Determining Minimum AWS Permissions for Terraform Configurations

TLDR

To determine the minimum AWS permissions for a Terraform configuration, use tools like AWS IAM Access Analyzer or Terraform's plan and apply logs. Start with least privilege and add permissions incrementally based on errors or logs.

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Granting the minimum necessary permissions to Terraform is a best practice for enhancing security and compliance. This guide will show you how to identify and configure the least privilege permissions required for your Terraform configurations.

Why Use Least Privilege?

• Security: Reduces the risk of unauthorized access or accidental changes.
• Compliance: Helps meet regulatory requirements for access control.
• Cost Management: Prevents unintended resource creation or modification.

Steps to Determine Minimum Permissions

To determine the minimum AWS permissions required for your Terraform configurations, follow these steps:

Step 1: Analyze Terraform Actions

Review your Terraform configuration to identify the AWS services and actions it interacts with. For example, if you're creating an S3 bucket, you'll need permissions for s3:CreateBucket and s3:PutBucketPolicy.

Step 2: Use AWS IAM Access Analyzer

AWS IAM Access Analyzer can help you identify the permissions required for your Terraform configuration.

1. Enable Access Analyzer in the AWS Management Console.
2. Run your Terraform configuration.
3. Review the findings to identify the actions performed by Terraform.

Step 3: Start with Least Privilege

Create an IAM policy with the minimum permissions required. For example, if your configuration only creates an S3 bucket, your policy might look like this:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["s3:CreateBucket", "s3:PutBucketPolicy"],
      "Resource": "*"
    }
  ]
}

Step 4: Use Terraform Logs

Run terraform plan and terraform apply to identify any missing permissions. Terraform will log errors if it lacks the necessary permissions.

Step 5: Refine Permissions

Update your IAM policy based on the errors or logs. Repeat this process until Terraform runs without errors.

Best Practices

• Use Service-Specific Roles: Create separate IAM roles for different Terraform configurations.
• Limit Wildcards: Avoid using * in actions or resources unless absolutely necessary.
• Enable Logging: Use AWS CloudTrail to monitor API calls made by Terraform.
• Test in Non-Production: Validate your permissions in a non-production environment before applying them to production.

By following these steps, you can determine the minimum AWS permissions required for your Terraform configurations, enhancing security and compliance while maintaining functionality.