Ispmanager 6 lite, pro, host documentation

DNSSEC configuration

DNSSEC is a set of security extensions to DNS that provides the means for authenticating DNS records. It allows preventing malicious activities like cache poisoning, phishing, and other attacks.

How it works

The purpose of DNSSEC is to protect Internet clients from counterfeit DNS data by verifying digital signatures embedded in the data. DNSSEC creates a specific record with a digital signature for every resource record. The key peculiarity of a digital signature is the use of public key cryptography to ensure that DNS records are authentic. Every member of the system can check the signature, however only those having the secret key can sign new or modified data.

Public keys are published as a DNSKEY resource record along with other resource records. A sequence of records that identifies public keys is called a chain of trust. The key authenticity is checked with its digests (fingerprint, hashes) that are sent to the parent zone as DS-records. Digests of the parent zone public keys are also sent to the corresponding parent zones. The chain of trust is built up to the root zone which public key and digests are published in the official documents of ICANN.

DNSSEC uses 2 types of keys:

  • ZSK (Zone Signing Key) — this key is used to sign records within the zone;
  • KSK (Key Signing Key) — this key is used to sign keys.

Normally, KSK uses larger values of the key length and update period than ZSK. A ZSK-key is used every time the domain zone is modified or updated. Using a short key makes it easier to sing a domain, and a short update period ensures a high level of security. KSK-keys are used only to sign the keys, that's why they are used not so often as ZSK. A long key does not affect the efficiency. Besides, it is safe to specify a long update period for a long key. A long update period of KSK-keys allows sending DS-records to the parent zone more rarely.

To avoid DNSSEC key compromising, the keys are updated. According to the standard practice, the keys are updated in steps so that slave servers and DNS caching servers have enough time for synchronization with the primary DNS server.

KSK key update procedure includes the following steps: 

  1. DS-records of a new KSK-key is published in the parent zone. In ISPmanager the next KSK-key is created right after the domain is signed or the old KSK-key is removed. A user may publish the DS-record of the new key beforehand. To update the KSK-key correctly in ISPmanager, you need to publish the DS-record of the new key in the parent zone one month before the KSK-key is updated.
  2. Changing the KSK-key. The active KSK-key is changed into a new one. In ISPmanager the key is changed 2 weeks before the KSK-key is updated.
  3. Removing DS-records of the old key from the parent zone. ISPmanager generates a new key allowing users to perform the required operations in the parent zone: delete the DS-record of the old key and add the DS-records of a new key.

ZSK key update procedure includes the following steps: 

  1. Creating and publishing a new ZSK-key in the domain zone. This operation is performed in ISPmanager 2 weeks before the key is changed. A new key is not used for signing the domain.
  2. Changing the ZSK-key. A newly published ZSK-key is get activated. The old ZSK-key is no longer used for signing domains.
  3. Deleting the old passive ZSK-key. This operation is performed 2 weeks after the ZSK-key was changed.
When you set up DNSSEC, the package size will be enlarged.  When exceeding 512 bytes, DNS will use TCP. Some routers do not allow to run DNS through TCP (port 53 is closed).When the package size exceeds the MTU limit, DNS will be filtered. MTU is the maximum transmission unit of one package that can be transmitted without fragmentation. The optimum MTU size is 1500 bytes.
Some domain name registrars require that spaces be removed from the created keys when publishing DS records.

Activate DNSSEC

DNSSEC can be activated for the following DNS-servers:

  • Bind 9.8.4 and later;
  • PowerDNS 3.2 and later.
PowerDNS up to version 4 does not fully support CAA-records. So, signing a domain name with DNSSEC on a DNS-server with PowerDNS before version 4 can make CAA-records inaccessible.

To enable DNSSEC and configure the domain key settings:

1.Navigate to Main menu→  Domain names (DNS).  

