DNSSEC Implementation - thakares/nx9-dns-server GitHub Wiki

DNSSEC Implementation

This page details how DNSSEC is implemented in nx9-dns-server and provides guidance on setup and maintenance.

What is DNSSEC?

DNSSEC (Domain Name System Security Extensions) adds security to the DNS protocol by providing:

  • Data origin authentication: Verifies that DNS data comes from the stated source
  • Data integrity protection: Ensures DNS data hasn't been modified in transit
  • Authenticated denial of existence: Proves that a requested DNS resource record does not exist

DNSSEC in nx9-dns-server

nx9-dns-server includes built-in support for DNSSEC:

  • Key Management: Loading DNSSEC keys from configurable paths
  • Record Signing: Automatic signing of DNS responses with RRSIG records
  • DNSKEY Records: Automatic generation of DNSKEY records for public key distribution
  • DS Records: Support for Delegation Signer records for secure delegation

Setting Up DNSSEC

1. Generate DNSSEC Key Pair

You need to create a DNSSEC key pair using BIND's dnssec-keygen tool:

# Install dnssec-keygen
sudo apt-get install bind9-dnsutils   # Debian/Ubuntu
# or
sudo yum install bind-utils           # CentOS/RHEL

# Generate a 2048-bit RSA key
dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com

This command generates two files:

  • Kexample.com.+008+12345.key (public key)
  • Kexample.com.+008+12345.private (private key)

Where 12345 is a randomly generated key tag.

2. Configure nx9-dns-server

Set the DNSSEC_KEY_FILE environment variable to point to the public key file:

export DNSSEC_KEY_FILE="/path/to/Kexample.com.+008+12345.key"

For a systemd service, add this to your service file:

Environment="DNSSEC_KEY_FILE=/var/nx9-dns-server/Kexample.com.+008+12345.key"

3. Key Preprocessing (Optional)

If needed, preprocess the key file for compatibility:

sudo chmod +x /var/nx9-dns-server/preprocess-key.sh
sudo -u dnsuser /var/nx9-dns-server/preprocess-key.sh

4. Restart the Server

After configuring the key file, restart nx9-dns-server:

sudo systemctl restart dns-server.service

5. Verify DNSSEC Setup

Check that DNSSEC is working correctly:

# Using the diagnostic script
bash scripts/dnscheck.sh

# Or manually
dig @localhost example.com DNSKEY +dnssec
dig @localhost example.com A +dnssec

You should see RRSIG records in the response, indicating that DNSSEC is active.

Understanding DNSSEC Records

DNSKEY Records

DNSKEY records contain the public key used to verify signatures. nx9-dns-server automatically generates DNSKEY records from your configured key file.

Example DNSKEY record:

example.com. 3600 IN DNSKEY 257 3 8 AwEAAZ...

RRSIG Records

RRSIG (Resource Record Signature) records contain digital signatures for DNS records. nx9-dns-server automatically generates these signatures.

Example RRSIG record:

example.com. 3600 IN RRSIG A 8 2 3600 20230615000000 20230515000000 12345 example.com. HGds...

DS Records

DS (Delegation Signer) records are placed in the parent zone to establish a chain of trust. After generating your DNSSEC keys, you need to create and submit DS records to your parent zone (typically your domain registrar).

Generate DS records with:

dnssec-dsfromkey Kexample.com.+008+12345.key

Example DS record:

example.com. IN DS 12345 8 2 8D18...

DNSSEC Key Management

Key Rotation

For security, DNSSEC keys should be rotated periodically (typically annually). To rotate keys:

  1. Generate a new key pair:

    dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com

  2. Update the DNSSEC_KEY_FILE environment variable to point to the new key.

  3. Restart nx9-dns-server.

  4. Generate new DS records and submit them to your parent zone.

  5. After the parent zone updates and the TTL expires, you can safely retire the old key.

Key Security

Protect your DNSSEC keys:

  • Keep private key files (*.private) secure and with restricted permissions
  • Only the public key file (*.key) should be accessible to nx9-dns-server
  • Consider using hardware security modules (HSMs) for key storage in high-security environments
  • Maintain secure backups of all key material

Troubleshooting DNSSEC

Common Issues

  1. Missing RRSIG records

    • Check that DNSSEC_KEY_FILE is set correctly
    • Verify the key file is readable by the nx9-dns-server process
    • Check server logs for DNSSEC-related errors

  2. DNSSEC validation failures

    • Ensure the correct key is being used
    • Check that SOA serial numbers are up-to-date
    • Verify parent zone DS records match your DNSKEY

  3. Performance issues

    • DNSSEC adds overhead; consider increasing cache settings
    • For high-volume servers, more powerful hardware may be needed

Debugging Tools

# Check DNSKEY records
dig @localhost example.com DNSKEY

# Verify DNSSEC chain
dig @localhost example.com A +dnssec +trace

# Check signature expiration
dig @localhost example.com SOA +dnssec | grep RRSIG

Future DNSSEC Enhancements

Planned DNSSEC features for nx9-dns-server:

  • Automated key rotation
  • Multiple signing keys (ZSK/KSK separation)
  • NSEC3 support for better privacy
  • Web UI for DNSSEC management
  • Real-time signature monitoring

References