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46
<refname><command>&COMMANDNAME;</command></refname>
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Client for <application>Mandos</application>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--connect
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<replaceable>ADDRESS</replaceable><literal>:</literal
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<replaceable>IPADDR</replaceable><literal>:</literal
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><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>IPADDR</replaceable><literal>:</literal
63
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><replaceable>PORT</replaceable></option></arg>
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<arg choice="plain"><option>--keydir
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg choice="plain"><option>-d
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg choice="plain"><option>--interface
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<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>-i
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</refsynopsisdiv>
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<refsect1 id="description">
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<title>DESCRIPTION</title>
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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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to get a password. It uses IPv6 link-local addresses to get
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network connectivity, Zeroconf to find the server, and TLS with
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an OpenPGP key to ensure authenticity and confidentiality. It
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keeps running, trying all servers on the network, until it
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receives a satisfactory reply.
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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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<manvolnum>8mandos</manvolnum></citerefentry>, which in turn
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runs as a <quote>keyscript</quote> specified in the
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<citerefentry><refentrytitle>crypttab</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry> file.
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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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This option is normally only useful for debugging.
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<term><option>--interface=<replaceable
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>NAME</replaceable></option></term>
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<term><option>--keydir=<replaceable
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>DIRECTORY</replaceable></option></term>
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<replaceable>DIRECTORY</replaceable></option></term>
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Directory to read the OpenPGP key files
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<filename>pubkey.txt</filename> and
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<filename>seckey.txt</filename> from. The default is
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<filename>/conf/conf.d/mandos</filename> (in the initial
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<acronym>RAM</acronym> disk environment).
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<term><option>--interface=
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<replaceable>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 the empty
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string, which will automatically choose an appropriate
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If the <option>--connect</option> option is used, this
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specifies the interface to use to connect to the address
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Note that since this program will normally run in the
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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>
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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 string
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<quote><literal>none</literal></quote>; this will not use
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any specific interface, and will not bring up an interface
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on startup. This is not recommended, and only meant for
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Mandos servers to connect to. The default it
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<quote><literal>eth0</literal></quote>.
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<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 client part. It is a plugin started by
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<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
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at all. This is why a separate plugin runner (<citerefentry>
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<refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
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both this program and others in in parallel,
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<emphasis>one</emphasis> of which will prompt for passwords on
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<refsect1 id="exit_status">
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<title>EXIT STATUS</title>
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successfully decrypted and output on standard output. The
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program will exit with a non-zero exit status only if a critical
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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.
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<refsect1 id="environment">
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<title>ENVIRONMENT</title>
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This program does not use any environment variables, not even
384
the ones provided by <citerefentry><refentrytitle
385
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
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<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
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Armor</quote> format. These are the default file names,
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they can be changed with the <option>--pubkey</option> and
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<option>--seckey</option> options.
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<!-- <refsect1 id="bugs"> -->
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<!-- <title>BUGS</title> -->
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<application>Mandosservers</application> servers as they appear,
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trying to get a decryptable password.
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<!-- <refsect1 id="environment"> -->
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<!-- <title>ENVIRONMENT</title> -->
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<!-- This program does not use any environment variables. -->
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<!-- </refsect1> -->
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<refsect1 id="example">
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<title>EXAMPLE</title>
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Note that normally, command line options will not be given
420
directly, but via options for the Mandos <citerefentry
421
><refentrytitle>plugin-runner</refentrytitle>
422
<manvolnum>8mandos</manvolnum></citerefentry>.
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Normal invocation needs no options, if the network interface
427
is <quote>eth0</quote>:
430
<userinput>&COMMANDNAME;</userinput>
435
Search for Mandos servers (and connect to them) using another
439
<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --interface eth1</userinput>
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Run in debug mode, and use a custom key:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
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Run in debug mode, with a custom key, and do not use Zeroconf
457
to locate a server; connect directly to the IPv6 link-local
458
address <quote><systemitem class="ipaddress"
459
>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
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using interface eth2:
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
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<refsect1 id="security">
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<title>SECURITY</title>
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This program is set-uid to root, but will switch back to the
475
original (and presumably non-privileged) user and group after
476
bringing up the network interface.
