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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
39
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
47
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
54
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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62
<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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<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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<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>--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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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>. 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.
376
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
437
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>
484
<refentrytitle>mandos-clients.conf</refentrytitle>
485
<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
545
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
562
should not in itself present any security risk to the host
563
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
571
does have the OpenPGP key of the stored fingerprint. This is
572
guaranteed by the fact that the client sends its OpenPGP
573
public key in the TLS handshake; this ensures it to be
574
genuine. The server computes the fingerprint of the key
575
itself and looks up the fingerprint in its list of
576
clients. The <filename>clients.conf</filename> file (see
577
<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
578
<manvolnum>5</manvolnum></citerefentry>)
579
<emphasis>must</emphasis> be made non-readable by anyone
580
except the user starting the server (usually root).
583
As detailed in <xref linkend="checking"/>, the status of all
584
client computers will continually be checked and be assumed
585
compromised if they are gone for too long.
588
If a client is compromised, its downtime should be duly noted
589
by the server which would therefore disable the client. But
590
if the server was ever restarted, it would re-read its client
591
list from its configuration file and again regard all clients
592
therein as enabled, and hence eligible to receive their
593
passwords. Therefore, be careful when restarting servers if
594
it is suspected that a client has, in fact, been compromised
595
by parties who may now be running a fake Mandos client with
596
the keys from the non-encrypted initial <acronym>RAM</acronym>
597
image of the client host. What should be done in that case
598
(if restarting the server program really is necessary) is to
599
stop the server program, edit the configuration file to omit
600
any suspect clients, and restart the server program.
603
For more details on client-side security, see
604
<citerefentry><refentrytitle>mandos-client</refentrytitle>
605
<manvolnum>8mandos</manvolnum></citerefentry>.
610
<refsect1 id="see_also">
611
<title>SEE ALSO</title>
614
<refentrytitle>mandos-clients.conf</refentrytitle>
615
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
616
<refentrytitle>mandos.conf</refentrytitle>
617
<manvolnum>5</manvolnum></citerefentry>, <citerefentry>
618
<refentrytitle>mandos-client</refentrytitle>
619
<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
620
<refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
626
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
630
Zeroconf is the network protocol standard used by clients
631
for finding this Mandos server on the local network.
637
<ulink url="http://www.avahi.org/">Avahi</ulink>
641
Avahi is the library this server calls to implement
642
Zeroconf service announcements.
648
<ulink url="http://www.gnu.org/software/gnutls/"
653
GnuTLS is the library this server uses to implement TLS for
654
communicating securely with the client, and at the same time
655
confidently get the client’s public OpenPGP key.
661
RFC 4291: <citetitle>IP Version 6 Addressing
662
Architecture</citetitle>
667
<term>Section 2.2: <citetitle>Text Representation of
668
Addresses</citetitle></term>
669
<listitem><para/></listitem>
672
<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
673
Address</citetitle></term>
674
<listitem><para/></listitem>
677
<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
678
Addresses</citetitle></term>
681
The clients use IPv6 link-local addresses, which are
682
immediately usable since a link-local addresses is
683
automatically assigned to a network interfaces when it
693
RFC 4346: <citetitle>The Transport Layer Security (TLS)
694
Protocol Version 1.1</citetitle>
698
TLS 1.1 is the protocol implemented by GnuTLS.
704
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
708
The data sent to clients is binary encrypted OpenPGP data.
714
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
719
This is implemented by GnuTLS and used by this server so
720
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
727
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