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<!ENTITY COMMANDNAME "mandos">
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<!ENTITY TIMESTAMP "2022-04-24">
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<!ENTITY % common SYSTEM "common.ent">
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<title>&COMMANDNAME;</title>
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<!-- NWalsh's docbook scripts use this to generate the footer: -->
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<productname>&COMMANDNAME;</productname>
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<productnumber>&VERSION;</productnumber>
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<refentry xmlns:xi="http://www.w3.org/2001/XInclude">
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<title>Mandos Manual</title>
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<!-- NWalsh’s docbook scripts use this to generate the footer: -->
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<productname>Mandos</productname>
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<productnumber>&version;</productnumber>
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<date>&TIMESTAMP;</date>
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<firstname>Björn</firstname>
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<surname>Påhlsson</surname>
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<email>belorn@fukt.bsnet.se</email>
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<email>belorn@recompile.se</email>
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<firstname>Teddy</firstname>
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<surname>Hogeborn</surname>
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<email>teddy@fukt.bsnet.se</email>
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<email>teddy@recompile.se</email>
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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
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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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<arg><option>--no-restore</option></arg>
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<arg><option>--statedir
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<replaceable>DIRECTORY</replaceable></option></arg>
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<arg><option>--socket
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<replaceable>FD</replaceable></option></arg>
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<arg><option>--foreground</option></arg>
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<arg><option>--no-zeroconf</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 requests for passwords for a pre-defined list
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of 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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<term><option>--no-restore</option></term>
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<xi:include href="mandos-options.xml" xpointer="restore"/>
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See also <xref linkend="persistent_state"/>.
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<term><option>--statedir
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<replaceable>DIRECTORY</replaceable></option></term>
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<xi:include href="mandos-options.xml" xpointer="statedir"/>
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<term><option>--socket
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<replaceable>FD</replaceable></option></term>
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<xi:include href="mandos-options.xml" xpointer="socket"/>
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<term><option>--foreground</option></term>
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<xi:include href="mandos-options.xml"
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xpointer="foreground"/>
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<term><option>--no-zeroconf</option></term>
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<xi:include href="mandos-options.xml" xpointer="zeroconf"/>
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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 a TLS public key, and the key ID
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of this public key is used by the Mandos server to look up (in a
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list read from <filename>clients.conf</filename> at start time)
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which binary blob to give the client. No other authentication
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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>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>.
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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 class="devicefile">/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="persistent_state">
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<title>PERSISTENT STATE</title>
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Client settings, initially read from
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<filename>clients.conf</filename>, are persistent across
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restarts, and run-time changes will override settings in
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<filename>clients.conf</filename>. However, if a setting is
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<emphasis>changed</emphasis> (or a client added, or removed) in
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<filename>clients.conf</filename>, this will take precedence.
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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>/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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<emphasis >Note:</emphasis> If the <filename
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class="directory">/run</filename> directory does not
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exist, <filename>/var/run/mandos.pid</filename> will be
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class="directory">/var/lib/mandos</filename></term>
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Directory where persistent state will be saved. Change
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this with the <option>--statedir</option> option. See
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also the <option>--no-restore</option> option.
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<term><filename class="devicefile">/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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There is no fine-grained control over logging and debug output.
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<xi:include href="bugs.xml"/>
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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 class="directory">~/mandos</filename> directory,
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and use the Zeroconf service name <quote>Test</quote> to not
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collide with 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">
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<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 correct key ID of the stored key ID. This is
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guaranteed by the fact that the client sends its public key in
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the TLS handshake; this ensures it to be genuine. The server
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computes the key ID of the key itself and looks up the key ID
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in its list of clients. The <filename>clients.conf</filename>
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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 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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For more details on client-side security, see
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<citerefentry><refentrytitle>mandos-client</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>.
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<refsect1 id="see_also">
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<title>SEE ALSO</title>
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<citerefentry><refentrytitle>intro</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>mandos.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>mandos-client</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sh</refentrytitle>
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<manvolnum>1</manvolnum></citerefentry>
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<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
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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.
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<ulink url="https://www.avahi.org/">Avahi</ulink>
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Avahi is the library this server calls to implement
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Zeroconf service announcements.
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<ulink url="https://gnutls.org/">GnuTLS</ulink>
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GnuTLS is the library this server uses to implement TLS for
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communicating securely with the client, and at the same time
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confidently get the client’s public key.
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RFC 4291: <citetitle>IP Version 6 Addressing
722
Architecture</citetitle>
727
<term>Section 2.2: <citetitle>Text Representation of
728
Addresses</citetitle></term>
729
<listitem><para/></listitem>
732
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
733
Address</citetitle></term>
734
<listitem><para/></listitem>
737
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
738
Addresses</citetitle></term>
741
The clients use IPv6 link-local addresses, which are
742
immediately usable since a link-local address is
743
automatically assigned to a network interfaces when it
753
RFC 5246: <citetitle>The Transport Layer Security (TLS)
754
Protocol Version 1.2</citetitle>
758
TLS 1.2 is the protocol implemented by GnuTLS.
764
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
768
The data sent to clients is binary encrypted OpenPGP data.
774
RFC 7250: <citetitle>Using Raw Public Keys in Transport
775
Layer Security (TLS) and Datagram Transport Layer Security
780
This is implemented by GnuTLS version 3.6.6 and is, if
781
present, used by this server so that raw public keys can be
788
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
789
Security (TLS) Authentication</citetitle>
793
This is implemented by GnuTLS before version 3.6.0 and is,
794
if present, used by this server so that OpenPGP keys can be
802
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