Add system to kick people if they connect to multiple servers at once. (#34563)

Content.Server/Administration/Managers/MultiServerKickManager.cs

@@ -0,0 +1,114 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Content.Server.Database;
+using Content.Shared.CCVar;
+using Robust.Server.Player;
+using Robust.Shared.Asynchronous;
+using Robust.Shared.Configuration;
+using Robust.Shared.Enums;
+using Robust.Shared.Network;
+using Robust.Shared.Player;
+
+namespace Content.Server.Administration.Managers;
+
+/// <summary>
+/// Handles kicking people that connect to multiple servers on the same DB at once.
+/// </summary>
+/// <seealso cref="CCVars.AdminAllowMultiServerPlay"/>
+public sealed class MultiServerKickManager
+{
+    public const string NotificationChannel = "multi_server_kick";
+
+    [Dependency] private readonly IPlayerManager _playerManager = null!;
+    [Dependency] private readonly IServerDbManager _dbManager = null!;
+    [Dependency] private readonly ILogManager _logManager = null!;
+    [Dependency] private readonly IConfigurationManager _cfg = null!;
+    [Dependency] private readonly IAdminManager _adminManager = null!;
+    [Dependency] private readonly ITaskManager _taskManager = null!;
+    [Dependency] private readonly IServerNetManager _netManager = null!;
+    [Dependency] private readonly ILocalizationManager _loc = null!;
+    [Dependency] private readonly ServerDbEntryManager _serverDbEntry = null!;
+
+    private ISawmill _sawmill = null!;
+    private bool _allowed;
+
+    public void Initialize()
+    {
+        _sawmill = _logManager.GetSawmill("multi_server_kick");
+
+        _playerManager.PlayerStatusChanged += OnPlayerStatusChanged;
+        _cfg.OnValueChanged(CCVars.AdminAllowMultiServerPlay, b => _allowed = b, true);
+
+        _dbManager.SubscribeToJsonNotification<NotificationData>(
+            _taskManager,
+            _sawmill,
+            NotificationChannel,
+            OnNotification,
+            OnNotificationEarlyFilter
+        );
+    }
+
+    // ReSharper disable once AsyncVoidMethod
+    private async void OnPlayerStatusChanged(object? sender, SessionStatusEventArgs e)
+    {
+        if (_allowed)
+            return;
+
+        if (e.NewStatus != SessionStatus.InGame)
+            return;
+
+        // Send notification to other servers so they can kick this player that just connected.
+        try
+        {
+            await _dbManager.SendNotification(new DatabaseNotification
+            {
+                Channel = NotificationChannel,
+                Payload = JsonSerializer.Serialize(new NotificationData
+                {
+                    PlayerId = e.Session.UserId,
+                    ServerId = (await _serverDbEntry.ServerEntity).Id,
+                }),
+            });
+        }
+        catch (Exception ex)
+        {
+            _sawmill.Error($"Failed to send notification for multi server kick: {ex}");
+        }
+    }
+
+    private bool OnNotificationEarlyFilter()
+    {
+        if (_allowed)
+        {
+            _sawmill.Verbose("Received notification for player join, but multi server play is allowed on this server. Ignoring");
+            return false;
+        }
+
+        return true;
+    }
+
+    // ReSharper disable once AsyncVoidMethod
+    private async void OnNotification(NotificationData notification)
+    {
+        if (!_playerManager.TryGetSessionById(new NetUserId(notification.PlayerId), out var player))
+            return;
+
+        if (notification.ServerId == (await _serverDbEntry.ServerEntity).Id)
+            return;
+
+        if (_adminManager.IsAdmin(player, includeDeAdmin: true))
+            return;
+
+        _sawmill.Info($"Kicking {player} for connecting to another server. Multi-server play is not allowed.");
+        _netManager.DisconnectChannel(player.Channel, _loc.GetString("multi-server-kick-reason"));
+    }
+
+    private sealed class NotificationData
+    {
+        [JsonPropertyName("player_id")]
+        public Guid PlayerId { get; set; }
+
+        [JsonPropertyName("server_id")]
+        public int ServerId { get; set; }
+    }
+}