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<holder>Teddy Hogeborn & Björn Påhlsson</holder>
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<holder>Teddy Hogeborn</holder>
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<holder>Björn Påhlsson</holder>
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This manual page is free software: you can redistribute it
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and/or modify it under the terms of the GNU General Public
40
License as published by the Free Software Foundation,
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either version 3 of the License, or (at your option) any
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This manual page is distributed in the hope that it will
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be useful, but WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A
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PARTICULAR PURPOSE. See the GNU General Public License
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You should have received a copy of the GNU General Public
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License along with this program; If not, see
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<ulink url="http://www.gnu.org/licenses/"/>.
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<xi:include href="legalnotice.xml"/>
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<refentrytitle>&COMMANDNAME;</refentrytitle>
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<manvolnum>8mandos</manvolnum>
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<manvolnum>8</manvolnum>
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<refname><command>&COMMANDNAME;</command></refname>
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Sends encrypted passwords to authenticated mandos clients
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Gives encrypted passwords to authenticated Mandos clients
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<command>&COMMANDNAME;</command>
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<arg choice='opt' rep='repeat'>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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<replaceable>NAME</replaceable></option></arg>
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<arg choice="plain"><option>--address
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<replaceable>ADDRESS</replaceable></option></arg>
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<arg choice="plain"><option>-a
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<replaceable>ADDRESS</replaceable></option></arg>
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<arg choice="plain"><option>--port
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<replaceable>PORT</replaceable></option></arg>
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<arg choice="plain"><option>-p
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<replaceable>PORT</replaceable></option></arg>
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<arg><option>--priority
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<replaceable>PRIORITY</replaceable></option></arg>
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<arg><option>--servicename
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<replaceable>NAME</replaceable></option></arg>
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<arg><option>--configdir
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg><option>--debug</option></arg>
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<arg><option>--debuglevel
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<replaceable>LEVEL</replaceable></option></arg>
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<arg><option>--no-dbus</option></arg>
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<arg><option>--no-ipv6</option></arg>
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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>-h</option></arg>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--version</option></arg>
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<command>&COMMANDNAME;</command>
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<arg choice="plain"><option>--check</option></arg>
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<refsect1 id="description">
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<title>DESCRIPTION</title>
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<command>&COMMANDNAME;</command> is a server daemon that handels
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incomming passwords request for passwords. Mandos use avahi to
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announce the service, and through gnutls authenticates
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clients. Any authenticated client is then given its encrypted
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<term><literal>-h</literal>, <literal>--help</literal></term>
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show a help message and exit
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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>-a</literal>, <literal>--address <replaceable>
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ADDRESS</replaceable></literal></term>
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Address to listen for requests on
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<term><literal>-p</literal>, <literal>--port <replaceable>
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PORT</replaceable></literal></term>
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Port number to receive requests on
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<term><literal>--check</literal></term>
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Run self-test on the server
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<term><literal>--debug</literal></term>
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<term><literal>--priority <replaceable>
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PRIORITY</replaceable></literal></term>
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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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<term><literal>--servicename <replaceable>NAME</replaceable>
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Zeroconf service name
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<term><literal>--configdir <replaceable>DIR</replaceable>
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Directory to search for configuration files
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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. For an introduction, see
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<citerefentry><refentrytitle>intro</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>. The Mandos server
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uses Zeroconf to announce itself on the local network, and uses
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TLS to communicate securely with and to authenticate the
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clients. The Mandos server uses IPv6 to allow Mandos clients to
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use IPv6 link-local addresses, since the clients will probably
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not have any other addresses configured (see <xref
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linkend="overview"/>). Any authenticated client is then given
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the stored pre-encrypted password for that specific client.
