Solving the AWS ACM Certificate Validation Challenge with Terraform

Learn how to effectively manage AWS ACM certificate validation with Terraform by avoiding dependency issues and ensuring seamless DNS integration.
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This video is based on the question https://stackoverflow.com/q/72576096/ asked by the user 'ilrock' ( https://stackoverflow.com/u/5895099/ ) and on the answer https://stackoverflow.com/a/72576234/ provided by the user 'Mark B' ( https://stackoverflow.com/u/13070/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Introduction

When working with AWS and Terraform, managing resources such as SSL certificates can sometimes lead to complications—especially when it comes to validation. One common issue that developers encounter is the struggle to retrieve the necessary CNAME record for validation of AWS ACM certificates. If you're stuck in a situation where your Terraform plan hangs during validation, this guide will guide you through understanding the problem and proposing an effective solution.

Understanding the Problem

You may have encountered a scenario similar to this:

You have defined a media_certificate module in your Terraform script, which creates an AWS ACM certificate.

Upon running terraform apply, the module gets stuck at the validation stage, waiting for the certificate to be validated.

The process ultimately fails after a considerable amount of time, typically due to the absence of the required CNAME record in your DNS settings.

The CNAME record is crucial for confirming domain ownership, allowing AWS to finish the validation process. Unfortunately, Terraform doesn't automatically manage DNS records for your specific provider, leading to the issue you're experiencing.

Key Observations

The certificate validation is pending because the CNAME record needs to be added manually on your DNS provider.

Attempting to output domain_validation_options directly from the module results in an error, as this information is not accessible until after the resource is applied.

Solution Overview

To tackle this problem, it's essential to reconsider how you're managing certificate validation within Terraform:

Avoid Unnecessary Certificate Validation Resource Creation:

Terraform should not finalize the ACM certificate validation without also creating the corresponding DNS records.

Extract CNAME Information Before Validation:

Instead of trying to use an output directly, implement a way to retrieve that information beforehand, which can then be manually added to your DNS provider.

Step-by-Step Solution

1. Modify the media_certificate Module

In your media_certificate/main.tf, you should separate the creation of the certificate and its validation by avoiding the use of aws_acm_certificate_validation until after you have successfully set up the necessary DNS records. Here’s what that could look like:

[[See Video to Reveal this Text or Code Snippet]]

2. Output the Necessary Validation Information

You can create an output resource outside of the aws_acm_certificate_validation, which will give you the required CNAME data:

[[See Video to Reveal this Text or Code Snippet]]

This output will provide the necessary information regarding the CNAMEs required for validation.

3. Manually Add CNAME Records

Once you retrieve the CNAME output after running terraform apply, you will need to manually add those records into your DNS provider. This is important as it allows AWS to validate your certificate ownership effectively.

4. Create the Validation Resource After CNAME Addition

After you have added the CNAME records, you can now safely implement the aws_acm_certificate_validation resource:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Although it may seem like a hurdle, managing AWS ACM certificate validation with Terraform requires careful thought regarding how resources interact. By ensuring that Terraform properly handles the output of CNAME records and separating the validation process, you can successfully navigate through the complexities of DNS management.

If you follow these steps, you'll not only streamline your certificate validation process but also avoid unnecessary errors during your deployment workflow. As always, happy coding!

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