shorewall_code/docs/CompiledPrograms.xml

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  <!--$Id$-->

  <articleinfo>
    <title>Compiled Firewall Programs and Shorewall Lite</title>

    <authorgroup>
      <author>
        <firstname>Tom</firstname>

        <surname>Eastep</surname>
      </author>
    </authorgroup>

    <pubdate><?dbtimestamp format="Y/m/d"?></pubdate>

    <copyright>
      <year>2006-2007</year>

      <holder>Thomas M. Eastep</holder>
    </copyright>

    <legalnotice>
      <para>Permission is granted to copy, distribute and/or modify this
      document under the terms of the GNU Free Documentation License, Version
      1.2 or any later version published by the Free Software Foundation; with
      no Invariant Sections, with no Front-Cover, and with no Back-Cover
      Texts. A copy of the license is included in the section entitled
      <quote><ulink url="GnuCopyright.htm">GNU Free Documentation
      License</ulink></quote>.</para>
    </legalnotice>
  </articleinfo>

  <caution>
    <para><emphasis role="bold">This article applies to Shorewall 4.3 and
    later. If you are running a version of Shorewall earlier than Shorewall
    4.3.5 then please see the documentation appropriate for your
    version.</emphasis></para>
  </caution>

  <section id="Overview">
    <title>Overview</title>

    <para>Shorewall has the capability to compile a Shorewall configuration
    and produce a runnable firewall program script. The script is a complete
    program which can be placed on a system with <emphasis>Shorewall
    Lite</emphasis> installed and can serve as the firewall creation script
    for that system.</para>

    <section id="Restrictions">
      <title>Restrictions</title>

      <para>While compiled Shorewall programs are useful in many cases, there
      are some important restrictions that you should be aware of before
      attempting to use them.</para>

      <orderedlist>
        <listitem>
          <para>The <emphasis role="bold">detectnets</emphasis> interface
          option is not supported.</para>
        </listitem>

        <listitem>
          <para>All extension scripts used are copied into the program (with
          the exception of <ulink url="shorewall_extension_scripts.htm">those
          executed at compile-time by the compiler</ulink>). The ramifications
          of this are:</para>

          <itemizedlist>
            <listitem>
              <para>If you update an extension script, the compiled program
              will not use the updated script.</para>
            </listitem>

            <listitem>
              <para>The <filename>params</filename> file is only processed at
              compile time if you set EXPORTPARAMS=No in
              <filename>shorewall.conf</filename>. For run-time setting of
              shell variables, use the <filename>init</filename> extension
              script. Although the default setting is EXPORTPARAMS=Yes for
              compatibility, the recommended setting is
              EXPORTPARAMS=No.</para>

              <para>If the <filename>params</filename> file needs to set shell
              variables based on the configuration of the firewall system, you
              can use this trick:</para>

              <programlisting>EXT_IP=$(ssh root@firewall "/sbin/shorewall-lite call find_first_interface_address eth0")</programlisting>

              <para>The <command>shorewall-lite call</command> command allows
              you to to call interactively any Shorewall function that you can
              call in an extension script.</para>
            </listitem>
          </itemizedlist>
        </listitem>

        <listitem>
          <para>You must install Shorewall Lite on the system where you want
          to run the script. You then install the compiled program in
          /usr/share/shorewall-lite/firewall and use the /sbin/shorewall-lite
          program included with Shorewall Lite to control the firewall just as
          if the full Shorewall distribution was installed.</para>
        </listitem>
      </orderedlist>
    </section>
  </section>

  <section id="Compile">
    <title>The "shorewall compile" command</title>

    <para>A compiled script is produced using the <command>compile</command>
    command:</para>

    <blockquote>
      <para><command>shorewall compile [ -e ] [ &lt;directory name&gt; ]
      &lt;path name&gt;</command></para>
    </blockquote>

    <para>where</para>

    <blockquote>
      <variablelist>
        <varlistentry>
          <term>-e</term>

          <listitem>
            <para>Indicates that the program is to be "exported" to another
            system. When this flag is set, neither the "detectnets" interface
            option nor DYNAMIC_ZONES=Yes in shorewall.conf are allowed. The
            created program may be run on a system that has only Shorewall
            Lite installed</para>

