269 lines
12 KiB
XML
269 lines
12 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!--
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- Copyright (C) 2010, 2012 Internet Systems Consortium, Inc. ("ISC")
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-
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- Permission to use, copy, modify, and/or distribute this software for any
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- purpose with or without fee is hereby granted, provided that the above
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- copyright notice and this permission notice appear in all copies.
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-
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- THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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- AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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- OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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- PERFORMANCE OF THIS SOFTWARE.
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-->
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<!-- $Id$ -->
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<sect1 id="dnssec.dynamic.zones">
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<title>DNSSEC, Dynamic Zones, and Automatic Signing</title>
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<para>As of BIND 9.7.0 it is possible to change a dynamic zone
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from insecure to signed and back again. A secure zone can use
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either NSEC or NSEC3 chains.</para>
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<sect2>
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<title>Converting from insecure to secure</title>
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</sect2>
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<para>Changing a zone from insecure to secure can be done in two
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ways: using a dynamic DNS update, or the
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<command>auto-dnssec</command> zone option.</para>
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<para>For either method, you need to configure
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<command>named</command> so that it can see the
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<filename>K*</filename> files which contain the public and private
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parts of the keys that will be used to sign the zone. These files
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will have been generated by
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<command>dnssec-keygen</command>. You can do this by placing them
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in the key-directory, as specified in
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<filename>named.conf</filename>:</para>
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<programlisting>
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zone example.net {
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type master;
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update-policy local;
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file "dynamic/example.net/example.net";
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key-directory "dynamic/example.net";
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};
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</programlisting>
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<para>If one KSK and one ZSK DNSKEY key have been generated, this
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configuration will cause all records in the zone to be signed
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with the ZSK, and the DNSKEY RRset to be signed with the KSK as
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well. An NSEC chain will be generated as part of the initial
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signing process.</para>
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<sect2>
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<title>Dynamic DNS update method</title>
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</sect2>
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<para>To insert the keys via dynamic update:</para>
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<screen>
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% nsupdate
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> ttl 3600
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> update add example.net DNSKEY 256 3 7 AwEAAZn17pUF0KpbPA2c7Gz76Vb18v0teKT3EyAGfBfL8eQ8al35zz3Y I1m/SAQBxIqMfLtIwqWPdgthsu36azGQAX8=
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> update add example.net DNSKEY 257 3 7 AwEAAd/7odU/64o2LGsifbLtQmtO8dFDtTAZXSX2+X3e/UNlq9IHq3Y0 XtC0Iuawl/qkaKVxXe2lo8Ct+dM6UehyCqk=
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> send
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</screen>
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<para>While the update request will complete almost immediately,
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the zone will not be completely signed until
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<command>named</command> has had time to walk the zone and
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generate the NSEC and RRSIG records. The NSEC record at the apex
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will be added last, to signal that there is a complete NSEC
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chain.</para>
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<para>If you wish to sign using NSEC3 instead of NSEC, you should
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add an NSEC3PARAM record to the initial update request. If you
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wish the NSEC3 chain to have the OPTOUT bit set, set it in the
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flags field of the NSEC3PARAM record.</para>
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<screen>
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% nsupdate
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> ttl 3600
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> update add example.net DNSKEY 256 3 7 AwEAAZn17pUF0KpbPA2c7Gz76Vb18v0teKT3EyAGfBfL8eQ8al35zz3Y I1m/SAQBxIqMfLtIwqWPdgthsu36azGQAX8=
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> update add example.net DNSKEY 257 3 7 AwEAAd/7odU/64o2LGsifbLtQmtO8dFDtTAZXSX2+X3e/UNlq9IHq3Y0 XtC0Iuawl/qkaKVxXe2lo8Ct+dM6UehyCqk=
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> update add example.net NSEC3PARAM 1 1 100 1234567890
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> send
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</screen>
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<para>Again, this update request will complete almost
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immediately; however, the record won't show up until
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<command>named</command> has had a chance to build/remove the
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relevant chain. A private type record will be created to record
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the state of the operation (see below for more details), and will
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be removed once the operation completes.</para>
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<para>While the initial signing and NSEC/NSEC3 chain generation
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is happening, other updates are possible as well.</para>
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<sect2>
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<title>Fully automatic zone signing</title>
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</sect2>
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<para>To enable automatic signing, add the
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<command>auto-dnssec</command> option to the zone statement in
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<filename>named.conf</filename>.
