The onPlayerDamageCancelled event for improved server-side cheat detection

Client/mods/deathmatch/logic/CClientGame.cpp

@@ -4412,6 +4412,25 @@ bool CClientGame::ApplyPedDamageFromGame(eWeaponType weaponUsed, float fDamage,
             }
             pDamagedPed->GetGamePlayer()->SetHealth(fPreviousHealth);
             pDamagedPed->GetGamePlayer()->SetArmor(fPreviousArmor);
+
+            if (IS_PLAYER(pDamagedPed) && pDamagedPed->IsLocalPlayer() && g_pNet->CanServerBitStream(eBitStreamVersion::PlayerDamageCancelled))
+            {
+                if (auto stream = g_pNet->AllocateNetBitStream())
+                {
+                    if (pInflictingEntity)
+                        stream->Write(pInflictingEntity->GetID());
+                    else
+                        stream->Write(0);
+
+                    stream->Write(static_cast<std::uint8_t>(weaponUsed));
+                    stream->Write(static_cast<std::uint8_t>(hitZone));
+                    stream->Write(fDamage);
+
+                    g_pNet->SendPacket(PACKET_ID_PLAYER_DAMAGE_CANCELLED, stream, PACKET_PRIORITY_HIGH, PACKET_RELIABILITY_RELIABLE_ORDERED);
+                    g_pNet->DeallocateNetBitStream(stream);
+                }
+            }
+
             return false;
         }
 

Server/mods/deathmatch/logic/CGame.cpp

@@ -59,6 +59,7 @@
 #include "packets/CPlayerListPacket.h"
 #include "packets/CPlayerClothesPacket.h"
 #include "packets/CPlayerWorldSpecialPropertyPacket.h"
+#include "packets/CPlayerDamageCancelledPacket.h"
 #include "packets/CServerInfoSyncPacket.h"
 #include "packets/CLuaPacket.h"
 #include "../utils/COpenPortsTester.h"
@@ -1322,6 +1323,12 @@ bool CGame::ProcessPacket(CPacket& Packet)
             return true;
         }
 
+        case PACKET_ID_PLAYER_DAMAGE_CANCELLED:
+        {
+            Packet_PlayerDamageCancelled(static_cast<CPlayerDamageCancelledPacket&>(Packet));
+            return true;
+        }
+
         default:
             break;
     }
@@ -1642,6 +1649,7 @@ void CGame::AddBuiltInEvents()
     m_Events.AddEvent("onPlayerChangesProtectedData", "element, key, value", nullptr, false);
     m_Events.AddEvent("onPlayerChangesWorldSpecialProperty", "property, enabled", nullptr, false);
     m_Events.AddEvent("onPlayerTeleport", "previousX, previousY, previousZ, currentX, currentY, currentZ", nullptr, false);
+    m_Events.AddEvent("onPlayerDamageCancelled", "attacker, cause, bodypart, loss", nullptr, false);
 
     // Ped events
     m_Events.AddEvent("onPedVehicleEnter", "vehicle, seat, jacked", NULL, false);
@@ -4307,6 +4315,32 @@ void CGame::Packet_PlayerWorldSpecialProperty(CPlayerWorldSpecialPropertyPacket&
     player->CallEvent("onPlayerChangesWorldSpecialProperty", arguments, nullptr);
 }
 
+void CGame::Packet_PlayerDamageCancelled(CPlayerDamageCancelledPacket& packet) noexcept
+{
+    CPlayer* player = packet.GetSourcePlayer();
+
+    if (!player)
+        return;
+
+    const std::uint32_t attacker = packet.GetAttacker();
+    const std::uint8_t cause = packet.GetCause();
+    const std::uint8_t bodypart = packet.GetBodypart();
+    const float loss = packet.GetLoss();
+
+    CLuaArguments arguments;
+
+    if (GetElementFromId<CElement>(attacker))
+        arguments.PushElement(GetElementFromId<CElement>(attacker));
+    else
+        arguments.PushNil();
+
+    arguments.PushNumber(cause);
+    arguments.PushNumber(bodypart);
+    arguments.PushNumber(loss);
+
+    player->CallEvent("onPlayerDamageCancelled", arguments, nullptr);
+}
+
 void CGame::Packet_PlayerModInfo(CPlayerModInfoPacket& Packet)
 {
     CPlayer* pPlayer = Packet.GetSourcePlayer();

Server/mods/deathmatch/logic/CGame.h

@@ -519,6 +519,7 @@ class CGame
     void Packet_PlayerNetworkStatus(class CPlayerNetworkStatusPacket& Packet);
     void Packet_PlayerResourceStart(class CPlayerResourceStartPacket& Packet);
     void Packet_PlayerWorldSpecialProperty(class CPlayerWorldSpecialPropertyPacket& packet) noexcept;
+    void Packet_PlayerDamageCancelled(class CPlayerDamageCancelledPacket& packet) noexcept;
 
     static void PlayerCompleteConnect(CPlayer* pPlayer);
 

