67
68
<refname><command>&COMMANDNAME;</command></refname>
69
Sends encrypted passwords to authenticated mandos clients
70
Gives encrypted passwords to authenticated Mandos clients
75
76
<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>
77
<arg>--interface<arg choice="plain">NAME</arg></arg>
78
<arg>--address<arg choice="plain">ADDRESS</arg></arg>
79
<arg>--port<arg choice="plain">PORT</arg></arg>
80
<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
81
<arg>--servicename<arg choice="plain">NAME</arg></arg>
82
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
86
<command>&COMMANDNAME;</command>
87
<arg>-i<arg choice="plain">NAME</arg></arg>
88
<arg>-a<arg choice="plain">ADDRESS</arg></arg>
89
<arg>-p<arg choice="plain">PORT</arg></arg>
90
<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
91
<arg>--servicename<arg choice="plain">NAME</arg></arg>
92
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
96
<command>&COMMANDNAME;</command>
98
<arg choice="plain">-h</arg>
99
<arg choice="plain">--help</arg>
103
<command>&COMMANDNAME;</command>
104
<arg choice="plain">--version</arg>
107
<command>&COMMANDNAME;</command>
108
<arg choice="plain">--check</arg>
98
112
<refsect1 id="description">
99
113
<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
115
<command>&COMMANDNAME;</command> is a server daemon which
116
handles incoming request for passwords for a pre-defined list of
117
client host computers. The Mandos server uses Zeroconf to
118
announce itself on the local network, and uses TLS to
119
communicate securely with and to authenticate the clients. The
120
Mandos server uses IPv6 to allow Mandos clients to use IPv6
121
link-local addresses, since the clients will probably not have
122
any other addresses configured (see <xref linkend="overview"/>).
123
Any authenticated client is then given the stored pre-encrypted
124
password for that specific client.
129
<refsect1 id="purpose">
130
<title>PURPOSE</title>
133
The purpose of this is to enable <emphasis>remote and unattended
134
rebooting</emphasis> of client host computer with an
135
<emphasis>encrypted root file system</emphasis>. See <xref
136
linkend="overview"/> for details.
141
<refsect1 id="options">
142
<title>OPTIONS</title>
110
<term><literal>-h</literal>, <literal>--help</literal></term>
146
<term><option>-h</option></term>
147
<term><option>--help</option></term>
113
show a help message and exit
150
Show a help message and exit
119
<term><literal>-i</literal>, <literal>--interface <replaceable>
120
IF</replaceable></literal></term>
156
<term><option>-i</option>
157
<replaceable>NAME</replaceable></term>
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<term><option>--interface</option>
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<replaceable>NAME</replaceable></term>
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<xi:include href="mandos-options.xml" xpointer="interface"/>
129
166
<term><literal>-a</literal>, <literal>--address <replaceable>
130
167
ADDRESS</replaceable></literal></term>
133
Address to listen for requests on
169
<xi:include href="mandos-options.xml" xpointer="address"/>
139
174
<term><literal>-p</literal>, <literal>--port <replaceable>
140
175
PORT</replaceable></literal></term>
143
Port number to receive requests on
177
<xi:include href="mandos-options.xml" xpointer="port"/>
149
182
<term><literal>--check</literal></term>
152
Run self-test on the server
185
Run the server’s self-tests. This includes any unit
158
192
<term><literal>--debug</literal></term>
194
<xi:include href="mandos-options.xml" xpointer="debug"/>
199
231
<term><literal>--version</literal></term>
202
Prints the program version
234
Prints the program version and exit.
241
<refsect1 id="overview">
242
<title>OVERVIEW</title>
243
<xi:include href="overview.xml"/>
245
This program is the server part. It is a normal server program
246
and will run in a normal system environment, not in an initial
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RAM disk environment.
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<refsect1 id="protocol">
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<title>NETWORK PROTOCOL</title>
254
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
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line of text where the first whitespace-separated field is the
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protocol version, which currently is
259
<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
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server program acts as a TLS <quote>client</quote> while the
262
connecting Mandos client acts as a TLS <quote>server</quote>.