            <para>When this flag is given, Shorewall does not probe the
            current system to determine the kernel/iptables features that it
            supports. It rather reads those capabilities from
            <filename>/etc/shorewall/capabilities</filename>. See below for
            details.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>&lt;directory name&gt;</term>

          <listitem>
            <para>specifies a directory to be searched for configuration files
            before those directories listed in the CONFIG_PATH variable in
            <filename>shorewall.conf</filename>.</para>

            <para>When -e &lt;directory-name&gt; is included, only the
            SHOREWALL_SHELL and VERBOSITY settings from
            <filename>/etc/shorewall/shorewall.conf</filename> are used and
            these apply only to the compiler itself. The settings used by the
            compiled firewall script are determined by the contents of
            <filename>&lt;directory name&gt;/shorewall.conf</filename>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term>&lt;path name&gt;</term>

          <listitem>
            <para>specifies the name of the script to be created.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </blockquote>
  </section>

  <section id="Lite">
    <title>Shorewall Lite</title>

    <para>Shorewall Lite is a companion product to Shorewall and is designed
    to allow you to maintain all Shorewall configuration information on a
    single system within your network.</para>

    <orderedlist numeration="loweralpha">
      <listitem>
        <para>You install the full Shorewall release on one system within your
        network. You need not configure Shorewall there and you may totally
        disable startup of Shorewall in your init scripts. For ease of
        reference, we call this system the 'administrative system'.</para>
      </listitem>

      <listitem>
        <para>On each system where you wish to run a Shorewall-generated
        firewall, you install Shorewall Lite. For ease of reference, we will
        call these systems the 'firewall systems'.</para>

        <note>
          <para>The firewall systems do <emphasis role="bold">NOT</emphasis>
          need to have the full Shorewall product installed but rather only
          the Shorewall Lite product. Shorewall and Shorewall Lite may be
          installed on the same system but that isn't encouraged.</para>
        </note>
      </listitem>

      <listitem>
        <para>On the administrative system you create a separate 'export
        directory' for each firewall system. You copy the contents of
        <filename
        class="directory">/usr/share/shorewall/configfiles</filename> into
        each export directory.</para>
      </listitem>

      <listitem>
        <para>The <filename>/etc/shorewall/shorewall.conf</filename> file is
        used to determine the VERBOSITY setting which determines how much
        output the compiler generates. All other settings are taken from the
        <filename>shorewall.conf </filename>file in the remote systems export
        directory.</para>

        <caution>
          <para>If you want to be able to allow non-root users to manage
          remote firewall systems, then the files
          <filename>/etc/shorewall/params</filename> and
          <filename>/etc/shorewall/shorewall.conf</filename> must be readable
          by all users on the administrative system. Not all packages secure
          the files that way and you may have to change the file permissions
          yourself.</para>
        </caution>
      </listitem>

      <listitem id="Debian">
        <para>On each firewall system, If you are running Debian or one of its
        derivatives like Ubuntu then edit
        <filename>/etc/default/shorewall-lite</filename> and set
        startup=1.</para>
      </listitem>

      <listitem>
        <para>On the administrative system, for each firewall system you do
        the following (this may be done by a non-root user who has root ssh
        access to the firewall system):</para>

        <orderedlist>
          <listitem>
            <para>modify the files in the corresponding export directory
            appropriately. It's a good idea to include the IP address of the
            administrative system in the <filename>routestopped</filename>
            file.</para>

            <para>It is important to understand that with Shorewall Lite, the
            firewall's export directory on the administrative system acts as
            <filename class="directory">/etc/shorewall</filename> for that
            firewall. So when the Shorewall documentation gives instructions
            for placing entries in files in the firewall's <filename
            class="directory">/etc/shorewall</filename>, when using Shorewall
            Lite you make those changes in the firewall's export directory on
            the administrative system.</para>

