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Blazor WebAssembly Custom Authentication From Scratch

In this article, we are going to explore and implement custom authentication from the scratch. In this sample, we will use JWT authentication for user authentication.

Main Building Blocks Of Blazor WebAssembly Authentication:

The core concepts of blazor webassembly authentication are:
  • AuthenticationStateProvider Service
  • AuthorizeView Component
  • Task<AuthenticationState> Cascading Property
  • CascadingAuthenticationState Component
  • AuthorizeRouteView Component
AuthenticationStateProvider Service - this provider holds the authentication information about the login user. The 'GetAuthenticationStateAsync()' method in the Authentication state provider returns user AuthenticationState. The 'NotifyAuthenticationStateChaged()' to notify the latest user information within the components which using this AuthenticationStateProvider.

AuthorizeView Component - displays different content depending on the user authorization state. This component uses the AuthenticationStateProvider service internally to get user information.

Task<AuthenticationState> Cascading Property - This property to get updated information about the user. So in any component to check user authenticated or to fetch claims of an authenticated user this cascading property need to be initialized in our components. We always prefer to create this cascading property instead of directly injecting AuthenticationStateProvider directly into our components.

CascadingAuthenticationState Component - This component helps to pass the Task<AuthenticationState> cascading property to the child components. So the most preferred way to use this component is in the 'App.razor' file all components must be encapsulated with this CasadingAuthenticationState component, by doing this all components will have access to the user authentication information by using Task<AuthenticationState> property.

AuthorizeRouteView Component - Combines the behavior of 'AuthorizeView' and 'RouteView' components, so that it displays the page matching the specified route but only if the user Authorized to see it.

Create A Blazor WebAssembly Sample App:

Let's understand the Blazor WebAssembly authentication flow by implementing a sample, so let's begin our journey by creating a sample application. While creating a sample don't select any authentication check box provided on template selection(Visual Studio), here we are going to implement authentication from scratch. The IDE's for development can be chosen base on our personal preferences, the most recommended IDE's are Visual Studio 2019 and Visual Studio Code.

Required Packages To Install:

Authentication Package:
Install-Package Microsoft.AspNetCore.Components.WebAssembly.Authentication
Browser LocalStorage Package:
Install-Package Blazored.LocalStorage

CascadingAuthenticationState And AuthrozieRouteView Components:

CascadingAuthenticationState provides Task<AuthenticateState>  cascading property which has information about the user, so all children components can use this cascading property provided by the CascadingAuthenticationState component. The ideal place to configure this CascadingAuthentication state is at App.razor file as the parent of all components of our application which means as root component, so that all components in our application can implement Task<AuthenticateState>

AuthorizeRouteView can validate the user against his roles and claims to access a particular page. In our demo AuthorizeRouteView component configuration is optional, but it is best practice to use it. In the 'App.razor' file, we need to replace the existing 'RouteView' component with the 'AuthorizeRouteView' component.
App.razor:
<CascadingAuthenticationState>
    <Router AppAssembly="@typeof(Program).Assembly">
        <Found Context="routeData">
            <AuthorizeRouteView RouteData="@routeData" DefaultLayout="@typeof(MainLayout)" />
        </Found>
        <NotFound>
            <LayoutView Layout="@typeof(MainLayout)">
                <p>Sorry, there's nothing at this address.</p>
            </LayoutView>
        </NotFound>
    </Router>
</CascadingAuthenticationState>

Custom AuthenticationStateProvider:

The 'Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider' is the main provider in the Blazor application for authentication. So for our authentication flow process, we need to create a custom provider by inheriting the AuthenticationStateProvider as a base class.
Auth/CustomAuthenticationProvider:
using Microsoft.AspNetCore.Components.Authorization;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;

namespace BlazorWasm.JwtAuthLearning.Auth
{
    public class CustomAuthenticationProvider : AuthenticationStateProvider
    {
        public override Task<AuthenticationState> GetAuthenticationStateAsync()
        {
            throw new NotImplementedException();
        }
    }
}
Now register our service in DI(dependency Injection) service.
Program.cs:
builder.Services.AddScoped<AuthenticationStateProvider, CustomAuthenticationProvider>();
builder.Services.AddAuthorizationCore();
  • The 'AddAuthorizationCore()' service enables authentication to our application.

