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Encryption of secure assets in Azure Automation

  • Artikkeli

Azure Automation secures assets such as credentials, certificates, connections, and encrypted variables are using various levels of encryption. This helps enhance the security of these assets. Additionally, to ensure greater security and privacy for the customer code, runbooks, and DSC scripts are also encrypted. Encryption in Azure Automation follows two models, depending on the top-level key used for encryption:

  • Using Microsoft-managed keys
  • Using keys that you manage

Microsoft-managed Keys

By default, your Azure Automation account uses Microsoft-managed keys.

Each secure asset is encrypted and stored in Azure Automation using a unique key (Data Encryption key) that is generated for each automation account. These keys themselves are encrypted and stored in Azure Automation using yet another unique key that is generated for each account called an Account Encryption Key (AEK). These account encryption keys encrypted and stored in Azure Automation using Microsoft-managed Keys.

Keys that you manage with Key Vault

You can manage encryption of secure assets for your Automation account with your own keys. When you specify a customer-managed key at the level of the Automation account, that key is used to protect and control access to the account encryption key for the Automation account. This in turn is used to encrypt and decrypt all the secure assets. Customer-managed keys offer greater flexibility to create, rotate, disable, and revoke access controls. You can also audit the encryption keys used to protect your secure assets.

Use Azure Key Vault to store customer-managed keys. You can either create your own keys and store them in a key vault, or you can use the Azure Key Vault APIs to generate keys.

Enabling the Azure Firewall on Azure Key Vault blocks access from Azure Automation runbooks for that service. Access will be blocked even when the firewall exception to allow trusted Microsoft services is enabled, as Automation is not a part of the trusted services list. With an enabled firewall, access can only be made by using a Hybrid Runbook Worker and a virtual network service endpoint. However, when you enable the Private link for Key Vault, Azure Automation loses access to the Key Vault. Even if you enable a Private link for Hybrid Runbook Worker, it will allow access only to Azure Automation service and not to the Key Vault.

For more information about Azure Key Vault, see What is Azure Key Vault?

Use of customer-managed keys for an Automation account

When you use encryption with customer-managed keys for an Automation account, Azure Automation wraps the account encryption key with the customer-managed key in the associated key vault. Enabling customer-managed keys doesn't impact performance, and the account is encrypted with the new key immediately, without any delay.

A new Automation account is always encrypted using Microsoft-managed keys. It's not possible to enable customer-managed keys at the time that the account is created. Customer-managed keys are stored in Azure Key Vault, and the key vault must be provisioned with access policies that grant key permissions to the managed identity that is associated with the Automation account. The managed identity is available only after the automation account is created.

When you modify the key being used for Azure Automation secure asset encryption, by enabling or disabling customer-managed keys, updating the key version, or specifying a different key, the encryption of the account encryption key changes but the secure assets in your Azure Automation account don't need to be re-encrypted.

Note

To enable customer-managed key using Azure Automation REST API calls, you need to use api version 2020-01-13-preview.

Prerequisites for using customer-managed keys in Azure Automation

Before enabling customer-managed keys for an Automation account, you must ensure the following prerequisites are met:

Generate and assign a new system-assigned identity for an Automation account

To use customer-managed keys with an Automation account, your Automation account needs to authenticate against the key vault storing customer-managed keys. Azure Automation uses system assigned managed identities to authenticate the account with Azure Key Vault. For more information about managed identities, see What are managed identities for Azure resources?

Using PowerShell

Use PowerShell cmdlet Set-AzAutomationAccount to modify an existing Azure Automation account. The -AssignSystemIdentity parameter generates and assigns a new system-assigned identity for the Automation account to use with other services like Azure Key Vault. For more information, see What are managed identities for Azure resources? and About Azure Key Vault. Execute the following code:

# Revise variables with your actual values.
$resourceGroup = "ResourceGroupName"
$automationAccount = "AutomationAccountName"
$vaultName = "KeyVaultName"
$keyName = "KeyName"

Set-AzAutomationAccount `
    -ResourceGroupName $resourceGroup `
    -Name $automationAccount `
    -AssignSystemIdentity

The output should look similar to the following:

Output from Set-AzAutomationAccount cmdlet.

Obtain the PrincipalId for later use. Execute the following code:

$principalID = (Get-AzAutomationAccount `
    -ResourceGroupName $resourceGroup `
    -Name $automationAccount).Identity.PrincipalId

$principalID

Using REST

Configure a system-assigned managed identity to the Automation account using the following REST API call:

PATCH https://management.azure.com/subscriptions/aaaa0a0a-bb1b-cc2c-dd3d-eeeeee4e4e4e/resourceGroups/resource-group-name/providers/Microsoft.Automation/automationAccounts/automation-account-name?api-version=2020-01-13-preview

Request body:

{ 
 "identity": 
 { 
  "type": "SystemAssigned" 
  } 
}

System-assigned identity for the Automation account is returned in a response similar to the following:

{
 "name": "automation-account-name",
 "id": "/subscriptions/aaaa0a0a-bb1b-cc2c-dd3d-eeeeee4e4e4e/resourceGroups/resource-group-name/providers/Microsoft.Automation/automationAccounts/automation-account-name",
 ..
 "identity": {
    "type": "SystemAssigned",
    "principalId": "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa",
    "tenantId": "bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb"
 },
..
}

Configuration of the Key Vault access policy

Once a system assigned managed identity is assigned to the Automation account, you configure access to the key vault storing customer-managed keys. Azure Automation requires the Get, Recover, WrapKey, and UnwrapKey operation permissions for the identity to access the customer-managed keys.

