/mandos/release : revision 109

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Committer: Teddy Hogeborn
Date: 2008-08-27 01:18:25 UTC
Revision ID: teddy@fukt.bsnet.se-20080827011825-ka3ni6xvy2ehi1y8

* .bzrignore: New.

* clients.conf ([foo]): Remove Radix-64 checksum.

* mandos (AvahiService.rename, server_state_changed,
          entry_group_state_changed): Make Avahi log messages more
                                      clear that they are about
                                      Zeroconf.
  (fingerprint): Use plain "0" instead of "ctypes.c_uint(0)".

files added:
.bzrignore

COPYING

initramfs-tools-hook

initramfs-tools-hook-conf

initramfs-tools-script

mandos-keygen

mandos-keygen.xml

mandos-options.xml

overview.xml

plugins.d/usplash

files removed:
network-protocol.txt

files renamed:
clients.conf.xml => mandos-clients.conf.xml

mandos-client.c => plugin-runner.c

mandos-client.xml => plugin-runner.xml

files modified:
Makefile

TODO

clients.conf

mandos

mandos.conf

mandos.conf.xml

mandos.xml

plugins.d/password-prompt.c

plugins.d/password-prompt.xml

plugins.d/password-request.c

plugins.d/password-request.xml

Show diffs side-by-side

added added

removed removed

mandos.xml

<?xml version='1.0' encoding='UTF-8'?>

<?xml-stylesheet type="text/xsl"

href="http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl"?>

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"

"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [

<!ENTITY VERSION "1.0">

<!ENTITY COMMANDNAME "mandos">

<title>&COMMANDNAME;</title>

<productname>&COMMANDNAME;</productname>

<productnumber>&VERSION;</productnumber>

</authorgroup>

<holder>Teddy Hogeborn & Björn Påhlsson</holder>

<holder>Teddy Hogeborn</holder>

<holder>Björn Påhlsson</holder>

</copyright>

<para>

<refname><command>&COMMANDNAME;</command></refname>

Sends encrypted passwords to authenticated mandos clients

Sends encrypted passwords to authenticated Mandos clients

</refpurpose>

</refnamediv>

<command>&COMMANDNAME;</command>

<arg choice='opt' rep='repeat'>OPTION</arg>

<arg>--interface<arg choice="plain">NAME</arg></arg>

<arg>--address<arg choice="plain">ADDRESS</arg></arg>

<arg>--priority<arg choice="plain">PRIORITY</arg></arg>

<arg>--servicename<arg choice="plain">NAME</arg></arg>

<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>

<arg>--debug</arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

<arg>-a<arg choice="plain">ADDRESS</arg></arg>

<arg>--priority<arg choice="plain">PRIORITY</arg></arg>

<arg>--servicename<arg choice="plain">NAME</arg></arg>

<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>

<arg>--debug</arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

</group>

</cmdsynopsis>

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<command>&COMMANDNAME;</command>

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<arg choice="plain">--version</arg>

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</cmdsynopsis>

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<command>&COMMANDNAME;</command>

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<arg choice="plain">--check</arg>

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</cmdsynopsis>

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</refsynopsisdiv>

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<title>DESCRIPTION</title>

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<para>

<command>&COMMANDNAME;</command> is a server daemon that handels

incomming passwords request for passwords. Mandos use avahi to

announce the service, and through gnutls authenticates

clients. Any authenticated client is then given its encrypted

password.

</para>

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<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.

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</para>

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</refsect1>

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<title>PURPOSE</title>

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<para>

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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

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linkend="overview"/> for details.

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</para>

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</refsect1>

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<title>OPTIONS</title>

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<para>

show a help message and exit

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Show a help message and exit

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</para>

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</listitem>

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</varlistentry>

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<term><literal>-i</literal>, <literal>--interface <replaceable>

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IF</replaceable></literal></term>

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<term><literal>-i</literal>, <literal>--interface <replaceable

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>NAME</replaceable></literal></term>

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<para>

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Bind to interface IF

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</para>

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<xi:include href="mandos-options.xml" xpointer="interface"/>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>-a</literal>, <literal>--address <replaceable>

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ADDRESS</replaceable></literal></term>

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<para>

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Address to listen for requests on

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</para>

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<xi:include href="mandos-options.xml" xpointer="address"/>

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</listitem>

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</varlistentry>

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</varlistentry>

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PORT</replaceable></literal></term>

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<para>

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Port number to receive requests on

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</para>

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<xi:include href="mandos-options.xml" xpointer="port"/>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--check</literal></term>

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<para>

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Run self-test on the server

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Run the server’s self-tests. This includes any unit

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tests, etc.