            <para>The CONFIG_PATH variable is treated as follows:</para>

            <itemizedlist>
              <listitem>
                <para>The value of CONFIG_PATH in
                <filename>/etc/shorewall/shorewall.conf</filename> is ignored
                when compiling for export (the -e option in given) and when
                the <command>load</command> or <command>reload</command>
                command is being executed (see below).</para>
              </listitem>

              <listitem>
                <para>The value of CONFIG_PATH in the
                <filename>shorewall.conf</filename> file in the export
                directory is used to search for configuration files during
                compilation of that configuration.</para>
              </listitem>

              <listitem>
                <para>The value of CONFIG_PATH used when the script is run on
                the firewall system is
                "/etc/shorewall-lite:/usr/share/shorewall-lite".</para>
              </listitem>
            </itemizedlist>
          </listitem>

          <listitem>
            <programlisting><command>cd &lt;export directory&gt;</command>
<command>/sbin/shorewall load -c firewall</command></programlisting>

            <para>The <ulink
            url="starting_and_stopping_shorewall.htm#Load"><command>load</command></ulink>
            command compiles a firewall script from the configuration files in
            the current working directory (using <command>shorewall compile
            -e</command>), copies that file to the remote system via scp and
            starts Shorewall Lite on the remote system via ssh. The -c option
            causes the capabilities of the remote system to be generated and
            copied to a file named capabilities in the export directory. See
            <link linkend="Shorecap">below</link>.</para>

            <para>Example (firewall's DNS name is 'gateway'):</para>

            <para><command>/sbin/shorewall load -c gateway</command><note>
                <para>Although scp and ssh are used by default, you can use
                other utilities by setting RSH_COMMAND and RCP_COMMAND in
                <filename>/etc/shorewall/shorewall.conf</filename>.</para>
              </note></para>
          </listitem>
        </orderedlist>
      </listitem>

      <listitem>
        <para>If you later need to change the firewall's configuration, change
        the appropriate files in the firewall's export directory then:</para>

        <programlisting><command>cd &lt;export directory&gt;</command>
<command>/sbin/shorewall reload firewall</command></programlisting>

        <para>The <ulink
        url="manpages/shorewall.html"><command>reload</command></ulink>
        command compiles a firewall script from the configuration files in the
        current working directory (using <command>shorewall compile
        -e</command>), copies that file to the remote system via scp and
        restarts Shorewall Lite on the remote system via ssh. The <emphasis
        role="bold">reload</emphasis> command also supports the '-c'
        option.</para>

        <para>I personally place a <filename>Makefile</filename> in each
        export directory as follows:</para>

        <blockquote>
          <programlisting>#     Shorewall Packet Filtering Firewall Export Directory Makefile - V3.3
#
#     This program is under GPL [http://www.gnu.org/licenses/old-licenses/gpl-2.0.txt]
#
#     (c) 2006 - Tom Eastep (teastep@shorewall.net)
#
#       Shorewall documentation is available at http://www.shorewall.net
#
#       This program is free software; you can redistribute it and/or modify
#       it under the terms of Version 2 of the GNU General Public License
#       as published by the Free Software Foundation.
#
#       This program is distributed in the hope that it will be useful,
#       but WITHOUT ANY WARRANTY; without even the implied warranty of
#       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
#       GNU General Public License for more details.
#
#       You should have received a copy of the GNU General Public License
#       along with this program; if not, write to the Free Software
#       Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
################################################################################
# Place this file in each export directory. Modify each copy to set HOST
# to the name of the remote firewall corresponding to the directory.
#
#       To make the 'firewall' script, type "make".
# 
#       Once the script is compiling correctly, you can install it by
#       typing "make install".
#  
################################################################################
#                             V A R I A B L E S
#
# Files in the export directory on which the firewall script does not depend
#
IGNOREFILES =  firewall% Makefile% trace% %~
#
# Remote Firewall system
#
HOST = gateway
#
# Save some typing
#
LITEDIR = /var/lib/shorewall-lite
#
# Set this if the remote system has a non-standard modules directory
#
MODULESDIR=
#
# Default target is the firewall script
#
################################################################################
#                                T A R G E T S
#
all: firewall
#
# Only generate the capabilities file if it doesn't already exist
#
capabilities: 
        ssh root@$(HOST) "MODULESDIR=$(MODULESDIR) /usr/share/shorewall-lite/shorecap &gt; $(LITEDIR)/capabilities"
        scp root@$(HOST):$(LITEDIR)/capabilities .
#
# Compile the firewall script. Using the 'wildcard' function causes "*" to be expanded so that
# 'filter-out' will be presented with the list of files in this directory rather than "*"
#
firewall: $(filter-out $(IGNOREFILES) capabilities , $(wildcard *) ) capabilities
        shorewall compile -e . firewall
#
# Only reload on demand.
#
install: firewall
        scp firewall firewall.conf root@$(HOST):$(LITEDIR)
        ssh root@$(HOST) "/sbin/shorewall-lite restart"
#
# Save running configuration
#
save:
        ssh root@$(HOST) "/sbin/shorewall-lite save"
#
# Remove generated files
#
clean: 
        rm -f capabilities firewall firewall.conf reload
</programlisting>
        </blockquote>

