66
67
<refname><command>&COMMANDNAME;</command></refname>
68
Sends encrypted passwords to authenticated Mandos clients
69
Sends encrypted passwords to authenticated mandos clients
74
75
<command>&COMMANDNAME;</command>
75
<arg>--interface<arg choice="plain">IF</arg></arg>
76
<arg>--address<arg choice="plain">ADDRESS</arg></arg>
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<arg>--port<arg choice="plain">PORT</arg></arg>
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<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
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<arg>--servicename<arg choice="plain">NAME</arg></arg>
80
<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
84
<command>&COMMANDNAME;</command>
85
<arg>-i<arg choice="plain">IF</arg></arg>
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<arg>-a<arg choice="plain">ADDRESS</arg></arg>
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<arg>-p<arg choice="plain">PORT</arg></arg>
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<arg>--priority<arg choice="plain">PRIORITY</arg></arg>
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<arg>--servicename<arg choice="plain">NAME</arg></arg>
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<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>
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<command>&COMMANDNAME;</command>
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<arg choice="plain">-h</arg>
97
<arg choice="plain">--help</arg>
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<command>&COMMANDNAME;</command>
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<arg choice="plain">--version</arg>
105
<command>&COMMANDNAME;</command>
106
<arg choice="plain">--check</arg>
76
<arg choice='opt' rep='repeat'>OPTION</arg>
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80
<refsect1 id="description">
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81
<title>DESCRIPTION</title>
113
<command>&COMMANDNAME;</command> is a server daemon which
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handles incoming request for passwords for a pre-defined list of
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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
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link-local addresses, since the clients will probably not have
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any other addresses configured (see <xref linkend="overview"/>).
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Any authenticated client is then given the stored pre-encrypted
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password for that specific client.
127
<refsect1 id="purpose">
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<title>PURPOSE</title>
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The purpose of this is to enable <emphasis>remote and unattended
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rebooting</emphasis> of client host computer with an
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<emphasis>encrypted root file system</emphasis>. See <xref
134
linkend="overview"/> for details.
139
<refsect1 id="options">
140
<title>OPTIONS</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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92
<term><literal>-h</literal>, <literal>--help</literal></term>
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Show a help message and exit
95
show a help message and exit
194
149
<term><literal>--priority <replaceable>
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PRIORITY</replaceable></literal></term>
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<xi:include href="mandos-options.xml" xpointer="priority"/>
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GnuTLS priority string. See <citerefentry>
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<refentrytitle>gnutls_priority_init</refentrytitle>
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<manvolnum>3</manvolnum></citerefentry>
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161
<term><literal>--servicename <replaceable>NAME</replaceable>
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162
</literal></term>
205
<xi:include href="mandos-options.xml"
206
xpointer="servicename"/>
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Zeroconf service name
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<term><literal>--configdir <replaceable>DIR</replaceable>
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</literal></term>
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Directory to search for configuration files. Default is
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<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>.
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<term><literal>--version</literal></term>
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Prints the program version and exit.
236
<refsect1 id="overview">
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<title>OVERVIEW</title>
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<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>
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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>
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<entry>Mandos Client</entry>
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<entry>Direction</entry>
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<entry>Mandos Server</entry>
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<entry>Connect</entry>
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<entry>-><!-- → --></entry>
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<entry><quote><literal>1\r\en</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>
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<entry>OpenPGP public key (part of TLS handshake)</entry>
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<entry>-><!-- → --></entry>
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<entry><-<!-- ← --></entry>
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<entry>Binary blob (client will assume OpenPGP data)</entry>
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<entry><-<!-- ← --></entry>
301
</tbody></tgroup></table>
304
<refsect1 id="checking">
305
<title>CHECKING</title>
307
The server will, by default, continually check that the clients
308
are still up. If a client has not been confirmed as being up
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for some time, the client is assumed to be compromised and is no
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longer eligible to receive the encrypted password. The timeout,
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checker program, and interval between checks can be configured
312
both globally and per client; see <citerefentry>
313
<refentrytitle>mandos.conf</refentrytitle>
314
<manvolnum>5</manvolnum></citerefentry> and <citerefentry>
315
<refentrytitle>mandos-clients.conf</refentrytitle>
316
<manvolnum>5</manvolnum></citerefentry>.
