How to Use Cross Account IAM Role

Cross account IAM roles allow you to grant access to resources in one AWS account to a user or resource in another AWS account. This is useful for scenarios where you have multiple AWS accounts and need to share resources between them.

To use cross account IAM roles, follow these steps:

1. Create an IAM role in the account that owns the resource you want to share. This is known as the resource account ACCOUNT B.
2. Define a trust policy for the role that allows the account you want to share the resource with to assume the role. The trust policy should include the AWS account ID of the account that will assume the role ACCOUNT A.
3. Attach a policy to the role that grants permissions to the resource you want to share.
4. Share the IAM role with the account that needs access to the resource . To do this, create a role in the account that needs access ACCOUNT A, and define a trust policy that allows it to assume the cross account IAM role.
5. Use the cross account IAM role to access the shared resource.

By following these steps, you can easily share resources between AWS accounts using cross account IAM roles.

If you want to know more, I have prepared a video in which I explain everything step by step. I am creating 2 IAM roles in 2 different AWS accounts and one lambda function that can use a role from another AWS account. The lambda function can add, remove, change and do other cool things in a completely different AWS account.