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- Committer: Teddy Hogeborn
- Date: 2024-11-17 16:53:00 UTC
- Revision ID: teddy@recompile.se-20241117165300-02hxm96s8cj9528e
mandos: Avoid closing configured server network socket
If we are passed a pre-created created network socket as a file
descriptor, we must avoid later closing it (when stdin, stdout and
stderr are dup2()ed over with /dev/null) by making sure that the
network file descriptor is not 0, 1, or 2, by creating a new file
descriptor if necessary.
However, when we create a new file descriptor we must check that the
new file descriptor is not 0, 1, or 2 either, and try again until we
get a suitable file descriptor.
If we are passed a pre-created created network socket as a file
descriptor, we must avoid later closing it (when stdin, stdout and
stderr are dup2()ed over with /dev/null) by making sure that the
network file descriptor is not 0, 1, or 2, by creating a new file
descriptor if necessary.
However, when we create a new file descriptor we must check that the
new file descriptor is not 0, 1, or 2 either, and try again until we
get a suitable file descriptor.
- files added:
- bugs.xml
- debian/tests
- debian/upstream
- dracut-module
- plugin-helpers
- files removed:
- initramfs-tools-hook-conf
- files modified:
- .bzrignore
added
removed
plugins.d/mandos-client.xml
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2
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY COMMANDNAME "mandos-client">
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<!ENTITY TIMESTAMP "2013-06-21">
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<!ENTITY TIMESTAMP "2023-10-21">
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<!ENTITY % common SYSTEM "../common.ent">
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%common;
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]>
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<copyright>
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<year>2008</year>
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<year>2009</year>
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<year>2010</year>
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<year>2011</year>
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<year>2012</year>
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<year>2013</year>
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<year>2014</year>
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<year>2015</year>
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<year>2016</year>
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<year>2017</year>
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<year>2018</year>
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<year>2019</year>
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<holder>Teddy Hogeborn</holder>
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<holder>Björn Påhlsson</holder>
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</copyright>
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<replaceable>FILE</replaceable></option></arg>
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</group>
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<sbr/>
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<group>
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<arg choice="plain"><option>--tls-privkey
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<replaceable>FILE</replaceable></option></arg>
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<arg choice="plain"><option>-t
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<replaceable>FILE</replaceable></option></arg>
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</group>
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<sbr/>
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<group>
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<arg choice="plain"><option>--tls-pubkey
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<replaceable>FILE</replaceable></option></arg>
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<arg choice="plain"><option>-T
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<replaceable>FILE</replaceable></option></arg>
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</group>
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<sbr/>
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<arg>
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<option>--priority <replaceable>STRING</replaceable></option>
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</arg>
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</arg>
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<sbr/>
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<arg>
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<option>--dh-params <replaceable>FILE</replaceable></option>
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</arg>
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<sbr/>
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<arg>
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<option>--delay <replaceable>SECONDS</replaceable></option>
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</arg>
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<sbr/>
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brings up network interfaces, uses the interfaces’ IPv6
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link-local addresses to get network connectivity, uses Zeroconf
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to find servers on the local network, and communicates with
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servers using TLS with an OpenPGP key to ensure authenticity and
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confidentiality. This client program keeps running, trying all
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servers on the network, until it receives a satisfactory reply
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or a TERM signal. After all servers have been tried, all
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servers using TLS with a raw public key to ensure authenticity
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and confidentiality. This client program keeps running, trying
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all servers on the network, until it receives a satisfactory
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reply or a TERM signal. After all servers have been tried, all
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servers are periodically retried. If no servers are found it
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will wait indefinitely for new servers to appear.
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</para>
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</para>
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<para>
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This program is not meant to be run directly; it is really meant
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to run as a plugin of the <application>Mandos</application>
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
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initial <acronym>RAM</acronym> disk environment because it is
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specified as a <quote>keyscript</quote> in the <citerefentry>
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<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry> file.
