Azure Policy – Where to Start?

One of the positives of Azure is that it can offer you so many possibilities when it comes to deployment options. However, if you don’t implement the correct governance, this can very quickly become a negative. Historically, Cloud has had difficulties when it comes to sprawl; Azure Policy is a service that will help prevent that.

Azure Policy isn’t only a tool for prevention either. With the right policies, you can audit and enhance your environment in terms of efficiency, security and compliance. This gives you greater insight into your Azure deployment and confidence in your requirements.

Governance in Azure is addressed in many ways; a good place to start for overall strategy is the Azure Architecture Center. It has specific sections on Governance as well as overall design guidelines.

So how does Azure Policy work? At its core, it is an assessment service. You create policies with specific rules and scopes. Once the policies are active, they audit all resources in the included scope for compliance. Policies can range in complexity; you can use the default templates or create a custom one to meet your needs.

There are two core areas when dealing with Azure Policy:

Policy Definition

Every policy must have a definition. The definition contains all the details of the conditions under which it’s enforced. It also has the defined effect that occurs if the conditions are met. Definitions are created using JSON and the full structure is defined here. You will need familiarity with this if you are going to write your own custom policies.

Allowed Locations Policy Example:

{
    "properties": {
        "mode": "all",
        "parameters": {
            "allowedLocations": {
                "type": "array",
                "metadata": {
                    "description": "The list of locations that can be specified when deploying resources",
                    "strongType": "location",
                    "displayName": "Allowed locations"
                },
                "defaultValue": [ "westus2" ]
            }
        },
        "displayName": "Allowed locations",
        "description": "This policy enables you to restrict the locations your organization can specify when deploying resources.",
        "policyRule": {
            "if": {
                "not": {
                    "field": "location",
                    "in": "[parameters('allowedLocations')]"
                }
            },
            "then": {
                "effect": "deny"
            }
        }
    }
}
Policy Assignment

A policy assignment is a policy definition that has been assigned to take place within a specific scope. Assignments range from Management Groups to a single Resource Group. The scope of the assignment refers to all the Resource Groups, Subscriptions, or Management Groups that the Definition is assigned to. Inheritance is enabled for all assignments. Therefore, a policy applied to a resource group is also applied to all resources in that resource group. However, you can include exclusions as a sub-scope of the assignment. For example, a Definition is assigned to a Subscription; all Resource Groups inherit the Definition but you need a single Resource Group excluded. Rather than redo the Assignment for each Resource Group, you can simply exclude it from the Subscription assignment.

Your First Policy

Now that you understand what Azure Policy is, let’s get started with our first policy. For this example, I’m going to prevent Public IP addresses being deployed within a Subscription. This is something I commonly add to IaaS projects that are connected to a local LAN.

Once you’ve logged in to the Azure Portal, make your way to the Azure Policy service, I normally use the search bar as below as it’s quick!

Once you’re on the Overview blade, a handy option for your first time is to click the Getting Started option. This details the steps to take and we’re going to start by browsing default Definitions so click that View Definitions option as below:

This will bring you to the Definitions blade. You will see a lot of built-in policies. To simplify things, click the search bar and enter “not allowed”, this will bring up the Definition we will use, then go ahead and click on the Policy name “Not allowed resource types” as below:

You’re now in the Definition page, where you can see the exact structure in JSON format. We’re going to jump straight to Assignment from here by clicking “Assign” as below:

This will bring you the assignment blade. Our first step is to set a scope. I’m going to go ahead and choose my Subscription and a Resource Group, then click “Select” as below:

We’re going to leave most of the settings as they are, but you can where you can set Exclusions below. We’re going to click the drop down arrow as highlighted:

This opens a huge list of resource providers and types. Thankfully, there is a search bar, so type in “public” to narrow the list and tick the checkbox for Microsoft.Network/publicIPAddresses, then click away from the list as below:

We’re almost there! You can see that publicIPAddresses are now defined as a parameter. So click the blue “Assign” button as below:

Now your policy is assigned, we need to give it a couple of minutes to propagate. Now, when I try to create a Public IP resource in my scoped Resource Group (I’ve used POSH in Cloudshell, but deployment method doesn’t matter) I’m told I cannot as it’s disallowed by policy:

You’ve now successfully applied your first Azure Policy! As you can see, even though this is a single Definition it is still very powerful. Your options to layer Definitions and apply custom ones allow for full control of your environment with very little effort. Azure Policy should be high on your list of priorities for your Azure deployments.

As always, if there are any questions, please get in touch!

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