Basic rate limiting for chat messages (#21907)

Content.Server/Chat/Managers/ChatManager.RateLimit.cs

@@ -0,0 +1,84 @@
+using System.Runtime.InteropServices;
+using Content.Shared.CCVar;
+using Content.Shared.Database;
+using Robust.Shared.Enums;
+using Robust.Shared.Player;
+using Robust.Shared.Timing;
+
+namespace Content.Server.Chat.Managers;
+
+internal sealed partial class ChatManager
+{
+    private readonly Dictionary<ICommonSession, RateLimitDatum> _rateLimitData = new();
+
+    public bool HandleRateLimit(ICommonSession player)
+    {
+        ref var datum = ref CollectionsMarshal.GetValueRefOrAddDefault(_rateLimitData, player, out _);
+        var time = _gameTiming.RealTime;
+        if (datum.CountExpires < time)
+        {
+            // Period expired, reset it.
+            var periodLength = _configurationManager.GetCVar(CCVars.ChatRateLimitPeriod);
+            datum.CountExpires = time + TimeSpan.FromSeconds(periodLength);
+            datum.Count = 0;
+            datum.Announced = false;
+        }
+
+        var maxCount = _configurationManager.GetCVar(CCVars.ChatRateLimitCount);
+        datum.Count += 1;
+
+        if (datum.Count <= maxCount)
+            return true;
+
+        // Breached rate limits, inform admins if configured.
+        if (_configurationManager.GetCVar(CCVars.ChatRateLimitAnnounceAdmins))
+        {
+            if (datum.NextAdminAnnounce < time)
+            {
+                SendAdminAlert(Loc.GetString("chat-manager-rate-limit-admin-announcement", ("player", player.Name)));
+                var delay = _configurationManager.GetCVar(CCVars.ChatRateLimitAnnounceAdminsDelay);
+                datum.NextAdminAnnounce = time + TimeSpan.FromSeconds(delay);
+            }
+        }
+
+        if (!datum.Announced)
+        {
+            DispatchServerMessage(player, Loc.GetString("chat-manager-rate-limited"), suppressLog: true);
+            _adminLogger.Add(LogType.ChatRateLimited, LogImpact.Medium, $"Player {player} breached chat rate limits");
+
+            datum.Announced = true;
+        }
+
+        return false;
+    }
+
+    private void PlayerStatusChanged(object? sender, SessionStatusEventArgs e)
+    {
+        if (e.NewStatus == SessionStatus.Disconnected)
+            _rateLimitData.Remove(e.Session);
+    }
+
+    private struct RateLimitDatum
+    {
+        /// <summary>
+        /// Time stamp (relative to <see cref="IGameTiming.RealTime"/>) this rate limit period will expire at.
+        /// </summary>
+        public TimeSpan CountExpires;
+
+        /// <summary>
+        /// How many messages have been sent in the current rate limit period.
+        /// </summary>
+        public int Count;
+
+        /// <summary>
+        /// Have we announced to the player that they've been blocked in this rate limit period?
+        /// </summary>
+        public bool Announced;
+
+        /// <summary>
+        /// Time stamp (relative to <see cref="IGameTiming.RealTime"/>) of the
+        /// next time we can send an announcement to admins about rate limit breach.
+        /// </summary>
+        public TimeSpan NextAdminAnnounce;
+    }
+}