Forgive me if I'm wrong, but it appears that the ListAllMyBuckets permission is only used to perform a login check when validating the form: https://github.com/jenkinsci/s3-plugin/blob/1feed0d956cf6eeff24306028d76e765ee997547/src/main/java/hudson/plugins/s3/S3BucketPublisher.java#L494

If the permission is not actually required when publishing to S3 then can we make this optional? For security reasons, we'd like to limit S3 access to a specific bucket and not allow the plugin to access our full list of buckets.