S3 Bucket Policy for all files public read: http://awspolicygen.s3.amazonaws.com/policygen.html

public_read.json

{
  "Id": "Policy1407525880036",
  "Statement": [
    {
      "Sid": "Stmt1407525872165",
      "Action": [
        "s3:GetObject"
      ],
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::$BUCKET_NAME/*",
      "Principal": {
        "AWS": [
          "*"
        ]
      }
    }
  ]
}