67
46
<refname><command>&COMMANDNAME;</command></refname>
69
Sends encrypted passwords to authenticated mandos clients
48
Gives encrypted passwords to authenticated Mandos clients
75
54
<command>&COMMANDNAME;</command>
76
<arg choice='opt' rep='repeat'>OPTION</arg>
56
<arg choice="plain"><option>--interface
57
<replaceable>NAME</replaceable></option></arg>
58
<arg choice="plain"><option>-i
59
<replaceable>NAME</replaceable></option></arg>
63
<arg choice="plain"><option>--address
64
<replaceable>ADDRESS</replaceable></option></arg>
65
<arg choice="plain"><option>-a
66
<replaceable>ADDRESS</replaceable></option></arg>
70
<arg choice="plain"><option>--port
71
<replaceable>PORT</replaceable></option></arg>
72
<arg choice="plain"><option>-p
73
<replaceable>PORT</replaceable></option></arg>
76
<arg><option>--priority
77
<replaceable>PRIORITY</replaceable></option></arg>
79
<arg><option>--servicename
80
<replaceable>NAME</replaceable></option></arg>
82
<arg><option>--configdir
83
<replaceable>DIRECTORY</replaceable></option></arg>
85
<arg><option>--debug</option></arg>
88
<command>&COMMANDNAME;</command>
90
<arg choice="plain"><option>--help</option></arg>
91
<arg choice="plain"><option>-h</option></arg>
95
<command>&COMMANDNAME;</command>
96
<arg choice="plain"><option>--version</option></arg>
99
<command>&COMMANDNAME;</command>
100
<arg choice="plain"><option>--check</option></arg>
80
104
<refsect1 id="description">
81
105
<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
107
<command>&COMMANDNAME;</command> is a server daemon which
108
handles incoming request for passwords for a pre-defined list of
109
client host computers. The Mandos server uses Zeroconf to
110
announce itself on the local network, and uses TLS to
111
communicate securely with and to authenticate the clients. The
112
Mandos server uses IPv6 to allow Mandos clients to use IPv6
113
link-local addresses, since the clients will probably not have
114
any other addresses configured (see <xref linkend="overview"/>).
115
Any authenticated client is then given the stored pre-encrypted
116
password for that specific client.
120
<refsect1 id="purpose">
121
<title>PURPOSE</title>
123
The purpose of this is to enable <emphasis>remote and unattended
124
rebooting</emphasis> of client host computer with an
125
<emphasis>encrypted root file system</emphasis>. See <xref
126
linkend="overview"/> for details.
130
<refsect1 id="options">
131
<title>OPTIONS</title>
134
<term><option>--help</option></term>
135
<term><option>-h</option></term>
138
Show a help message and exit
144
<term><option>--interface</option>
145
<replaceable>NAME</replaceable></term>
146
<term><option>-i</option>
147
<replaceable>NAME</replaceable></term>
149
<xi:include href="mandos-options.xml" xpointer="interface"/>
154
<term><option>--address
155
<replaceable>ADDRESS</replaceable></option></term>
157
<replaceable>ADDRESS</replaceable></option></term>
159
<xi:include href="mandos-options.xml" xpointer="address"/>
165
<replaceable>PORT</replaceable></option></term>
167
<replaceable>PORT</replaceable></option></term>
169
<xi:include href="mandos-options.xml" xpointer="port"/>
174
<term><option>--check</option></term>
177
Run the server’s self-tests. This includes any unit
184
<term><option>--debug</option></term>
186
<xi:include href="mandos-options.xml" xpointer="debug"/>
191
<term><option>--priority <replaceable>
192
PRIORITY</replaceable></option></term>
194
<xi:include href="mandos-options.xml" xpointer="priority"/>
199
<term><option>--servicename
200
<replaceable>NAME</replaceable></option></term>
202
<xi:include href="mandos-options.xml"
203
xpointer="servicename"/>
208
<term><option>--configdir
209
<replaceable>DIRECTORY</replaceable></option></term>
212
Directory to search for configuration files. Default is
213
<quote><literal>/etc/mandos</literal></quote>. See
214
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
215
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
216
<refentrytitle>mandos-clients.conf</refentrytitle>
217
<manvolnum>5</manvolnum></citerefentry>.
223
<term><option>--version</option></term>
226
Prints the program version and exit.
