47
67
<refname><command>&COMMANDNAME;</command></refname>
49
Gives encrypted passwords to authenticated Mandos clients
69
Sends encrypted passwords to authenticated mandos clients
55
75
<command>&COMMANDNAME;</command>
57
<arg choice="plain"><option>--interface
58
<replaceable>NAME</replaceable></option></arg>
59
<arg choice="plain"><option>-i
60
<replaceable>NAME</replaceable></option></arg>
64
<arg choice="plain"><option>--address
65
<replaceable>ADDRESS</replaceable></option></arg>
66
<arg choice="plain"><option>-a
67
<replaceable>ADDRESS</replaceable></option></arg>
71
<arg choice="plain"><option>--port
72
<replaceable>PORT</replaceable></option></arg>
73
<arg choice="plain"><option>-p
74
<replaceable>PORT</replaceable></option></arg>
77
<arg><option>--priority
78
<replaceable>PRIORITY</replaceable></option></arg>
80
<arg><option>--servicename
81
<replaceable>NAME</replaceable></option></arg>
83
<arg><option>--configdir
84
<replaceable>DIRECTORY</replaceable></option></arg>
86
<arg><option>--debug</option></arg>
89
<command>&COMMANDNAME;</command>
91
<arg choice="plain"><option>--help</option></arg>
92
<arg choice="plain"><option>-h</option></arg>
96
<command>&COMMANDNAME;</command>
97
<arg choice="plain"><option>--version</option></arg>
100
<command>&COMMANDNAME;</command>
101
<arg choice="plain"><option>--check</option></arg>
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'>--check</arg>
93
<command>&COMMANDNAME;</command>
94
<arg choice='plain'>--version</arg>
105
98
<refsect1 id="description">
106
99
<title>DESCRIPTION</title>
108
<command>&COMMANDNAME;</command> is a server daemon which
109
handles incoming request for passwords for a pre-defined list of
110
client host computers. The Mandos server uses Zeroconf to
111
announce itself on the local network, and uses TLS to
112
communicate securely with and to authenticate the clients. The
113
Mandos server uses IPv6 to allow Mandos clients to use IPv6
114
link-local addresses, since the clients will probably not have
115
any other addresses configured (see <xref linkend="overview"/>).
116
Any authenticated client is then given the stored pre-encrypted
117
password for that specific client.
121
<refsect1 id="purpose">
122
<title>PURPOSE</title>
124
The purpose of this is to enable <emphasis>remote and unattended
125
rebooting</emphasis> of client host computer with an
126
<emphasis>encrypted root file system</emphasis>. See <xref
127
linkend="overview"/> for details.
131
<refsect1 id="options">
132
<title>OPTIONS</title>
135
<term><option>--help</option></term>
136
<term><option>-h</option></term>
139
Show a help message and exit
145
<term><option>--interface</option>
146
<replaceable>NAME</replaceable></term>
147
<term><option>-i</option>
148
<replaceable>NAME</replaceable></term>
150
<xi:include href="mandos-options.xml" xpointer="interface"/>
155
<term><option>--address
156
<replaceable>ADDRESS</replaceable></option></term>
158
<replaceable>ADDRESS</replaceable></option></term>
160
<xi:include href="mandos-options.xml" xpointer="address"/>
166
<replaceable>PORT</replaceable></option></term>
168
<replaceable>PORT</replaceable></option></term>
170
<xi:include href="mandos-options.xml" xpointer="port"/>
175
<term><option>--check</option></term>
178
Run the server’s self-tests. This includes any unit
185
<term><option>--debug</option></term>
187
<xi:include href="mandos-options.xml" xpointer="debug"/>
192
<term><option>--priority <replaceable>
193
PRIORITY</replaceable></option></term>
195
<xi:include href="mandos-options.xml" xpointer="priority"/>
200
<term><option>--servicename
201
<replaceable>NAME</replaceable></option></term>
203
<xi:include href="mandos-options.xml"
204
xpointer="servicename"/>
209
<term><option>--configdir
210
<replaceable>DIRECTORY</replaceable></option></term>
213
Directory to search for configuration files. Default is
214
<quote><literal>/etc/mandos</literal></quote>. See
215
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
216
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
217
<refentrytitle>mandos-clients.conf</refentrytitle>
218
<manvolnum>5</manvolnum></citerefentry>.
224
<term><option>--version</option></term>
227
Prints the program version and exit.
234
<refsect1 id="overview">
235
<title>OVERVIEW</title>
236
<xi:include href="overview.xml"/>
238
This program is the server part. It is a normal server program
239
and will run in a normal system environment, not in an initial
240
<acronym>RAM</acronym> disk environment.
