shorewall_code/docs/Shorewall-5.xml

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  <articleinfo>
    <title>Shorewall 5</title>

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

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

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

    <copyright>
      <year>2015</year>

      <year>2016</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>

  <section>
    <title>Introduction</title>

    <para>There are currently three principle groups of changes that
    distinguish Shorewall 5 from Shorewall 4:</para>

    <orderedlist>
      <listitem>
        <para>Cruft Removal - over the years, as new ways to accomplish
        various tasks are added to Shorewall, support for the old way of doing
        things has generally been retained but deprecated. Shorewall 5 drops
        support for those deprecated features.</para>
      </listitem>

      <listitem>
        <para>Changes to CLI commands - In order to make command names more
        accurately reflect what the associated commands do, a number of
        commands have been renamed or the function that they perform has been
        changed.</para>
      </listitem>

      <listitem>
        <para>CLI unification - Beginning with Shorewall 5.1.0, there is a
        single CLI program (<filename>/sbin/shorewall </filename>or
        <filename>/usr/sbin/shorewall</filename> depending on your
        distribution).</para>
      </listitem>
    </orderedlist>

    <para>Each of these groups is described in more detail in the sections
    that follow.</para>
  </section>

  <section>
    <title>Cruft Removal</title>

    <para>Removal of superseded features makes the code cleaner and easier to
    extend while also reducing compilation and execution time. The following
    subsections detail the features that are no longer supported in Shorewall
    5.</para>

    <section>
      <title>Scripts Compiled with Shorewall 4.4.7 or Earlier</title>

      <para>Shorewall 5 cannot correctly run scripts compiled with Shorewall
      4.4.7 or earlier releases. Such scripts must be recompiled with 4.4.8 or
      later prior to upgrading to Shorewall 5.</para>
    </section>

    <section>
      <title>Workarounds</title>

      <para>Over the years, a number of workarounds have been added to
      Shorewall to work around defects in other products. In current
      distributions, those defects have been corrected, and in 4.6.11, a
      WORKAROUNDS configuration option was added to disable those workarounds.
      In Shorewall 5, the WORKAROUNDS setting is still available in the
      shorewall[6].conf files but:</para>

      <orderedlist>
        <listitem>
          <para>Its default setting has been changed to No.</para>
        </listitem>

        <listitem>
          <para>All workarounds for old distributions have been
          eliminated.</para>
        </listitem>
      </orderedlist>

      <para>If there is a need to add new workarounds in the future, those
      workarounds will be enabled by WORKAROUNDS=Yes.</para>
    </section>

    <section>
      <title>Removal of Configuration Options</title>

      <para>A number of configuration options have been eliminated in
      Shorewall 5. The following options have been eliminated and the
      functionality that they enabled is been removed:</para>

      <itemizedlist>
        <listitem>
          <para>EXPORTPARAMS</para>
        </listitem>

        <listitem>
          <para>IPSECFILE</para>
        </listitem>

        <listitem>
          <para>LEGACY_FASTSTART</para>
        </listitem>

        <listitem>
          <para>CHAIN_SCRIPTS (Removed in Shorewall 5.1).</para>
        </listitem>
      </itemizedlist>

      <para>A compilation warning is issued when any of these options are
      encountered in the .conf file, and the <command>shorewall[6]
      update</command> command will remove them from the configuration
      file.</para>

      <para>These options have been eliminated because they have been
      superseded by newer options.</para>

      <itemizedlist>
        <listitem>
          <para>LOGRATE and LOGBURST (superseded by LOGLIMIT)</para>
        </listitem>

        <listitem>
          <para>WIDE_TC_MARKS (superseded by TC_BITS)</para>
        </listitem>

        <listitem>
          <para>HIGH_ROUTE_MARKS (superseded by PROVIDER_OFFSET)</para>
        </listitem>

        <listitem>
          <para>BLACKLISTNEWONLY (superseded by BLACKLIST)</para>
        </listitem>
      </itemizedlist>

      <para>A fatal compilation error is emitted if any of these options are
      present in the .conf file, and the <command>shorewall[6]
      update</command> command will replace these options with equivalent
      setting of the options that supersede them.</para>
    </section>

    <section>
      <title>Obsolete Configuration Files</title>

      <para>Support has been removed for the 'blacklist', 'tcrules',
      'routestopped', 'notrack' and 'tos' files.</para>