Using PowerShell

Use PowerShell cmdlet Set-AzKeyVaultAccessPolicy to grant the necessary permissions. Then use Add-AzKeyVaultKey to create a key in the key vault. Execute the following code:

Set-AzKeyVaultAccessPolicy `
    -VaultName $vaultName `
    -ObjectId $principalID `
    -PermissionsToKeys Get, Recover, UnwrapKey, WrapKey

Add-AzKeyVaultKey `
    -VaultName $vaultName `
    -Name $keyName `
    -Destination 'Software'

The output should look similar to the following:

Output from Add-AzKeyVaultKey cmdlet.

Using REST

The access policy can be set using the following REST API call:

PUT https://management.azure.com/subscriptions/aaaa0a0a-bb1b-cc2c-dd3d-eeeeee4e4e4e/resourceGroups/sample-group/providers/Microsoft.KeyVault/vaults/sample-vault/accessPolicies/add?api-version=2018-02-14

Request body:

{
  "properties": {
    "accessPolicies": [
      {
        "tenantId": "bbbbbbbb-bbbb-bbbb-bbbb-bbbbbbbbbbbb",
        "objectId": "aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa",
        "permissions": {
          "keys": [
            "get",
            "recover",
            "wrapKey",
            "unwrapKey"
          ],
          "secrets": [],
          "certificates": []
        }
      }
    ]
  }
}

Note

The tenantId and objectId fields must be provided with values of identity.tenantId and identity.principalId respectively from the response of managed identity for the Automation account.

Reconfigure Automation account to use customer-managed key

If you want to switch your Automation account from Microsoft-managed keys to customer-managed keys, you can perform this change using Azure PowerShell or with an Azure Resource Manager template.

Using PowerShell

Use PowerShell cmdlet Set-AzAutomationAccount to reconfigure the Automation account to use customer-managed keys.

$vaultURI = (Get-AzKeyVault -VaultName $vaultName).VaultUri
$keyVersion = (Get-AzKeyVaultKey -VaultName $vaultName -KeyName $keyName).Version

Set-AzAutomationAccount `
    -ResourceGroupName $resourceGroup `
    -Name $automationAccount `
    -AssignSystemIdentity `
    -KeyName $keyName `
    -KeyVaultUri $vaultURI `
    -KeyVersion $keyVersion `
    -KeyVaultEncryption

You can verify the change by running the following command:

(Get-AzAutomationAccount `
    -ResourceGroupName $resourceGroup `
    -Name $automationAccount).Encryption `
    |  ConvertTo-Json

The output should look similar to the following:

Output from Get-AzAutomationAccount cmdlet.

Using REST

Use the following REST API call:

PATCH https://management.azure.com/subscriptions/aaaa0a0a-bb1b-cc2c-dd3d-eeeeee4e4e4e/resourceGroups/resource-group-name/providers/Microsoft.Automation/automationAccounts/automation-account-name?api-version=2020-01-13-preview

Request body:

{
	"identity": {
	"type": "SystemAssigned"
	},
	"properties": {
		"encryption": {
			"keySource": "Microsoft.Keyvault",
			"keyvaultProperties": {
				"keyName": "sample-vault-key",
				"keyvaultUri": "https://sample-vault-key12.vault.azure.net",
				"keyVersion": "7c73556c521340209371eaf623cc099d"
			}
		}
	}
}

Sample response

{
  "name": "automation-account-name",
  "id": "/subscriptions/aaaa0a0a-bb1b-cc2c-dd3d-eeeeee4e4e4e/resourceGroups/resource-group-name/providers/Microsoft.Automation/automationAccounts/automation-account-name",
  ..
  "properties": {
    ..
    "encryption": {
      "keyvaultProperties": {
         "keyName": "sample-vault-key",
          "keyvaultUri": "https://sample-vault-key12.vault.azure.net",
          "keyVersion": "7c73556c521340209371eaf623cc099d"
      },
      "keySource": "Microsoft.Keyvault"
    },
    ..
  }
}

Rotation of a customer-managed key

You can rotate a customer-managed key in Azure Key Vault according to your compliance policies. When the key is rotated, you must update the Automation account to use the new key URI.

Rotating the key doesn't trigger re-encryption of secure assets in the Automation account. There's no further action required.

Revocation of access to a customer-managed key

To revoke access to customer-managed keys, use PowerShell or the Azure CLI. For more information, see Azure Key Vault PowerShell or Azure Key Vault CLI. Revoking access effectively blocks access to all secure assets in the Automation account, as the encryption key is inaccessible by Azure Automation.

Next steps