Troubleshooting AWS Certificate Manager: Common Pitfalls

AWS Certificate Manager (ACM) simplifies the process of managing SSL/TLS certificates for AWS services. However, encountered problems can stall your setup, impacting performance and security. In this blog post, we will explore some common pitfalls when using ACM and how to effectively troubleshoot them.

Understanding AWS Certificate Manager

Before we delve into troubleshooting, it’s essential to understand that AWS Certificate Manager helps to:

Issue and manage SSL/TLS certificates.
Automate certificate renewals.
Integrate seamlessly with services like Elastic Load Balancing, Amazon CloudFront, and more.

For a detailed overview, you can refer to the official AWS Certificate Manager documentation.

Why Use AWS Certificate Manager?

Cost-Effective: ACM provides free public SSL/TLS certificates.
Automatic Renewals: Reduces the workload of managing certificate renewals.
Easy Integration: Works effortlessly with other AWS services.

Common Pitfalls in AWS Certificate Manager

While ACM is designed to be user-friendly, here are a few common pitfalls and how to troubleshoot them effectively.

1. Domains Not Validated

One of the primary requirements in ACM is to validate your domain ownership. If your domain hasn't been validated, certificates won't be issued.

Troubleshooting Steps:

Check for Domain Validation: Navigate to ACM in the AWS Management Console. If the status shows "Pending validation," action is required.
Use the Right Validation Method: ACM supports two validation methods:
- Email Validation: An email is sent to predefined addresses listed in the WHOIS record.
- DNS Validation: A CNAME record must be added to your DNS configuration.

Choose a validation type and follow the respective steps carefully. For instance, if choosing DNS validation:

# Sample DNS CNAME Record
Name: _abc123.yourdomain.com
Value: _xyz456.acm-validations.aws
TTL: 300

Using DNS validation is often preferred for its automated renewal capability. Ensure to check for DNS propagation after adding the CNAME record, using tools like DNS Checker.

2. Certificate Not in the Correct Region

AWS services are region-specific; thus, your certificates should also be.

Troubleshooting Steps:

Check Region: Ensure you are requesting the certificate in the same region where your resources (like Elastic Load Balancers, CloudFront distributions) are deployed. The region dropdown in the ACM console displays the certificates available in that region.

3. Using Imported Certificates

If you’re using imported certificates instead of certificates issued by ACM, there can be issues like the certificate not being correct or not matching the private key.

Troubleshooting Steps:

Check Certificate and Key Compatibility: Ensure the certificate matches with the private key you uploaded. Using OpenSSL can help verify this:

# Verify Certificate
openssl x509 -noout -modulus -in your_certificate.crt | openssl md5
openssl rsa -noout -modulus -in your_private.key | openssl md5

Both commands should return the same hash value.

4. Misconfigured Apache or NGINX

For EC2 instances running web servers like Apache or NGINX, misconfigured virtual hosts can lead to SSL errors.

Troubleshooting Steps:

Check SSL Configuration: Ensure that the virtual host configuration points to the correct certificate files. Here’s a sample configuration for NGINX to illustrate:

server {
    listen 443 ssl;
    server_name yourdomain.com;

    ssl_certificate /etc/ssl/certs/your_certificate.crt;
    ssl_certificate_key /etc/ssl/private/your_private.key;

    location / {
        proxy_pass http://backend_server;
    }
}

In this configuration, ensure that the paths to ssl_certificate and ssl_certificate_key are correct, as failure to correctly specify the paths would result in server errors.

5. Certificate Chain Issues

A common error that leads to SSL warnings in your browser is an incomplete certificate chain.

Troubleshooting Steps:

Install Intermediate Certificates: Make sure the intermediate certificates are included. When using NGINX, this could be added like this:

ssl_certificate /etc/ssl/certs/your_certificate_bundle.crt; # Include chain

If you're using Apache, the following directive ensures you are addressing the chain:

SSLCertificateChainFile /etc/ssl/certs/intermediate.crt

6. Mismatch Between Domain Name and Certificate

If you try accessing a domain that does not match any of the Subject Alternative Names (SAN) in the SSL certificate, it will result in a security warning.

Troubleshooting Steps:

Check the SAN: When creating or importing a certificate, ensure that the exact domain name and subdomains you intend to cover are included.
You can use the OpenSSL command to check your certificate:

openssl x509 -in your_certificate.crt -text -noout

Look for the 'Subject Alternative Name' field to ensure your desired domains are listed.

Additional Resources

Check the AWS documentation on ACM for comprehensive troubleshooting procedures.
Utilize the AWS Support forums to ask questions or search for solutions provided by the community.

Summary

AWS Certificate Manager is a powerful tool, and while issues may arise, most can be easily rectified through careful troubleshooting. Remember to validate your domain correctly, check your certificates, and ensure proper configurations in your web servers. By avoiding common mistakes outlined in this blog, you’ll be able to manage your SSL/TLS certificates more effectively and ensure a secure user experience.

By proactively addressing each of these common pitfalls, you ensure a smoother deployment, reduced downtime, and a more professional presentation of your applications online. Start implementing these solutions today and maintain a secure web presence efficiently.