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3.12 Ensure Storage for Critical Data are Encrypted with Customer Managed Keys (Manual)​

Profile Applicability​

• Level 2

Description​

Enable sensitive data encryption at rest using Customer Managed Keys rather than Microsoft Managed keys.

Rationale​

By default, data in the storage account is encrypted using Microsoft Managed Keys at rest. All Azure Storage resources are encrypted, including blobs, disks, files, queues, and tables. All object metadata is also encrypted. If you want to control and manage this encryption key yourself, however, you can specify a customer-managed key. That key is used to protect and control access to the key that encrypts your data. You can also choose to automatically update the key version used for Azure Storage encryption whenever a new version is available in the associated Key Vault.

Impact​

If the key expires by setting the 'activation date' and 'expiration date', the user must rotate the key manually.

Using Customer Managed Keys may also incur additional man-hour requirements to create, store, manage, and protect the keys as needed.

Audit​

From Azure Console​

  1. Go to Storage Accounts
  2. For each storage account, go to Encryption
  3. Ensure that Encryption type is set to Customer Managed Keys

From Azure PowerShell​

Connect-AzAccount
Set-AzContext -Subscription <subscription id>
Get-AzStorageAccount |Select-Object -ExpandProperty Encryption

PowerShell Results - Non-Compliant

...
KeySource : Microsoft.Storage
...

PowerShell Results - Compliant

...
KeySource : Microsoft.Keyvault
...

Remediation​

From Azure Portal​

  1. Go to Storage Accounts
  2. For each storage account, go to Encryption
  3. Set Customer Managed Keys
  4. Select the Encryption key and enter the appropriate setting value
  5. Click Save

References​

https://docs.microsoft.com/en-us/azure/storage/common/storage-service-encryption
https://docs.microsoft.com/en-us/azure/security/fundamentals/data-encryption-best-practices#protect-data-at-rest
https://docs.microsoft.com/en-us/azure/storage/common/storage-service-encryption#azure-storage-encryption-versus-disk-encryption
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-data-protection#dp-5-use-customer-managed-key-option-in-data-at-rest-encryption-when-required