#include "stdafx.h"
#include "LoadPe.h"


namespace MWR::Loader
{

#pragma warning( push )
#pragma warning( disable : 4214 ) // nonstandard extension
	typedef struct
	{
		WORD	offset : 12;
		WORD	type : 4;
	} IMAGE_RELOC, * PIMAGE_RELOC;
#pragma warning(pop)

#ifdef _WIN64
	constexpr auto HostMachine = IMAGE_FILE_MACHINE_AMD64;
#else
	constexpr auto HostMachine = IMAGE_FILE_MACHINE_I386;
#endif

	typedef BOOL(WINAPI* DllEntryPoint)(HINSTANCE, DWORD, LPVOID);

	struct
	{
		UINT_PTR m_DllBaseAddress;
		DWORD m_SizeOfTheDll;
	} moduleData;

#if defined _M_AMD64
	void* RtlPcToFileHeaderHook(PVOID pc, PVOID* baseOfImage)
	{
		if (pc > (void*)moduleData.m_DllBaseAddress and pc < (void*)(moduleData.m_DllBaseAddress + moduleData.m_SizeOfTheDll))
		{
			*baseOfImage = 0;
			return (void*)moduleData.m_DllBaseAddress;
		}
		else
		{
			return RtlPcToFileHeader(pc, baseOfImage);
		}
	}
#endif

	void* GetHookAddress(const char* dllName, const char* funcName)
	{
#if defined _M_AMD64
		if (_stricmp(dllName,"kernel32.dll") == 0 && strcmp(funcName, "RtlPcToFileHeader") == 0)
			return (void*)RtlPcToFileHeaderHook;
#endif

		return nullptr;
	}

	int LoadPe(void* dllData, std::string_view callExport)
	{
		// Loader code based on Shellcode Reflective DLL Injection by Nick Landers https://github.com/monoxgas/sRDI
		// which is derived from "Improved Reflective DLL Injection" from Dan Staples https://disman.tl/2015/01/30/an-improved-reflective-dll-injection-technique.html
		// which itself is derived from the original project by Stephen Fewer. https://github.com/stephenfewer/ReflectiveDLLInjection

		auto dosHeader = Rva2Va<PIMAGE_DOS_HEADER>(dllData, 0);
		auto ntHeaders = Rva2Va<PIMAGE_NT_HEADERS>(dllData, dosHeader->e_lfanew);
		auto sizeOfImage = ntHeaders->OptionalHeader.SizeOfImage;

		// Perform sanity checks on the image (Stolen from https://github.com/fancycode/MemoryModule/blob/master/MemoryModule.c)

		if (ntHeaders->Signature != IMAGE_NT_SIGNATURE)
			return 1;

		if (ntHeaders->FileHeader.Machine != HostMachine)
			return 1;

		if (ntHeaders->OptionalHeader.SectionAlignment & 1)
			return 1;

		// Align the image to the page size (Stolen from https://github.com/fancycode/MemoryModule/blob/master/MemoryModule.c)

		auto sectionHeader = IMAGE_FIRST_SECTION(ntHeaders);
		DWORD lastSectionEnd = 0;
		DWORD endOfSection;
		for (size_t i = 0; i < ntHeaders->FileHeader.NumberOfSections; i++, sectionHeader++)
		{
			if (sectionHeader->SizeOfRawData == 0)
				endOfSection = sectionHeader->VirtualAddress + ntHeaders->OptionalHeader.SectionAlignment;
			else
				endOfSection = sectionHeader->VirtualAddress + sectionHeader->SizeOfRawData;

			if (endOfSection > lastSectionEnd)
				lastSectionEnd = endOfSection;
		}

		SYSTEM_INFO sysInfo;
		GetNativeSystemInfo(&sysInfo);
		auto alignedImageSize = AlignValueUp(ntHeaders->OptionalHeader.SizeOfImage, sysInfo.dwPageSize);
		if (alignedImageSize != AlignValueUp(lastSectionEnd, sysInfo.dwPageSize))
			return 1;