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<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
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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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<term><option>--help</option></term>
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<term><option>-h</option></term>
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Show a help message and exit
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<term><option>--interface</option>
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<replaceable>NAME</replaceable></term>
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<term><option>-i</option>
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<replaceable>NAME</replaceable></term>
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<xi:include href="mandos-options.xml" xpointer="interface"/>
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<term><option>--address
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<replaceable>ADDRESS</replaceable></option></term>
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<replaceable>ADDRESS</replaceable></option></term>
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<xi:include href="mandos-options.xml" xpointer="address"/>
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<replaceable>PORT</replaceable></option></term>
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<replaceable>PORT</replaceable></option></term>
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<xi:include href="mandos-options.xml" xpointer="port"/>
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<term><option>--check</option></term>
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Run the server’s self-tests. This includes any unit
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<term><option>--debug</option></term>
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<xi:include href="mandos-options.xml" xpointer="debug"/>
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<term><option>--debuglevel
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<replaceable>LEVEL</replaceable></option></term>
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Set the debugging log level.
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<replaceable>LEVEL</replaceable> is a string, one of
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<quote><literal>CRITICAL</literal></quote>,
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<quote><literal>ERROR</literal></quote>,
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<quote><literal>WARNING</literal></quote>,
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<quote><literal>INFO</literal></quote>, or
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<quote><literal>DEBUG</literal></quote>, in order of
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increasing verbosity. The default level is
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<quote><literal>WARNING</literal></quote>.
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<term><option>--priority <replaceable>
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PRIORITY</replaceable></option></term>
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<xi:include href="mandos-options.xml" xpointer="priority"/>
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<term><option>--servicename
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<replaceable>NAME</replaceable></option></term>
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<xi:include href="mandos-options.xml"
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xpointer="servicename"/>
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<term><option>--configdir
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<replaceable>DIRECTORY</replaceable></option></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><option>--version</option></term>
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Prints the program version and exit.
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<term><option>--no-dbus</option></term>
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<xi:include href="mandos-options.xml" xpointer="dbus"/>
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See also <xref linkend="dbus_interface"/>.
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<term><option>--no-ipv6</option></term>
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<xi:include href="mandos-options.xml" xpointer="ipv6"/>
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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 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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<acronym>RAM</acronym> 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\n</literal></quote></entry>
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<entry>-><!-- → --></entry>
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<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
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<entry><-><!-- ⟷ --></entry>
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<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
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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>
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</tbody></tgroup></table>
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<refsect1 id="checking">
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<title>CHECKING</title>
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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. (Manual
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intervention is required to re-enable a client.) The timeout,
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extended timeout, checker program, and interval between checks
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can be configured both globally and per client; see
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<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>. A client successfully
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receiving its password will also be treated as a successful
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<refsect1 id="approval">
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<title>APPROVAL</title>
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The server can be configured to require manual approval for a
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client before it is sent its secret. The delay to wait for such
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approval and the default action (approve or deny) can be
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configured both globally and per client; see <citerefentry>
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<refentrytitle>mandos-clients.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>. By default all clients
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will be approved immediately without delay.
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This can be used to deny a client its secret if not manually
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approved within a specified time. It can also be used to make
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the server delay before giving a client its secret, allowing
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optional manual denying of this specific client.
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<refsect1 id="logging">
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<title>LOGGING</title>
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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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<refsect1 id="dbus_interface">
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<title>D-BUS INTERFACE</title>
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The server will by default provide a D-Bus system bus interface.
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This interface will only be accessible by the root user or a
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Mandos-specific user, if such a user exists. For documentation
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of the D-Bus API, see the file <filename>DBUS-API</filename>.
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<refsect1 id="exit_status">
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<title>EXIT STATUS</title>
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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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<refsect1 id="environment">
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<title>ENVIRONMENT</title>
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<term><envar>PATH</envar></term>
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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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<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
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<refsect1 id="files">
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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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<term><filename>/etc/mandos/mandos.conf</filename></term>
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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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<term><filename>/etc/mandos/clients.conf</filename></term>
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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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<term><filename>/var/run/mandos.pid</filename></term>
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The file containing the process id of the
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<command>&COMMANDNAME;</command> process started last.
