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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY COMMANDNAME "mandos">
<!ENTITY TIMESTAMP "2019-02-10">
<!ENTITY % common SYSTEM "common.ent">
%common;
]>

<refentry xmlns:xi="http://www.w3.org/2001/XInclude">
   <refentryinfo>
    <title>Mandos Manual</title>
    <!-- NWalsh’s docbook scripts use this to generate the footer: -->
    <productname>Mandos</productname>
    <productnumber>&version;</productnumber>
    <date>&TIMESTAMP;</date>
    <authorgroup>
      <author>
	<firstname>Björn</firstname>
	<surname>Påhlsson</surname>
	<address>
	  <email>belorn@recompile.se</email>
	</address>
      </author>
      <author>
	<firstname>Teddy</firstname>
	<surname>Hogeborn</surname>
	<address>
	  <email>teddy@recompile.se</email>
	</address>
      </author>
    </authorgroup>
    <copyright>
      <year>2008</year>
      <year>2009</year>
      <year>2010</year>
      <year>2011</year>
      <year>2012</year>
      <year>2013</year>
      <year>2014</year>
      <year>2015</year>
      <year>2016</year>
      <year>2017</year>
      <year>2018</year>
      <year>2019</year>
      <holder>Teddy Hogeborn</holder>
      <holder>Björn Påhlsson</holder>
    </copyright>
    <xi:include href="legalnotice.xml"/>
  </refentryinfo>
  
  <refmeta>
    <refentrytitle>&COMMANDNAME;</refentrytitle>
    <manvolnum>8</manvolnum>
  </refmeta>
  
  <refnamediv>
    <refname><command>&COMMANDNAME;</command></refname>
    <refpurpose>
      Gives encrypted passwords to authenticated Mandos clients
    </refpurpose>
  </refnamediv>
  
  <refsynopsisdiv>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <group>
	<arg choice="plain"><option>--interface
	<replaceable>NAME</replaceable></option></arg>
	<arg choice="plain"><option>-i
	<replaceable>NAME</replaceable></option></arg>
      </group>
      <sbr/>
      <group>
	<arg choice="plain"><option>--address
	<replaceable>ADDRESS</replaceable></option></arg>
	<arg choice="plain"><option>-a
	<replaceable>ADDRESS</replaceable></option></arg>
      </group>
      <sbr/>
      <group>
	<arg choice="plain"><option>--port
	<replaceable>PORT</replaceable></option></arg>
	<arg choice="plain"><option>-p
	<replaceable>PORT</replaceable></option></arg>
      </group>
      <sbr/>
      <arg><option>--priority
      <replaceable>PRIORITY</replaceable></option></arg>
      <sbr/>
      <arg><option>--servicename
      <replaceable>NAME</replaceable></option></arg>
      <sbr/>
      <arg><option>--configdir
      <replaceable>DIRECTORY</replaceable></option></arg>
      <sbr/>
      <arg><option>--debug</option></arg>
      <sbr/>
      <arg><option>--debuglevel
      <replaceable>LEVEL</replaceable></option></arg>
      <sbr/>
      <arg><option>--no-dbus</option></arg>
      <sbr/>
      <arg><option>--no-ipv6</option></arg>
      <sbr/>
      <arg><option>--no-restore</option></arg>
      <sbr/>
      <arg><option>--statedir
      <replaceable>DIRECTORY</replaceable></option></arg>
      <sbr/>
      <arg><option>--socket
      <replaceable>FD</replaceable></option></arg>
      <sbr/>
      <arg><option>--foreground</option></arg>
      <sbr/>
      <arg><option>--no-zeroconf</option></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <group choice="req">
	<arg choice="plain"><option>--help</option></arg>
	<arg choice="plain"><option>-h</option></arg>
      </group>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <arg choice="plain"><option>--version</option></arg>
    </cmdsynopsis>
    <cmdsynopsis>
      <command>&COMMANDNAME;</command>
      <arg choice="plain"><option>--check</option></arg>
    </cmdsynopsis>
  </refsynopsisdiv>
  