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--debug</literal></term>

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<para>

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Debug mode

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</para>

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<xi:include href="mandos-options.xml" xpointer="debug"/>

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</listitem>

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</varlistentry>

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<term><literal>--priority <replaceable>

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PRIORITY</replaceable></literal></term>

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<para>

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GnuTLS priority string. See <citerefentry>

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<refentrytitle>gnutls_priority_init</refentrytitle>

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</para>

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<xi:include href="mandos-options.xml" xpointer="priority"/>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--servicename <replaceable>NAME</replaceable>

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</literal></term>

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<para>

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Zeroconf service name

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</para>

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<xi:include href="mandos-options.xml"

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xpointer="servicename"/>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--configdir <replaceable>DIR</replaceable>

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</literal></term>

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<para>

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Directory to search for configuration files

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</para>

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</listitem>

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</varlistentry>

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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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<refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry>.

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</para>

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</listitem>

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</varlistentry>

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<term><literal>--version</literal></term>

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<para>

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Prints the program version and exit.

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</refsect1>

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<title>OVERVIEW</title>

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<xi:include href="overview.xml"/>

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<para>

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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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</para>

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</refsect1>

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<title>NETWORK PROTOCOL</title>

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<para>

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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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</para>

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<table>

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<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>

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<row>

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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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</row>

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</thead><tbody>

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<row>

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<entry>Connect</entry>

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</row>

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<row>

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</row>

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<row>

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<entry>TLS handshake <emphasis>as TLS <quote>server</quote>

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</emphasis></entry>

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<entry>TLS handshake <emphasis>as TLS <quote>client</quote>

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</emphasis></entry>

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</row>

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<row>

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<entry>OpenPGP public key (part of TLS handshake)</entry>

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</row>

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<row>

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<entry>Binary blob (client will assume OpenPGP data)</entry>

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</row>

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<row>

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<entry>Close</entry>

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</row>

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</tbody></tgroup></table>

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</refsect1>

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<title>CHECKING</title>

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<para>

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The server will, by default, continually check that the clients

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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

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both globally and per client; see <citerefentry>

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<refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry>.

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</para>

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</refsect1>

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<title>LOGGING</title>

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<para>

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The server will send log message with various severity levels to

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<filename>/dev/log</filename>. With the

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<option>--debug</option> option, it will log even more messages,

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and also show them on the console.

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</para>

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</refsect1>

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<title>EXIT STATUS</title>

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<para>

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The server will exit with a non-zero exit status only when a

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critical error is encountered.

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</para>

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</refsect1>

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<title>ENVIRONMENT</title>

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<para>

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To start the configured checker (see <xref

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linkend="checking"/>), the server uses

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<filename>/bin/sh</filename>, which in turn uses

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<varname>PATH</varname> to search for matching commands if

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an absolute path is not given. See <citerefentry>

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</citerefentry>.

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</refsect1>

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<title>FILES</title>

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<para>

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Use the <option>--configdir</option> option to change where

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<command>&COMMANDNAME;</command> looks for its configurations

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files. The default file names are listed here.

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</para>

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<term><filename>/etc/mandos/mandos.conf</filename></term>

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<para>

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Server-global settings. See

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<citerefentry><refentrytitle>mandos.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry> for details.

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</para>

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</listitem>

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</varlistentry>

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<term><filename>/etc/mandos/clients.conf</filename></term>

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<para>

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List of clients and client-specific settings. See

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<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry> for details.

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</para>

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</listitem>

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</varlistentry>

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<term><filename>/var/run/mandos/mandos.pid</filename></term>

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<para>

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The file containing the process id of

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<command>&COMMANDNAME;</command>.

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</para>

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</listitem>

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</varlistentry>

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<para>

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The Unix domain socket to where local syslog messages are

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sent.

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</para>

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</listitem>

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</varlistentry>

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<para>

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This is used to start the configured checker command for

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each client. See <citerefentry>

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<refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry> for details.

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</refsect1>

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<para>

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This server might, on especially fatal errors, emit a Python

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backtrace. This could be considered a feature.

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</para>

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<para>

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Currently, if a client is declared <quote>invalid</quote> due to

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having timed out, the server does not record this fact onto

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permanent storage. This has some security implications, see

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<xref linkend="CLIENTS"/>.

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</para>

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<para>

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There is currently no way of querying the server of the current

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status of clients, other than analyzing its <systemitem

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class="service">syslog</systemitem> output.

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</para>

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<para>

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There is no fine-grained control over logging and debug output.

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</para>

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<para>

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Debug mode is conflated with running in the foreground.

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</para>

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<para>

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The console log messages does not show a timestamp.

