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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-client">
<!ENTITY TIMESTAMP "2009-01-24">
<!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@fukt.bsnet.se</email>
</address>
</author>
<author>
<firstname>Teddy</firstname>
<surname>Hogeborn</surname>
<address>
<email>teddy@fukt.bsnet.se</email>
</address>
</author>
</authorgroup>
<copyright>
<year>2008</year>
<year>2009</year>
<holder>Teddy Hogeborn</holder>
<holder>Björn Påhlsson</holder>
</copyright>
<xi:include href="../legalnotice.xml"/>
</refentryinfo>
<refmeta>
<refentrytitle>&COMMANDNAME;</refentrytitle>
<manvolnum>8mandos</manvolnum>
</refmeta>
<refnamediv>
<refname><command>&COMMANDNAME;</command></refname>
<refpurpose>
Client for <application>Mandos</application>
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>&COMMANDNAME;</command>
<group>
<arg choice="plain"><option>--connect
<replaceable>ADDRESS</replaceable><literal>:</literal
><replaceable>PORT</replaceable></option></arg>
<arg choice="plain"><option>-c
<replaceable>ADDRESS</replaceable><literal>:</literal
><replaceable>PORT</replaceable></option></arg>
</group>
<sbr/>
<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>--pubkey
<replaceable>FILE</replaceable></option></arg>
<arg choice="plain"><option>-p
<replaceable>FILE</replaceable></option></arg>
</group>
<sbr/>
<group>
<arg choice="plain"><option>--seckey
<replaceable>FILE</replaceable></option></arg>
<arg choice="plain"><option>-s
<replaceable>FILE</replaceable></option></arg>
</group>
<sbr/>
<arg>
<option>--priority <replaceable>STRING</replaceable></option>
</arg>
<sbr/>
<arg>
<option>--dh-bits <replaceable>BITS</replaceable></option>
</arg>
<sbr/>
<arg>
<option>--debug</option>
</arg>
</cmdsynopsis>
<cmdsynopsis>
<command>&COMMANDNAME;</command>
<group choice="req">
<arg choice="plain"><option>--help</option></arg>
<arg choice="plain"><option>-?</option></arg>
</group>
</cmdsynopsis>
<cmdsynopsis>
<command>&COMMANDNAME;</command>
<arg choice="plain"><option>--usage</option></arg>
</cmdsynopsis>
<cmdsynopsis>
<command>&COMMANDNAME;</command>
<group choice="req">
<arg choice="plain"><option>--version</option></arg>
<arg choice="plain"><option>-V</option></arg>
</group>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id="description">
<title>DESCRIPTION</title>
<para>
<command>&COMMANDNAME;</command> is a client program that
communicates with <citerefentry><refentrytitle
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
to get a password. It brings up a network interface, uses its
IPv6 link-local address to get network connectivity, uses
Zeroconf to find servers, and uses TLS with an OpenPGP key to
ensure authenticity and confidentiality. It keeps running,
trying all servers on the network, until it receives a
satisfactory reply or a TERM signal is received.
</para>
<para>
This program is not meant to be run directly; it is really meant
to run as a plugin of the <application>Mandos</application>
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
initial <acronym>RAM</acronym> disk environment because it is
specified as a <quote>keyscript</quote> in the <citerefentry>
<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
</citerefentry> file.
</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>
<para>
This program is commonly not invoked from the command line; it
is normally started by the <application>Mandos</application>
plugin runner, see <citerefentry><refentrytitle
>plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
</citerefentry>. Any command line options this program accepts
are therefore normally provided by the plugin runner, and not
directly.
</para>
<variablelist>
<varlistentry>
<term><option>--connect=<replaceable
>ADDRESS</replaceable><literal>:</literal><replaceable
>PORT</replaceable></option></term>
<term><option>-c
<replaceable>ADDRESS</replaceable><literal>:</literal
><replaceable>PORT</replaceable></option></term>
<listitem>
<para>
Do not use Zeroconf to locate servers. Connect directly
to only one specified <application>Mandos</application>
server. Note that an IPv6 address has colon characters in
it, so the <emphasis>last</emphasis> colon character is
assumed to separate the address from the port number.
</para>
<para>
This option is normally only useful for testing and
debugging.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--interface=
<replaceable>NAME</replaceable></option></term>
<term><option>-i
<replaceable>NAME</replaceable></option></term>
<listitem>
<para>
Network interface that will be brought up and scanned for
Mandos servers to connect to. The default it
<quote><literal>eth0</literal></quote>.
