Upgrade Web Application Firewall policies using Azure PowerShell

Article
05/23/2023

This script makes it easy to transition from a WAF config, or a custom rules-only WAF policy, to a full WAF policy. You might see a warning in the portal that says upgrade to WAF policy, or you might want the new WAF features such as Geomatch custom rules, per-site WAF policy, and per-URI WAF policy, or the bot mitigation ruleset. To use any of these features, you need a full WAF policy associated to your application gateway.

For more information about creating a new WAF policy, see Create Web Application Firewall policies for Application Gateway. For information about migrating, see upgrade to WAF policy.

To upgrade to WAF policy using the migration script

Use the following steps to run the migration script:

Open the following Cloud Shell window, or open one from within the portal.
Copy the script into the Cloud Shell window and run it.
The script asks for Subscription ID, Resource Group name, the name of the Application Gateway that the WAF config is associated with, and the name of the new WAF policy that you create. Once you enter these inputs, the script runs and creates your new WAF policy
Verify the new WAF policy is associated with your application gateway. Go to the WAF policy in the portal and select the Associated Application Gateways tab. Verify the Application Gateway is associated with the WAF policy.

Note

The script does not complete a migration if the following conditions exist:

An entire ruleset is disabled. To complete a migration, make sure an entire rulegroup is not disabled.

For more information, see the ValidateInput function in the script.

<#PSScriptInfo
.DESCRIPTION
Will be used to upgrade to the application-gateway to a top level waf policy experience.

.VERSION 1.0

.GUID b6fedd43-ebd0-41ed-9847-4f1c1c43be22

.AUTHOR Venkat.Krishnan

.PARAMETER subscriptionId 
Subscription Id of where the resources are present.
.PARAMETER resourceGroupName
Resource-group where the resources are present.
.PARAMETER applicationGatewayName
Application-Gateway name
.PARAMETER wafPolicyName
Name of the web application firewall policy

.EXAMPLE
./migrateToWafPolicy.ps1 -subscriptionId  <your-subscription-id> -applicationGatewayName <your-appgw-name> -resourceGroupName <your-resource-group-name> -wafPolicyName <new-waf-policy-name>
#>

param(
    [Parameter(Mandatory=$true)]
    [string] $subscriptionId,
    [Parameter(Mandatory=$true)]
    [string] $resourceGroupName,
    [Parameter(Mandatory=$true)]
    [string] $applicationGatewayName,
    [Parameter(Mandatory=$true)]
    [string] $wafPolicyName
)

function ValidateInput ($appgwName, $resourceGroupName) {
    # Obtain the application-gateway
    $appgw = Get-AzApplicationGateway -Name $applicationGatewayName -ResourceGroupName $resourceGroupName
    if (-not $appgw) {
        Write-Error "ApplicationGateway: $applicationGatewayName is not present in ResourceGroup: $resourceGroupName"
        return $false
    }

    # Check if already have a global firewall policy
    if ($appgw.FirewallPolicy) {
        $fp = Get-AzResource -ResourceId $appgw.FirewallPolicy.Id
        if ($fp.PolicySettings) {
            Write-Error "ApplicationGateway: $applicationGatewayName already has a global firewall policy: $fp.Name. Please use portal for changing the policy."
            return $false
        }
    }

    if ($appgw.WebApplicationFirewallConfiguration) {
        # Throw an error, since ruleGroup disabled case can't be migrated now.
        if ($appgw.WebApplicationFirewallConfiguration.DisabledRuleGroups) {
            foreach ($disabled in $appgw.WebApplicationFirewallConfiguration.DisabledRuleGroups) {
                if ($disabled.Rules.Count -eq 0) {
                    $ruleGroupName = $disabled.RuleGroupName
                    Write-Error "The ruleGroup '$ruleGroupName' is disabled. Currently we can't upgrade to a firewall policy when an entire ruleGroup is disabled. This feature will be delivered shortly. To continue, kindly ensure the entire rulegroups are not disabled. "
                    return $false
                }
            }
        }
    }

    if ($appgw.Sku.Name -ne "WAF_v2" -or $appgw.Sku.Tier -ne "WAF_v2") {
        Write-Error " Cannot associate a firewall policy to application gateway :$applicationGatewayName since the Sku is not on WAF_v2"
        return $false
    }

    return $true
}

function Login() {
    $context = Get-AzContext
    if ($null -eq $context -or $null -eq $context.Account) {
        Login-AzAccount
    }
}

function createNewTopLevelWafPolicy ($subscriptionId, $resourceGroupName, $applicationGatewayName, $wafPolicyName) {
    Select-AzSubscription -Subscription $subscriptionId
    $retVal = ValidateInput -appgwName $applicationGatewayName -resourceGroupName $resourceGroupName
    if (!$retVal) {
        return
    }

    $appgw = Get-AzApplicationGateway -Name $applicationGatewayName -ResourceGroupName $resourceGroupName

    # Get the managedRule and PolicySettings
    $managedRule = New-AzApplicationGatewayFirewallPolicyManagedRule
    $policySetting = New-AzApplicationGatewayFirewallPolicySetting
    if ($appgw.WebApplicationFirewallConfiguration) {
        $ruleGroupOverrides = [System.Collections.ArrayList]@()
        if ($appgw.WebApplicationFirewallConfiguration.DisabledRuleGroups) {
            foreach ($disabled in $appgw.WebApplicationFirewallConfiguration.DisabledRuleGroups) {
                $rules = [System.Collections.ArrayList]@()
                if ($disabled.Rules.Count -gt 0) {
                    foreach ($rule in $disabled.Rules) {
                        $ruleOverride = New-AzApplicationGatewayFirewallPolicyManagedRuleOverride -RuleId $rule
                        $_ = $rules.Add($ruleOverride)
                    }
                }
                
