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<tr><th colspan="3" align="center">Chapter�4.�Advanced DNS Features</th></tr>
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<div class="chapter" lang="en">
<div class="titlepage"><div><div><h2 class="title">
<div class="toc">
<p><b>Table of Contents</b></p>
<dl>
<dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch04.html#journal">The journal file</a></span></dt></dl></dd>
<dt><span class="sect1"><a href="Bv9ARM.ch04.html#incremental_zone_transfers">Incremental Zone Transfers (IXFR)</a></span></dt>
<dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2564053">Example split DNS setup</a></span></dt></dl></dd>
<dd><dl>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571722">Generate Shared Keys for Each Pair of Hosts</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571796">Copying the Shared Secret to Both Machines</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571806">Informing the Servers of the Key's Existence</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2571979">Instructing the Server to Use the Key</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2572105">TSIG Key Based Access Control</a></span></dt>
</dl></dd>
<dd><dl>
</dl></dd>
<dt><span class="sect1"><a href="Bv9ARM.ch04.html#dnssec.dynamic.zones">DNSSEC, Dynamic Zones, and Automatic Signing</a></span></dt>
<dd><dl>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2608619">Converting from insecure to secure</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2608657">Dynamic DNS update method</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563569">Fully automatic zone signing</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563790">Dynamic DNS update method</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563824">Automatic key rollovers</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563850">NSEC3PARAM rollovers via UPDATE</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563860">Converting from NSEC to NSEC3</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563869">Converting from NSEC3 to NSEC</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2563882">Converting from secure to insecure</a></span></dt>
</dl></dd>
<dt><span class="sect1"><a href="Bv9ARM.ch04.html#rfc5011.support">Dynamic Trust Anchor Management</a></span></dt>
<dd><dl>
</dl></dd>
<dt><span class="sect1"><a href="Bv9ARM.ch04.html#pkcs11">PKCS #11 (Cryptoki) support</a></span></dt>
<dd><dl>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2608878">Building BIND 9 with PKCS#11</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2611660">Specifying the engine on the command line</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2611706">Running named with automatic zone re-signing</a></span></dt>
</dl></dd>
<dt><span class="sect1"><a href="Bv9ARM.ch04.html#id2572802">IPv6 Support in <acronym class="acronym">BIND</acronym> 9</a></span></dt>
<dd><dl>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2573068">Address Lookups Using AAAA Records</a></span></dt>
<dt><span class="sect2"><a href="Bv9ARM.ch04.html#id2573090">Address to Name Lookups Using Nibble Format</a></span></dt>
</dl></dd>
</dl>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="notify"></a>Notify</h2></div></div></div>
<p>
<acronym class="acronym">DNS</acronym> NOTIFY is a mechanism that allows master
servers to notify their slave servers of changes to a zone's data. In
response to a <span><strong class="command">NOTIFY</strong></span> from a master server, the
slave will check to see that its version of the zone is the
current version and, if not, initiate a zone transfer.
</p>
<p>
For more information about <acronym class="acronym">DNS</acronym>
<span><strong class="command">NOTIFY</strong></span>, see the description of the
<span><strong class="command">notify</strong></span> option in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</a> and
the description of the zone option <span><strong class="command">also-notify</strong></span> in
<a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</a>. The <span><strong class="command">NOTIFY</strong></span>
protocol is specified in RFC 1996.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
As a slave zone can also be a master to other slaves, <span><strong class="command">named</strong></span>,
by default, sends <span><strong class="command">NOTIFY</strong></span> messages for every zone
it loads. Specifying <span><strong class="command">notify master-only;</strong></span> will
cause <span><strong class="command">named</strong></span> to only send <span><strong class="command">NOTIFY</strong></span> for master
zones that it loads.
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="dynamic_update"></a>Dynamic Update</h2></div></div></div>
<p>
Dynamic Update is a method for adding, replacing or deleting
records in a master server by sending it a special form of DNS
messages. The format and meaning of these messages is specified
in RFC 2136.
</p>
<p>
Dynamic update is enabled by including an
<span><strong class="command">allow-update</strong></span> or an <span><strong class="command">update-policy</strong></span>
clause in the <span><strong class="command">zone</strong></span> statement.
</p>
<p>
If the zone's <span><strong class="command">update-policy</strong></span> is set to
<strong class="userinput"><code>local</code></strong>, updates to the zone
will be permitted for the key <code class="varname">local-ddns</code>,
which will be generated by <span><strong class="command">named</strong></span> at startup.
See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called “Dynamic Update Policies”</a> for more details.
</p>
<p>
Dynamic updates using Kerberos signed requests can be made
<span><strong class="command">tkey-gssapi-keytab</strong></span> option, or alternatively
by setting both the <span><strong class="command">tkey-gssapi-credential</strong></span>
and <span><strong class="command">tkey-domain</strong></span> options. Once enabled,
Kerberos signed requests will be matched against the update
policies for the zone, using the Kerberos principal as the
signer for the request.
</p>
<p>
Updating of secure zones (zones using DNSSEC) follows RFC
3007: RRSIG, NSEC and NSEC3 records affected by updates are
automatically regenerated by the server using an online
zone key. Update authorization is based on transaction
signatures and an explicit server policy.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="journal"></a>The journal file</h3></div></div></div>
<p>
All changes made to a zone using dynamic update are stored
in the zone's journal file. This file is automatically created
by the server when the first dynamic update takes place.
The name of the journal file is formed by appending the extension
<code class="filename">.jnl</code> to the name of the
corresponding zone
file unless specifically overridden. The journal file is in a
binary format and should not be edited manually.
</p>
<p>
The server will also occasionally write ("dump")
the complete contents of the updated zone to its zone file.
This is not done immediately after
each dynamic update, because that would be too slow when a large
zone is updated frequently. Instead, the dump is delayed by
up to 15 minutes, allowing additional updates to take place.
