67
48
<refname><command>&COMMANDNAME;</command></refname>
50
Client for <application>Mandos</application>
75
56
<command>&COMMANDNAME;</command>
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<arg choice='opt' rep='repeat'>OPTION</arg>
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<arg choice="plain"><option>--connect
59
<replaceable>ADDRESS</replaceable><literal>:</literal
60
><replaceable>PORT</replaceable></option></arg>
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<arg choice="plain"><option>-c
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<replaceable>ADDRESS</replaceable><literal>:</literal
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><replaceable>PORT</replaceable></option></arg>
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<arg choice="plain"><option>--interface
68
<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>-i
70
<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>--pubkey
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<replaceable>FILE</replaceable></option></arg>
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<arg choice="plain"><option>-p
77
<replaceable>FILE</replaceable></option></arg>
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<arg choice="plain"><option>--seckey
82
<replaceable>FILE</replaceable></option></arg>
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<arg choice="plain"><option>-s
84
<replaceable>FILE</replaceable></option></arg>
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<option>--priority <replaceable>STRING</replaceable></option>
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<option>--dh-bits <replaceable>BITS</replaceable></option>
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<option>--delay <replaceable>SECONDS</replaceable></option>
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<option>--debug</option>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--help</option></arg>
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<arg choice="plain"><option>-?</option></arg>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--usage</option></arg>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--version</option></arg>
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<arg choice="plain"><option>-V</option></arg>
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<refsect1 id="description">
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124
<title>DESCRIPTION</title>
83
<command>&COMMANDNAME;</command> is a mandos plugin that works
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like a client program that through avahi detects mandos servers,
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sets up a gnutls connect and request a encrypted password. Any
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passwords given is automaticly decrypted and passed to
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<term><literal>-c</literal>, <literal>--connect=<replaceable>
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IP</replaceable></literal></term>
96
Connect directly to a sepcified mandos server
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<term><literal>-d</literal>, <literal>--keydir=<replaceable>
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KEYDIR</replaceable></literal></term>
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Directory where the openpgp keyring is
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<term><literal>-i</literal>, <literal>--interface=
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<replaceable>INTERFACE</replaceable></literal></term>
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Interface that Avahi will conntect through
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<term><literal>-p</literal>, <literal>--pubkey=<replaceable>
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PUBKEY</replaceable></literal></term>
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Public openpgp key for gnutls authentication
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<term><literal>-s</literal>, <literal>--seckey=<replaceable>
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SECKEY</replaceable></literal></term>
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Secret openpgp key for gnutls authentication
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<term><literal>--priority=<replaceable>PRIORITY</replaceable>
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<term><literal>--dh-bits=<replaceable>BITS</replaceable>
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dh-bits to use in gnutls communication
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<term><literal>--debug</literal></term>
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<term><literal>-?</literal>, <literal>--help</literal></term>
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<term><literal>--usage</literal></term>
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Gives a short usage message
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<term><literal>-V</literal>, <literal>--version</literal></term>
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Prints the program version
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<command>&COMMANDNAME;</command> is a client program that
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communicates with <citerefentry><refentrytitle
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>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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to get a password. In slightly more detail, this client program
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brings up a network interface, uses the interface’s IPv6
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link-local address to get network connectivity, uses Zeroconf to
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find servers on the local network, and communicates with servers
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using TLS with an OpenPGP key to ensure authenticity and
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confidentiality. This client program keeps running, trying all
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servers on the network, until it receives a satisfactory reply
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or a TERM signal is received. If no servers are found, or after
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all servers have been tried, it waits indefinitely for new
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This program is not meant to be run directly; it is really meant
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to run as a plugin of the <application>Mandos</application>
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
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initial <acronym>RAM</acronym> disk environment because it is
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specified as a <quote>keyscript</quote> in the <citerefentry>
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<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry> file.
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<refsect1 id="purpose">
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<title>PURPOSE</title>
155
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
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linkend="overview"/> for details.
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<refsect1 id="options">
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<title>OPTIONS</title>
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This program is commonly not invoked from the command line; it
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is normally started by the <application>Mandos</application>
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plugin runner, see <citerefentry><refentrytitle
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>plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
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</citerefentry>. Any command line options this program accepts
170
are therefore normally provided by the plugin runner, and not
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<term><option>--connect=<replaceable
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>ADDRESS</replaceable><literal>:</literal><replaceable
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>PORT</replaceable></option></term>
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<replaceable>ADDRESS</replaceable><literal>:</literal
181
><replaceable>PORT</replaceable></option></term>
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Do not use Zeroconf to locate servers. Connect directly
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to only one specified <application>Mandos</application>
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server. Note that an IPv6 address has colon characters in
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it, so the <emphasis>last</emphasis> colon character is
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assumed to separate the address from the port number.
