Review

Robust.Client/ClientIoC.cs

@@ -159,7 +159,7 @@ public static void RegisterIoC(GameController.DisplayMode mode, IDependencyColle
 
             deps.Register<IXamlProxyHelper, XamlProxyHelper>();
             deps.Register<MarkupTagManager>();
-            deps.Register<IHWId, BasicHWid>();
+            deps.Register<IHWId, BasicHWId>();
         }
     }
 }

Robust.Client/HWId/BasicHWId.cs

@@ -0,0 +1,86 @@
+using System;
+using System.IO;
+using System.Security.Cryptography;
+using Microsoft.Win32;
+using Robust.Client.Utility;
+using Robust.Shared.IoC;
+using Robust.Shared.Network;
+
+namespace Robust.Client.HWId;
+
+internal sealed class BasicHWId : IHWId
+{
+    [Dependency] private readonly IGameControllerInternal _gameController = default!;
+
+    public const int LengthHwid = 32;
+
+    public byte[] GetLegacy()
+    {
+        if (OperatingSystem.IsWindows())
+            return GetWindowsHWid("Hwid");
+
+        return [];
+    }
+
+    public byte[] GetModern()
+    {
+        byte[] raw;
+
+        if (OperatingSystem.IsWindows())
+            raw = GetWindowsHWid("Hwid2");
+        else
+            raw = GetFileHWid();
+
+        return [0, ..raw];
+    }
+
+    private static byte[] GetWindowsHWid(string keyName)
+    {
+        const string keyPath = @"HKEY_CURRENT_USER\SOFTWARE\Space Wizards\Robust";
+
+        var regKey = Registry.GetValue(keyPath, keyName, null);
+        if (regKey is byte[] { Length: LengthHwid } bytes)
+            return bytes;
+
+        var newId = new byte[LengthHwid];
+        RandomNumberGenerator.Fill(newId);
+        Registry.SetValue(
+            keyPath,
+            keyName,
+            newId,
+            RegistryValueKind.Binary);
+
+        return newId;
+    }
+
+    private byte[] GetFileHWid()
+    {
+        var path = UserDataDir.GetRootUserDataDir(_gameController);
+        var hwidPath = Path.Combine(path, ".hwid");
+
+        var value = ReadHWidFile(hwidPath);
+        if (value != null)
+            return value;
+
+        value = RandomNumberGenerator.GetBytes(LengthHwid);
+        File.WriteAllBytes(hwidPath, value);
+
+        return value;
+    }
+
+    private static byte[]? ReadHWidFile(string path)
+    {
+        try
+        {
+            var value = File.ReadAllBytes(path);
+            if (value.Length == LengthHwid)
+                return value;
+        }
+        catch (FileNotFoundException)
+        {
+            // First time the file won't exist.
+        }
+
+        return null;
+    }
+}

Robust.Server/ServerIoC.cs

@@ -97,7 +97,7 @@ internal static void RegisterIoC(IDependencyCollection deps)
             deps.Register<NetworkResourceManager>();
             deps.Register<IHttpClientHolder, HttpClientHolder>();
             deps.Register<UploadedContentManager>();
-            deps.Register<IHWId, DummyHWid>();
+             deps.Register<IHWId, DummyHWId>();
         }
     }
 }

Robust.Shared/CVars.cs

@@ -402,7 +402,7 @@ protected CVars()
         /// Note that modern HWIDs are only available if the connection is authenticated.
         /// </para>
         /// </remarks>
-        public static readonly CVarDef<bool> NetHwid =
+        public static readonly CVarDef<bool> NetHWId =
             CVarDef.Create("net.hwid", true, CVar.SERVERONLY);
 
 

Robust.Shared/Network/IHWId.cs

@@ -36,7 +36,7 @@ internal interface IHWId
 /// <summary>
 /// Implementation of <see cref="IHWId"/> that does nothing, always returning an empty result.
 /// </summary>
-internal sealed class DummyHWid : IHWId
+internal sealed class DummyHWId : IHWId
 {
     public byte[] GetLegacy()
     {

Robust.Shared/Network/NetManager.ServerAuth.cs

@@ -80,7 +80,7 @@ private async void HandleHandshake(NetPeerData peer, NetConnection connection)
 
                     var verifyToken = new byte[4];
                     RandomNumberGenerator.Fill(verifyToken);
-                    var wantHwid = _config.GetCVar(CVars.NetHwid);
+                    var wantHwid = _config.GetCVar(CVars.NetHWId);
                     var msgEncReq = new MsgEncryptionRequest
                     {
                         PublicKey = needPk ? CryptoPublicKey : Array.Empty<byte>(),

Robust.UnitTesting/Server/RobustServerSimulation.cs

@@ -199,7 +199,7 @@ public ISimulation InitializeInstance()
             container.RegisterInstance<ITaskManager>(new Mock<ITaskManager>().Object);
             container.Register<HttpClientHolder>();
             container.Register<IHttpClientHolder, HttpClientHolder>();
-            container.Register<IHWId, DummyHWid>();
+            container.Register<IHWId, DummyHWId>();
 
             var realReflection = new ServerReflectionManager();
             realReflection.LoadAssemblies(new List<Assembly>(2)

Robust.UnitTesting/Shared/GameObjects/EntityState_Tests.cs

@@ -36,7 +36,7 @@ public void ComponentChangedSerialized()
             container.Register<IConfigurationManager, ServerNetConfigurationManager>();
             container.Register<IConfigurationManagerInternal, ServerNetConfigurationManager>();
             container.Register<INetManager, NetManager>();
-            container.Register<IHWId, DummyHWid>();
+            container.Register<IHWId, DummyHWId>();
             container.Register<IReflectionManager, ServerReflectionManager>();
             container.Register<IRobustSerializer, ServerRobustSerializer>();
             container.Register<IRobustMappedStringSerializer, RobustMappedStringSerializer>();