docs/157245: [PATCH] [RFC] Add a section about DNSSEC to the DNS chapter in the handbook
Niclas Zeising
niclas.zeising at gmail.com
Mon May 23 12:50:17 UTC 2011
The following reply was made to PR docs/157245; it has been noted by GNATS.
From: Niclas Zeising <niclas.zeising at gmail.com>
To: bug-followup at FreeBSD.org, niclas.zeising at gmail.com
Cc:
Subject: Re: docs/157245: [PATCH] [RFC] Add a section about DNSSEC to the
DNS chapter in the handbook
Date: Mon, 23 May 2011 14:46:30 +0200
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After comments from Doug Barton and more comments from Warren Block,
here is a further refined patch with some changes and spelling fixes.
It also contains the necessary changes to man-refs.ent.
Thank you for the help and review!
--
Niclas
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Index: en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml
===================================================================
RCS file: /home/ncvs/doc/en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml,v
retrieving revision 1.130
diff -u -d -r1.130 chapter.sgml
--- en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml 15 May 2011 20:41:30 -0000 1.130
+++ en_US.ISO8859-1/books/handbook/network-servers/chapter.sgml 23 May 2011 12:10:10 -0000
@@ -3872,6 +3872,325 @@
</sect2>
<sect2>
+ <title><acronym role="Doman Name Security Extensions">DNSSEC</acronym></title>
+ <indexterm>
+ <primary>BIND</primary>
+ <secondary>DNS security extensions</secondary>
+ </indexterm>
+
+ <para>Domain Name System Security Extensions, or
+ <acronym role="Domain Name Security Extensions">DNSSEC</acronym>
+ for short, is a suite of specifications to protect
+ resolving name servers from forged <acronym>DNS</acronym> data,
+ such as spoofed <acronym>DNS</acronym> records. By using digital
+ signatures, a resolver can verify the integrity of the record. Note
+ that <acronym role="Domain Name Security Extensions">DNSSEC</acronym>
+ only provides integrity via digitally signing the Resource Records
+ (<acronym role="Resource Record">RR</acronym>s). It provides neither
+ confidentiality nor protection against false end-user assumptions.
+ This means that it cannot protect against people going to
+ <hostid role="domainname">example.net</hostid> instead of
+ <hostid role="domainname">example.com</hostid>. The only
+ thing <acronym>DNSSEC</acronym> does is authenticate that the data
+ has not been compromised in transit.
+ The security of <acronym>DNS</acronym> is an important step in
+ securing the Internet in general. For more in-depth details of how
+ <acronym>DNSSEC</acronym> works, the relevant
+ <acronym>RFC</acronym>s are a good place to start. See the list in
+ <xref linkend="dns-read">.</para>
+
+ <para>The following sections will demonstrate how to enable
+ <acronym>DNSSEC</acronym> for an authoritative <acronym>DNS</acronym>
+ server and a recursive (or caching) <acronym>DNS</acronym> server
+ running <acronym>BIND</acronym> 9. While all versions of
+ <acronym>BIND</acronym> 9 support <acronym>DNSSEC</acronym>, it is
+ necessary to have at least version 9.6.2 in order to be able to use
+ the signed root zone when validating <acronym>DNS</acronym> queries.
+ This is because earlier versions lack the required algorithms to enable
+ validation using the root zone key. It is strongly recommended to use
+ the latest version of <acronym>BIND</acronym> 9.7 or later to take
+ advantage of automatic key updating for the root key, as well as other
+ features to automatically keep zones signed and signatures up to date.
+ Where configurations differ between 9.6.2 and 9.7 and later,
+ differences will be pointed out.</para>
+
+ <sect3>
+ <title>Recursive <acronym>DNS</acronym> server configuration</title>
+
+ <para>Enabling <acronym>DNSSEC</acronym> validation of queries
+ performed by a recursive <acronym>DNS</acronym> server requires a
+ few changes to <filename>named.conf</filename>. Before making these
+ changes the root zone key, or trust anchor, must be acquired.
+ Currently the root zone key is not available in a file format
+ <acronym>BIND</acronym> understands, so it has to be manually
+ converted into the proper format. The key itself can be obtained by
+ querying the root zone for it using <application>dig</application>.
