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9.11 Ensure Azure Key Vaults are Used to Store Secrets (Manual)​

Profile Applicability​

• Level 2

Description​

Azure Key Vault will store multiple types of sensitive information such as encryption keys, certificate thumbprints, and Managed Identity Credentials. Access to these 'Secrets' can be controlled through granular permissions.

Rationale​

The credentials given to an application have permissions to create, delete, or modify data stored within the systems they access. If these credentials are stored within the application itself, anyone with access to the application or a copy of the code has access to them. Storing within Azure Key Vault as secrets increases security by controlling access. This also allows for updates of the credentials without redeploying the entire application.

Impact​

Integrating references to secrets within the key vault are required to be specifically integrated within the application code. This will require additional configuration to be made during the writing of an application, or refactoring of an already written one. There are also additional costs that are charged per 10000 requests to the Key Vault.

Audit​

From Azure Portal​

  1. Login to Azure Portal
  2. In the expandable menu on the left go to Key Vaults
  3. View the Key Vaults listed.

From Azure CLI​

To list key vaults within a subscription run the following command:

Get-AzKeyVault

To list the secrets within these key vaults run the following command:

Get-AzKeyVaultSecret [-VaultName] <vault name>

From Azure Powershell​

To list key vaults within a subscription run the following command:

Get-AzKeyVault

To list all secrets in a key vault run the following command:

Get-AzKeyVaultSecret -VaultName '<vaultName'

Remediation​

Remediation has 2 steps

  1. Setup the Key Vault
  2. Setup the App Service to use the Key Vault

Step 1: Set up the Key Vault

From Azure CLI​

az keyvault create --name "<name>" --resource-group "<myResourceGroup>" --location myLocation

From Azure Powershell​

New-AzKeyvault -name <name> -ResourceGroupName <myResourceGroup> -Location <myLocation>

Step 2: Set up the App Service to use the Key Vault

Sample JSON Template for App Service Configuration:

{
 //...
 "resources": [
 {
 "type": "Microsoft.Storage/storageAccounts",
 "name": "[variables('storageAccountName')]",
 //...
 },
 {
 "type": "Microsoft.Insights/components",
 "name": "[variables('appInsightsName')]",
 //...
 },
 {
 "type": "Microsoft.Web/sites",
 "name": "[variables('functionAppName')]",
 "identity": {
 "type": "SystemAssigned"
 },
 //...
 "resources": [
 {
 "type": "config",
 "name": "appsettings",
 //...
 "dependsOn": [
 "[resourceId('Microsoft.Web/sites', variables('functionAppName'))]",
 "[resourceId('Microsoft.KeyVault/vaults/', variables('keyVaultName'))]",
 "[resourceId('Microsoft.KeyVault/vaults/secrets', variables('keyVaultName'), variables('storageConnectionStringName'))]",
 "[resourceId('Microsoft.KeyVault/vaults/secrets', variables('keyVaultName'), variables('appInsightsKeyName'))]"
 ],
 "properties": {
 "AzureWebJobsStorage": "[concat('@Microsoft.KeyVault(SecretUri=', reference(variables('storageConnectionStringResourceId')).secretUriWithVersion, ')')]",
 "WEBSITE_CONTENTAZUREFILECONNECTIONSTRING": "[concat('@Microsoft.KeyVault(SecretUri=', reference(variables('storageConnectionStringResourceId')).secretUriWithVersion, ')')]",
 "APPINSIGHTS_INSTRUMENTATIONKEY": "[concat('@Microsoft.KeyVault(SecretUri=', reference(variables('appInsightsKeyResourceId')).secretUriWithVersion, ')')]",
 "WEBSITE_ENABLE_SYNC_UPDATE_SITE": "true"
 //...
 }
 },
 {
 "type": "sourcecontrols",
 "name": "web",
 //...
 "dependsOn": [
 "[resourceId('Microsoft.Web/sites', variables('functionAppName'))]",
 "[resourceId('Microsoft.Web/sites/config', variables('functionAppName'), 'appsettings')]"
 ],
 }
 ]
 },
 {
 "type": "Microsoft.KeyVault/vaults",
 "name": "[variables('keyVaultName')]",
 //...
 "dependsOn": [
 "[resourceId('Microsoft.Web/sites', variables('functionAppName'))]"
 ],
 "properties": {
 //...
 "accessPolicies": [
 {
 "tenantId": "[reference(concat('Microsoft.Web/sites/', variables('functionAppName'), '/providers/Microsoft.ManagedIdentity/Identities/default'), '2015-08-31-PREVIEW').tenantId]",
 "objectId": "[reference(concat('Microsoft.Web/sites/', variables('functionAppName'), '/providers/Microsoft.ManagedIdentity/Identities/default'), '2015-08-31-PREVIEW').principalId]",
 "permissions": {
 "secrets": [ "get" ]
 }
 }
 ]
 },
 "resources": [
 {
 "type": "secrets",
 "name": "[variables('storageConnectionStringName')]",
 //...
 "dependsOn": [
 "[resourceId('Microsoft.KeyVault/vaults/', variables('keyVaultName'))]",
 "[resourceId('Microsoft.Storage/storageAccounts', variables('storageAccountName'))]"
 ],
 "properties": {
 "value": "[concat('DefaultEndpointsProtocol=https;AccountName=', variables('storageAccountName'), ';AccountKey=', listKeys(variables('storageAccountResourceId'),'2015-05-01-preview').key1)]"
 }
 },
 {
 "type": "secrets",
 "name": "[variables('appInsightsKeyName')]",
 //...
 "dependsOn": [
 "[resourceId('Microsoft.KeyVault/vaults/', variables('keyVaultName'))]",
 "[resourceId('Microsoft.Insights/components', variables('appInsightsName'))]"
 ],
 "properties": {
 "value": "[reference(resourceId('microsoft.insights/components/', variables('appInsightsName')), '2015-05-01').InstrumentationKey]"
 }
 }
 ]
 }
 ]
}

References​

https://docs.microsoft.com/en-us/azure/app-service/app-service-key-vault-references
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-identity-management#im-2-manage-application-identities-securely-and-automatically
https://docs.microsoft.com/en-us/cli/azure/keyvault?view=azure-cli-latest
https://docs.microsoft.com/en-us/cli/azure/keyvault?view=azure-cli-latest