  <refsect1 id="description">
    <title>DESCRIPTION</title>
    <para>
      <command>&COMMANDNAME;</command> is a server daemon which
      handles incoming request for passwords for a pre-defined list of
      client host computers. For an introduction, see
      <citerefentry><refentrytitle>intro</refentrytitle>
      <manvolnum>8mandos</manvolnum></citerefentry>. The Mandos server
      uses Zeroconf to announce itself on the local network, and uses
      TLS to communicate securely with and to authenticate the
      clients.  The Mandos server uses IPv6 to allow Mandos clients to
      use IPv6 link-local addresses, since the clients will probably
      not have any other addresses configured (see <xref
      linkend="overview"/>).  Any authenticated client is then given
      the stored pre-encrypted password for that specific client.
    </para>
  </refsect1>
  
  <refsect1 id="purpose">
    <title>PURPOSE</title>
    <para>
      The purpose of this is to enable <emphasis>remote and unattended
      rebooting</emphasis> of client host computer with an
      <emphasis>encrypted root file system</emphasis>.  See <xref
      linkend="overview"/> for details.
    </para>
  </refsect1>
  
  <refsect1 id="options">
    <title>OPTIONS</title>
    <variablelist>
      <varlistentry>
	<term><option>--help</option></term>
	<term><option>-h</option></term>
	<listitem>
	  <para>
	    Show a help message and exit
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--interface</option>
	<replaceable>NAME</replaceable></term>
	<term><option>-i</option>
	<replaceable>NAME</replaceable></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="interface"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--address
	<replaceable>ADDRESS</replaceable></option></term>
	<term><option>-a
	<replaceable>ADDRESS</replaceable></option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="address"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--port
	<replaceable>PORT</replaceable></option></term>
	<term><option>-p
	<replaceable>PORT</replaceable></option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="port"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--check</option></term>
	<listitem>
	  <para>
	    Run the server’s self-tests.  This includes any unit
	    tests, etc.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--debug</option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="debug"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--debuglevel
	<replaceable>LEVEL</replaceable></option></term>
	<listitem>
	  <para>
	    Set the debugging log level.
	    <replaceable>LEVEL</replaceable> is a string, one of
	    <quote><literal>CRITICAL</literal></quote>,
	    <quote><literal>ERROR</literal></quote>,
	    <quote><literal>WARNING</literal></quote>,
	    <quote><literal>INFO</literal></quote>, or
	    <quote><literal>DEBUG</literal></quote>, in order of
	    increasing verbosity.  The default level is
	    <quote><literal>WARNING</literal></quote>.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--priority <replaceable>
	PRIORITY</replaceable></option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="priority"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--servicename
	<replaceable>NAME</replaceable></option></term>
	<listitem>
	  <xi:include href="mandos-options.xml"
		      xpointer="servicename"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--configdir
	<replaceable>DIRECTORY</replaceable></option></term>
	<listitem>
	  <para>
	    Directory to search for configuration files.  Default is
	    <quote><literal>/etc/mandos</literal></quote>.  See
	    <citerefentry><refentrytitle>mandos.conf</refentrytitle>
	    <manvolnum>5</manvolnum></citerefentry> and <citerefentry>
	    <refentrytitle>mandos-clients.conf</refentrytitle>
	    <manvolnum>5</manvolnum></citerefentry>.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--version</option></term>
	<listitem>
	  <para>
	    Prints the program version and exit.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--no-dbus</option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="dbus"/>
	  <para>
	    See also <xref linkend="dbus_interface"/>.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--no-ipv6</option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="ipv6"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--no-restore</option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="restore"/>
	  <para>
	    See also <xref linkend="persistent_state"/>.
	  </para>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--statedir
	<replaceable>DIRECTORY</replaceable></option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="statedir"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--socket
	<replaceable>FD</replaceable></option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="socket"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--foreground</option></term>
	<listitem>
	  <xi:include href="mandos-options.xml"
		      xpointer="foreground"/>
	</listitem>
      </varlistentry>
      
      <varlistentry>
	<term><option>--no-zeroconf</option></term>
	<listitem>
	  <xi:include href="mandos-options.xml" xpointer="zeroconf"/>
	</listitem>
      </varlistentry>
      
