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Authenticate Node.js apps to Azure services during local development using developer accounts

During local development, applications need to authenticate to Azure to access various Azure services. Two common approaches for local authentication are to use a service principal or to use a developer account. This article explains how to use a developer account. In the sections ahead, you learn:

  • How to use Microsoft Entra groups to efficiently manage permissions for multiple developer accounts
  • How to assign roles to developer accounts to scope permissions
  • How to sign-in to supported local development tools
  • How to authenticate using a developer account from your app code

For an app to authenticate to Azure during local development using the developer's Azure credentials, the developer must be signed-in to Azure from one of the following developer tools:

  • Azure CLI
  • Azure Developer CLI
  • Azure PowerShell

The Azure Identity library can detect that the developer is signed-in from one of these tools. The library can then obtain the Microsoft Entra access token via the tool to authenticate the app to Azure as the signed-in user.

This approach takes advantage of the developer's existing Azure accounts to streamline the authentication process. However, a developer's account likely has more permissions than required by the app, therefore exceeding the permissions the app runs with in production. As an alternative, you can create application service principals to use during local development, which can be scoped to have only the access needed by the app.

Create a Microsoft Entra group for local development

Create a Microsoft Entra group to encapsulate the roles (permissions) the app needs in local development rather than assigning the roles to individual service principal objects. This approach offers the following advantages:

  • Every developer has the same roles assigned at the group level.
  • If a new role is needed for the app, it only needs to be added to the group for the app.
  • If a new developer joins the team, a new application service principal is created for the developer and added to the group, ensuring the developer has the right permissions to work on the app.

  1. Navigate to the Microsoft Entra ID overview page in the Azure portal.

  2. Select All groups from the left-hand menu.

  3. On the Groups page, select New group.

  4. On the New group page, fill out the following form fields:

    • Group type: Select Security.
    • Group name: Enter a name for the group that includes a reference to the app or environment name.
    • Group description: Enter a description that explains the purpose of the group.

    A screenshot showing how to create a group in the Azure portal.

  5. Select the No members selected link under Members to add members to the group.

  6. In the flyout panel that opens, search for the service principal you created earlier and select it from the filtered results. Choose the Select button at the bottom of the panel to confirm your selection.

  7. Select Create at the bottom of the New group page to create the group and return to the All groups page. If you don't see the new group listed, wait a moment and refresh the page.

Assign roles to the group

Next, determine what roles (permissions) your app needs on what resources and assign those roles to the Microsoft Entra group you created. Groups can be assigned a role at the resource, resource group, or subscription scope. This example shows how to assign roles at the resource group scope, since most apps group all their Azure resources into a single resource group.

  1. In the Azure portal, navigate to the Overview page of the resource group that contains your app.

  2. Select Access control (IAM) from the left navigation.

  3. On the Access control (IAM) page, select + Add and then choose Add role assignment from the drop-down menu. The Add role assignment page provides several tabs to configure and assign roles.

  4. On the Role tab, use the search box to locate the role you want to assign. Select the role, and then choose Next.

  5. On the Members tab:

    • For the Assign access to value, select User, group, or service principal .
    • For the Members value, choose + Select members to open the Select members flyout panel.
    • Search for the Microsoft Entra group you created earlier and select it from the filtered results. Choose Select to select the group and close the flyout panel.
    • Select Review + assign at the bottom of the Members tab.

    A screenshot showing how to assign a role to the Microsoft Entra group.

  6. On the Review + assign tab, select Review + assign at the bottom of the page.

Sign-in to Azure using developer tooling

Next, sign-in to Azure using one of several developer tools that can be used to perform authentication in your development environment. The account you authenticate should also exist in the Microsoft Entra group you created and configured earlier.

Developers can use Azure CLI to authenticate to Microsoft Entra ID. Apps using DefaultAzureCredential or AzureCliCredential can then use this account to authenticate app requests when running locally.

To authenticate with the Azure CLI, run the az login command. On a system with a default web browser, the Azure CLI launches the browser to authenticate the user.

az login

For systems without a default web browser, the az login command uses the device code authentication flow. The user can also force the Azure CLI to use the device code flow rather than launching a browser by specifying the --use-device-code argument.

az login --use-device-code

Authenticate to Azure services from your app

The Azure Identity library provides various credentials—implementations of TokenCredential adapted to supporting different scenarios and Microsoft Entra authentication flows. The steps ahead demonstrate how to use DefaultAzureCredential when working with user accounts locally.

Implement the code

DefaultAzureCredential is an opinionated, ordered sequence of mechanisms for authenticating to Microsoft Entra ID. Each authentication mechanism is a class derived from the TokenCredential class and is known as a credential. At runtime, DefaultAzureCredential attempts to authenticate using the first credential. If that credential fails to acquire an access token, the next credential in the sequence is attempted, and so on, until an access token is successfully obtained. In this way, your app can use different credentials in different environments without writing environment-specific code.

To use DefaultAzureCredential, add the @azure/identity packages to your application. In a terminal of your choice, navigate to the application project directory and run the following command:

npm install @azure/identity

Azure services are accessed using specialized client classes from the various Azure SDK client libraries. These classes and your own custom services should be registered so they can be accessed throughout your app. Complete the following programmatic steps to create a client class and DefaultAzureCredential:

  1. Import the @azure/identity package.
  2. Create the Azure service client, and pass to it a new instance of DefaultAzureCredential.
import { DefaultAzureCredential } from "@azure/identity";
import { SomeAzureServiceClient } from "@azure/arm-some-service";

const client = new SomeAzureServiceClient(new DefaultAzureCredential());