Create Account Services:

To write our logical implementations for login, logout to our application let's create service files as follow.
Services/IAccountService.cs:
using System.Threading.Tasks;

namespace BlazorWasm.JwtAuthLearning.Services
{
    public interface IAccountService
    {
	
    }
}
Services/AccountService.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace BlazorWasm.JwtAuthLearning.Services
{
    public class AccountService : IAccountService
    {

    }
}
Now register our logical services in DI(dependency Injection) service
Program.cs:
builder.Services.AddScoped<IAccountService, AccountService>();

Implement The AuthorizedView Component: 

The AutherizedView component displays different content based on user authentication. Its child components are like 'Authorized'(displays only for authenticated users), 'NotAuthorized'(displays only for non authenticated users).
Pages/Index.razor:(Html Part)
@page "/"
<div>
    <AuthorizeView>
        <Authorized>
            <h1>Your Dashboard - Your Claims</h1>
            <div>
                @foreach (var claim in userClaim)
                {
                    <div>@claim.Type - @claim.Value</div>
                }
            </div>
            <div>
                <button type="button" @onclick="Logout">Logout</button>
            </div>
        </Authorized>
        <NotAuthorized>
            <h1>!Oops you need to be login to view your dashboard</h1>
            <button type="button" @onclick="Login">Login</button>
        </NotAuthorized>
    </AuthorizeView>
</div>
  • The 'AuthorizeView' component contains 'Authorized'(displayed for login users), 'NotAuthorized'(displayed for non login users).
  • In the 'Authorized' component showing all user claims. Add a button to logout the user.
  • In the 'NotAuthorized' component showing a message with a button for login.
Pages/Index.razor:(Code Part)
@code{ 
    [CascadingParameter]
    private Task<AuthenticationState> authenticationState { get; set; }
    private IList<Claim> userClaim { get; set; } = new List<Claim>() { };

    private void Login()
    {

    }

    private void Logout()
    {

    }
}
  • (Line: 3) The 'Task<AuthenticateState>' cascading property was declared.
  • (Line: 4) The collection of  'Claims' property declares to show all the claims to the users on login.
Import the following namespaces in _Import.razor file
_Import.razor:
@using Microsoft.AspNetCore.Authorization
@using Microsoft.AspNetCore.Components.Authorization
@using System.Security.Claims

Mock Claims To Test Authentication:

To understand the 'Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider' provider effects on blazor webassembly authentication, let's add some fake claims to it for testing.
Auth/CustomAuthenticationProvider:
private ClaimsPrincipal claimsPrincipal = new ClaimsPrincipal(new ClaimsIdentity());
public override async Task<AuthenticationState> GetAuthenticationStateAsync()
{
  await Task.FromResult(0);
  return new AuthenticationState(claimsPrincipal);
}
  • The 'AuthenticationStateProvider.GetAuthenticationStateAsync()' method will be to update the users state of the application. 
  • For the 'claimsPrincipal' property we created an empty claims principal(technically non authenticated if no claims) and this property value will be consumed by 'GetAuthenticationStateAsync()' to return the AuthenticationState.
Auth/CustomAuthenticationProvider:
public void LoginNotify()
{
  var identity = new ClaimsIdentity(new[]
  {
    new Claim(ClaimTypes.Name, "Test"),
	new Claim(ClaimTypes.Email, "test@test.com")
  },"Fake Authentication");
  claimsPrincipal = new ClaimsPrincipal(identity);
  NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
}
  • (Line: 1) The 'LoginNotify()' method needs to invoke on the user tries to log in.
  • (Line: 3-7) Adding some collection of fake claims.
  • (Line: 8) Assigning those fake data ClaiPrincipal to the property 'claisPrincipal'(this property will be returned in AuthenticationState by the 'GetAuthenticationStateAsyn()' method).
  • (Line: 9) The 'AuthenticationStateProvider.NotifyAuthenticationStateChanged()' method raise a change event to update AuthenticationState. Here we are resetting the authentication by invoking the 'GetAuthenticationStateAsync'. Since we have created some fake claims now the application state will be changed as authenticated.
Auth/CustomAuthenticationProvider:
public void LogoutNotify()
{
  var anonymous = new ClaimsPrincipal(new ClaimsIdentity());
  claimsPrincipal = anonymous;
  NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
}
  • (Line: 1) The 'LogoutNotify()' method needs to invoke on the user logs out from the application.
  • (Line: 3) Creating empty claims to make the user to logout. 
  • (Line: 4) Assigning those dummy claims to 'cliamsPrincipal' property
  • (Line: 5) Here invoking the 'NotifyAuthenticationStageChanged()' method to reset the authentication state by changing the claims to empty to make the user logout.
Complete authentication provider code looks as below:
Auth/CustomAuthentiationProvider:
public class CustomAuthenticationProvider : AuthenticationStateProvider
{
  private ClaimsPrincipal claimsPrincipal = new ClaimsPrincipal(new ClaimsIdentity());
  public override async Task<AuthenticationState> GetAuthenticationStateAsync()
  {
	await Task.FromResult(0);
	return new AuthenticationState(claimsPrincipal);
  }

  public void LoginNotify()
  {
	var identity = new ClaimsIdentity(new[]
	{
	new Claim(ClaimTypes.Name, "Test"),
	new Claim(ClaimTypes.Email, "test@test.com")
	},"Fake Authentication");
	claimsPrincipal = new ClaimsPrincipal(identity);
	NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
  }

  public void LogoutNotify()
  {
	var anonymous = new ClaimsPrincipal(new ClaimsIdentity());
	claimsPrincipal = anonymous;
	NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
  }
}
Now update the AccountService logic to communicate with the CustomAuthenticationProvider as follow.
Services/IAccountService.cs:
public interface IAccountService
{
  bool Login();
  bool Logout();
}
Services/AccountService.cs:
public class AccountService : IAccountService
{
  private readonly AuthenticationStateProvider _authenticationStateProvider;
  public AccountService(AuthenticationStateProvider authenticationStateProvider)
  {
	_authenticationStateProvider = authenticationStateProvider;
  }
  public bool Login()
  {
	(_authenticationStateProvider as CustomAuthenticationProvider).LoginNotify();
	return true;
  }

  public bool Logout()
  {
	(_authenticationStateProvider as CustomAuthenticationProvider).LogoutNotify();
	return true;
  }
}
  • (Line: 3) The 'Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider' injected into our service.
  • (Line: 10) Invoking 'LoginNotify()' method
  • (Line: 16) Invoking 'LogoutNotify()' method.
Now update our Index.razor component to use our AccountService.
Pages/Index.razor:
@inject IAccountService _accountService;
  • Inject our IAccountService 
Pages/Index.razor:
[CascadingParameter]
private Task<AuthenticationState> authenticationState { get; set; }
private IList<Claim> userClaim
{
  get
  {
   var auth =  authenticationState.Result;
   if (auth.User.Identity.IsAuthenticated)
   {
	return auth.User.Claims.ToList();
   }
   return new List<Claim>();
  }
}
  • The 'Task<AuthenticationState>' cascading property will always change on update in user state. So to receive the latest changes always we called it inside of the claims collection property.
The complete code for the Index.razor as below
Pages/Index.razor:
@page "/"
@inject IAccountService _accountService;
<div>
    <AuthorizeView>
        <Authorized>
            <h1>Your Dashboard - Your Claims</h1>
            <div>
                @foreach (var claim in userClaim)
                {
                    <div>@claim.Type - @claim.Value</div>
                }
            </div>
            <div>
                <button type="button" class="btn btn-primary"  @onclick="Logout">Logout</button>
            </div>
        </Authorized>
        <NotAuthorized>
            <h1>!Oops you need to be login to view your dashboard</h1>
            <button type="button" class="btn btn-primary"  @onclick="Login">Login</button>
        </NotAuthorized>
    </AuthorizeView>
</div>

