Creating a Service Principal in Azure

An Azure service principal is a security identity used by user-created apps, services, and automation tools to access specific Azure resources. Service Principals allow you to provision an account that only has enough permissions and scope to run a task within a predefined set of Azure resources. Think of it as a 'user identity' (login and password or certificate) with a specific role, and tightly controlled permissions to access your resources. It only needs to be able to do specific things, unlike a general user identity.

Using a Service Principal improves security if you only grant it the minimum permission levels needed to perform its specific tasks. Service Principals with locked down permissions are easier to provision, monitor and de-provision if something goes wrong. Service Principals rely on a corresponding Azure Active Directory application.

In order to use a Service Principal, you will need the following:

An Application ID Uniform Resource Identifier, also known as a URI, is used to identify a logical or physical resource.
A Secret key
And the tenant ID, also known as our Active Directory ID

The URI and Secret key will be used to authenticate in place of a user name and password.

Check Azure Active Directory Permissions

Log in to your Azure Account through the Azure portal.
Click on the hamburger menu in the top left and select Azure Active Directory.

In Azure Active Directory Overview, select Users.
Select User settings.

Check whether the App registrations setting is Yes or No.

App Registrations Permissions

The App registrations setting must me set to Yes in order for any user within the AD tenant to register an app.
If the App registrations setting is set to No, only administrative users can register an app.

If the App registrations setting is set to No, you can check whether your account is an admin or a user for the Azure AD tenant.
Return to the Azure Active Directory Overview page.
Select Roles and administrators from the side bar.

From All roles, you can see Your Role.

Administrator Access

If your account is assigned to the User role, but the App registrations setting from the preceding steps is limited to administrative users, ask your administrator to either assign you to an administrative role, or to enable users to register apps.

Check Azure subscription permissions

In your Azure subscription, your account must have Microsoft.Authorization/*/Write access to assign an AD app to a role. This action is granted through the Owner role or User Access Administrator role. If your account is assigned to the Contributor role, you do not have adequate permission. You receive an error when attempting to assign the service principal to a role.

Click on the hamburger menu from the top left and select Azure Active Directory.

From the Azure Active Directory Overview page, select Users.

From the All users tab, search for and click on your name.

Select Azure role assignment.

View your assigned roles, and determine if you have adequate permissions to assign an AD application to a role.

Request Permissions

If you do not have adequate permissions, ask your subscription administrator to add you to the User Access Administrator role.

Create an Azure Active Directory Application

Log in to your Azure Account through the Azure portal.
Click on the hamburger menu in the top left and select Azure Active Directory.

Select App registrations.

Select New registration.

Name - Choose a user-facing display name for your application.
Supported account types - Choose can use the application or access the API.
Redirect URI - Enter a URI to return the authentication response to after successfully authenticating the user.

Once the configuration is complete, click Register.

Get Application ID and Client Secret

When programmatically logging in, you need the ID for your application and an authentication key.

To get those values, use the following steps:

From App registrations in Azure Active Directory, select your application.

Copy the Application (client) ID

To generate a Client secret, click Certificates & secrets.
Click the Client secrets tab.
Click New client secret.

Description - Provide a description for your client secret.
Expires - Choose how long that your client secret should be valid for.

Best Practices

From a best practices standpoint, it is not suggested to have a secret that never expires.

Once configuration is complete, click Add.

After saving the key, the Value along with the Secret ID is displayed on the Certificates and secrets page.
View Value

You can only view the Value immediately after creation. Be certain to note this value down and store it in a safe place.
You provide the Client Secret Value along with the Application ID to log in as the application.

Get Tenant ID

When programmatically logging in, you need to pass the tenant ID with your authentication request.

Log in to your Azure Account through the Azure portal.
Click on the hamburger menu in the top left and select Azure Active Directory.

From your Azure Active Directory tenant, select Properties.
Your Tenant ID is available to copy.

Assign application to role

To access resources in your subscription, you must assign the application to a role. Decide which role represents the right permissions for the application. To learn about the available roles, see RBAC: Built in Roles.

You can set the scope at the level of the subscription, resource group, or resource. Permissions are inherited to lower levels of scope. For example, adding an application to the Reader role for a resource group means it can read the resource group and any resources it contains.

Navigate to the level of scope you wish to assign the application to.
In our example, we will assign the role to the resource group scope so we will select our preferred resource group.

Subscription

To assign at the subscription level, select Subscriptions from the Azure Management Portal and follow the same steps listed below.

Select Access control (IAM).

Select Add > Add role assignment.

From the Role tab, search for and select the role that you wish to assign to the application. In our case we are going to assign Reader.
Once done selecting, click Next.

From the Members tab, click on Select members.
A new blade will open on the right side of your screen titled Select members.
Search for your application and then click on it.
Once done, click Select.

Click Review + assign.

From the Review + assign tab, review your configurations.
If everything looks correct, click the Review + assign button.

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