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' rep='repeat'>OPTION</arg>
78
<arg choice="plain"><option>--interface
79
<replaceable>NAME</replaceable></option></arg>
80
<arg choice="plain"><option>-i
81
<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>--address
86
<replaceable>ADDRESS</replaceable></option></arg>
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<arg choice="plain"><option>-a
88
<replaceable>ADDRESS</replaceable></option></arg>
92
<arg choice="plain"><option>--port
93
<replaceable>PORT</replaceable></option></arg>
94
<arg choice="plain"><option>-p
95
<replaceable>PORT</replaceable></option></arg>
98
<arg><option>--priority
99
<replaceable>PRIORITY</replaceable></option></arg>
101
<arg><option>--servicename
102
<replaceable>NAME</replaceable></option></arg>
104
<arg><option>--configdir
105
<replaceable>DIRECTORY</replaceable></option></arg>
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<arg><option>--debug</option></arg>
110
<command>&COMMANDNAME;</command>
112
<arg choice="plain"><option>--help</option></arg>
113
<arg choice="plain"><option>-h</option></arg>
117
<command>&COMMANDNAME;</command>
118
<arg choice="plain"><option>--version</option></arg>
121
<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--check</option></arg>
80
126
<refsect1 id="description">
81
127
<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
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<command>&COMMANDNAME;</command> is a server daemon which
130
handles incoming request for passwords for a pre-defined list of
131
client host computers. The Mandos server uses Zeroconf to
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announce itself on the local network, and uses TLS to
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communicate securely with and to authenticate the clients. The
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Mandos server uses IPv6 to allow Mandos clients to use IPv6
135
link-local addresses, since the clients will probably not have
136
any other addresses configured (see <xref linkend="overview"/>).
137
Any authenticated client is then given the stored pre-encrypted
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password for that specific client.
143
<refsect1 id="purpose">
144
<title>PURPOSE</title>
147
The purpose of this is to enable <emphasis>remote and unattended
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rebooting</emphasis> of client host computer with an
149
<emphasis>encrypted root file system</emphasis>. See <xref
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linkend="overview"/> for details.
155
<refsect1 id="options">
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<title>OPTIONS</title>
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<term><literal>-h</literal>, <literal>--help</literal></term>
160
<term><option>-h</option></term>
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<term><option>--help</option></term>
95
show a help message and exit
164
Show a help message and exit
101
<term><literal>-i</literal>, <literal>--interface <replaceable>
102
IF</replaceable></literal></term>
170
<term><option>-i</option>
171
<replaceable>NAME</replaceable></term>
172
<term><option>--interface</option>
173
<replaceable>NAME</replaceable></term>
175
<xi:include href="mandos-options.xml" xpointer="interface"/>
111
180
<term><literal>-a</literal>, <literal>--address <replaceable>
112
181
ADDRESS</replaceable></literal></term>
115
Address to listen for requests on
183
<xi:include href="mandos-options.xml" xpointer="address"/>
121
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<term><literal>-p</literal>, <literal>--port <replaceable>
122
189
PORT</replaceable></literal></term>
125
Port number to receive requests on
191
<xi:include href="mandos-options.xml" xpointer="port"/>
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196
<term><literal>--check</literal></term>
134
Run self-test on the server
199
Run the server’s self-tests. This includes any unit
140
206
<term><literal>--debug</literal></term>
208
<xi:include href="mandos-options.xml" xpointer="debug"/>
149
213
<term><literal>--priority <replaceable>
150
214
PRIORITY</replaceable></literal></term>
153
GnuTLS priority string. See <citerefentry>
154
<refentrytitle>gnutls_priority_init</refentrytitle>
155
<manvolnum>3</manvolnum></citerefentry>
216
<xi:include href="mandos-options.xml" xpointer="priority"/>
161
221
<term><literal>--servicename <replaceable>NAME</replaceable>
162
222
</literal></term>
165
Zeroconf service name
224
<xi:include href="mandos-options.xml"
225
xpointer="servicename"/>
171
230
<term><literal>--configdir <replaceable>DIR</replaceable>
172
231
</literal></term>
175
Directory to search for configuration files
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Directory to search for configuration files. Default is
235
<quote><literal>/etc/mandos</literal></quote>. See
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<citerefentry><refentrytitle>mandos.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
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<refentrytitle>mandos-clients.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>.