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<term><filename>/dev/log</filename></term>
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The Unix domain socket to where local syslog messages are
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<term><filename>/bin/sh</filename></term>
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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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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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Currently, if a client is disabled due to having timed out, the
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server does not record this fact onto permanent storage. This
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has some security implications, see <xref linkend="clients"/>.
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There is no fine-grained control over logging and debug output.
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Debug mode is conflated with running in the foreground.
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The console log messages do not show a time stamp.
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This server does not check the expire time of clients’ OpenPGP
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<refsect1 id="example">
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<title>EXAMPLE</title>
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Normal invocation needs no options:
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<userinput>&COMMANDNAME;</userinput>
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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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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>
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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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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>
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<refsect1 id="security">
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<title>SECURITY</title>
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<refsect2 id="server">
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<title>SERVER</title>
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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 switches to a non-root user
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<refsect2 id="clients">
570
<title>CLIENTS</title>
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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>)
581
<emphasis>must</emphasis> be made non-readable by anyone
582
except the user starting the server (usually root).
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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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If a client is compromised, its downtime should be duly noted
591
by the server which would therefore disable the client. But
592
if the server was ever restarted, it would re-read its client
593
list from its configuration file and again regard all clients
594
therein as enabled, and hence eligible to receive their
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passwords. Therefore, be careful when restarting servers if
596
it is suspected that a client has, in fact, been compromised
597
by parties who may now be running a fake Mandos client with
598
the keys from the non-encrypted initial <acronym>RAM</acronym>
599
image of the client host. What should be done in that case
600
(if restarting the server program really is necessary) is to
601
stop the server program, edit the configuration file to omit
602
any suspect clients, and restart the server program.
605
For more details on client-side security, see
606
<citerefentry><refentrytitle>mandos-client</refentrytitle>
607
<manvolnum>8mandos</manvolnum></citerefentry>.
612
<refsect1 id="see_also">
613
<title>SEE ALSO</title>
615
<citerefentry><refentrytitle>intro</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
618
<manvolnum>5</manvolnum></citerefentry>,
619
<citerefentry><refentrytitle>mandos.conf</refentrytitle>
620
<manvolnum>5</manvolnum></citerefentry>,
621
<citerefentry><refentrytitle>mandos-client</refentrytitle>
622
<manvolnum>8mandos</manvolnum></citerefentry>,
623
<citerefentry><refentrytitle>sh</refentrytitle>
624
<manvolnum>1</manvolnum></citerefentry>
629
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
633
Zeroconf is the network protocol standard used by clients
634
for finding this Mandos server on the local network.
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<ulink url="http://www.avahi.org/">Avahi</ulink>
644
Avahi is the library this server calls to implement
645
Zeroconf service announcements.
651
<ulink url="http://www.gnu.org/software/gnutls/"
656
GnuTLS is the library this server uses to implement TLS for
657
communicating securely with the client, and at the same time
658
confidently get the client’s public OpenPGP key.
664
RFC 4291: <citetitle>IP Version 6 Addressing
665
Architecture</citetitle>
670
<term>Section 2.2: <citetitle>Text Representation of
671
Addresses</citetitle></term>
672
<listitem><para/></listitem>
675
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
676
Address</citetitle></term>
677
<listitem><para/></listitem>
680
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
681
Addresses</citetitle></term>
684
The clients use IPv6 link-local addresses, which are
685
immediately usable since a link-local addresses is
686
automatically assigned to a network interfaces when it
696
RFC 4346: <citetitle>The Transport Layer Security (TLS)
697
Protocol Version 1.1</citetitle>
701
TLS 1.1 is the protocol implemented by GnuTLS.
707
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
711
The data sent to clients is binary encrypted OpenPGP data.
717
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
722
This is implemented by GnuTLS and used by this server so
723
that OpenPGP keys can be used.
730
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