During the dump process, transient files will be created
with the extensions <code class="filename">.jnw</code> and
<code class="filename">.jbk</code>; under ordinary circumstances, these
will be removed when the dump is complete, and can be safely
ignored.
</p>
<p>
When a server is restarted after a shutdown or crash, it will replay
the journal file to incorporate into the zone any updates that
took
place after the last zone dump.
</p>
<p>
Changes that result from incoming incremental zone transfers are
also
journalled in a similar way.
</p>
<p>
The zone files of dynamic zones cannot normally be edited by
hand because they are not guaranteed to contain the most recent
dynamic changes — those are only in the journal file.
The only way to ensure that the zone file of a dynamic zone
is up to date is to run <span><strong class="command">rndc stop</strong></span>.
</p>
<p>
If you have to make changes to a dynamic zone
manually, the following procedure will work: Disable dynamic updates
to the zone using
<span><strong class="command">rndc freeze <em class="replaceable"><code>zone</code></em></strong></span>.
This will also remove the zone's <code class="filename">.jnl</code> file
and update the master file. Edit the zone file. Run
<span><strong class="command">rndc thaw <em class="replaceable"><code>zone</code></em></strong></span>
to reload the changed zone and re-enable dynamic updates.
</p>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="incremental_zone_transfers"></a>Incremental Zone Transfers (IXFR)</h2></div></div></div>
<p>
The incremental zone transfer (IXFR) protocol is a way for
slave servers to transfer only changed data, instead of having to
transfer the entire zone. The IXFR protocol is specified in RFC
</p>
<p>
When acting as a master, <acronym class="acronym">BIND</acronym> 9
supports IXFR for those zones
where the necessary change history information is available. These
include master zones maintained by dynamic update and slave zones
whose data was obtained by IXFR. For manually maintained master
zones, and for slave zones obtained by performing a full zone
transfer (AXFR), IXFR is supported only if the option
<span><strong class="command">ixfr-from-differences</strong></span> is set
to <strong class="userinput"><code>yes</code></strong>.
</p>
<p>
When acting as a slave, <acronym class="acronym">BIND</acronym> 9 will
attempt to use IXFR unless
it is explicitly disabled. For more information about disabling
IXFR, see the description of the <span><strong class="command">request-ixfr</strong></span> clause
of the <span><strong class="command">server</strong></span> statement.
</p>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2564035"></a>Split DNS</h2></div></div></div>
<p>
Setting up different views, or visibility, of the DNS space to
internal and external resolvers is usually referred to as a
<span class="emphasis"><em>Split DNS</em></span> setup. There are several
reasons an organization would want to set up its DNS this way.
</p>
<p>
One common reason for setting up a DNS system this way is
to hide "internal" DNS information from "external" clients on the
Internet. There is some debate as to whether or not this is actually
useful.
Internal DNS information leaks out in many ways (via email headers,
for example) and most savvy "attackers" can find the information
they need using other means.
However, since listing addresses of internal servers that
external clients cannot possibly reach can result in
connection delays and other annoyances, an organization may
choose to use a Split DNS to present a consistent view of itself
to the outside world.
</p>
<p>
Another common reason for setting up a Split DNS system is
to allow internal networks that are behind filters or in RFC 1918
space (reserved IP space, as documented in RFC 1918) to resolve DNS
on the Internet. Split DNS can also be used to allow mail from outside
back in to the internal network.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2564053"></a>Example split DNS setup</h3></div></div></div>
<p>
Let's say a company named <span class="emphasis"><em>Example, Inc.</em></span>
has several corporate sites that have an internal network with
reserved
Internet Protocol (IP) space and an external demilitarized zone (DMZ),
or "outside" section of a network, that is available to the public.
</p>
<p>
<span class="emphasis"><em>Example, Inc.</em></span> wants its internal clients
to be able to resolve external hostnames and to exchange mail with
people on the outside. The company also wants its internal resolvers
to have access to certain internal-only zones that are not available
at all outside of the internal network.
</p>
<p>
In order to accomplish this, the company will set up two sets
of name servers. One set will be on the inside network (in the
reserved
IP space) and the other set will be on bastion hosts, which are
"proxy"
hosts that can talk to both sides of its network, in the DMZ.
</p>
<p>
The internal servers will be configured to forward all queries,
except queries for <code class="filename">site1.internal</code>, <code class="filename">site2.internal</code>, <code class="filename">site1.example.com</code>,
in the
DMZ. These internal servers will have complete sets of information
for <code class="filename">site1.example.com</code>, <code class="filename">site2.example.com</code>, <code class="filename">site1.internal</code>,
</p>
<p>
To protect the <code class="filename">site1.internal</code> and <code class="filename">site2.internal</code> domains,
the internal name servers must be configured to disallow all queries
to these domains from any external hosts, including the bastion
hosts.
</p>
<p>
The external servers, which are on the bastion hosts, will
be configured to serve the "public" version of the <code class="filename">site1</code> and <code class="filename">site2.example.com</code> zones.
This could include things such as the host records for public servers
and mail exchange (MX) records (<code class="filename">a.mx.example.com</code> and <code class="filename">b.mx.example.com</code>).
</p>
<p>
In addition, the public <code class="filename">site1</code> and <code class="filename">site2.example.com</code> zones
should have special MX records that contain wildcard (`*') records
pointing to the bastion hosts. This is needed because external mail
servers do not have any other way of looking up how to deliver mail
to those internal hosts. With the wildcard records, the mail will
be delivered to the bastion host, which can then forward it on to
internal hosts.
</p>
<p>
Here's an example of a wildcard MX record:
</p>
<p>
Now that they accept mail on behalf of anything in the internal
network, the bastion hosts will need to know how to deliver mail
to internal hosts. In order for this to work properly, the resolvers
on
the bastion hosts will need to be configured to point to the internal
name servers for DNS resolution.
</p>
<p>
Queries for internal hostnames will be answered by the internal
servers, and queries for external hostnames will be forwarded back
out to the DNS servers on the bastion hosts.
