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Committer: Teddy Hogeborn
Date: 2008-09-03 17:34:29 UTC
Revision ID: teddy@fukt.bsnet.se-20080903173429-db2mjtddf7mgbx8z

* plugins.d/password-request.xml (OVERVIEW): Refer to
                                             password-prompt(8) by
                                             name.
  (SECURITY): Improved wording.  Add paragraph about insecurity of
              ping.
  (SEE ALSO): Add references to cryptsetup(8) and crypttab(5).
              Changed to be a <variablelist> and added text.

files added:
.bzrignore

COPYING

initramfs-tools-hook

initramfs-tools-hook-conf

initramfs-tools-script

legalnotice.xml

mandos-clients.conf.xml

mandos-keygen

mandos-keygen.xml

mandos-options.xml

mandos.conf

mandos.conf.xml

mandos.xml

overview.xml

plugin-runner.xml

plugins.d/password-prompt.xml

plugins.d/password-request.xml

plugins.d/usplash

files removed:
ca.pem

cert.pem

client-cert.pem

client-key.pem

crl.pem

key.pem

files renamed:
mandos-clients.conf => clients.conf

server.py => mandos

plugbasedclient.c => plugin-runner.c

plugins.d/passprompt.c => plugins.d/password-prompt.c

plugins.d/mandosclient.c => plugins.d/password-request.c

files modified:
Makefile

TODO

Show diffs side-by-side

added added

removed removed

mandos.xml

<?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 VERSION "1.0">

<!ENTITY COMMANDNAME "mandos">

<!ENTITY TIMESTAMP "2008-09-02">

<title>Mandos Manual</title>

<productname>Mandos</productname>

<productnumber>&VERSION;</productnumber>

<date>&TIMESTAMP;</date>

<firstname>Björn</firstname>

<surname>Påhlsson</surname>

<email>belorn@fukt.bsnet.se</email>

</address>

</author>

<firstname>Teddy</firstname>

<surname>Hogeborn</surname>

<email>teddy@fukt.bsnet.se</email>

</address>

</author>

</authorgroup>

<holder>Teddy Hogeborn</holder>

<holder>Björn Påhlsson</holder>

</copyright>

<xi:include href="legalnotice.xml"/>

</refentryinfo>

<refentrytitle>&COMMANDNAME;</refentrytitle>

</refmeta>

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

Gives encrypted passwords to authenticated Mandos clients

</refpurpose>

</refnamediv>

<command>&COMMANDNAME;</command>

<group>

<arg choice="plain"><option>--interface

<arg choice="plain"><option>-i

</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

<arg choice="plain"><option>-p

</group>

<sbr/>

<arg><option>--priority

<replaceable>PRIORITY</replaceable></option></arg>

<sbr/>

<arg><option>--servicename

<sbr/>

<arg><option>--configdir

<replaceable>DIRECTORY</replaceable></option></arg>

<sbr/>

<arg><option>--debug</option></arg>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

</group>

</cmdsynopsis>

<command>&COMMANDNAME;</command>

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

</cmdsynopsis>

<command>&COMMANDNAME;</command>

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

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</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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<title>OPTIONS</title>

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<para>

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Show a help message and exit

139

</para>

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</listitem>

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</varlistentry>

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<term><option>--interface</option>

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<xi:include href="mandos-options.xml" xpointer="interface"/>

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</listitem>

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</varlistentry>

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<term><option>--address

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<replaceable>ADDRESS</replaceable></option></term>

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<term><option>-a

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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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</listitem>

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</varlistentry>

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<term><option>--port

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<term><option>-p

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<xi:include href="mandos-options.xml" xpointer="port"/>

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</listitem>

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</varlistentry>

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<term><option>--check</option></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.

179

</para>

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</listitem>

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</varlistentry>

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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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</listitem>

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</varlistentry>

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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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</listitem>

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</varlistentry>

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<term><option>--servicename

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<xi:include href="mandos-options.xml"

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xpointer="servicename"/>

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</listitem>

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</varlistentry>

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<term><option>--configdir

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<replaceable>DIRECTORY</replaceable></option></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>.

218

</para>

219

</listitem>

220

</varlistentry>

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<term><option>--version</option></term>

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<para>

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Prints the program version and exit.

227

</para>

228

</listitem>

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</varlistentry>

230

</variablelist>

231

</refsect1>

232

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<title>OVERVIEW</title>

235

<xi:include href="overview.xml"/>

236

<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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<acronym>RAM</acronym> disk environment.

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</para>

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</refsect1>

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<title>NETWORK PROTOCOL</title>

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<para>

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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>.

255

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.

260

</para>

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<table>

262

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

263

<row>

264

<entry>Mandos Client</entry>

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<entry>Direction</entry>

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<entry>Mandos Server</entry>

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</row>

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</thead><tbody>

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<row>

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<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>

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

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</refsect1>

300

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<title>CHECKING</title>

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<para>

304

The server will, by default, continually check that the clients

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are still up. If a client has not been confirmed as being up

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for some time, the client is assumed to be compromised and is no

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longer eligible to receive the encrypted password. The timeout,

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checker program, and interval between checks can be configured

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both globally and per client; see <citerefentry>

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

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

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</para>

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</refsect1>

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<title>LOGGING</title>

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<para>

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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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</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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354

<title>FILES</title>

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<para>

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Use the <option>--configdir</option> option to change where

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<command>&COMMANDNAME;</command> looks for its configurations

358

files. The default file names are listed here.

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</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>

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</varlistentry>

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

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<para>

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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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</para>

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</listitem>

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</varlistentry>

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

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<para>

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The file containing the process id of

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<command>&COMMANDNAME;</command>.

387

</para>

388

</listitem>

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</varlistentry>

390

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<para>

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The Unix domain socket to where local syslog messages are

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sent.

