Cis Azure Storage 17.5

17.5 Ensure that 'Enable Infrastructure Encryption' for Each Storage Account in Azure Storage is Set to 'enabled' (Automated)

Description

Enabling encryption at the hardware level on top of the default software encryption for Storage Accounts accessing Azure storage solutions.

Rationale

Azure Storage automatically encrypts all data in a storage account at the network level using 256-bit AES encryption, which is one of the strongest, FIPS 140-2-compliant block ciphers available. Customers who require higher levels of assurance that their data is secure can also enable 256-bit AES encryption at the Azure Storage infrastructure level for double encryption. Double encryption of Azure Storage data protects against a scenario where one of the encryption algorithms or keys may be compromised. Similarly, data is encrypted even before network transmission and in all backups. In this scenario, the additional layer of encryption continues to protect your data. For the most secure implementation of key based encryption, it is recommended to use a Customer Managed asymmetric RSA 2048 Key in Azure Key Vault.

Impact

The read and write speeds to the storage will be impacted if both default encryption and Infrastructure Encryption are checked, as a secondary form of encryption requires more resource overhead for the cryptography of information. This performance impact should be considered in an analysis for justifying use of the feature in your environment. Customer-managed keys are recommended for the most secure implementation, leading to overhead of key management. The key will also need to be backed up in a secure location, as loss of the key will mean loss of the information in the storage.

Audit Procedure

Audit from Azure Portal

1. From Azure Portal select the portal menu in the top left.
2. Select Storage Accounts.
3. Click on each storage account within each resource group you wish to audit.
4. In the overview, under Security, ensure Infrastructure encryption is set to Enabled.

Audit from Azure CLI

az storage blob show \
    --account-name <storage-account> \
    --container-name <container> \
    --name <blob> \
    --query "properties.serverEncrypted"

Audit from PowerShell

$account = Get-AzStorageAccount -ResourceGroupName <resource-group> `
    -Name <storage-account>
$blob = Get-AzStorageBlob -Context $account.Context `
    -Container <container> `
    -Blob <blob>
$blob.ICloudBlob.Properties.IsServerEncrypted

Audit from Azure Policy

Policy ID: 4733ea7b-a883-42fe-8cac-97454c2a9e4a - Name: 'Storage accounts should have infrastructure encryption'

Expected Result

Infrastructure encryption should be set to Enabled for each storage account. CLI/PowerShell commands should return true for server encryption properties.

Remediation

Remediate from Azure Portal

1. During Storage Account creation, in the Encryption tab, check the box next to Enable infrastructure encryption.

Remediate from Azure CLI

Replace the information within <> with appropriate values:

az storage account create \
    --name <storage-account> \
    --resource-group <resource-group> \
    --location <location> \
    --sku Standard_RAGRS \
    --kind StorageV2 \
    --require-infrastructure-encryption

Remediate from PowerShell

Replace the information within <> with appropriate values:

New-AzStorageAccount -ResourceGroupName <resource_group> `
    -AccountName <storage-account> `
    -Location <location> `
    -SkuName "Standard_RAGRS" `
    -Kind StorageV2 `
    -RequireInfrastructureEncryption

Enabling Infrastructure Encryption after Storage Account Creation

If infrastructure encryption was not enabled on blob storage creation, there is no official way to enable it. Please see the additional information section.

Default Value

By default, Infrastructure Encryption is disabled in blob creation.

References

1. https://docs.microsoft.com/en-us/azure/storage/blobs/storage-blob-encryption-status
2. https://docs.microsoft.com/en-us/azure/storage/common/storage-service-encryption
3. https://docs.microsoft.com/en-us/azure/storage/common/infrastructure-encryption-enable
4. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-data-protection#dp-4-enable-data-at-rest-encryption-by-default

Additional Information

The default service side encryption for Azure Storage is enabled on every block blob, append blob, or page blob that was written to Azure Storage after October 20, 2017. Hardware encryption, however, cannot be enabled on a blob storage after its creation. There are ways to copy all data from a blob storage into another or download and reupload into another blob storage. This could result in data loss and is not recommended.

Profile

Level 2 | Automated