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3e98472223
Closes #34199. Signed-off-by: Christoph Anton Mitterer <mail@christoph.anton.mitterer.name>
147 lines
7.3 KiB
XML
147 lines
7.3 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
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<!ENTITY % entities SYSTEM "custom-entities.ent" >
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%entities;
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]>
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="systemd-ssh-generator"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>systemd-ssh-generator</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>systemd-ssh-generator</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-ssh-generator</refname>
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<refpurpose>Generator for binding a socket-activated SSH server to local <constant>AF_VSOCK</constant>
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and <constant>AF_UNIX</constant> sockets</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>/usr/lib/systemd/system-generators/systemd-ssh-generator</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><command>systemd-ssh-generator</command> binds a socket-activated SSH server to local
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<constant>AF_VSOCK</constant> and <constant>AF_UNIX</constant> sockets under certain conditions. It only
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has an effect if the <citerefentry
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project="man-pages"><refentrytitle>sshd</refentrytitle><manvolnum>8</manvolnum></citerefentry> binary is
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installed. Specifically, it does the following:</para>
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<itemizedlist>
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<listitem><para>If invoked in a VM with <constant>AF_VSOCK</constant> support, a socket-activated SSH
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per-connection service is bound to <constant>AF_VSOCK</constant> port 22.</para></listitem>
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<listitem><para>If invoked in a container environment with a writable directory
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<filename>/run/host/unix-export/</filename> pre-mounted it binds SSH to an <constant>AF_UNIX</constant>
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socket <filename>/run/host/unix-export/ssh</filename>. The assumption is that this directory is bind
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mounted to the host side as well, and can be used to connect to the container from there. See <ulink
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url="https://systemd.io/CONTAINER_INTERFACE">Container Interface</ulink> for more information about
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this interface.</para></listitem>
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<listitem><para>A local <constant>AF_UNIX</constant> socket
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<filename>/run/ssh-unix-local/socket</filename> is also bound, unconditionally. This may be used for
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SSH communication from the host to itself, without involving networking, for example to traverse
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security boundaries safely and with secure authentication.</para></listitem>
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<listitem><para>Additional <constant>AF_UNIX</constant> and <constant>AF_VSOCK</constant> sockets are
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optionally bound, based on the <varname>systemd.ssh_listen=</varname> kernel command line option or the
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<filename>ssh.listen</filename> system credential (see below).</para></listitem>
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</itemizedlist>
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<para>See
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<citerefentry><refentrytitle>systemd-ssh-proxy</refentrytitle><manvolnum>1</manvolnum></citerefentry> for
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details on how to connect to these sockets via the <command>ssh</command> client.</para>
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<para>The <varname>ssh.authorized_keys.root</varname> credential can be used to allow specific public keys
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to log in over SSH. See
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<citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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for more information.</para>
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<para>The generator will use a packaged <filename>sshd@.service</filename> service template file if one
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exists, and otherwise generate a suitable service template file.</para>
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<para><filename>systemd-ssh-generator</filename> implements
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<citerefentry><refentrytitle>systemd.generator</refentrytitle><manvolnum>7</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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<title>Kernel Command Line</title>
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<para><filename>systemd-ssh-generator</filename> understands the following
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<citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>
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parameters:</para>
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<variablelist class='kernel-commandline-options'>
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<varlistentry>
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<term><varname>systemd.ssh_auto=</varname></term>
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<listitem><para>This option takes an optional boolean argument, and defaults to yes. If enabled, the
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automatic binding to the <constant>AF_VSOCK</constant> and <constant>AF_UNIX</constant> sockets
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listed above is done. If disable, this is not done, except for those explicitly requested via
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<varname>systemd.ssh_listen=</varname> on the kernel command line or via the
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<varname>ssh.listen</varname> system credential.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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<varlistentry>
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<term><varname>systemd.ssh_listen=</varname></term>
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<listitem><para>This option configures an additional socket to bind SSH to. It may be used multiple
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times to bind multiple sockets. The syntax should follow the one of <varname>ListenStream=</varname>,
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see
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<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details. This functionality supports all socket families systemd supports, including
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<constant>AF_INET</constant> and <constant>AF_INET6</constant>.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Credentials</title>
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<para><command>systemd-ssh-generator</command> supports the system credentials logic. The following
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credentials are used when passed in:</para>
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<variablelist class='system-credentials'>
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<varlistentry>
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<term><varname>ssh.listen</varname></term>
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<listitem><para>This credential should be a text file, with each line referencing one additional
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socket to bind SSH to. The syntax should follow the one of <varname>ListenStream=</varname>, see
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<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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for details. This functionality supports all socket families systemd supports, including
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<constant>AF_INET</constant> and <constant>AF_INET6</constant>.</para>
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<xi:include href="version-info.xml" xpointer="v256"/></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>systemd.system-credentials</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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<member><citerefentry project="man-pages"><refentrytitle>vsock</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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<member><citerefentry project="man-pages"><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry></member>
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<member><citerefentry project="man-pages"><refentrytitle>ssh</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry project="man-pages"><refentrytitle>sshd</refentrytitle><manvolnum>8</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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