Bv9ARM.ch04.html revision a1b05dea35aa30b152a47115e18bbe679d3fcf19
d6fa26d0adaec6c910115be34fe7a5a5f402c14fMark Andrews<!--
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - Copyright (C) 2004-2007 Internet Systems Consortium, Inc. ("ISC")
32098293b78922a5fbd10906afa28624820d3756Tinderbox User - Copyright (C) 2000-2003 Internet Software Consortium.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein -
5347c0fcb04eaea19d9f39795646239f487c6207Tinderbox User - Permission to use, copy, modify, and distribute this software for any
5347c0fcb04eaea19d9f39795646239f487c6207Tinderbox User - purpose with or without fee is hereby granted, provided that the above
5347c0fcb04eaea19d9f39795646239f487c6207Tinderbox User - copyright notice and this permission notice appear in all copies.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein -
d6fa26d0adaec6c910115be34fe7a5a5f402c14fMark Andrews - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein - PERFORMANCE OF THIS SOFTWARE.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein-->
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User<!-- $Id: Bv9ARM.ch04.html,v 1.76 2007/05/16 06:12:01 marka Exp $ -->
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<html>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<head>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<title>Chapter�4.�Advanced DNS Features</title>
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User<meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<link rel="start" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<link rel="up" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<link rel="prev" href="Bv9ARM.ch03.html" title="Chapter�3.�Name Server Configuration">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<link rel="next" href="Bv9ARM.ch05.html" title="Chapter�5.�The BIND 9 Lightweight Resolver">
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews</head>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<div class="navheader">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<table width="100%" summary="Navigation header">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<tr><th colspan="3" align="center">Chapter�4.�Advanced DNS Features</th></tr>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<tr>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<td width="20%" align="left">
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<a accesskey="p" href="Bv9ARM.ch03.html">Prev</a>�</td>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<th width="60%" align="center">�</th>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<td width="20%" align="right">�<a accesskey="n" href="Bv9ARM.ch05.html">Next</a>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</td>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User</tr>
0b89eee6167201843c9a46b7e7c63cb1e4e09ba3Tinderbox User</table>
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>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User<dl>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<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#id2570658">Split DNS</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2570676">Example split DNS setup</a></span></dt></dl></dd>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<dt><span class="sect1"><a href="Bv9ARM.ch04.html#tsig">TSIG</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dd><dl>
f9ce6280cec79deb16ff6d9807aa493ff23e10d9Tinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571111">Generate Shared Keys for Each Pair of Hosts</a></span></dt>
0b89eee6167201843c9a46b7e7c63cb1e4e09ba3Tinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571185">Copying the Shared Secret to Both Machines</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571264">Informing the Servers of the Key's Existence</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571303">Instructing the Server to Use the Key</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571429">TSIG Key Based Access Control</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571474">Errors</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User</dl></dd>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2571488">TKEY</a></span></dt>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2571673">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>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571741">Generating Keys</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571811">Signing the Zone</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571890">Configuring Servers</a></span></dt>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User</dl></dd>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2572033">IPv6 Support in <acronym class="acronym">BIND</acronym> 9</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dd><dl>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2572163">Address Lookups Using AAAA Records</a></span></dt>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2572184">Address to Name Lookups Using Nibble Format</a></span></dt>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User</dl></dd>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</dl>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</div>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<div class="sect1" lang="en">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<div class="titlepage"><div><div><h2 class="title" style="clear: both">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<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
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt servers to notify their slave servers of changes to a zone's data. In
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User 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
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox 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.
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User </p>
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox 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, named,
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User by default, sends <span><strong class="command">NOTIFY</strong></span> messages for every zone
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User it loads. Specifying <span><strong class="command">notify master-only;</strong></span> will
33c9436ef1a43d3c0fc3d9be9b4b0509daa83223Tinderbox User cause named 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.
