If you require cross-account access to S3 buckets in multiple Amazon accounts and you use user-defined master and worker roles, set up cross-account IAM roles in AWS.
When you set up cross-account IAM roles in AWS, complete the following tasks:
Edit the policies in the user-defined worker role to access the S3 resources in each account.
Add a bucket policy to the S3 buckets in each account that permits the user-defined worker role to access the bucket.
You cannot combine cross-account access with default master and worker roles and role-based security. If your organization requires cross-account access, consider one of the following options: