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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<title>Chapter�4.�Advanced DNS Features</title>
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<tr><th colspan="3" align="center">Chapter�4.�Advanced DNS Features</th></tr>
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fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<td width="20%" align="left">
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<a accesskey="p" href="Bv9ARM.ch03.html">Prev</a>�</td>
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14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<td width="20%" align="right">�<a accesskey="n" href="Bv9ARM.ch05.html">Next</a>
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14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<hr>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</div>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<div class="chapter" lang="en">
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<div class="titlepage"><div><div><h2 class="title">
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User<a name="Bv9ARM.ch04"></a>Chapter�4.�Advanced DNS Features</h2></div></div></div>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User<div class="toc">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<p><b>Table of Contents</b></p>
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User<dl>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#notify">Notify</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect1"><a href="Bv9ARM.ch04.html#dynamic_update">Dynamic Update</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch04.html#journal">The journal file</a></span></dt></dl></dd>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect1"><a href="Bv9ARM.ch04.html#incremental_zone_transfers">Incremental Zone Transfers (IXFR)</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2570508">Split DNS</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2570526">Example split DNS setup</a></span></dt></dl></dd>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect1"><a href="Bv9ARM.ch04.html#tsig">TSIG</a></span></dt>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dd><dl>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571028">Generate Shared Keys for Each Pair of Hosts</a></span></dt>
f9ce6280cec79deb16ff6d9807aa493ff23e10d9Tinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571101">Copying the Shared Secret to Both Machines</a></span></dt>
0b89eee6167201843c9a46b7e7c63cb1e4e09ba3Tinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571112">Informing the Servers of the Key's Existence</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571155">Instructing the Server to Use the Key</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571281">TSIG Key Based Access Control</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571330">Errors</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</dl></dd>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2571412">TKEY</a></span></dt>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2571461">SIG(0)</a></span></dt>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#DNSSEC">DNSSEC</a></span></dt>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<dd><dl>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571666">Generating Keys</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571813">Signing the Zone</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571894">Configuring Servers</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User</dl></dd>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2572064">IPv6 Support in <acronym class="acronym">BIND</acronym> 9</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dd><dl>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2572262">Address Lookups Using AAAA Records</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2572283">Address to Name Lookups Using Nibble Format</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</dl></dd>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User</dl>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</div>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<div class="sect1" lang="en">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<div class="titlepage"><div><div><h2 class="title" style="clear: both">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<a name="notify"></a>Notify</h2></div></div></div>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <acronym class="acronym">DNS</acronym> NOTIFY is a mechanism that allows master
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User servers to notify their slave servers of changes to a zone's data. In
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt response to a <span><strong class="command">NOTIFY</strong></span> from a master server, the
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User slave will check to see that its version of the zone is the
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User current version and, if not, initiate a zone transfer.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User </p>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<p>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User For more information about <acronym class="acronym">DNS</acronym>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User <span><strong class="command">NOTIFY</strong></span>, see the description of the
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User <span><strong class="command">notify</strong></span> option in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a> and
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User the description of the zone option <span><strong class="command">also-notify</strong></span> in
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>. The <span><strong class="command">NOTIFY</strong></span>
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User protocol is specified in RFC 1996.
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User </p>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User<h3 class="title">Note</h3>
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User As a slave zone can also be a master to other slaves, <span><strong class="command">named</strong></span>,
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User by default, sends <span><strong class="command">NOTIFY</strong></span> messages for every zone
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User it loads. Specifying <span><strong class="command">notify master-only;</strong></span> will
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User cause <span><strong class="command">named</strong></span> to only send <span><strong class="command">NOTIFY</strong></span> for master
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User zones that it loads.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User </div>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User</div>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<div class="sect1" lang="en">
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<div class="titlepage"><div><div><h2 class="title" style="clear: both">
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<a name="dynamic_update"></a>Dynamic Update</h2></div></div></div>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User<p>
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User Dynamic Update is a method for adding, replacing or deleting
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User records in a master server by sending it a special form of DNS
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User messages. The format and meaning of these messages is specified
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User in RFC 2136.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User </p>
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Dynamic update is enabled by including an
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User <span><strong class="command">allow-update</strong></span> or an <span><strong class="command">update-policy</strong></span>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User clause in the <span><strong class="command">zone</strong></span> statement.
