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Committer: Teddy Hogeborn
Date: 2008-08-16 20:32:58 UTC
mfrom: (24.1.55 mandos)
Revision ID: teddy@fukt.bsnet.se-20080816203258-eq4by31vdgxkhs9g

* mandos-keygen.xml: New man page for mandos-keygen(8).

files added:
network-protocol.txt

files removed:
overview.xml

files modified:
Makefile

TODO

mandos-keygen.xml

mandos.xml

plugins.d/password-request.c

plugins.d/password-request.xml

Show diffs side-by-side

added added

removed removed

mandos.xml

<?xml version="1.0" encoding="UTF-8"?>

<?xml version='1.0' encoding='UTF-8'?>

<?xml-stylesheet type="text/xsl"

href="http://docbook.sourceforge.net/release/xsl/current/manpages/docbook.xsl"?>

<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"

"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [

<!ENTITY VERSION "1.0">

<!ENTITY COMMANDNAME "mandos">

<!ENTITY OVERVIEW SYSTEM "overview.xml">

<title>&COMMANDNAME;</title>

<productname>&COMMANDNAME;</productname>

<productnumber>&VERSION;</productnumber>

</authorgroup>

<holder>Teddy Hogeborn</holder>

<holder>Björn Påhlsson</holder>

<holder>Teddy Hogeborn & Björn Påhlsson</holder>

</copyright>

<para>

<refname><command>&COMMANDNAME;</command></refname>

Sends encrypted passwords to authenticated Mandos clients

Sends encrypted passwords to authenticated mandos clients

</refpurpose>

</refnamediv>

<command>&COMMANDNAME;</command>

<arg>--interface<arg choice="plain">IF</arg></arg>

<arg>--address<arg choice="plain">ADDRESS</arg></arg>

<arg>--priority<arg choice="plain">PRIORITY</arg></arg>

<arg>--servicename<arg choice="plain">NAME</arg></arg>

<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>

<arg>--debug</arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

<arg>-a<arg choice="plain">ADDRESS</arg></arg>

<arg>--priority<arg choice="plain">PRIORITY</arg></arg>

<arg>--servicename<arg choice="plain">NAME</arg></arg>

<arg>--configdir<arg choice="plain">DIRECTORY</arg></arg>

<arg>--debug</arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

</group>

100

</cmdsynopsis>

101

102

<command>&COMMANDNAME;</command>

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<arg choice="plain">--version</arg>

104

</cmdsynopsis>

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<command>&COMMANDNAME;</command>

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<arg choice="plain">--check</arg>

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</cmdsynopsis>

<arg choice='opt'>--interface<arg choice='plain'>IF</arg></arg>

<arg choice='opt'>--address<arg choice='plain'>ADDRESS</arg></arg>

<arg choice='opt'>--priority<arg choice='plain'>PRIORITY</arg></arg>

<arg choice='opt'>--servicename<arg choice='plain'>NAME</arg></arg>

<arg choice='opt'>--configdir<arg choice='plain'>DIRECTORY</arg></arg>

<arg choice='opt'>--debug</arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

<arg choice='plain'>--version</arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

<arg choice='plain'>--check</arg>

</cmdsynopsis>

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</refsynopsisdiv>

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<title>DESCRIPTION</title>

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<para>

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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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</para>

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</refsect1>

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<title>PURPOSE</title>

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<para>

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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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</para>

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</refsect1>

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<command>&COMMANDNAME;</command> is a server daemon that handels

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incomming passwords request for passwords. Mandos use avahi to

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announce the service, and through gnutls authenticates

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clients. Any authenticated client is then given its encrypted

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password.

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</para>

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</refsect1>

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<title>OPTIONS</title>

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<para>

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Show a help message and exit

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show a help message and exit

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</para>

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</listitem>

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</varlistentry>

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IF</replaceable></literal></term>

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<para>

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Only announce the server and listen to requests on network

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interface <replaceable>IF</replaceable>. Default is to

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use all available interfaces. <emphasis>Note:</emphasis>

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a failure to bind to the specified interface is not

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considered critical, and the server does not exit.

