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Tutorial: Prepare your external tenant to authenticate users in an ASP.NET Core web app

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This tutorial series demonstrates how to build an ASP.NET Core web application and prepare it for authentication using the Microsoft Entra admin center. You'll use the Microsoft Authentication Library for .NET and Microsoft Identity Web libraries to authenticate your app with your external tenant. Finally, you'll run the application and test the sign-in and sign-out experiences.

In this tutorial, you'll;

  • Register a web application in the Microsoft Entra admin center, and record its identifiers
  • Create a client secret for the web application
  • Define the platform and URLs
  • Grant permissions to the web application to access the Microsoft Graph API
  • Create a sign in and sign out user flow in the Microsoft Entra admin center
  • Associate your web application with the user flow

Prerequisites

  • An external tenant. If you don't have one, create a trial tenant or a tenant with a subscription before you begin.
  • This Azure account must have permissions to manage applications. Any of the following Microsoft Entra roles include the required permissions:
    • Application Administrator
    • Application Developer
    • Cloud Application Administrator

Register the web app and record identifiers

To enable your application to sign in users with Microsoft Entra, Microsoft Entra External ID must be made aware of the application you create. The app registration establishes a trust relationship between the app and Microsoft Entra. When you register an application, External ID generates a unique identifier known as an Application (client) ID, a value used to identify your app when creating authentication requests.

The following steps show you how to register your app in the Microsoft Entra admin center:

  1. Sign in to the Microsoft Entra admin center as at least an Application Developer.

  2. If you have access to multiple tenants, use the Settings icon in the top menu to switch to your external tenant from the Directories + subscriptions menu.

  3. Browse to Identity >Applications > App registrations.

  4. Select + New registration.

  5. In the Register an application page that appears;

    1. Enter a meaningful application Name that is displayed to users of the app, for example ciam-client-app.
    2. Under Supported account types, select Accounts in this organizational directory only.

  6. Select Register.

  7. The application's Overview pane displays upon successful registration. Record the Application (client) ID to be used in your application source code.

Add a platform redirect URL

To specify your app type to your app registration, follow these steps:

  1. Under Manage, select Authentication.
  2. On the Platform configurations page, select Add a platform, and then select Web option.
  3. For the Redirect URIs enter https://localhost:7274/signin-oidc.
  4. Under Front-channel logout URL, enter https://localhost:7274/signout-callback-oidc for signing out.
  5. Select Configure to save your changes.

Add app client secret

Create a client secret for the registered application. The application uses the client secret to prove its identity when it requests for tokens.

  1. From the App registrations page, select the application that you created (such as ciam-client-app) to open its Overview page.
  2. Under Manage, select Certificates & secrets.
  3. Select New client secret.
  4. In the Description box, enter a description for the client secret (for example, ciam app client secret).
  5. Under Expires, select a duration for which the secret is valid (per your organizations security rules), and then select Add.
  6. Record the secret's Value. You'll use this value for configuration in a later step. The secret value won't be displayed again, and isn't retrievable by any means, after you navigate away from the Certificates and secrets. Make sure you record it.

Grant API permissions

  1. From the App registrations page, select the application that you created (such as ciam-client-app) to open its Overview page.

  2. Under Manage, select API permissions.

  3. Under Configured permissions, select Add a permission.

  4. Select Microsoft APIs tab.

  5. Under Commonly used Microsoft APIs section, select Microsoft Graph.

  6. Select Delegated permissions option.

  7. Under Select permissions section, search for and select both openid and offline_access permissions.

  8. Select the Add permissions button.

  9. At this point, you've assigned the permissions correctly. However, since the tenant is a customer's tenant, the consumer users themselves can't consent to these permissions. You as the admin must consent to these permissions on behalf of all the users in the tenant:

    1. Select Grant admin consent for <your tenant name>, then select Yes.
    2. Select Refresh, then verify that Granted for <your tenant name> appears under Status for both scopes.

Create a user flow

Follow these steps to create a user flow a customer can use to sign in or sign up for an application.

  1. Sign in to the Microsoft Entra admin center as at least an External ID User Flow Administrator.

  2. If you have access to multiple tenants, use the Settings icon in the top menu to switch to your external tenant from the Directories + subscriptions menu.

  3. Browse to Identity > External Identities > User flows.

  4. Select + New user flow.

  5. On the Create page:

    1. Enter a Name for the user flow, such as SignInSignUpSample.

    2. In the Identity providers list, select Email Accounts. This identity provider allows users to sign-in or sign-up using their email address.

      Note

      Additional identity providers will be listed here only after you set up federation with them. For example, if you set up federation with Google or Facebook, you'll be able to select those additional identity providers here.

    3. Under Email accounts, you can select one of the two options. For this tutorial, select Email with password.

      • Email with password: Allows new users to sign up and sign in using an email address as the sign-in name and a password as their first factor credential.
      • Email one-time-passcode: Allows new users to sign up and sign in using an email address as the sign-in name and email one-time passcode as their first factor credential. Email one-time passcode must be enabled at the tenant level (All Identity Providers > Email One-time-passcode) for this option to be available at the user flow level.

    4. Under User attributes, choose the attributes you want to collect from the user upon sign-up. By selecting Show more, you can choose attributes and claims for Country/Region, Display Name, and Postal Code. Select OK. (Users are only prompted for attributes when they sign up for the first time.)

  6. Select Create. The new user flow appears in the User flows list. If necessary, refresh the page.

To enable self-service password reset, use the steps in Enable self-service password reset article.

Associate the web application with the user flow

Although many applications can be associated with your user flow, a single application can only be associated with one user flow. A user flow allows configuration of the user experience for specific applications. For example, you can configure a user flow that requires users to sign in or sign up with email address.

  1. On the sidebar menu, select Identity.

  2. Select External Identities, then User flows.

  3. In the User flows page, select the User flow name you created earlier, for example, SignInSignUpSample.

  4. Under Use, select Applications.

  5. Select Add application.

  6. Select the application from the list such as ciam-client-app or use the search box to find the application, and then select it.

  7. Choose Select.

Next steps

Part 2: Prepare an ASP.NET Core web app for authentication in an external tenant