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User </p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User If the zone's <span><strong class="command">update-policy</strong></span> is set to
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <strong class="userinput"><code>local</code></strong>, updates to the zone
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User will be permitted for the key <code class="varname">local-ddns</code>,
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User which will be generated by <span><strong class="command">named</strong></span> at startup.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a> for more details.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User </p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The <span><strong class="command">tkey-gssapi-credential</strong></span> and
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User <span><strong class="command">tkey-domain</strong></span> clauses in the
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User <span><strong class="command">options</strong></span> statement enable the
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User server to negotiate keys that can be matched against those
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User in <span><strong class="command">update-policy</strong></span> or
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User <span><strong class="command">allow-update</strong></span>.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User Updating of secure zones (zones using DNSSEC) follows RFC
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User 3007: RRSIG, NSEC and NSEC3 records affected by updates are
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User automatically regenerated by the server using an online
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User zone key. Update authorization is based on transaction
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User signatures and an explicit server policy.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<div class="sect2" lang="en">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<div class="titlepage"><div><div><h3 class="title">
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User<a name="journal"></a>The journal file</h3></div></div></div>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User<p>
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User All changes made to a zone using dynamic update are stored
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User in the zone's journal file. This file is automatically created
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User by the server when the first dynamic update takes place.
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User The name of the journal file is formed by appending the extension
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User <code class="filename">.jnl</code> to the name of the
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User corresponding zone
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User file unless specifically overridden. The journal file is in a
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User binary format and should not be edited manually.
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User </p>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User The server will also occasionally write ("dump")
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User the complete contents of the updated zone to its zone file.
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User This is not done immediately after
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User each dynamic update, because that would be too slow when a large
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User zone is updated frequently. Instead, the dump is delayed by
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User up to 15 minutes, allowing additional updates to take place.
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User </p>
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User<p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User When a server is restarted after a shutdown or crash, it will replay
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User the journal file to incorporate into the zone any updates that
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User took
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User place after the last zone dump.
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User Changes that result from incoming incremental zone transfers are
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User also
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User journalled in a similar way.
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User </p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User<p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User The zone files of dynamic zones cannot normally be edited by
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User hand because they are not guaranteed to contain the most recent
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User dynamic changes &#8212; those are only in the journal file.
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User The only way to ensure that the zone file of a dynamic zone
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User is up to date is to run <span><strong class="command">rndc stop</strong></span>.
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User </p>
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User<p>
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User If you have to make changes to a dynamic zone
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User manually, the following procedure will work: Disable dynamic updates
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User to the zone using
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User <span><strong class="command">rndc freeze <em class="replaceable"><code>zone</code></em></strong></span>.
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User This will also remove the zone's <code class="filename">.jnl</code> file
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User and update the master file. Edit the zone file. Run
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User <span><strong class="command">rndc thaw <em class="replaceable"><code>zone</code></em></strong></span>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User to reload the changed zone and re-enable dynamic updates.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User</div>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</div>
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User<div class="sect1" lang="en">
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User<div class="titlepage"><div><div><h2 class="title" style="clear: both">
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User<a name="incremental_zone_transfers"></a>Incremental Zone Transfers (IXFR)</h2></div></div></div>
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User<p>
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User The incremental zone transfer (IXFR) protocol is a way for
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User slave servers to transfer only changed data, instead of having to
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User transfer the entire zone. The IXFR protocol is specified in RFC
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User 1995. See <a href="Bv9ARM.ch09.html#proposed_standards">Proposed Standards</a>.
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User </p>
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User<p>
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User When acting as a master, <acronym class="acronym">BIND</acronym> 9
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User supports IXFR for those zones
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User where the necessary change history information is available. These
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User include master zones maintained by dynamic update and slave zones
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User whose data was obtained by IXFR. For manually maintained master
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User zones, and for slave zones obtained by performing a full zone
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User transfer (AXFR), IXFR is supported only if the option
d253648fe3331622cebea02d60aaecca3082d78dTinderbox User <span><strong class="command">ixfr-from-differences</strong></span> is set
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User to <strong class="userinput"><code>yes</code></strong>.
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User </p>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User<p>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User When acting as a slave, <acronym class="acronym">BIND</acronym> 9 will
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User attempt to use IXFR unless
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User it is explicitly disabled. For more information about disabling
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User IXFR, see the description of the <span><strong class="command">request-ixfr</strong></span> clause
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User of the <span><strong class="command">server</strong></span> statement.
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User </p>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User</div>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User<div class="sect1" lang="en">
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User<div class="titlepage"><div><div><h2 class="title" style="clear: both">
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User<a name="id2570508"></a>Split DNS</h2></div></div></div>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User<p>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User Setting up different views, or visibility, of the DNS space to
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User internal and external resolvers is usually referred to as a
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User <span class="emphasis"><em>Split DNS</em></span> setup. There are several
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User reasons an organization would want to set up its DNS this way.
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User </p>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User<p>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User One common reason for setting up a DNS system this way is
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User to hide "internal" DNS information from "external" clients on the
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User Internet. There is some debate as to whether or not this is actually
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User useful.
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User Internal DNS information leaks out in many ways (via email headers,
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User for example) and most savvy "attackers" can find the information
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User they need using other means.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt However, since listing addresses of internal servers that
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User external clients cannot possibly reach can result in
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User connection delays and other annoyances, an organization may
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User choose to use a Split DNS to present a consistent view of itself
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User to the outside world.