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Bind to interface IF

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>-a</literal>, <literal>--address <replaceable>

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ADDRESS</replaceable></literal></term>

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<para>

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If this option is used, the server will only listen to a

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specific address. This must currently be an IPv6 address;

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an IPv4 address can be specified using the

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<quote><literal>::FFFF:192.0.2.3</literal></quote> syntax.

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Also, if a link-local address is specified, an interface

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should be set, since a link-local address is only valid on

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a single interface. By default, the server will listen to

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all available addresses.

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Address to listen for requests on

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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PORT</replaceable></literal></term>

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<para>

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If this option is used, the server to bind to that

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port. By default, the server will listen to an arbitrary

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port given by the operating system.

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Port number to receive requests on

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--check</literal></term>

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<para>

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Run the server’s self-tests. This includes any unit

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tests, etc.

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Run self-test on the server

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--debug</literal></term>

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<para>

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If the server is run in debug mode, it will run in the

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foreground and print a lot of debugging information. The

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default is <emphasis>not</emphasis> to run in debug mode.

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Debug mode

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</para>

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</listitem>

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</varlistentry>

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PRIORITY</replaceable></literal></term>

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<para>

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GnuTLS priority string for the TLS handshake with the

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clients. The default is

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<quote><literal>SECURE256:!CTYPE-X.509:+CTYPE-OPENPGP</literal></quote>.

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See <citerefentry><refentrytitle>gnutls_priority_init

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</refentrytitle><manvolnum>3</manvolnum></citerefentry>

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for the syntax. <emphasis>Warning</emphasis>: changing

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this may make the TLS handshake fail, making communication

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with clients impossible.

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GnuTLS priority string. See <citerefentry>

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<refentrytitle>gnutls_priority_init</refentrytitle>

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--servicename <replaceable>NAME</replaceable>

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</literal></term>

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<para>

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Zeroconf service name. The default is

240

<quote><literal>Mandos</literal></quote>. You only need

241

to change this if you for some reason want to run more

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than one server on the same <emphasis>host</emphasis>,

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which would not normally be useful. If there are name

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collisions on the same <emphasis>network</emphasis>, the

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newer server will automatically rename itself to

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<quote><literal>Mandos #2</literal></quote>, and so on;

247

therefore, this option is not needed in that case.

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Zeroconf service name

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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<term><literal>--configdir <replaceable>DIR</replaceable>

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</literal></term>

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<para>

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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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<refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry>.

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Directory to search for configuration files

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</para>

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</listitem>

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</varlistentry>

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<term><literal>--version</literal></term>

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<para>

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Prints the program version and exit.

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Prints the program version

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</para>

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</listitem>

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</varlistentry>

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</varlistentry>

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</variablelist>

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</refsect1>

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<title>OVERVIEW</title>

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&OVERVIEW;

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<para>

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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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RAM disk environment.

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</para>

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</refsect1>

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<title>NETWORK PROTOCOL</title>

290

<para>

291

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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</para>

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<table>

307

<title>Mandos Protocol (Version 1)</title><tgroup cols="3"><thead>

308

<row>

309

<entry>Mandos Client</entry>

310

<entry>Direction</entry>

311

<entry>Mandos Server</entry>

312

</row>

313

</thead><tbody>

314

<row>

315

<entry>Connect</entry>

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</row>

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<row>

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</row>

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<row>

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<entry>TLS handshake <emphasis>as TLS <quote>server</quote>

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</emphasis></entry>

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<entry>TLS handshake <emphasis>as TLS <quote>client</quote>

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</emphasis></entry>

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</row>

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<row>

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<entry>OpenPGP public key (part of TLS handshake)</entry>

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</row>

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<row>

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<entry>Binary blob (client will assume OpenPGP data)</entry>

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</row>

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<row>

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<entry>Close</entry>

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</row>

343

</tbody></tgroup></table>

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</refsect1>

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<title>CHECKING</title>

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<para>

349

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.conf</refentrytitle>

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357

<refentrytitle>mandos-clients.conf</refentrytitle>

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<manvolnum>5</manvolnum></citerefentry>.

