doc/arm/dnssec.xml

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<sect1 id="dnssec.dynamic.zones">
  <title>DNSSEC, Dynamic Zones, and Automatic Signing</title>
  <para>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.</para>
  <sect2>
    <title>Converting from insecure to secure</title>
  </sect2>
  <para>Changing a zone from insecure to secure can be done in two
  ways: using a dynamic DNS update, or the
  <command>auto-dnssec</command> zone option.</para>
  <para>For either method, you need to configure
  <command>named</command> so that it can see the
  <filename>K*</filename> 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
  <command>dnssec-keygen</command>. You can do this by placing them
  in the key-directory, as specified in
  <filename>named.conf</filename>:</para>
  <programlisting>
        zone example.net {
                type master;
                update-policy local;
                file "dynamic/example.net/example.net";
                key-directory "dynamic/example.net";
        };
</programlisting>
  <para>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.</para>
  <sect2>
    <title>Dynamic DNS update method</title>
  </sect2>
  <para>To insert the keys via dynamic update:</para>
  <screen>
        % nsupdate
        &gt; ttl 3600
        &gt; update add example.net DNSKEY 256 3 7 AwEAAZn17pUF0KpbPA2c7Gz76Vb18v0teKT3EyAGfBfL8eQ8al35zz3Y I1m/SAQBxIqMfLtIwqWPdgthsu36azGQAX8=
        &gt; update add example.net DNSKEY 257 3 7 AwEAAd/7odU/64o2LGsifbLtQmtO8dFDtTAZXSX2+X3e/UNlq9IHq3Y0 XtC0Iuawl/qkaKVxXe2lo8Ct+dM6UehyCqk=
        &gt; send
</screen>
  <para>While the update request will complete almost immediately,
  the zone will not be completely signed until
  <command>named</command> 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.</para>
  <para>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.</para>
  <screen>
        % nsupdate
        &gt; ttl 3600
        &gt; update add example.net DNSKEY 256 3 7 AwEAAZn17pUF0KpbPA2c7Gz76Vb18v0teKT3EyAGfBfL8eQ8al35zz3Y I1m/SAQBxIqMfLtIwqWPdgthsu36azGQAX8=
        &gt; update add example.net DNSKEY 257 3 7 AwEAAd/7odU/64o2LGsifbLtQmtO8dFDtTAZXSX2+X3e/UNlq9IHq3Y0 XtC0Iuawl/qkaKVxXe2lo8Ct+dM6UehyCqk=
        &gt; update add example.net NSEC3PARAM 1 1 100 1234567890
        &gt; send
</screen>
  <para>Again, this update request will complete almost
  immediately; however, the record won't show up until
  <command>named</command> has had a chance to build/remove the
  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.</para>
  <para>While the initial signing and NSEC/NSEC3 chain generation
  is happening, other updates are possible as well.</para>
  <sect2>
    <title>Fully automatic zone signing</title>
  </sect2>
  <para>To enable automatic signing, add the
  <command>auto-dnssec</command> option to the zone statement in
  <filename>named.conf</filename>.
  <command>auto-dnssec</command> has two possible arguments:
  <constant>allow</constant> or
  <constant>maintain</constant>.</para>
  <para>With
  <command>auto-dnssec allow</command>,
  <command>named</command> 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
  <command>rndc sign &lt;zonename&gt;</command> or
  <command>rndc loadkeys &lt;zonename&gt;</command> command.</para>
  <para>
  <!-- TODO: this is repeated in the ARM -->
  <command>auto-dnssec maintain</command> includes the above
  functionality, but will also automatically adjust the zone's
  DNSKEY records on schedule according to the keys' timing metadata.
  (See <xref linkend="man.dnssec-keygen"/> and
  <xref linkend="man.dnssec-settime"/> for more information.)
  If keys are present in the key directory the first time the zone
  is loaded, it will be signed immediately, without waiting for an
  <command>rndc sign</command> or <command>rndc loadkeys</command>
  command. (Those commands can still be used when there are unscheduled
  key changes, however.)
