Tutorial: Create an application gateway with a web application firewall using the Azure portal

This tutorial shows you how to use the Azure portal to create an application gateway with a web application firewall (WAF). The WAF uses OWASP rules to protect your application. These rules include protection against attacks such as SQL injection, cross-site scripting attacks, and session hijacks. After creating the application gateway, you test it to make sure it's working correctly. With Azure Application Gateway, you direct your application web traffic to specific resources by assigning listeners to ports, creating rules, and adding resources to a backend pool. For the sake of simplicity, this tutorial uses a simple setup with a public front-end IP, a basic listener to host a single site on this application gateway, two virtual machines used for the backend pool, and a basic request routing rule.

In this tutorial, you learn how to:

  • Create an application gateway with WAF enabled
  • Create the virtual machines used as backend servers
  • Create a storage account and configure diagnostics
  • Test the application gateway

Web application firewall example

Note

This article has been updated to use the new Azure PowerShell Az module. To learn more about the new Az module and AzureRM compatibility, see Introducing the new Azure PowerShell Az module. For installation instructions, see Install Azure PowerShell.

If you prefer, you can complete this tutorial using Azure PowerShell or Azure CLI.

If you don't have an Azure subscription, create a free account before you begin.

Sign in to Azure

Sign in to the Azure portal at https://portal.azure.com

Create an application gateway

For Azure to communicate between resources, it needs a virtual network. You can either create a new virtual network or use an existing one. In this example, you create a new virtual network. You can create a virtual network at the same time that you create the application gateway. Application Gateway instances are created in separate subnets. You create two subnets in this example: one for the application gateway, and another for the backend servers.

Select Create a resource on the left menu of the Azure portal. The New window appears.

Select Networking and then select Application Gateway in the Featured list.

Basics page

  1. On the Basics page, enter these values for the following application gateway settings:
    • Name: Enter myAppGateway for the name of the application gateway.
    • Resource group: Select myResourceGroupAG for the resource group. If it doesn't exist, select Create new to create it.
    • Select WAF for the tier of the application gateway.Create new application gateway

Accept the default values for the other settings and then click OK.

Settings page

  1. On the Settings page, under Subnet configuration, select Choose a virtual network.
  2. On the Choose virtual network page, select Create new, and then enter values for the following virtual network settings:
    • Name: Enter myVNet for the name of the virtual network.
    • Address space: Enter 10.0.0.0/16 for the virtual network address space.
    • Subnet name: Enter myAGSubnet for the subnet name.
      The application gateway subnet can contain only application gateways. No other resources are allowed.
    • Subnet address range: Enter 10.0.0.0/24 for the subnet address range.Create virtual network
  3. Click OK to create the virtual network and subnet.
  4. Choose the Frontend IP configuration. Under Frontend IP configuration, verify IP address type is set to Public. Under Public IP address, verify Create new is selected.
    You can configure the Frontend IP to be Public or Private as per your use case. Here, you choose a Public Frontend IP.
  5. Enter myAGPublicIPAddress for the public IP address name.
  6. Accept the default values for the other settings and then select OK.
    You choose default values in this tutorial for simplicity but you can configure custom values for the other settings depending on your use case.

Summary page

Review the settings on the Summary page, and then select OK to create the virtual network, the public IP address, and the application gateway. It may take several minutes for Azure to create the application gateway. Wait until the deployment finishes successfully before moving on to the next section.

Add backend pool

The backend pool is used to route requests to the backend servers, which serve the request. Backend pools can have NICs, virtual machine scale sets, public IPs, internal IPs, fully qualified domain names (FQDN), and multi-tenant back-ends like Azure App Service. Add your backend targets to a backend pool.

In this example, you use virtual machines as the target backend. You can either use existing virtual machines or create new ones. Here, you create two virtual machines that Azure uses as backend servers for the application gateway. To do this, you:

  1. Create a new subnet, myBackendSubnet, in which the new VMs will be created.
  2. Create two new VMS, myVM and myVM2, to be used as backend servers.
  3. Install IIS on the virtual machines to verify that the application gateway was created successfully.
  4. Add the backend servers to the backend pool.

Add a subnet

Add a subnet to the virtual network you created by following these steps:

  1. Select All resources on the left menu of the Azure portal, enter myVNet in the search box, and then select myVNet from the search results.

