How do you secure a SignalR chat application to allow only authenticated users to chat.

Question

Ravi Vishwakarma · Answer

To secure a SignalR chat application so that only authenticated users can send and receive messages, follow these steps:
Step 1: Enable Authentication in Your ASP.NET Core App
Configure authentication (e.g., cookies, JWT bearer tokens, or
ASP.NET Identity) in Startup.cs or Program.cs.
Example with cookie authentication:
public void ConfigureServices(IServiceCollection services)
{
    services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
            .AddCookie();
    services.AddAuthorization();
    services.AddSignalR();
}
And in the middleware pipeline:
public void Configure(IApplicationBuilder app)
{
    app.UseRouting();
    app.UseAuthentication();
    app.UseAuthorization();
    app.UseEndpoints(endpoints =andgt;
    {
        endpoints.MapHubandlt;ChatHubandgt;("/chatHub").RequireAuthorization();
        // Only authenticated users can connect to /chatHub
    });
}
Step 2: Restrict Access to the Hub
Apply the [Authorize] attribute on your hub class:
using Microsoft.AspNetCore.Authorization;
[Authorize]
public class ChatHub : Hub
{
    public async Task SendMessage(string message)
    {
        var user = Context.User.Identity.Name;
        await Clients.All.SendAsync("ReceiveMessage", user, message);
    }
}
This ensures only authenticated users can invoke methods or receive messages.
Step 3: Set the User Identifier
By default, SignalR uses User.Identity.Name as the user identifier. If you need a custom value (e.g., user ID from claims):
public class CustomUserIdProvider : IUserIdProvider
{
    public string GetUserId(HubConnectionContext connection)
    {
        return connection.User?.FindFirst("sub")?.Value;
    }
}
Register it in Startup.cs:
services.AddSingletonandlt;IUserIdProvider, CustomUserIdProviderandgt;();
Step 4: Secure the Client-Side Connection
When using cookies, authentication is handled automatically in the browser. For
JWT, pass the token explicitly:
const connection = new signalR.HubConnectionBuilder()
    .withUrl("/chatHub", {
        accessTokenFactory: () =andgt; getJwtToken()
    })
    .build();
Step 5: Handle Unauthorized Access
When a client is unauthenticated:The connection will be rejected by RequireAuthorization().
You can handle the error on the client:
connection.start().catch(err =andgt; {
    console.error("Connection failed:", err.toString());
});
Summary
Part
Description
UseAuthentication()
Enables authentication middleware
UseAuthorization()
Enables authorization checks
[Authorize] on Hub
Restricts access to authenticated users only
Custom IUserIdProvider
Optionally use a custom ID (e.g., User ID claim)
JWT/Cookie handling
Depends on whether your app is SPA or MVC

interview

How do you secure a SignalR chat application to allow only authenticated users to chat.

Ravi Vishwakarma

Can you answer this question?

1 Answers

Step 1: Enable Authentication in Your ASP.NET Core App

Step 2: Restrict Access to the Hub

Step 3: Set the User Identifier

Step 4: Secure the Client-Side Connection

Step 5: Handle Unauthorized Access

Summary

Liked By

Part	Description
`UseAuthentication()`	Enables authentication middleware
`UseAuthorization()`	Enables authorization checks
`[Authorize]` on Hub	Restricts access to authenticated users only
Custom `IUserIdProvider`	Optionally use a custom ID (e.g., User ID claim)
JWT/Cookie handling	Depends on whether your app is SPA or MVC