    </variablelist>
  </refsect1>
  
  <refsect1 id="overview">
    <title>OVERVIEW</title>
    <xi:include href="overview.xml"/>
    <para>
      This program is the server part.  It is a normal server program
      and will run in a normal system environment, not in an initial
      <acronym>RAM</acronym> disk environment.
    </para>
  </refsect1>
  
  <refsect1 id="protocol">
    <title>NETWORK PROTOCOL</title>
    <para>
      The Mandos server announces itself as a Zeroconf service of type
      <quote><literal>_mandos._tcp</literal></quote>.  The Mandos
      client connects to the announced address and port, and sends a
      line of text where the first whitespace-separated field is the
      protocol version, which currently is
      <quote><literal>1</literal></quote>.  The client and server then
      start a TLS protocol handshake with a slight quirk: the Mandos
      server program acts as a TLS <quote>client</quote> while the
      connecting Mandos client acts as a TLS <quote>server</quote>.
      The Mandos client must supply a TLS public key, and the key ID
      of this public key is used by the Mandos server to look up (in a
      list read from <filename>clients.conf</filename> at start time)
      which binary blob to give the client.  No other authentication
      or authorization is done by the server.
    </para>
    <table>
      <title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>
      <row>
	<entry>Mandos Client</entry>
	<entry>Direction</entry>
	<entry>Mandos Server</entry>
      </row>
      </thead><tbody>
      <row>
	<entry>Connect</entry>
	<entry>-><!-- &rarr; --></entry>
      </row>
      <row>
	<entry><quote><literal>1\r\n</literal></quote></entry>
	<entry>-><!-- &rarr; --></entry>
      </row>
      <row>
	<entry>TLS handshake <emphasis>as TLS <quote>server</quote>
	</emphasis></entry>
	<entry>&lt;-><!-- &xharr; --></entry>
	<entry>TLS handshake <emphasis>as TLS <quote>client</quote>
	</emphasis></entry>
      </row>
      <row>
	<entry>Public key (part of TLS handshake)</entry>
	<entry>-><!-- &rarr; --></entry>
      </row>
      <row>
	<entry/>
	<entry>&lt;-<!-- &larr; --></entry>
	<entry>Binary blob (client will assume OpenPGP data)</entry>
      </row>
      <row>
	<entry/>
	<entry>&lt;-<!-- &larr; --></entry>
	<entry>Close</entry>
      </row>
    </tbody></tgroup></table>
  </refsect1>
  
  <refsect1 id="checking">
    <title>CHECKING</title>
    <para>
      The server will, by default, continually check that the clients
      are still up.  If a client has not been confirmed as being up
      for some time, the client is assumed to be compromised and is no
      longer eligible to receive the encrypted password.  (Manual
      intervention is required to re-enable a client.)  The timeout,
      extended timeout, checker program, and interval between checks
      can be configured both globally and per client; see
      <citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry>.
    </para>
  </refsect1>
  
  <refsect1 id="approval">
    <title>APPROVAL</title>
    <para>
      The server can be configured to require manual approval for a
      client before it is sent its secret.  The delay to wait for such
      approval and the default action (approve or deny) can be
      configured both globally and per client; see <citerefentry>
      <refentrytitle>mandos-clients.conf</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry>.  By default all clients
      will be approved immediately without delay.
    </para>
    <para>
      This can be used to deny a client its secret if not manually
      approved within a specified time.  It can also be used to make
      the server delay before giving a client its secret, allowing
      optional manual denying of this specific client.
    </para>
    
  </refsect1>
  
  <refsect1 id="logging">
    <title>LOGGING</title>
    <para>
      The server will send log message with various severity levels to
      <filename class="devicefile">/dev/log</filename>.  With the
      <option>--debug</option> option, it will log even more messages,
      and also show them on the console.
    </para>
  </refsect1>
  
  <refsect1 id="persistent_state">
    <title>PERSISTENT STATE</title>
    <para>
      Client settings, initially read from
      <filename>clients.conf</filename>, are persistent across
      restarts, and run-time changes will override settings in
      <filename>clients.conf</filename>.  However, if a setting is
      <emphasis>changed</emphasis> (or a client added, or removed) in
      <filename>clients.conf</filename>, this will take precedence.
    </para>
  </refsect1>
  