</p>
<p>
In order for all this to work properly, internal clients will
need to be configured to query <span class="emphasis"><em>only</em></span> the internal
name servers for DNS queries. This could also be enforced via
selective
filtering on the network.
</p>
<p>
If everything has been set properly, <span class="emphasis"><em>Example, Inc.</em></span>'s
internal clients will now be able to:
</p>
<div class="itemizedlist"><ul type="disc">
<li>
Look up any hostnames in the <code class="literal">site1</code>
and
</li>
<li>
</li>
<li>Look up any hostnames on the Internet.</li>
<li>Exchange mail with both internal and external people.</li>
</ul></div>
<p>
Hosts on the Internet will be able to:
</p>
<div class="itemizedlist"><ul type="disc">
<li>
Look up any hostnames in the <code class="literal">site1</code>
and
</li>
<li>
Exchange mail with anyone in the <code class="literal">site1</code> and
</li>
</ul></div>
<p>
Here is an example configuration for the setup we just
described above. Note that this is only configuration information;
for information on how to configure your zone files, see <a href="Bv9ARM.ch03.html#sample_configuration" title="Sample Configurations">the section called “Sample Configurations”</a>.
</p>
<p>
Internal DNS server config:
</p>
<pre class="programlisting">
acl externals { <code class="varname">bastion-ips-go-here</code>; };
options {
...
...
forward only;
// forward to external servers
forwarders {
<code class="varname">bastion-ips-go-here</code>;
};
// sample allow-transfer (no one)
allow-transfer { none; };
// restrict query access
allow-query { internals; externals; };
// restrict recursion
allow-recursion { internals; };
...
...
};
// sample master zone
zone "site1.example.com" {
type master;
file "m/site1.example.com";
// do normal iterative resolution (do not forward)
forwarders { };
allow-query { internals; externals; };
allow-transfer { internals; };
};
// sample slave zone
zone "site2.example.com" {
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 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>
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="id2571722"></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="id2571739"></a>Automatic Generation</h4></div></div></div>
<p>
The following command will generate a 128-bit (16 byte) HMAC-SHA256
key as described above. Longer keys are better, but shorter keys
are easier to read. Note that the maximum key length is the digest
length, here 256 bits.
</p>
<p>
<strong class="userinput"><code>dnssec-keygen -a hmac-sha256 -b 128 -n HOST host1-host2.</code></strong>
</p>
<p>
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>
<p>
be used as the shared secret.
</p>
</div>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2571778"></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="id2571796"></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="id2571806"></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-sha256;
};
</pre>
<p>
The secret is the one generated above. Since this is a secret, it
non-world readable, or the key directive be added to a non-world
</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="id2571979"></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="id2572105"></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 “Dynamic Update Policies”</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="id2572154"></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="id2572168"></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="id2572217"></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)
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
</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
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="id2572354"></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
</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:
(where
12345 is an example of a key tag). The key filenames contain
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="id2572433"></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
default, all zone keys which have an available private key are
used to generate signatures.
</p>
<p>
</p>
<p>
One output file is produced:
file
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="id2572582"></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> option
must be set to <strong class="userinput"><code>yes</code></strong>, and the
<span><strong class="command">dnssec-validation</strong></span> options must be set to
<strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>auto</code></strong>.
</p>
<p>
If <span><strong class="command">dnssec-validation</strong></span> is set to
<strong class="userinput"><code>auto</code></strong>, then a default
trust anchor for the DNS root zone will be used.
If it is set to <strong class="userinput"><code>yes</code></strong>, however,
then at least one trust anchor must be configured
with a <span><strong class="command">trusted-keys</strong></span> or
<span><strong class="command">managed-keys</strong></span> statement in
will not occur. The default setting is
<strong class="userinput"><code>yes</code></strong>.
</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">managed-keys</strong></span> are trusted keys which are
automatically kept up to date via RFC 5011 trust anchor
maintenance.
</p>
<p>
<span><strong class="command">trusted-keys</strong></span> and
<span><strong class="command">managed-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">
managed-keys {
/* Root Key */
"." initial-key 257 3 3 "BNY4wrWM1nCfJ+CXd0rVXyYmobt7sEEfK3clRbGaTwS
hf+6fElrmLkdaz MQ2OCnACR817DF4BBa7UR/beDHyp
66gKodQj+MiA21AfUVe7u99WzTLzY3qlxDhxYQQ20FQ
dgxbcDTClU0CRBdiieyLMNzXG3";
};
trusted-keys {
/* Key for our organization's forward zone */
example.com. 257 3 5 "AwEAAaxPMcR2x0HbQV4WeZB6oEDX+r0QM6
5KbhTjrW1ZaARmPhEZZe3Y9ifgEuq7vZ/z
GZUdEGNWy+JZzus0lUptwgjGwhUS1558Hb
4JKUbbOTcM8pwXlj0EiX3oDFVmjHO444gL
g4ywzO9WglMk7jbfW33gUKvirTHr25GL7S
TQUzBb5Usxt8lgnyTUHs1t3JwCY5hKZ6Cq
F4qJCyduieHukuY3H4XMAcR+xia2nIUPvm
1OTQ09A0=";
/* Key for our reverse zone. */
