What Is the ACME Protocol?

Quick Overview

The Automated Certificate Management Environment (ACME) protocol is a standardized way to automate the process of obtaining and renewing SSL/TLS certificates. It allows web servers to prove ownership of domains and receive certificates without manual intervention. ACME automates certificate issuance and renewal, improves website security, reduces human error in certificate management, and is widely supported by certificate authorities and web servers.

Understanding ACME

The ACME protocol, an open standard designed to automate the process of issuing and renewing digital certificates, has revolutionized certificate management. Developed to streamline the entire process, ACME has been widely adopted by many Certificate Authorities (CAs) and has become an internet standard (RFC 8555).

Before ACME, obtaining and managing SSL/TLS certificates was often a manual, time-consuming process. Website administrators had to:

1. Generate a Certificate Signing Request (CSR)
2. Prove domain ownership through various methods
3. Submit the CSR to a Certificate Authority
4. Wait for approval and certificate issuance
5. Manually install the certificate on their web server
6. Remember to renew the certificate before it expired

This process was prone to human error and often resulted in expired certificates, leading to security warnings for website visitors.

ACME automates this entire process by defining a standard protocol for communication between web servers and Certificate Authorities. The web server (ACME client) sends a request to the CA (ACME server) for a certificate for a specific domain. The CA then challenges the client to prove ownership of the domain, usually by placing a specific file on the web server. Once the CA verifies the challenge completion, it issues the certificate to the client, which automatically installs it. This process can be fully automated, allowing for easy initial setup and seamless renewals.

Benefits of Using ACME

The ACME protocol offers numerous advantages for website owners and administrators:

• Automation: It significantly reduces manual intervention in certificate management.
• Improved Security: Regular, automatic renewals ensure certificates are always up-to-date.
• Cost-Effectiveness: Many ACME-compatible CAs offer free or low-cost certificates.
• Reduced Errors: Automation minimizes the risk of human errors in the certificate process.
• Scalability: It allows for easy management of certificates for multiple domains or subdomains.
• Standardization: As an open standard, ACME promotes interoperability between different systems.

Implementing ACME

To start using ACME for your websites, follow these steps:

1. Choose an ACME Client: Select a client that is actively maintained, well-documented, supports your operating system and web server, and offers the features you need (e.g., wildcard certificates, multiple domain support).
2. Install the ACME Client: The installation process varies depending on your chosen client and system. You might use a package manager, download the client directly from the developer’s website, or clone a repository and build the client from source. Always refer to the official documentation of your chosen ACME client for specific installation instructions.
3. Configure the Client: Set up your ACME client with your domain details and preferred settings. This usually involves specifying the domain(s) you want to secure, the web server you’re using (e.g., Apache, Nginx), and where to store the certificates.
4. Request a Certificate: Run your ACME client to initiate the certificate request process. The client will generate a certificate signing request, prove domain ownership to the CA, and receive and install the certificate.
5. Configure Your Web Server: While most ACME clients will automatically configure your web server to use the new certificate, you may need to make some manual adjustments depending on your setup. For Apache, ensure your virtual host configuration includes the paths to your new certificate files. For Nginx, update your server block with the paths to the new certificate and key files.
6. Set Up Automatic Renewal: ACME certificates typically have short lifespans (often 90 days) to encourage frequent renewals and improve security. Set up automatic renewals to ensure your certificates stay current. Most ACME clients offer built-in renewal mechanisms, and you can typically set up a cron job or scheduled task to run the renewal process regularly.

Advanced ACME Features

ACME supports issuing wildcard certificates, which secure a domain and all its subdomains. To request a wildcard certificate, you typically need to use DNS challenges for domain validation. Additionally, ACME provides a standardized way to revoke certificates if they are compromised or no longer needed.

Troubleshooting Common ACME Issues

When implementing ACME, you might encounter some common issues:

• Rate Limiting: Be aware of rate limits imposed by most ACME CAs to prevent abuse.
• Connectivity Issues: Ensure your server can communicate with the ACME CA’s servers; check firewall rules if you encounter connection problems.
• Domain Validation Failures: Misconfigured web servers can prevent successful domain validation, so make sure your server is correctly serving challenge responses.
• DNS Challenges: For DNS-based challenges, ensure your DNS records are correctly set up and propagated.
• Permission Errors: ACME clients often need elevated permissions to write certificates and configure web servers; use appropriate privilege elevation when necessary.

Can I use ACME to order SSL/TLS certificates from SSL.com?

Yes! Please read SSL/TLS Certificate Issuance and Revocation with ACME and ACME SSL/TLS Automation with Apache and Nginx for more information.

What is the lifetime of SSL/TLS certificates purchased from SSL.com via ACME?

All certificates issued by SSL.com via the ACME protocol have a lifetime of one year.

Which types of certificates can I order from SSL.com with ACME?

The following SSL/TLS certificate products may be ordered via the ACME protocol by any SSL.com customer:

• Basic SSL • Wildcard SSL • Premium SSL • Multi-Domain UCC/SAN SSL

For more information, please refer to the section on Certificate Types and Billing from our ACME guide.

Do SSL.com’s Reseller and Volume Purchasing discounts apply to certificates ordered with ACME?

Yes. Participants in SSL.com’s Reseller and Volume Purchasing Program will receive the wholesale discounts associated with their reseller and volume purchasing tier when they request certificates with the ACME protocol. Resellers can also generate ACME credentials for their customers.

Conclusion

The ACME protocol has revolutionized SSL/TLS certificate management, making it easier than ever to secure websites and maintain valid certificates. By automating the certificate lifecycle, ACME helps improve internet security, reduces administrative overhead, and ensures a smoother experience for both website operators and visitors.

As you implement ACME for your own websites, remember to:

• Choose a reliable ACME client compatible with your environment
• Regularly monitor your certificate status and renewal processes
• Keep your ACME client and web server software up-to-date
• Follow security best practices for storing and managing your certificates