# DNSSEC, Dynamic Zones, and Automatic Signing

## Converting from insecure to secure

A zone ca be changed from insecure to secure in two ways: using a dynamic DNS update, or via the `auto-dnssec` zone option.

For either method, `named` must be configured so that it can see the `K*` files which contain the public and private parts of the keys that are used to sign the zone. These files are generated by `dnssec-keygen`, and they should be placed in the key-directory, as specified in `named.conf`:

    	zone example.net {
    		type master;
    		update-policy local;
    		file "dynamic/example.net/example.net";
    		key-directory "dynamic/example.net";
    	};

If one KSK and one ZSK DNSKEY key have been generated, this configuration causes all records in the zone to be signed with the ZSK, and the DNSKEY RRset to be signed with the KSK. An NSEC chain is generated as part of the initial signing process.

## Dynamic DNS Update Method

To insert the keys via dynamic update:

    	% 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

While the update request completes almost immediately, the zone is not completely signed until `named` has had time to "walk" the zone and generate the NSEC and RRSIG records. The NSEC record at the apex is added last, to signal that there is a complete NSEC chain.

To sign using NSEC3 instead of NSEC, add an NSEC3PARAM record to the initial update request. The OPTOUT bit in the NSEC3 chain can be set in the flags field of the NSEC3PARAM record.

    	% 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

Again, this update request completes almost immediately; however, the record does not show up until `named` has had a chance to build/remove the relevant chain. A private type record is created to record the state of the operation (see below for more details), and is removed once the operation completes.

While the initial signing and NSEC/NSEC3 chain generation is happening, other updates are possible as well.

## Fully Automatic Zone Signing

To enable automatic signing, add the `auto-dnssec` option to the zone statement in `named.conf`. `auto-dnssec` has two possible arguments: `allow` or `maintain`.

With `auto-dnssec allow`, `named` can search the key directory for keys matching the zone, insert them into the zone, and use them to sign the zone. It does so only when it receives an `rndc sign <zonename>`.

`auto-dnssec maintain` includes the above functionality, but also automatically adjusts the zone's DNSKEY records on a schedule according to the keys' timing metadata. (See and for more information.)

`named` periodically searches the key directory for keys matching the zone; if the keys' metadata indicates that any change should be made to the zone - such as adding, removing, or revoking a key - then that action is carried out. By default, the key directory is checked for changes every 60 minutes; this period can be adjusted with `dnssec-loadkeys-interval`, up to a maximum of 24 hours. The `rndc loadkeys` forces `named` to check for key updates immediately.

If keys are present in the key directory the first time the zone is loaded, the zone is signed immediately, without waiting for an `rndc sign` or `rndc loadkeys` command. Those commands can still be used when there are unscheduled key changes.

When new keys are added to a zone, the TTL is set to match that of any existing DNSKEY RRset. If there is no existing DNSKEY RRset, the TTL is set to the TTL specified when the key was created (using the `dnssec-keygen -L` option), if any, or to the SOA TTL.

To sign the zone using NSEC3 instead of NSEC, submit an NSEC3PARAM record via dynamic update prior to the scheduled publication and activation of the keys. The OPTOUT bit for the NSEC3 chain can be set in the flags field of the NSEC3PARAM record. The NSEC3PARAM record does not appear in the zone immediately, but it is stored for later reference. When the zone is signed and the NSEC3 chain is completed, the NSEC3PARAM record appears in the zone.

Using the `auto-dnssec` option requires the zone to be configured to allow dynamic updates, by adding an `allow-update` or `update-policy` statement to the zone configuration. If this has not been done, the configuration fails.

## Private Type Records

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 with a non-zero initial octet have a non-zero value for the final octet.

If the first octet of a private type record is non-zero, the record indicates either that the zone needs to be signed with the key matching the record, or that all signatures that match the record should be removed. Here are the meanings of the different values of the first octet:

      algorithm (octet 1)
      key id in network order (octet 2 and 3)
      removal flag (octet 4)
      complete flag (octet 5)

Only records flagged as "complete" can be removed via dynamic update; attempts to remove other private type records are silently ignored.