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<command>auto-dnssec</command> has two possible arguments:
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<constant>allow</constant> or
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<constant>maintain</constant>.</para>
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<para>With
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<command>auto-dnssec allow</command>,
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<command>named</command> can search the key directory for keys
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matching the zone, insert them into the zone, and use them to
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sign the zone. It will do so only when it receives an
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<command>rndc sign <zonename></command> or
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<command>rndc loadkeys <zonename></command> command.</para>
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<para>
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<!-- TODO: this is repeated in the ARM -->
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<command>auto-dnssec maintain</command> includes the above
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functionality, but will also automatically adjust the zone's
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DNSKEY records on schedule according to the keys' timing metadata.
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(See <xref linkend="man.dnssec-keygen"/> and
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<xref linkend="man.dnssec-settime"/> for more information.)
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If keys are present in the key directory the first time the zone
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is loaded, it will be signed immediately, without waiting for an
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<command>rndc sign</command> or <command>rndc loadkeys</command>
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command. (Those commands can still be used when there are unscheduled
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key changes, however.)
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</para>
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<para>Using the
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<command>auto-dnssec</command> option requires the zone to be
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configured to allow dynamic updates, by adding an
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<command>allow-update</command> or
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<command>update-policy</command> statement to the zone
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configuration. If this has not been done, the configuration will
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fail.</para>
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<sect2>
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<title>Private-type records</title>
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</sect2>
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<para>The state of the signing process is signaled by
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private-type records (with a default type value of 65534). When
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signing is complete, these records will have a nonzero value for
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the final octet (for those records which have a nonzero initial
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octet).</para>
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<para>The private type record format: If the first octet is
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non-zero then the record indicates that the zone needs to be
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signed with the key matching the record, or that all signatures
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that match the record should be removed.</para>
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<para>
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<literallayout>
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<!-- TODO: how to format this? -->
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algorithm (octet 1)
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key id in network order (octet 2 and 3)
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removal flag (octet 4)
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complete flag (octet 5)
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</literallayout>
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</para>
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<para>Only records flagged as "complete" can be removed via
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dynamic update. Attempts to remove other private type records
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will be silently ignored.</para>
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<para>If the first octet is zero (this is a reserved algorithm
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number that should never appear in a DNSKEY record) then the
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record indicates changes to the NSEC3 chains are in progress. The
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rest of the record contains an NSEC3PARAM record. The flag field
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tells what operation to perform based on the flag bits.</para>
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<para>
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<literallayout>
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<!-- TODO: how to format this? -->
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0x01 OPTOUT
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0x80 CREATE
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0x40 REMOVE
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0x20 NONSEC
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</literallayout>
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</para>
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<sect2>
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<title>DNSKEY rollovers</title>
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</sect2>
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<para>As with insecure-to-secure conversions, rolling DNSSEC
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keys can be done in two ways: using a dynamic DNS update, or the
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<command>auto-dnssec</command> zone option.</para>
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<sect2>
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<title>Dynamic DNS update method</title>
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</sect2>
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<para> To perform key rollovers via dynamic update, you need to add
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the <filename>K*</filename> files for the new keys so that
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<command>named</command> can find them. You can then add the new
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DNSKEY RRs via dynamic update.