2. In the form that opens click Default settings.

3. Enable the DNSSEC support checkbox.

4. Configure the newly appeared sections Key signing key (KSK) and Zone signing key (ZSK)

  • Algorithm – algorithm used to generate a key;
  • Key length – number of bits in the key;
  • Renewal period – time (in months) of key update, after which a new key will be generated.
5. Click Save.

Disable DNSSEC

Before disabling DNSSEC you need to delete DS-records of all signed domain from their parent zones. Otherwise, the domains will stop working.

1. To disable DNSSEC navigate to Main menu→  Domain names(DNS) → Default settings 

2. Clear the DNSSEC support checkbox.

3. Click Save.

For more details, see the article Install and configure a DNS server. After saving, all domains are unsubscribed and all their keys are deleted.

Email notifications

When activating DNSSEC protection you need to publish and update the DS-record in the parent zone manually. DNSSEC email notifications will inform you about new DS-records you need to publish.

  1. In the Main menu choose Settings.
  2. From the drop-down list select Notifications.
  3. Find the Notifications settings section.
  4. Enable the  DNSSEC notifications checkbox.
  5. Click Save.

Enable DNSSEC for a domain

DNSSEC activation involves several steps:

  • the system checks the maximum TTL in the domain zone;
  • signs the domain zone;
  • generates a chain of trust.

Checking the maximum DNS TTL

The maximum DNS TTL must be less than 2 weeks. The default value is 3 hours.

1. To set the maximum TTL, navigate to the Main menu→  Domain names (DNS) → select a domain → Manage DNS Records 

 2. Check the TTL, sec. value, make changes if needed.

The default zone TTL is 1 hour (3600 seconds).

Signing domain zone

1. To sign a domain zone, go to Main menu →  Domain names (DNS).

2. In the form that opens, select the appropriate domain name and click the Edit button.

3. Enable the Sign domain checkbox.

4. Click Save.

If the domain zone is successfully signed, the icon will change to 

DNSSEC button becomes available for the domain and "There are unpublished DS records" banner is displayed.

Creating a chain of trust

To create a chain of trust, you need to transfer DS-records (or even DNSKEY-records KSK, depending on a registrar) into the parent zone.

You can see the information about the main key parameters and their DNSKEY and DS records in Main menu →  Domain names (DNS) → select a domain → DNSSEC.

The following data are displayed for every DS-record:

  • Start of record — beginning of the DS-record;
  • Tag — KSK-key identifier;
  • Algorithm — encryption digest identifier;
  • Digest type — digest type identifier;
  • Digest — digest content.

Show DNSKEY — click the button to see a table with DNSKEY-records. The following data are shown for every record DNSKEY-record:

  • Start of record — beginning of the DNSKEY-record;
  • Flags — key type identifier;
  • Protocol — DNSSEC protocol number;
  • Algorithm — encryption algorithm identifier;
  • Public key — public part of the key;
  • Tag — KSK-key identifier.

DS-records are sent in one of the following ways:

  1. Add records in the domain control panel interface on a registrar side. You need to copy the DS-records from ISPmanager. If records should be added in the form of strings on the registrar side, you need to group the values of all columns of the DS-record table in ISPmanager. Do not forget to add spaces between them.
  2. If the domain zone is located along with the parent zone on the same sever managed by ISPmanager or DNSmanager, on the*"DNSSEC parameters"* page you will see the "Send DS-records to the parent zone" button. Click the button to pass the DS-records.
  3. If the domain is the parent for the domain on the remote server, DS-records of the child domain will be created on the parent the same way as other resource records.

Once a week, ispmanager checks DS-records in the parent zone. At least one DS-record for every KSK must be sent. Once completed, the warning in the Status column in  Domain names (DNS) will change into the icon  confirming that the domain is protected with DNSSEC.  

Disable DNSSEC for a domain

If the keys are compromised, you need to sign the domain zone with new keys. To do so, disable DNSSEC protection:

  • delete all the DS-records from the parent domain zone and wait for several hours;
  • delete the domain signature in Main menu → Domain names  (DNS)→  select a domain → menu Edit →  Delete sign.
  • Click Save.