xOdNax071L18QqZnQQQAVVr+i
LhGTnNGp3HoWQLUIzKrJVZ3zg
gy3WwNT6kZo6c0tszYqbtvchm
siaOdS0yOI6BgPsw+YZdzlYMa
IJGf4M4dyoKIhzdZyQ2bYQrjy
Q4LB0lC7aOnsMyYKHHYeRvPxj
IQXmdqgOJGq+vsevG06zW+1xg
59VvjSPsZJHeDCUyWYrvPZesZ
DIRvhDD52SKvbheeTJUm6Ehkz
};
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
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="dnssec.dynamic.zones"></a>DNSSEC, Dynamic Zones, and Automatic Signing</h2></div></div></div>
<p>As of BIND 9.7.0 it is possible to change a dynamic zone
from insecure to signed and back again. A secure zone can use
either NSEC or NSEC3 chains.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2608619"></a>Converting from insecure to secure</h3></div></div></div></div>
<p>Changing a zone from insecure to secure can be done in two
ways: using a dynamic DNS update, or the
<span><strong class="command">auto-dnssec</strong></span> zone option.</p>
<p>For either method, you need to configure
<span><strong class="command">named</strong></span> so that it can see the
<code class="filename">K*</code> files which contain the public and private
parts of the keys that will be used to sign the zone. These files
will have been generated by
<span><strong class="command">dnssec-keygen</strong></span>. You can do this by placing them
in the key-directory, as specified in
<pre class="programlisting">
zone example.net {
type master;
update-policy local;
key-directory "dynamic/example.net";
};
</pre>
<p>If one KSK and one ZSK DNSKEY key have been generated, this
configuration will cause all records in the zone to be signed
with the ZSK, and the DNSKEY RRset to be signed with the KSK as
well. An NSEC chain will be generated as part of the initial
signing process.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2608657"></a>Dynamic DNS update method</h3></div></div></div></div>
<p>To insert the keys via dynamic update:</p>
<pre class="screen">
% nsupdate
> ttl 3600
> update add example.net DNSKEY 256 3 7 AwEAAZn17pUF0KpbPA2c7Gz76Vb18v0teKT3EyAGfBfL8eQ8al35zz3Y I1m/SAQBxIqMfLtIwqWPdgthsu36azGQAX8=
> update add example.net DNSKEY 257 3 7 AwEAAd/7odU/64o2LGsifbLtQmtO8dFDtTAZXSX2+X3e/UNlq9IHq3Y0 XtC0Iuawl/qkaKVxXe2lo8Ct+dM6UehyCqk=
> send
</pre>
<p>While the update request will complete almost immediately,
the zone will not be completely signed until
<span><strong class="command">named</strong></span> has had time to walk the zone and
generate the NSEC and RRSIG records. The NSEC record at the apex
will be added last, to signal that there is a complete NSEC
chain.</p>
<p>If you wish to sign using NSEC3 instead of NSEC, you should
add an NSEC3PARAM record to the initial update request. If you
wish the NSEC3 chain to have the OPTOUT bit set, set it in the
flags field of the NSEC3PARAM record.</p>
<pre class="screen">
% nsupdate
> ttl 3600
> update add example.net DNSKEY 256 3 7 AwEAAZn17pUF0KpbPA2c7Gz76Vb18v0teKT3EyAGfBfL8eQ8al35zz3Y I1m/SAQBxIqMfLtIwqWPdgthsu36azGQAX8=
> update add example.net DNSKEY 257 3 7 AwEAAd/7odU/64o2LGsifbLtQmtO8dFDtTAZXSX2+X3e/UNlq9IHq3Y0 XtC0Iuawl/qkaKVxXe2lo8Ct+dM6UehyCqk=
> update add example.net NSEC3PARAM 1 1 100 1234567890
> send
</pre>
<p>Again, this update request will complete almost
immediately; however, the record won't show up until
relevant chain. A private type record will be created to record
the state of the operation (see below for more details), and will
be removed once the operation completes.</p>
is happening, other updates are possible as well.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563569"></a>Fully automatic zone signing</h3></div></div></div></div>
<p>To enable automatic signing, add the
<span><strong class="command">auto-dnssec</strong></span> option to the zone statement in
<span><strong class="command">auto-dnssec</strong></span> has two possible arguments:
<code class="constant">allow</code> or
<code class="constant">maintain</code>.</p>
<p>With
<span><strong class="command">auto-dnssec allow</strong></span>,
<span><strong class="command">named</strong></span> can search the key directory for keys
matching the zone, insert them into the zone, and use them to
sign the zone. It will do so only when it receives an
<span><strong class="command">rndc sign <zonename></strong></span>.</p>
<p>
<span><strong class="command">auto-dnssec maintain</strong></span> includes the above
functionality, but will also automatically adjust the zone's
DNSKEY records on schedule according to the keys' timing metadata.
(See <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
<a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a> for more information.)
</p>
<p>
<span><strong class="command">named</strong></span> will periodically search the key directory
for keys matching the zone, and if the keys' metadata indicates
that any change should be made the zone, such as adding, removing,
or revoking a key, then that action will be carried out. By default,
the key directory is checked for changes every 60 minutes; this period
can be adjusted with the <code class="option">dnssec-loadkeys-interval</code>, up
to a maximum of 24 hours. The <span><strong class="command">rndc loadkeys</strong></span> forces
<span><strong class="command">named</strong></span> to check for key updates immediately.
</p>
<p>
If keys are present in the key directory the first time the zone
is loaded, the zone will be signed immediately, without waiting for an
<span><strong class="command">rndc sign</strong></span> or <span><strong class="command">rndc loadkeys</strong></span>
command. (Those commands can still be used when there are unscheduled
key changes, however.)
</p>
<p>
If you wish the zone to be signed using NSEC3 instead of NSEC,
submit an NSEC3PARAM record via dynamic update prior to the
scheduled publication and activation of the keys. If you wish the
NSEC3 chain to have the OPTOUT bit set, set it in the flags field
of the NSEC3PARAM record. The NSEC3PARAM record will not appear in
the zone immediately, but it will be stored for later reference. When
the zone is signed and the NSEC3 chain is completed, the NSEC3PARAM
record will appear in the zone.