		UINT_PTR baseAddress = (UINT_PTR)VirtualAlloc(NULL, alignedImageSize, MEM_RESERVE | MEM_COMMIT, PAGE_READWRITE);
		if (!baseAddress)
			return 1;

		/// Copy headers
		memcpy((void*)baseAddress, dllData, ntHeaders->OptionalHeader.SizeOfHeaders);

		// STEP 3: Load in the sections
		sectionHeader = IMAGE_FIRST_SECTION(ntHeaders);
		for (int i = 0; i < ntHeaders->FileHeader.NumberOfSections; i++, sectionHeader++)
		{
			auto sectionVa = Rva2Va<void*>(baseAddress, sectionHeader->VirtualAddress);
			auto sectionRawData = Rva2Va<void*>(dllData, sectionHeader->PointerToRawData);
			memcpy(sectionVa, sectionRawData, sectionHeader->SizeOfRawData);
		}


		///
		// STEP 4: process all of our images relocations (assuming we missed the preferred address)
		///

		auto baseOffset = (UINT_PTR)baseAddress - ntHeaders->OptionalHeader.ImageBase;
		auto dataDir = &ntHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_BASERELOC];

		if (baseOffset && dataDir->Size)
		{

			auto relocation = Rva2Va<PIMAGE_BASE_RELOCATION>(baseAddress, dataDir->VirtualAddress);

			while (relocation->VirtualAddress)
			{
				auto relocList = (PIMAGE_RELOC)(relocation + 1);

				while ((PBYTE)relocList != (PBYTE)relocation + relocation->SizeOfBlock)
				{

					if (relocList->type == IMAGE_REL_BASED_DIR64)
						*(PULONG_PTR)((PBYTE)baseAddress + relocation->VirtualAddress + relocList->offset) += baseOffset;
					else if (relocList->type == IMAGE_REL_BASED_HIGHLOW)
						*(PULONG_PTR)((PBYTE)baseAddress + relocation->VirtualAddress + relocList->offset) += (DWORD)baseOffset;
					else if (relocList->type == IMAGE_REL_BASED_HIGH)
						*(PULONG_PTR)((PBYTE)baseAddress + relocation->VirtualAddress + relocList->offset) += HIWORD(baseOffset);
					else if (relocList->type == IMAGE_REL_BASED_LOW)
						*(PULONG_PTR)((PBYTE)baseAddress + relocation->VirtualAddress + relocList->offset) += LOWORD(baseOffset);

					relocList++;
				}
				relocation = (PIMAGE_BASE_RELOCATION)relocList;
			}
		}

		///
		// STEP 5: process our import table
		///

		dataDir = &ntHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT];

		if (dataDir->Size)
		{
			auto importDesc = Rva2Va<PIMAGE_IMPORT_DESCRIPTOR>(baseAddress, dataDir->VirtualAddress);
			for (; importDesc->Name; importDesc++)
			{
				auto libName = (LPCSTR)(baseAddress + importDesc->Name);
				auto libraryAddress = (PBYTE)LoadLibraryA(libName);
				auto firstThunk = Rva2Va<PIMAGE_THUNK_DATA>(baseAddress, importDesc->FirstThunk);
				auto origFirstThunk = Rva2Va<PIMAGE_THUNK_DATA>(baseAddress, importDesc->OriginalFirstThunk);

				// iterate through all imported functions, importing by ordinal if no name present
				for (; origFirstThunk->u1.Function; firstThunk++, origFirstThunk++)
				{
					if (IMAGE_SNAP_BY_ORDINAL(origFirstThunk->u1.Ordinal))
					{
						firstThunk->u1.Function = (ULONG_PTR)GetProcAddress((HMODULE)libraryAddress, (LPCSTR)IMAGE_ORDINAL(origFirstThunk->u1.Ordinal));
					}
					else
					{
						auto importByName = Rva2Va<PIMAGE_IMPORT_BY_NAME>(baseAddress, origFirstThunk->u1.AddressOfData);
						void* addr = GetHookAddress(libName, importByName->Name);
						if (!addr)
							addr = GetProcAddress((HMODULE)libraryAddress, importByName->Name);
						firstThunk->u1.Function = (ULONG_PTR)addr;
					}
				}
			}
		}

