Deploy Azure Policy to delegated subscriptions at scale

As a service provider, you may have onboarded multiple customer tenants to Azure Lighthouse. Azure Lighthouse allows service providers to perform operations at scale across several tenants at once, making management tasks more efficient.

This topic explains how to use Azure Policy to deploy a policy definition and policy assignment across multiple tenants using PowerShell commands. In this example, the policy definition ensures that storage accounts are secured by allowing only HTTPS traffic.

Use Azure Resource Graph to query across customer tenants

You can use Azure Resource Graph to query across all subscriptions in customer tenants that you manage. In this example, we'll identify any storage accounts in these subscriptions that do not currently require HTTPS traffic.

$MspTenant = "insert your managing tenantId here"

$subs = Get-AzSubscription

$ManagedSubscriptions = Search-AzGraph -Query "ResourceContainers | where type == 'microsoft.resources/subscriptions' | where tenantId != '$($mspTenant)' | project name, subscriptionId, tenantId" -subscription $subs.subscriptionId

Search-AzGraph -Query "Resources | where type =~ 'Microsoft.Storage/storageAccounts' | project name, location, subscriptionId, tenantId, properties.supportsHttpsTrafficOnly" -subscription $ManagedSubscriptions.subscriptionId | convertto-json

Deploy a policy across multiple customer tenants

The example below shows how to use an Azure Resource Manager template to deploy a policy definition and policy assignment across delegated subscriptions in multiple customer tenants. This policy definition requires all storage accounts to use HTTPS traffic. It prevents the creation of any new storage accounts that don't comply. Any existing storage accounts without the setting are marked as non-compliant.

Write-Output "In total, there are $($ManagedSubscriptions.Count) delegated customer subscriptions to be managed"

foreach ($ManagedSub in $ManagedSubscriptions)
{
    Select-AzSubscription -SubscriptionId $ManagedSub.subscriptionId

    New-AzSubscriptionDeployment -Name mgmt `
                     -Location eastus `
                     -TemplateUri "https://raw.githubusercontent.com/Azure/Azure-Lighthouse-samples/master/templates/policy-enforce-https-storage/enforceHttpsStorage.json" `
                     -AsJob
}

Validate the policy deployment

After you've deployed the Azure Resource Manager template, confirm that the policy definition was successfully applied by attempting to create a storage account with EnableHttpsTrafficOnly set to false in one of your delegated subscriptions. Because of the policy assignment, you should be unable to create this storage account.

New-AzStorageAccount -ResourceGroupName (New-AzResourceGroup -name policy-test -Location eastus -Force).ResourceGroupName `
                     -Name (get-random) `
                     -Location eastus `
                     -EnableHttpsTrafficOnly $false `
                     -SkuName Standard_LRS `
                     -Verbose                  

Clean up resources

When you're finished, remove the policy definition and assignment created by the deployment.

foreach ($ManagedSub in $ManagedSubscriptions)
{
    select-azsubscription -subscriptionId $ManagedSub.subscriptionId

    Remove-AzSubscriptionDeployment -Name mgmt -AsJob

    $Assignment = Get-AzPolicyAssignment | where-object {$_.Name -like "enforce-https-storage-assignment"}

    if ([string]::IsNullOrEmpty($Assignment))
    {
        Write-Output "Nothing to clean up - we're done"
    }
    else
    {

    Remove-AzPolicyAssignment -Name 'enforce-https-storage-assignment' -Scope "/subscriptions/$($ManagedSub.subscriptionId)" -Verbose

    Write-Output "Deployment has been deleted - we're done"
    }
}

Next steps

• Learn about Azure Policy.
• Learn about cross-tenant management experiences.
• Learn how to deploy a policy that can be remediated within a delegated subscription.