</p>
<p>Using the
<span><strong class="command">auto-dnssec</strong></span> option requires the zone to be
configured to allow dynamic updates, by adding an
<span><strong class="command">allow-update</strong></span> or
<span><strong class="command">update-policy</strong></span> statement to the zone
configuration. If this has not been done, the configuration will
fail.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563740"></a>Private-type records</h3></div></div></div></div>
<p>The state of the signing process is signaled by
private-type records (with a default type value of 65534). When
signing is complete, these records will have a nonzero value for
the final octet (for those records which have a nonzero initial
octet).</p>
<p>The private type record format: If the first octet is
non-zero then the record indicates that the zone needs to be
signed with the key matching the record, or that all signatures
that match the record should be removed.</p>
<p>
</p>
<div class="literallayout"><p><br>
<br>
��algorithm�(octet�1)<br>
��key�id�in�network�order�(octet�2�and�3)<br>
��removal�flag�(octet�4)<br>
��complete�flag�(octet�5)<br>
</p></div>
<p>
</p>
<p>Only records flagged as "complete" can be removed via
dynamic update. Attempts to remove other private type records
will be silently ignored.</p>
<p>If the first octet is zero (this is a reserved algorithm
number that should never appear in a DNSKEY record) then the
record indicates changes to the NSEC3 chains are in progress. The
rest of the record contains an NSEC3PARAM record. The flag field
tells what operation to perform based on the flag bits.</p>
<p>
</p>
<div class="literallayout"><p><br>
<br>
��0x01�OPTOUT<br>
��0x80�CREATE<br>
��0x40�REMOVE<br>
��0x20�NONSEC<br>
</p></div>
<p>
</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563778"></a>DNSKEY rollovers</h3></div></div></div></div>
<p>As with insecure-to-secure conversions, rolling DNSSEC
keys can be done in two ways: using a dynamic DNS update, or the
<span><strong class="command">auto-dnssec</strong></span> zone option.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563790"></a>Dynamic DNS update method</h3></div></div></div></div>
<p> To perform key rollovers via dynamic update, you need to add
the <code class="filename">K*</code> files for the new keys so that
<span><strong class="command">named</strong></span> can find them. You can then add the new
DNSKEY RRs via dynamic update.
<span><strong class="command">named</strong></span> will then cause the zone to be signed
with the new keys. When the signing is complete the private type
records will be updated so that the last octet is non
zero.</p>
<p>If this is for a KSK you need to inform the parent and any
trust anchor repositories of the new KSK.</p>
<p>You should then wait for the maximum TTL in the zone before
removing the old DNSKEY. If it is a KSK that is being updated,
you also need to wait for the DS RRset in the parent to be
updated and its TTL to expire. This ensures that all clients will
be able to verify at least one signature when you remove the old
DNSKEY.</p>
<p>The old DNSKEY can be removed via UPDATE. Take care to
specify the correct key.
<span><strong class="command">named</strong></span> will clean out any signatures generated
by the old key after the update completes.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563824"></a>Automatic key rollovers</h3></div></div></div></div>
<p>When a new key reaches its activation date (as set by
<span><strong class="command">dnssec-keygen</strong></span> or <span><strong class="command">dnssec-settime</strong></span>),
if the <span><strong class="command">auto-dnssec</strong></span> zone option is set to
<code class="constant">maintain</code>, <span><strong class="command">named</strong></span> will
automatically carry out the key rollover. If the key's algorithm
has not previously been used to sign the zone, then the zone will
be fully signed as quickly as possible. However, if the new key
is replacing an existing key of the same algorithm, then the
zone will be re-signed incrementally, with signatures from the
old key being replaced with signatures from the new key as their
signature validity periods expire. By default, this rollover
completes in 30 days, after which it will be safe to remove the
old key from the DNSKEY RRset.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563850"></a>NSEC3PARAM rollovers via UPDATE</h3></div></div></div></div>
<p>Add the new NSEC3PARAM record via dynamic update. When the
new NSEC3 chain has been generated, the NSEC3PARAM flag field
will be zero. At this point you can remove the old NSEC3PARAM
record. The old chain will be removed after the update request
completes.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563860"></a>Converting from NSEC to NSEC3</h3></div></div></div></div>
<p>To do this, you just need to add an NSEC3PARAM record. When
the conversion is complete, the NSEC chain will have been removed
and the NSEC3PARAM record will have a zero flag field. The NSEC3
chain will be generated before the NSEC chain is
destroyed.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563869"></a>Converting from NSEC3 to NSEC</h3></div></div></div></div>
<p>To do this, use <span><strong class="command">nsupdate</strong></span> to
remove all NSEC3PARAM records with a zero flag
field. The NSEC chain will be generated before the NSEC3 chain is
removed.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2563882"></a>Converting from secure to insecure</h3></div></div></div></div>
<p>To convert a signed zone to unsigned using dynamic DNS,
delete all the DNSKEY records from the zone apex using
<span><strong class="command">nsupdate</strong></span>. All signatures, NSEC or NSEC3 chains,
and associated NSEC3PARAM records will be removed automatically.
This will take place after the update request completes.</p>
<p> This requires the
<span><strong class="command">dnssec-secure-to-insecure</strong></span> option to be set to
<strong class="userinput"><code>yes</code></strong> in
<p>In addition, if the <span><strong class="command">auto-dnssec maintain</strong></span>
zone statement is used, it should be removed or changed to
<span><strong class="command">allow</strong></span> instead (or it will re-sign).
</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2571224"></a>Periodic re-signing</h3></div></div></div></div>
<p>In any secure zone which supports dynamic updates, named
will periodically re-sign RRsets which have not been re-signed as
a result of some update action. The signature lifetimes will be
adjusted so as to spread the re-sign load over time rather than
all at once.</p>
<div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title">
<a name="id2571234"></a>NSEC3 and OPTOUT</h3></div></div></div></div>
<p>
<span><strong class="command">named</strong></span> only supports creating new NSEC3 chains
where all the NSEC3 records in the zone have the same OPTOUT
state.
<span><strong class="command">named</strong></span> supports UPDATES to zones where the NSEC3
records in the chain have mixed OPTOUT state.
