Create an Azure service principal with Azure PowerShell

Article
10/08/2024

Warning

The AzureRM PowerShell module has been officially deprecated as of February 29, 2024. Users are advised to migrate from AzureRM to the Az PowerShell module to ensure continued support and updates.

Although the AzureRM module may still function, it's no longer maintained or supported, placing any continued use at the user's discretion and risk. Please refer to our migration resources for guidance on transitioning to the Az module.

If you plan to manage your app or service with Azure PowerShell, you should run it under an Azure Microsoft Entra service principal, rather than your own credentials. This article steps you through creating a security principal with Azure PowerShell.

Note

You can also create a service principal through the Azure portal. Read Use portal to create Active Directory application and service principal that can access resources for more details.

What is a 'service principal'?

An Azure service principal is a security identity used by user-created apps, services, and automation tools to access specific Azure resources. Think of it as a 'user identity' (username and password or certificate) with a specific role, and tightly controlled permissions. A service principal should only need to do specific things, unlike a general user identity. It improves security if you only grant it the minimum permissions level needed to perform its management tasks.

Verify your own permission level

First, you must have sufficient permissions in both your Microsoft Entra ID and your Azure subscription. You must be able to create an app in the Active Directory and assign a role to the service principal.

The easiest way to check whether your account has the right permissions is through the portal. See Check required permission in portal.

Create a service principal for your app

Once signed in to your Azure account, you can create the service principal. You must have one of the following ways to identify your deployed app:

The unique name of your deployed app, such as "MyDemoWebApp" in the following examples, or
the Application ID, the unique GUID associated with your deployed app, service, or object

Get information about your application

The Get-AzureRmADApplication cmdlet can be used to get information about your application.

Get-AzureRmADApplication -DisplayNameStartWith MyDemoWebApp

DisplayName             : MyDemoWebApp
ObjectId                : 775f64cd-0ec8-4b9b-b69a-8b8946022d9f
IdentifierUris          : {http://MyDemoWebApp}
HomePage                : http://www.contoso.com
Type                    : Application
ApplicationId           : 00001111-aaaa-2222-bbbb-3333cccc4444
AvailableToOtherTenants : False
AppPermissions          :
ReplyUrls               : {}

Create a service principal for your application

The New-AzureRmADServicePrincipal cmdlet is used to create the service principal.

$servicePrincipal = New-AzureRmADServicePrincipal -ApplicationId 00001111-aaaa-2222-bbbb-3333cccc4444

Secret                : System.Security.SecureString
ServicePrincipalNames : {00001111-aaaa-2222-bbbb-3333cccc4444, http://MyDemoWebApp}
ApplicationId         : 00001111-aaaa-2222-bbbb-3333cccc4444
DisplayName           : MyDemoWebApp
Id                    : 698138e7-d7b6-4738-a866-b4e3081a69e4
AdfsId                :
Type                  : ServicePrincipal

From here, you can either directly use the $servicePrincipal.Secret property in Connect-AzureRmAccount (see "Sign in using the service principal" below), or you can convert this SecureString to a plain text string for later usage:

$BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($servicePrincipal.Secret)
$password = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR)
[Runtime.InteropServices.Marshal]::ZeroFreeBSTR($BSTR)

You can now sign in as the new service principal for your app using the appId you provided and password that was automatically generated. You also need the Tenant ID for the service principal. Your Tenant ID is displayed when you sign into Azure with your personal credentials. To sign in with a service principal, use the following commands:

$cred = New-Object System.Management.Automation.PSCredential ("00001111-aaaa-2222-bbbb-3333cccc4444", $servicePrincipal.Secret)
Connect-AzureRmAccount -Credential $cred -ServicePrincipal -TenantId 00000000-0000-0000-0000-000000000000

After a successful sign-in you see output like:

Environment           : AzureCloud
Account               : 00001111-aaaa-2222-bbbb-3333cccc4444
TenantId              : 00000000-0000-0000-0000-000000000000
SubscriptionId        :
SubscriptionName      :
CurrentStorageAccount :

Congratulations! You can use these credentials to run your app. Next, you need to adjust the permissions of the service principal.

Managing roles

Note

Azure Role-Based Access Control (RBAC) is a model for defining and managing roles for user and service principals. Roles have sets of permissions associated with them, which determine the resources a principal can read, access, write, or manage. For more information on RBAC and roles, see RBAC: Built-in roles.