      <para>The <option>-t</option> and <option>-b</option> options of the
      <command>update</command> command are still available to convert the
      'tcrules' and 'tos' files to the equivalent 'mangle' file and to convert
      the 'blacklist' file into an equivalent 'blrules' file.</para>

      <para>As in Shorewall 4.6.12, the <option>-s</option> option is
      available to convert the 'routestopped' file into the equivalent
      'stoppedrules' file and the <option>-n</option> option is available to
      convert a 'notrack' file to the equivalent 'conntrack' file.</para>
    </section>

    <section>
      <title>Macro and Action Formats</title>

      <para>Originally, macro and action files had formats that were different
      from that of the rules file,</para>

      <para>Format-1 action files had the following columns:</para>

      <itemizedlist>
        <listitem>
          <para>TARGET</para>
        </listitem>

        <listitem>
          <para>SOURCE</para>
        </listitem>

        <listitem>
          <para>DEST</para>
        </listitem>

        <listitem>
          <para>PROTO</para>
        </listitem>

        <listitem>
          <para>DEST PORT(S)</para>
        </listitem>

        <listitem>
          <para>SOURCE PORT(S)</para>
        </listitem>

        <listitem>
          <para>RATE</para>
        </listitem>

        <listitem>
          <para>USER/GROUP</para>
        </listitem>

        <listitem>
          <para>MARK</para>
        </listitem>
      </itemizedlist>

      <para>Format-1 macro files were similar but did not support the MARK
      column.</para>

      <para>Format-2 macro and action files have these columns:</para>

      <itemizedlist>
        <listitem>
          <para>TARGET</para>
        </listitem>

        <listitem>
          <para>SOURCE</para>
        </listitem>

        <listitem>
          <para>DEST</para>
        </listitem>

        <listitem>
          <para>PROTO</para>
        </listitem>

        <listitem>
          <para>DPORT</para>
        </listitem>

        <listitem>
          <para>SPORT</para>
        </listitem>

        <listitem>
          <para>ORIGDEST</para>
        </listitem>

        <listitem>
          <para>RATE</para>
        </listitem>

        <listitem>
          <para>USER/GROUP</para>
        </listitem>

        <listitem>
          <para>MARK</para>
        </listitem>

        <listitem>
          <para>CONNLIMIT</para>
        </listitem>

        <listitem>
          <para>TIME</para>
        </listitem>

        <listitem>
          <para>HEADERS (Only valid for IPv6)</para>
        </listitem>

        <listitem>
          <para>SWITCH</para>
        </listitem>

        <listitem>
          <para>HELPER</para>
        </listitem>
      </itemizedlist>

      <para>Notice that the first five columns of both sets are the same
      (although the port-valued column names have changed, the contents are
      the same).</para>

      <para>In Shorewall 5, support for format-1 macros and actions has been
      dropped and all macros and actions will be processed as if ?FORMAT 2
      were included before the first entry. Given that the vast majority of
      actions and macros only use the first five columns, this change will be
      of no concern to most users, but will cause compilation errors if
      columns beyold the fifth one are populated.</para>
    </section>

    <section>
      <title>COMMENT, FORMAT and SECTION Lines</title>

      <para>COMMENT, FORMAT and SECTION Lines now require the leading question
      mark ("?"). In earlier releases, the question mark was optional. The
      <command>shorewall[6] update -D</command> command in Shorewall 4.6 will
      insert the question marks for you.</para>
    </section>
  </section>

  <section>
    <title>CLI Command Changes</title>

    <para>A number of commands have been renamed and/or now perform a
    different function.</para>

    <section>
      <title>restart</title>

      <para>The <command>restart</command> command now does a true restart and
      is equivalent to a <command>stop</command> followed by a
      <command>start</command>.</para>
    </section>

    <section>
      <title>load</title>

      <para>The function performed by the Shorewall-4 <command>load</command>
      command is now performed by the <command>remote-start</command>
      command.</para>
    </section>

    <section>
      <title>reload</title>

      <para>In Shorewall 5, the <command>reload</command> command now performs
      the same function as the <command>restart</command> command did in
      Shorewall 4. The action taken by the Shorewall-4
      <command>reload</command> command is now performed by the
      <command>remote-restart</command> command.</para>