<span><strong class="command">named</strong></span> does not support changing the OPTOUT
state of an individual NSEC3 record, the entire chain needs to be
changed if the OPTOUT state of an individual NSEC3 needs to be
changed.</p>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<p>BIND 9.7.0 introduces support for RFC 5011, dynamic trust
anchor management. Using this feature allows
<span><strong class="command">named</strong></span> to keep track of changes to critical
DNSSEC keys without any need for the operator to make changes to
configuration files.</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571266"></a>Validating Resolver</h3></div></div></div>
<p>To configure a validating resolver to use RFC 5011 to
maintain a trust anchor, configure the trust anchor using a
<span><strong class="command">managed-keys</strong></span> statement. Information about
this can be found in
and Usage">the section called “<span><strong class="command">managed-keys</strong></span> Statement Definition
and Usage”</a>.</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2571288"></a>Authoritative Server</h3></div></div></div>
<p>To set up an authoritative zone for RFC 5011 trust anchor
maintenance, generate two (or more) key signing keys (KSKs) for
the zone. Sign the zone with one of them; this is the "active"
KSK. All KSK's which do not sign the zone are "stand-by"
keys.</p>
<p>Any validating resolver which is configured to use the
active KSK as an RFC 5011-managed trust anchor will take note
of the stand-by KSKs in the zone's DNSKEY RRset, and store them
for future reference. The resolver will recheck the zone
periodically, and after 30 days, if the new key is still there,
then the key will be accepted by the resolver as a valid trust
anchor for the zone. Any time after this 30-day acceptance
timer has completed, the active KSK can be revoked, and the
zone can be "rolled over" to the newly accepted key.</p>
<p>The easiest way to place a stand-by key in a zone is to
use the "smart signing" features of
<span><strong class="command">dnssec-keygen</strong></span> and
<span><strong class="command">dnssec-signzone</strong></span>. If a key with a publication
date in the past, but an activation date which is unset or in
the future, "
<span><strong class="command">dnssec-signzone -S</strong></span>" will include the DNSKEY
record in the zone, but will not sign with it:</p>
<pre class="screen">
$ <strong class="userinput"><code>dnssec-keygen -K keys -f KSK -P now -A now+2y example.net</code></strong>
</pre>
<p>To revoke a key, the new command
<span><strong class="command">dnssec-revoke</strong></span> has been added. This adds the
REVOKED bit to the key flags and re-generates the
<code class="filename">K*.key</code> and
<code class="filename">K*.private</code> files.</p>
<p>After revoking the active key, the zone must be signed
with both the revoked KSK and the new active KSK. (Smart
signing takes care of this automatically.)</p>
<p>Once a key has been revoked and used to sign the DNSKEY
RRset in which it appears, that key will never again be
accepted as a valid trust anchor by the resolver. However,
validation can proceed using the new active key (which had been
accepted by the resolver when it was a stand-by key).</p>
<p>See RFC 5011 for more details on key rollover
scenarios.</p>
<p>When a key has been revoked, its key ID changes,
increasing by 128, and wrapping around at 65535. So, for
<p>If two keys have ID's exactly 128 apart, and one is
revoked, then the two key ID's will collide, causing several
problems. To prevent this,
<span><strong class="command">dnssec-keygen</strong></span> will not generate a new key if
another key is present which may collide. This checking will
only occur if the new keys are written to the same directory
which holds all other keys in use for that zone.</p>
<p>Older versions of BIND 9 did not have this precaution.
Exercise caution if using key revocation on keys that were
generated by previous releases, or if using keys stored in
multiple directories or on multiple machines.</p>
<p>It is expected that a future release of BIND 9 will
address this problem in a different way, by storing revoked
keys with their original unrevoked key ID's.</p>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="pkcs11"></a>PKCS #11 (Cryptoki) support</h2></div></div></div>
<p>PKCS #11 (Public Key Cryptography Standard #11) defines a
platform- independent API for the control of hardware security
modules (HSMs) and other cryptographic support devices.</p>
<p>BIND 9 is known to work with two HSMs: The Sun SCA 6000
cryptographic acceleration board, tested under Solaris x86, and
the AEP Keyper network-attached key storage device, tested with
Debian Linux, Solaris x86 and Windows Server 2003.</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2608266"></a>Prerequisites</h3></div></div></div>
<p>See the HSM vendor documentation for information about
installing, initializing, testing and troubleshooting the
HSM.</p>
<p>BIND 9 uses OpenSSL for cryptography, but stock OpenSSL
does not yet fully support PKCS #11. However, a PKCS #11 engine
for OpenSSL is available from the OpenSolaris project. It has
been modified by ISC to work with with BIND 9, and to provide
new features such as PIN management and key by
reference.</p>
<p>The patched OpenSSL depends on a "PKCS #11 provider".
This is a shared library object, providing a low-level PKCS #11
interface to the HSM hardware. It is dynamically loaded by
OpenSSL at runtime. The PKCS #11 provider comes from the HSM
vendor, and and is specific to the HSM to be controlled.</p>
<p>There are two "flavors" of PKCS #11 support provided by
the patched OpenSSL, one of which must be chosen at
configuration time. The correct choice depends on the HSM
hardware:</p>
<div class="itemizedlist"><ul type="disc">
<li><p>Use 'crypto-accelerator' with HSMs that have hardware
cryptographic acceleration features, such as the SCA 6000
board. This causes OpenSSL to run all supported
cryptographic operations in the HSM.</p></li>
<li><p>Use 'sign-only' with HSMs that are designed to
function primarily as secure key storage devices, but lack
hardware acceleration. These devices are highly secure, but
are not necessarily any faster at cryptography than the
system CPU — often, they are slower. It is therefore
most efficient to use them only for those cryptographic
functions that require access to the secured private key,
such as zone signing, and to use the system CPU for all
other computationally-intensive operations. The AEP Keyper
is an example of such a device.</p></li>
</ul></div>
<p>The modified OpenSSL code is included in the BIND 9.7.0
release, in the form of a context diff against the latest OpenSSL.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
The latest OpenSSL version at the time of the BIND release
is 0.9.8l.
