Create an application gateway with a web application firewall by using the portal

Learn how to create a web application firewall (WAF)-enabled application gateway.

The WAF in Azure Application Gateway protects web applications from common web-based attacks like SQL injection, cross-site scripting attacks, and session hijacks. A WAF protects against many of the OWASP top 10 common web vulnerabilities.

Scenarios

This article presents two scenarios. In the first scenario, you learn how to create an application gateway with a WAF. In the second scenario, you learn how to add a WAF to an existing application gateway.

Scenario example

Note

You can add custom health probes, back-end pool addresses, and additional rules to the application gateway. These applications are configured after the application gateway is configured and not during initial deployment.

Before you begin

An application gateway requires its own subnet. When you create a virtual network, ensure that you leave enough address space to have multiple subnets. After you deploy an application gateway to a subnet, only additional application gateways can be added to the subnet.

Add a web application firewall to an existing application gateway

This example updates an existing application gateway to support a WAF in Prevention mode.

  1. In the Azure portal Favorites pane, select All resources. On the All resources blade, select the existing application gateway. If the subscription you selected already has several resources in it, enter the name in the Filter by name box to easily access the DNS zone.

    Existing application gateway selection

  2. Select Web application firewall, and update the application gateway settings. When the update finishes, select Save.

  3. Use the following settings to update an existing application gateway to support a WAF:

    Setting Value Details
    Upgrade to WAF tier Checked This option sets the tier of the application gateway to the WAF tier.
    Firewall status Enabled This setting enables the firewall on the WAF.
    Firewall mode Prevention This setting is how a WAF deals with malicious traffic. Detection mode only logs the events. Prevention mode logs the events and stops the malicious traffic.
    Rule set 3.0 This setting determines the core rule set that's used to protect the back-end pool members.
    Configure disabled rules Varies To prevent possible false positives, you can use this setting to disable certain rules and rule groups.
    Note

    When you upgrade an existing application gateway to the WAF SKU, the SKU size changes to medium. After configuration finishes, you can reconfigure this setting.

    Basic settings

    Note

    To view WAF logs, enable diagnostics and select ApplicationGatewayFirewallLog. Choose an instance count of 1 for testing purposes only. We do not recommend an instance count under 2 because it's not covered by the SLA. Small gateways aren't available when you use a WAF.

Create an application gateway with a web application firewall

This scenario will:

  • Create a medium WAF application gateway with two instances.
  • Create a virtual network named AdatumAppGatewayVNET with a reserved CIDR block of 10.0.0.0/16.
  • Create a subnet called Appgatewaysubnet that uses 10.0.0.0/28 as its CIDR block.
  • Configure a certificate for SSL offload.
  1. Sign in to the Azure portal. If you don't already have an account, you can sign up for a free one-month trial.

  2. In the Favorites pane on the portal, select New.

  3. On the New blade, select Networking. On the Networking blade, select Application Gateway, as shown in the following image:

    Application gateway creation

  4. On the Basics blade that appears, enter the following values, and then select OK:

    Setting Value Details
    Name AdatumAppGateway The name of the application gateway.
    Tier WAF Available values are Standard and WAF. To learn more about a WAF, see Web application firewall.
    SKU Size Medium Standard tier options are Small, Medium, and Large. WAF tier options are Medium and Large only.
    Instance count 2 The number of instances of the application gateway for high availability. Use instance counts of 1 for testing purposes only.
    Subscription [Your subscription] Select a subscription to use to create the application gateway.
    Resource group Create new: AdatumAppGatewayRG Create a resource group. The resource group name must be unique within the subscription you selected. To learn more about resource groups, read the Resource Manager overview article.
    Location West US

    Basic settings configuration

  5. On the Settings blade that appears under Virtual network, select Choose a virtual network. On the Choose virtual network blade, select Create new.

    Virtual network choice

  6. On the Create virtual network blade, enter the following values, and then select OK. The Subnet field on the Settings blade is populated with the subnet you chose.

    Setting Value Details
    Name AdatumAppGatewayVNET The name of the application gateway.
    Address space 10.0.0.0/16 This value is the address space for the virtual network.
    Subnet name AppGatewaySubnet The name of the subnet for the application gateway.
    Subnet address range 10.0.0.0/28 This subnet allows more additional subnets in the virtual network for back-end pool members.
  7. On the Settings blade under Frontend IP configuration, select Public as the IP address type.

  8. On the Settings blade under Public IP address, select Choose a public IP address. On the Choose public IP address blade, select Create new.

    Public IP address choice

  9. On the Create public IP address blade, accept the default value, and select OK. The Public IP address field is populated with the public IP address you chose.

  10. On the Settings blade under Listener configuration, select HTTP under Protocol. A certificate is required to use HTTPS. The private key for the certificate is needed. Provide a .pfx export of the certificate, and enter the password for the file.

  11. Configure specific settings for the WAF.

    Setting Value Details
    Firewall status Enabled This setting turns the WAF on or off.
    Firewall mode Prevention This setting determines the actions the WAF takes on malicious traffic. Detection mode only logs traffic. Prevention mode logs and stops traffic with a 403 Unauthorized response.
  12. Review the Summary page, and select OK. Now the application gateway is queued up and created.

  13. After the application gateway is created, go to it in the portal to continue configuration of the application gateway.

    Application gateway resource view

These steps create a basic application gateway with default settings for the listener, back-end pool, back-end HTTP settings, and rules. After the provisioning finishes successfully, you can modify these settings to suit your deployment.

Note

Application gateways created with the basic WAF configuration are configured with CRS 3.0 for protections.

Next steps

To configure a custom domain alias for the public IP address, you can use Azure DNS or another DNS provider.

To configure diagnostic logging to log the events that are detected or prevented with WAF, see Application Gateway diagnostics.

To create custom health probes, see Create a custom health probe.

To configure SSL offloading and take the costly SSL subscription off your web servers, see Configure SSL offload.