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<holder>Teddy Hogeborn</holder>
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<holder>Björn Påhlsson</holder>
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<holder>Teddy Hogeborn & Björn Påhlsson</holder>
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<xi:include href="legalnotice.xml"/>
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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,
41
either version 3 of the License, or (at your option) any
46
This manual page is distributed in the hope that it will
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be useful, but WITHOUT ANY WARRANTY; without even the
48
implied warranty of MERCHANTABILITY or FITNESS FOR A
49
PARTICULAR PURPOSE. See the GNU General Public License
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You should have received a copy of the GNU General Public
55
License along with this program; If not, see
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<ulink url="http://www.gnu.org/licenses/"/>.
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<refentrytitle>&COMMANDNAME;</refentrytitle>
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<manvolnum>8</manvolnum>
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<manvolnum>8mandos</manvolnum>
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<refname><command>&COMMANDNAME;</command></refname>
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Gives encrypted passwords to authenticated Mandos clients
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Sends encrypted passwords to authenticated mandos clients
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<command>&COMMANDNAME;</command>
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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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<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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<arg choice='opt' rep='repeat'>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 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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<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>--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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<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. 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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<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="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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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
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<command>&COMMANDNAME;</command>.
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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 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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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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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 does 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
489
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 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 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.
515
If a client is compromised, its downtime should be duly noted
516
by the server which would therefore declare the client
517
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 <acronym>RAM</acronym> image of the client host. What
525
should be done in that case (if restarting the server program
526
really is 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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For more details on client-side security, see
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<citerefentry><refentrytitle>mandos-client</refentrytitle>
533
<manvolnum>8mandos</manvolnum></citerefentry>.
538
<refsect1 id="see_also">
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<title>SEE ALSO</title>
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<refentrytitle>mandos-clients.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
544
<refentrytitle>mandos.conf</refentrytitle>
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<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
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<refentrytitle>mandos-client</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
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<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
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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="http://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="http://www.gnu.org/software/gnutls/"
581
GnuTLS is the library this server uses to implement TLS for
582
communicating securely with the client, and at the same time
583
confidently get the client’s public OpenPGP key.
589
RFC 4291: <citetitle>IP Version 6 Addressing
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Architecture</citetitle>
595
<term>Section 2.2: <citetitle>Text Representation of
596
Addresses</citetitle></term>
597
<listitem><para/></listitem>
600
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
601
Address</citetitle></term>
602
<listitem><para/></listitem>
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<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
606
Addresses</citetitle></term>
609
The clients use IPv6 link-local addresses, which are
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immediately usable since a link-local addresses is
611
automatically assigned to a network interfaces when it
621
RFC 4346: <citetitle>The Transport Layer Security (TLS)
622
Protocol Version 1.1</citetitle>
626
TLS 1.1 is the protocol implemented by GnuTLS.
632
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
636
The data sent to clients is binary encrypted OpenPGP data.
642
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
647
This is implemented by GnuTLS and used by this server so
648
that OpenPGP keys can be used.
83
<command>&COMMANDNAME;</command> is a server daemon that handels
84
incomming passwords request for passwords. Mandos use avahi to
85
announce the service, and through gnutls authenticates
86
clients. Any authenticated client is then given its encrypted
92
<term><literal>-h</literal>, <literal>--help</literal></term>
95
show a help message and exit
101
<term><literal>-i</literal>, <literal>--interface <replaceable>
102
IF</replaceable></literal></term>
111
<term><literal>-a</literal>, <literal>--address <replaceable>
112
ADDRESS</replaceable></literal></term>
115
Address to listen for requests on
121
<term><literal>-p</literal>, <literal>--port <replaceable>
122
PORT</replaceable></literal></term>
125
Port number to receive requests on
131
<term><literal>--check</literal></term>
134
Run self-test on the server
140
<term><literal>--debug</literal></term>
149
<term><literal>--priority <replaceable>
150
PRIORITY</replaceable></literal></term>
153
GnuTLS priority string. See <citerefentry>
154
<refentrytitle>gnutls_priority_init</refentrytitle>
155
<manvolnum>3</manvolnum></citerefentry>
161
<term><literal>--servicename <replaceable>NAME</replaceable>
165
Zeroconf service name
171
<term><literal>--configdir <replaceable>DIR</replaceable>
175
Directory to search for configuration files
655
<!-- Local Variables: -->
656
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
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<!-- time-stamp-end: "[\"']>" -->
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<!-- time-stamp-format: "%:y-%02m-%02d" -->