Creating a proxy to another web api with Asp.net core

Question

I\'m developing an ASP.Net Core web application where I need to create a kind of \"authentication proxy\" to another (external) web service.

What I mean by authentic

Answer 1

Here is a basic implementation of Proxy library for ASP.NET Core:

This does not implement the authorization but could be useful to someone looking for a simple reverse proxy with ASP.NET Core. We only use this for development stages.

using System;
using System.Globalization;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Primitives;

namespace Sample.Proxy
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddLogging(options =>
            {
                options.AddDebug();
                options.AddConsole(console =>
                {
                    console.IncludeScopes = true;
                });
            });

            services.AddProxy(options =>
            {
                options.MessageHandler = new HttpClientHandler
                {
                    AllowAutoRedirect = false,
                    UseCookies = true 
                };

                options.PrepareRequest = (originalRequest, message) =>
                {
                    var host = GetHeaderValue(originalRequest, "X-Forwarded-Host") ?? originalRequest.Host.Host;
                    var port = GetHeaderValue(originalRequest, "X-Forwarded-Port") ?? originalRequest.Host.Port.Value.ToString(CultureInfo.InvariantCulture);
                    var prefix = GetHeaderValue(originalRequest, "X-Forwarded-Prefix") ?? originalRequest.PathBase;

                    message.Headers.Add("X-Forwarded-Host", host);
                    if (!string.IsNullOrWhiteSpace(port)) message.Headers.Add("X-Forwarded-Port", port);
                    if (!string.IsNullOrWhiteSpace(prefix)) message.Headers.Add("X-Forwarded-Prefix", prefix);

                    return Task.FromResult(0);
                };
            });
        }

        private static string GetHeaderValue(HttpRequest request, string headerName)
        {
            return request.Headers.TryGetValue(headerName, out StringValues list) ? list.FirstOrDefault() : null;
        }

        public void Configure(IApplicationBuilder app)
        {
            app.UseWebSockets()
                .Map("/api", api => api.RunProxy(new Uri("http://localhost:8833")))
                .Map("/image", api => api.RunProxy(new Uri("http://localhost:8844")))
                .Map("/admin", api => api.RunProxy(new Uri("http://localhost:8822")))
                .RunProxy(new Uri("http://localhost:8811"));
        }

        public static void Main(string[] args)
        {
            var host = new WebHostBuilder()
                .UseKestrel()
                .UseIISIntegration()
                .UseStartup()
                .Build();

            host.Run();
        }
    }
}