  2. Select Subnets from the left menu and then select + Subnet.

    Create subnet

  3. From the Add subnet page, enter myBackendSubnet for the Name of the subnet, and then select OK.

Create a virtual machine

  1. On the Azure portal, select Create a resource. The New window appears.
  2. Select Compute and then select Windows Server 2016 Datacenter in the Featured list. The Create a virtual machine page appears.
    Application Gateway can route traffic to any type of virtual machine used in its backend pool. In this example, you use a Windows Server 2016 Datacenter.
  3. Enter these values in the Basics tab for the following virtual machine settings:
    • Resource group: Select myResourceGroupAG for the resource group name.
    • Virtual machine name: Enter myVM for the name of the virtual machine.
    • Username: Enter azureuser for the administrator user name.
    • Password: Enter Azure123456! for the administrator password.
  4. Accept the other defaults and then select Next: Disks.
  5. Accept the Disks tab defaults and then select Next: Networking.
  6. On the Networking tab, verify that myVNet is selected for the Virtual network and the Subnet is set to myBackendSubnet. Accept the other defaults and then select Next: Management.
    Application Gateway can communicate with instances outside of the virtual network that it is in, but you need to ensure there's IP connectivity.
  7. On the Management tab, set Boot diagnostics to Off. Accept the other defaults and then select Review + create.
  8. On the Review + create tab, review the settings, correct any validation errors, and then select Create.
  9. Wait for the virtual machine creation to complete before continuing.

Install IIS for testing

In this example, you install IIS on the virtual machines only for the purpose of verifying Azure created the application gateway successfully.

  1. Open Azure PowerShell. To do so, select Cloud Shell from the top navigation bar of the Azure portal and then select PowerShell from the drop-down list.

    Install custom extension

  2. Run the following command to install IIS on the virtual machine:

    Set-AzVMExtension `
      -ResourceGroupName myResourceGroupAG `
      -ExtensionName IIS `
      -VMName myVM `
      -Publisher Microsoft.Compute `
      -ExtensionType CustomScriptExtension `
      -TypeHandlerVersion 1.4 `
      -SettingString '{"commandToExecute":"powershell Add-WindowsFeature Web-Server; powershell Add-Content -Path \"C:\\inetpub\\wwwroot\\Default.htm\" -Value $($env:computername)"}' `
      -Location EastUS
    
  3. Create a second virtual machine and install IIS by using the steps that you previously completed. Use myVM2 for the virtual machine name and for the VMName setting of the Set-AzVMExtension cmdlet.

Add backend servers to backend pool

  1. Select All resources, and then select myAppGateway.

  2. Select Backend pools from the left menu. Azure automatically created a default pool, appGatewayBackendPool, when you created the application gateway.

  3. Select appGatewayBackendPool.

  4. Under Targets, select Virtual machine from the drop-down list.

  5. Under VIRTUAL MACHINE and NETWORK INTERFACES, select the myVM and myVM2 virtual machines and their associated network interfaces from the drop-down lists.

    Add backend servers

  6. Select Save.

Create a storage account and configure diagnostics

Create a storage account

In this tutorial, the application gateway uses a storage account to store data for detection and prevention purposes. You could also use Azure Monitor logs or Event Hub to record data.

  1. Click New found on the upper left-hand corner of the Azure portal.
  2. Select Storage, and then select Storage account - blob, file, table, queue.
  3. Enter the name of the storage account, select Use existing for the resource group, and then select myResourceGroupAG. In this example, the storage account name is myagstore1. Accept the default values for the other settings and then click Create.

Configure diagnostics

Configure diagnostics to record data into the ApplicationGatewayAccessLog, ApplicationGatewayPerformanceLog, and ApplicationGatewayFirewallLog logs.

  1. In the left-hand menu, click All resources, and then select myAppGateway.

  2. Under Monitoring, click Diagnostics logs.

  3. Click Add diagnostics setting.

  4. Enter myDiagnosticsSettings as the name for the diagnostics settings.

  5. Select Archive to a storage account, and then click Configure to select the myagstore1 storage account that you previously created.

  6. Select the application gateway logs to collect and retain.

  7. Click Save.

    Configure diagnostics

Test the application gateway

Although IIS isn't required to create the application gateway, you installed it in this quickstart to verify whether Azure successfully created the application gateway. Use IIS to test the application gateway:

  1. Find the public IP address for the application gateway on its Overview page.Record application gateway public IP addressAlternatively, you can select All resources, enter myAGPublicIPAddress in the search box, and then select it in the search results. Azure displays the public IP address on the Overview page.
  2. Copy the public IP address, and then paste it into the address bar of your browser.
  3. Check the response. A valid response verifies that the application gateway was successfully created and it can successfully connect with the backend.Test application gateway

Clean up resources

When you no longer need the resources that you created with the application gateway, remove the resource group. By removing the resource group, you also remove the application gateway and all its related resources.

To remove the resource group:

  1. On the left menu of the Azure portal, select Resource groups.
  2. On the Resource groups page, search for myResourceGroupAG in the list, then select it.
  3. On the Resource group page, select Delete resource group.
  4. Enter myResourceGroupAG for TYPE THE RESOURCE GROUP NAME and then select Delete

Next steps