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User </p>
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User<p>
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User Another common reason for setting up a Split DNS system is
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User to allow internal networks that are behind filters or in RFC 1918
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User space (reserved IP space, as documented in RFC 1918) to resolve DNS
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User on the Internet. Split DNS can also be used to allow mail from outside
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User back in to the internal network.
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User </p>
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User<div class="sect2" lang="en">
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User<div class="titlepage"><div><div><h3 class="title">
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User<a name="id2570526"></a>Example split DNS setup</h3></div></div></div>
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User<p>
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User Let's say a company named <span class="emphasis"><em>Example, Inc.</em></span>
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User (<code class="literal">example.com</code>)
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User has several corporate sites that have an internal network with
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User reserved
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User Internet Protocol (IP) space and an external demilitarized zone (DMZ),
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User or "outside" section of a network, that is available to the public.
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User </p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User <span class="emphasis"><em>Example, Inc.</em></span> wants its internal clients
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User to be able to resolve external hostnames and to exchange mail with
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User people on the outside. The company also wants its internal resolvers
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User to have access to certain internal-only zones that are not available
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User at all outside of the internal network.
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User </p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User In order to accomplish this, the company will set up two sets
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User of name servers. One set will be on the inside network (in the
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User reserved
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User IP space) and the other set will be on bastion hosts, which are
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User "proxy"
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User hosts that can talk to both sides of its network, in the DMZ.
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User The internal servers will be configured to forward all queries,
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User except queries for <code class="filename">site1.internal</code>, <code class="filename">site2.internal</code>, <code class="filename">site1.example.com</code>,
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User and <code class="filename">site2.example.com</code>, to the servers
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User in the
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User DMZ. These internal servers will have complete sets of information
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User for <code class="filename">site1.example.com</code>, <code class="filename">site2.example.com</code>, <code class="filename">site1.internal</code>,
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User and <code class="filename">site2.internal</code>.
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User To protect the <code class="filename">site1.internal</code> and <code class="filename">site2.internal</code> domains,
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User the internal name servers must be configured to disallow all queries
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt to these domains from any external hosts, including the bastion
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User hosts.
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User </p>
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User<p>
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User The external servers, which are on the bastion hosts, will
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User be configured to serve the "public" version of the <code class="filename">site1</code> and <code class="filename">site2.example.com</code> zones.
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User This could include things such as the host records for public servers
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User (<code class="filename">www.example.com</code> and <code class="filename">ftp.example.com</code>),
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User and mail exchange (MX) records (<code class="filename">a.mx.example.com</code> and <code class="filename">b.mx.example.com</code>).
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User </p>
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User<p>
111d5ef471ecec90671f480afd8f93e550a80917Tinderbox User In addition, the public <code class="filename">site1</code> and <code class="filename">site2.example.com</code> zones
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User should have special MX records that contain wildcard (`*') records
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User pointing to the bastion hosts. This is needed because external mail
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User servers do not have any other way of looking up how to deliver mail
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User to those internal hosts. With the wildcard records, the mail will
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User be delivered to the bastion host, which can then forward it on to
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User internal hosts.
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User </p>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<p>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User Here's an example of a wildcard MX record:
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User </p>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User<pre class="programlisting">* IN MX 10 external1.example.com.</pre>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User<p>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User Now that they accept mail on behalf of anything in the internal
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User network, the bastion hosts will need to know how to deliver mail
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User to internal hosts. In order for this to work properly, the resolvers
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User on
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User the bastion hosts will need to be configured to point to the internal
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User name servers for DNS resolution.
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User </p>
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User<p>
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User Queries for internal hostnames will be answered by the internal
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User servers, and queries for external hostnames will be forwarded back
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User out to the DNS servers on the bastion hosts.
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User </p>
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User<p>
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User In order for all this to work properly, internal clients will
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User need to be configured to query <span class="emphasis"><em>only</em></span> the internal
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User name servers for DNS queries. This could also be enforced via
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User selective
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User filtering on the network.
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User </p>
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User<p>
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User If everything has been set properly, <span class="emphasis"><em>Example, Inc.</em></span>'s
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User internal clients will now be able to:
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User </p>
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User<div class="itemizedlist"><ul type="disc">
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User<li>
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User Look up any hostnames in the <code class="literal">site1</code>
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User and
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User <code class="literal">site2.example.com</code> zones.
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User </li>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User<li>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User Look up any hostnames in the <code class="literal">site1.internal</code> and
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User <code class="literal">site2.internal</code> domains.
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User </li>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User<li>Look up any hostnames on the Internet.</li>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User<li>Exchange mail with both internal and external people.</li>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User</ul></div>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User<p>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User Hosts on the Internet will be able to:
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User </p>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User<div class="itemizedlist"><ul type="disc">
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User<li>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User Look up any hostnames in the <code class="literal">site1</code>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User and
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User <code class="literal">site2.example.com</code> zones.
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User </li>
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User<li>
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User Exchange mail with anyone in the <code class="literal">site1</code> and
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User <code class="literal">site2.example.com</code> zones.