Azure PowerShell provides the following cmdlets to manage role assignments:

The default role for a service principal is Contributor. It may not be the best choice depending on the scope of your app's interactions with Azure services, given its broad permissions. The Reader role is more restrictive and can be a good choice for read-only apps. You can view details on role-specific permissions or create custom ones through the Azure portal.

In this example, we add the Reader role to our prior example, and delete the Contributor one:

New-AzureRmRoleAssignment -ResourceGroupName myRG -ObjectId 698138e7-d7b6-4738-a866-b4e3081a69e4 -RoleDefinitionName Reader

RoleAssignmentId   : /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myRG/providers/Microsoft.Authorization/roleAssignments/818892f2-d075-46a1-a3a2-3a4e1a12fcd5
Scope              : /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myRG
DisplayName        : MyDemoWebApp
SignInName         :
RoleDefinitionName : Reader
RoleDefinitionId   : b24988ac-6180-42a0-ab88-20f7382dd24c
ObjectId           : 698138e7-d7b6-4738-a866-b4e3081a69e4
ObjectType         : ServicePrincipal

Remove-AzureRmRoleAssignment -ResourceGroupName myRG -ObjectId 698138e7-d7b6-4738-a866-b4e3081a69e4 -RoleDefinitionName Contributor

To view the current roles assigned:

Get-AzureRmRoleAssignment -ResourceGroupName myRG -ObjectId 698138e7-d7b6-4738-a866-b4e3081a69e4

RoleAssignmentId   : /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myRG/providers/Microsoft.Authorization/roleAssignments/0906bbd8-9982-4c03-8dae-aeaae8b13f9e
Scope              : /subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/myRG
DisplayName        : MyDemoWebApp
SignInName         :
RoleDefinitionName : Reader
RoleDefinitionId   : acdd72a7-3385-48ef-bd42-f606fba81ae7
ObjectId           : 698138e7-d7b6-4738-a866-b4e3081a69e4
ObjectType         : ServicePrincipal

Other Azure PowerShell cmdlets for role management:

Change the credentials of the security principal

It's a good security practice to review the permissions and update the password regularly. You may also want to manage and modify the security credentials as your app changes. For example, we can change the password of the service principal by creating a new password and removing the old one.

Add a new password for the service principal

New-AzureRmADSpCredential -ServicePrincipalName http://MyDemoWebApp

Secret    : System.Security.SecureString
StartDate : 11/16/2018 12:38:23 AM
EndDate   : 11/16/2019 12:38:23 AM
KeyId     : 00001111-aaaa-2222-bbbb-3333cccc4444
Type      : Password

Get a list of credentials for the service principal

Get-AzureRmADSpCredential -ServicePrincipalName http://MyDemoWebApp

StartDate           EndDate             KeyId                                Type
---------           -------             -----                                ----
3/8/2017 5:58:24 PM 3/8/2018 5:58:24 PM 00001111-aaaa-2222-bbbb-3333cccc4444 Password
5/5/2016 4:55:27 PM 5/5/2017 4:55:27 PM ca9d4846-4972-4c70-b6f5-a4effa60b9bc Password

Remove the old password from the service principal

Remove-AzureRmADSpCredential -ServicePrincipalName http://MyDemoWebApp -KeyId ca9d4846-4972-4c70-b6f5-a4effa60b9bc

Confirm
Are you sure you want to remove credential with keyId '00001111-aaaa-2222-bbbb-3333cccc4444' for
service principal objectId '698138e7-d7b6-4738-a866-b4e3081a69e4'.
[Y] Yes  [N] No  [S] Suspend  [?] Help (default is "Y"): Y

Verify the list of credentials for the service principal

Get-AzureRmADSpCredential -ServicePrincipalName http://MyDemoWebApp

StartDate           EndDate             KeyId                                Type
---------           -------             -----                                ----
3/8/2017 5:58:24 PM 3/8/2018 5:58:24 PM 00001111-aaaa-2222-bbbb-3333cccc4444 Password

Get information about the service principal

$svcprincipal = Get-AzureRmADServicePrincipal -ObjectId 698138e7-d7b6-4738-a866-b4e3081a69e4
$svcprincipal | Select-Object -Property *

ServicePrincipalNames : {http://MyDemoWebApp, 00001111-aaaa-2222-bbbb-3333cccc4444}
ApplicationId         : 00001111-aaaa-2222-bbbb-3333cccc4444
DisplayName           : MyDemoWebApp
Id                    : 698138e7-d7b6-4738-a866-b4e3081a69e4
Type                  : ServicePrincipal

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