Solved: ACME error: 429 Too Many Requests | Let’s Encrypt

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The error message “urn:ietf:params:acme:error:rateLimited” indicates that you have exceeded the rate limits imposed by the ACME (Automated Certificate Management Environment) server. ACME is the protocol used by Let’s Encrypt to automate the process of obtaining and renewing SSL/TLS certificates.

Reasons for Let’s Encrypt Rate Limits

Let’s Encrypt imposes rate limits to regulate the number of certificate requests that an entity can make within a specific time period. These rate limits are in place for several important reasons:

  • Prevention of Abuse:
    One of the primary reasons for rate limits is to prevent abuse of the Let’s Encrypt service. Without rate limits, malicious actors could flood the service with a high volume of certificate requests, leading to resource exhaustion, service degradation, and potential denial of service for legitimate users.
  • Resource Management:
    Let’s Encrypt operates on shared infrastructure, and the rate limits help manage the resources efficiently. By placing constraints on the frequency and volume of certificate requests, Let’s Encrypt ensures fair usage and allocates resources effectively among all users.
  • Encouragement of Automation Best Practices:
    Let’s Encrypt encourages automation for certificate issuance and renewal. Rate limits promote the development and implementation of efficient automation scripts by discouraging manual, repetitive processes. Automation not only benefits the users by simplifying certificate management but also aligns with Let’s Encrypt’s mission to make HTTPS adoption widespread.
  • Enhancement of Security:
    Rate limits contribute to the overall security of the Let’s Encrypt infrastructure. They help mitigate the impact of potential security threats, such as automated attacks attempting to obtain numerous certificates in a short period. By limiting the rate at which certificates can be issued, Let’s Encrypt adds an additional layer of protection against certain types of attacks.

Types of Let’s Encrypt Rate Limits

Let’s encrypt imposes various rate limits and these are:

Certificates Per Registered Domain (50 per week)

The limit for the number of certificates issued for a single registered domain is 50 per week. This includes both new certificates and renewals. This rate limit is designed to encourage users to use a single certificate for multiple subdomains through wildcard certificates.

Duplicate Certificate (5 per week)

There is a limit of five duplicate certificates per week. This limit is in place to prevent unintentional misconfigurations or abuse.

Failed Validation (5 failures per account per hour)

If a user encounters validation failures repeatedly, there is a rate limit to prevent excessive retries. This limit is set at five failures per account per hour.

New Accounts (20 per IP address per 3 hours)

The creation of new accounts is limited to 20 per IP address every three hours. This limit helps prevent automated account creation for malicious purposes.

How to fix the rate limit-related errors in Let’s Encrypt

Here are some of the steps you can take to resolve rate limit-related errors in Let’s Encrypt:

Wait for the Rate Limit to Reset:

The most straightforward solution is to wait until the rate limit resets. The duration varies depending on the specific limit that was exceeded. Refer to the Let’s Encrypt Rate Limits page for details.

Review Automation Scripts

Check your automation scripts for any misconfigurations or bugs that might be causing an excessive number of certificate requests. Ensure that your scripts are correctly configured and follow best practices.

Space Out Certificate Requests

If you’re hitting rate limits due to a high volume of requests, consider spacing them out over time. This helps distribute the load on the Let’s Encrypt servers and prevents rate limit breaches.

Implement Exponential Backoff

Enhance your retry logic by implementing exponential backoff. If a certificate request fails, introduce progressively longer wait times before retrying. This approach helps avoid rapid retries that might contribute to rate limit issues.

Use Let’s Encrypt Staging Environment

Utilize the Let’s Encrypt staging environment during development and testing. The staging environment has higher rate limits, allowing you to perform tests without hitting production limits. Once your implementation is stable, switch to the production environment.

Contact Let’s Encrypt Support

If you believe the rate limits are impacting your legitimate use case, reach out to Let’s Encrypt support for assistance. They can provide guidance and may adjust your rate limits based on your specific needs.

Check Certificates Issued

Review the number of certificates issued for the specific domain. If you’ve reached the limit, wait until the rate limit resets.

Reuse Certificates

Instead of issuing new certificates, consider reusing existing ones. Let’s Encrypt allows up to 100 domain names per certificate, including subdomains. Use wildcard certificates or include multiple domains in a single certificate to stay within the limits.

Optimize Certificate Renewals

Ensure that your certificate renewal process is optimized. Use automated renewal tools provided by Let’s Encrypt, and avoid unnecessary or frequent renewals.

Increase Rate Limit by Using Multiple Accounts

If necessary, you can create multiple accounts and distribute certificate issuance across these accounts. Be mindful of the new accounts rate limit and use this approach judiciously.

Following the above steps can potentially help you to address the rate limit-related errors in Let’s Encrypt and maintain a smooth certificate issuance and renewal process.

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