Introduction

In a rapidly growing cloud environment, ensuring that your resources align with organizational policies and security standards is crucial. One such measure is restricting IAM group users from launching EC2 instances with unapproved AMIs (Amazon Machine Images). By implementing Service Control Policies (SCPs) in AWS Organizations, you can enforce such restrictions effectively.

Why Enforce AMI Restrictions?

Restricting the use of unapproved AMIs ensures that all EC2 instances are created using images that meet your security, compliance, and operational standards. Unapproved AMIs might contain vulnerabilities, outdated software, or configurations that do not align with your organization’s policies.

Steps to Implement SCP Policies for AMI Restrictions

1. Create a List of Approved AMIs

Before setting up the SCP, you need a list of AMIs approved for use within your organization. Note down their AMI IDs.

2. Navigate to AWS Organizations

Log in to the AWS Management Console and navigate to the AWS Organizations service. Ensure you have the necessary permissions to create and manage SCPs.

3. Create the SCP Policy

Follow these steps to create the SCP:

  1. Go to Policies: In the left-hand menu, click on “Policies” under the “Service control policies” section.
  2. Create Policy: Click on the “Create policy” button.

Define Policy: Use the following JSON policy to restrict EC2 instance launches to approved AMIs only:

{

    “Version”: “2012-10-17”,

    “Statement”: [

        {

            “Effect”: “Deny”,

            “Action”: “ec2:RunInstances”,

            “Resource”: “arn:aws:ec2:*:*:instance/*”,

            “Condition”: {

                “StringNotEquals”: {

                    “ec2:ImageId”: [

                        “ami-0abcdef1234567890”,  // Replace with your approved AMI IDs

                        “ami-0abcdef1234567891”

                    ]

                }

            }

        }

    ]

}

  2. Name and Description: Give your policy a meaningful name, such as RestrictUnapprovedAMIs, and provide a description.
  3. Create Policy: Click on “Create policy” to save your changes.

4. Attach the SCP to the Organizational Unit (OU)

Attach the newly created SCP to the Organizational Unit (OU) containing the IAM groups or accounts you want to restrict:

  1. Navigate to OUs: In the AWS Organizations console, go to “Organizational units” in the left-hand menu.
  2. Select OU: Choose the OU to which you want to apply the policy.
  3. Attach Policy: Click on the “Policies” tab and then “Attach policy.” Select the RestrictUnapprovedAMIs policy and attach it to the OU.

Testing the Policy

To ensure the policy works as intended, attempt to launch an EC2 instance using an unapproved AMI. You should receive an error message indicating that you do not have permission to perform this action.

Conclusion

Implementing SCP policies to restrict IAM group users from launching EC2 instances with unapproved AMIs is a crucial step in maintaining security and compliance within your AWS environment. Following the steps outlined above, you can ensure all EC2 instances are launched using images that meet your organization’s standards.