Validate item deltas on import

Source/items/validation.cpp

@@ -10,6 +10,7 @@
 
 #include "items.h"
 #include "monstdat.h"
+#include "msg.h"
 #include "player.h"
 #include "spells.h"
 #include "utils/is_of.hpp"
@@ -175,4 +176,22 @@ bool IsItemValid(const Player &player, const Item &item)
 	return IsDungeonItemValid(item._iCreateInfo, item.dwBuff);
 }
 
+bool IsItemDeltaValid(const TCmdPItem &itemDelta)
+{
+	if (itemDelta.bCmd == CMD_INVALID)
+		return true;
+	if (IsNoneOf(itemDelta.bCmd, TCmdPItem::FloorItem, TCmdPItem::PickedUpItem, TCmdPItem::DroppedItem))
+		return false;
+	if (!InDungeonBounds({ itemDelta.x, itemDelta.y }))
+		return false;
+	_item_indexes idx = static_cast<_item_indexes>(SDL_SwapLE16(itemDelta.def.wIndx));
+	if (idx == IDI_EAR)
+		return true;
+	if (!IsItemAvailable(idx))
+		return false;
+	Item item = {};
+	RecreateItem(*MyPlayer, itemDelta.item, item);
+	return IsItemValid(*MyPlayer, item);
+}
+
 } // namespace devilution

Source/items/validation.h

@@ -7,17 +7,19 @@
 
 #include <cstdint>
 
+namespace devilution {
+
 // Forward declared structs to avoid circular dependencies
 struct Item;
+struct TCmdPItem;
 struct Player;
 
-namespace devilution {
-
 bool IsCreationFlagComboValid(uint16_t iCreateInfo);
 bool IsTownItemValid(uint16_t iCreateInfo, const Player &player);
 bool IsShopPriceValid(const Item &item);
 bool IsUniqueMonsterItemValid(uint16_t iCreateInfo, uint32_t dwBuff);
 bool IsDungeonItemValid(uint16_t iCreateInfo, uint32_t dwBuff);
 bool IsItemValid(const Player &player, const Item &item);
+bool IsItemDeltaValid(const TCmdPItem &itemDelta);
 
 } // namespace devilution

Source/msg.cpp

@@ -499,6 +499,8 @@ size_t DeltaImportItem(const std::byte *src, TCmdPItem *dst)
 			size++;
 		} else {
 			memcpy(dst, &src[size], sizeof(TCmdPItem));
+			if (!IsItemDeltaValid(*dst))
+				memset(dst, 0xFF, sizeof(TCmdPItem));
 			size += sizeof(TCmdPItem);
 		}
 	}