		///
		// STEP 6: process our delayed import table
		///

		dataDir = &ntHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_DELAY_IMPORT];

		if (dataDir->Size)
		{
			auto delayDesc = Rva2Va<PIMAGE_DELAYLOAD_DESCRIPTOR>(baseAddress, dataDir->VirtualAddress);

			for (; delayDesc->DllNameRVA; delayDesc++)
			{
				auto libName = (LPCSTR)(baseAddress + delayDesc->DllNameRVA);
				auto libraryAddress = (PBYTE)LoadLibraryA(libName);
				auto firstThunk = Rva2Va<PIMAGE_THUNK_DATA>(baseAddress, delayDesc->ImportAddressTableRVA);
				auto origFirstThunk = Rva2Va<PIMAGE_THUNK_DATA>(baseAddress, delayDesc->ImportNameTableRVA);

				// iterate through all imported functions, importing by ordinal if no name present
				for (; firstThunk->u1.Function; firstThunk++, origFirstThunk++)
				{
					if (IMAGE_SNAP_BY_ORDINAL(origFirstThunk->u1.Ordinal))
					{
						firstThunk->u1.Function = (ULONG_PTR)GetProcAddress((HMODULE)libraryAddress, (LPCSTR)IMAGE_ORDINAL(origFirstThunk->u1.Ordinal));
					}
					else
					{
						auto importByName = Rva2Va<PIMAGE_IMPORT_BY_NAME>(baseAddress, origFirstThunk->u1.AddressOfData);
						void* addr = GetHookAddress(libName, importByName->Name);
						if (!addr)
							addr = GetProcAddress((HMODULE)libraryAddress, importByName->Name);
						firstThunk->u1.Function = (ULONG_PTR)addr;
					}
				}
			}
		}

		///
		// STEP 7: Finalize our sections. Set memory protections.
		///
		sectionHeader = IMAGE_FIRST_SECTION(ntHeaders);

		for (int i = 0; i < ntHeaders->FileHeader.NumberOfSections; i++, sectionHeader++)
		{
			if (sectionHeader->SizeOfRawData)
			{
				// determine protection flags based on characteristics
				bool executable = (sectionHeader->Characteristics & IMAGE_SCN_MEM_EXECUTE) != 0;
				bool readable = (sectionHeader->Characteristics & IMAGE_SCN_MEM_READ) != 0;
				bool writeable = (sectionHeader->Characteristics & IMAGE_SCN_MEM_WRITE) != 0;

				DWORD protect = 0;
				if (!executable && !readable && !writeable)
					protect = PAGE_NOACCESS;
				else if (!executable && !readable && writeable)
					protect = PAGE_WRITECOPY;
				else if (!executable && readable && !writeable)
					protect = PAGE_READONLY;
				else if (!executable && readable && writeable)
					protect = PAGE_READWRITE;
				else if (executable && !readable && !writeable)
					protect = PAGE_EXECUTE;
				else if (executable && !readable && writeable)
					protect = PAGE_EXECUTE_WRITECOPY;
				else if (executable && readable && !writeable)
					protect = PAGE_EXECUTE_READ;
				else if (executable && readable && writeable)
					protect = PAGE_EXECUTE_READWRITE;

				if (sectionHeader->Characteristics & IMAGE_SCN_MEM_NOT_CACHED)
					protect |= PAGE_NOCACHE;

				// change memory access flags
				VirtualProtect(Rva2Va<LPVOID>(baseAddress, sectionHeader->VirtualAddress), sectionHeader->SizeOfRawData, protect, &protect);
			}
		}

