Encryption for backups in AWS Backup

Independent encryption

AWS Backup offers independent encryption for resource types that support full AWS Backup management. Independent encryption means that recovery points (backups) you create through AWS Backup can have an encryption method other than one determined by the source resource's encryption. For example, your backup of an Amazon S3 bucket can have a different encryption method than the source bucket you encrypted with Amazon S3 encryption. This encryption is controlled through the AWS KMS key configuration in the backup vault where your backup in stored.

Backups of resource types that are not fully managed by AWS Backup typically inherit the encryption settings from their source resource. You can configure these encryption settings according to that service's instructions, such as Amazon EBS encryption in the Amazon EBS User Guide.

Your IAM role must have access to the KMS key being used to back up and restore the object. Otherwise the job is successful but the objects are not backed up or restored. The permissions in IAM policy and KMS key policy must be consistent. For more information, see Specifying KMS keys in IAM policy statements in the AWS Key Management Service Developer Guide.

The following table lists each supported resource type, how encryption is configured for backups, and whether independent encryption for backups is supported. When AWS Backup independently encrypts a backup, it uses the industry-standard AES-256 encryption algorithm. For more information about encryption in AWS Backup, see cross-Region and cross-account backup.

Encryption for copies of a backup to a different account or AWS Region

When you copy your backups across accounts or Regions, AWS Backup automatically encrypts those copies for most resource types, even if the original backup is unencrypted.

Before you copy a backup from one account to another (cross-account copy job) or copy a backup from one Region to another (cross-Region copy job), note the following conditions, many of which depend on whether the resource type in the backup (recovery point) is fully managed by AWS Backup or not fully managed.

AWS Backup permissions, grants, and deny statements

To help avoid failed jobs, you can examine the AWS KMS key policy to ensure it has required permissions and does not have any deny statements that prevent successful operations.

Failed jobs can occur due to either one or more Deny statements applied to the KMS key or due to a grant revoked for the key.

In an AWS managed access policy such as AWSBackupFullAccess, there are Allow actions that permit AWS Backup to interface with AWS KMS to create a grant on a KMS key on a customer's behalf as part backup, copy, and storage operations.

At a minimum, the key policy requires the following permissions:

If Deny policies are necessary, you will need to allowlist the required roles for backup and restore operations.

These elements can look like:

{
    "Sid": "KmsPermissions",
    "Effect": "Allow",
    "Action": [
        "kms:ListKeys",
        "kms:DescribeKey",
        "kms:GenerateDataKey",
        "kms:ListAliases"
    ],
    "Resource": "*"
},
{
    "Sid": "KmsCreateGrantPermissions",
    "Effect": "Allow",
    "Action": [
        "kms:CreateGrant"
    ],
    "Resource": "*",
    "Condition": {
        "ForAnyValue:StringEquals": {
            "kms:EncryptionContextKeys": "aws:backup:backup-vault"
        },
        "Bool": {
            "kms:GrantIsForAWSResource": true
        },
        "StringLike": {
            "kms:ViaService": "backup.*.amazonaws.com"
        }
    }
}

These permissions must be part of the key, whether it is AWS managed or customer managed.

Additionally, the key associated with the role initiating a cross-Region copy job must have "kms:ResourcesAliases": "alias/aws/backup" in the DescribeKey permission.