Encryption of data at rest for Amazon OpenSearch Service

OpenSearch Service domains offer encryption of data at rest, a security feature that helps prevent unauthorized access to your data. The feature uses AWS Key Management Service (AWS KMS) to store and manage your encryption keys and the Advanced Encryption Standard algorithm with 256-bit keys (AES-256) to perform the encryption. If enabled, the feature encrypts the following aspects of a domain:

The following are not encrypted when you enable encryption of data at rest, but you can take additional steps to protect them:

OpenSearch Service supports only symmetric encryption KMS keys, not asymmetric ones. To learn how to create symmetric keys, see Creating keys in the AWS Key Management Service Developer Guide.

Regardless of whether encryption at rest is enabled, all domains automatically encrypt custom packages using AES-256 and OpenSearch Service-managed keys.

Permissions

To use the OpenSearch Service console to configure encryption of data at rest, you must have read permissions to AWS KMS, such as the following identity-based policy:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "kms:List*",
        "kms:Describe*"
      ],
      "Resource": "*"
    }
  ]
}

If you want to use a key other than the AWS owned key, you must also have permissions to create grants for the key. These permissions typically take the form of a resource-based policy that you specify when you create the key.

If you want to keep your key exclusive to OpenSearch Service, you can add the kms:ViaService condition to that key policy:

"Condition": {
  "StringEquals": {
    "kms:ViaService": "es.us-west-1.amazonaws.com"
  },
  "Bool": {
    "kms:GrantIsForAWSResource": "true"
  }
}

For more information, see Using key policies in AWS KMS in the AWS Key Management Service Developer Guide.

Enabling encryption of data at rest

Encryption of data at rest on new domains requires either OpenSearch or Elasticsearch 5.1 or later. Enabling it on existing domains requires either OpenSearch or Elasticsearch 6.7 or later.

You can also enable encryption through the configuration API. The following request enables encryption of data at rest on an existing domain:

{
   "ClusterConfig":{
      "EncryptionAtRestOptions":{
         "Enabled": true,
         "KmsKeyId":"arn:aws:kms:us-east-1:123456789012:alias/my-key"
      }
   }
}

Disabled or deleted KMS key

If you disable or delete the key that you used to encrypt a domain, the domain becomes inaccessible. OpenSearch Service sends you a notification informing you that it can't access the KMS key. Re-enable the key immediately to access your domain.

The OpenSearch Service team can't help you recover your data if your key is deleted. AWS KMS deletes keys only after a waiting period of at least seven days. If your key is pending deletion, either cancel deletion or take a manual snapshot of the domain to prevent loss of data.

Disabling encryption of data at rest

After you configure a domain to encrypt data at rest, you can't disable the setting. Instead, you can take a manual snapshot of the existing domain, create another domain, migrate your data, and delete the old domain.

Monitoring domains that encrypt data at rest

Domains that encrypt data at rest have two additional metrics: KMSKeyError and KMSKeyInaccessible. These metrics appear only if the domain encounters a problem with your encryption key. For full descriptions of these metrics, see Cluster metrics. You can view them using either the OpenSearch Service console or the Amazon CloudWatch console.

Other considerations