67
48
<refname><command>&COMMANDNAME;</command></refname>
69
Sends encrypted passwords to authenticated mandos clients
50
Gives encrypted passwords to authenticated Mandos clients
75
56
<command>&COMMANDNAME;</command>
76
<arg choice='opt' rep='repeat'>OPTION</arg>
58
<arg choice="plain"><option>--interface
59
<replaceable>NAME</replaceable></option></arg>
60
<arg choice="plain"><option>-i
61
<replaceable>NAME</replaceable></option></arg>
65
<arg choice="plain"><option>--address
66
<replaceable>ADDRESS</replaceable></option></arg>
67
<arg choice="plain"><option>-a
68
<replaceable>ADDRESS</replaceable></option></arg>
72
<arg choice="plain"><option>--port
73
<replaceable>PORT</replaceable></option></arg>
74
<arg choice="plain"><option>-p
75
<replaceable>PORT</replaceable></option></arg>
78
<arg><option>--priority
79
<replaceable>PRIORITY</replaceable></option></arg>
81
<arg><option>--servicename
82
<replaceable>NAME</replaceable></option></arg>
84
<arg><option>--configdir
85
<replaceable>DIRECTORY</replaceable></option></arg>
87
<arg><option>--debug</option></arg>
89
<arg><option>--no-ipv6</option></arg>
92
<command>&COMMANDNAME;</command>
94
<arg choice="plain"><option>--help</option></arg>
95
<arg choice="plain"><option>-h</option></arg>
99
<command>&COMMANDNAME;</command>
100
<arg choice="plain"><option>--version</option></arg>
103
<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--check</option></arg>
80
108
<refsect1 id="description">
81
109
<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>
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<term><literal>--priority <replaceable>
150
PRIORITY</replaceable></literal></term>
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GnuTLS priority string. See <citerefentry>
154
<refentrytitle>gnutls_priority_init</refentrytitle>
155
<manvolnum>3</manvolnum></citerefentry>
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<term><literal>--servicename <replaceable>NAME</replaceable>
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Zeroconf service name
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<term><literal>--configdir <replaceable>DIR</replaceable>
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Directory to search for configuration files
111
<command>&COMMANDNAME;</command> is a server daemon which
112
handles incoming request for passwords for a pre-defined list of
113
client host computers. The Mandos server uses Zeroconf to
114
announce itself on the local network, and uses TLS to
115
communicate securely with and to authenticate the clients. The
116
Mandos server uses IPv6 to allow Mandos clients to use IPv6
117
link-local addresses, since the clients will probably not have
118
any other addresses configured (see <xref linkend="overview"/>).
119
Any authenticated client is then given the stored pre-encrypted
120
password for that specific client.
124
<refsect1 id="purpose">
125
<title>PURPOSE</title>
127
The purpose of this is to enable <emphasis>remote and unattended
128
rebooting</emphasis> of client host computer with an
129
<emphasis>encrypted root file system</emphasis>. See <xref
130
linkend="overview"/> for details.
134
<refsect1 id="options">
135
<title>OPTIONS</title>
138
<term><option>--help</option></term>
139
<term><option>-h</option></term>
142
Show a help message and exit
148
<term><option>--interface</option>
149
<replaceable>NAME</replaceable></term>
150
<term><option>-i</option>
151
<replaceable>NAME</replaceable></term>
153
<xi:include href="mandos-options.xml" xpointer="interface"/>
158
<term><option>--address
159
<replaceable>ADDRESS</replaceable></option></term>
161
<replaceable>ADDRESS</replaceable></option></term>
163
<xi:include href="mandos-options.xml" xpointer="address"/>
169
<replaceable>PORT</replaceable></option></term>
171
<replaceable>PORT</replaceable></option></term>
173
<xi:include href="mandos-options.xml" xpointer="port"/>
178
<term><option>--check</option></term>
181
Run the server’s self-tests. This includes any unit
188
<term><option>--debug</option></term>
190
<xi:include href="mandos-options.xml" xpointer="debug"/>
195
<term><option>--priority <replaceable>
196
PRIORITY</replaceable></option></term>
198
<xi:include href="mandos-options.xml" xpointer="priority"/>
203
<term><option>--servicename
204
<replaceable>NAME</replaceable></option></term>
206
<xi:include href="mandos-options.xml"
207
xpointer="servicename"/>
212
<term><option>--configdir
213
<replaceable>DIRECTORY</replaceable></option></term>
216
Directory to search for configuration files. Default is
217
<quote><literal>/etc/mandos</literal></quote>. See
218
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
219
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
220
<refentrytitle>mandos-clients.conf</refentrytitle>
221
<manvolnum>5</manvolnum></citerefentry>.