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</para>

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</listitem>

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</varlistentry>

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<para>

403

This is used to start the configured checker command for

404

each client. See <citerefentry>

405

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

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

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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>

412

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414

415

<para>

416

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

417

backtrace. This could be considered a feature.

418

</para>

419

<para>

420

Currently, if a client is declared <quote>invalid</quote> due to

421

having timed out, the server does not record this fact onto

422

permanent storage. This has some security implications, see

423

<xref linkend="CLIENTS"/>.

424

</para>

425

<para>

426

There is currently no way of querying the server of the current

427

status of clients, other than analyzing its <systemitem

428

class="service">syslog</systemitem> output.

429

</para>

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<para>

431

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

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</para>

433

<para>

434

Debug mode is conflated with running in the foreground.

435

</para>

436

<para>

437

The console log messages does not show a timestamp.

438

</para>

439

</refsect1>

440

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<title>EXAMPLE</title>

443

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<para>

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Normal invocation needs no options:

446

</para>

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<para>

448

<userinput>&COMMANDNAME;</userinput>

449

</para>

450

</informalexample>

451

452

<para>

453

Run the server in debug mode, read configuration files from

454

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

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

456

any other official Mandos server on this host:

457

</para>

458

<para>

459

460

461

<userinput>&COMMANDNAME; --debug --configdir ~/mandos --servicename Test</userinput>

462

463

</para>

464

</informalexample>

465

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<para>

467

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

468

only on the link-local address on that interface:

469

</para>

470

<para>

471

472

473

<userinput>&COMMANDNAME; --interface eth7 --address fe80::aede:48ff:fe71:f6f2</userinput>

474

475

</para>

476

</informalexample>

477

</refsect1>

478

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480

<title>SECURITY</title>

481

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<title>SERVER</title>

483

<para>

484

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

485

should not in itself present any security risk to the host

486

computer running it. The program does not need any special

487

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

488

</para>

489

</refsect2>

490

491

<title>CLIENTS</title>

492

<para>

493

The server only gives out its stored data to clients which

494

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

495

guaranteed by the fact that the client sends its OpenPGP

496

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

497

genuine. The server computes the fingerprint of the key

498

itself and looks up the fingerprint in its list of

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

500

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

501

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

502

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

503

except the user running the server.

504

</para>

505

<para>

506

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

507

client computers will continually be checked and be assumed

508

compromised if they are gone for too long.

509

</para>

510

<para>

511

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

512

by the server which would therefore declare the client

513

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

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

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regard all clients therein as valid, and hence eligible to

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receive their passwords. Therefore, be careful when

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restarting servers if it is suspected that a client has, in

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fact, been compromised by parties who may now be running a

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fake Mandos client with the keys from the non-encrypted

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initial <acronym>RAM</acronym> image of the client host. What

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should be done in that case (if restarting the server program

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really is necessary) is to stop the server program, edit the

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configuration file to omit any suspect clients, and restart

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the server program.

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</para>

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<para>

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For more details on client-side security, see

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

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

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</para>

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</refsect2>

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</refsect1>

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<para>

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

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<refentrytitle>mandos.conf</refentrytitle>

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<refentrytitle>password-request</refentrytitle>

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

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</citerefentry>

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</para>

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<term>

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

551

</term>

552

553

<para>

554

Zeroconf is the network protocol standard used by clients

555

for finding this Mandos server on the local network.

556

</para>

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</listitem>

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</varlistentry>

559

560

<term>

561

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

562

</term>

563

564

<para>

565

Avahi is the library this server calls to implement

566

Zeroconf service announcements.

567

</para>

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</listitem>

569

</varlistentry>

570

571

<term>

572

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

573

>GnuTLS</ulink>

574

</term>

575

576

<para>

577

GnuTLS is the library this server uses to implement TLS for

578

communicating securely with the client, and at the same time

579

confidently get the client’s public OpenPGP key.

580

</para>

581

</listitem>

582

</varlistentry>

583

584

<term>

585

RFC 4291: <citetitle>IP Version 6 Addressing

586

Architecture</citetitle>

587

</term>

588

589

590

591

<term>Section 2.2: <citetitle>Text Representation of

592

Addresses</citetitle></term>

593

594

</varlistentry>

595

596

<term>Section 2.5.5.2: <citetitle>IPv4-Mapped IPv6

597

Address</citetitle></term>

598

599

</varlistentry>

600

601

<term>Section 2.5.6, <citetitle>Link-Local IPv6 Unicast

602

Addresses</citetitle></term>

603

604

<para>

605

The clients use IPv6 link-local addresses, which are

606

immediately usable since a link-local addresses is

607

automatically assigned to a network interfaces when it

608

is brought up.

609

</para>

610

</listitem>

611

</varlistentry>

612

</variablelist>

613

</listitem>

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</varlistentry>

615

616

<term>

617

RFC 4346: <citetitle>The Transport Layer Security (TLS)

618

Protocol Version 1.1</citetitle>

619

</term>

620

621

<para>

622

TLS 1.1 is the protocol implemented by GnuTLS.

623

</para>

624

</listitem>

625

</varlistentry>

626

627

<term>

628

RFC 4880: <citetitle>OpenPGP Message Format</citetitle>

629

</term>

630

631

<para>

632

The data sent to clients is binary encrypted OpenPGP data.

633

</para>

634

</listitem>

635

</varlistentry>

636

637

<term>

638

RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer

639

Security</citetitle>

640

</term>

641

642

<para>

643

This is implemented by GnuTLS and used by this server so

644

that OpenPGP keys can be used.

645

</para>

646

</listitem>

647

</varlistentry>

648

</variablelist>

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</refsect1>

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</refentry>

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