Server/mods/deathmatch/logic/CPacketTranslator.cpp

@@ -49,6 +49,7 @@
 #include "packets/CPlayerNetworkStatusPacket.h"
 #include "packets/CPlayerResourceStartPacket.h"
 #include "packets/CPlayerWorldSpecialPropertyPacket.h"
+#include "packets/CPlayerDamageCancelledPacket.h"
 
 CPacketTranslator::CPacketTranslator(CPlayerManager* pPlayerManager)
 {
@@ -217,6 +218,10 @@ CPacket* CPacketTranslator::Translate(const NetServerPlayerID& Socket, ePacketID
             pTemp = new CPlayerWorldSpecialPropertyPacket;
             break;
 
+        case PACKET_ID_PLAYER_DAMAGE_CANCELLED:
+            pTemp = new CPlayerDamageCancelledPacket;
+            break;
+
         default:
             break;
     }

Server/mods/deathmatch/logic/packets/CPlayerDamageCancelledPacket.cpp

@@ -0,0 +1,22 @@
+/*****************************************************************************
+ *
+ *  PROJECT:     Multi Theft Auto
+ *  LICENSE:     See LICENSE in the top level directory
+ *  FILE:        mods/deathmatch/logic/packets/CPlayerDamageCancelledPacket.cpp
+ *
+ *  Multi Theft Auto is available from https://www.multitheftauto.com/
+ *
+ *****************************************************************************/
+
+#include "StdInc.h"
+#include "CPlayerDamageCancelledPacket.h"
+
+bool CPlayerDamageCancelledPacket::Read(NetBitStreamInterface& stream) noexcept
+{
+    stream.Read(m_attacker);
+    stream.Read(m_cause);
+    stream.Read(m_bodypart);
+    stream.Read(m_loss);
+
+    return true;
+}

Server/mods/deathmatch/logic/packets/CPlayerDamageCancelledPacket.h

@@ -0,0 +1,38 @@
+/*****************************************************************************
+ *
+ *  PROJECT:     Multi Theft Auto
+ *  LICENSE:     See LICENSE in the top level directory
+ *  FILE:        mods/deathmatch/logic/packets/CPlayerDamageCancelledPacket.h
+ *
+ *  Multi Theft Auto is available from https://www.multitheftauto.com/
+ *
+ *****************************************************************************/
+
+#pragma once
+
+#include <string>
+#include <cstdint>
+#include "CPacket.h"
+
+class CPlayerDamageCancelledPacket final : public CPacket
+{
+public:
+    CPlayerDamageCancelledPacket() noexcept {}
+
+    ePacketID               GetPacketID() const noexcept { return PACKET_ID_PLAYER_DAMAGE_CANCELLED; }
+    unsigned long           GetFlags() const noexcept { return PACKET_HIGH_PRIORITY | PACKET_RELIABLE | PACKET_SEQUENCED; }
+    virtual ePacketOrdering GetPacketOrdering() const noexcept { return PACKET_ORDERING_DEFAULT; }
+
+    bool Read(NetBitStreamInterface& stream) noexcept;
+
+    std::uint32_t GetAttacker() const noexcept { return m_attacker; }
+    std::uint8_t GetCause() const noexcept { return m_cause; }
+    std::uint8_t GetBodypart() const noexcept { return m_bodypart; }
+    float GetLoss() const noexcept { return m_loss; }
+
+private:
+    std::uint32_t m_attacker;
+    std::uint8_t m_cause;
+    std::uint8_t m_bodypart;
+    float m_loss;
+};

Shared/mods/deathmatch/logic/Enums.cpp

@@ -216,4 +216,5 @@ ADD_ENUM1(PACKET_ID_SERVER_INFO_SYNC)
 ADD_ENUM1(PACKET_ID_DISCORD_JOIN)
 ADD_ENUM1(PACKET_ID_PLAYER_RESOURCE_START)
 ADD_ENUM1(PACKET_ID_PLAYER_WORLD_SPECIAL_PROPERTY)
+ADD_ENUM1(PACKET_ID_PLAYER_DAMAGE_CANCELLED)
 IMPLEMENT_ENUM_END("ePacketID")

Shared/sdk/net/Packets.h

@@ -151,5 +151,6 @@ enum ePacketID
     PACKET_ID_SERVER_INFO_SYNC,
     PACKET_ID_DISCORD_JOIN,
     PACKET_ID_PLAYER_RESOURCE_START,
-    PACKET_ID_PLAYER_WORLD_SPECIAL_PROPERTY
+    PACKET_ID_PLAYER_WORLD_SPECIAL_PROPERTY,
+    PACKET_ID_PLAYER_DAMAGE_CANCELLED
 };

Shared/sdk/net/bitstream.h

@@ -612,6 +612,10 @@ enum class eBitStreamVersion : unsigned short
     // 2025-01-29
     PedSync_CameraRotation,
 
+    // Add onPlayerDamageCancelled
+    // 2025-02-21
+    PlayerDamageCancelled,
+
     // This allows us to automatically increment the BitStreamVersion when things are added to this enum.
     // Make sure you only add things above this comment.
     Next,