ISC will provide an updated patch as new versions of OpenSSL
are released. The version number in the following examples
is expected to change.</div>
<p>
Before building BIND 9 with PKCS #11 support, it will be
necessary to build OpenSSL with this patch in place and inform
it of the path to the HSM-specific PKCS #11 provider
library.</p>
<p>Obtain OpenSSL 0.9.8l:</p>
<pre class="screen">
$ <strong class="userinput"><code>wget <a href="" target="_top">http://www.openssl.org/source/openssl-0.9.8l.tar.gz</a></code></strong>
</pre>
<p>Extract the tarball:</p>
<pre class="screen">
</pre>
<p>Apply the patch from the BIND 9 release:</p>
<pre class="screen">
$ <strong class="userinput"><code>patch -p1 -d openssl-0.9.8l \
</pre>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>(Note that the patch file may not be compatible with the
"patch" utility on all operating systems. You may need to
install GNU patch.)</div>
<p>When building OpenSSL, place it in a non-standard
location so that it does not interfere with OpenSSL libraries
elsewhere on the system. In the following examples, we choose
when we configure BIND 9.</p>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2608499"></a>Building OpenSSL for the AEP Keyper on Linux</h4></div></div></div>
<p>The AEP Keyper is a highly secure key storage device,
but does not provide hardware cryptographic acceleration. It
can carry out cryptographic operations, but it is probably
slower than your system's CPU. Therefore, we choose the
'sign-only' flavor when building OpenSSL.</p>
<p>The Keyper-specific PKCS #11 provider library is
delivered with the Keyper software. In this example, we place
<pre class="screen">
$ <strong class="userinput"><code>cp pkcs11.GCC4.0.2.so.4.05 /opt/pkcs11/usr/lib/libpkcs11.so</code></strong>
</pre>
<p>This library is only available for Linux as a 32-bit
binary. If we are compiling on a 64-bit Linux system, it is
necessary to force a 32-bit build, by specifying -m32 in the
build options.</p>
<p>Finally, the Keyper library requires threads, so we
must specify -pthread.</p>
<pre class="screen">
$ <strong class="userinput"><code>cd openssl-0.9.8l</code></strong>
--pk11-flavor=sign-only \
</pre>
<p>After configuring, run "<span><strong class="command">make</strong></span>"
and "<span><strong class="command">make test</strong></span>". If "<span><strong class="command">make
test</strong></span>" fails with "pthread_atfork() not found", you forgot to
add the -pthread above.</p>
</div>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2608705"></a>Building OpenSSL for the SCA 6000 on Solaris</h4></div></div></div>
<p>The SCA-6000 PKCS #11 provider is installed as a system
library, libpkcs11. It is a true crypto accelerator, up to 4
times faster than any CPU, so the flavor shall be
'crypto-accelerator'.</p>
<p>In this example, we are building on Solaris x86 on an
AMD64 system.</p>
<pre class="screen">
$ <strong class="userinput"><code>cd openssl-0.9.8l</code></strong>
--pk11-flavor=crypto-accelerator \
</pre>
<p>(For a 32-bit build, use "solaris-x86-cc" and
<p>After configuring, run
<span><strong class="command">make</strong></span> and
<span><strong class="command">make test</strong></span>.</p>
<p>Once you have built OpenSSL, run
that PKCS #11 support was compiled in correctly. The output
should be one of the following lines, depending on the flavor
selected:</p>
<pre class="screen">
(pkcs11) PKCS #11 engine support (sign only)
</pre>
<p>Or:</p>
<pre class="screen">
(pkcs11) PKCS #11 engine support (crypto accelerator)
</pre>
<p>Next, run
attempt to initialize the PKCS #11 engine. If it is able to
do so successfully, it will report
“<span class="quote"><code class="literal">[ available ]</code></span>”.</p>
<p>If the output is correct, run
"<span><strong class="command">make install</strong></span>" which will install the
modified OpenSSL suite to
</div>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2608878"></a>Building BIND 9 with PKCS#11</h3></div></div></div>
<p>When building BIND 9, the location of the custom-built
OpenSSL library must be specified via configure.</p>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2608887"></a>Configuring BIND 9 for Linux</h4></div></div></div>
<p>To link with the PKCS #11 provider, threads must be
enabled in the BIND 9 build.</p>
<p>The PKCS #11 library for the AEP Keyper is currently
only available as a 32-bit binary. If we are building on a
64-bit host, we must force a 32-bit build by adding "-m32" to
the CC options on the "configure" command line.</p>
<pre class="screen">
</pre>
</div>
<div class="sect3" lang="en">
<div class="titlepage"><div><div><h4 class="title">
<a name="id2608918"></a>Configuring BIND 9 for Solaris</h4></div></div></div>
<p>To link with the PKCS #11 provider, threads must be
enabled in the BIND 9 build.</p>
<pre class="screen">
</pre>
<p>(For a 32-bit build, omit CC="cc -xarch=amd64".)</p>
<p>If configure complains about OpenSSL not working, you
incorrectly specified the path to OpenSSL (it should be the
same as the --prefix argument to the OpenSSL
Configure).</p>
</div>
<p>After configuring, run
"<span><strong class="command">make</strong></span>",
"<span><strong class="command">make test</strong></span>" and
"<span><strong class="command">make install</strong></span>".</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2609110"></a>PKCS #11 Tools</h3></div></div></div>
<p>BIND 9 includes a minimal set of tools to operate the
HSM, including
<span><strong class="command">pkcs11-keygen</strong></span> to generate a new key pair
within the HSM,
<span><strong class="command">pkcs11-list</strong></span> to list objects currently
available, and
<span><strong class="command">pkcs11-destroy</strong></span> to remove objects.</p>
9 is configured with the --with-pkcs11 option. (NOTE: If
--with-pkcs11 is set to "yes", rather than to the path of the
PKCS #11 provider, then the tools will be built but the
provider will be left undefined. Use the -m option or the
PKCS11_PROVIDER environment variable to specify the path to the
provider.)</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2609141"></a>Using the HSM</h3></div></div></div>
<p>First, we must set up the runtime environment so the
OpenSSL and PKCS #11 libraries can be loaded:</p>
<pre class="screen">