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User Dynamic update is enabled by including an
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <span><strong class="command">allow-update</strong></span> or <span><strong class="command">update-policy</strong></span>
0da02c26a6631c25f075a8e4ac6de9e58f49a0c2Tinderbox User clause in the <span><strong class="command">zone</strong></span> statement. The
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <span><strong class="command">tkey-gssapi-credential</strong></span> and
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <span><strong class="command">tkey-domain</strong></span> clauses in the
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <span><strong class="command">options</strong></span> statement enable the
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User server to negotiate keys that can be matched against those
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User in <span><strong class="command">update-policy</strong></span> or
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User <span><strong class="command">allow-update</strong></span>.
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User </p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Updating of secure zones (zones using DNSSEC) follows
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User RFC 3007: RRSIG and NSEC records affected by updates are automatically
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User regenerated by the server using an online zone key.
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User Update authorization is based
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User on transaction signatures and an explicit server policy.
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User </p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<div class="sect2" lang="en">
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<div class="titlepage"><div><div><h3 class="title">
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<a name="journal"></a>The journal file</h3></div></div></div>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User<p>
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User All changes made to a zone using dynamic update are stored
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User in the zone's journal file. This file is automatically created
8a48b6b9b6fa8486f24b22d1972b2b6ebb36a4a4Tinderbox User by the server when the first dynamic update takes place.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The name of the journal file is formed by appending the extension
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="filename">.jnl</code> to the name of the
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User corresponding zone
a1ff871f78b7d907d6fc3a382beea2a640fe8423Tinderbox User file unless specifically overridden. The journal file is in a
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User binary format and should not be edited manually.
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User </p>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User<p>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User The server will also occasionally write ("dump")
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User the complete contents of the updated zone to its zone file.
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User This is not done immediately after
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User each dynamic update, because that would be too slow when a large
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User zone is updated frequently. Instead, the dump is delayed by
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User up to 15 minutes, allowing additional updates to take place.
363b21045b718d06d414784c96193dc9a233e8c5Tinderbox User </p>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User When a server is restarted after a shutdown or crash, it will replay
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User the journal file to incorporate into the zone any updates that
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User took
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User place after the last zone dump.
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User </p>
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User<p>
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User Changes that result from incoming incremental zone transfers are
550d3276d0490c4918f089ccb1528a3eb0951b0aTinderbox User also
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User journalled in a similar way.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox 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
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox 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
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User is up to date is to run <span><strong class="command">rndc stop</strong></span>.
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User </p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User<p>
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User If you have to make changes to a dynamic zone
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User manually, the following procedure will work: Disable dynamic updates
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User to the zone using
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User <span><strong class="command">rndc freeze <em class="replaceable"><code>zone</code></em></strong></span>.
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User This will also remove the zone's <code class="filename">.jnl</code> file
51da15c88648a9e47d0cddff4b2b782665e99401Tinderbox User and update the master file. Edit the zone file. Run
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox 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>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</div>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User</div>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User<div class="sect1" lang="en">
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User<div class="titlepage"><div><div><h2 class="title" style="clear: both">
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User<a name="incremental_zone_transfers"></a>Incremental Zone Transfers (IXFR)</h2></div></div></div>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User<p>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User The incremental zone transfer (IXFR) protocol is a way for
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User slave servers to transfer only changed data, instead of having to
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User transfer the entire zone. The IXFR protocol is specified in RFC
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User 1995. See <a href="Bv9ARM.ch09.html#proposed_standards">Proposed Standards</a>.
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User </p>
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User<p>
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User When acting as a master, <acronym class="acronym">BIND</acronym> 9
bfb7b680bf88c1fdd9949197b71c512c532280a4Tinderbox User supports IXFR for those zones
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User where the necessary change history information is available. These
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User include master zones maintained by dynamic update and slave zones
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User whose data was obtained by IXFR. For manually maintained master
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User zones, and for slave zones obtained by performing a full zone
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User transfer (AXFR), IXFR is supported only if the option
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User <span><strong class="command">ixfr-from-differences</strong></span> is set
3ca1a32241189d1e02e59f6b56399eb9b40f2aafTinderbox User to <strong class="userinput"><code>yes</code></strong>.