  </para>
  <para>Using the
  <command>auto-dnssec</command> option requires the zone to be
  configured to allow dynamic updates, by adding an
  <command>allow-update</command> or
  <command>update-policy</command> statement to the zone
  configuration. If this has not been done, the configuration will
  fail.</para>
  <sect2>
    <title>Private-type records</title>
  </sect2>
  <para>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).</para>
  <para>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.</para>
  <para>
    <literallayout>
<!-- TODO: how to format this? -->
  algorithm (octet 1)
  key id in network order (octet 2 and 3)
  removal flag (octet 4)
  complete flag (octet 5)
</literallayout>
  </para>
  <para>Only records flagged as "complete" can be removed via
  dynamic update. Attempts to remove other private type records
  will be silently ignored.</para>
  <para>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.</para>
  <para>
    <literallayout>
<!-- TODO: how to format this? -->
  0x01 OPTOUT
  0x80 CREATE
  0x40 REMOVE
  0x20 NONSEC
</literallayout>
  </para>
  <sect2>
    <title>DNSKEY rollovers</title>
  </sect2>
  <para>As with insecure-to-secure conversions, rolling DNSSEC
  keys can be done in two ways: using a dynamic DNS update, or the
  <command>auto-dnssec</command> zone option.</para>
  <sect2>
    <title>Dynamic DNS update method</title>
  </sect2>
  <para> To perform key rollovers via dynamic update, you need to add
  the <filename>K*</filename> files for the new keys so that
  <command>named</command> can find them. You can then add the new
  DNSKEY RRs via dynamic update.
  <command>named</command> 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.</para>
  <para>If this is for a KSK you need to inform the parent and any
  trust anchor repositories of the new KSK.</para>
  <para>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.</para>
  <para>The old DNSKEY can be removed via UPDATE. Take care to
  specify the correct key.
  <command>named</command> will clean out any signatures generated
  by the old key after the update completes.</para>
  <sect2>
    <title>Automatic key rollovers</title>
  </sect2>
  <para>When a new key reaches its activation date (as set by
  <command>dnssec-keygen</command> or <command>dnssec-settime</command>),
  if the <command>auto-dnssec</command> zone option is set to
  <constant>maintain</constant>, <command>named</command> 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.</para>
  <sect2>
    <title>NSEC3PARAM rollovers via UPDATE</title>
  </sect2>
  <para>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.</para>
  <sect2>
    <title>Converting from NSEC to NSEC3</title>
  </sect2>
  <para>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.</para>
  <sect2>
    <title>Converting from NSEC3 to NSEC</title>
  </sect2>
  <para>To do this, use <command>nsupdate</command> to
  remove all NSEC3PARAM records with a zero flag
  field. The NSEC chain will be generated before the NSEC3 chain is
  removed.</para>
  <sect2>
    <title>Converting from secure to insecure</title>
  </sect2>
  <para>To convert a signed zone to unsigned using dynamic DNS,
  delete all the DNSKEY records from the zone apex using
  <command>nsupdate</command>. All signatures, NSEC or NSEC3 chains,
  and associated NSEC3PARAM records will be removed automatically.
  This will take place after the update request completes.</para>
  <para> This requires the
  <command>dnssec-secure-to-insecure</command> option to be set to
  <userinput>yes</userinput> in
  <filename>named.conf</filename>.</para>
  <para>In addition, if the <command>auto-dnssec maintain</command>
  zone statement is used, it should be removed or changed to
  <command>allow</command> instead (or it will re-sign).
  </para>
  <sect2>
    <title>Periodic re-signing</title>
  </sect2>
  <para>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.</para>
  <sect2>
    <title>NSEC3 and OPTOUT</title>
  </sect2>
  <para>
  <command>named</command> only supports creating new NSEC3 chains
  where all the NSEC3 records in the zone have the same OPTOUT
  state.
  <command>named</command> supports UPDATES to zones where the NSEC3
  records in the chain have mixed OPTOUT state.
  <command>named</command> 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.</para>
</sect1>