Granting access to an Amazon S3 bucket

When you create a file share, your File Gateway requires access to upload files into your Amazon S3 bucket, and to perform actions on any access points or virtual private cloud (VPC) endpoints that it uses to connect to the bucket. To grant this access, your File Gateway assumes an AWS Identity and Access Management (IAM) role that is associated with an IAM policy that grants this access.

The role requires this IAM policy and a security token service trust (STS) relationship for it. The policy determines which actions the role can perform. In addition, your S3 bucket and any associated access points or VPC endpoints must have an access policy that allows the IAM role to access them.

You can create the role and access policy yourself, or your File Gateway can create them for you. If your File Gateway creates the policy for you, the policy contains a list of S3 actions. For information about roles and permissions, see Creating a role to delegate permissions to an AWS service in the IAM User Guide.

The following example is a trust policy that allows your File Gateway to assume an IAM role.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "",
      "Effect": "Allow",
      "Principal": {
        "Service": "storagegateway.amazonaws.com"
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

If you don't want your File Gateway to create a policy on your behalf, you can create your own policy and attach it to your file share. For more information about how to do this, see Creating a file share.

The following example policy allows your File Gateway to perform all the Amazon S3 actions listed in the policy. The first part of the statement allows all the actions listed to be performed on the S3 bucket named amzn-s3-demo-bucket. The second part allows the listed actions on all objects in amzn-s3-demo-bucket.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "s3:GetAccelerateConfiguration",
                "s3:GetBucketLocation",
                "s3:GetBucketVersioning",
                "s3:ListBucket",
                "s3:ListBucketVersions",
                "s3:ListBucketMultipartUploads"
            ],
            "Resource": "arn:aws:s3:::amzn-s3-demo-bucket",
            "Effect": "Allow"
        },
        {
            "Action": [
                "s3:AbortMultipartUpload",
                "s3:DeleteObject",
                "s3:DeleteObjectVersion",
                "s3:GetObject",
                "s3:GetObjectAcl",
                "s3:GetObjectVersion",
                "s3:ListMultipartUploadParts",
                "s3:PutObject",
                "s3:PutObjectAcl"
            ],
            "Resource": "arn:aws:s3:::amzn-s3-demo-bucket/*",
            "Effect": "Allow"
        }
    ]
}

The following example policy is similar to the preceding one, but allows your File Gateway to perform actions required to access a bucket through an access point.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "s3:AbortMultipartUpload",
                "s3:DeleteObject",
                "s3:DeleteObjectVersion",
                "s3:GetObject",
                "s3:GetObjectAcl",
                "s3:GetObjectVersion",
                "s3:ListMultipartUploadParts",
                "s3:PutObject",
                "s3:PutObjectAcl"
            ],
            "Resource": "arn:aws:s3:us-east-1:123456789:accesspoint/TestAccessPointName/*",
            "Effect": "Allow"
        }
    ]
}