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User </p>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox User<p>
dfae459e8c4f794f8a239e74aa9d5e11cce6ea5bTinderbox 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.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt </p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User</div>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<div class="sect1" lang="en">
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<div class="titlepage"><div><div><h2 class="title" style="clear: both">
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<a name="id2570658"></a>Split DNS</h2></div></div></div>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<p>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User Setting up different views, or visibility, of the DNS space to
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User internal and external resolvers is usually referred to as a
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User <span class="emphasis"><em>Split DNS</em></span> setup. There are several
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User reasons an organization would want to set up its DNS this way.
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User </p>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<p>
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User One common reason for setting up a DNS system this way is
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User to hide "internal" DNS information from "external" clients on the
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User Internet. There is some debate as to whether or not this is actually
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User useful.
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User Internal DNS information leaks out in many ways (via email headers,
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User for example) and most savvy "attackers" can find the information
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User they need using other means.
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox User However, since listing addresses of internal servers that
f14ce68ee54a5a4587fbde4ffacb117946df2d73Tinderbox 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
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User to the outside world.
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User </p>
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User<p>
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User Another common reason for setting up a Split DNS system is
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User to allow internal networks that are behind filters or in RFC 1918
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User space (reserved IP space, as documented in RFC 1918) to resolve DNS
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User on the Internet. Split DNS can also be used to allow mail from outside
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User back in to the internal network.
0d6a6642b2be93cffa651c54a9b8810dd2d31392Tinderbox User </p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<div class="sect2" lang="en">
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<div class="titlepage"><div><div><h3 class="title">
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<a name="id2570676"></a>Example split DNS setup</h3></div></div></div>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User Let's say a company named <span class="emphasis"><em>Example, Inc.</em></span>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User (<code class="literal">example.com</code>)
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User has several corporate sites that have an internal network with
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User reserved
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox 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.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User<p>
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User <span class="emphasis"><em>Example, Inc.</em></span> wants its internal clients
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User to be able to resolve external hostnames and to exchange mail with
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User people on the outside. The company also wants its internal resolvers
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User to have access to certain internal-only zones that are not available
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User at all outside of the internal network.
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User<p>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User In order to accomplish this, the company will set up two sets
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User of name servers. One set will be on the inside network (in the
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User reserved
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User IP space) and the other set will be on bastion hosts, which are
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User "proxy"
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User hosts that can talk to both sides of its network, in the DMZ.
abe69df9a7de5cda07a2b8e19e8b7c981bcd7a9dTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User The internal servers will be configured to forward all queries,
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User except queries for <code class="filename">site1.internal</code>, <code class="filename">site2.internal</code>, <code class="filename">site1.example.com</code>,
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt and <code class="filename">site2.example.com</code>, to the servers
164ade1482251e1da962b42e5bf0d3aa02a11e03Tinderbox User in the
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User DMZ. These internal servers will have complete sets of information
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User for <code class="filename">site1.example.com</code>, <code class="filename">site2.example.com</code>,<span class="emphasis"><em></em></span> <code class="filename">site1.internal</code>,
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User and <code class="filename">site2.internal</code>.
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User </p>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User<p>
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User To protect the <code class="filename">site1.internal</code> and <code class="filename">site2.internal</code> domains,
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User the internal name servers must be configured to disallow all queries
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User to these domains from any external hosts, including the bastion
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User hosts.
a0fb6a0980359165a4459723f52d5d7b5725f9c6Tinderbox User </p>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User<p>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User The external servers, which are on the bastion hosts, will
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User be configured to serve the "public" version of the <code class="filename">site1</code> and <code class="filename">site2.example.com</code> zones.
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User This could include things such as the host records for public servers
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User (<code class="filename">www.example.com</code> and <code class="filename">ftp.example.com</code>),
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User and mail exchange (MX) records (<code class="filename">a.mx.example.com</code> and <code class="filename">b.mx.example.com</code>).
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User </p>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User<p>
8c7245514646663b25d8b186186ebede41903fa3Tinderbox User In addition, the public <code class="filename">site1</code> and <code class="filename">site2.example.com</code> zones
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User should have special MX records that contain wildcard (`*') records
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User pointing to the bastion hosts. This is needed because external mail
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User servers do not have any other way of looking up how to deliver mail
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User to those internal hosts. With the wildcard records, the mail will
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User be delivered to the bastion host, which can then forward it on to
421ba11f3f07cbcb12c288ef7f4e7bad13fcc28fTinderbox User internal hosts.