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User </li>
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User</ul></div>
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User<p>
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User Here is an example configuration for the setup we just
666b453b37f9ccfe3c7984fb0b31b70a3ceb918fTinderbox User described above. Note that this is only configuration information;
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User for information on how to configure your zone files, see <a href="Bv9ARM.ch03.html#sample_configuration" title="Sample Configurations">the section called &#8220;Sample Configurations&#8221;</a>.
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User </p>
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User<p>
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User Internal DNS server config:
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User </p>
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User<pre class="programlisting">
266afc085a8a74f4b13cb150234a4db21f65278bTinderbox User
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox Useracl internals { 172.16.72.0/24; 192.168.1.0/24; };
bea02a4cc08d57b9f36979906f291ac78a99060aTinderbox User
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox Useracl externals { <code class="varname">bastion-ips-go-here</code>; };
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox Useroptions {
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User ...
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User ...
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt forward only;
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User // forward to external servers
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt forwarders {
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt <code class="varname">bastion-ips-go-here</code>;
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User };
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt // sample allow-transfer (no one)
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User allow-transfer { none; };
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User // restrict query access
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt allow-query { internals; externals; };
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt // restrict recursion
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User allow-recursion { internals; };
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User ...
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt ...
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt};
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User// sample master zone
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntzone "site1.example.com" {
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User type master;
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt file "m/site1.example.com";
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User // do normal iterative resolution (do not forward)
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein forwarders { };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-query { internals; externals; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-transfer { internals; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein};
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein// sample slave zone
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinzone "site2.example.com" {
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews type slave;
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews file "s/site2.example.com";
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein masters { 172.16.72.3; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein forwarders { };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-query { internals; externals; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-transfer { internals; };
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User};
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinzone "site1.internal" {
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein type master;
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein file "m/site1.internal";
350e5eecadfc5ee72b11b2cc46828c9a0bcd717cTinderbox User forwarders { };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-query { internals; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-transfer { internals; }
};
zone "site2.internal" {
type slave;
file "s/site2.internal";
masters { 172.16.72.3; };
forwarders { };
allow-query { internals };
allow-transfer { internals; }
};
</pre>
<p>
External (bastion host) DNS server config:
</p>
<pre class="programlisting">
acl internals { 172.16.72.0/24; 192.168.1.0/24; };
acl externals { bastion-ips-go-here; };
options {
...
...
// sample allow-transfer (no one)
allow-transfer { none; };
// default query access
allow-query { any; };
// restrict cache access
allow-query-cache { internals; externals; };
// restrict recursion
allow-recursion { internals; externals; };
...
...
};
// sample slave zone
zone "site1.example.com" {
type master;
file "m/site1.foo.com";
allow-transfer { internals; externals; };
};
zone "site2.example.com" {
type slave;
file "s/site2.foo.com";
masters { another_bastion_host_maybe; };
allow-transfer { internals; externals; }
};
</pre>
<p>
In the <code class="filename">resolv.conf</code> (or equivalent) on
the bastion host(s):
</p>
<pre class="programlisting">
search ...
nameserver 172.16.72.2
nameserver 172.16.72.3
nameserver 172.16.72.4
</pre>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="tsig"></a>TSIG</h2></div></div></div>
<p>
This is a short guide to setting up Transaction SIGnatures
(TSIG) based transaction security in <acronym class="acronym">BIND</acronym>. It describes changes
to the configuration file as well as what changes are required for
different features, including the process of creating transaction
keys and using transaction signatures with <acronym class="acronym">BIND</acronym>.
</p>
<p>
<acronym class="acronym">BIND</acronym> primarily supports TSIG for server
to server communication.
This includes zone transfer, notify, and recursive query messages.
Resolvers based on newer versions of <acronym class="acronym">BIND</acronym> 8 have limited support
for TSIG.
</p>
<p>
TSIG can also be useful for dynamic update. A primary
server for a dynamic zone should control access to the dynamic
update service, but IP-based access control is insufficient.
The cryptographic access control provided by TSIG
is far superior. The <span><strong class="command">nsupdate</strong></span>
program supports TSIG via the <code class="option">-k</code> and
<code class="option">-y</code> command line options or inline by use
of the <span><strong class="command">key</strong></span>.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571028"></a>Generate Shared Keys for Each Pair of Hosts</h3></div></div></div>
<p>
A shared secret is generated to be shared between <span class="emphasis"><em>host1</em></span> and <span class="emphasis"><em>host2</em></span>.
An arbitrary key name is chosen: "host1-host2.". The key name must
be the same on both hosts.
</p>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2571045"></a>Automatic Generation</h4></div></div></div>
<p>
The following command will generate a 128-bit (16 byte) HMAC-MD5
key as described above. Longer keys are better, but shorter keys
are easier to read. Note that the maximum key length is 512 bits;
keys longer than that will be digested with MD5 to produce a
128-bit key.
