json

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "MyListBucket",
      "Effect": "Allow",
      "Action": "S3:ListBucket",
      "Resource": [
        "arn:aws:s3:::com.demo.file"
      ],
      "Condition": {"StringEquals":  {"aws:username": "Bob"}}
    }
  ]
}