320
<refsect1 id="logging">
321
<title>LOGGING</title>
323
The server will send log messaged with various severity levels
324
to <filename>/dev/log</filename>. With the
325
<option>--debug</option> option, it will log even more messages,
326
and also show them on the console.
330
<refsect1 id="exit_status">
331
<title>EXIT STATUS</title>
333
The server will exit with a non-zero exit status only when a
334
critical error is encountered.
338
<refsect1 id="environment">
339
<title>ENVIRONMENT</title>
342
<term><varname>PATH</varname></term>
345
To start the configured checker (see <xref
346
linkend="checking"/>), the server uses
347
<filename>/bin/sh</filename>, which in turn uses
348
<varname>PATH</varname> to search for matching commands if
349
an absolute path is not given. See <citerefentry>
350
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
361
Use the <option>--configdir</option> option to change where
362
<command>&COMMANDNAME;</command> looks for its configurations
363
files. The default file names are listed here.
367
<term><filename>/etc/mandos/mandos.conf</filename></term>
370
Server-global settings. See
371
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
372
<manvolnum>5</manvolnum></citerefentry> for details.
377
<term><filename>/etc/mandos/clients.conf</filename></term>
380
List of clients and client-specific settings. See
381
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
382
<manvolnum>5</manvolnum></citerefentry> for details.
387
<term><filename>/var/run/mandos/mandos.pid</filename></term>
390
The file containing the process id of
391
<command>&COMMANDNAME;</command>.
396
<term><filename>/dev/log</filename></term>
399
The Unix domain socket to where local syslog messages are
405
<term><filename>/bin/sh</filename></term>
408
This is used to start the configured checker command for
409
each client. See <citerefentry>
410
<refentrytitle>mandos-clients.conf</refentrytitle>
411
<manvolnum>5</manvolnum></citerefentry> for details.
421
This server might, on especially fatal errors, emit a Python
422
backtrace. This could be considered a feature.
425
Currently, if a client is declared <quote>invalid</quote> due to
426
having timed out, the server does not record this fact onto
427
permanent storage. This has some security implications, see
428
<xref linkend="CLIENTS"/>.
431
There is currently no way of querying the server of the current
432
status of clients, other than analyzing its <systemitem
433
class="service">syslog</systemitem> output.
436
There is no fine-grained control over logging and debug output.
439
Debug mode is conflated with running in the foreground.
442
The console log messages does not show a timestamp.
446
<refsect1 id="example">
447
<title>EXAMPLE</title>
450
Normal invocation needs no options:
453
<userinput>mandos</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>mandos --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>mandos --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 does not need any special
492
privileges to run, and is designed to run as 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 running the server.
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 RAM image of the client host. What should be done in
526
that case (if restarting the server program really is
527
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>password-request</refentrytitle>
534
<manvolnum>8mandos</manvolnum></citerefentry>.
539
<refsect1 id="see_also">
540
<title>SEE ALSO</title>
545
<refentrytitle>password-request</refentrytitle>
546
<manvolnum>8mandos</manvolnum>
551
This is the actual program which talks to this server.
552
Note that it is normally not invoked directly, and is only
553
run in the initial RAM disk environment, and not on a
554
fully started system.
560
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
564
Zeroconf is the network protocol standard used by clients
565
for finding this Mandos server on the local network.
571
<ulink url="http://www.avahi.org/">Avahi</ulink>
575
Avahi is the library this server calls to implement
576
Zeroconf service announcements.
583
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
587
GnuTLS is the library this server uses to implement TLS for
588
communicating securely with the client, and at the same time
589
confidently get the client’s public OpenPGP key.
595
<citation>RFC 4291: <citetitle>IP Version 6 Addressing
596
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
597
Unicast Addresses</citation>
601
The clients use IPv6 link-local addresses, which are
602
immediately usable since a link-local addresses is
603
automatically assigned to a network interfaces when it is
610
<citation>RFC 4346: <citetitle>The Transport Layer Security
611
(TLS) Protocol Version 1.1</citetitle></citation>
615
TLS 1.1 is the protocol implemented by GnuTLS.
621
<citation>RFC 4880: <citetitle>OpenPGP Message
622
Format</citetitle></citation>
626
The data sent to clients is binary encrypted OpenPGP data.
632
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
633
Transport Layer Security</citetitle></citation>
637
This is implemented by GnuTLS and used by this server so
638
that OpenPGP keys can be used.
175
Directory to search for configuration files