227
<term><option>--version</option></term>
230
Prints the program version and exit.
236
<term><option>--no-ipv6</option></term>
238
<xi:include href="mandos-options.xml" xpointer="ipv6"/>
244
<refsect1 id="overview">
245
<title>OVERVIEW</title>
246
<xi:include href="overview.xml"/>
248
This program is the server part. It is a normal server program
249
and will run in a normal system environment, not in an initial
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<acronym>RAM</acronym> disk environment.
254
<refsect1 id="protocol">
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<title>NETWORK PROTOCOL</title>
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The Mandos server announces itself as a Zeroconf service of type
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<quote><literal>_mandos._tcp</literal></quote>. The Mandos
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client connects to the announced address and port, and sends a
260
line of text where the first whitespace-separated field is the
261
protocol version, which currently is
262
<quote><literal>1</literal></quote>. The client and server then
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start a TLS protocol handshake with a slight quirk: the Mandos
264
server program acts as a TLS <quote>client</quote> while the
265
connecting Mandos client acts as a TLS <quote>server</quote>.
266
The Mandos client must supply an OpenPGP certificate, and the
267
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>
269
at start time) which binary blob to give the client. No other
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authentication or authorization is done by the server.
273
<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
275
<entry>Mandos Client</entry>
276
<entry>Direction</entry>
277
<entry>Mandos Server</entry>
281
<entry>Connect</entry>
282
<entry>-><!-- → --></entry>
285
<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>
291
<entry><-><!-- ⟷ --></entry>
292
<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
296
<entry>OpenPGP public key (part of TLS handshake)</entry>
297
<entry>-><!-- → --></entry>
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<entry><-<!-- ← --></entry>
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<entry>Binary blob (client will assume OpenPGP data)</entry>
306
<entry><-<!-- ← --></entry>
309
</tbody></tgroup></table>
312
<refsect1 id="checking">
313
<title>CHECKING</title>
315
The server will, by default, continually check that the clients
316
are still up. If a client has not been confirmed as being up
317
for some time, the client is assumed to be compromised and is no
318
longer eligible to receive the encrypted password. (Manual
319
intervention is required to re-enable a client.) The timeout,
320
checker program, and interval between checks can be configured
321
both globally and per client; see <citerefentry>
322
<refentrytitle>mandos-clients.conf</refentrytitle>
323
<manvolnum>5</manvolnum></citerefentry>. A client successfully
324
receiving its password will also be treated as a successful
329
<refsect1 id="logging">
330
<title>LOGGING</title>
332
The server will send log message with various severity levels to
333
<filename>/dev/log</filename>. With the
334
<option>--debug</option> option, it will log even more messages,
335
and also show them on the console.
339
<refsect1 id="exit_status">
340
<title>EXIT STATUS</title>
342
The server will exit with a non-zero exit status only when a
343
critical error is encountered.
347
<refsect1 id="environment">
348
<title>ENVIRONMENT</title>
351
<term><envar>PATH</envar></term>
354
To start the configured checker (see <xref
355
linkend="checking"/>), the server uses
356
<filename>/bin/sh</filename>, which in turn uses
357
<varname>PATH</varname> to search for matching commands if
358
an absolute path is not given. See <citerefentry>
359
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
367
<refsect1 id="files">
370
Use the <option>--configdir</option> option to change where
371
<command>&COMMANDNAME;</command> looks for its configurations
372
files. The default file names are listed here.
376
<term><filename>/etc/mandos/mandos.conf</filename></term>
379
Server-global settings. See
380
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
381
<manvolnum>5</manvolnum></citerefentry> for details.
386
<term><filename>/etc/mandos/clients.conf</filename></term>
389
List of clients and client-specific settings. See
390
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
391
<manvolnum>5</manvolnum></citerefentry> for details.
396
<term><filename>/var/run/mandos.pid</filename></term>
399
The file containing the process id of
400
<command>&COMMANDNAME;</command>.
405
<term><filename>/dev/log</filename></term>
408
The Unix domain socket to where local syslog messages are
414
<term><filename>/bin/sh</filename></term>
417
This is used to start the configured checker command for
418
each client. See <citerefentry>
419
<refentrytitle>mandos-clients.conf</refentrytitle>
420
<manvolnum>5</manvolnum></citerefentry> for details.
430
This server might, on especially fatal errors, emit a Python
431
backtrace. This could be considered a feature.