		// We must flush the instruction cache to avoid stale code being used
		FlushInstructionCache((HANDLE)-1, nullptr, 0);

		///
		// STEP 7.1: Set static TLS values
		///
		MWR::Loader::UnexportedWinApi::LdrpHandleTlsData((void*)baseAddress);

		///
		// STEP 8: execute TLS callbacks
		///
		dataDir = &ntHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_TLS];

		if (dataDir->Size)
		{
			auto tlsDir = Rva2Va<PIMAGE_TLS_DIRECTORY>(baseAddress, dataDir->VirtualAddress);
			auto callback = (PIMAGE_TLS_CALLBACK*)(tlsDir->AddressOfCallBacks);

			for (; *callback; callback++)
				(*callback)((LPVOID)baseAddress, DLL_PROCESS_ATTACH, NULL);
		}

		//
		// STEP 8.1: Add Exception handling
		//
#if defined _M_X64
		auto pImageEntryException = &ntHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXCEPTION];

		if (pImageEntryException->Size > 0)
		{
			auto functionTable = Rva2Va<PRUNTIME_FUNCTION>(baseAddress, pImageEntryException->VirtualAddress);
			DWORD count = pImageEntryException->Size / sizeof(IMAGE_RUNTIME_FUNCTION_ENTRY);
			if (!RtlAddFunctionTable(functionTable, count, (DWORD64)baseAddress))
				return 1;
		}

		// register VEH
		moduleData.m_DllBaseAddress = baseAddress;
		moduleData.m_SizeOfTheDll = ntHeaders->OptionalHeader.SizeOfImage;

#elif defined _M_IX86
		MWR::Loader::UnexportedWinApi::RtlInsertInvertedFunctionTable((void*)baseAddress, ntHeaders->OptionalHeader.SizeOfImage);
#endif

		///
		// STEP 9: call our images entry point
		///
		auto dllEntryPoint = Rva2Va<DllEntryPoint>(baseAddress, ntHeaders->OptionalHeader.AddressOfEntryPoint);
		dllEntryPoint((HINSTANCE)baseAddress, DLL_PROCESS_ATTACH, NULL);

		///
		// STEP 10: call our exported function
		///
		if (!callExport.empty())
		{
			do
			{
				dataDir = &ntHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
				if (!dataDir->Size)
					break;

				auto exportDir = (PIMAGE_EXPORT_DIRECTORY)(baseAddress + dataDir->VirtualAddress);
				if (!exportDir->NumberOfNames || !exportDir->NumberOfFunctions)
					break;

				auto expName = Rva2Va<PDWORD>(baseAddress, exportDir->AddressOfNames);
				auto expOrdinal = Rva2Va<PWORD>(baseAddress, exportDir->AddressOfNameOrdinals);

				for (size_t i = 0; i < exportDir->NumberOfNames; i++, expName++, expOrdinal++)
				{
					auto expNameStr = Rva2Va<LPCSTR>(baseAddress, *expName);

					if (!expNameStr)
						break;

					if (expNameStr == callExport && expOrdinal)
					{
						auto exportFunc = Rva2Va<ExportFunc>(baseAddress, *(PDWORD)(baseAddress + exportDir->AddressOfFunctions + (*expOrdinal * 4)));
						exportFunc();
						break;
					}
				}
			} while (0);
		}

		// STEP 11 Cleanup
#if defined _M_X64
		if (pImageEntryException->Size > 0)
		{
			auto functionTable = Rva2Va<PRUNTIME_FUNCTION>(baseAddress, pImageEntryException->VirtualAddress);
			RtlDeleteFunctionTable(functionTable);
		}
#elif defined _M_IX86
	// TODO cleanup after RtlInsertInvertedFunctionTable -> see ntdll!_RtlRemoveInvertedFunctionTable@4
#endif
		VirtualFree((void*)baseAddress, alignedImageSize, MEM_RELEASE);
		return 0;
	}
}