</p>
<p>
<strong class="userinput"><code>dnssec-keygen -a hmac-md5 -b 128 -n HOST host1-host2.</code></strong>
</p>
<p>
The key is in the file <code class="filename">Khost1-host2.+157+00000.private</code>.
Nothing directly uses this file, but the base-64 encoded string
following "<code class="literal">Key:</code>"
can be extracted from the file and used as a shared secret:
</p>
<pre class="programlisting">Key: La/E5CjG9O+os1jq0a2jdA==</pre>
<p>
The string "<code class="literal">La/E5CjG9O+os1jq0a2jdA==</code>" can
be used as the shared secret.
</p>
</div>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2571083"></a>Manual Generation</h4></div></div></div>
<p>
The shared secret is simply a random sequence of bits, encoded
in base-64. Most ASCII strings are valid base-64 strings (assuming
the length is a multiple of 4 and only valid characters are used),
so the shared secret can be manually generated.
</p>
<p>
Also, a known string can be run through <span><strong class="command">mmencode</strong></span> or
a similar program to generate base-64 encoded data.
</p>
</div>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571101"></a>Copying the Shared Secret to Both Machines</h3></div></div></div>
<p>
This is beyond the scope of DNS. A secure transport mechanism
should be used. This could be secure FTP, ssh, telephone, etc.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571112"></a>Informing the Servers of the Key's Existence</h3></div></div></div>
<p>
Imagine <span class="emphasis"><em>host1</em></span> and <span class="emphasis"><em>host 2</em></span>
are
both servers. The following is added to each server's <code class="filename">named.conf</code> file:
</p>
<pre class="programlisting">
key host1-host2. {
algorithm hmac-md5;
secret "La/E5CjG9O+os1jq0a2jdA==";
};
</pre>
<p>
The algorithm, <code class="literal">hmac-md5</code>, is the only one supported by <acronym class="acronym">BIND</acronym>.
The secret is the one generated above. Since this is a secret, it
is recommended that either <code class="filename">named.conf</code> be non-world
readable, or the key directive be added to a non-world readable
file that is included by
<code class="filename">named.conf</code>.
</p>
<p>
At this point, the key is recognized. This means that if the
server receives a message signed by this key, it can verify the
signature. If the signature is successfully verified, the
response is signed by the same key.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571155"></a>Instructing the Server to Use the Key</h3></div></div></div>
<p>
Since keys are shared between two hosts only, the server must
be told when keys are to be used. The following is added to the <code class="filename">named.conf</code> file
for <span class="emphasis"><em>host1</em></span>, if the IP address of <span class="emphasis"><em>host2</em></span> is
10.1.2.3:
</p>
<pre class="programlisting">
server 10.1.2.3 {
keys { host1-host2. ;};
};
</pre>
<p>
Multiple keys may be present, but only the first is used.
This directive does not contain any secrets, so it may be in a
world-readable
file.
</p>
<p>
If <span class="emphasis"><em>host1</em></span> sends a message that is a request
to that address, the message will be signed with the specified key. <span class="emphasis"><em>host1</em></span> will
expect any responses to signed messages to be signed with the same
key.
</p>
<p>
A similar statement must be present in <span class="emphasis"><em>host2</em></span>'s
configuration file (with <span class="emphasis"><em>host1</em></span>'s address) for <span class="emphasis"><em>host2</em></span> to
sign request messages to <span class="emphasis"><em>host1</em></span>.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571281"></a>TSIG Key Based Access Control</h3></div></div></div>
<p>
<acronym class="acronym">BIND</acronym> allows IP addresses and ranges
to be specified in ACL
definitions and
<span><strong class="command">allow-{ query | transfer | update }</strong></span>
directives.
This has been extended to allow TSIG keys also. The above key would
be denoted <span><strong class="command">key host1-host2.</strong></span>
</p>
<p>
An example of an <span><strong class="command">allow-update</strong></span> directive would be:
</p>
<pre class="programlisting">
allow-update { key host1-host2. ;};
</pre>
<p>
This allows dynamic updates to succeed only if the request
was signed by a key named "<span><strong class="command">host1-host2.</strong></span>".
</p>
<p>
See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a> for a discussion of
the more flexible <span><strong class="command">update-policy</strong></span> statement.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571330"></a>Errors</h3></div></div></div>
<p>
The processing of TSIG signed messages can result in
several errors. If a signed message is sent to a non-TSIG aware
server, a FORMERR (format error) will be returned, since the server will not
understand the record. This is a result of misconfiguration,
since the server must be explicitly configured to send a TSIG
signed message to a specific server.
</p>
<p>
If a TSIG aware server receives a message signed by an
unknown key, the response will be unsigned with the TSIG
extended error code set to BADKEY. If a TSIG aware server
receives a message with a signature that does not validate, the
response will be unsigned with the TSIG extended error code set
to BADSIG. If a TSIG aware server receives a message with a time
outside of the allowed range, the response will be signed with
the TSIG extended error code set to BADTIME, and the time values
will be adjusted so that the response can be successfully
verified. In any of these cases, the message's rcode (response code) is set to
NOTAUTH (not authenticated).