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</para>

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</refsect1>

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<title>EXAMPLE</title>

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<para>

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Normal invocation needs no options:

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</para>

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<para>

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<userinput>mandos</userinput>

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</para>

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</informalexample>

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<para>

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Run the server in debug mode, read configuration files from

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the <filename>~/mandos</filename> directory, and use the

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Zeroconf service name <quote>Test</quote> to not collide with

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any other official Mandos server on this host:

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</para>

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<para>

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<userinput>mandos --debug --configdir ~/mandos --servicename Test</userinput>

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</para>

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</informalexample>

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<para>

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Run the server normally, but only listen to one interface and

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only on the link-local address on that interface:

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</para>

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<para>

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<userinput>mandos --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>

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</para>

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</informalexample>

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</refsect1>

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<title>SECURITY</title>

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<title>SERVER</title>

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<para>

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Running this <command>&COMMANDNAME;</command> server program

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should not in itself present any security risk to the host

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computer running it. The program does not need any special

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privileges to run, and is designed to run as a non-root user.

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</para>

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</refsect2>

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<title>CLIENTS</title>

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<para>

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The server only gives out its stored data to clients which

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does have the OpenPGP key of the stored fingerprint. This is

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guaranteed by the fact that the client sends its OpenPGP

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public key in the TLS handshake; this ensures it to be

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genuine. The server computes the fingerprint of the key

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itself and looks up the fingerprint in its list of

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clients. The <filename>clients.conf</filename> file (see

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<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry>)

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<emphasis>must</emphasis> be made non-readable by anyone

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except the user running the server.

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</para>

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<para>

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As detailed in <xref linkend="checking"/>, the status of all

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client computers will continually be checked and be assumed

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compromised if they are gone for too long.

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</para>

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<para>

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If a client is compromised, its downtime should be duly noted

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by the server which would therefore declare the client

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invalid. But if the server was ever restarted, it would

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re-read its client list from its configuration file and again

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regard all clients therein as valid, and hence eligible to

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receive their passwords. Therefore, be careful when

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restarting servers if it is suspected that a client has, in

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fact, been compromised by parties who may now be running a

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fake Mandos client with the keys from the non-encrypted

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initial RAM image of the client host. What should be done in

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that case (if restarting the server program really is

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necessary) is to stop the server program, edit the

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configuration file to omit any suspect clients, and restart

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the server program.

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</para>

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<para>

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For more details on client-side security, see

531

<citerefentry><refentrytitle>password-request</refentrytitle>

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<manvolnum>8mandos</manvolnum></citerefentry>.

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</para>

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</refsect2>

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</refsect1>

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<para>

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<refentrytitle>mandos.conf</refentrytitle>

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<refentrytitle>mandos-clients.conf</refentrytitle>

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<refentrytitle>password-request</refentrytitle>

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<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>

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</citerefentry>

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</para>

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<term>

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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>

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</term>

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<para>

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Zeroconf is the network protocol standard used by clients

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for finding this Mandos server on the local network.

559

</para>

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</listitem>

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</varlistentry>

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<term>

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<ulink url="http://www.avahi.org/">Avahi</ulink>

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</term>

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<para>

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Avahi is the library this server calls to implement

569

Zeroconf service announcements.

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</para>

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</listitem>

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</varlistentry>

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<term>

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<ulink url="http://www.gnu.org/software/gnutls/"

576

>GnuTLS</ulink>

577

</term>

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579

<para>

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GnuTLS is the library this server uses to implement TLS for

581

communicating securely with the client, and at the same time

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confidently get the client’s public OpenPGP key.

583

</para>

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</listitem>

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</varlistentry>

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<term>

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RFC 4291: <citetitle>IP Version 6 Addressing

589

Architecture</citetitle>

590

</term>

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<term>Section 2.2: <citetitle>Text Representation of

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Addresses</citetitle></term>

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</varlistentry>

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<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6

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Address</citetitle></term>

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</varlistentry>

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604

<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast

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Addresses</citetitle></term>

606

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<para>

608

The clients use IPv6 link-local addresses, which are

609

immediately usable since a link-local addresses is

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automatically assigned to a network interfaces when it

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is brought up.

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</listitem>

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</varlistentry>

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<term>

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RFC 4346: <citetitle>The Transport Layer Security (TLS)

621

Protocol Version 1.1</citetitle>

622

</term>

623

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<para>

625

TLS 1.1 is the protocol implemented by GnuTLS.

626

</para>

627

</listitem>

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</varlistentry>

629

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<term>

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RFC 4880: <citetitle>OpenPGP Message Format</citetitle>

632

</term>

633

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<para>

635

The data sent to clients is binary encrypted OpenPGP data.

636

</para>

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</listitem>

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</varlistentry>

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<term>

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RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer

642

Security</citetitle>

643

</term>

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<para>

646

This is implemented by GnuTLS and used by this server so

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that OpenPGP keys can be used.

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</refsect1>

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</refentry>

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