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to be run by other programs in the initial
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<acronym>RAM</acronym> disk environment; see <xref
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linkend="overview"/>.
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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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This program is commonly not invoked from the command line; it
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is normally started by the <application>Mandos</application>
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plugin runner, see <citerefentry><refentrytitle
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>plugin-runner</refentrytitle><manvolnum>8mandos</manvolnum>
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</citerefentry>. Any command line options this program accepts
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are therefore normally provided by the plugin runner, and not
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directly.
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is normally started by another program as described in <xref
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linkend="description"/>. Any command line options this program
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accepts are therefore normally provided by the invoking program,
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and not directly.
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</para>
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<variablelist>
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assumed to separate the address from the port number.
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</para>
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<para>
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This option is normally only useful for testing and
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debugging.
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Normally, Zeroconf would be used to locate Mandos servers,
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in which case this option would only be used when testing
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and debugging.
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</para>
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</listitem>
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</varlistentry>
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<para>
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<replaceable>NAME</replaceable> can be the string
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<quote><literal>none</literal></quote>; this will make
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<command>&COMMANDNAME;</command> not bring up
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<emphasis>any</emphasis> interfaces specified
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<emphasis>after</emphasis> this string. This is not
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recommended, and only meant for advanced users.
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<command>&COMMANDNAME;</command> only bring up interfaces
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specified <emphasis>before</emphasis> this string. This
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is not recommended, and only meant for advanced users.
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</para>
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</listitem>
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</varlistentry>
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</varlistentry>
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<varlistentry>
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<term><option>--tls-pubkey=<replaceable
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>FILE</replaceable></option></term>
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<term><option>-T
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<replaceable>FILE</replaceable></option></term>
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<listitem>
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<para>
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TLS raw public key file name. The default name is
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<quote><filename>/conf/conf.d/mandos/tls-pubkey.pem</filename
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></quote>.
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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><option>--tls-privkey=<replaceable
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>FILE</replaceable></option></term>
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<term><option>-t
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<replaceable>FILE</replaceable></option></term>
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<listitem>
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<para>
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TLS secret key file name. The default name is
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<quote><filename>/conf/conf.d/mandos/tls-privkey.pem</filename
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></quote>.
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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><option>--priority=<replaceable
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>STRING</replaceable></option></term>
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<listitem>
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<listitem>
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<para>
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Sets the number of bits to use for the prime number in the
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TLS Diffie-Hellman key exchange. Default is 1024.
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TLS Diffie-Hellman key exchange. The default value is
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selected automatically based on the GnuTLS security
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profile set in its priority string. Note that if the
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<option>--dh-params</option> option is used, the values
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from that file will be used instead.
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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><option>--dh-params=<replaceable
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>FILE</replaceable></option></term>
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<listitem>
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<para>
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Specifies a PEM-encoded PKCS#3 file to read the parameters
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needed by the TLS Diffie-Hellman key exchange from. If
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this option is not given, or if the file for some reason
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could not be used, the parameters will be generated on
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startup, which will take some time and processing power.
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Those using servers running under time, power or processor
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constraints may want to generate such a file in advance
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and use this option.
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</para>
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</listitem>
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</varlistentry>
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<title>OVERVIEW</title>
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<xi:include href="../overview.xml"/>
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<para>
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This program is the client part. It is a plugin started by
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry> which will run in
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an initial <acronym>RAM</acronym> disk environment.
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This program is the client part. It is run automatically in an
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initial <acronym>RAM</acronym> disk environment.
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</para>
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<para>
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In an initial <acronym>RAM</acronym> disk environment using
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<citerefentry><refentrytitle>systemd</refentrytitle>
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<manvolnum>1</manvolnum></citerefentry>, this program is started
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by the <application>Mandos</application> <citerefentry>
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<refentrytitle>password-agent</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>, which in turn is
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started automatically by the <citerefentry>
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<refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry> <quote>Password Agent</quote> system.