$ <strong class="userinput"><code>export LD_LIBRARY_PATH=/opt/pkcs11/usr/lib:${LD_LIBRARY_PATH}</code></strong>
</pre>
<p>When operating an AEP Keyper, it is also necessary to
specify the location of the "machine" file, which stores
information about the Keyper for use by PKCS #11 provider
library. If the machine file is in
use:</p>
<pre class="screen">
$ <strong class="userinput"><code>export KEYPER_LIBRARY_PATH=/opt/Keyper/PKCS11Provider</code></strong>
</pre>
<p>These environment variables must be set whenever running
any tool that uses the HSM, including
<span><strong class="command">pkcs11-keygen</strong></span>,
<span><strong class="command">pkcs11-list</strong></span>,
<span><strong class="command">pkcs11-destroy</strong></span>,
<span><strong class="command">dnssec-keyfromlabel</strong></span>,
<span><strong class="command">dnssec-signzone</strong></span>,
<span><strong class="command">dnssec-keygen</strong></span>(which will use the HSM for
random number generation), and
<span><strong class="command">named</strong></span>.</p>
<p>We can now create and use keys in the HSM. In this case,
we will create a 2048 bit key and give it the label
"sample-ksk":</p>
<pre class="screen">
$ <strong class="userinput"><code>pkcs11-keygen -b 2048 -l sample-ksk</code></strong>
</pre>
<p>To confirm that the key exists:</p>
<pre class="screen">
$ <strong class="userinput"><code>pkcs11-list</code></strong>
Enter PIN:
object[0]: handle 2147483658 class 3 label[8] 'sample-ksk' id[0]
object[1]: handle 2147483657 class 2 label[8] 'sample-ksk' id[0]
</pre>
<p>Before using this key to sign a zone, we must create a
pair of BIND 9 key files. The "dnssec-keyfromlabel" utility
does this. In this case, we will be using the HSM key
"sample-ksk" as the key-signing key for "example.net":</p>
<pre class="screen">
$ <strong class="userinput"><code>dnssec-keyfromlabel -l sample-ksk -f KSK example.net</code></strong>
</pre>
<p>The resulting K*.key and K*.private files can now be used
to sign the zone. Unlike normal K* files, which contain both
public and private key data, these files will contain only the
public key data, plus an identifier for the private key which
remains stored within the HSM. The HSM handles signing with the
private key.</p>
<p>If you wish to generate a second key in the HSM for use
as a zone-signing key, follow the same procedure above, using a
different keylabel, a smaller key size, and omitting "-f KSK"
from the dnssec-keyfromlabel arguments:</p>
<pre class="screen">
$ <strong class="userinput"><code>pkcs11-keygen -b 1024 -l sample-zsk</code></strong>
</pre>
<p>Alternatively, you may prefer to generate a conventional
on-disk key, using dnssec-keygen:</p>
<pre class="screen">
</pre>
<p>This provides less security than an HSM key, but since
HSMs can be slow or cumbersome to use for security reasons, it
may be more efficient to reserve HSM keys for use in the less
frequent key-signing operation. The zone-signing key can be
rolled more frequently, if you wish, to compensate for a
reduction in key security.</p>
<p>Now you can sign the zone. (Note: If not using the -S
option to
<span><strong class="command">dnssec-signzone</strong></span>, it will be necessary to add
the contents of both
<code class="filename">K*.key</code> files to the zone master file before
signing it.)</p>
<pre class="screen">
Enter PIN:
Verifying the zone using the following algorithms:
NSEC3RSASHA1.
Zone signing complete:
Algorithm: NSEC3RSASHA1: ZSKs: 1, KSKs: 1 active, 0 revoked, 0 stand-by
</pre>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2611660"></a>Specifying the engine on the command line</h3></div></div></div>
<p>The OpenSSL engine can be specified in
<span><strong class="command">named</strong></span> and all of the BIND
<span><strong class="command">dnssec-*</strong></span> tools by using the "-E
<engine>" command line option. If BIND 9 is built with
the --with-pkcs11 option, this option defaults to "pkcs11".
Specifying the engine will generally not be necessary unless
for some reason you wish to use a different OpenSSL
engine.</p>
<p>If you wish to disable use of the "pkcs11" engine —
for troubleshooting purposes, or because the HSM is unavailable
— set the engine to the empty string. For example:</p>
<pre class="screen">
</pre>
<p>This causes
<span><strong class="command">dnssec-signzone</strong></span> to run as if it were compiled
without the --with-pkcs11 option.</p>
</div>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2611706"></a>Running named with automatic zone re-signing</h3></div></div></div>
<p>If you want
<span><strong class="command">named</strong></span> to dynamically re-sign zones using HSM
named must have access to the HSM PIN. This can be accomplished
by placing the PIN into the openssl.cnf file (in the above
examples,
<p>The location of the openssl.cnf file can be overridden by
setting the OPENSSL_CONF environment variable before running
named.</p>
<pre class="programlisting">
openssl_conf = openssl_def
[ openssl_def ]
engines = engine_section
[ engine_section ]
pkcs11 = pkcs11_section
[ pkcs11_section ]
PIN = <em class="replaceable"><code><PLACE PIN HERE></code></em>
</pre>
<p>This will also allow the dnssec-* tools to access the HSM
without PIN entry. (The pkcs11-* tools access the HSM directly,
not via OpenSSL, so a PIN will still be required to use
them.)</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Warning</h3>
<p>Placing the HSM's PIN in a text file in
this manner may reduce the security advantage of using an
HSM. Be sure this is what you want to do before configuring
OpenSSL in this way.</p>
</div>
</div>
</div>
<div class="sect1" lang="en">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="id2572802"></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
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 “IPv6 addresses (AAAA)”</a>.
</p>
<div class="sect2" lang="en">
<div class="titlepage"><div><div><h3 class="title">
<a name="id2573068"></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="id2573090"></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
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">
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0 14400 IN PTR (
</pre>
</div>
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