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The Mandos client must supply an OpenPGP certificate, and the
264
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>
266
at start time) which binary blob to give the client. No other
267
authentication or authorization is done by the server.
270
<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
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<entry>Mandos Client</entry>
273
<entry>Direction</entry>
274
<entry>Mandos Server</entry>
278
<entry>Connect</entry>
279
<entry>-><!-- → --></entry>
282
<entry><quote><literal>1\r\n</literal></quote></entry>
283
<entry>-><!-- → --></entry>
286
<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
288
<entry><-><!-- ⟷ --></entry>
289
<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
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<entry>OpenPGP public key (part of TLS handshake)</entry>
294
<entry>-><!-- → --></entry>
298
<entry><-<!-- ← --></entry>
299
<entry>Binary blob (client will assume OpenPGP data)</entry>
303
<entry><-<!-- ← --></entry>
306
</tbody></tgroup></table>
309
<refsect1 id="checking">
310
<title>CHECKING</title>
312
The server will, by default, continually check that the clients
313
are still up. If a client has not been confirmed as being up
314
for some time, the client is assumed to be compromised and is no
315
longer eligible to receive the encrypted password. The timeout,
316
checker program, and interval between checks can be configured
317
both globally and per client; see <citerefentry>
318
<refentrytitle>mandos-clients.conf</refentrytitle>
319
<manvolnum>5</manvolnum></citerefentry>.
323
<refsect1 id="logging">
324
<title>LOGGING</title>
326
The server will send log message with various severity levels to
327
<filename>/dev/log</filename>. With the
328
<option>--debug</option> option, it will log even more messages,
329
and also show them on the console.
333
<refsect1 id="exit_status">
334
<title>EXIT STATUS</title>
336
The server will exit with a non-zero exit status only when a
337
critical error is encountered.
341
<refsect1 id="environment">
342
<title>ENVIRONMENT</title>
345
<term><envar>PATH</envar></term>
348
To start the configured checker (see <xref
349
linkend="checking"/>), the server uses
350
<filename>/bin/sh</filename>, which in turn uses
351
<varname>PATH</varname> to search for matching commands if
352
an absolute path is not given. See <citerefentry>
353
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
364
Use the <option>--configdir</option> option to change where
365
<command>&COMMANDNAME;</command> looks for its configurations
366
files. The default file names are listed here.
370
<term><filename>/etc/mandos/mandos.conf</filename></term>
373
Server-global settings. See
374
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
375
<manvolnum>5</manvolnum></citerefentry> for details.
380
<term><filename>/etc/mandos/clients.conf</filename></term>
383
List of clients and client-specific settings. See
384
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
385
<manvolnum>5</manvolnum></citerefentry> for details.
390
<term><filename>/var/run/mandos/mandos.pid</filename></term>
393
The file containing the process id of
394
<command>&COMMANDNAME;</command>.
399
<term><filename>/dev/log</filename></term>
402
The Unix domain socket to where local syslog messages are
408
<term><filename>/bin/sh</filename></term>
411
This is used to start the configured checker command for
412
each client. See <citerefentry>
413
<refentrytitle>mandos-clients.conf</refentrytitle>
414
<manvolnum>5</manvolnum></citerefentry> for details.
424
This server might, on especially fatal errors, emit a Python
425
backtrace. This could be considered a feature.
428
Currently, if a client is declared <quote>invalid</quote> due to
429
having timed out, the server does not record this fact onto
430
permanent storage. This has some security implications, see
431
<xref linkend="CLIENTS"/>.
434
There is currently no way of querying the server of the current
435
status of clients, other than analyzing its <systemitem
436
class="service">syslog</systemitem> output.
439
There is no fine-grained control over logging and debug output.
442
Debug mode is conflated with running in the foreground.
445
The console log messages does not show a timestamp.