        <para>That way, after I've changed the configuration, I can simply
        type <command>make</command> or <emphasis role="bold">make
        install</emphasis>.</para>

        <note>
          <para>The above Makefile is available at <ulink
          url="http://www1.shorewall.net/pub/shorewall/contrib/Shorewall-lite/">http://www.shorewall.net/pub/shorewall/contrib/Shorewall-lite/</ulink></para>
        </note>

        <note>
          <para>I omit trace% because I often trace compiler execution while
          I'm debugging new versions of Shorewall.</para>
        </note>
      </listitem>
    </orderedlist>

    <para>There is a <filename>shorewall-lite.conf</filename> file installed
    as part of Shorewall Lite
    (<filename>/etc/shorewall-lite/shorewall-lite.conf</filename>). You can
    use that file on the firewall system to override some of the settings from
    the shorewall.conf file in the export directory.</para>

    <para>Settings that you can override are:</para>

    <blockquote>
      <simplelist>
        <member>VERBOSITY</member>

        <member>LOGFILE</member>

        <member>LOGFORMAT</member>

        <member>IPTABLES</member>

        <member>PATH</member>

        <member>SHOREWALL_SHELL</member>

        <member>SUBSYSLOCK</member>

        <member>RESTOREFILE</member>
      </simplelist>
    </blockquote>

    <para>You will normally not need to touch
    <filename>/etc/shorewall-lite/shorewall-lite.conf</filename> unless you
    run Debian or one of its derivatives (see <link
    linkend="Debian">above</link>).</para>

    <para>The <filename>/sbin/shorewall-lite</filename> program included with
    Shorewall Lite supports the same set of commands as the
    <filename>/sbin/shorewall</filename> program in a full Shorewall
    installation with the following exceptions:</para>

    <blockquote>
      <simplelist>
        <member>add</member>

        <member>compile</member>

        <member>delete</member>

        <member>refresh</member>

        <member>reload</member>

        <member>try</member>

        <member>safe-start</member>

        <member>safe-restart</member>

        <member>show actions</member>

        <member>show macros</member>
      </simplelist>
    </blockquote>

    <para>On systems with only Shorewall Lite installed, I recommend that you
    create a symbolic link <filename>/sbin/shorewall</filename> and point it
    at <filename>/sbin/shorewall-lite</filename>. That way, you can use
    <command>shorewall</command> as the command regardless of which product is
    installed.</para>

    <blockquote>
      <programlisting><command>ln -sf shorewall-lite /sbin/shorewall</command></programlisting>
    </blockquote>

    <section id="Converting">
      <title>Converting a system from Shorewall to Shorewall Lite</title>

      <para>Converting a firewall system that is currently running Shorewall
      to run Shorewall Lite instead is straight-forward.</para>

      <orderedlist numeration="loweralpha">
        <listitem>
          <para>On the administrative system, create an export directory for
          the firewall system.</para>
        </listitem>

        <listitem>
          <para>Copy the contents of <filename
          class="directory">/etc/shorewall/</filename> from the firewall
          system to the export directory on the administrative system.</para>
        </listitem>

