Sharing a snapshot

Sharing a cluster snapshot using the console Security considerations for sharing encrypted snapshots

You can share an existing manual snapshot with other Amazon customer accounts by authorizing access to the snapshot. You can authorize up to 20 for each snapshot and 100 for each Amazon Key Management Service (Amazon KMS) key. That is, if you have 10 snapshots that are encrypted with a single KMS key, then you can authorize 10 Amazon accounts to restore each snapshot, or other combinations that add up to 100 accounts and do not exceed 20 accounts for each snapshot. A person logged in as a user in one of the authorized accounts can then describe the snapshot or restore it to create a new Amazon Redshift cluster under their account. For example, if you use separate Amazon customer accounts for production and test, a user can log on using the production account and share a snapshot with users in the test account. Someone logged on as a test account user can then restore the snapshot to create a new cluster that is owned by the test account for testing or diagnostic work.

A manual snapshot is permanently owned by the Amazon customer account under which it was created. Only users in the account owning the snapshot can authorize other accounts to access the snapshot, or to revoke authorizations. Users in the authorized accounts can only describe or restore any snapshot that has been shared with them; they cannot copy or delete snapshots that have been shared with them. An authorization remains in effect until the snapshot owner revokes it. If an authorization is revoked, the previously authorized user loses visibility of the snapshot and cannot launch any new actions referencing the snapshot. If the account is in the process of restoring the snapshot when access is revoked, the restore runs to completion. You cannot delete a snapshot while it has active authorizations; you must first revoke all of the authorizations.

Amazon customer accounts are always authorized to access snapshots owned by the account. Attempts to authorize or revoke access to the owner account will receive an error. You cannot restore or describe a snapshot that is owned by an inactive Amazon customer account.

After you have authorized access to an Amazon customer account, no users in that account can perform any actions on the snapshot unless they assume a role with policies that allow them to do so.

Users in the snapshot owner account can authorize and revoke access to a snapshot only if they assume a role with an IAM policy that allows them to perform those actions with a resource specification that includes the snapshot. For example, the following policy allows a user or role in Amazon account 012345678912 to authorize other accounts to access a snapshot named my-snapshot20130829:
```
{
  "Version": "2012-10-17",
  "Statement":[
    {
      "Effect":"Allow",
      "Action":[
          "redshift:AuthorizeSnapshotAccess",
          "redshift:RevokeSnapshotAccess"
          ],
      "Resource":[
           "arn:aws:redshift:us-east-1:012345678912:snapshot:*/my-snapshot20130829"
          ]
    }
  ]
}
```
Users in an Amazon account with which a snapshot has been shared cannot perform actions on that snapshot unless they have permissions allowing those actions. You can do this by assigning the policy to a role and assuming the role.
- To list or describe a snapshot, they must have an IAM policy that allows the DescribeClusterSnapshots action. The following code shows an example:
```
{
  "Version": "2012-10-17",
  "Statement":[
    {
      "Effect":"Allow",
      "Action":[
          "redshift:DescribeClusterSnapshots"
          ],
      "Resource":[
           "*"
          ]
    }
  ]
}
```
- To restore a snapshot, a user must assume a role with an IAM policy that allows the RestoreFromClusterSnapshot action and has a resource element that covers both the cluster they are attempting to create and the snapshot. For example, if a user in account 012345678912 has shared snapshot my-snapshot20130829 with account 219876543210, in order to create a cluster by restoring the snapshot, a user in account 219876543210 must assume a role with a policy such as the following:
```
{
  "Version": "2012-10-17",
  "Statement":[
    {
      "Effect":"Allow",
      "Action":[
          "redshift:RestoreFromClusterSnapshot"
          ],
      "Resource":[
           "arn:aws:redshift:us-east-1:012345678912:snapshot:*/my-snapshot20130829",
           "arn:aws:redshift:us-east-1:219876543210:cluster:from-another-account"
          ]
    }
  ]
}
```
- After access to a snapshot has been revoked from an Amazon account, no users in that account can access the snapshot. This is the case even if those accounts have IAM policies that allow actions on the previously shared snapshot resource.

On the console, you can authorize other users to access a manual snapshot you own, and you can later revoke that access when it is no longer required.

To share a snapshot with another account

Sign in to the Amazon Web Services Management Console and open the Amazon Redshift console at https://console.amazonaws.cn/redshiftv2/.
On the navigation menu, choose Clusters, Snapshots, then choose the manual snapshot to share.
For Actions, choose Manual snapshot settings to display the properties of the manual snapshot.
Enter the account or accounts to share with in the Manage access section, then choose Save.

When you provide access to an encrypted snapshot, Redshift requires that the Amazon KMS customer managed key used to create the snapshot is shared with the account or accounts performing the restore. If the key isn't shared, attempting to restore the snapshot results in an access-denied error. The receiving account doesn't need any extra permissions to restore a shared snapshot. When you authorize snapshot access and share the key, the identity authorizing access must have kms:DescribeKey permissions on the key used to encrypt the snapshot. This permission is described in more detail in Amazon KMS permissions. For more information, see DescribeKey in the Amazon Redshift API reference documentation.

The customer managed key policy can be updated programmatically or in the Amazon Key Management Service console.

To share the Amazon KMS customer managed key for an encrypted snapshot, update the key policy by performing the following steps:

Update the KMS key policy with the Amazon Resource Name (ARN) of the Amazon account that you are sharing to as Principal in the KMS key policy.
Allow the kms:Decrypt action.

In the following key-policy example, user 111122223333 is the owner of the KMS key, and user 444455556666 is the account that the key is shared with. This key policy gives the Amazon account access to the sample KMS key by including the ARN for the root Amazon account identity for user 444455556666 as a Principal for the policy, and by allowing the kms:Decrypt action.


{
    "Id": "key-policy-1",
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "Allow use of the key",
            "Effect": "Allow",
            "Principal": {
                "AWS": [
                    "arn:aws:iam::111122223333:user/KeyUser",
                    "arn:aws:iam::444455556666:root"
                ]
            },
            "Action": [
                "kms:Decrypt"
            ],
            "Resource": "*"
        }
    ]
}

After access is granted to the customer managed KMS key, the account that restores the encrypted snapshot must create an Amazon Identity and Access Management (IAM) role, or user, if it doesn't already have one. In addition, that Amazon account must also attach an IAM policy to that IAM role or user that allows them to restore an encrypted database snapshot, using your KMS key.

For more information about giving access to an Amazon KMS key, see Allowing users in other accounts to use a KMS key, in the Amazon Key Management Service developer guide.

For an overview of key policies, see How Amazon Redshift uses Amazon KMS.

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Creating a snapshot schedule

Copying an automated snapshot

Sharing a cluster snapshot using the console

To share a snapshot with another account

Security considerations for sharing encrypted snapshots

Allowing access to the Amazon KMS key for an encrypted snapshot