233
<refsect1 id="overview">
234
<title>OVERVIEW</title>
235
<xi:include href="overview.xml"/>
237
This program is the server part. It is a normal server program
238
and will run in a normal system environment, not in an initial
239
<acronym>RAM</acronym> disk environment.
243
<refsect1 id="protocol">
244
<title>NETWORK PROTOCOL</title>
246
The Mandos server announces itself as a Zeroconf service of type
247
<quote><literal>_mandos._tcp</literal></quote>. The Mandos
248
client connects to the announced address and port, and sends a
249
line of text where the first whitespace-separated field is the
250
protocol version, which currently is
251
<quote><literal>1</literal></quote>. The client and server then
252
start a TLS protocol handshake with a slight quirk: the Mandos
253
server program acts as a TLS <quote>client</quote> while the
254
connecting Mandos client acts as a TLS <quote>server</quote>.
255
The Mandos client must supply an OpenPGP certificate, and the
256
fingerprint of this certificate is used by the Mandos server to
257
look up (in a list read from <filename>clients.conf</filename>
258
at start time) which binary blob to give the client. No other
259
authentication or authorization is done by the server.
262
<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
264
<entry>Mandos Client</entry>
265
<entry>Direction</entry>
266
<entry>Mandos Server</entry>
270
<entry>Connect</entry>
271
<entry>-><!-- → --></entry>
274
<entry><quote><literal>1\r\n</literal></quote></entry>
275
<entry>-><!-- → --></entry>
278
<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
280
<entry><-><!-- ⟷ --></entry>
281
<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
285
<entry>OpenPGP public key (part of TLS handshake)</entry>
286
<entry>-><!-- → --></entry>
290
<entry><-<!-- ← --></entry>
291
<entry>Binary blob (client will assume OpenPGP data)</entry>
295
<entry><-<!-- ← --></entry>
298
</tbody></tgroup></table>
301
<refsect1 id="checking">
302
<title>CHECKING</title>
304
The server will, by default, continually check that the clients
305
are still up. If a client has not been confirmed as being up
306
for some time, the client is assumed to be compromised and is no
307
longer eligible to receive the encrypted password. The timeout,
308
checker program, and interval between checks can be configured
309
both globally and per client; see <citerefentry>
310
<refentrytitle>mandos-clients.conf</refentrytitle>
311
<manvolnum>5</manvolnum></citerefentry>.
315
<refsect1 id="logging">
316
<title>LOGGING</title>
318
The server will send log message with various severity levels to
319
<filename>/dev/log</filename>. With the
320
<option>--debug</option> option, it will log even more messages,
321
and also show them on the console.
325
<refsect1 id="exit_status">
326
<title>EXIT STATUS</title>
328
The server will exit with a non-zero exit status only when a
329
critical error is encountered.
333
<refsect1 id="environment">
334
<title>ENVIRONMENT</title>
337
<term><envar>PATH</envar></term>
340
To start the configured checker (see <xref
341
linkend="checking"/>), the server uses
342
<filename>/bin/sh</filename>, which in turn uses
343
<varname>PATH</varname> to search for matching commands if
344
an absolute path is not given. See <citerefentry>
345
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
356
Use the <option>--configdir</option> option to change where
357
<command>&COMMANDNAME;</command> looks for its configurations
358
files. The default file names are listed here.
362
<term><filename>/etc/mandos/mandos.conf</filename></term>
365
Server-global settings. See
366
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
367
<manvolnum>5</manvolnum></citerefentry> for details.
372
<term><filename>/etc/mandos/clients.conf</filename></term>
375
List of clients and client-specific settings. See
376
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
377
<manvolnum>5</manvolnum></citerefentry> for details.
382
<term><filename>/var/run/mandos/mandos.pid</filename></term>
385
The file containing the process id of
386
<command>&COMMANDNAME;</command>.
391
<term><filename>/dev/log</filename></term>
394
The Unix domain socket to where local syslog messages are
400
<term><filename>/bin/sh</filename></term>
403
This is used to start the configured checker command for
404
each client. See <citerefentry>
405
<refentrytitle>mandos-clients.conf</refentrytitle>
406
<manvolnum>5</manvolnum></citerefentry> for details.
416
This server might, on especially fatal errors, emit a Python
417
backtrace. This could be considered a feature.
420
Currently, if a client is declared <quote>invalid</quote> due to
421
having timed out, the server does not record this fact onto
422
permanent storage. This has some security implications, see
423
<xref linkend="CLIENTS"/>.
