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[原创]UE4逆向笔记之GObjectArray
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发表于: 2023-1-11 16:01
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GObjectArray逆向：
首先查看源代码：
此处上面存在字符串特征：
1 | Cannot Cancel Async Loading while async loading is suspended. |
直接搜索该字符串就可以定位到GUObjectArray.GetObjectArrayNum():
然后查看GetObjectArrayNum的源代码：
1 2 3 4 | FORCEINLINE int32 GetObjectArrayNum() const { return ObjObjects.Num();} |
跟进ObjObjects发现定义如下：
1 | TUObjectArray ObjObjects; |
继续跟进：
1 | typedef FChunkedFixedUObjectArray TUObjectArray; |
得到如下类：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | class FChunkedFixedUObjectArray{ enum { NumElementsPerChunk = 64 * 1024, }; /** Master table to chunks of pointers **/ FUObjectItem** Objects; /** If requested, a contiguous memory where all objects are allocated **/ FUObjectItem* PreAllocatedObjects; /** Maximum number of elements **/ int32 MaxElements; /** Number of elements we currently have **/ int32 NumElements; /** Maximum number of chunks **/ int32 MaxChunks; /** Number of chunks we currently have **/ int32 NumChunks; |
找到方法的定义如下：
1 2 3 4 | FORCEINLINE int32 Num() const{ return NumElements;} |
发现返回的就是NumElements这个，所以7FF78E0D11A4该地址其实就是ObjObjects.NumElements,而上面存在5个元素，5*4=0x14，所以该地址-0x14就可以得到GObjectArray:
此时的第一个元素为：
1 2 3 4 5 6 7 8 9 10 11 | class FUObjectItem{// Pointer to the allocated objectclass UObjectBase* Object;// Internal flagsint32 Flags;// UObject Owner Cluster Indexint32 ClusterRootIndex;// Weak Object Pointer Serial number associated with the objectint32 SerialNumber;} |
继续查看第一个元素就是UObject:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | class UObject{/** virtual function table */void* vtf;/** Flags used to track and report various object states. This needs to be 8 bytealigned on 32-bitplatforms to reduce memory waste */EObjectFlags ObjectFlags;/** Index into GObjectArray...very private. */int32 InternalIndex; //表明该对象在GObjectArray中的第几个/** Class the object belongs to. */UClass* ClassPrivate;/** Name of this object */FName NamePrivate;/** Object this object resides in. */UObject* OuterPrivate;} |
通过UObject就可以遍历出UE4引擎的所有对象了
使用代码遍历：
通过观察代码我们知道Objct是一个二级指针:
1 | FUObjectItem** Objects; |
也就是说他和Gname一样是以表的形式存在的，所以我们想要遍历他就需要知道当前需要遍历的对象在哪张表中，算法如下：
1 2 3 4 5 6 7 8 9 10 11 12 | UObject* UobjectArray::GetObjectPtr(int id) { if (id >= NumElements) return 0; DWORD64 chunkIndex = id / 65536; //chunkIndex = 0 if (chunkIndex >= NumChunks) return 0; auto chunk = Process::ReadProcess<void*>(Objects+(chunkIndex * 8));// if (!chunk) return 0; DWORD withinChunkIndex = id % 65536 * 32; //这里的32是根据游戏实际结构体大小决定了，默认情况下为32 auto item = Process::ReadProcess<PVOID>((PVOID)((DWORD64)chunk + withinChunkIndex)); return (DWORD64)item;} |
官方给出的SDK代码中就有，可以复制过来直接用：
遍历代码如下：
1 2 3 4 5 6 7 8 9 10 11 12 | GobjectArray = Process::ReadProcess<UobjectArray>((PVOID)((DWORD64)Process::GetProcessMoudleBase() + 0x8031190));//int NumElements = Process::ReadProcess<int>((PVOID)(GobjectArray + 0x14));cout << "NumElements: " << hex << GobjectArray.NumElements << endl;for (int i = 0; i < GobjectArray.NumElements; i++) { cout <<"ID:" << i << " Uobject Address: " << GobjectArray.GetObjectPtr(i) << endl;} |
测试结果：
当能够遍历出Object后还需要使用到Gname遍历Object的名称，具体可以查看我之前的文章，部分代码如下：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 | string GetObjectName(DWORD64 Address) { string Name; DWORD64 UobjectOuter = Process::ReadProcess<DWORD64>((PVOID)(Address + 0x20)); //获取UObject->OuterPrivate if (UobjectOuter != 0) { for (DWORD64 Outer = UobjectOuter; Outer; Outer = Process::ReadProcess<DWORD64>((PVOID)(Outer + 0x20))) { Name = GetName_New(GetFName(Outer).ComparisonIndex) + "." + Name; } Name = GetKlassName(Address) + " " + Name + GetName_New(GetFName(Address).ComparisonIndex); return Name; } Name = GetKlassName(Address) + " " + GetName_New(GetFName(Address).ComparisonIndex); return Name;} |
遍历结果如下：
参考代码：
https://github.com/guttir14/CheatIt
https://github.com/XiaoTouMingyo/UE4ForeachClass
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