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User </p>
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User<p>
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User Here's an example of a wildcard MX record:
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User </p>
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User<pre class="programlisting">* IN MX 10 external1.example.com.</pre>
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User<p>
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User Now that they accept mail on behalf of anything in the internal
3b15473cedf41d48904f5b07bdc5e87afff6b58cTinderbox User network, the bastion hosts will need to know how to deliver mail
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User to internal hosts. In order for this to work properly, the resolvers
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User on
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User the bastion hosts will need to be configured to point to the internal
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User name servers for DNS resolution.
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User </p>
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User<p>
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User Queries for internal hostnames will be answered by the internal
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User servers, and queries for external hostnames will be forwarded back
99b30e26a6beb9092557cc9e5370b517309bff6eTinderbox User out to the DNS servers on the bastion hosts.
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User </p>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User<p>
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User In order for all this to work properly, internal clients will
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User need to be configured to query <span class="emphasis"><em>only</em></span> the internal
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User name servers for DNS queries. This could also be enforced via
c48fdfda7a8ae8973aadfeb88cbeaab013024a6cTinderbox User selective
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User filtering on the network.
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User </p>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User<p>
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User If everything has been set properly, <span class="emphasis"><em>Example, Inc.</em></span>'s
9efd8fc7e811d3c0c160adeb5552c2df7e49df67Tinderbox User internal clients will now 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.
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User </li>
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User<li>
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User Look up any hostnames in the <code class="literal">site1.internal</code> and
ffe29868b4bbc64953fc5d0de51f988c20158967Tinderbox User <code class="literal">site2.internal</code> domains.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt </li>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<li>Look up any hostnames on the Internet.</li>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<li>Exchange mail with both internal and external people.</li>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt</ul></div>
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User<p>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt Hosts on the Internet will be able to:
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User </p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User<div class="itemizedlist"><ul type="disc">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<li>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt Look up any hostnames in the <code class="literal">site1</code>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User and
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User <code class="literal">site2.example.com</code> zones.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt </li>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<li>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt Exchange mail with anyone in the <code class="literal">site1</code> and
fd2597f75693a2279fdf588bd40dfe2407c42028Tinderbox User <code class="literal">site2.example.com</code> zones.
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt </li>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User</ul></div>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt<p>
7911e6f9de303bca5a3d8b34f4330c8f7cecffaeTinderbox User Here is an example configuration for the setup we just
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein described above. Note that this is only configuration information;
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein 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>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Internal DNS server config:
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein </p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<pre class="programlisting">
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrewsacl internals { 172.16.72.0/24; 192.168.1.0/24; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinacl externals { <code class="varname">bastion-ips-go-here</code>; };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinoptions {
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User ...
cd32f419a8a5432fbb139f56ee73cbf68b9350ccTinderbox User ...
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein forward only;
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein forwarders { // forward to external servers
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="varname">bastion-ips-go-here</code>;
0b89eee6167201843c9a46b7e7c63cb1e4e09ba3Tinderbox User };
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-transfer { none; }; // sample allow-transfer (no one)
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein allow-query { internals; externals; }; // restrict query access
allow-recursion { internals; }; // restrict recursion
...
...
};
zone "site1.example.com" { // sample master zone
type master;
file "m/site1.example.com";
forwarders { }; // do normal iterative
// resolution (do not forward)
allow-query { internals; externals; };
allow-transfer { internals; };
};
zone "site2.example.com" { // sample slave zone
type slave;
file "s/site2.example.com";
masters { 172.16.72.3; };
forwarders { };
allow-query { internals; externals; };
allow-transfer { internals; };
};
zone "site1.internal" {
type master;
file "m/site1.internal";
forwarders { };
allow-query { internals; };
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 {
...
...
allow-transfer { none; }; // sample allow-transfer (no one)
allow-query { any; }; // default query access
allow-query-cache { internals; externals; }; // restrict cache access
allow-recursion { internals; externals; }; // restrict recursion
...