</p>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2571412"></a>TKEY</h2></div></div></div>
<p><span><strong class="command">TKEY</strong></span>
is a mechanism for automatically generating a shared secret
between two hosts. There are several "modes" of
<span><strong class="command">TKEY</strong></span> that specify how the key is generated
or assigned. <acronym class="acronym">BIND</acronym> 9 implements only one of
these modes, the Diffie-Hellman key exchange. Both hosts are
required to have a Diffie-Hellman KEY record (although this
record is not required to be present in a zone). The
<span><strong class="command">TKEY</strong></span> process must use signed messages,
signed either by TSIG or SIG(0). The result of
<span><strong class="command">TKEY</strong></span> is a shared secret that can be used to
sign messages with TSIG. <span><strong class="command">TKEY</strong></span> can also be
used to delete shared secrets that it had previously
generated.
</p>
<p>
The <span><strong class="command">TKEY</strong></span> process is initiated by a
client
or server by sending a signed <span><strong class="command">TKEY</strong></span>
query
(including any appropriate KEYs) to a TKEY-aware server. The
server response, if it indicates success, will contain a
<span><strong class="command">TKEY</strong></span> record and any appropriate keys.
After
this exchange, both participants have enough information to
determine the shared secret; the exact process depends on the
<span><strong class="command">TKEY</strong></span> mode. When using the
Diffie-Hellman
<span><strong class="command">TKEY</strong></span> mode, Diffie-Hellman keys are
exchanged,
and the shared secret is derived by both participants.
</p>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2571461"></a>SIG(0)</h2></div></div></div>
<p>
<acronym class="acronym">BIND</acronym> 9 partially supports DNSSEC SIG(0)
transaction signatures as specified in RFC 2535 and RFC 2931.
SIG(0)
uses public/private keys to authenticate messages. Access control
is performed in the same manner as TSIG keys; privileges can be
granted or denied based on the key name.
</p>
<p>
When a SIG(0) signed message is received, it will only be
verified if the key is known and trusted by the server; the server
will not attempt to locate and/or validate the key.
</p>
<p>
SIG(0) signing of multiple-message TCP streams is not
supported.
</p>
<p>
The only tool shipped with <acronym class="acronym">BIND</acronym> 9 that
generates SIG(0) signed messages is <span><strong class="command">nsupdate</strong></span>.
</p>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="DNSSEC"></a>DNSSEC</h2></div></div></div>
<p>
Cryptographic authentication of DNS information is possible
through the DNS Security (<span class="emphasis"><em>DNSSEC-bis</em></span>) extensions,
defined in RFC 4033, RFC 4034, and RFC 4035.
This section describes the creation and use of DNSSEC signed zones.
</p>
<p>
In order to set up a DNSSEC secure zone, there are a series
of steps which must be followed. <acronym class="acronym">BIND</acronym>
9 ships
with several tools
that are used in this process, which are explained in more detail
below. In all cases, the <code class="option">-h</code> option prints a
full list of parameters. Note that the DNSSEC tools require the
keyset files to be in the working directory or the
directory specified by the <code class="option">-d</code> option, and
that the tools shipped with BIND 9.2.x and earlier are not compatible
with the current ones.
</p>
<p>
There must also be communication with the administrators of
the parent and/or child zone to transmit keys. A zone's security
status must be indicated by the parent zone for a DNSSEC capable
resolver to trust its data. This is done through the presence
or absence of a <code class="literal">DS</code> record at the
delegation
point.
</p>
<p>
For other servers to trust data in this zone, they must
either be statically configured with this zone's zone key or the
zone key of another zone above this one in the DNS tree.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571666"></a>Generating Keys</h3></div></div></div>
<p>
The <span><strong class="command">dnssec-keygen</strong></span> program is used to
generate keys.
</p>
<p>
A secure zone must contain one or more zone keys. The
zone keys will sign all other records in the zone, as well as
the zone keys of any secure delegated zones. Zone keys must
have the same name as the zone, a name type of
<span><strong class="command">ZONE</strong></span>, and must be usable for
authentication.
It is recommended that zone keys use a cryptographic algorithm
designated as "mandatory to implement" by the IETF; currently
the only one is RSASHA1.
</p>
<p>
The following command will generate a 768-bit RSASHA1 key for
the <code class="filename">child.example</code> zone:
</p>
<p>
<strong class="userinput"><code>dnssec-keygen -a RSASHA1 -b 768 -n ZONE child.example.</code></strong>
</p>
<p>
Two output files will be produced:
<code class="filename">Kchild.example.+005+12345.key</code> and
<code class="filename">Kchild.example.+005+12345.private</code>
(where
12345 is an example of a key tag). The key filenames contain
the key name (<code class="filename">child.example.</code>),
algorithm (3
is DSA, 1 is RSAMD5, 5 is RSASHA1, etc.), and the key tag (12345 in
this case).
