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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
> 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
</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
> 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
</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 <zonename></command> or
<command>rndc loadkeys <zonename></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>