The Problem with Token Expiration

Oct 13, 2025 by wbrum.org 130 views

What is the Best Practice to Manually Refresh Auth Tokens in Blazor WebAssembly with Auth0

When building a Blazor WebAssembly application with Auth0 for authentication, it's essential to understand how to manually refresh auth tokens to ensure seamless user experience and prevent token expiration errors. In this article, we'll explore the best practices for refreshing auth tokens in a Blazor WebAssembly application using Auth0.

Before diving into the best practices for refreshing auth tokens, let's understand what auth tokens are and how they work. Auth tokens, also known as access tokens, are short-lived tokens issued by an authentication server (in this case, Auth0) after a user successfully authenticates. These tokens contain the user's identity information and are used to authenticate requests to protected APIs.

The Problem with Token Expiration

Auth tokens have a limited lifespan, typically ranging from 15 minutes to several hours. When a token expires, the application will no longer be able to authenticate requests, resulting in a 401 Unauthorized error. To mitigate this issue, we need to refresh the auth token before it expires.

CustomAuthorizationMessageHandler

In a Blazor WebAssembly application, we can use the CustomAuthorizationMessageHandler to handle authentication and token refresh. This handler is responsible for sending the auth token with each request and refreshing the token when it expires.

Refreshing Auth Tokens

So, how do we manually refresh auth tokens in a Blazor WebAssembly application with Auth0? Here are the best practices:

1. Use the Refresh Token

When a user authenticates, Auth0 issues a refresh token, which can be used to obtain a new access token when the current one expires. We should store the refresh token securely and use it to refresh the auth token when necessary.

2. Implement Token Refresh in the CustomAuthorizationMessageHandler

We can implement token refresh in the CustomAuthorizationMessageHandler by using the refresh token to obtain a new access token. Here's an example:

public class CustomAuthorizationMessageHandler : AuthorizationMessageHandler
{
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IAuth0Service _auth0Service;
public CustomAuthorizationMessageHandler(IHttpClientFactory httpClientFactory, IAuth0Service auth0Service)
{
    _httpClientFactory = httpClientFactory;
    _auth0Service = auth0Service;
}

protected override async Task&lt;HttpResponseMessage&gt; SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
    // Send the request with the auth token
    request.Headers.Authorization = new AuthenticationHeaderValue(&quot;Bearer&quot;, await _auth0Service.GetAccessTokenAsync());

    // Check if the token has expired
    if (await _auth0Service.IsTokenExpiredAsync())
    {
        // Refresh the token using the refresh token
        await _auth0Service.RefreshTokenAsync();
    }

    return await base.SendAsync(request, cancellationToken);
}

}

3. Handle Token Refresh Errors

When refreshing the token, we should handle any errors that may occur. We can use a retry mechanism to attempt token refresh multiple times before failing.

4. Store the Refresh Token Securely

We should store the refresh token securely using a secure storage mechanism, such as the IOptions<T> pattern or a secure storage library.

5. Monitor Token Expiration

We should monitor token expiration and refresh the token before it expires to prevent token expiration errors.

Example Use Case

Here's an example use case for refreshing auth tokens in a Blazor WebAssembly application with Auth0:

@page "/"
@using Microsoft.AspNetCore.Components.WebAssembly.Authentication
@inject IAuth0Service _auth0Service
@code {
protected override async Task OnInitializedAsync()
{
// Get the auth token
var token = await _auth0Service.GetAccessTokenAsync();
    // Check if the token has expired
    if (await _auth0Service.IsTokenExpiredAsync())
    {
        // Refresh the token using the refresh token
        await _auth0Service.RefreshTokenAsync();
    }
}

}

In conclusion, manually refreshing auth tokens in a Blazor WebAssembly application with Auth0 requires a combination of understanding how auth tokens work, implementing token refresh in the CustomAuthorizationMessageHandler, handling token refresh errors, storing the refresh token securely, and monitoring token expiration. By following these best practices, we can ensure seamless user experience and prevent token expiration errors in our Blazor WebAssembly application.

Q: How do I implement token refresh in my Blazor WebAssembly application? A: You can implement token refresh in the CustomAuthorizationMessageHandler by using the refresh token to obtain a new access token.
Q: What happens if the token refresh fails? A: You should handle token refresh errors and use a retry mechanism to attempt token refresh multiple times before failing.
Q: How do I store the refresh token securely? A: You can store the refresh token securely using a secure storage mechanism, such as the IOptions<T> pattern or a secure storage library.
Frequently Asked Questions (FAQs) about Manually Refreshing Auth Tokens in Blazor WebAssembly with Auth0

A: The purpose of manually refreshing auth tokens is to ensure seamless user experience and prevent token expiration errors. When a user authenticates, Auth0 issues a short-lived access token that expires after a certain period. If the token expires before the user completes their session, the application will no longer be able to authenticate requests, resulting in a 401 Unauthorized error. By manually refreshing the auth token, we can prevent this issue and ensure that the user remains authenticated throughout their session.

A: You can implement token refresh in the CustomAuthorizationMessageHandler by using the refresh token to obtain a new access token. Here's an example:

public class CustomAuthorizationMessageHandler : AuthorizationMessageHandler
{
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IAuth0Service _auth0Service;
public CustomAuthorizationMessageHandler(IHttpClientFactory httpClientFactory, IAuth0Service auth0Service)
{
    _httpClientFactory = httpClientFactory;
    _auth0Service = auth0Service;
}

protected override async Task&lt;HttpResponseMessage&gt; SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
    // Send the request with the auth token
    request.Headers.Authorization = new AuthenticationHeaderValue(&quot;Bearer&quot;, await _auth0Service.GetAccessTokenAsync());

    // Check if the token has expired
    if (await _auth0Service.IsTokenExpiredAsync())
    {
        // Refresh the token using the refresh token
        await _auth0Service.RefreshTokenAsync();
    }

    return await base.SendAsync(request, cancellationToken);
}

}

A: If the token refresh fails, you should handle the error and use a retry mechanism to attempt token refresh multiple times before failing. You can also implement a fallback strategy to handle cases where token refresh is not possible.

A: You can store the refresh token securely using a secure storage mechanism, such as the IOptions<T> pattern or a secure storage library. Make sure to use a secure storage mechanism that is designed to protect sensitive data.

A: Yes, you can use a different authentication provider instead of Auth0. However, you will need to modify the CustomAuthorizationMessageHandler to work with the new authentication provider.

A: You can monitor token expiration by checking the token's expiration date and time. You can use a timer or a scheduling mechanism to check the token's expiration date and time at regular intervals.

A: Yes, you can use a different storage mechanism instead of the IOptions<T> pattern. However, make sure to use a secure storage mechanism that is designed to protect sensitive data.

A: You can handle cases where the user is not authenticated by checking the authentication status of the user. If the user is not authenticated, you can redirect the user to the login page or display an error message.

A: Yes, you can use a different authentication flow instead of the default authentication flow. However, you will need to modify the CustomAuthorizationMessageHandler to work with the new authentication flow.

A: You can troubleshoot issues with token refresh by checking the logs, using a debugger, or implementing a logging mechanism to track token refresh attempts. You can also use a tool like Fiddler or Postman to inspect the token refresh requests and responses.

In conclusion, manually refreshing auth tokens in a Blazor WebAssembly application with Auth0 requires a combination of understanding how auth tokens work, implementing token refresh in the CustomAuthorizationMessageHandler, handling token refresh errors, storing the refresh token securely, and monitoring token expiration. By following these best practices, you can ensure seamless user experience and prevent token expiration errors in your Blazor WebAssembly application.