The private key (in the <code class="filename">.private</code>
file) is
used to generate signatures, and the public key (in the
<code class="filename">.key</code> file) is used for signature
verification.
</p>
<p>
To generate another key with the same properties (but with
a different key tag), repeat the above command.
</p>
<p>
The <span><strong class="command">dnssec-keyfromlabel</strong></span> program is used
to get a key pair from a crypto hardware and build the key
files. Its usage is similar to <span><strong class="command">dnssec-keygen</strong></span>.
</p>
<p>
The public keys should be inserted into the zone file by
including the <code class="filename">.key</code> files using
<span><strong class="command">$INCLUDE</strong></span> statements.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571813"></a>Signing the Zone</h3></div></div></div>
<p>
The <span><strong class="command">dnssec-signzone</strong></span> program is used
to sign a zone.
</p>
<p>
Any <code class="filename">keyset</code> files corresponding to
secure subzones should be present. The zone signer will
generate <code class="literal">NSEC</code>, <code class="literal">NSEC3</code>
and <code class="literal">RRSIG</code> records for the zone, as
well as <code class="literal">DS</code> for the child zones if
<code class="literal">'-g'</code> is specified. If <code class="literal">'-g'</code>
is not specified, then DS RRsets for the secure child
zones need to be added manually.
</p>
<p>
The following command signs the zone, assuming it is in a
file called <code class="filename">zone.child.example</code>. By
default, all zone keys which have an available private key are
used to generate signatures.
</p>
<p>
<strong class="userinput"><code>dnssec-signzone -o child.example zone.child.example</code></strong>
</p>
<p>
One output file is produced:
<code class="filename">zone.child.example.signed</code>. This
file
should be referenced by <code class="filename">named.conf</code>
as the
input file for the zone.
</p>
<p><span><strong class="command">dnssec-signzone</strong></span>
will also produce a keyset and dsset files and optionally a
dlvset file. These are used to provide the parent zone
administrators with the <code class="literal">DNSKEYs</code> (or their
corresponding <code class="literal">DS</code> records) that are the
secure entry point to the zone.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571894"></a>Configuring Servers</h3></div></div></div>
<p>
To enable <span><strong class="command">named</strong></span> to respond appropriately
to DNS requests from DNSSEC aware clients,
<span><strong class="command">dnssec-enable</strong></span> must be set to yes.
(This is the default setting.)
</p>
<p>
To enable <span><strong class="command">named</strong></span> to validate answers from
other servers, the <span><strong class="command">dnssec-enable</strong></span> and
<span><strong class="command">dnssec-validation</strong></span> options must both be
set to yes (the default setting in <acronym class="acronym">BIND</acronym> 9.5
and later), and at least one trust anchor must be configured
with a <span><strong class="command">trusted-keys</strong></span> statement in
<code class="filename">named.conf</code>.
</p>
<p>
<span><strong class="command">trusted-keys</strong></span> are copies of DNSKEY RRs
for zones that are used to form the first link in the
cryptographic chain of trust. All keys listed in
<span><strong class="command">trusted-keys</strong></span> (and corresponding zones)
are deemed to exist and only the listed keys will be used
to validated the DNSKEY RRset that they are from.
</p>
<p>
<span><strong class="command">trusted-keys</strong></span> are described in more detail
later in this document.
</p>
<p>
Unlike <acronym class="acronym">BIND</acronym> 8, <acronym class="acronym">BIND</acronym>
9 does not verify signatures on load, so zone keys for
authoritative zones do not need to be specified in the
configuration file.
</p>
<p>
After DNSSEC gets established, a typical DNSSEC configuration
will look something like the following. It has one or
more public keys for the root. This allows answers from
outside the organization to be validated. It will also
have several keys for parts of the namespace the organization
controls. These are here to ensure that <span><strong class="command">named</strong></span> is immune
to compromises in the DNSSEC components of the security
of parent zones.
</p>
<pre class="programlisting">
trusted-keys {
/* Root Key */
"." 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
JxrGkxJWoZu6I7PzJu/E9gx4UC1zGAHlXKdE4zYIpRh
aBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3zy2Xy
4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYg
hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M/lUUVRbke
g1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq
66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
97S+LKUTpQcq27R7AT3/V5hRQxScINqwcz4jYqZD2fQ
dgxbcDTClU0CRBdiieyLMNzXG3";
/* Key for our organization's forward zone */
example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
kBOUKUf/mC7HvfwYH/Be22GnClrinKJp1O
g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
FxmAVZP20igTixin/1LcrgX/KMEGd/biuv
F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
/oyWR8BW/hWdzOvnSCThlHf3xiYleDbt/o
1OTQ09A0=";
/* Key for our reverse zone. */
2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwc
xOdNax071L18QqZnQQQAVVr+i
LhGTnNGp3HoWQLUIzKrJVZ3zg
gy3WwNT6kZo6c0tszYqbtvchm
gQC8CzKojM/W16i6MG/eafGU3
siaOdS0yOI6BgPsw+YZdzlYMa
IJGf4M4dyoKIhzdZyQ2bYQrjy
Q4LB0lC7aOnsMyYKHHYeRvPxj
IQXmdqgOJGq+vsevG06zW+1xg
YJh9rCIfnm1GX/KMgxLPG2vXT
D/RnLX+D3T3UL7HJYHJhAZD5L
59VvjSPsZJHeDCUyWYrvPZesZ
DIRvhDD52SKvbheeTJUm6Ehkz
ytNN2SN96QRk8j/iI8ib";
};
options {
...
