forbid Tor exit nodes to request private servers (#14)

WebInterface/Controllers/PrivateController.cs

@@ -13,16 +13,19 @@ namespace WebInterface.Controllers
     {
         private readonly IPrivateServerService _privateServerService;
         private readonly IRateLimiterService _rateLimiterService;
+        private readonly ITorCheckService _torCheckService;
         private readonly ICustomMapService _customMapService;
         private readonly ILogger<PrivateController> _logger;
 
         public PrivateController(IPrivateServerService privateServerService,
             IRateLimiterService rateLimiterService,
+            ITorCheckService torCheckService,
             ICustomMapService customMapService,
             ILogger<PrivateController> logger)
         {
             _privateServerService = privateServerService;
             _rateLimiterService = rateLimiterService;
+            _torCheckService = torCheckService;
             _customMapService = customMapService;
             _logger = logger;
         }
@@ -51,6 +54,9 @@ namespace WebInterface.Controllers
                 if (!ModelState.IsValid)
                     throw new WebInterfaceException("Something went off the rails.");
 
+                if (_torCheckService.IsTorExit(HttpContext.Connection.RemoteIpAddress))
+                    throw new WebInterfaceException("Requesting private servers through Tor is not allowed.");
+
                 if (!_rateLimiterService.IsRequestAllowed(HttpContext.Connection.RemoteIpAddress))
                     throw new WebInterfaceException("Sorry, you have requested too many servers recently, you need to wait some time.");
 

WebInterface/Services/ITorCheckService.cs

@@ -0,0 +1,13 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Threading.Tasks;
+
+namespace WebInterface.Services
+{
+    public interface ITorCheckService
+    {
+        bool IsTorExit(IPAddress address);
+    }
+}

WebInterface/Services/TorCheckService.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Net;
+using System.Threading.Tasks;
+
+namespace WebInterface.Services
+{
+    public class TorCheckService : ITorCheckService
+    {
+        private const string torExitNodesListUrl = "https://check.torproject.org/exit-addresses";
+
+        private static DateTime lastListUpdate = DateTime.MinValue;
+        private static DateTime lastUpdateFail = DateTime.MinValue;
+        private static string list = string.Empty;
+
+        public bool IsTorExit(IPAddress address)
+        {
+            if (!IsListActual())
+                UpdateList();
+
+            bool isInList = IsInList(address);
+            return isInList;
+        }
+
+        private bool IsListActual()
+        {
+            return !(string.IsNullOrWhiteSpace(list) || DateTime.UtcNow - lastListUpdate > TimeSpan.FromDays(1));
+        }
+
+        private void UpdateList()
+        {
+            if (DateTime.UtcNow - lastUpdateFail > TimeSpan.FromMinutes(30))
+            {
+                WebClient webClient = new WebClient();
+                var listTask = webClient.DownloadStringTaskAsync(new Uri(torExitNodesListUrl));
+                if (listTask.Wait(TimeSpan.FromSeconds(2)))
+                {
+                    list = listTask.Result;
+                    lastListUpdate = DateTime.UtcNow;
+                }
+                else
+                {
+                    lastUpdateFail = DateTime.UtcNow;
+                }
+            }
+        }
+
+        private bool IsInList(IPAddress address)
+        {
+            return list.Contains(address.ToString());
+        }
+    }
+}

WebInterface/Startup.cs

@@ -45,6 +45,7 @@ namespace WebInterface
             services.Add(new ServiceDescriptor(typeof(IStateService), typeof(StateService), ServiceLifetime.Singleton));
             services.Add(new ServiceDescriptor(typeof(IPrivateServerService), typeof(PrivateServerService), ServiceLifetime.Transient));
             services.Add(new ServiceDescriptor(typeof(IRateLimiterService), typeof(RateLimiterService), ServiceLifetime.Singleton));
+            services.Add(new ServiceDescriptor(typeof(ITorCheckService), typeof(TorCheckService), ServiceLifetime.Singleton));
             services.Add(new ServiceDescriptor(typeof(ICustomMapService), typeof(CustomMapService), ServiceLifetime.Transient));
 
             services.Configure<FormOptions>(options =>