Cis Azure Compute 2.1.18

Ensure app is integrated with a virtual network

Description

Integrate App Service apps with a virtual network to enable access to resources in or through a non-internet-routable virtual network.

Rationale

Integrate App Service apps with a virtual network for increased security and control.

Impact

Additional configuration may be required to ensure that traffic is routed properly.

Audit Procedure

Using Azure Portal

1. Go to App Services.
2. Click the name of an app.
3. Under Settings, click Networking.
4. Under Outbound traffic configuration, next to Virtual network integration, ensure that a virtual network and subnet name are displayed.
5. Repeat steps 1-4 for each app.

Using Azure CLI

Run the following command to list apps:

az webapp list

For each app, run the following command to get the virtual network subnet ID:

az webapp show --resource-group <resource-group-name> --name <app-name> --query "virtualNetworkSubnetId"

Ensure that a virtual network subnet ID is returned.

Using Azure PowerShell

Run the following command to list apps:

Get-AzWebApp

Run the following command to get the app in a resource group with a given name:

$app = Get-AzWebapp -ResourceGroupName <resource-group-name> -Name <app-name>

Run the following command to get the virtual network subnet ID:

$app.virtualNetworkSubnetId

Ensure that a virtual network subnet ID is returned. Repeat for each app.

Expected Result

A virtual network subnet ID should be returned, indicating the app is integrated with a virtual network.

Remediation

Using Azure Portal

1. Go to App Services.
2. Click the name of an app.
3. Under Settings, click Networking.
4. Under Outbound traffic configuration, next to Virtual network integration, click Not configured.
5. Click Add virtual network integration.
6. Select an existing App Service Plan connection, or select New connection and select a subscription, virtual network, and subnet.
7. Click Connect.
8. Repeat steps 1-7 for each app requiring remediation.

Using Azure CLI

For each app requiring remediation, run the following command to integrate with a virtual network:

az webapp vnet-integration add --resource-group <resource-group-name> --name <app-name> --vnet <virtual-network-name> --subnet <subnet-name>

Using Azure PowerShell

For each app requiring remediation, run the following commands to integrate with a virtual network:

Prepare parameters:

$siteName = '<app-name>'
$vNetResourceGroupName = '<virtual-network-resource-group-name>'
$appResourceGroupName = '<app-resource-group-name>'
$vNetName = '<virtual-network-name>'
$integrationSubnetName = '<subnet-name>'
$vNetSubscriptionId = '<subscription-guid>'

Check if the subnet is delegated to Microsoft.Web/serverFarms:

$vnet = Get-AzVirtualNetwork -Name $vNetName -ResourceGroupName $vNetResourceGroupName
$subnet = Get-AzVirtualNetworkSubnetConfig -Name $integrationSubnetName -VirtualNetwork $vnet
Get-AzDelegation -Subnet $subnet

Add delegation:

$subnet = Add-AzDelegation -Name "myDelegation" -ServiceName "Microsoft.Web/serverFarms" -Subnet $subnet
Set-AzVirtualNetwork -VirtualNetwork $vnet

Configure virtual network integration:

$subnetResourceId = "/subscriptions/$vNetSubscriptionId/resourceGroups/$vNetResourceGroupName/providers/Microsoft.Network/virtualNetworks/$vNetName/subnets/$integrationSubnetName"
$app = Get-AzResource -ResourceType Microsoft.Web/sites -ResourceGroupName $appResourceGroupName -ResourceName $siteName
$app.Properties.virtualNetworkSubnetId = $subnetResourceId
$app.Properties.vnetRouteAllEnabled = 'true'
$app | Set-AzResource -Force

Default Value

By default, virtual network integration is not configured.

References

1. https://learn.microsoft.com/en-us/azure/app-service/overview-vnet-integration
2. https://learn.microsoft.com/en-us/azure/app-service/configure-vnet-integration-enable
3. https://learn.microsoft.com/en-us/cli/azure/webapp
4. https://learn.microsoft.com/en-us/powershell/module/az.websites/get-azwebapp

Profile

Level 1 | Automated