      <para>For those that can't get used to the idea of using
      <command>reload</command> in place of <command>restart</command>, a
      RESTART option has been added to shorewall[6].conf. The option defaults
      to 'restart' but if set to 'reload', then the <command>restart</command>
      command does what it did in earlier releases.</para>

      <note>
        <para>Beginning with Shorewall 5.0.1 and Shorewall 4.6.13.2, the
        update command will set RESTART=reload to maintain compatibility with
        earlier releases. Shorewall 5.0.0 created the setting
        LEGACY_RESTART=No which was equivalent to RESTART=restart. Under
        Shorewall 5.0.1 and later, update will convert LEGACY_RESTART to the
        equivalent RESTART setting.</para>
      </note>
    </section>
  </section>

  <section>
    <title>CLI Unification</title>

    <para>Prior to Shorewall 5.1, there were four separate CLI
    programs:</para>

    <itemizedlist>
      <listitem>
        <para><filename>/sbin/shorewall </filename>or
        <filename>/usr/sbin/shorewall</filename> depending on your
        distribution. Packaged with Shorewall and used to control
        Shorewall.</para>
      </listitem>

      <listitem>
        <para><filename>/sbin/shorewall6 </filename>or
        <filename>/usr/sbin/shorewall6</filename> depending on your
        distribution. Packaged with Shorewall6 and used to control
        Shorewall6.</para>
      </listitem>

      <listitem>
        <para><filename>/sbin/shorewall-lite </filename>or
        <filename>/usr/sbin/shorewall-lite</filename> depending on your
        distribution. Packaged with Shorewall-lite and used to control
        Shorewall-lite.</para>
      </listitem>

      <listitem>
        <para><filename>/sbin/shorewall6-lite </filename>or
        <filename>/usr/sbin/shorewall6-lite</filename> depending on your
        distribution. Packaged with Shorewall6-lite and used to control
        Shorewall6-lite.</para>
      </listitem>
    </itemizedlist>

    <para>Each of these programs had their own (largely duplicated)
    manpage.</para>

    <para>Beginning with Shorewall 5.1, there is a single CLI program
    (<filename>/sbin/shorewall</filename> or
    <filename>/usr/sbin/shorewall</filename>) packaged with Shorewall-core.
    The Shorewall6, Shorewall-lite and Shorewall6-lite packages create a
    symbolic link to that program; the links are named shorewall6,
    shorewall-lite and shorewall6-lite respectively. These symbolic links are
    for backward compatibility only; all four products can be managed using
    the single CLI program itself. The manpages shorewall6(8),
    shorewall-lite(8) and shorewall6-lite(8) are skeletal and refer the reader
    to shorewall(8).</para>
  </section>

  <section>
    <title>Upgrading to Shorewall 5</title>

    <para>It is strongly recommended that you first upgrade your installation
    to a 4.6 release that supports the <option>-A</option> option to the
    <command>update</command> command; 4.6.13.2 or later is preferred.</para>

    <para>Once you are on that release, execute the <command>shorewall update
    -A</command> command (and <command>shorewall6 update -A</command> if you
    also have Shorewall6).</para>

    <para>Finally, add ?FORMAT 2 to each of your macro and action files and be
    sure that the check command does not produce errors -- if it does, you can
    shuffle the columns around to make them work on both Shorewall 4 and
    Shorewall 5.</para>

    <para>These steps can also be taken after you upgrade, but your firewall
    likely won't start or work correctly until you do.</para>

    <para>The <command>update</command> command in Shorewall 5 has many fewer
    options. The <option>-b</option>, <option>-t</option>,
    <option>-n</option>, <option>-D</option> and <option>-s </option>options
    have been removed -- the updates triggered by those options are now
    performed unconditionally. The <option>-i </option>and <option>-A
    </option>options have been retained - both enable checking for issues that
    could result if INLINE_MATCHES were to be set to Yes.</para>

    <section>
      <title id="CHAIN_SCRIPTS">CHAIN_SCRIPTS Removal</title>

      <para>Prior to the availability of ?[BEGIN] PERL .... ?END PERL, the
      only way to create Perl code to insert rules into a chain was to use a
      per-Chain script with the same name as the chain. The most common use of
      these scripts was with Actions where an action A would have an empty
      action.A file and then a file named A that contained Perl code. This was
      a hack, at best, and has been deprecated since embedded Perl has been
      available in action files.</para>

