This is the permission you need to set with Amazon AWS S3 to provide full access to a "mybucket" bucket and read-access only to all your buckets.

S3permission

{
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "S3:*",
      "Resource": "arn:aws:s3:::mybucket/*",
      "Condition": {}
    },
    {
      "Effect": "Allow",
      "Action": [
        "s3:ListBucket"
      ],
      "Resource": "arn:aws:s3:::mybucket",
      "Condition": {}
    },
    {
      "Effect": "Allow",
      "Action": "s3:ListAllMyBuckets",
      "Resource": "arn:aws:s3:::*"
    }
  ]
}