        <listitem>
          <para>On the firewall system:</para>

          <para>Be sure that the IP address of the administrative system is
          included in the firewall's export directory
          <filename>routestopped</filename> file.</para>

          <programlisting><command>shorewall stop</command></programlisting>

          <para><emphasis role="bold">We recommend that you uninstall
          Shorewall at this point.</emphasis></para>
        </listitem>

        <listitem>
          <para>Install Shorewall Lite on the firewall system.</para>

          <para>If you are running Debian or one of its derivatives like
          Ubuntu then edit <filename>/etc/default/shorewall-lite</filename>
          and set startup=1.</para>
        </listitem>

        <listitem>
          <para>On the administrative system:</para>

          <para>It's a good idea to include the IP address of the
          administrative system in the firewall system's
          <filename>routestopped</filename> file.</para>

          <para>Also, edit the <filename>shorewall.conf</filename> file in the
          firewall's export directory and change the CONFIG_PATH setting to
          remove <filename class="directory">/etc/shorewall</filename>. You
          can replace it with <filename
          class="directory">/usr/share/shorewall/configfiles</filename> if you
          like.</para>

          <para>Example:</para>

          <blockquote>
            <para>Before editing:</para>

            <programlisting>CONFIG_PATH=/etc/shorewall:/usr/share/shorewall</programlisting>

            <para>After editing:</para>

            <programlisting>CONFIG_PATH=/usr/share/shorewall/configfiles:/usr/share/shorewall</programlisting>
          </blockquote>

          <para>Changing CONFIG_PATH will ensure that subsequent compilations
          using the export directory will not include any files from <filename
          class="directory">/etc/shorewall</filename> other than
          <filename>shorewall.conf</filename> and
          <filename>params</filename>.</para>

          <para>If you set variables in the params file, there are a couple of
          issues:</para>

          <para>The <filename>params</filename> file is not processed at run
          time if you set EXPORTPARAMS=No in
          <filename>shorewall.conf</filename>. For run-time setting of shell
          variables, use the <filename>init</filename> extension
          script.</para>

          <para>If the <filename>params</filename> file needs to set shell
          variables based on the configuration of the firewall system, you can
          use this trick:</para>

          <programlisting>EXT_IP=$(ssh root@firewall "/sbin/shorewall-lite call find_first_interface_address eth0")</programlisting>

          <para>The <command>shorewall-lite call</command> command allows you
          to to call interactively any Shorewall function that you can call in
          an extension script.</para>

          <para>After having made the above changes to the firewall's export
          directory, execute the following commands.</para>

          <blockquote>
            <programlisting><command>cd &lt;export directory&gt;</command>
<command>/sbin/shorewall load -c &lt;firewall system&gt;</command>
</programlisting>

            <para>Example (firewall's DNS name is 'gateway'):</para>

            <para><command>/sbin/shorewall load -c gateway</command></para>
          </blockquote>

          <para>The <ulink
          url="starting_and_stopping_shorewall.htm#Load"><command>load</command></ulink>
          command compiles a firewall script from the configuration files in
          the current working directory (using <command>shorewall compile
          -e</command>), copies that file to the remote system via
          <command>scp</command> and starts Shorewall Lite on the remote
          system via <command>ssh</command>.</para>
        </listitem>

        <listitem>
          <para>If you later need to change the firewall's configuration,
          change the appropriate files in the firewall's export directory
          then:</para>

          <programlisting><command>cd &lt;export directory&gt;</command>
<command>/sbin/shorewall reload firewall</command></programlisting>

          <para>The <ulink
          url="starting_and_stopping_shorewall.htm#Reload"><command>reload</command></ulink>
          command compiles a firewall script from the configuration files in
          the current working directory (using <command>shorewall compile
          -e</command>), copies that file to the remote system via
          <command>scp</command> and restarts Shorewall Lite on the remote
          system via <command>ssh</command>.</para>
        </listitem>

        <listitem>
          <para>If the kernel/iptables configuration on the firewall later
          changes and you need to create a new
          <filename>capabilities</filename> file, do the following on the
          firewall system:</para>

