DNS-Persist-01: A New Model for DNS-Based Challenge Validation

DNS-based challenge validation is the backbone of modern certificate automation and service verification, but its core model hasn’t changed in over a decade. The introduction of DNS-Persist-01—a new model for DNS-based challenge validation—signals a pivotal shift: moving from transient, one-off TXT records to a persistent, stateful validation presence. Here’s why this change matters for DevOps, SREs, and anyone who automates domain ownership proofs.

Key Takeaways:

• DNS-Persist-01 introduces persistent DNS records for challenge validation, reducing race conditions and improving automation reliability
• Stateful validation enables continuous monitoring and auditability, but changes operational and security assumptions
• Production deployment requires changes to DNS zone management, record lifecycle, and incident response playbooks
• Security teams must balance persistent exposure with defense-in-depth, monitoring, and regular review processes

DNS-Persist-01 Fundamentals: What’s New?

The traditional DNS-01 challenge, as implemented by ACME (RFC 8555), relies on the client creating a one-time TXT record under _acme-challenge.example.com for each validation event. This record is deleted after validation—minimizing public exposure but creating reliability problems under load, high DNS latency, or aggressive caching.

DNS-Persist-01 rethinks this model by introducing a persistent TXT (or CNAME) record that remains in place throughout the certificate’s lifetime or the service’s operational window. Instead of proving control once per issuance, the client maintains an ongoing assertion of domain control. This enables:

• Continuous validation: Auditors or automated systems can verify control at any time, not just during issuance or renewal
• Reduced race conditions: No “window of vulnerability” for record propagation or late cleanup
• Improved support for multi-issuer and multi-cloud setups: Multiple authorities can check the same persistent record

This evolution was discussed at recent IETF meetings (CENTR report on IETF124), where new DNS transport signaling and cache sharing concepts were also tested for improved performance and scalability.

For a primer on DNS fundamentals and its evolution since RFC 882/1034/1035, see this technical overview.

Deploying DNS-Persist-01: Real-World Configurations

Implementing DNS-Persist-01 in production isn’t just about leaving a TXT record in place. You need to:

1. Choose a naming strategy for persistent challenge records (e.g., _persist-challenge.example.com).
2. Automate record creation and update using your DNS provider’s API or a DNS management tool.
3. Integrate validation checks into your CI/CD and monitoring pipelines.
4. Design a record rotation and revocation process for security events.

Example 1: Creating a Persistent TXT Record with CLI

# Using Cloudflare's CLI tool (cfcli) to create a persistent TXT record
cfcli dns create --zone example.com --type TXT --name _persist-challenge --content "persisted-challenge-token" --ttl 300

This command maintains a persistent challenge token. You can rotate the token by updating the --content field and propagating the change.

Example 2: Automated Validation in CI/CD (GitHub Actions)

name: Persist Challenge Validation

on:
  schedule:
    - cron: '0 * * * *' # every hour

jobs:
  validate:
    runs-on: ubuntu-latest
    steps:
      - name: Verify DNS Challenge Record
        run: |
          dig +short TXT _persist-challenge.example.com

This scheduled workflow checks the presence and value of the persistent DNS record every hour, alerting if the record is missing or incorrect.

Example 3: Revoking a Persistent Challenge Record

# Remove the persistent record in the event of key compromise or service shutdown
cfcli dns delete --zone example.com --type TXT --name _persist-challenge

Security policy should mandate immediate revocation of challenge records if credentials are compromised.

If you need more advanced DNS automation patterns, our Tailscale Peer Relays deployment guide covers robust production DNS configuration.

Practical Example: Implementing DNS-Persist-01 in a Multi-Cloud Environment

When deploying DNS-Persist-01 across multiple cloud providers, ensure that each provider supports persistent records. For instance, AWS Route 53 allows for custom TTL settings, which can be beneficial for managing persistent records. In a multi-cloud setup, you can create a centralized management script that uses APIs from different providers to maintain consistency across your DNS records.

Consider using a monitoring tool that checks the status of these records across all platforms, alerting you if any discrepancies arise. This proactive approach helps maintain domain control and ensures that your automated systems can always validate ownership.

Validation Robustness and Security Implications

Persistent DNS challenge records fundamentally change the threat model:

• Continuous Exposure: Attackers have more time to study and attempt to subvert validation records. Careful record naming and secret value rotation are essential.
• Multi-party Trust: Multi-issuer and federated environments can benefit, but must coordinate token management and auditing.
• Auditability: Persistent records support continuous compliance and are easier to monitor with standard DNS tools.

At IETF124, engineers debated the operational pros and cons of persistent validation, including its role in post-quantum cryptography and resilience against DNS cache poisoning (CENTR IETF124 report).

Security best practices include:

• Rotating challenge values at regular intervals (e.g., monthly or after major changes)
• Automating checks for unauthorized record changes
• Integrating incident response with DNS management—revoke and reissue on compromise

For a comparison to how quickly new attack vectors emerge in production, see our recent coverage of zero-day CSS vulnerabilities.

Edge Cases and Limitations

• Delegation: Some DNS providers may not support persistent custom records or may enforce TTL limits—test before deploying in production.
• Record Bloat: In multi-tenant or multi-service environments, you may accumulate many persistent records; periodic cleanup is required.
• Key Rotation: Coordination is critical—rotating persistent tokens must not break in-flight validations.

Common Pitfalls and Pro Tips

• Forgotten Records: Persistent challenge records are easy to overlook during domain transfer or decommissioning—build automated cleanup into your process.
• Over-permissive DNS Access: Restrict who and what can update persistent records. Compromised automation keys can lead to unauthorized certificate issuance.
• Monitoring Blind Spots: Integrate DNS challenge monitoring into your existing SIEM and alerting—don’t rely solely on CA logs for detection.
• Provider API Drift: DNS provider APIs change—test your automation regularly and subscribe to provider change notifications.

Teams that adopted persistent DNS records at recent IETF hackathons reported a measurable drop in failed validations and support tickets, but flagged the need for strict access controls and regular audits (CENTR IETF124).

If you’re new to DNS automation, review our production DNS relay guide for resilient, secure patterns.

Edge Case: Handling DNS Provider Limitations

Some DNS providers may impose restrictions on the types of records you can create or the TTL values you can set. For example, if a provider limits the TTL to a minimum of 3600 seconds, this could impact your ability to rotate challenge tokens quickly. Always review your provider’s documentation to understand these limitations before implementing DNS-Persist-01.

Additionally, if your provider does not support persistent records, you may need to consider switching to a more flexible DNS service that accommodates your automation needs. This decision should factor into your overall DNS strategy to ensure seamless operations.

Conclusion & Next Steps

DNS-Persist-01 offers a robust, audit-friendly model for DNS-based challenge validation, especially for enterprises juggling multiple CAs, clouds, and compliance standards.

Before switching, review your DNS provider’s capabilities and update your automation and incident response playbooks for persistent record management.

Track IETF working group discussions and emerging standards for further refinements. For more on how foundational protocols are adapting to modern automation, see our analysis of AI’s impact on production systems and cutting-edge security responses.