+ By running
+ <screen>&prompt.user; <userinput>dig +multi +noall +answer DNSKEY . > root.dnskey</userinput></screen>
+ the key will end up in <filename>root.dnskey</filename>. The
+ contents should look something like this:</para>
+
+ <programlisting>. 93910 IN DNSKEY 257 3 8 (
+ AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQ
+ bSEW0O8gcCjFFVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh
+ /RStIoO8g0NfnfL2MTJRkxoXbfDaUeVPQuYEhg37NZWA
+ JQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaDX6RS6CXp
+ oY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3
+ LQpzW5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGO
+ Yl7OyQdXfZ57relSQageu+ipAdTTJ25AsRTAoub8ONGc
+ LmqrAmRLKBP1dfwhYB4N7knNnulqQxA+Uk1ihz0=
+ ) ; key id = 19036
+. 93910 IN DNSKEY 256 3 8 (
+ AwEAAcaGQEA+OJmOzfzVfoYN249JId7gx+OZMbxy69Hf
+ UyuGBbRN0+HuTOpBxxBCkNOL+EJB9qJxt+0FEY6ZUVjE
+ g58sRr4ZQ6Iu6b1xTBKgc193zUARk4mmQ/PPGxn7Cn5V
+ EGJ/1h6dNaiXuRHwR+7oWh7DnzkIJChcTqlFrXDW3tjt
+ ) ; key id = 34525</programlisting>
+
+ <para>Do not be alarmed if the obtained keys differ from this example.
+ They might have changed since these instructions were last updated.
+ This output actually contains two keys. The first key in the
+ listing, with the value 257 after the DNSKEY record type, is the one
+ needed. This value indicates that this is a Secure Entry Point
+ (<acronym role="Secure Entry Point">SEP</acronym>),
+ commonly known as a Key Signing Key
+ (<acronym role="Key Signing Key">KSK</acronym>). The second key,
+ with value 256, is a subordinate key, commonly called a Zone Signing
+ Key (<acronym role="Zone Signing Key">ZSK</acronym>). More on the
+ different key types later in the <xref linkend="dns-dnssec-auth">.
+ </para>
+
+ <para>Now the key must be verified and formatted so that
+ <acronym>BIND</acronym> can use it. To verify the key, generate a
+ <acronym role="Delegation Signer">DS</acronym>
+ <acronym role="Resource Record">RR</acronym> set. Create a file
+ containing these <acronym role="Resource Record">RR</acronym>s with
+ <screen>&prompt.user; <userinput>dnssec-dsfromkey -f root-dnskey . > root.ds</userinput></screen>
+ These records use SHA-1 and SHA-256 respectively, and should look
+ similar to the following example, where the longer is using SHA-256.
+ </para>
+
+ <programlisting>. IN DS 19036 8 1 B256BD09DC8DD59F0E0F0D8541B8328DD986DF6E
+. IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5</programlisting>
+
+ <para>The SHA-256 <acronym>RR</acronym> can now be compared to the
+ digest in <ulink url="https://data.iana.org/root-anchors/root-anchors.xml">
+ https://data.iana.org/root-anchors/root-anchors.xml</ulink>. To be
+ absolutely sure that the key has not been tampered with the data in
+ the <acronym>XML</acronym> file can be verified using the
+ <acronym>PGP</acronym> signature in <ulink
+ url="https://data.iana.org/root-anchors/root-anchors.asc">
+ https://data.iana.org/root-anchors/root-anchors.asc</ulink>.</para>
+
+ <para>Next, the key must be formatted properly. This differs a
+ little between <acronym>BIND</acronym> versions 9.6.2 and 9.7 and
+ later. In version 9.7 support was added to automatically track
+ changes to the key and update it as necessary. This is done using
+ <literal>managed-keys</literal> as seen in the example below.
+ When using the older version, the key is added using a
+ <literal>trusted-keys</literal> statement and updates must be done
+ manually. For <acronym>BIND</acronym> 9.6.2 the format should look
+ like:</para>
+
+ <programlisting>trusted-keys {
+ "." 257 3 8
+ "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
+ FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
+ bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
+ X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
+ W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
+ Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
+ QxA+Uk1ihz0=";
+};</programlisting>
+
+ <para>For 9.7 the format will instead be:</para>
+
+ <programlisting>managed-keys {
+ "." initial-key 257 3 8
+ "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF
+ FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX
+ bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD
+ X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz
+ W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS
+ Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq
+ QxA+Uk1ihz0=";
+};</programlisting>
+
+ <para>The root key can now be added to <filename>named.conf</filename>
+ either directly or by including a file containing the key. After
+ these steps, configure <acronym>BIND</acronym> to do
+ <acronym>DNSSEC</acronym> validation on queries by editing
+ <filename>named.conf</filename> and adding the following to the
+ <literal>options</literal> directive:</para>
+
+ <programlisting>dnssec-enable yes;
+dnssec-validation yes;</programlisting>
+
+ <para>To verify that it is actually working use
+ <application>dig</application> to make a query for a signed zone
+ using the resolver just configured. A successful reply will contain
+ the <literal>AD</literal> flag to indicate the data was
+ authenticated. Running a query such as
+ <screen>&prompt.user; <userinput>dig @<replaceable>resolver</replaceable> +dnssec se ds </userinput></screen>
+ should return the <acronym>DS</acronym> <acronym>RR</acronym> for
+ the <literal>.se</literal> zone. In the <literal>flags:</literal>
+ section the <literal>AD</literal> flag should be set, as seen in:
+ </para>
+
+ <programlisting>...