dnssec-enable yes;
dnssec-validation yes;
};
</pre>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
None of the keys listed in this example are valid. In particular,
the root key is not valid.
</div>
<p>
When DNSSEC validation is enabled and properly configured,
the resolver will reject any answers from signed, secure zones
which fail to validate, and will return SERVFAIL to the client.
</p>
<p>
Responses may fail to validate for any of several reasons,
including missing, expired, or invalid signatures, a key which
does not match the DS RRset in the parent zone, or an insecure
response from a zone which, according to its parent, should have
been secure.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
When the validator receives a response from an unsigned zone
that has a signed parent, it must confirm with the parent
that the zone was intentionally left unsigned. It does
this by verifying, via signed and validated NSEC/NSEC3 records,
that the parent zone contains no DS records for the child.
</p>
<p>
If the validator <span class="emphasis"><em>can</em></span> prove that the zone
is insecure, then the response is accepted. However, if it
cannot, then it must assume an insecure response to be a
forgery; it rejects the response and logs an error.
</p>
<p>
The logged error reads "insecurity proof failed" and
"got insecure response; parent indicates it should be secure".
(Prior to BIND 9.7, the logged error was "not insecure".
This referred to the zone, not the response.)
</p>
</div>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2572064"></a>IPv6 Support in <acronym class="acronym">BIND</acronym> 9</h2></div></div></div>
<p>
<acronym class="acronym">BIND</acronym> 9 fully supports all currently
defined forms of IPv6 name to address and address to name
lookups. It will also use IPv6 addresses to make queries when
running on an IPv6 capable system.
</p>
<p>
For forward lookups, <acronym class="acronym">BIND</acronym> 9 supports
only AAAA records. RFC 3363 deprecated the use of A6 records,
and client-side support for A6 records was accordingly removed
from <acronym class="acronym">BIND</acronym> 9.
However, authoritative <acronym class="acronym">BIND</acronym> 9 name servers still
load zone files containing A6 records correctly, answer queries
for A6 records, and accept zone transfer for a zone containing A6
records.
</p>
<p>
For IPv6 reverse lookups, <acronym class="acronym">BIND</acronym> 9 supports
the traditional "nibble" format used in the
<span class="emphasis"><em>ip6.arpa</em></span> domain, as well as the older, deprecated
<span class="emphasis"><em>ip6.int</em></span> domain.
Older versions of <acronym class="acronym">BIND</acronym> 9
supported the "binary label" (also known as "bitstring") format,
but support of binary labels has been completely removed per
RFC 3363.
Many applications in <acronym class="acronym">BIND</acronym> 9 do not understand
the binary label format at all any more, and will return an
error if given.
In particular, an authoritative <acronym class="acronym">BIND</acronym> 9
name server will not load a zone file containing binary labels.
</p>
<p>
For an overview of the format and structure of IPv6 addresses,
see <a href="Bv9ARM.ch09.html#ipv6addresses" title="IPv6 addresses (AAAA)">the section called &#8220;IPv6 addresses (AAAA)&#8221;</a>.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2572262"></a>Address Lookups Using AAAA Records</h3></div></div></div>
<p>
The IPv6 AAAA record is a parallel to the IPv4 A record,
and, unlike the deprecated A6 record, specifies the entire
IPv6 address in a single record. For example,
</p>
<pre class="programlisting">
$ORIGIN example.com.
host 3600 IN AAAA 2001:db8::1
</pre>
<p>
Use of IPv4-in-IPv6 mapped addresses is not recommended.
If a host has an IPv4 address, use an A record, not
a AAAA, with <code class="literal">::ffff:192.168.42.1</code> as
the address.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2572283"></a>Address to Name Lookups Using Nibble Format</h3></div></div></div>
<p>
When looking up an address in nibble format, the address
components are simply reversed, just as in IPv4, and
<code class="literal">ip6.arpa.</code> is appended to the
resulting name.
For example, the following would provide reverse name lookup for
a host with address
<code class="literal">2001:db8::1</code>.
</p>
<pre class="programlisting">
$ORIGIN 0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa.
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
host.example.com. )
</pre>
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