244
<refsect1 id="protocol">
245
<title>NETWORK PROTOCOL</title>
247
The Mandos server announces itself as a Zeroconf service of type
248
<quote><literal>_mandos._tcp</literal></quote>. The Mandos
249
client connects to the announced address and port, and sends a
250
line of text where the first whitespace-separated field is the
251
protocol version, which currently is
252
<quote><literal>1</literal></quote>. The client and server then
253
start a TLS protocol handshake with a slight quirk: the Mandos
254
server program acts as a TLS <quote>client</quote> while the
255
connecting Mandos client acts as a TLS <quote>server</quote>.
256
The Mandos client must supply an OpenPGP certificate, and the
257
fingerprint of this certificate is used by the Mandos server to
258
look up (in a list read from <filename>clients.conf</filename>
259
at start time) which binary blob to give the client. No other
260
authentication or authorization is done by the server.
263
<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
265
<entry>Mandos Client</entry>
266
<entry>Direction</entry>
267
<entry>Mandos Server</entry>
271
<entry>Connect</entry>
272
<entry>-><!-- → --></entry>
275
<entry><quote><literal>1\r\n</literal></quote></entry>
276
<entry>-><!-- → --></entry>
279
<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
281
<entry><-><!-- ⟷ --></entry>
282
<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
286
<entry>OpenPGP public key (part of TLS handshake)</entry>
287
<entry>-><!-- → --></entry>
291
<entry><-<!-- ← --></entry>
292
<entry>Binary blob (client will assume OpenPGP data)</entry>
296
<entry><-<!-- ← --></entry>
299
</tbody></tgroup></table>
302
<refsect1 id="checking">
303
<title>CHECKING</title>
305
The server will, by default, continually check that the clients
306
are still up. If a client has not been confirmed as being up
307
for some time, the client is assumed to be compromised and is no
308
longer eligible to receive the encrypted password. The timeout,
309
checker program, and interval between checks can be configured
310
both globally and per client; see <citerefentry>
311
<refentrytitle>mandos-clients.conf</refentrytitle>
312
<manvolnum>5</manvolnum></citerefentry>.
316
<refsect1 id="logging">
317
<title>LOGGING</title>
319
The server will send log message with various severity levels to
320
<filename>/dev/log</filename>. With the
321
<option>--debug</option> option, it will log even more messages,
322
and also show them on the console.
326
<refsect1 id="exit_status">
327
<title>EXIT STATUS</title>
329
The server will exit with a non-zero exit status only when a
330
critical error is encountered.
334
<refsect1 id="environment">
335
<title>ENVIRONMENT</title>
338
<term><envar>PATH</envar></term>
341
To start the configured checker (see <xref
342
linkend="checking"/>), the server uses
343
<filename>/bin/sh</filename>, which in turn uses
344
<varname>PATH</varname> to search for matching commands if
345
an absolute path is not given. See <citerefentry>
346
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
357
Use the <option>--configdir</option> option to change where
358
<command>&COMMANDNAME;</command> looks for its configurations
359
files. The default file names are listed here.
363
<term><filename>/etc/mandos/mandos.conf</filename></term>
366
Server-global settings. See
367
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
368
<manvolnum>5</manvolnum></citerefentry> for details.
373
<term><filename>/etc/mandos/clients.conf</filename></term>
376
List of clients and client-specific settings. See
377
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
378
<manvolnum>5</manvolnum></citerefentry> for details.
383
<term><filename>/var/run/mandos.pid</filename></term>
386
The file containing the process id of
387
<command>&COMMANDNAME;</command>.
392
<term><filename>/dev/log</filename></term>
395
The Unix domain socket to where local syslog messages are
401
<term><filename>/bin/sh</filename></term>
404
This is used to start the configured checker command for
405
each client. See <citerefentry>
406
<refentrytitle>mandos-clients.conf</refentrytitle>
407
<manvolnum>5</manvolnum></citerefentry> for details.
417
This server might, on especially fatal errors, emit a Python
418
backtrace. This could be considered a feature.
421
Currently, if a client is declared <quote>invalid</quote> due to
422
having timed out, the server does not record this fact onto
423
permanent storage. This has some security implications, see
424
<xref linkend="CLIENTS"/>.
427
There is currently no way of querying the server of the current
428
status of clients, other than analyzing its <systemitem
429
class="service">syslog</systemitem> output.
432
There is no fine-grained control over logging and debug output.
435
Debug mode is conflated with running in the foreground.
438
The console log messages does not show a time stamp.