359

</para>

360

</refsect1>

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363

<title>LOGGING</title>

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<para>

365

The server will send log messaged with various severity levels

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to <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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</para>

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</refsect1>

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<title>EXIT STATUS</title>

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<para>

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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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</para>

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</refsect1>

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<title>ENVIRONMENT</title>

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<para>

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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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</citerefentry>

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</para>

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</listitem>

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</varlistentry>

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</variablelist>

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</refsect1>

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<title>FILES</title>

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<para>

403

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.

406

</para>

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<term><filename>/etc/mandos/mandos.conf</filename></term>

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<para>

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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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</para>

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</listitem>

417

</varlistentry>

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<term><filename>/etc/mandos/clients.conf</filename></term>

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<para>

422

List of clients and client-specific settings. See

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<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>

424

<manvolnum>5</manvolnum></citerefentry> for details.

425

</para>

426

</listitem>

427

</varlistentry>

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

430

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<para>

432

The file containing the process id of

433

<command>&COMMANDNAME;</command>.

434

</para>

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</listitem>

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</varlistentry>

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<para>

441

The Unix domain socket to where local syslog messages are

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sent.

443

</para>

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</listitem>

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</varlistentry>

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<para>

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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>

453

<manvolnum>5</manvolnum></citerefentry> for details.

454

</para>

455

</listitem>

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</varlistentry>

457

</variablelist>

222

</para>

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</refsect1>

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<title>NOTES</title>

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<para>

228

</para>

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</refsect1>

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<para>

463

This server might, on especially fatal errors, emit a Python

464

backtrace. This could be considered a feature.

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</para>

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<para>

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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"/>.

471

</para>

472

<para>

473

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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</para>

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<para>

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

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</para>

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<para>

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Debug mode is conflated with running in the foreground.

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</para>

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<para>

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The console log messages does not show a timestamp.

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</para>

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</refsect1>

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<title>EXAMPLE</title>

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<para>

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Normal invocation needs no options:

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</para>

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<para>

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<userinput>mandos</userinput>

496

</para>

497

</informalexample>

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<para>

500

Run the server in debug mode, read configuration files from

501

the <filename>~/mandos</filename> directory, and use the

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Zeroconf service name <quote>Test</quote> to not collide with

503

any other official Mandos server on this host:

504

</para>

505

<para>

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<userinput>mandos --debug --configdir ~/mandos --servicename Test</userinput>

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</para>

511

</informalexample>

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<para>

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Run the server normally, but only listen to one interface and

515

only on the link-local address on that interface:

516

</para>

517

<para>

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519

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<userinput>mandos --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>

521

522

</para>

523

</informalexample>

234

</para>

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</refsect1>

236

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<title>EXAMPLES</title>

239

<para>

240

</para>

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</refsect1>

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527

244

<title>SECURITY</title>

528

529

<title>SERVER</title>

530

<para>

531

Running this <command>&COMMANDNAME;</command> server program

532

should not in itself present any security risk to the host

533

computer running it. The program does not need any special

534

privileges to run, and is designed to run as a non-root user.

535

</para>

536

</refsect2>

537

538

<title>CLIENTS</title>

539

<para>

540

The server only gives out its stored data to clients which

541

does have the OpenPGP key of the stored fingerprint. This is

542

guaranteed by the fact that the client sends its OpenPGP

543

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

544

genuine. The server computes the fingerprint of the key

545

itself and looks up the fingerprint in its list of

546

clients. The <filename>clients.conf</filename> file (see

547

<citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>

548

<manvolnum>5</manvolnum></citerefentry>)

549

<emphasis>must</emphasis> be made non-readable by anyone

550

except the user running the server.

551

</para>

552

<para>

553

As detailed in <xref linkend="checking"/>, the status of all

554

client computers will continually be checked and be assumed

555

compromised if they are gone for too long.