245
<term><literal>--version</literal></term>
248
Prints the program version and exit.
255
<refsect1 id="overview">
256
<title>OVERVIEW</title>
257
<xi:include href="overview.xml"/>
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This program is the server part. It is a normal server program
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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>
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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
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line of text where the first whitespace-separated field is the
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protocol version, which currently is
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<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
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connecting Mandos client acts as a TLS <quote>server</quote>.
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The Mandos client must supply an OpenPGP certificate, and the
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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>
280
at start time) which binary blob to give the client. No other
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authentication or authorization is done by the server.
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<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
286
<entry>Mandos Client</entry>
287
<entry>Direction</entry>
288
<entry>Mandos Server</entry>
292
<entry>Connect</entry>
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<entry>-><!-- → --></entry>
296
<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>
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<entry><-><!-- ⟷ --></entry>
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<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
307
<entry>OpenPGP public key (part of TLS handshake)</entry>
308
<entry>-><!-- → --></entry>
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<entry><-<!-- ← --></entry>
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<entry>Binary blob (client will assume OpenPGP data)</entry>
317
<entry><-<!-- ← --></entry>
320
</tbody></tgroup></table>
323
<refsect1 id="checking">
324
<title>CHECKING</title>
326
The server will, by default, continually check that the clients
327
are still up. If a client has not been confirmed as being up
328
for some time, the client is assumed to be compromised and is no
329
longer eligible to receive the encrypted password. The timeout,
330
checker program, and interval between checks can be configured
331
both globally and per client; see <citerefentry>
332
<refentrytitle>mandos-clients.conf</refentrytitle>
333
<manvolnum>5</manvolnum></citerefentry>.
337
<refsect1 id="logging">
338
<title>LOGGING</title>
340
The server will send log message with various severity levels to
341
<filename>/dev/log</filename>. With the
342
<option>--debug</option> option, it will log even more messages,
343
and also show them on the console.
347
<refsect1 id="exit_status">
348
<title>EXIT STATUS</title>
350
The server will exit with a non-zero exit status only when a
351
critical error is encountered.
355
<refsect1 id="environment">
356
<title>ENVIRONMENT</title>
359
<term><envar>PATH</envar></term>
362
To start the configured checker (see <xref
363
linkend="checking"/>), the server uses
364
<filename>/bin/sh</filename>, which in turn uses
365
<varname>PATH</varname> to search for matching commands if
366
an absolute path is not given. See <citerefentry>
367
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
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Use the <option>--configdir</option> option to change where
379
<command>&COMMANDNAME;</command> looks for its configurations
380
files. The default file names are listed here.
384
<term><filename>/etc/mandos/mandos.conf</filename></term>
387
Server-global settings. See
388
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
389
<manvolnum>5</manvolnum></citerefentry> for details.
394
<term><filename>/etc/mandos/clients.conf</filename></term>
397
List of clients and client-specific settings. See
398
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
399
<manvolnum>5</manvolnum></citerefentry> for details.
404
<term><filename>/var/run/mandos/mandos.pid</filename></term>
407
The file containing the process id of
408
<command>&COMMANDNAME;</command>.
413
<term><filename>/dev/log</filename></term>
416
The Unix domain socket to where local syslog messages are
422
<term><filename>/bin/sh</filename></term>
425
This is used to start the configured checker command for
426
each client. See <citerefentry>
427
<refentrytitle>mandos-clients.conf</refentrytitle>
428
<manvolnum>5</manvolnum></citerefentry> for details.
438
This server might, on especially fatal errors, emit a Python
439
backtrace. This could be considered a feature.
442
Currently, if a client is declared <quote>invalid</quote> due to
443
having timed out, the server does not record this fact onto
444
permanent storage. This has some security implications, see
445
<xref linkend="CLIENTS"/>.
448
There is currently no way of querying the server of the current
449
status of clients, other than analyzing its <systemitem
450
class="service">syslog</systemitem> output.
453
There is no fine-grained control over logging and debug output.
456
Debug mode is conflated with running in the foreground.