          <programlisting><command>/usr/share/shorewall-lite/shorecap &gt; capabilities</command>
<command>scp capabilities &lt;admin system&gt;:&lt;this system's config dir&gt;</command></programlisting>

          <para>Or simply use the -c option the next time that you use the
          <command>reload</command> command.</para>
        </listitem>
      </orderedlist>
    </section>
  </section>

  <section id="Shorecap">
    <title>The /etc/shorewall/capabilities file and the shorecap
    program</title>

    <para>As mentioned above, the
    <filename>/etc/shorewall/capabilities</filename> file specifies that
    kernel/iptables capabilities of the target system. Here is a sample
    file:</para>

    <blockquote>
      <programlisting>#
# Shorewall detected the following iptables/netfilter capabilities - Tue Jul 15 07:28:12 PDT 2008
#
NAT_ENABLED=Yes
MANGLE_ENABLED=Yes
MULTIPORT=Yes
XMULTIPORT=Yes
CONNTRACK_MATCH=Yes
USEPKTTYPE=Yes
POLICY_MATCH=Yes
PHYSDEV_MATCH=Yes
PHYSDEV_BRIDGE=Yes
LENGTH_MATCH=Yes
IPRANGE_MATCH=Yes
RECENT_MATCH=Yes
OWNER_MATCH=Yes
IPSET_MATCH=Yes
CONNMARK=Yes
XCONNMARK=Yes
CONNMARK_MATCH=Yes
XCONNMARK_MATCH=Yes
RAW_TABLE=Yes
IPP2P_MATCH=
CLASSIFY_TARGET=Yes
ENHANCED_REJECT=Yes
KLUDGEFREE=Yes
MARK=Yes
XMARK=Yes
MANGLE_FORWARD=Yes
COMMENTS=Yes
ADDRTYPE=Yes
TCPMSS_MATCH=Yes
HASHLIMIT_MATCH=Yes
NFQUEUE_TARGET=Yes
REALM_MATCH=Yes
CAPVERSION=40190</programlisting>
    </blockquote>

    <para>As you can see, the file contains a simple list of shell variable
    assignments — the variables correspond to the capabilities listed by the
    <command>shorewall show capabilities</command> command and they appear in
    the same order as the output of that command.</para>

    <para>To aid in creating this file, Shorewall Lite includes a
    <command>shorecap</command> program. The program is installed in the
    <filename class="directory">/usr/share/shorewall-lite/</filename>
    directory and may be run as follows:</para>

    <blockquote>
      <para><command>[ IPTABLES=&lt;iptables binary&gt; ] [
      MODULESDIR=&lt;kernel modules directory&gt; ]
      /usr/share/shorewall-lite/shorecap &gt; capabilities</command></para>
    </blockquote>

    <para>The IPTABLES and MODULESDIR options have their <ulink
    url="manpages/shorewall.conf.html">usual Shorewall default
    values</ulink>.</para>

    <para>The <filename>capabilities</filename> file may then be copied to a
    system with Shorewall installed and used when compiling firewall programs
    to run on the remote system.</para>

    <para>The <filename>capabilities</filename> file may also be creating
    using <filename>/sbin/shorewall-lite</filename>:<blockquote>
        <para><command>shorewall-lite show -f capabilities &gt;
        capabilities</command></para>
      </blockquote></para>

    <para>Note that unlike the <command>shorecap</command> program, the
    <command>show capabilities</command> command shows the kernel's current
    capabilities; it does not attempt to load additional kernel
    modules.</para>
  </section>

  <section id="Running">
    <title>Running compiled programs directly</title>

    <para>Compiled firewall programs are complete programs that support the
    following command line forms:</para>

    <blockquote>
      <simplelist>
        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        start</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        stop</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        clear</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        refresh</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        reset</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        restart</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        status</command></member>

        <member><command>&lt;program&gt; [ -q ] [ -v ] [ -n ]
        version</command></member>
      </simplelist>
    </blockquote>

    <para>The options have the same meanings as when they are passed to
    <filename>/sbin/shorewall</filename> itself. The default VERBOSITY level
    is the level specified in the <filename>shorewall.conf</filename> file
    used when the program was compiled.</para>
  </section>
</article>