434
Currently, if a client is declared <quote>invalid</quote> due to
435
having timed out, the server does not record this fact onto
436
permanent storage. This has some security implications, see
437
<xref linkend="clients"/>.
440
There is currently no way of querying the server of the current
441
status of clients, other than analyzing its <systemitem
442
class="service">syslog</systemitem> output.
445
There is no fine-grained control over logging and debug output.
448
Debug mode is conflated with running in the foreground.
451
The console log messages do not show a time stamp.
454
This server does not check the expire time of clients’ OpenPGP
459
<refsect1 id="example">
460
<title>EXAMPLE</title>
463
Normal invocation needs no options:
466
<userinput>&COMMANDNAME;</userinput>
471
Run the server in debug mode, read configuration files from
472
the <filename>~/mandos</filename> directory, and use the
473
Zeroconf service name <quote>Test</quote> to not collide with
474
any other official Mandos server on this host:
478
<!-- do not wrap this line -->
479
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
485
Run the server normally, but only listen to one interface and
486
only on the link-local address on that interface:
490
<!-- do not wrap this line -->
491
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
497
<refsect1 id="security">
498
<title>SECURITY</title>
499
<refsect2 id="server">
500
<title>SERVER</title>
502
Running this <command>&COMMANDNAME;</command> server program
503
should not in itself present any security risk to the host
504
computer running it. The program switches to a non-root user
508
<refsect2 id="clients">
509
<title>CLIENTS</title>
511
The server only gives out its stored data to clients which
512
does have the OpenPGP key of the stored fingerprint. This is
513
guaranteed by the fact that the client sends its OpenPGP
514
public key in the TLS handshake; this ensures it to be
515
genuine. The server computes the fingerprint of the key
516
itself and looks up the fingerprint in its list of
517
clients. The <filename>clients.conf</filename> file (see
518
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
519
<manvolnum>5</manvolnum></citerefentry>)
520
<emphasis>must</emphasis> be made non-readable by anyone
521
except the user starting the server (usually root).
524
As detailed in <xref linkend="checking"/>, the status of all
525
client computers will continually be checked and be assumed
526
compromised if they are gone for too long.
529
If a client is compromised, its downtime should be duly noted
530
by the server which would therefore declare the client
531
invalid. But if the server was ever restarted, it would
532
re-read its client list from its configuration file and again
533
regard all clients therein as valid, and hence eligible to
534
receive their passwords. Therefore, be careful when
535
restarting servers if it is suspected that a client has, in
536
fact, been compromised by parties who may now be running a
537
fake Mandos client with the keys from the non-encrypted
538
initial <acronym>RAM</acronym> image of the client host. What
539
should be done in that case (if restarting the server program
540
really is necessary) is to stop the server program, edit the
541
configuration file to omit any suspect clients, and restart
545
For more details on client-side security, see
546
<citerefentry><refentrytitle>mandos-client</refentrytitle>
547
<manvolnum>8mandos</manvolnum></citerefentry>.
552
<refsect1 id="see_also">
553
<title>SEE ALSO</title>
556
<refentrytitle>mandos-clients.conf</refentrytitle>
557
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
558
<refentrytitle>mandos.conf</refentrytitle>
559
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
560
<refentrytitle>mandos-client</refentrytitle>
561
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
562
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
568
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
572
Zeroconf is the network protocol standard used by clients
573
for finding this Mandos server on the local network.
579
<ulink url="http://www.avahi.org/">Avahi</ulink>
583
Avahi is the library this server calls to implement
584
Zeroconf service announcements.
590
<ulink url="http://www.gnu.org/software/gnutls/"
595
GnuTLS is the library this server uses to implement TLS for
596
communicating securely with the client, and at the same time
597
confidently get the client’s public OpenPGP key.
603
RFC 4291: <citetitle>IP Version 6 Addressing
604
Architecture</citetitle>
609
<term>Section 2.2: <citetitle>Text Representation of
610
Addresses</citetitle></term>
611
<listitem><para/></listitem>
614
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
615
Address</citetitle></term>
616
<listitem><para/></listitem>
619
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
620
Addresses</citetitle></term>
623
The clients use IPv6 link-local addresses, which are
624
immediately usable since a link-local addresses is
625
automatically assigned to a network interfaces when it
635
RFC 4346: <citetitle>The Transport Layer Security (TLS)
636
Protocol Version 1.1</citetitle>
640
TLS 1.1 is the protocol implemented by GnuTLS.
646
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
650
The data sent to clients is binary encrypted OpenPGP data.
656
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
661
This is implemented by GnuTLS and used by this server so
662
that OpenPGP keys can be used.
669
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