</para>
<para>
If the <option>--connect</option> option is used, this
specifies the interface to use to connect to the address
given.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--pubkey=<replaceable
>FILE</replaceable></option></term>
<term><option>-p
<replaceable>FILE</replaceable></option></term>
<listitem>
<para>
OpenPGP public key file name. The default name is
<quote><filename>/conf/conf.d/mandos/pubkey.txt</filename
></quote>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--seckey=<replaceable
>FILE</replaceable></option></term>
<term><option>-s
<replaceable>FILE</replaceable></option></term>
<listitem>
<para>
OpenPGP secret key file name. The default name is
<quote><filename>/conf/conf.d/mandos/seckey.txt</filename
></quote>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--priority=<replaceable
>STRING</replaceable></option></term>
<listitem>
<xi:include href="../mandos-options.xml"
xpointer="priority"/>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--dh-bits=<replaceable
>BITS</replaceable></option></term>
<listitem>
<para>
Sets the number of bits to use for the prime number in the
TLS Diffie-Hellman key exchange. Default is 1024.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--debug</option></term>
<listitem>
<para>
Enable debug mode. This will enable a lot of output to
standard error about what the program is doing. The
program will still perform all other functions normally.
</para>
<para>
It will also enable debug mode in the Avahi and GnuTLS
libraries, making them print large amounts of debugging
output.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--help</option></term>
<term><option>-?</option></term>
<listitem>
<para>
Gives a help message about options and their meanings.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--usage</option></term>
<listitem>
<para>
Gives a short usage message.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>--version</option></term>
<term><option>-V</option></term>
<listitem>
<para>
Prints the program version.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="overview">
<title>OVERVIEW</title>
<xi:include href="../overview.xml"/>
<para>
This program is the client part. It is a plugin started by
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
<manvolnum>8mandos</manvolnum></citerefentry> which will run in
an initial <acronym>RAM</acronym> disk environment.
</para>
<para>
This program could, theoretically, be used as a keyscript in
<filename>/etc/crypttab</filename>, but it would then be
impossible to enter a password for the encrypted root disk at
the console, since this program does not read from the console
at all. This is why a separate plugin runner (<citerefentry>
<refentrytitle>plugin-runner</refentrytitle>
<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
both this program and others in in parallel,
<emphasis>one</emphasis> of which will prompt for passwords on
the system console.
</para>
</refsect1>
<refsect1 id="exit_status">
<title>EXIT STATUS</title>
<para>
This program will exit with a successful (zero) exit status if a
server could be found and the password received from it could be
successfully decrypted and output on standard output. The
program will exit with a non-zero exit status only if a critical
error occurs. Otherwise, it will forever connect to new
<application>Mandos</application> servers as they appear, trying
to get a decryptable password and print it.
</para>
</refsect1>
<refsect1 id="environment">
<title>ENVIRONMENT</title>
<para>
This program does not use any environment variables, not even
the ones provided by <citerefentry><refentrytitle
>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>.
</para>
</refsect1>
<refsect1 id="files">
<title>FILES</title>
<variablelist>
<varlistentry>
<term><filename>/conf/conf.d/mandos/pubkey.txt</filename
></term>
<term><filename>/conf/conf.d/mandos/seckey.txt</filename
></term>
<listitem>
<para>
OpenPGP public and private key files, in <quote>ASCII
Armor</quote> format. These are the default file names,
they can be changed with the <option>--pubkey</option> and
<option>--seckey</option> options.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<!-- <refsect1 id="bugs"> -->
<!-- <title>BUGS</title> -->
<!-- <para> -->
<!-- </para> -->
<!-- </refsect1> -->
<refsect1 id="example">
<title>EXAMPLE</title>
<para>
Note that normally, command line options will not be given
directly, but via options for the Mandos <citerefentry
><refentrytitle>plugin-runner</refentrytitle>
<manvolnum>8mandos</manvolnum></citerefentry>.