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To use this program for its intended purpose (see <xref
480
linkend="purpose"/>), the password for the root file system will
481
have to be given out to be stored in a server computer, after
482
having been encrypted using an OpenPGP key. This encrypted data
483
which will be stored in a server can only be decrypted by the
484
OpenPGP key, and the data will only be given out to those
485
clients who can prove they actually have that key. This key,
486
however, is stored unencrypted on the client side in its initial
487
<acronym>RAM</acronym> disk image file system. This is normally
488
readable by all, but this is normally fixed during installation
489
of this program; file permissions are set so that no-one is able
493
The only remaining weak point is that someone with physical
494
access to the client hard drive might turn off the client
495
computer, read the OpenPGP keys directly from the hard drive,
496
and communicate with the server. To safeguard against this, the
497
server is supposed to notice the client disappearing and stop
498
giving out the encrypted data. Therefore, it is important to
499
set the timeout and checker interval values tightly on the
500
server. See <citerefentry><refentrytitle
501
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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It will also help if the checker program on the server is
505
configured to request something from the client which can not be
506
spoofed by someone else on the network, unlike unencrypted
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<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
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<emphasis>Note</emphasis>: This makes it completely insecure to
511
have <application >Mandos</application> clients which dual-boot
512
to another operating system which is <emphasis>not</emphasis>
513
trusted to keep the initial <acronym>RAM</acronym> disk image
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<refsect1 id="see_also">
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<title>SEE ALSO</title>
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<citerefentry><refentrytitle>cryptsetup</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>crypttab</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>,
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383
<citerefentry><refentrytitle>mandos</refentrytitle>
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384
<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>password-prompt</refentrytitle>
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387
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>
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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
539
Zeroconf is the network protocol standard used for finding
540
Mandos servers on the local network.
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<ulink url="http://www.avahi.org/">Avahi</ulink>
550
Avahi is the library this program calls to find Zeroconf
557
<ulink url="http://www.gnu.org/software/gnutls/"
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GnuTLS is the library this client uses to implement TLS for
563
communicating securely with the server, and at the same time
564
send the public OpenPGP key to the server.
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<ulink url="http://www.gnupg.org/related_software/gpgme/"
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GPGME is the library used to decrypt the OpenPGP data sent
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RFC 4291: <citetitle>IP Version 6 Addressing
583
Architecture</citetitle>
588
<term>Section 2.2: <citetitle>Text Representation of
589
Addresses</citetitle></term>
590
<listitem><para/></listitem>
593
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
594
Address</citetitle></term>
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<listitem><para/></listitem>
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<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
599
Addresses</citetitle></term>
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This client uses IPv6 link-local addresses, which are
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immediately usable since a link-local addresses is
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automatically assigned to a network interfaces when it
614
RFC 4346: <citetitle>The Transport Layer Security (TLS)
615
Protocol Version 1.1</citetitle>
619
TLS 1.1 is the protocol implemented by GnuTLS.
625
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
629
The data received from the server is binary encrypted
636
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
641
This is implemented by GnuTLS and used by this program so
642
that OpenPGP keys can be used.
392
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
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<ulink url="http://www.avahi.org/">Avahi</ulink>
401
url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>
406
url="http://www.gnupg.org/related_software/gpgme/">
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<citation>RFC 4880: <citetitle>OpenPGP Message
412
Format</citetitle></citation>
416
<citation>RFC 5081: <citetitle>Using OpenPGP Keys for
417
Transport Layer Security</citetitle></citation>
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<citation>RFC 4291: <citetitle>IP Version 6 Addressing
422
Architecture</citetitle>, section 2.5.6, Link-Local IPv6
423
Unicast Addresses</citation>
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