If the first octet is zero (this is a reserved algorithm number that should never appear in a DNSKEY record), the record indicates that changes to the NSEC3 chains are in progress. The rest of the record contains an NSEC3PARAM record, while the flag field tells what operation to perform based on the flag bits:

      0x01 OPTOUT
      0x80 CREATE
      0x40 REMOVE
      0x20 NONSEC

## DNSKEY Rollovers

As with insecure-to-secure conversions, DNSSEC keyrolls can be done in two ways: using a dynamic DNS update, or via the `auto-dnssec` zone option.

## Dynamic DNS Update Method

To perform key rollovers via dynamic update, the `K*` files for the new keys must be added so that `named` can find them. The new DNSKEY RRs can then be added via dynamic update. `named` then causes the zone to be signed with the new keys; when the signing is complete, the private type records are updated so that the last octet is non-zero.

If this is for a KSK, the parent and any trust anchor repositories of the new KSK must be informed.

The maximum TTL in the zone must expire before removing the old DNSKEY. If it is a KSK that is being updated, the DS RRset in the parent must also be updated its TTL allowed to expire. This ensures that all clients are able to verify at least one signature when the old DNSKEY is removed.

The old DNSKEY can be removed via UPDATE, taking care to specify the correct key. `named` cleans out any signatures generated by the old key after the update completes.

## Automatic Key Rollovers

When a new key reaches its activation date (as set by `dnssec-keygen` or `dnssec-settime`), and if the `auto-dnssec` zone option is set to `maintain`, `named` automatically carries out the key rollover. If the key's algorithm has not previously been used to sign the zone, then the zone is fully signed as quickly as possible. However, if the new key replaces an existing key of the same algorithm, the zone is re-signed incrementally, with signatures from the old key replaced with signatures from the new key as their signature validity periods expire. By default, this rollover completes in 30 days, after which it is safe to remove the old key from the DNSKEY RRset.

## NSEC3PARAM Rollovers via UPDATE

The new NSEC3PARAM record can be added via dynamic update. When the new NSEC3 chain has been generated, the NSEC3PARAM flag field is set to zero. At that point, the old NSEC3PARAM record can be removed. The old chain is removed after the update request completes.

## Converting From NSEC to NSEC3

To do this, an NSEC3PARAM record must be added. When the conversion is complete, the NSEC chain is removed and the NSEC3PARAM record has a zero flag field. The NSEC3 chain is generated before the NSEC chain is destroyed.

## Converting From NSEC3 to NSEC

To do this, use `nsupdate` to remove all NSEC3PARAM records with a zero flag field. The NSEC chain is generated before the NSEC3 chain is removed.

## Converting From Secure to Insecure

To convert a signed zone to unsigned using dynamic DNS, delete all the DNSKEY records from the zone apex using `nsupdate`. All signatures, NSEC or NSEC3 chains, and associated NSEC3PARAM records are removed automatically. This takes place after the update request completes.

This requires the `dnssec-secure-to-insecure` option to be set to `yes` in `named.conf`.

In addition, if the `auto-dnssec maintain` zone statement is used, it should be removed or changed to `allow` instead; otherwise, it will re-sign).

## Periodic Re-signing

In any secure zone which supports dynamic updates, `named` periodically re-signs RRsets which have not been re-signed as a result of some update action. The signature lifetimes are adjusted to spread the re-sign load over time rather than all at once.

## NSEC3 and OPTOUT

`named` only supports creating new NSEC3 chains where all the NSEC3 records in the zone have the same OPTOUT state. `named` supports UPDATES to zones where the NSEC3 records in the chain have mixed OPTOUT state. `named` does not support changing the OPTOUT state of an individual NSEC3 record; if the OPTOUT state of an individual NSEC3 needs to be changed, the entire chain must be changed.