AWS CloudFront Custom Domain Name with HTTPS Not Working

Amazon CloudFront is a fast content delivery network (CDN) service that distributes content globally and integrates seamlessly with services like AWS S3, EC2, and Lambda. However, even with its robust infrastructure, issues can arise, especially when configuring CloudFront to work with custom domain names and secure HTTPS connections. Below is a detailed examination of why HTTPS might not work with a CloudFront custom domain name, along with potential solutions.

Understanding Custom Domain Names

Subdomains and CNAMEs

When using a custom domain with CloudFront, you generally create a CNAME (Canonical Name) DNS record pointing to your CloudFront distribution. For instance, if your CloudFront distribution's domain is `d123456789.cloudfront.net`, and you want to use `cdn.example.com`, you'll create a CNAME that resolves `cdn.example.com` to `d123456789.cloudfront.net`.

The Role of ACM Certificates

To secure a custom domain with HTTPS, you must provision an SSL/TLS certificate, ideally using AWS Certificate Manager (ACM). These certificates need to be validated and attached to your CloudFront distribution.

Common Troubleshooting Scenarios

1. DNS Misconfiguration

Problem:

The CNAME record might be incorrectly configured or not yet propagated.

Solution:

• Verify the CNAME record and ensure it points to the correct CloudFront domain.
• Use DNS lookup tools to check if the CNAME is resolving properly.

2. SSL/TLS Certificate Issues

Problem:

The SSL/TLS certificate may not be correctly configured or validated.

Solution:

• Check if the ACM certificate is correctly issued and associated with your CloudFront distribution.
• Ensure the certificate is in the `us-east-1` (N. Virginia) region as required by CloudFront.
• Revalidate and renew the certificate if necessary.

3. HTTPS Redirection Issues

Problem:

The distribution might not be set up to use HTTPS correctly.

Solution:

• In the CloudFront console, navigate to the behavior settings.
• Ensure that you have configured the `Viewer Protocol Policy` to redirect HTTP requests to HTTPS or to allow only HTTPS connections.

4. Missing or Incorrect Root CA

Problem:

The browser might not trust the root Certificate Authority (CA) used to issue the SSL certificate.

Solution:

• Use an SSL checker tool to verify the chain of trust.
• Ensure intermediate certificates and root certificates are part of the credential chain.

Step-by-Step Setup Guide

1. Provision an SSL/TLS Certificate:
   • Navigate to AWS Certificate Manager (ACM).
   • Request a public certificate for your domain (e.g., `cdn.example.com`).
   • Complete domain validation—usually done via DNS validation by adding the CNAME record ACM provides.
2. Configure Your CloudFront Distribution:
   • Navigate to the CloudFront console.
   • Create or update a distribution to include your custom domain name in the `Alternate Domain Names (CNAMEs)` field.
   • Attach the verified SSL/TLS certificate to the distribution.
3. DNS Configuration:
   • Update the DNS service hosting your domain records to add or adjust the CNAME record.
   • Verify DNS propagation using a global DNS tool.

Key Points Summary

Additional Considerations

Monitoring and Logs

• Utilize CloudFront's built-in logging to analyze request data.
• AWS CloudWatch can be used to set alarms and monitor your distribution’s performance and errors.

Security Recommendations

• Leverage AWS WAF for application-level protection and DDoS mitigation.
• Regularly review IAM permissions for resources and apply the principle of least privilege.

Advanced Settings

• Consider enabling HTTP/2 for improved speed and performance.
• If you use Lambda@Edge with CloudFront, ensure your Lambda functions are properly configured to handle HTTPS requests.

Conclusion

While there can be multiple reasons a CloudFront custom domain may not work with HTTPS, careful configuration and diligent troubleshooting will lead to successful deployment. By ensuring proper DNS records, valid SSL/TLS certificates, and correct CloudFront settings, you can achieve a secure and optimal CDN setup tailored to your requirements.