+;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
+...</programlisting>
+
+ <para>The resolver is now capable of authenticating
+ <acronym>DNS</acronym> queries.</para>
+ </sect3>
+
+ <sect3 id="dns-dnssec-auth">
+ <title>Authoritative <acronym>DNS</acronym> server configuration</title>
+
+ <para>In order to get an authoritative name server to serve a
+ <acronym>DNSSEC</acronym> signed zone a little more work is
+ required. A zone is signed using cryptographic keys which must be
+ generated. It is possible to use only one key for this. The
+ preferred method however is to have a strong well-protected Key Signing Key
+ (<acronym role="Key Signing Key">KSK</acronym>) that is not rotated
+ very often and a Zone Signing Key
+ (<acronym role="Zone Signing Key">ZSK</acronym>) that is rotated more
+ frequently. Information on recommended operational practices can be
+ found in <ulink url="http://www.ietf.org/rfc/rfc4641.txt">
+ <acronym>RFC</acronym> 4641: <acronym>DNSSEC</acronym> Operational
+ Practices</ulink>. Practices regarding the root zone can be found in
+ <ulink url="http://www.root-dnssec.org/wp-content/uploads/2010/06/icann-dps-00.txt">
+ <acronym>DNSSEC</acronym> Practice Statement for the Root Zone
+ <acronym>KSK</acronym> operator</ulink> and
+ <ulink url="http://www.root-dnssec.org/wp-content/uploads/2010/06/vrsn-dps-00.txt">
+ <acronym>DNSSEC</acronym> Practice Statement for the Root Zone
+ <acronym>ZSK</acronym> operator</ulink>. The
+ <acronym role="Key Signing Key">KSK</acronym> is used to build a chain
+ of authority to the data in need of validation and as such is also
+ called a Secure Entry Point
+ (<acronym role="Secure Entry Point">SEP</acronym>) key. A message
+ digest of this key, called a Delegation Signer
+ (<acronym role="Delegation Signer">DS</acronym>) record, must be
+ published in the parent zone to establish the trust chain. How
+ this is accomplished depends on the parent zone owner. The
+ <acronym role="Zone Signing Key">ZSK</acronym> is used
+ to sign the zone, and only needs to be published there.</para>
+
+ <para>To enable <acronym>DNSSEC</acronym> for the <hostid
+ role="domainname">example.com</hostid> zone depicted in previous
+ examples, the first step is to use
+ <application>dnssec-keygen</application> to generate the
+ <acronym>KSK</acronym> and <acronym>ZSK</acronym> key pair. This
+ key pair can utilize different cryptographic algorithms. It is
+ recommended to use RSA/SHA256 for the keys and 2048 bits key length
+ should be enough. To generate the <acronym>KSK</acronym> for
+ <hostid role="domainname">example.com</hostid>, run
+ <screen>&prompt.user; <userinput>dnssec-keygen -f KSK -a RSASHA256 -b 2048 -n ZONE example.com</userinput></screen>
+ and to generate the
+ <acronym>ZSK</acronym>, run
+ <screen>&prompt.user; <userinput>dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com</userinput></screen>
+ <application>dnssec-keygen</application> outputs two files, the public
+ and the private keys in files named similar to
+ <filename>Kexample.com.+005+nnnnn.key</filename> (public) and
+ <filename>Kexample.com.+005+nnnnn.private</filename> (private). The
+ <literal>nnnnn</literal> part of the file name is a five digit key ID.
