Date: Sun, 22 May 2011 11:34:09 +0200 (CEST) From: Niclas Zeising <niclas.zeising@gmail.com> To: FreeBSD-gnats-submit@FreeBSD.org Subject: docs/157245: [PATCH] [RFC] Add a section about DNSSEC to the DNS chapter in the handbook Message-ID: <201105220934.p4M9Y9JL041108@vincent.daemonic.se> Resent-Message-ID: <201105220940.p4M9e8fi016684@freefall.freebsd.org>
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>Number: 157245 >Category: docs >Synopsis: [PATCH] [RFC] Add a section about DNSSEC to the DNS chapter in the handbook >Confidential: no >Severity: non-critical >Priority: low >Responsible: freebsd-doc >State: open >Quarter: >Keywords: >Date-Required: >Class: update >Submitter-Id: current-users >Arrival-Date: Sun May 22 09:40:08 UTC 2011 >Closed-Date: >Last-Modified: >Originator: Niclas Zeising >Release: FreeBSD 8.2-RELEASE amd64 >Organization: >Environment: System: FreeBSD vincent.daemonic.se 8.2-RELEASE FreeBSD 8.2-RELEASE #0: Wed Apr 20 17:22:47 CEST 2011 root@vincent.daemonic.se:/usr/obj/usr/src/sys/VINCENT amd64 >Description: DNSSEC is deemd to be very important in order to secure the Internet as a whole I have written a section about what DNSSEC is and how to configure BIND to use it, intended for the FreeBSD handbook. As a first step, I would like some review on my work, both from a technical and a linguistic point of view. >How-To-Repeat: >Fix: Attached patch contains my changes to the handbook to include information about DNSSEC. Please review it as a first step, so that I can work on getting it into the handbook. --- network-servers.chapter.sgml.diff begins here --- Index: 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 --- chapter.sgml 15 May 2011 20:41:30 -0000 1.130 +++ chapter.sgml 21 May 2011 19:13:24 -0000 @@ -3872,6 +3872,293 @@ </sect2> <sect2> + <title>DNSSEC</title> + <indexterm> + <primary>BIND</primary> + <secondary>DNS security extensions</secondary> + </indexterm> + + <para>Domain Name System Security Extensions, or <acronym>DNSSEC</acronym> + for short, is a suite of specifications to protect the + <acronym>DNS</acronym> clients, i.e. Internet resolvers, from forged + <acronym>DNS</acronym> data, such as spoofed <acronym>DNS</acronym> + records. By using digital signatures, a resolver can verify the + integrity and authenticity of the record. It is worth noticing that + <acronym>DNSSEC</acronym> does only provide integrity, it does not + provide either confidentiality nor protection against false assumptions, + meaning that it cannot protect against people going to + <hostid role="domainname">example.com</hostid> instead of + <hostid role="domainname">example.net</hostid> and similar. The only + thing <acronym>DNSSEC</acronym> does is authenticate that the data is + from the domain owner and that it has not been compromised in transit. + The security of <acronym>DNS</acronym> is believed to be an important + step in securing the Internet in general. For a more in-depth + knowledge of how <acronym>DNSSEC</acronym> works, the relevant + <acronym>RFC</acronym>s is a good place to start. See the list at the + end of this chapter.</para> + + <para>The next two sections will demonstrate how to enable + <acronym>DNSSEC</acronym> for an authorative <acronym>DNS</acronym> + server and a recursive (or cashing) <acronym>DNS</acronym> server + running <acronym>BIND</acronym>9. While all versions of + <acronym>BIND</acronym>9 supports <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 + <acronym>BIND</acronym> 9.7 or later, to take advantage of the automatic + key updating function for the root key, as well as other functions 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>To enable <acronym>DNSSEC</acronym> validation of queries done by + a recursive <acronym>DNS</acronym> server, a few changes to + <filename>named.conf</filename> are needed. However, before changing + <filename>named.conf</filename> the root zone key, or trust anchor, + must be aquired. Currently the root zone key is not available in a + file format <acronym>BIND</acronym> understands, so this has to be + manually generated. The key itself can be obtained by querying the + root zone for it, using <appication>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:<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>Do not be alarmed if the keys differ, they might + have changed since this was last updated. This output actually + contains two keys. The first key in the listing, with the value 257 + behind the DNSKEY record type, is the one needed. The value + indicates that this is a Secure Entry Point, more 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 section <xref + linkend="dns-dnssec-auth">.</para> + + <para>Now that the key is obtained, it has to be verified to be + correct, and then made into a format <acronym>BIND</acronym> can + use. The next step is to generate a + <acronym role="Delegation signer">DS</acronym> + <acronym role="Resource Record">RR</acronym> set. This is done by + running <screen>&propmt.user; <userinput>dnssec-dsfromkey -f + root-dnskey . > root.ds</userinput></screen>, which will emit two + <acronym>RR</acronyms>s into <filename>root.ds</filename>. These + records are using SHA-1 and SHA-256 respectively, and should look + similar to this, where the longer is using SHA-256.<programlisting> +. IN DS 19036 8 1 B256BD09DC8DD59F0E0F0D8541B8328DD986DF6E +. IN DS 19036 8 2 49AAC11D7B6F6446702E54A1607371607A1A41855200FD2CE1CDDE32F24E8FB5 + </programlisting>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>The last step is to format the key to a format + <acronym>BIND</acronym> understand. This differs a little between + version 9.6.2 and 9.7 and later. Both uses a + <literal>managed-keys</literal> clause, but support for + <literal>initial-key</literal> was added in 9.7. + <literal>initial-key</literal> tells <acronym>BIND</acronym> + automatic tracking of the key. With <acronym>BIND</acronym> 9.6.2 + it is necessary to update the key manually when it is changed. The + format should look like, for <acronym>BIND</acronym> 9.6.2: + <programlisting> +managed-keys { + "." 