AWS CloudFormation and IAM Service Roles

CloudFormation allows the use of service roles, which are IAM roles created specifically for CloudFormation to manage stack resources on your behalf.

Key Points:

• Service Roles: IAM roles dedicated to CloudFormation to create, update, and delete stack resources.
• Least Privilege Principle: Users can manage stack resources without having direct permissions on the resources themselves.
• IAM PassRole Permission: Users must have this permission to allow CloudFormation to assume the service role.

Use Case:

• To allow users to manage stack resources without granting them full access to the actual resources.

How to Create and Use an IAM Service Role with CloudFormation:

1. Create a Service Role:
   • Navigate to IAM and go to the roles section.
   • Create a new role for the AWS service CloudFormation.
   • Assign appropriate permissions (e.g., S3 full access for S3 resources).
2. Naming the Role:
   • Example name: DemoRole for CFN with S3 capabilities.
   • This role allows CloudFormation to manage Amazon S3 resources.
3. Using the Role in CloudFormation:
   • When creating a stack in CloudFormation, select the option to specify an IAM role.
   • Choose the created service role (e.g., DemoRole for CFN with S3 capabilities).
   • The role will be used for all operations on the stack.

Example Scenario:

• If the stack is designed to create an EC2 instance but the service role only has S3 permissions, the stack creation will fail due to insufficient permissions.

Conclusion:

• IAM roles for CloudFormation enable fine-grained access control and adherence to the least privilege principle for stack resource management.
• Users should ensure that the service role has all the necessary permissions for the resources that the CloudFormation stack will manage.