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</para>
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<para>
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In the case of a non-<citerefentry>
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<refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum>
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</citerefentry> environment, this program is started as a plugin
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of the <application>Mandos</application> <citerefentry>
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<refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>, which runs in the
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initial <acronym>RAM</acronym> disk environment because it is
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specified as a <quote>keyscript</quote> in the <citerefentry>
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<refentrytitle>crypttab</refentrytitle><manvolnum>5</manvolnum>
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</citerefentry> file.
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</para>
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<para>
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This program could, theoretically, be used as a keyscript in
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<filename>/etc/crypttab</filename>, but it would then be
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impossible to enter a password for the encrypted root disk at
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the console, since this program does not read from the console
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at all. This is why a separate plugin runner (<citerefentry>
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<refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) is used to run
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both this program and others in in parallel,
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<emphasis>one</emphasis> of which (<citerefentry>
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<refentrytitle>password-prompt</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>) will prompt for
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passwords on the system console.
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at all.
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</para>
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</refsect1>
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<refsect1 id="environment">
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<title>ENVIRONMENT</title>
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<variablelist>
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<varlistentry>
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<term><envar>MANDOSPLUGINHELPERDIR</envar></term>
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<listitem>
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<para>
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This environment variable will be assumed to contain the
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directory containing any helper executables. The use and
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nature of these helper executables, if any, is purposely
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not documented.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>
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This program does not use any environment variables, not even
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the ones provided by <citerefentry><refentrytitle
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This program does not use any other environment variables, not
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even the ones provided by <citerefentry><refentrytitle
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>cryptsetup</refentrytitle><manvolnum>8</manvolnum>
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</citerefentry>.
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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><filename>/conf/conf.d/mandos/tls-pubkey.pem</filename
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></term>
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<term><filename>/conf/conf.d/mandos/tls-privkey.pem</filename
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></term>
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<listitem>
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<para>
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Public and private raw key files, in <quote>PEM</quote>
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format. These are the default file names, they can be
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changed with the <option>--tls-pubkey</option> and
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<option>--tls-privkey</option> options.
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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><filename
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class="directory">/lib/mandos/network-hooks.d</filename></term>
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<listitem>
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</variablelist>
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</refsect1>
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<!-- <refsect1 id="bugs"> -->
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<!-- <title>BUGS</title> -->
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<!-- <para> -->
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<!-- </para> -->
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<!-- </refsect1> -->
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<refsect1 id="bugs">
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<title>BUGS</title>
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<xi:include href="../bugs.xml"/>
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</refsect1>
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<refsect1 id="example">
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<title>EXAMPLE</title>
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<para>
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Note that normally, command line options will not be given
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directly, but via options for the Mandos <citerefentry
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><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>.
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directly, but passed on via the program responsible for starting
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this program; see <xref linkend="overview"/>.
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</para>
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<informalexample>
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<para>
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</informalexample>
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<informalexample>
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<para>
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Run in debug mode, and use a custom key:
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Run in debug mode, and use custom keys:
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</para>
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<para>
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt</userinput>
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --tls-pubkey keydir/tls-pubkey.pem --tls-privkey keydir/tls-privkey.pem</userinput>
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</para>
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</informalexample>
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<informalexample>
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<para>
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Run in debug mode, with a custom key, and do not use Zeroconf
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Run in debug mode, with custom keys, and do not use Zeroconf
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to locate a server; connect directly to the IPv6 link-local
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address <quote><systemitem class="ipaddress"
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>fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
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<para>
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<!-- do not wrap this line -->
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
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<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --tls-pubkey keydir/tls-pubkey.pem --tls-privkey keydir/tls-privkey.pem --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
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</para>
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</informalexample>
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<refsect1 id="security">
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<title>SECURITY</title>
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<para>
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This program is set-uid to root, but will switch back to the
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original (and presumably non-privileged) user and group after
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bringing up the network interface.