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<command>named</command> will then cause the zone to be signed
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with the new keys. When the signing is complete the private type
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records will be updated so that the last octet is non
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zero.</para>
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<para>If this is for a KSK you need to inform the parent and any
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trust anchor repositories of the new KSK.</para>
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<para>You should then wait for the maximum TTL in the zone before
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removing the old DNSKEY. If it is a KSK that is being updated,
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you also need to wait for the DS RRset in the parent to be
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updated and its TTL to expire. This ensures that all clients will
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be able to verify at least one signature when you remove the old
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DNSKEY.</para>
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<para>The old DNSKEY can be removed via UPDATE. Take care to
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specify the correct key.
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<command>named</command> will clean out any signatures generated
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by the old key after the update completes.</para>
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<sect2>
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<title>Automatic key rollovers</title>
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</sect2>
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<para>When a new key reaches its activation date (as set by
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<command>dnssec-keygen</command> or <command>dnssec-settime</command>),
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if the <command>auto-dnssec</command> zone option is set to
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<constant>maintain</constant>, <command>named</command> will
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automatically carry out the key rollover. If the key's algorithm
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has not previously been used to sign the zone, then the zone will
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be fully signed as quickly as possible. However, if the new key
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is replacing an existing key of the same algorithm, then the
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zone will be re-signed incrementally, with signatures from the
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old key being replaced with signatures from the new key as their
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signature validity periods expire. By default, this rollover
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completes in 30 days, after which it will be safe to remove the
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old key from the DNSKEY RRset.</para>
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<sect2>
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<title>NSEC3PARAM rollovers via UPDATE</title>
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</sect2>
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<para>Add the new NSEC3PARAM record via dynamic update. When the
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new NSEC3 chain has been generated, the NSEC3PARAM flag field
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will be zero. At this point you can remove the old NSEC3PARAM
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record. The old chain will be removed after the update request
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completes.</para>
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<sect2>
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<title>Converting from NSEC to NSEC3</title>
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</sect2>
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<para>To do this, you just need to add an NSEC3PARAM record. When
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the conversion is complete, the NSEC chain will have been removed
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and the NSEC3PARAM record will have a zero flag field. The NSEC3
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chain will be generated before the NSEC chain is
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destroyed.</para>
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<sect2>
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<title>Converting from NSEC3 to NSEC</title>
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</sect2>
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<para>To do this, use <command>nsupdate</command> to
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remove all NSEC3PARAM records with a zero flag
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field. The NSEC chain will be generated before the NSEC3 chain is
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removed.</para>
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<sect2>
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<title>Converting from secure to insecure</title>
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</sect2>
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<para>To convert a signed zone to unsigned using dynamic DNS,
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delete all the DNSKEY records from the zone apex using
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<command>nsupdate</command>. All signatures, NSEC or NSEC3 chains,
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and associated NSEC3PARAM records will be removed automatically.
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This will take place after the update request completes.</para>
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<para> This requires the
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<command>dnssec-secure-to-insecure</command> option to be set to
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<userinput>yes</userinput> in
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<filename>named.conf</filename>.</para>
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<para>In addition, if the <command>auto-dnssec maintain</command>
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zone statement is used, it should be removed or changed to
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<command>allow</command> instead (or it will re-sign).
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</para>
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<sect2>
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<title>Periodic re-signing</title>
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</sect2>
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<para>In any secure zone which supports dynamic updates, named
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will periodically re-sign RRsets which have not been re-signed as
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a result of some update action. The signature lifetimes will be
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adjusted so as to spread the re-sign load over time rather than
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all at once.</para>
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<sect2>
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<title>NSEC3 and OPTOUT</title>
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</sect2>
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<para>
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<command>named</command> only supports creating new NSEC3 chains
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where all the NSEC3 records in the zone have the same OPTOUT
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state.
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<command>named</command> supports UPDATES to zones where the NSEC3
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records in the chain have mixed OPTOUT state.
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<command>named</command> does not support changing the OPTOUT
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state of an individual NSEC3 record, the entire chain needs to be
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changed if the OPTOUT state of an individual NSEC3 needs to be
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changed.</para>
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</sect1>
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