clients will probably
127
not have any other addresses configured (see <xref
128
linkend="overview"/>). Any authenticated client is then given
129
the stored pre-encrypted password for that specific client.
133
<refsect1 id="purpose">
134
<title>PURPOSE</title>
136
The purpose of this is to enable <emphasis>remote and unattended
137
rebooting</emphasis> of client host computer with an
138
<emphasis>encrypted root file system</emphasis>. See <xref
139
linkend="overview"/> for details.
143
<refsect1 id="options">
144
<title>OPTIONS</title>
147
<term><option>--help</option></term>
148
<term><option>-h</option></term>
151
Show a help message and exit
157
<term><option>--interface</option>
158
<replaceable>NAME</replaceable></term>
159
<term><option>-i</option>
160
<replaceable>NAME</replaceable></term>
162
<xi:include href="mandos-options.xml" xpointer="interface"/>
167
<term><option>--address
168
<replaceable>ADDRESS</replaceable></option></term>
170
<replaceable>ADDRESS</replaceable></option></term>
172
<xi:include href="mandos-options.xml" xpointer="address"/>
178
<replaceable>PORT</replaceable></option></term>
180
<replaceable>PORT</replaceable></option></term>
182
<xi:include href="mandos-options.xml" xpointer="port"/>
187
<term><option>--check</option></term>
190
Run the server’s self-tests. This includes any unit
197
<term><option>--debug</option></term>
199
<xi:include href="mandos-options.xml" xpointer="debug"/>
204
<term><option>--debuglevel
205
<replaceable>LEVEL</replaceable></option></term>
208
Set the debugging log level.
209
<replaceable>LEVEL</replaceable> is a string, one of
210
<quote><literal>CRITICAL</literal></quote>,
211
<quote><literal>ERROR</literal></quote>,
212
<quote><literal>WARNING</literal></quote>,
213
<quote><literal>INFO</literal></quote>, or
214
<quote><literal>DEBUG</literal></quote>, in order of
215
increasing verbosity. The default level is
216
<quote><literal>WARNING</literal></quote>.
222
<term><option>--priority <replaceable>
223
PRIORITY</replaceable></option></term>
225
<xi:include href="mandos-options.xml" xpointer="priority"/>
230
<term><option>--servicename
231
<replaceable>NAME</replaceable></option></term>
233
<xi:include href="mandos-options.xml"
234
xpointer="servicename"/>
239
<term><option>--configdir
240
<replaceable>DIRECTORY</replaceable></option></term>
243
Directory to search for configuration files. Default is
244
<quote><literal>/etc/mandos</literal></quote>. See
245
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
246
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
247
<refentrytitle>mandos-clients.conf</refentrytitle>
248
<manvolnum>5</manvolnum></citerefentry>.
254
<term><option>--version</option></term>
257
Prints the program version and exit.
263
<term><option>--no-dbus</option></term>
265
<xi:include href="mandos-options.xml" xpointer="dbus"/>
267
See also <xref linkend="dbus_interface"/>.
273
<term><option>--no-ipv6</option></term>
275
<xi:include href="mandos-options.xml" xpointer="ipv6"/>
281
<refsect1 id="overview">
282
<title>OVERVIEW</title>
283
<xi:include href="overview.xml"/>
285
This program is the server part. It is a normal server program
286
and will run in a normal system environment, not in an initial
287
<acronym>RAM</acronym> disk environment.
291
<refsect1 id="protocol">
292
<title>NETWORK PROTOCOL</title>
294
The Mandos server announces itself as a Zeroconf service of type
295
<quote><literal>_mandos._tcp</literal></quote>. The Mandos
296
client connects to the announced address and port, and sends a
297
line of text where the first whitespace-separated field is the
298
protocol version, which currently is
299
<quote><literal>1</literal></quote>. The client and server then
300
start a TLS protocol handshake with a slight quirk: the Mandos
301
server program acts as a TLS <quote>client</quote> while the
302
connecting Mandos client acts as a TLS <quote>server</quote>.
303
The Mandos client must supply an OpenPGP certificate, and the
304
fingerprint of this certificate is used by the Mandos server to
305
look up (in a list read from <filename>clients.conf</filename>
306
at start time) which binary blob to give the client. No other
307
authentication or authorization is done by the server.