426
There is currently no way of querying the server of the current
427
status of clients, other than analyzing its <systemitem
428
class="service">syslog</systemitem> output.
431
There is no fine-grained control over logging and debug output.
434
Debug mode is conflated with running in the foreground.
437
The console log messages does not show a timestamp.
441
<refsect1 id="example">
442
<title>EXAMPLE</title>
445
Normal invocation needs no options:
448
<userinput>&COMMANDNAME;</userinput>
453
Run the server in debug mode, read configuration files from
454
the <filename>~/mandos</filename> directory, and use the
455
Zeroconf service name <quote>Test</quote> to not collide with
456
any other official Mandos server on this host:
460
<!-- do not wrap this line -->
461
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
467
Run the server normally, but only listen to one interface and
468
only on the link-local address on that interface:
472
<!-- do not wrap this line -->
473
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
479
<refsect1 id="security">
480
<title>SECURITY</title>
481
<refsect2 id="SERVER">
482
<title>SERVER</title>
484
Running this <command>&COMMANDNAME;</command> server program
485
should not in itself present any security risk to the host
486
computer running it. The program does not need any special
487
privileges to run, and is designed to run as a non-root user.
490
<refsect2 id="CLIENTS">
491
<title>CLIENTS</title>
493
The server only gives out its stored data to clients which
494
does have the OpenPGP key of the stored fingerprint. This is
495
guaranteed by the fact that the client sends its OpenPGP
496
public key in the TLS handshake; this ensures it to be
497
genuine. The server computes the fingerprint of the key
498
itself and looks up the fingerprint in its list of
499
clients. The <filename>clients.conf</filename> file (see
500
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
501
<manvolnum>5</manvolnum></citerefentry>)
502
<emphasis>must</emphasis> be made non-readable by anyone
503
except the user running the server.
506
As detailed in <xref linkend="checking"/>, the status of all
507
client computers will continually be checked and be assumed
508
compromised if they are gone for too long.
511
If a client is compromised, its downtime should be duly noted
512
by the server which would therefore declare the client
513
invalid. But if the server was ever restarted, it would
514
re-read its client list from its configuration file and again
515
regard all clients therein as valid, and hence eligible to
516
receive their passwords. Therefore, be careful when
517
restarting servers if it is suspected that a client has, in
518
fact, been compromised by parties who may now be running a
519
fake Mandos client with the keys from the non-encrypted
520
initial <acronym>RAM</acronym> image of the client host. What
521
should be done in that case (if restarting the server program
522
really is necessary) is to stop the server program, edit the
523
configuration file to omit any suspect clients, and restart
527
For more details on client-side security, see
528
<citerefentry><refentrytitle>password-request</refentrytitle>
529
<manvolnum>8mandos</manvolnum></citerefentry>.
534
<refsect1 id="see_also">
535
<title>SEE ALSO</title>
538
<refentrytitle>mandos-clients.conf</refentrytitle>
539
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
540
<refentrytitle>mandos.conf</refentrytitle>
541
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
542
<refentrytitle>password-request</refentrytitle>
543
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
544
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
550
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
554
Zeroconf is the network protocol standard used by clients
555
for finding this Mandos server on the local network.
561
<ulink url="http://www.avahi.org/">Avahi</ulink>
565
Avahi is the library this server calls to implement
566
Zeroconf service announcements.
572
<ulink url="http://www.gnu.org/software/gnutls/"
577
GnuTLS is the library this server uses to implement TLS for
578
communicating securely with the client, and at the same time
579
confidently get the client’s public OpenPGP key.
585
RFC 4291: <citetitle>IP Version 6 Addressing
586
Architecture</citetitle>
591
<term>Section 2.2: <citetitle>Text Representation of
592
Addresses</citetitle></term>
593
<listitem><para/></listitem>
596
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
597
Address</citetitle></term>
598
<listitem><para/></listitem>
601
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
602
Addresses</citetitle></term>
605
The clients use IPv6 link-local addresses, which are
606
immediately usable since a link-local addresses is
607
automatically assigned to a network interfaces when it
617
RFC 4346: <citetitle>The Transport Layer Security (TLS)
618
Protocol Version 1.1</citetitle>
622
TLS 1.1 is the protocol implemented by GnuTLS.
628
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
632
The data sent to clients is binary encrypted OpenPGP data.
638
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
643
This is implemented by GnuTLS and used by this server so
644
that OpenPGP keys can be used.
651
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652
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653
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