/mandos/release

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<!ENTITY COMMANDNAME "mandos">

<!ENTITY TIMESTAMP "2011-10-22">

<!ENTITY % common SYSTEM "common.ent">

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<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>

      <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>

    </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"/>

	</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 an OpenPGP certificate, and the

      fingerprint of this certificate 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>OpenPGP 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>.  A client successfully

      receiving its password will also be treated as a successful

      checker run.

    </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>/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="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>/var/run/mandos.pid</filename></term>

	<listitem>

	  <para>

	    The file containing the process id of the

	    <command>&COMMANDNAME;</command> process started last.

	  </para>

	</listitem>

      </varlistentry>

      <varlistentry>

	<term><filename>/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>

      Currently, if a client is disabled due to having timed out, the

      server does not record this fact onto permanent storage.  This

      has some security implications, see <xref linkend="clients"/>.

    </para>

    <para>

      There is no fine-grained control over logging and debug output.

    </para>

    <para>

      Debug mode is conflated with running in the foreground.

    </para>

    <para>

      This server does not check the expire time of clients’ OpenPGP

      keys.

    </para>

  </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>~/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 OpenPGP key of the stored fingerprint.  This is

	guaranteed by the fact that the client sends its OpenPGP

	public key in the TLS handshake; this ensures it to be

	genuine.  The server computes the fingerprint of the key

	itself and looks up the fingerprint 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>

	If a client is compromised, its downtime should be duly noted

	by the server which would therefore disable the client.  But

	if the server was ever restarted, it would re-read its client

	list from its configuration file and again regard all clients

	therein as enabled, and hence eligible to receive their

	passwords.  Therefore, be careful when restarting servers if

	it is suspected that a client has, in fact, been compromised

	by parties who may now be running a fake Mandos client with

	the keys from the non-encrypted initial <acronym>RAM</acronym>

	image of the client host.  What should be done in that case

	(if restarting the server program really is necessary) is to

	stop the server program, edit the configuration file to omit

	any suspect clients, and restart the server program.

      </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="http://www.gnu.org/software/gnutls/"

	  >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 OpenPGP key.

	</para>

      </listitem>

      </varlistentry>

      <varlistentry>

	<term>

	  RFC 4291: <citetitle>IP Version 6 Addressing

	  Architecture</citetitle>

	</term>

	<listitem>

	  <variablelist>

	    <varlistentry>