459
The console log messages does not show a timestamp.
463
<refsect1 id="example">
464
<title>EXAMPLE</title>
467
Normal invocation needs no options:
470
<userinput>&COMMANDNAME;</userinput>
475
Run the server in debug mode, read configuration files from
476
the <filename>~/mandos</filename> directory, and use the
477
Zeroconf service name <quote>Test</quote> to not collide with
478
any other official Mandos server on this host:
482
<!-- do not wrap this line -->
483
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
489
Run the server normally, but only listen to one interface and
490
only on the link-local address on that interface:
494
<!-- do not wrap this line -->
495
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
501
<refsect1 id="security">
502
<title>SECURITY</title>
503
<refsect2 id="SERVER">
504
<title>SERVER</title>
506
Running this <command>&COMMANDNAME;</command> server program
507
should not in itself present any security risk to the host
508
computer running it. The program does not need any special
509
privileges to run, and is designed to run as a non-root user.
512
<refsect2 id="CLIENTS">
513
<title>CLIENTS</title>
515
The server only gives out its stored data to clients which
516
does have the OpenPGP key of the stored fingerprint. This is
517
guaranteed by the fact that the client sends its OpenPGP
518
public key in the TLS handshake; this ensures it to be
519
genuine. The server computes the fingerprint of the key
520
itself and looks up the fingerprint in its list of
521
clients. The <filename>clients.conf</filename> file (see
522
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
523
<manvolnum>5</manvolnum></citerefentry>)
524
<emphasis>must</emphasis> be made non-readable by anyone
525
except the user running the server.
528
As detailed in <xref linkend="checking"/>, the status of all
529
client computers will continually be checked and be assumed
530
compromised if they are gone for too long.
533
If a client is compromised, its downtime should be duly noted
534
by the server which would therefore declare the client
535
invalid. But if the server was ever restarted, it would
536
re-read its client list from its configuration file and again
537
regard all clients therein as valid, and hence eligible to
538
receive their passwords. Therefore, be careful when
539
restarting servers if it is suspected that a client has, in
540
fact, been compromised by parties who may now be running a
541
fake Mandos client with the keys from the non-encrypted
542
initial RAM image of the client host. What should be done in
543
that case (if restarting the server program really is
544
necessary) is to stop the server program, edit the
545
configuration file to omit any suspect clients, and restart
549
For more details on client-side security, see
550
<citerefentry><refentrytitle>password-request</refentrytitle>
551
<manvolnum>8mandos</manvolnum></citerefentry>.
556
<refsect1 id="see_also">
557
<title>SEE ALSO</title>
560
<refentrytitle>mandos-clients.conf</refentrytitle>
561
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
562
<refentrytitle>mandos.conf</refentrytitle>
563
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
564
<refentrytitle>password-request</refentrytitle>
565
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
566
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
572
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
576
Zeroconf is the network protocol standard used by clients
577
for finding this Mandos server on the local network.
583
<ulink url="http://www.avahi.org/">Avahi</ulink>
587
Avahi is the library this server calls to implement
588
Zeroconf service announcements.
594
<ulink url="http://www.gnu.org/software/gnutls/"
599
GnuTLS is the library this server uses to implement TLS for
600
communicating securely with the client, and at the same time
601
confidently get the client’s public OpenPGP key.
607
RFC 4291: <citetitle>IP Version 6 Addressing
608
Architecture</citetitle>
613
<term>Section 2.2: <citetitle>Text Representation of
614
Addresses</citetitle></term>
615
<listitem><para/></listitem>
618
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
619
Address</citetitle></term>
620
<listitem><para/></listitem>
623
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
624
Addresses</citetitle></term>
627
The clients use IPv6 link-local addresses, which are
628
immediately usable since a link-local addresses is
629
automatically assigned to a network interfaces when it
639
RFC 4346: <citetitle>The Transport Layer Security (TLS)
640
Protocol Version 1.1</citetitle>
644
TLS 1.1 is the protocol implemented by GnuTLS.
650
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
654
The data sent to clients is binary encrypted OpenPGP data.
660
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
665
This is implemented by GnuTLS and used by this server so
666
that OpenPGP keys can be used.
673
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