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This option is normally only useful for testing and
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<term><option>--interface=<replaceable
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>NAME</replaceable></option></term>
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<replaceable>NAME</replaceable></option></term>
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Network interface that will be brought up and scanned for
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Mandos servers to connect to. The default is
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<quote><literal>eth0</literal></quote>.
209
If the <option>--connect</option> option is used, this
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specifies the interface to use to connect to the address
214
Note that since this program will normally run in the
215
initial RAM disk environment, the interface must be an
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interface which exists at that stage. Thus, the interface
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can not be a pseudo-interface such as <quote>br0</quote>
218
or <quote>tun0</quote>; such interfaces will not exist
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until much later in the boot process, and can not be used
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<replaceable>NAME</replaceable> can be the empty string;
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this will not use any specific interface, and will not
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bring up an interface on startup. This is not
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recommended, and only meant for advanced users.
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<term><option>--pubkey=<replaceable
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>FILE</replaceable></option></term>
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<replaceable>FILE</replaceable></option></term>
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OpenPGP public key file name. The default name is
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<quote><filename>/conf/conf.d/mandos/pubkey.txt</filename
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<term><option>--seckey=<replaceable
247
>FILE</replaceable></option></term>
249
<replaceable>FILE</replaceable></option></term>
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OpenPGP secret key file name. The default name is
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<quote><filename>/conf/conf.d/mandos/seckey.txt</filename
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<term><option>--priority=<replaceable
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>STRING</replaceable></option></term>
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<xi:include href="../mandos-options.xml"
264
xpointer="priority"/>
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<term><option>--dh-bits=<replaceable
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>BITS</replaceable></option></term>
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Sets the number of bits to use for the prime number in the
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TLS Diffie-Hellman key exchange. Default is 1024.
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<term><option>--delay=<replaceable
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>SECONDS</replaceable></option></term>
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After bringing the network interface up, the program waits
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for the interface to arrive in a <quote>running</quote>
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state before proceeding. During this time, the kernel log
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level will be lowered to reduce clutter on the system
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console, alleviating any other plugins which might be
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using the system console. This option sets the upper
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limit of seconds to wait. The default is 2.5 seconds.
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<term><option>--debug</option></term>
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Enable debug mode. This will enable a lot of output to
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standard error about what the program is doing. The
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program will still perform all other functions normally.
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It will also enable debug mode in the Avahi and GnuTLS
305
libraries, making them print large amounts of debugging
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<term><option>--help</option></term>
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<term><option>-?</option></term>
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Gives a help message about options and their meanings.
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<term><option>--usage</option></term>
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Gives a short usage message.
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<term><option>--version</option></term>
332
<term><option>-V</option></term>
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Prints the program version.
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<refsect1 id="overview">
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<title>OVERVIEW</title>
344
<xi:include href="../overview.xml"/>
346
This program is the client part. It is a plugin started by
347
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry> which will run in
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an initial <acronym>RAM</acronym> disk environment.
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This program could, theoretically, be used as a keyscript in
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<filename>/etc/crypttab</filename>, but it would then be
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impossible to enter a password for the encrypted root disk at
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the console, since this program does not read from the console
356
at all. This is why a separate plugin runner (<citerefentry>
357
<refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
359
both this program and others in in parallel,
360
<emphasis>one</emphasis> of which will prompt for passwords on
365
<refsect1 id="exit_status">
366
<title>EXIT STATUS</title>
368
This program will exit with a successful (zero) exit status if a
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server could be found and the password received from it could be
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successfully decrypted and output on standard output. The
371
program will exit with a non-zero exit status only if a critical
372
error occurs. Otherwise, it will forever connect to new
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<application>Mandos</application> servers as they appear, trying
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to get a decryptable password and print it.
378
<refsect1 id="environment">
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<title>ENVIRONMENT</title>
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This program does not use any environment variables, not even
382
the ones provided by <citerefentry><refentrytitle
383
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
388
<refsect1 id="files">
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<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
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<term><filename>/conf/conf.d/mandos/seckey.txt</filename
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OpenPGP public and private key files, in <quote>ASCII
399
Armor</quote> format. These are the default file names,
400
they can be changed with the <option>--pubkey</option> and
401
<option>--seckey</option> options.