257 3 8 + "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF + FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX + bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD + X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz + W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS + Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq + QxA+Uk1ihz0="; +}; + </programlisting>For 9.7 the format will instead be: + <programlisting> +managed-keys { + "." initial-key 257 3 8 + "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF + FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX + bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD + X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz + W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS + Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq + QxA+Uk1ihz0="; +}; + </programlisting>The <literal>managed-keys</literal> directive can + now be added to <filename>named.conf</filename> either directly or + by including a file containing the key. After all this is done it + is just to tell <acronym>BIND</acronym> to do + <acronym>DNSSEC</acronym> validation on queries. This is achieved by + editing <filename>named.conf</filename> and add the following to the + <literal>options</literal> directive:<programlisting> +dnssec-enable yes; +dnssec-validation yes; + </programlisting></para> + + <para>To verify that it is actually working, use + <application>dig</application> to make a query for a signed zone + using the resolver just set up. A successful reply will contain + the <literal><acronym role="Authenticated Data">AD</acronym> + </literal> flag to indicate the data was authenticated. Running a + query such as <screen>&prompt.user; <userinput>dig @resolver +dnssec + se ds</userinput><screen> should return the <acronym>DS</acronym> + <acronym>RR</acronyms> for the .se zone. In the + <literal>flags:</literal> section the + <literal><acronym>AD</acronym></literal> flag should be set, as seen + in:<programlisting> +... +;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1 +... + </programlisting>. This means that the resolver is now capable of + authenticate made <acronym>DNS</acronym>queries.</para> + </sect3> + + <sect3 id="dns-dnssec-auth"> + <title>Authorative <acronym>DNS</acronym> server configuration</title> + <para>In order to get an authorative nameserver to serve a + <acronym>DNSSEC</acronym> signed zone, a little more work is + required. To sign a zone, two cryptographic keys for that zone must + be generated. These two keys are usually called the Key Signing Key + (<acronym role="Key Signing Key">KSK</acronym>) and Zone Signing Key + (<acronym role="Zone Signing Key">ZSK</acronym>) respectively. 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 also called + a Secure Entry Point (<acronym role="Secure Entry + Point">SEP</acronym>) key. This key needs to be published in the + parent zone as well, 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> keypair. This keypair + can utilize different cryptograhic algorithms. Currently the mandatory + algorithm is <literal>RSA/SHA-1</literal>. In the examples the key + length used is 2048 bits for the <acronym>KSK</acronym> and 1024 bits + for the <acronym>ZSK</acronym>. To generate the + <acronym>KSK</acronym> for <hostid + role="domainname">example.com</hostid>, run <screen>&promt.user; + <userinput>dnssec-keygen -f KSK -a RSASHA1 -b 2048 -n ZONE + example.com</userinput></screen> and to generate the + <acronym>ZSK</acronym>, run <screen>&promt.user; + <userinput>dnssec-keygen -a RSASHA1 -b 1024 -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. The public key + files can now be included in the zone file, using the + <literal>$include</literal> statement. It should look something like + this:<programlisting> +$include Kexample.net.+005+nnnnn.key ; ZSK +$include Kexample.net.+005+nnnnn.key ; KSK + </programlisting></para> + + <para>The only steps left is to sign the zone and tell + <acronym>BIND</acronym> to use the signed zonefile. 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>&promt.user; <userinput>dnssec-signzone -o example.com -k + Kexample.com+005+nnnnn example.com.db + Kexample.com+005+nnnnn.key</userinput></screen>. The key supplied to + the <literal>-k</literal> 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>. To use this signed zone + just modify the zone directive in <filename>named.conf</filename> to + use this file. By default, the signatures are only valid 30 days, + meaning that the zone needs to be resigned within this time. It is + possible to make a script and a cron job to do this. See relevant + manuals for details.</para> + <para>Some cautionary words at the end. 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 key, 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. + Failiure to do this might render the <acronym>DNS</acronym> data + unavailable for a time, untill 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, + from now on called a key repository, 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 the tool + <application>nsupdate</application> with the new option + <literal>-l</literal> is used. <application>rndc</application> has + also grown the ability to sign zones with keys in the key repository, + using the option <literal>sign</literal>. To make this work, put + something similar to what is shown below into + <filename>named.conf</filename>.<programlisting> +zone example.com { + type master; + key-directory "keys"; + update-policy local; + auto-dnssec maintain; + file "dynamic/example.com.zone"; +}; + </programlisting>This will tell named to use automatic signing and + updating of the zone <hostid role="domainname">example.com</hostid>. + After this is done just generate keys for the zone as explained in + <xref linkened="dns-dnssec-auth">, put these in the key repository + denoted by <literal>key-directory</literal> in the zone configuration + and sign the zone using <application>rndc</application>. Updates to + the zone is done using <application>nsupdate</application> which will + take care of resigning the zone with the new data added. For further + details, see <xref linkened="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, @@ -3897,7 +4184,7 @@ </tip> </sect2> - <sect2> + <sect2 id="dns-read"> <title>Further Reading</title> <para>BIND/<application>named</application> manual pages: @@ -3932,6 +4219,38 @@ 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 + - Recource 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> --- network-servers.chapter.sgml.diff ends here --- >Release-Note: >Audit-Trail: >Unformatted:
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