Example of a policy applied to a back up user in amazon AWS for the script https://gist.github.com/nicholasdunbar/0f9bc264fe8eaa95cd7f (only use s3:DeleteObject on your back up bucket if you have versioning turned on)

policyExampleAwsUtil.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "Stmt1426742219000",
            "Effect": "Allow",
            "Action": [
                "s3:AbortMultipartUpload",
                "s3:GetObject",
                "s3:GetObjectAcl",
                "s3:GetBucketPolicy",
                "s3:GetBucketAcl",
                "s3:GetObjectVersion",
                "s3:ListBucket",
                "s3:ListBucketMultipartUploads",
                "s3:ListMultipartUploadParts"
            ],
            "Resource": [
                "arn:aws:s3:::example-of-a-bucket-name",
                "arn:aws:s3:::example-of-a-bucket-name/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "s3:AbortMultipartUpload",
                "s3:GetObject",
                "s3:GetObjectAcl",
                "s3:GetBucketPolicy",
                "s3:GetBucketAcl",
                "s3:GetObjectVersion",
                "s3:ListBucket",
                "s3:ListBucketMultipartUploads",
                "s3:ListMultipartUploadParts",
                "s3:PutObject",
                "s3:DeleteObject"
            ],
            "Resource": [
                "arn:aws:s3:::example-of-a-backup-bucket-name",
                "arn:aws:s3:::example-of-a-backup-bucket-name/*"
            ]
        }
    ]
}