Modded Handshake support (#551)

* fix paths for new starlight update

* fix folder

* modded handshake (needs test)

Main.cs

@@ -40,7 +40,7 @@ public class Main : BasePlugin
 {
     private const string DebugKeyHash = "c0fd562955ba56af3ae20d7ec9e64c664f0facecef4b3e366e109306adeae29d";
     private const string DebugKeySalt = "59687b";
-    private const string PluginGuid = "com.gurge44.endlesshostroles";
+    public const string PluginGuid = "com.gurge44.endlesshostroles";
     public const string PluginVersion = "7.4.0";
     public const string PluginDisplayVersion = "7.4.0";
     public const bool TestBuild = false;

Patches/HandshakePatch.cs

@@ -0,0 +1,100 @@
+using System;
+using HarmonyLib;
+using Hazel;
+using Il2CppInterop.Runtime.InteropTypes.Arrays;
+using InnerNet;
+
+namespace EHR.Patches;
+
+// This is taken from Reactor modded handshake.
+// We do not want to pull in Reactor as a dependency though.
+
+/// <summary>
+/// Represents flags of the mod.
+/// </summary>
+[Flags]
+public enum ModFlags : ushort
+{
+    /// <summary>
+    /// No flags.
+    /// </summary>
+    None = 0,
+
+    /// <summary>
+    /// Requires all clients in a lobby to have the mod.
+    /// </summary>
+    RequireOnAllClients = 1 << 0,
+
+    /// <summary>
+    /// Requires the server to have a plugin that handles the mod.
+    /// </summary>
+    RequireOnServer = 1 << 1,
+
+    /// <summary>
+    /// Requires the host of the lobby to have the mod.
+    /// </summary>
+    RequireOnHost = 1 << 2,
+
+    /// <summary>
+    /// Notifies the game server that the host has authority over game logic.
+    /// </summary>
+    DisableServerAuthority = 1 << 3,
+}
+
+
+/// <summary>
+///     Version of the Reactor.Networking protocol format.
+/// </summary>
+public enum ReactorProtocolVersion : byte
+{
+    /// <summary>
+    ///     First public Reactor Protocol version.
+    /// </summary>
+    V2 = 1,
+
+    /// <summary>
+    ///     Version introducing vanilla server support, syncer concept and registries.
+    /// </summary>
+    V3 = 2,
+
+    /// <summary>
+    ///     Latest version.
+    /// </summary>
+    Latest = V3,
+}
+
+[HarmonyPatch(typeof(InnerNetClient), nameof(InnerNetClient.GetConnectionData))]
+public static class HandshakePatch
+{
+    private const ulong MAGIC = 0x72656163746f72; // "reactor" in ascii, 7 bytes
+
+    public static void Prefix(ref bool useDtlsLayout)
+    {
+        // Due to reasons currently unknown, the useDtlsLayout parameter sometimes doesn't reflect whether DTLS
+        // is actually supposed to be enabled. This causes a bad handshake message and a quick disconnect.
+        // The field on AmongUsClient appears to be more reliable, so override this parameter with what it is supposed to be.
+        useDtlsLayout = AmongUsClient.Instance.useDtls;
+    }
+
+    public static void Postfix(ref Il2CppStructArray<byte> __result)
+    {
+        var handshake = new MessageWriter(1000);
+
+        // Original data
+        handshake.Write(__result);
+
+        // Reactor Header
+        var version = (byte) ReactorProtocolVersion.Latest;
+        var value = (MAGIC << 8) | version;
+        handshake.Write(value);
+
+        // ModdedHandshakeC2S
+        handshake.WritePacked(1);
+        handshake.Write(Main.PluginGuid);
+        handshake.Write(Main.PluginVersion);
+        handshake.Write((ushort) (ModFlags.RequireOnHost | ModFlags.RequireOnAllClients));
+
+        __result = handshake.ToByteArray(true);
+        handshake.Recycle();
+    }
+}