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This program assumes that it is set-uid to root, and will switch
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back to the original (and presumably non-privileged) user and
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group after bringing up the network interface.
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</para>
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<para>
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To use this program for its intended purpose (see <xref
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<para>
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The only remaining weak point is that someone with physical
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access to the client hard drive might turn off the client
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computer, read the OpenPGP keys directly from the hard drive,
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and communicate with the server. To safeguard against this, the
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server is supposed to notice the client disappearing and stop
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giving out the encrypted data. Therefore, it is important to
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set the timeout and checker interval values tightly on the
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server. See <citerefentry><refentrytitle
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computer, read the OpenPGP and TLS keys directly from the hard
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drive, and communicate with the server. To safeguard against
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this, the server is supposed to notice the client disappearing
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and stop giving out the encrypted data. Therefore, it is
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important to set the timeout and checker interval values tightly
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on the server. See <citerefentry><refentrytitle
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>mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
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</para>
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<para>
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It will also help if the checker program on the server is
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configured to request something from the client which can not be
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spoofed by someone else on the network, unlike unencrypted
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<acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
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spoofed by someone else on the network, like SSH server key
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fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
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echo (<quote>ping</quote>) replies.
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</para>
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<para>
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<emphasis>Note</emphasis>: This makes it completely insecure to
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<manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>mandos</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>password-prompt</refentrytitle>
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<citerefentry><refentrytitle>password-agent</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>plugin-runner</refentrytitle>
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<manvolnum>8mandos</manvolnum></citerefentry>
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</varlistentry>
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<varlistentry>
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<term>
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<ulink url="http://www.avahi.org/">Avahi</ulink>
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<ulink url="https://www.avahi.org/">Avahi</ulink>
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</term>
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<listitem>
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<para>
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</varlistentry>
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<varlistentry>
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<term>
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<ulink url="http://www.gnu.org/software/gnutls/"
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>GnuTLS</ulink>
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<ulink url="https://www.gnutls.org/">GnuTLS</ulink>
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</term>
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<listitem>
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<para>
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GnuTLS is the library this client uses to implement TLS for
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communicating securely with the server, and at the same time
809
send the public OpenPGP key to the server.
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send the public key to 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>
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<ulink url="http://www.gnupg.org/related_software/gpgme/"
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<ulink url="https://www.gnupg.org/related_software/gpgme/"
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>GPGME</ulink>
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</term>
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<listitem>
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</varlistentry>
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<varlistentry>
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<term>
859
RFC 4346: <citetitle>The Transport Layer Security (TLS)
860
Protocol Version 1.1</citetitle>
968
RFC 5246: <citetitle>The Transport Layer Security (TLS)
969
Protocol Version 1.2</citetitle>
861
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</term>
862
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<listitem>
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<para>
864
TLS 1.1 is the protocol implemented by GnuTLS.
973
TLS 1.2 is the protocol implemented by GnuTLS.
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</para>
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</listitem>
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</varlistentry>
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</varlistentry>
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<varlistentry>
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<term>
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RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
990
RFC 7250: <citetitle>Using Raw Public Keys in Transport
991
Layer Security (TLS) and Datagram Transport Layer Security
992
(DTLS)</citetitle>
993
</term>
994
<listitem>
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<para>
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This is implemented by GnuTLS in version 3.6.6 and is, if
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present, used by this program so that raw public keys can be
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used.
999
</para>
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</listitem>
1001
</varlistentry>
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<varlistentry>
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<term>
1004
RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
882
1005
Security</citetitle>
883
1006
</term>
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<listitem>
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<para>
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This is implemented by GnuTLS and used by this program so
887
that OpenPGP keys can be used.
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This is implemented by GnuTLS before version 3.6.0 and is,
1010
if present, used by this program so that OpenPGP keys can be
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used.
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</para>
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</listitem>
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</varlistentry>
Loggerhead is a web-based interface for Breezy
Version: 2.0.2.dev0