                $ruleGroupOverride = New-AzApplicationGatewayFirewallPolicyManagedRuleGroupOverride -RuleGroupName $disabled.RuleGroupName -Rule $rules
                $_ = $ruleGroupOverrides.Add($ruleGroupOverride)
            }
        }

        $managedRuleSet = New-AzApplicationGatewayFirewallPolicyManagedRuleSet -RuleSetType $appgw.WebApplicationFirewallConfiguration.RuleSetType -RuleSetVersion $appgw.WebApplicationFirewallConfiguration.RuleSetVersion 
        if ($ruleGroupOverrides.Count -ne 0) {
            $managedRuleSet = New-AzApplicationGatewayFirewallPolicyManagedRuleSet -RuleSetType $appgw.WebApplicationFirewallConfiguration.RuleSetType -RuleSetVersion $appgw.WebApplicationFirewallConfiguration.RuleSetVersion -RuleGroupOverride $ruleGroupOverrides
        }
    
        $exclusions = [System.Collections.ArrayList]@()  
        if ($appgw.WebApplicationFirewallConfiguration.Exclusions) {
            foreach ($excl in $appgw.WebApplicationFirewallConfiguration.Exclusions) {
                if ($excl.MatchVariable -and $excl.SelectorMatchOperator -and $excl.Selector) {
                    $exclusionEntry = New-AzApplicationGatewayFirewallPolicyExclusion -MatchVariable  $excl.MatchVariable -SelectorMatchOperator $excl.SelectorMatchOperator -Selector $excl.Selector
                    $_ = $exclusions.Add($exclusionEntry)
                }

                if ($excl.MatchVariable -and !$excl.SelectorMatchOperator -and !$excl.Selecto) {
                    # Equals Any exclusion
                    $exclusionEntry = New-AzApplicationGatewayFirewallPolicyExclusion -MatchVariable  $excl.MatchVariable -SelectorMatchOperator "EqualsAny" -Selector "*"
                    $_ = $exclusions.Add($exclusionEntry)
                }
            }
        }
    
        $managedRule = New-AzApplicationGatewayFirewallPolicyManagedRule -ManagedRuleSet $managedRuleSet
        $exclCount = $exclusions.Count
        if ($exclCount -ne 0) {
            $managedRule = New-AzApplicationGatewayFirewallPolicyManagedRule -ManagedRuleSet $managedRuleSet -Exclusion $exclusions
        }

        
        $policySetting = New-AzApplicationGatewayFirewallPolicySetting -MaxFileUploadInMb $appgw.WebApplicationFirewallConfiguration.FileUploadLimitInMb -MaxRequestBodySizeInKb $appgw.WebApplicationFirewallConfiguration.MaxRequestBodySizeInKb -Mode Detection -State Disabled
        if ($appgw.WebApplicationFirewallConfiguration.FirewallMode -eq "Prevention") {
            $policySetting.Mode = "Prevention"
        }

        if ($appgw.WebApplicationFirewallConfiguration.Enabled) {
            $policySetting.State = "Enabled"
        }

        $policySetting.RequestBodyCheck = $appgw.WebApplicationFirewallConfiguration.RequestBodyCheck;
    }

    if ($appgw.FirewallPolicy) {
        $customRulePolicyId = $appgw.FirewallPolicy.Id
        $rg = Get-AzResourceGroup -Id $customRulePolicyId
        $crPolicyName = $customRulePolicyId.Substring($customRulePolicyId.LastIndexOf("/") + 1)
        $customRulePolicy = Get-AzApplicationGatewayFirewallPolicy -ResourceGroupName $rg.ResourceGroupName -Name $crPolicyName
        $wafPolicy = New-AzApplicationGatewayFirewallPolicy -ResourceGroupName $rg.ResourceGroupName -Name $wafPolicyName -CustomRule $customRulePolicy.CustomRules -ManagedRule $managedRule -PolicySetting $policySetting -Location $appgw.Location
    } else { 
        $wafPolicy = New-AzApplicationGatewayFirewallPolicy -Name $wafPolicyName -ResourceGroupName $resourceGroupName -PolicySetting $policySetting -ManagedRule $managedRule -Location $appgw.Location
    }

    if (!$wafPolicy) {
        return
    }

    $appgw.WebApplicationFirewallConfiguration = $null
    $appgw.FirewallPolicy = $wafPolicy
    $appgw = Set-AzApplicationGateway -ApplicationGateway $appgw
    Write-Host " firewallPolicy: $wafPolicyName has been created/updated successfully and applied to applicationGateway: $applicationGatewayName!"
    return $wafPolicy
}

function Main() {
    Login
    $policy = createNewTopLevelWafPolicy -subscriptionId $subscriptionId -resourceGroupName $resourceGroupName -applicationGatewayName $applicationGatewayName -wafPolicyName $wafPolicyName
    return $policy
}

Main

Next steps

Learn more about Web Application Firewall CRS rule groups and rules.

Upgrade Web Application Firewall policies using Azure PowerShell

To upgrade to WAF policy using the migration script

Next steps

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