408
<!-- <refsect1 id="bugs"> -->
409
<!-- <title>BUGS</title> -->
414
<refsect1 id="example">
415
<title>EXAMPLE</title>
417
Note that normally, command line options will not be given
418
directly, but via options for the Mandos <citerefentry
419
><refentrytitle>plugin-runner</refentrytitle>
420
<manvolnum>8mandos</manvolnum></citerefentry>.
424
Normal invocation needs no options, if the network interface
425
is <quote>eth0</quote>:
428
<userinput>&COMMANDNAME;</userinput>
433
Search for Mandos servers (and connect to them) using another
437
<!-- do not wrap this line -->
438
<userinput>&COMMANDNAME; --interface eth1</userinput>
443
Run in debug mode, and use a custom key:
447
<!-- do not wrap this line -->
448
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
454
Run in debug mode, with a custom key, and do not use Zeroconf
455
to locate a server; connect directly to the IPv6 link-local
456
address <quote><systemitem class="ipaddress"
457
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
458
using interface eth2:
462
<!-- do not wrap this line -->
463
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
469
<refsect1 id="security">
470
<title>SECURITY</title>
472
This program is set-uid to root, but will switch back to the
473
original (and presumably non-privileged) user and group after
474
bringing up the network interface.
477
To use this program for its intended purpose (see <xref
478
linkend="purpose"/>), the password for the root file system will
479
have to be given out to be stored in a server computer, after
480
having been encrypted using an OpenPGP key. This encrypted data
481
which will be stored in a server can only be decrypted by the
482
OpenPGP key, and the data will only be given out to those
483
clients who can prove they actually have that key. This key,
484
however, is stored unencrypted on the client side in its initial
485
<acronym>RAM</acronym> disk image file system. This is normally
486
readable by all, but this is normally fixed during installation
487
of this program; file permissions are set so that no-one is able
491
The only remaining weak point is that someone with physical
492
access to the client hard drive might turn off the client
493
computer, read the OpenPGP keys directly from the hard drive,
494
and communicate with the server. To safeguard against this, the
495
server is supposed to notice the client disappearing and stop
496
giving out the encrypted data. Therefore, it is important to
497
set the timeout and checker interval values tightly on the
498
server. See <citerefentry><refentrytitle
499
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
502
It will also help if the checker program on the server is
503
configured to request something from the client which can not be
504
spoofed by someone else on the network, unlike unencrypted
505
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
508
<emphasis>Note</emphasis>: This makes it completely insecure to
509
have <application >Mandos</application> clients which dual-boot
510
to another operating system which is <emphasis>not</emphasis>
511
trusted to keep the initial <acronym>RAM</acronym> disk image
516
<refsect1 id="see_also">
517
<title>SEE ALSO</title>
519
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
520
<manvolnum>8</manvolnum></citerefentry>,
521
<citerefentry><refentrytitle>crypttab</refentrytitle>
522
<manvolnum>5</manvolnum></citerefentry>,
523
<citerefentry><refentrytitle>mandos</refentrytitle>
524
<manvolnum>8</manvolnum></citerefentry>,
525
<citerefentry><refentrytitle>password-prompt</refentrytitle>
526
<manvolnum>8mandos</manvolnum></citerefentry>,
527
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
528
<manvolnum>8mandos</manvolnum></citerefentry>
533
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
537
Zeroconf is the network protocol standard used for finding
538
Mandos servers on the local network.
544
<ulink url="http://www.avahi.org/">Avahi</ulink>
548
Avahi is the library this program calls to find Zeroconf
555
<ulink url="http://www.gnu.org/software/gnutls/"
560
GnuTLS is the library this client uses to implement TLS for
561
communicating securely with the server, and at the same time
562
send the public OpenPGP key to the server.
568
<ulink url="http://www.gnupg.org/related_software/gpgme/"
573
GPGME is the library used to decrypt the OpenPGP data sent
580
RFC 4291: <citetitle>IP Version 6 Addressing
581
Architecture</citetitle>
586
<term>Section 2.2: <citetitle>Text Representation of
587
Addresses</citetitle></term>
588
<listitem><para/></listitem>
591
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
592
Address</citetitle></term>
593
<listitem><para/></listitem>
596
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
597
Addresses</citetitle></term>
600
This client uses IPv6 link-local addresses, which are
601
immediately usable since a link-local addresses is
602
automatically assigned to a network interfaces when it
612
RFC 4346: <citetitle>The Transport Layer Security (TLS)
613
Protocol Version 1.1</citetitle>
617
TLS 1.1 is the protocol implemented by GnuTLS.
623
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
627
The data received from the server is binary encrypted
634
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
639
This is implemented by GnuTLS and used by this program so
640
that OpenPGP keys can be used.
648
<!-- Local Variables: -->
649
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650
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