449
<refsect1 id="example">
450
<title>EXAMPLE</title>
453
Normal invocation needs no options:
456
<userinput>&COMMANDNAME;</userinput>
461
Run the server in debug mode, read configuration files from
462
the <filename>~/mandos</filename> directory, and use the
463
Zeroconf service name <quote>Test</quote> to not collide with
464
any other official Mandos server on this host:
468
<!-- do not wrap this line -->
469
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
475
Run the server normally, but only listen to one interface and
476
only on the link-local address on that interface:
480
<!-- do not wrap this line -->
481
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
487
<refsect1 id="security">
488
<title>SECURITY</title>
489
<refsect2 id="SERVER">
490
<title>SERVER</title>
492
Running this <command>&COMMANDNAME;</command> server program
493
should not in itself present any security risk to the host
494
computer running it. The program does not need any special
495
privileges to run, and is designed to run as a non-root user.
498
<refsect2 id="CLIENTS">
499
<title>CLIENTS</title>
501
The server only gives out its stored data to clients which
502
does have the OpenPGP key of the stored fingerprint. This is
503
guaranteed by the fact that the client sends its OpenPGP
504
public key in the TLS handshake; this ensures it to be
505
genuine. The server computes the fingerprint of the key
506
itself and looks up the fingerprint in its list of
507
clients. The <filename>clients.conf</filename> file (see
508
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
509
<manvolnum>5</manvolnum></citerefentry>)
510
<emphasis>must</emphasis> be made non-readable by anyone
511
except the user running the server.
514
As detailed in <xref linkend="checking"/>, the status of all
515
client computers will continually be checked and be assumed
516
compromised if they are gone for too long.
519
If a client is compromised, its downtime should be duly noted
520
by the server which would therefore declare the client
521
invalid. But if the server was ever restarted, it would
522
re-read its client list from its configuration file and again
523
regard all clients therein as valid, and hence eligible to
524
receive their passwords. Therefore, be careful when
525
restarting servers if it is suspected that a client has, in
526
fact, been compromised by parties who may now be running a
527
fake Mandos client with the keys from the non-encrypted
528
initial RAM image of the client host. What should be done in
529
that case (if restarting the server program really is
530
necessary) is to stop the server program, edit the
531
configuration file to omit any suspect clients, and restart
535
For more details on client-side security, see
536
<citerefentry><refentrytitle>password-request</refentrytitle>
537
<manvolnum>8mandos</manvolnum></citerefentry>.
542
<refsect1 id="see_also">
543
<title>SEE ALSO</title>
546
<refentrytitle>mandos-clients.conf</refentrytitle>
547
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
548
<refentrytitle>mandos.conf</refentrytitle>
549
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
550
<refentrytitle>password-request</refentrytitle>
551
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
552
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
558
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
562
Zeroconf is the network protocol standard used by clients
563
for finding this Mandos server on the local network.
569
<ulink url="http://www.avahi.org/">Avahi</ulink>
573
Avahi is the library this server calls to implement
574
Zeroconf service announcements.
580
<ulink url="http://www.gnu.org/software/gnutls/"
585
GnuTLS is the library this server uses to implement TLS for
586
communicating securely with the client, and at the same time
587
confidently get the client’s public OpenPGP key.
593
RFC 4291: <citetitle>IP Version 6 Addressing
594
Architecture</citetitle>
599
<term>Section 2.2: <citetitle>Text Representation of
600
Addresses</citetitle></term>
601
<listitem><para/></listitem>
604
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
605
Address</citetitle></term>
606
<listitem><para/></listitem>
609
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
610
Addresses</citetitle></term>
613
The clients use IPv6 link-local addresses, which are
614
immediately usable since a link-local addresses is
615
automatically assigned to a network interfaces when it
625
RFC 4346: <citetitle>The Transport Layer Security (TLS)
626
Protocol Version 1.1</citetitle>
630
TLS 1.1 is the protocol implemented by GnuTLS.
636
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
640
The data sent to clients is binary encrypted OpenPGP data.
646
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
651
This is implemented by GnuTLS and used by this server so
652
that OpenPGP keys can be used.
659
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660
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