  <refsect1 id="dbus_interface">
    <title>D-BUS INTERFACE</title>
    <para>
      The server will by default provide a D-Bus system bus interface.
      This interface will only be accessible by the root user or a
      Mandos-specific user, if such a user exists.  For documentation
      of the D-Bus API, see the file <filename>DBUS-API</filename>.
    </para>
  </refsect1>
  
  <refsect1 id="exit_status">
    <title>EXIT STATUS</title>
    <para>
      The server will exit with a non-zero exit status only when a
      critical error is encountered.
    </para>
  </refsect1>
  
  <refsect1 id="environment">
    <title>ENVIRONMENT</title>
    <variablelist>
      <varlistentry>
	<term><envar>PATH</envar></term>
	<listitem>
	  <para>
	    To start the configured checker (see <xref
	    linkend="checking"/>), the server uses
	    <filename>/bin/sh</filename>, which in turn uses
	    <varname>PATH</varname> to search for matching commands if
	    an absolute path is not given.  See <citerefentry>
	    <refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
	    </citerefentry>.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
  
  <refsect1 id="files">
    <title>FILES</title>
    <para>
      Use the <option>--configdir</option> option to change where
      <command>&COMMANDNAME;</command> looks for its configurations
      files.  The default file names are listed here.
    </para>
    <variablelist>
      <varlistentry>
	<term><filename>/etc/mandos/mandos.conf</filename></term>
	<listitem>
	  <para>
	    Server-global settings.  See
	    <citerefentry><refentrytitle>mandos.conf</refentrytitle>
	    <manvolnum>5</manvolnum></citerefentry> for details.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/etc/mandos/clients.conf</filename></term>
	<listitem>
	  <para>
	    List of clients and client-specific settings.  See
	    <citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
	    <manvolnum>5</manvolnum></citerefentry> for details.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/run/mandos.pid</filename></term>
	<listitem>
	  <para>
	    The file containing the process id of the
	    <command>&COMMANDNAME;</command> process started last.
	    <emphasis >Note:</emphasis> If the <filename
	    class="directory">/run</filename> directory does not
	    exist, <filename>/var/run/mandos.pid</filename> will be
	    used instead.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename
	class="directory">/var/lib/mandos</filename></term>
	<listitem>
	  <para>
	    Directory where persistent state will be saved.  Change
	    this with the <option>--statedir</option> option.  See
	    also the <option>--no-restore</option> option.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename class="devicefile">/dev/log</filename></term>
	<listitem>
	  <para>
	    The Unix domain socket to where local syslog messages are
	    sent.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><filename>/bin/sh</filename></term>
	<listitem>
	  <para>
	    This is used to start the configured checker command for
	    each client.  See <citerefentry>
	    <refentrytitle>mandos-clients.conf</refentrytitle>
	    <manvolnum>5</manvolnum></citerefentry> for details.
	  </para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
  
  <refsect1 id="bugs">
    <title>BUGS</title>
    <para>
      This server might, on especially fatal errors, emit a Python
      backtrace.  This could be considered a feature.
    </para>
    <para>
      There is no fine-grained control over logging and debug output.
    </para>
    <xi:include href="bugs.xml"/>
  </refsect1>
  
  <refsect1 id="example">
    <title>EXAMPLE</title>
    <informalexample>
      <para>
	Normal invocation needs no options:
      </para>
      <para>
	<userinput>&COMMANDNAME;</userinput>
      </para>
    </informalexample>
    <informalexample>
      <para>
	Run the server in debug mode, read configuration files from
	the <filename class="directory">~/mandos</filename> directory,
	and use the Zeroconf service name <quote>Test</quote> to not
	collide with any other official Mandos server on this host:
      </para>
      <para>

<!-- do not wrap this line -->
<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>

      </para>
    </informalexample>
    <informalexample>
      <para>
	Run the server normally, but only listen to one interface and
	only on the link-local address on that interface:
      </para>
      <para>

<!-- do not wrap this line -->
<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>

