CloudFormation Hooks - krdheeraj51/aws-labs GitHub Wiki

Overview:

AWS CloudFormation Hooks are a feature that allows you to ensure that your CloudFormation resources, stacks, and change sets comply with your organization's security, operational, and cost optimization best practices. Hooks can proactively inspect the configuration of your AWS resources before provisioning and either prevent non-compliant resources from being provisioned or emit a warning.

Key Points:

Types of Hooks:

  • Guard Hook: Evaluates resources using an AWS CloudFormation Guard rule.
  • Lambda Hook: Forwards requests for resource evaluation to an AWS Lambda function.
  • Custom Hook: Uses a custom Hook handler that you manually develop.

Use Cases:

  • Security Compliance: Verify security groups for appropriate inbound and outbound traffic rules.
  • Cost Optimization: Restrict development environments to use smaller EC2 instance types.
  • Operational Best Practices: Enforce automatic backups for RDS instances.

Creating Hooks:

  • Hooks are created and managed using the CloudFormation Command Line Interface (CFN-CLI).
  • You can register hooks in the CloudFormation registry, making it easy to distribute and activate them both publicly and privately2.

Example Workflow:

  • Initiate the Project: Generate the files needed to develop a custom Hook.
  • Develop the Hook: Write the code for the Hook handler.
  • Register the Hook: Use the CFN-CLI to register the Hook in the CloudFormation registry.
  • Test the Hook: Ensure that the Hook works as expected by testing it against sample templates.
  • Activate the Hook: Activate the Hook in your AWS account to enforce compliance1.

Example of Creating a Custom Hook

Step 1: Initiate the Project

cfn init

Step 2: Develop the Hook Write your custom logic in the generated files.

Step 3: Register the Hook

cfn submit

Step 4: Test the Hook Use sample templates to test your Hook.

Step 5: Activate the Hook Activate the Hook in your AWS account through the CloudFormation console or CLI.