supporting .net core auth in signalr hubs

SignalRHubsAuthExtentions.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Options;

namespace SignalRWebApp
{
    public static class SignalRHubsAuthExtentions
    {
        // Use one of the extentions to add hubs authentication support. See https://docs.microsoft.com/en-us/aspnet/core/signalr/authn-and-authz?view=aspnetcore-5.0#bearer-token-authentication for more details.

        public static void AddHubsAuthentication(this JwtBearerOptions options)
        {
            // We have to hook the OnMessageReceived event in order to
            // allow the JWT authentication handler to read the access
            // token from the query string when a WebSocket or 
            // Server-Sent Events request comes in.

            // Sending the access token in the query string is required due to
            // a limitation in Browser APIs. We restrict it to only calls to the
            // SignalR hub in this code.
            // See https://docs.microsoft.com/aspnet/core/signalr/security#access-token-logging
            // for more information about security considerations when using
            // the query string to transmit the access token.
            if (options.Events == null)
            {
                options.Events = new JwtBearerEvents();
            }
            var originalOnMessageReceived = options.Events.OnMessageReceived;
            options.Events.OnMessageReceived = async context =>
            {
                await originalOnMessageReceived?.Invoke(context);

                if (string.IsNullOrEmpty(context.Token))
                {
                    var accessToken = context.Request.Query["access_token"];
                    var path = context.HttpContext.Request.Path;

                    if (!string.IsNullOrEmpty(accessToken) &&
                        path.StartsWithSegments("/hubs"))
                    {
                        context.Token = accessToken;
                    }
                }
            };
        }

        /// <summary>
        /// Use this after adding services for authentication (AddAuthentication) and the authentication handler for Identity Server (AddIdentityServerJwt).
        /// </summary>
        public static void AddHubsAuthentication(this IServiceCollection services)
        {
            services.TryAddEnumerable(
                ServiceDescriptor.Singleton<IPostConfigureOptions<JwtBearerOptions>, ConfigureJwtBearerOptionsToSupportHubsAuthentication>());
        }

        private class ConfigureJwtBearerOptionsToSupportHubsAuthentication : IPostConfigureOptions<JwtBearerOptions>
        {
            public void PostConfigure(string name, JwtBearerOptions options)
            {
                options.AddHubsAuthentication();
            }
        }
    }
}