+ Keep track of which key ID belongs to which key. This is especially
+ important when having more than one key in a zone. It is also
+ possible to rename the keys. For each <acronym>KSK</acronym> file do:
+ <screen>&prompt.user; <userinput>mv Kexample.com+005+nnnnn.key Kexample.com+005+nnnnn.KSK.key</userinput>
+ &prompt.user; <userinput>mv Kexample.com+005+nnnnn.private Kexample.com+005+nnnnn.KSK.private</userinput></screen>
+ For the <acronym>ZSK</acronym> files, substitute
+ <literal>KSK</literal> for <literal>ZSK</literal> as necessary. The
+ files can now be included in the zone file, using the
+ <literal>$include</literal> statement. It should look something like
+ this:</para>
+
+ <programlisting>$include Kexample.com.+005+nnnnn.KSK.key ; ZSK
+$include Kexample.com.+005+nnnnn.ZSK.key ; KSK</programlisting>
+
+ <para>Finally, sign the zone and tell <acronym>BIND</acronym> to use
+ the signed zone file. To sign a zone
+ <application>dnssec-signzone</application> is used. The command to
+ sign the zone <hostid role="domainname">example.com</hostid>, located in
+ <filename>example.com.db</filename> would look similar to
+ <screen>&prompt.user; <userinput>dnssec-signzone -o example.com -k Kexample.com+005+nnnnn.KSK example.com.db Kexample.com+005+nnnnn.ZSK.key</userinput></screen>
+ The key supplied to
+ the <option>-k</option> argument is the <acronym>KSK</acronym> and
+ the other key file is the <acronym>ZSK</acronym> that should be used
+ in the signing. It is possible to supply more than one
+ <acronym>KSK</acronym> and <acronym>ZSK</acronym>, which will result
+ in the zone being signed with all supplied keys. This can be needed
+ to supply zone data signed using more than one algorithm. The output
+ of <application>dnssec-signzone</application> is a zone file with all
+ <acronym>RR</acronym>s signed. This output will end up in a file with
+ the extension <literal>.signed</literal>, such as
+ <filename>example.com.db.signed</filename>. The
+ <acronym role="Delegation Signer">DS</acronym> records will also be
+ written to a separate file <filename>dsset-example.com</filename>.
+ To use this signed zone just modify the zone directive in
+ <filename>named.conf</filename> to use
+ <filename>example.com.db.signed</filename>. By default, the
+ signatures are only valid 30 days, meaning that the zone needs to
+ be resigned in about 15 days to be sure that resolvers are not
+ caching records with stale signatures. It is possible to make a
+ script and a cron job to do this. See relevant manuals for details.
+ </para>
+
+ <para>Be sure to keep private keys confidential, as with all
+ cryptographic keys. When changing a key it is best to include the
+ new key into the zone, while still signing with
+ the old one, and then move over to using the new key to sign. After
+ these steps are done the old key can be removed from the zone.
+ Failure to do this might render the <acronym>DNS</acronym> data
+ unavailable for a time, until the new key has propagated through the
+ <acronym>DNS</acronym> hierarchy. For more information on key
+ rollovers and other <acronym>DNSSEC</acronym> operational issues, see
+ <ulink url="http://www.ietf.org/rfc/rfc4641.txt">
+ <acronym>RFC</acronym> 4641: <acronym>DNSSEC</acronym> Operational
+ practices</ulink>.</para>
+ </sect3>
+
+ <sect3>
+ <title>Automation using <acronym>BIND</acronym> 9.7 or later</title>
+ <para>Beginning with <acronym>BIND</acronym> version 9.7 a new feature
+ called <emphasis>Smart Signing</emphasis> was introduced. This
+ feature aims to make the key management and signing process simpler by
+ automating parts of the task. By putting the keys into a directory
+ called a <emphasis>key repository</emphasis>, and using the new option
+ <literal>auto-dnssec</literal>, it is possible to create a dynamic zone
+ which will be resigned as needed. To update this zone use
+ <application>nsupdate</application> with the new option
+ <option>-l</option>. <application>rndc</application> has
+ also grown the ability to sign zones with keys in the key repository,