441
This server does not check the expire time of clients’ OpenPGP
446
<refsect1 id="example">
447
<title>EXAMPLE</title>
450
Normal invocation needs no options:
453
<userinput>&COMMANDNAME;</userinput>
458
Run the server in debug mode, read configuration files from
459
the <filename>~/mandos</filename> directory, and use the
460
Zeroconf service name <quote>Test</quote> to not collide with
461
any other official Mandos server on this host:
465
<!-- do not wrap this line -->
466
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
472
Run the server normally, but only listen to one interface and
473
only on the link-local address on that interface:
477
<!-- do not wrap this line -->
478
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
484
<refsect1 id="security">
485
<title>SECURITY</title>
486
<refsect2 id="SERVER">
487
<title>SERVER</title>
489
Running this <command>&COMMANDNAME;</command> server program
490
should not in itself present any security risk to the host
491
computer running it. The program switches to a non-root user
495
<refsect2 id="CLIENTS">
496
<title>CLIENTS</title>
498
The server only gives out its stored data to clients which
499
does have the OpenPGP key of the stored fingerprint. This is
500
guaranteed by the fact that the client sends its OpenPGP
501
public key in the TLS handshake; this ensures it to be
502
genuine. The server computes the fingerprint of the key
503
itself and looks up the fingerprint in its list of
504
clients. The <filename>clients.conf</filename> file (see
505
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
506
<manvolnum>5</manvolnum></citerefentry>)
507
<emphasis>must</emphasis> be made non-readable by anyone
508
except the user starting the server (usually root).
511
As detailed in <xref linkend="checking"/>, the status of all
512
client computers will continually be checked and be assumed
513
compromised if they are gone for too long.
516
If a client is compromised, its downtime should be duly noted
517
by the server which would therefore declare the client
518
invalid. But if the server was ever restarted, it would
519
re-read its client list from its configuration file and again
520
regard all clients therein as valid, and hence eligible to
521
receive their passwords. Therefore, be careful when
522
restarting servers if it is suspected that a client has, in
523
fact, been compromised by parties who may now be running a
524
fake Mandos client with the keys from the non-encrypted
525
initial <acronym>RAM</acronym> image of the client host. What
526
should be done in that case (if restarting the server program
527
really is necessary) is to stop the server program, edit the
528
configuration file to omit any suspect clients, and restart
532
For more details on client-side security, see
533
<citerefentry><refentrytitle>mandos-client</refentrytitle>
534
<manvolnum>8mandos</manvolnum></citerefentry>.
539
<refsect1 id="see_also">
540
<title>SEE ALSO</title>
543
<refentrytitle>mandos-clients.conf</refentrytitle>
544
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
545
<refentrytitle>mandos.conf</refentrytitle>
546
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
547
<refentrytitle>mandos-client</refentrytitle>
548
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
549
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
555
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
559
Zeroconf is the network protocol standard used by clients
560
for finding this Mandos server on the local network.
566
<ulink url="http://www.avahi.org/">Avahi</ulink>
570
Avahi is the library this server calls to implement
571
Zeroconf service announcements.
577
<ulink url="http://www.gnu.org/software/gnutls/"
582
GnuTLS is the library this server uses to implement TLS for
583
communicating securely with the client, and at the same time
584
confidently get the client’s public OpenPGP key.
590
RFC 4291: <citetitle>IP Version 6 Addressing
591
Architecture</citetitle>
596
<term>Section 2.2: <citetitle>Text Representation of
597
Addresses</citetitle></term>
598
<listitem><para/></listitem>
601
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
602
Address</citetitle></term>
603
<listitem><para/></listitem>
606
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
607
Addresses</citetitle></term>
610
The clients use IPv6 link-local addresses, which are
611
immediately usable since a link-local addresses is
612
automatically assigned to a network interfaces when it
622
RFC 4346: <citetitle>The Transport Layer Security (TLS)
623
Protocol Version 1.1</citetitle>
627
TLS 1.1 is the protocol implemented by GnuTLS.
633
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
637
The data sent to clients is binary encrypted OpenPGP data.
643
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
648
This is implemented by GnuTLS and used by this server so
649
that OpenPGP keys can be used.
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
110
<term><literal>-h</literal>, <literal>--help</literal></term>
113
show a help message and exit
119
<term><literal>-i</literal>, <literal>--interface <replaceable>
120
IF</replaceable></literal></term>
129
<term><literal>-a</literal>, <literal>--address <replaceable>
130
ADDRESS</replaceable></literal></term>
133
Address to listen for requests on
139
<term><literal>-p</literal>, <literal>--port <replaceable>
140
PORT</replaceable></literal></term>
143
Port number to receive requests on
149
<term><literal>--check</literal></term>
152
Run self-test on the server
158
<term><literal>--debug</literal></term>
167
<term><literal>--priority <replaceable>
168
PRIORITY</replaceable></literal></term>
171
GnuTLS priority string. See <citerefentry>
172
<refentrytitle>gnutls_priority_init</refentrytitle>
173
<manvolnum>3</manvolnum></citerefentry>
179
<term><literal>--servicename <replaceable>NAME</replaceable>
183
Zeroconf service name
189
<term><literal>--configdir <replaceable>DIR</replaceable>
193
Directory to search for configuration files
656
<!-- Local Variables: -->
657
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
658
<!-- time-stamp-end: "[\"']>" -->
659
<!-- time-stamp-format: "%:y-%02m-%02d" -->