@code{ 
    [CascadingParameter]
    private Task<AuthenticationState> authenticationState { get; set; }
    private IList<Claim> userClaim
    {
        get
        {
            var auth =  authenticationState.Result;
            if (auth.User.Identity.IsAuthenticated)
            {
                return auth.User.Claims.ToList();
            }
            return new List<Claim>();
        }
    }

    private async Task Login()
    {
        _accountService.Login();
    }

    private void Logout()
    {
        _accountService.Logout();
    }
}
Now import IAccountService namespace in _Import.razor file
_Import.razor:
@using BlazorWasm.JwtAuthLearning.Services
Now we can test our sample page as follows.

Use Test JWT Token To Test Authentication:

In the above step, we have mocked claims data to implement authentication. Now we are going to use a test JWT Token to implement authentication(In later steps we will integrate actual JWT token API, for better understand here we are doing these mocking steps)
JWT Token For Testing:
eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJlbWFpbCI6Im5hdmVlbkBnbWFpbC5jb20iLCJwaG9uZSI6IjEyMzQ1Njc4OTAiLCJleHAiOjE2MDMxOTQ2MTIsImlzcyI6ImxvY2FsaG9zdDo1MDAwIiwiYXVkIjoiQVBJIn0.wRPD4THnUzLhJZhu4eNMx1ztbNAABQ9rkIEJaWBZX_c
On a single page, application tokens are saved in browser local storage. So let's register our LocalStorage service in DI(dependency injection) services.
Program.cs:
builder.Services.AddBlazoredLocalStorage();
The JWT token is an encrypted string that contains user information like claims, so we need to decrypt and read the claims from the JWT token. To read the claims from the JWT token add the following helper class to our application.
Helpers/JwtParser.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Claims;
using System.Text.Json;
using System.Threading.Tasks;

namespace BlazorWasm.JwtAuthLearning.Helpers
{
    public static class JwtParser
    {
        public static IEnumerable<Claim> ParseClaimsFromJwt(string jwt)
        {
            var claims = new List<Claim>();
            var payload = jwt.Split('.')[1];

            var jsonBytes = ParseBase64WithoutPadding(payload);

            var keyValuePairs = JsonSerializer.Deserialize<Dictionary<string, object>>(jsonBytes);

            claims.AddRange(keyValuePairs.Select(kvp => new Claim(kvp.Key, kvp.Value.ToString())));

            return claims;
        }

        private static byte[] ParseBase64WithoutPadding(string base64)
        {
            switch (base64.Length % 4)
            {
                case 2: base64 += "=="; break;
                case 3: base64 += "="; break;
            }
            return Convert.FromBase64String(base64);
        }
    }
}
Now update our CustomAuthenticationProvider to read the claims from the JWT token.
Auth/CustomAuthenticationProvider:
public class CustomAuthenticationProvider : AuthenticationStateProvider
{
  private readonly ILocalStorageService _localStorageService;

  public CustomAuthenticationProvider(ILocalStorageService localStorageService)
  {
   _localStorageService = localStorageService;
  }
  public override async Task<AuthenticationState> GetAuthenticationStateAsync()
  {

   string token = await _localStorageService.GetItemAsync<string>("token");
   if (string.IsNullOrEmpty(token))
   {
	var anonymous = new AuthenticationState(new ClaimsPrincipal(new ClaimsIdentity() { }));
	return anonymous;
   }
   var userClaimPrincipal = new ClaimsPrincipal(new ClaimsIdentity(JwtParser.ParseClaimsFromJwt(token),"Fake Authentication"));
   var loginUser = new AuthenticationState(userClaimPrincipal);
   return loginUser;
  }

