AWS IAMで特定のbucketにのみアクセス可能なPermissions Policy https://console.aws.amazon.com/iam/home 参考） http://blog.dateofrock.com/2011/04/s3iam.html

gistfile1.json

{
  "Statement": [
    {
      "Sid": "Stmt1355727169912",
      "Action": [
        "s3:ListAllMyBuckets"
      ],
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::*"
    },
    {
      "Sid": "Stmt1355727169913",
      "Action": [
        "s3:GetBucketLocation",
        "s3:ListBucket"
      ],
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::your_access_bucket_name"
    },
    {
      "Sid": "Stmt1355727169914",
      "Action": "s3:*",
      "Effect": "Allow",
      "Resource": "arn:aws:s3:::your_access_bucket_name/*"
    }
  ]
}