</para>
<informalexample>
<para>
Normal invocation needs no options, if the network interface
is <quote>eth0</quote>:
</para>
<para>
<userinput>&COMMANDNAME;</userinput>
</para>
</informalexample>
<informalexample>
<para>
Search for Mandos servers (and connect to them) using another
interface:
</para>
<para>
<!-- do not wrap this line -->
<userinput>&COMMANDNAME; --interface eth1</userinput>
</para>
</informalexample>
<informalexample>
<para>
Run in debug mode, and use a custom key:
</para>
<para>
<!-- do not wrap this line -->
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
</para>
</informalexample>
<informalexample>
<para>
Run in debug mode, with a custom key, and do not use Zeroconf
to locate a server; connect directly to the IPv6 address
<quote><systemitem class="ipaddress"
>2001:db8:f983:bd0b:30de:ae4a:71f2:f672</systemitem></quote>,
port 4711, using interface eth2:
</para>
<para>
<!-- do not wrap this line -->
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>
</para>
</informalexample>
</refsect1>
<refsect1 id="security">
<title>SECURITY</title>
<para>
This program is set-uid to root, but will switch back to the
original (and presumably non-privileged) user and group after
bringing up the network interface.
</para>
<para>
To use this program for its intended purpose (see <xref
linkend="purpose"/>), the password for the root file system will
have to be given out to be stored in a server computer, after
having been encrypted using an OpenPGP key. This encrypted data
which will be stored in a server can only be decrypted by the
OpenPGP key, and the data will only be given out to those
clients who can prove they actually have that key. This key,
however, is stored unencrypted on the client side in its initial
<acronym>RAM</acronym> disk image file system. This is normally
readable by all, but this is normally fixed during installation
of this program; file permissions are set so that no-one is able
to read that file.
</para>
<para>
The only remaining weak point is that someone with physical
access to the client hard drive might turn off the client
computer, read the OpenPGP keys directly from the hard drive,
and communicate with the server. To safeguard against this, the
server is supposed to notice the client disappearing and stop
giving out the encrypted data. Therefore, it is important to
set the timeout and checker interval values tightly on the
server. See <citerefentry><refentrytitle
>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
</para>
<para>
It will also help if the checker program on the server is
configured to request something from the client which can not be
spoofed by someone else on the network, unlike unencrypted
<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
</para>
<para>
<emphasis>Note</emphasis>: This makes it completely insecure to
have <application >Mandos</application> clients which dual-boot
to another operating system which is <emphasis>not</emphasis>
trusted to keep the initial <acronym>RAM</acronym> disk image
confidential.
</para>
</refsect1>
<refsect1 id="see_also">
<title>SEE ALSO</title>
<para>
<citerefentry><refentrytitle>cryptsetup</refentrytitle>
<manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>crypttab</refentrytitle>
<manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>mandos</refentrytitle>
<manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>password-prompt</refentrytitle>
<manvolnum>8mandos</manvolnum></citerefentry>,
<citerefentry><refentrytitle>plugin-runner</refentrytitle>
<manvolnum>8mandos</manvolnum></citerefentry>
</para>
<variablelist>
<varlistentry>
<term>
<ulink url="http://www.zeroconf.org/">Zeroconf</ulink>
</term>
<listitem>
<para>
Zeroconf is the network protocol standard used for finding
Mandos servers 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 program calls to find Zeroconf
services.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<ulink url="http://www.gnu.org/software/gnutls/"
>GnuTLS</ulink>
</term>
<listitem>
<para>
GnuTLS is the library this client uses to implement TLS for
communicating securely with the server, and at the same time
send the public OpenPGP key to the server.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
<ulink url="http://www.gnupg.org/related_software/gpgme/"
>GPGME</ulink>
</term>
<listitem>
<para>
GPGME is the library used to decrypt the OpenPGP data sent
by the server.
</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>
This client uses 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 4346: <citetitle>The Transport Layer Security (TLS)
Protocol Version 1.1</citetitle>
</term>
<listitem>
<para>
TLS 1.1 is the protocol implemented by GnuTLS.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
RFC 4880: <citetitle>OpenPGP Message Format</citetitle>
</term>
<listitem>
<para>
The data received from the server is binary encrypted
OpenPGP data.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>
RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
Security</citetitle>
</term>
<listitem>
<para>
This is implemented by GnuTLS and used by this program so
that OpenPGP keys can be used.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
<!-- Local Variables: -->
<!-- time-stamp-start: "<!ENTITY TIMESTAMP [\"']" -->
<!-- time-stamp-end: "[\"']>" -->
<!-- time-stamp-format: "%:y-%02m-%02d" -->
<!-- End: -->
|