  public void Notify()
  {
   NotifyAuthenticationStateChanged(GetAuthenticationStateAsync());
  }
}
  • (Line: 5) The 'Blazored.LocalStorage.ILocalStorageService' injected.
  • (Line: 12) Fetching token stored in browser local storage.
  • (Line: 13-17) If token not found, then we will return the empty claims(means not authenticated).
  • (Line: 18) Using 'JwtParser' helper class for retrieving claims from the token.
  • (Line: 25) The 'NotifyAuthenticationChanged()' to refresh the AuthenticationState.
Now update the logic in our AccountService files as below.
Services/IAccountService.cs:
public interface IAccountService
{
  Task<bool> LoginAsync();
  Task<bool> LogoutAsync();
}
Services/AccountService.cs:
public class AccountService : IAccountService
{
  private readonly AuthenticationStateProvider _customAuthenticationProvider;
  private readonly ILocalStorageService _localStorageService;
  public AccountService(ILocalStorageService localStorageService,
	AuthenticationStateProvider customAuthenticationProvider)
  {
	_localStorageService = localStorageService;
	_customAuthenticationProvider = customAuthenticationProvider;
  }
  public async Task<bool> LoginAsync()
  {
	string token = "copy_Past_Test_Token_in_the_article_above";
	await _localStorageService.SetItemAsync("token", token);
	(_customAuthenticationProvider as CustomAuthenticationProvider).Notify();
	return true;
  }

  public async Task<bool> LogoutAsync()
  {
	await _localStorageService.RemoveItemAsync("token");
	(_customAuthenticationProvider as CustomAuthenticationProvider).Notify();
	return true;
  }
}
  • (Line: 5-6) The 'Blazored.LocalStorage.ILocalStorageService' and 'Microsoft.AspNetCore.Components.Authorization.AuthenticationStateProvider' are injected.
  • (Line: 14) Storing the access token to the browser's local storage.
  • (Line: 15) Refreshing the AuthenticationState after storing the access token, so that AuthenticationStateProvider changes the user state.
  • (Line: 21) On logout remove the access token from the browser local storage.
  • (Line: 22) After removing the access token, refreshing the AuthenticationState.
Now update the code changes in Index.razor file as below.
Pages/Index.razor:
private async Task Login()
{
  await _accountService.LoginAsync();
}

private async void Logout()
{
  await _accountService.LogoutAsync();
}
Now test authentication flow on our page.

Integrate JWT Authentication API:

The final step of our authentication is to configure the JWT authentication endpoint. Click here to follow the steps to develop JWT Authentication. Here in our demo, I'm integrating my local JWT authentication endpoint.

Now let's create 2 model classes like LoginModel(used in the form) and AuthResponse(captures token response).
Models/LoginModel.cs:
public class LoginModel
{
  public string Email { get; set; }
  public string Password { get; set; }
}
Models/AuthResponse.cs:
public class AuthResponse
{
  public string Token { get; set; }
  public string RefreshToken { get; set; }
}
Update the 'LoginAsync' concrete method in IAccountService.
Services/IAccountService.cs:
Task<bool> LoginAsync(LoginModel model);
Update the AccountService to inject the HttpClient.
Services/AccountService.cs:
private readonly AuthenticationStateProvider _customAuthenticationProvider;
private readonly ILocalStorageService _localStorageService;
private readonly HttpClient _httpClient;
public AccountService(ILocalStorageService localStorageService,
	AuthenticationStateProvider customAuthenticationProvider,
	HttpClient httpClient)
{
  _localStorageService = localStorageService;
  _customAuthenticationProvider = customAuthenticationProvider;
  _httpClient = httpClient;
}
Update the 'LoginAsync' method implementation in AccountService.
Services/AccountService:
public async Task<bool> LoginAsync(LoginModel model)
{
  var response = await _httpClient.PostAsJsonAsync<LoginModel>("/account/login-token", model);
  if (!response.IsSuccessStatusCode)
  {
	return false;
  }
  AuthResponse authData = await response.Content.ReadFromJsonAsync<AuthResponse>();
  await _localStorageService.SetItemAsync("token", authData.Token);
  (_customAuthenticationProvider as CustomAuthenticationProvider).Notify();
  return true;
}
  • Integrated JWT authentication API to fetch the user login token
Now add the domain of JWT authentication API in Program file to the HttpClient object.
Program.cs:
builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri("https://localhost:5001/") });
Now add LoginModel property in Index.razor and also update the AccountService method invocation.
Index.razor:(Update Code Part)
@code{ 
    private LoginModel model = new LoginModel();