310
<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
312
<entry>Mandos Client</entry>
313
<entry>Direction</entry>
314
<entry>Mandos Server</entry>
318
<entry>Connect</entry>
319
<entry>-><!-- → --></entry>
322
<entry><quote><literal>1\r\n</literal></quote></entry>
323
<entry>-><!-- → --></entry>
326
<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
328
<entry><-><!-- ⟷ --></entry>
329
<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
333
<entry>OpenPGP public key (part of TLS handshake)</entry>
334
<entry>-><!-- → --></entry>
338
<entry><-<!-- ← --></entry>
339
<entry>Binary blob (client will assume OpenPGP data)</entry>
343
<entry><-<!-- ← --></entry>
346
</tbody></tgroup></table>
349
<refsect1 id="checking">
350
<title>CHECKING</title>
352
The server will, by default, continually check that the clients
353
are still up. If a client has not been confirmed as being up
354
for some time, the client is assumed to be compromised and is no
355
longer eligible to receive the encrypted password. (Manual
356
intervention is required to re-enable a client.) The timeout,
357
extended timeout, checker program, and interval between checks
358
can be configured both globally and per client; see
359
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
360
<manvolnum>5</manvolnum></citerefentry>. A client successfully
361
receiving its password will also be treated as a successful
366
<refsect1 id="approval">
367
<title>APPROVAL</title>
369
The server can be configured to require manual approval for a
370
client before it is sent its secret. The delay to wait for such
371
approval and the default action (approve or deny) can be
372
configured both globally and per client; see <citerefentry>
373
<refentrytitle>mandos-clients.conf</refentrytitle>
374
<manvolnum>5</manvolnum></citerefentry>. By default all clients
375
will be approved immediately without delay.
378
This can be used to deny a client its secret if not manually
379
approved within a specified time. It can also be used to make
380
the server delay before giving a client its secret, allowing
381
optional manual denying of this specific client.
386
<refsect1 id="logging">
387
<title>LOGGING</title>
389
The server will send log message with various severity levels to
390
<filename>/dev/log</filename>. With the
391
<option>--debug</option> option, it will log even more messages,
392
and also show them on the console.
396
<refsect1 id="dbus_interface">
397
<title>D-BUS INTERFACE</title>
399
The server will by default provide a D-Bus system bus interface.
400
This interface will only be accessible by the root user or a
401
Mandos-specific user, if such a user exists. For documentation
402
of the D-Bus API, see the file <filename>DBUS-API</filename>.
406
<refsect1 id="exit_status">
407
<title>EXIT STATUS</title>
409
The server will exit with a non-zero exit status only when a
410
critical error is encountered.
414
<refsect1 id="environment">
415
<title>ENVIRONMENT</title>
418
<term><envar>PATH</envar></term>
421
To start the configured checker (see <xref
422
linkend="checking"/>), the server uses
423
<filename>/bin/sh</filename>, which in turn uses
424
<varname>PATH</varname> to search for matching commands if
425
an absolute path is not given. See <citerefentry>
426
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
434
<refsect1 id="files">
437
Use the <option>--configdir</option> option to change where
438
<command>&COMMANDNAME;</command> looks for its configurations
439
files. The default file names are listed here.
443
<term><filename>/etc/mandos/mandos.conf</filename></term>
446
Server-global settings. See
447
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
448
<manvolnum>5</manvolnum></citerefentry> for details.
453
<term><filename>/etc/mandos/clients.conf</filename></term>
456
List of clients and client-specific settings. See
457
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
458
<manvolnum>5</manvolnum></citerefentry> for details.
463
<term><filename>/var/run/mandos.pid</filename></term>
466
The file containing the process id of the
467
<command>&COMMANDNAME;</command> process started last.
472
<term><filename>/dev/log</filename></term>
475
The Unix domain socket to where local syslog messages are
481
<term><filename>/bin/sh</filename></term>
484
This is used to start the configured checker command for
485
each client. See <citerefentry>
486
<refentrytitle>mandos-clients.conf</refentrytitle>
487
<manvolnum>5</manvolnum></citerefentry> for details.
497
This server might, on especially fatal errors, emit a Python
498
backtrace. This could be considered a feature.
501
Currently, if a client is disabled due to having timed out, the
502
server does not record this fact onto permanent storage. This
503
has some security implications, see <xref linkend="clients"/>.
506
There is no fine-grained control over logging and debug output.
509
Debug mode is conflated with running in the foreground.
512
The console log messages do not show a time stamp.