...
};
zone "site1.example.com" { // sample slave zone
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="id2571111"></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="id2571128"></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="id2571166"></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="id2571185"></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="id2571264"></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, hmac-md5, 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="id2571303"></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="id2571429"></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 allow-update 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>
You may want to read about the more powerful
<span><strong class="command">update-policy</strong></span> statement in
<a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571474"></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="id2571488"></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="id2571673"></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 RFC2931.
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="id2571741"></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 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="id2571811"></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> 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">'-d'</code> is specified.
If <code class="literal">'-d'</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="id2571890"></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.
</p>
<p>
To enable <span><strong class="command">named</strong></span> to validate answers from
other servers both <span><strong class="command">dnssec-enable</strong></span> and
<span><strong class="command">dnssec-validate</strong></span> must be set and some
<span><strong class="command">trusted-keys</strong></span> must be configured
into <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 a 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 named 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+CXd0rVXyYmobt7sEEfK3clRbGaTwSJxrGkxJWoZu6I7PzJu/
E9gx4UC1zGAHlXKdE4zYIpRhaBKnvcC2U9mZhkdUpd1Vso/HAdjNe8LmMlnzY3
zy2Xy4klWOADTPzSv9eamj8V18PHGjBLaVtYvk/ln5ZApjYghf+6fElrmLkdaz
MQ2OCnACR817DF4BBa7UR/beDHyp5iWTXWSi6XmoJLbG9Scqc7l70KDqlvXR3M
/lUUVRbkeg1IPJSidmK3ZyCllh4XSKbje/45SKucHgnwU5jefMtq66gKodQj+M
iA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ97S+LKUTpQcq27R7AT3/V5hRQxScI
Nqwcz4jYqZD2fQdgxbcDTClU0CRBdiieyLMNzXG3";
/* Key for our organization's forward zone */
example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM65KbhTjrW1ZaARmPhEZZe
3Y9ifgEuq7vZ/zGZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb4JKUbb
OTcM8pwXlj0EiX3oDFVmjHO444gLkBO UKUf/mC7HvfwYH/Be22GnC
lrinKJp1Og4ywzO9WglMk7jbfW33gUKvirTHr25GL7STQUzBb5Usxt
8lgnyTUHs1t3JwCY5hKZ6CqFxmAVZP20igTixin/1LcrgX/KMEGd/b
iuvF4qJCyduieHukuY3H4XMAcR+xia2 nIUPvm/oyWR8BW/hWdzOvn
SCThlHf3xiYleDbt/o1OTQ09A0=";
/* Key for our reverse zone. */
2.0.192.IN-ADDRPA.NET. 257 3 5 "AQOnS4xn/IgOUpBPJ3bogzwcxOdNax071L18QqZnQQQA
VVr+iLhGTnNGp3HoWQLUIzKrJVZ3zggy3WwNT6kZo6c0
tszYqbtvchmgQC8CzKojM/W16i6MG/ea fGU3siaOdS0
yOI6BgPsw+YZdzlYMaIJGf4M4dyoKIhzdZyQ2bYQrjyQ
4LB0lC7aOnsMyYKHHYeRv PxjIQXmdqgOJGq+vsevG06
zW+1xgYJh9rCIfnm1GX/KMgxLPG2vXTD/RnLX+D3T3UL
7HJYHJhAZD5L59VvjSPsZJHeDCUyWYrvPZesZDIRvhDD
52SKvbheeTJUm6EhkzytNN2SN96QRk8j/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>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2572033"></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="id2572163"></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="id2572184"></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>
</div>
</div>
</div>
<div class="navfooter">
<hr>
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left">
<a accesskey="p" href="Bv9ARM.ch03.html">Prev</a>�</td>
<td width="20%" align="center">�</td>
<td width="40%" align="right">�<a accesskey="n" href="Bv9ARM.ch05.html">Next</a>
</td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Chapter�3.�Name Server Configuration�</td>
<td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
<td width="40%" align="right" valign="top">�Chapter�5.�The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver</td>
</tr>
</table>
</div>
</body>
</html>