556

</para>

557

<para>

558

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

559

by the server which would therefore declare the client

560

invalid. But if the server was ever restarted, it would

561

re-read its client list from its configuration file and again

562

regard all clients therein as valid, and hence eligible to

563

receive their passwords. Therefore, be careful when

564

restarting servers if you suspect that a client has, in fact,

565

been compromised by parties who may now be running a fake

566

Mandos client with the keys from the non-encrypted initial RAM

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

568

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

569

stop the server program, edit the configuration file to omit

570

any suspect clients, and restart the server program.

571

</para>

572

<para>

573

For more details on client-side security, see

574

<citerefentry><refentrytitle>password-request</refentrytitle>

575

<manvolnum>8mandos</manvolnum></citerefentry>.

576

</para>

577

</refsect2>

245

<para>

246

</para>

578

247

</refsect1>

579

248

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249

581

250

582

583

584

<term>

585

586

<refentrytitle>password-request</refentrytitle>

587

<manvolnum>8mandos</manvolnum>

588

</citerefentry>

589

</term>

590

591

<para>

592

This is the actual program which talks to this server.

593

Note that it is normally not invoked directly, and is only

594

run in the initial RAM disk environment, and not on a

595

fully started system.

596

</para>

597

</listitem>

598

</varlistentry>

599

600

<term>

601

<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>

602

</term>

603

604

<para>

605

Zeroconf is the network protocol standard used by clients

606

for finding this Mandos server on the local network.

607

</para>

608

</listitem>

609

</varlistentry>

610

611

<term>

612

<ulink url="http://www.avahi.org/">Avahi</ulink>

613

</term>

614

615

<para>

616

Avahi is the library this server calls to implement

617

Zeroconf service announcements.

618

</para>

619

</listitem>

620

</varlistentry>

621

622

<term>

623

<ulink

624

url="http://www.gnu.org/software/gnutls/">GnuTLS</ulink>

625

</term>

626

627

<para>

628

GnuTLS is the library this server uses to implement TLS for

629

communicating securely with the client, and at the same time

630

confidently get the client’s public OpenPGP key.

631

</para>

632

</listitem>

633

</varlistentry>

634

635

<term>

636

<citation>RFC 4291: <citetitle>IP Version 6 Addressing

637

Architecture</citetitle>, section 2.5.6, Link-Local IPv6

638

Unicast Addresses</citation>

639

</term>

640

641

<para>

642

The clients use IPv6 link-local addresses, which are

643

immediately usable since a link-local addresses is

644

automatically assigned to a network interfaces when it is

645

brought up.

646

</para>

647

</listitem>

648

</varlistentry>

649

650

<term>

651

<citation>RFC 4346: <citetitle>The Transport Layer Security

652

(TLS) Protocol Version 1.1</citetitle></citation>

653

</term>

654

655

<para>

656

TLS 1.1 is the protocol implemented by GnuTLS.

657

</para>

658

</listitem>

659

</varlistentry>

660

661

<term>

662

<citation>RFC 4880: <citetitle>OpenPGP Message

663

Format</citetitle></citation>

664

</term>

665

666

<para>

667

The data sent to clients is binary encrypted OpenPGP data.

668

</para>

669

</listitem>

670

</varlistentry>

671

672

<term>

673

<citation>RFC 5081: <citetitle>Using OpenPGP Keys for

674

Transport Layer Security</citetitle></citation>

675

</term>

676

677

<para>

678

This is implemented by GnuTLS and used by this server so

679

that OpenPGP keys can be used.

680

</para>

681

</listitem>

682

</varlistentry>

683

</variablelist>

251

<para>

252

<citerefentry><refentrytitle>plugin-runner</refentrytitle>

253

<manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>

254

<refentrytitle>password-request</refentrytitle>

255

<manvolnum>8mandos</manvolnum></citerefentry> and <citerefentry>

256

<refentrytitle>password-prompt</refentrytitle>

257

<manvolnum>8mandos</manvolnum></citerefentry>

258

</para>

684

259

</refsect1>

260

685

261

</refentry>

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