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Secure User Authentication in Azure Using Microsoft.Identity.Client

Overview

User authentication is a fundamental aspect of many applications, and Azure provides robust identity management capabilities through Azure Active Directory (Azure AD). In this article, we will explore how to securely authenticate users in Azure using Microsoft.Identity.Client (MSAL) library in C#. We will cover the step-by-step process, including code examples, to authenticate a user and retrieve an access token for further interaction with Azure services or protected APIs.

Prerequisites

Before proceeding, ensure that we have the following prerequisites

  • Azure AD application registered in our Azure portal.
  • The Microsoft.Identity.Client package installed in our project.

Step 1. Set Up Azure AD Authentication Parameters

Start by defining the necessary parameters for Azure AD authentication in our C# code by Replacing "OurAzureADClientId" with our Azure AD client ID and "OurAzureADTenantId" with our Azure AD tenant ID. Additionally, adjust the scopes and redirect URI as per our application's requirements.

using Microsoft.Identity.Client;
using System;

string clientId = "OurAzureADClientId";
string authority = "https://login.microsoftonline.com/OurAzureADTenantId";
string[] scopes = new[] { "User.Read" };
string redirectUri = "http://localhost";

Step 2. Create a PublicClientApplication Instance

Next, create an instance of the PublicClientApplication class using the parameters defined in the previous step. This sets up the client application with the necessary configurations for Azure AD authentication.

IPublicClientApplication app = PublicClientApplicationBuilder
    .Create(clientId)
    .WithAuthority(authority)
    .WithRedirectUri(redirectUri)
    .Build();

Step 3. Initiate the User Authentication Flow

To authenticate the user, initiate the interactive authentication flow using the AcquireTokenInteractive method. This code prompts the user to sign in and consent to the requested scopes. Upon successful authentication, it retrieves the authentication result containing the access token and user account information.

var authResult = await app.AcquireTokenInteractive(scopes)
    .ExecuteAsync();

Step 4. Access User Information

Finally, access and utilize the authenticated user's information as per our application's requirements. For example, we can display the user's name and access token in the console as We can further utilize the access token to interact with Azure services or protected APIs on behalf of the authenticated user.

Console.WriteLine($"Welcome, {authResult.Account.Username}!");
Console.WriteLine($"Access token: {authResult.AccessToken}");

Summary

In this article, we explored how to securely authenticate users in Azure using Microsoft.Identity.Client library in C#. We can implement robust user authentication in our Azure applications by following the step-by-step process and incorporating the provided code examples. Remember to handle exceptions, validate user input, and implement appropriate security measures to ensure the overall security of our application's authentication flow.


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