+ using the option <option>sign</option>. To tell
+ <acronym>BIND</acronym> to use this automatic signing and zone
+ updating for <hostid role="domainname">example.com</hostid>, add the
+ following to <filename>named.conf</filename>:</para>
+
+ <programlisting>zone example.com {
+ type master;
+ key-directory "/etc/named/keys";
+ update-policy local;
+ auto-dnssec maintain;
+ file "/etc/named/dynamic/example.com.zone";
+};</programlisting>
+
+ <para>After making these changes, generate keys for the zone as
+ explained in <xref linkend="dns-dnssec-auth">, put those keys
+ in the key repository given as the argument to the
+ <literal>key-directory</literal> in the zone configuration and the
+ zone will be signed automatically. Updates to a zone configured
+ this way must be done using
+ <application>nsupdate</application>, which will take care of
+ re-signing the zone with the new data added. For further details,
+ see <xref linkend="dns-read"> and the <acronym>BIND</acronym>
+ documentation.</para>
+ </sect3>
+
+ </sect2>
+
+ <sect2>
<title>Security</title>
<para>Although BIND is the most common implementation of DNS,
@@ -3897,11 +4216,12 @@
</tip>
</sect2>
- <sect2>
+ <sect2 id="dns-read">
<title>Further Reading</title>
<para>BIND/<application>named</application> manual pages:
- &man.rndc.8; &man.named.8; &man.named.conf.5;</para>
+ &man.rndc.8; &man.named.8; &man.named.conf.5; &man.nsupdate.8;
+ &man.dnssec-signzone.8; &man.dnssec-keygen.8;</para>
<itemizedlist>
<listitem>
@@ -3922,6 +4242,17 @@
</listitem>
<listitem>
+ <para><ulink url="http://www.root-dnssec.org/documentation/"> Root
+ <acronym>DNSSEC</acronym></ulink></para>
+ </listitem>
+
+ <listitem>
+ <para><ulink url="http://data.iana.org/root-anchors/draft-icann-dnssec-trust-anchor.html">
+ <acronym>DNSSEC</acronym> Trust Anchor Publication for the Root
+ Zone</ulink></para>
+ </listitem>
+
+ <listitem>
<para><ulink
url="http://tools.ietf.org/html/rfc1034">RFC1034
- Domain Names - Concepts and Facilities</ulink></para>
@@ -3932,6 +4263,38 @@
url="http://tools.ietf.org/html/rfc1035">RFC1035
- Domain Names - Implementation and Specification</ulink></para>
</listitem>
+
+ <listitem>
+ <para><ulink
+ url="http://tools.ietf.org/html/rfc4033">RFC4033
+ - DNS Security Introduction and Requirements</ulink></para>
+ </listitem>
+
+ <listitem>
+ <para><ulink
+ url="http://tools.ietf.org/html/rfc4034">RFC4034
+ - Resource Records for the DNS Security Extensions</ulink></para>
+ </listitem>
+
+ <listitem>
+ <para><ulink
+ url="http://tools.ietf.org/html/rfc4035">RFC4035
+ - Protocol Modifications for the DNS Security Extensions</ulink></para>
+ </listitem>
+
+ <listitem>
+ <para><ulink
+ url="http://tools.ietf.org/html/rfc4641">RFC4641
+ - DNSSEC Operational Practices</ulink></para>
+ </listitem>
+
+ <listitem>
+ <para><ulink
+ url="http://tools.ietf.org/html/rfc5011">RFC 5011
+ - Automated Updates of DNS Security (<acronym>DNSSEC</acronym>
+ Trust Anchors</ulink></para>
+ </listitem>
+
</itemizedlist>
</sect2>
</sect1>
Index: share/sgml/man-refs.ent
===================================================================
RCS file: /home/ncvs/doc/share/sgml/man-refs.ent,v
retrieving revision 1.511
diff -u -d -r1.511 man-refs.ent
--- share/sgml/man-refs.ent 11 Feb 2011 16:15:44 -0000 1.511
+++ share/sgml/man-refs.ent 23 May 2011 12:10:56 -0000
@@ -4257,6 +4257,8 @@
<!ENTITY man.diskpart.8 "<citerefentry/<refentrytitle/diskpart/<manvolnum/8//">
<!ENTITY man.dm.8 "<citerefentry/<refentrytitle/dm/<manvolnum/8//">
<!ENTITY man.dmesg.8 "<citerefentry/<refentrytitle/dmesg/<manvolnum/8//">
+<!ENTITY man.dnssec-keygen.8 "<citerefentry/<refentrytitle/dnssec-keygen<manvolnum/8//">
+<!ENTITY man.dnssec-signzone.8 "<citerefentry/<refentrytitle/dnssec-signzone<manvolnum/8//">
<!ENTITY man.dump.8 "<citerefentry/<refentrytitle/dump/<manvolnum/8//">
<!ENTITY man.dumpfs.8 "<citerefentry/<refentrytitle/dumpfs/<manvolnum/8//">
<!ENTITY man.dumpon.8 "<citerefentry/<refentrytitle/dumpon/<manvolnum/8//">
--------------090906090406000801020902--
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