      <para>In Shorewall 5.1, the compiler notices that action.A is empty and
      looks for a file named A on the CONFIG_PATH. If that file is found, the
      compiler raises a fatal error:</para>

      <programlisting>    ERROR: File action.A is empty and file A exists - the two must be combined as described in the Migration Considerations section of the Shorewall release notes</programlisting>

      <para>To resolve this issue, one of two approaches can be taken
      depending on what the script A does.</para>

      <itemizedlist>
        <listitem>
          <para>If script A is simply inserting rules with ip[6]tables matches
          and/or targets that Shorewall doesn't directly support, they can
          probably be coded in the action.A file using the IP[6]TABLES action
          and/or inline matches. For example, the following script
          <filename>DNSDDOS</filename></para>

          <programlisting>use Shorewall::Chains;

add_rule $chainref, q(-m string --algo bm --from 30 --to 31 --hex-string "|010000010000000000000000020001|" -j DROP);
add_rule $chainref, q(-m string --algo bm --from 30 --to 31 --hex-string "|000000010000000000000000020001|" -j DROP);
add_rule $chainref, q(-j ACCEPT);

1;</programlisting>

          <para>can be coded in <filename>action.DNSDDOS</filename> as:</para>

          <programlisting>DROP    -       -       ;; -m string --algo bm --from 30 --to 31 --hex-string "|010000010000000000000000020001|"
DROP    -       -       ;; -m string --algo bm --from 30 --to 31 --hex-string "|000000010000000000000000020001|"
ACCEPT  -       -</programlisting>
        </listitem>

        <listitem>
          <para>The other approach is to simply convert A into embedded Perl
          in action.A. Consider this <filename>SSHKnock</filename>
          script:</para>

          <programlisting>use Shorewall::Chains;

if ( $level ) {
    log_rule_limit( $level, 
                    $chainref, 
                    'SSHKnock',
                    'ACCEPT',
                    '',
                    $tag,
                    'add',
                    '-p tcp --dport 22   -m recent --rcheck --name SSH ' );
     log_rule_limit( $level,
                     $chainref,
                     'SSHKnock',
                     'DROP',
                     '',
                     $tag,
                     'add',
                     '-p tcp --dport ! 22 ' );
}
add_rule( $chainref, '-p tcp --dport 22   -m recent --rcheck --seconds 60 --name SSH          -j ACCEPT' );
add_rule( $chainref, '-p tcp --dport 632 -m recent                        --name SSH --remove -j DROP' );
add_rule( $chainref, '-p tcp --dport 633 -m recent                        --name SSH --set    -j DROP' );
add_rule( $chainref, '-p tcp --dport 634 -m recent                        --name SSH --remove -j DROP' );
1;</programlisting>

          <para>Because this script uses the implicit $level and $tag
          variables, it must remain in Perl. This mostly involves simply
          moving the <filename>SSHKnock</filename> script into
          <filename>action.SSHKnock</filename>, but requires some additional
          code in <filename>action.SSHKnock</filename> as shown in <emphasis
          role="bold">bold font</emphasis> below:</para>

          <programlisting><emphasis role="bold">?begin perl</emphasis>

<emphasis role="bold">use Shorewall::Config;</emphasis>
use Shorewall::Chains;

<emphasis role="bold">my $chainref        = get_action_chain;
my ( $level, $tag ) = get_action_logging;</emphasis>

if ( $level ) {
    log_rule_limit( $level, 
                    $chainref, 
                    'SSHKnock',
                    'ACCEPT',
                    '',
                    $tag,
                    'add',
                    '-p tcp --dport 22   -m recent --rcheck --name SSH ' );

    log_rule_limit( $level,
                    $chainref,
                    'SSHKnock',
                    'DROP',
                    '',
                    $tag,
                    'add',
                    '-p tcp --dport ! 22 ' );
}

add_rule( $chainref, '-p tcp --dport 22   -m recent --rcheck --seconds 60 --name SSH          -j ACCEPT' );
add_rule( $chainref, '-p tcp --dport 632 -m recent                        --name SSH --remove -j DROP' );
add_rule( $chainref, '-p tcp --dport 633 -m recent                        --name SSH --set    -j DROP' );
add_rule( $chainref, '-p tcp --dport 634 -m recent                        --name SSH --remove -j DROP' );
1;

<emphasis role="bold">?end perl</emphasis></programlisting>
        </listitem>
      </itemizedlist>
    </section>
  </section>
</article>