    private async Task Login()
    {
        await _accountService.LoginAsync(model);
    }
	// code hidden for display purpose
}
Now update NonAuthorized component Html with a login form as below
Index.razor:(Update Html Part)
<NotAuthorized>
	<h1>!Oops you need to be login to view your dashboard</h1>
	<div>
		<div class="form-group">
			<label for="inputEmail">Email Address</label>
			<input type="email" class="form-control" id="inputEmail" @bind="@model.Email" />
		</div>
		<div class="form-group">
			<label for="inputPassword">Password</label>
			<input type="password" class="form-control" id="inputPassword" @bind="@model.Password" />
		</div>
		<button type="button" class="btn btn-primary" @onclick="Login">Login</button>
	</div>
</NotAuthorized>
Now run the application and test the login form as below.


That's all about the Blazor WebAssembly JWT authentication from the scratch. In the next article, we will implement the integration of the RefreshToken functionality.

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Wrapping Up:

Hopefully, I think this article delivered some useful information on the authentication implementation from scratch in the Blazor WebAssembly application. I love to have your feedback, suggestions, and better techniques in the comment section below.

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Comments

  1. You saved me a lot of time! Thank you!

    ReplyDelete
  2. When installing packages, perhaps you should say if its in the Server or the Client application??? Currently its not clear at all!!

    ReplyDelete
    Replies
    1. Hi everything client only. In this article I didnt explained any server side code

      Delete
  3. there is some error in this method: ParseBase64WithoutPadding
    because base64 string must replace like this:

    base64 = base64.Replace('-', '+').Replace('_', '/');
    and then switch (base64.Length % 4)

    ReplyDelete
  4. Really unfortunate that you don't show in this article or provide in the github repo, the CascadingAuthenticationState Component. You mention it briefly but never show how it works or provide it in the github repo, so this makes the tutorial incomplete.

    ReplyDelete

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Introduction: Form validations in any applications are like assures that a valid data is storing on servers. All programing frameworks have their own individual implementations for form validations. In Dotnet Core MVC application server-side validations carried on by the models with the help of Data Annotations and the client-side validations carried by the plugin jQuery Unobtrusive Validation. jQuery Unobtrusive Validation is a custom library developed by Microsoft based on the popular library  jQuery Validate . In this article, we are going to learn how the model validation and client-side validation works in Asp.Net Core MVC Application with sample examples. Getting Started: Let's create an Asp.Net Core MVC application project using preferred editors like Microsoft Visual Studio or Microsoft Visual Studio Code. Here I'm using Visual Studio. Let's create an MVC controller and name it as 'PersonController.cs' and add an action method as bel

NestJS File Upload

In this article, we are going to understand the steps to create a file uploading endpoint in the NestJS application. Key Features In NestJS File Upload: Let us know some key features of NestJS file upload before implementing a sample application. FileInterceptor: The 'FileInterceptor' will be decorated on top of the file upload endpoint. This interceptor will read single file data from the form posted to the endpoint. export declare function FilesInterceptor(fieldName: string, localOptions?: MulterOptions): Type<NestInterceptor>; Here we can observe the 'fieldName' first input parameter this value should be a match with our 'name' attribute value on the form file input field. So our interceptor read our files that are attached to the file input field. Another input parameter of 'MulterOptions' that provides configuration like file destination path, customizing file name, etc. FilesInterceptor: The 'FilesInterceptor' will be decorated on t