      </para>
    </informalexample>
  </refsect1>
  
  <refsect1 id="security">
    <title>SECURITY</title>
    <refsect2 id="server">
      <title>SERVER</title>
      <para>
	Running this <command>&COMMANDNAME;</command> server program
	should not in itself present any security risk to the host
	computer running it.  The program switches to a non-root user
	soon after startup.
      </para>
    </refsect2>
    <refsect2 id="clients">
      <title>CLIENTS</title>
      <para>
	The server only gives out its stored data to clients which
	does have the correct key ID of the stored key ID.  This is
	guaranteed by the fact that the client sends its public key in
	the TLS handshake; this ensures it to be genuine.  The server
	computes the key ID of the key itself and looks up the key ID
	in its list of clients. The <filename>clients.conf</filename>
	file (see
	<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
	<manvolnum>5</manvolnum></citerefentry>)
	<emphasis>must</emphasis> be made non-readable by anyone
	except the user starting the server (usually root).
      </para>
      <para>
	As detailed in <xref linkend="checking"/>, the status of all
	client computers will continually be checked and be assumed
	compromised if they are gone for too long.
      </para>
      <para>
	For more details on client-side security, see
	<citerefentry><refentrytitle>mandos-client</refentrytitle>
	<manvolnum>8mandos</manvolnum></citerefentry>.
      </para>
    </refsect2>
  </refsect1>
  
  <refsect1 id="see_also">
    <title>SEE ALSO</title>
    <para>
      <citerefentry><refentrytitle>intro</refentrytitle>
      <manvolnum>8mandos</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>mandos.conf</refentrytitle>
      <manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>mandos-client</refentrytitle>
      <manvolnum>8mandos</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sh</refentrytitle>
      <manvolnum>1</manvolnum></citerefentry>
    </para>
    <variablelist>
      <varlistentry>
	<term>
	  <ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
	</term>
	<listitem>
	  <para>
	    Zeroconf is the network protocol standard used by clients
	    for finding this Mandos server on the local network.
	  </para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <ulink url="http://www.avahi.org/">Avahi</ulink>
	</term>
      <listitem>
	<para>
	  Avahi is the library this server calls to implement
	  Zeroconf service announcements.
	</para>
      </listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  <ulink url="https://gnutls.org/">GnuTLS</ulink>
	</term>
      <listitem>
	<para>
	  GnuTLS is the library this server uses to implement TLS for
	  communicating securely with the client, and at the same time
	  confidently get the client’s public key.
	</para>
      </listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  RFC 4291: <citetitle>IP Version 6 Addressing
	  Architecture</citetitle>
	</term>
	<listitem>
	  <variablelist>
	    <varlistentry>
	      <term>Section 2.2: <citetitle>Text Representation of
	      Addresses</citetitle></term>
	      <listitem><para/></listitem>
	    </varlistentry>
	    <varlistentry>
	      <term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6
	      Address</citetitle></term>
	      <listitem><para/></listitem>
	    </varlistentry>
	    <varlistentry>
	    <term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast
	    Addresses</citetitle></term>
	    <listitem>
	      <para>
		The clients use IPv6 link-local addresses, which are
		immediately usable since a link-local addresses is
		automatically assigned to a network interfaces when it
		is brought up.
	      </para>
	    </listitem>
	    </varlistentry>
	  </variablelist>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  RFC 5246: <citetitle>The Transport Layer Security (TLS)
	  Protocol Version 1.2</citetitle>
	</term>
      <listitem>
	<para>
	  TLS 1.2 is the protocol implemented by GnuTLS.
	</para>
      </listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
	</term>
      <listitem>
	<para>
	  The data sent to clients is binary encrypted OpenPGP data.
	</para>
      </listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  RFC 7250: <citetitle>Using Raw Public Keys in Transport
	  Layer Security (TLS) and Datagram Transport Layer Security
	  (DTLS)</citetitle>
	</term>
      <listitem>
	<para>
	  This is implemented by GnuTLS version 3.6.6 and is, if
	  present, used by this server so that raw public keys can be
	  used.
	</para>
      </listitem>
      </varlistentry>
      <varlistentry>
	<term>
	  RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
	  Security (TLS) Authentication</citetitle>
	</term>
      <listitem>
	<para>
	  This is implemented by GnuTLS before version 3.6.0 and is,
	  if present, used by this server so that OpenPGP keys can be
	  used.
	</para>
      </listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>
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