515
This server does not check the expire time of clients’ OpenPGP
520
<refsect1 id="example">
521
<title>EXAMPLE</title>
524
Normal invocation needs no options:
527
<userinput>&COMMANDNAME;</userinput>
532
Run the server in debug mode, read configuration files from
533
the <filename>~/mandos</filename> directory, and use the
534
Zeroconf service name <quote>Test</quote> to not collide with
535
any other official Mandos server on this host:
539
<!-- do not wrap this line -->
540
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
546
Run the server normally, but only listen to one interface and
547
only on the link-local address on that interface:
551
<!-- do not wrap this line -->
552
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
558
<refsect1 id="security">
559
<title>SECURITY</title>
560
<refsect2 id="server">
561
<title>SERVER</title>
563
Running this <command>&COMMANDNAME;</command> server program
564
should not in itself present any security risk to the host
565
computer running it. The program switches to a non-root user
569
<refsect2 id="clients">
570
<title>CLIENTS</title>
572
The server only gives out its stored data to clients which
573
does have the OpenPGP key of the stored fingerprint. This is
574
guaranteed by the fact that the client sends its OpenPGP
575
public key in the TLS handshake; this ensures it to be
576
genuine. The server computes the fingerprint of the key
577
itself and looks up the fingerprint in its list of
578
clients. The <filename>clients.conf</filename> file (see
579
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
580
<manvolnum>5</manvolnum></citerefentry>)
581
<emphasis>must</emphasis> be made non-readable by anyone
582
except the user starting the server (usually root).
585
As detailed in <xref linkend="checking"/>, the status of all
586
client computers will continually be checked and be assumed
587
compromised if they are gone for too long.
590
If a client is compromised, its downtime should be duly noted
591
by the server which would therefore disable the client. But
592
if the server was ever restarted, it would re-read its client
593
list from its configuration file and again regard all clients
594
therein as enabled, and hence eligible to receive their
595
passwords. Therefore, be careful when restarting servers if
596
it is suspected that a client has, in fact, been compromised
597
by parties who may now be running a fake Mandos client with
598
the keys from the non-encrypted initial <acronym>RAM</acronym>
599
image of the client host. What should be done in that case
600
(if restarting the server program really is necessary) is to
601
stop the server program, edit the configuration file to omit
602
any suspect clients, and restart the server program.
605
For more details on client-side security, see
606
<citerefentry><refentrytitle>mandos-client</refentrytitle>
607
<manvolnum>8mandos</manvolnum></citerefentry>.
612
<refsect1 id="see_also">
613
<title>SEE ALSO</title>
615
<citerefentry><refentrytitle>intro</refentrytitle>
616
<manvolnum>8mandos</manvolnum></citerefentry>,
617
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
618
<manvolnum>5</manvolnum></citerefentry>,
619
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
620
<manvolnum>5</manvolnum></citerefentry>,
621
<citerefentry><refentrytitle>mandos-client</refentrytitle>
622
<manvolnum>8mandos</manvolnum></citerefentry>,
623
<citerefentry><refentrytitle>sh</refentrytitle>
624
<manvolnum>1</manvolnum></citerefentry>
629
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
633
Zeroconf is the network protocol standard used by clients
634
for finding this Mandos server on the local network.
640
<ulink url="http://www.avahi.org/">Avahi</ulink>
644
Avahi is the library this server calls to implement
645
Zeroconf service announcements.
651
<ulink url="http://www.gnu.org/software/gnutls/"
656
GnuTLS is the library this server uses to implement TLS for
657
communicating securely with the client, and at the same time
658
confidently get the client’s public OpenPGP key.
664
RFC 4291: <citetitle>IP Version 6 Addressing
665
Architecture</citetitle>
670
<term>Section 2.2: <citetitle>Text Representation of
671
Addresses</citetitle></term>
672
<listitem><para/></listitem>
675
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
676
Address</citetitle></term>
677
<listitem><para/></listitem>
680
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
681
Addresses</citetitle></term>
684
The clients use IPv6 link-local addresses, which are
685
immediately usable since a link-local addresses is
686
automatically assigned to a network interfaces when it
696
RFC 4346: <citetitle>The Transport Layer Security (TLS)
697
Protocol Version 1.1</citetitle>
701
TLS 1.1 is the protocol implemented by GnuTLS.
707
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
711
The data sent to clients is binary encrypted OpenPGP data.
717
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
722
This is implemented by GnuTLS and used by this server so
723
that OpenPGP keys can be used.
730
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