驱动开发：PE导出函数与RVA转换

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在笔者上篇文章`《驱动开发：内核扫描SSDT挂钩状态》`中简单介绍了如何扫描被挂钩的SSDT函数，并简单介绍了如何解析导出表，本章将继续延申PE导出表的解析，实现一系列灵活的解析如通过传入函数名解析出函数的RVA偏移，ID索引，Index下标等参数，并将其封装为可直接使用的函数，以在后期需要时可以被直接引用，同样为了节约篇幅本章中的`LoadKernelFile()`内存映射函数如需要使用请去前一篇文章中自行摘取。

在笔者上篇文章《内核扫描SSDT挂钩状态》中简单介绍了如何扫描被挂钩的SSDT函数，并简单介绍了如何解析导出表，本章将继续延申PE导出表的解析，实现一系列灵活的解析如通过传入函数名解析出函数的RVA偏移，ID索引，Index下标等参数，并将其封装为可直接使用的函数，以在后期需要时可以被直接引用，同样为了节约篇幅本章中的LoadKernelFile()内存映射函数如需要使用请去前一篇文章中自行摘取。

首先实现GetRvaFromModuleName()函数，当用户传入参数后自动将函数名解析为对应的RVA偏移或Index下标索引值，该函数接收三个参数传递，分别是wzFileName模块名，FunctionName所在模块内的函数名，Flag标志参数，函数输出ULONG64类型的数据。

// 从指定模块中得到特定函数的RVA或相对序号相对偏移
ULONG64 GetRvaFromModuleName(WCHAR *wzFileName, UCHAR *FunctionName, INT Flag)
{
	// 加载内核模块
	PVOID BaseAddress = LoadKernelFile(wzFileName);

	// 取出导出表
	PIMAGE_DOS_HEADER pDosHeader;
	PIMAGE_NT_HEADERS pNtHeaders;
	PIMAGE_SECTION_HEADER pSectionHeader;
	ULONGLONG FileOffset;
	PIMAGE_EXPORT_DIRECTORY pExportDirectory;

	// DLL内存数据转成DOS头结构
	pDosHeader = (PIMAGE_DOS_HEADER)BaseAddress;

	// 取出PE头结构
	pNtHeaders = (PIMAGE_NT_HEADERS)((ULONGLONG)BaseAddress + pDosHeader->e_lfanew);

	// 判断PE头导出表是否为空
	if (pNtHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress == 0)
	{
		return 0;
	}

	// 取出导出表偏移
	FileOffset = pNtHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;

	// 取出节头结构
	pSectionHeader = (PIMAGE_SECTION_HEADER)((ULONGLONG)pNtHeaders + sizeof(IMAGE_NT_HEADERS));
	PIMAGE_SECTION_HEADER pOldSectionHeader = pSectionHeader;

	// 遍历节结构进行地址运算
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}

	// 导出表地址
	pExportDirectory = (PIMAGE_EXPORT_DIRECTORY)((ULONGLONG)BaseAddress + FileOffset);

	// 取出导出表函数地址
	PULONG AddressOfFunctions;
	FileOffset = pExportDirectory->AddressOfFunctions;

	// 遍历节结构进行地址运算
	pSectionHeader = pOldSectionHeader;
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}
	AddressOfFunctions = (PULONG)((ULONGLONG)BaseAddress + FileOffset);

	// 取出导出表函数名字
	PUSHORT AddressOfNameOrdinals;
	FileOffset = pExportDirectory->AddressOfNameOrdinals;

	// 遍历节结构进行地址运算
	pSectionHeader = pOldSectionHeader;
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}
	AddressOfNameOrdinals = (PUSHORT)((ULONGLONG)BaseAddress + FileOffset);

	// 取出导出表函数序号
	PULONG AddressOfNames;
	FileOffset = pExportDirectory->AddressOfNames;

	// 遍历节结构进行地址运算
	pSectionHeader = pOldSectionHeader;
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}
	AddressOfNames = (PULONG)((ULONGLONG)BaseAddress + FileOffset);

	// 分析导出表
	ULONG uOffset;
	LPSTR FunName;
	ULONG uAddressOfNames;
	ULONG TargetOff = 0;

	for (ULONG uIndex = 0; uIndex < pExportDirectory->NumberOfNames; uIndex++, AddressOfNames++, AddressOfNameOrdinals++)
	{
		uAddressOfNames = *AddressOfNames;
		pSectionHeader = pOldSectionHeader;
		for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
		{
			if (pSectionHeader->VirtualAddress <= uAddressOfNames && uAddressOfNames <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
			{
				uOffset = uAddressOfNames - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
			}
		}
		FunName = (LPSTR)((ULONGLONG)BaseAddress + uOffset);

		// 如果找到则返回RVA
		if (!_stricmp((const char *)FunctionName, FunName))
		{
			// 等于1则返回RVA
			if (Flag == 1)
			{
				TargetOff = (ULONG)AddressOfFunctions[*AddressOfNameOrdinals];
				// DbgPrint("索引 [ %p ] 函数名 [ %s ] 相对RVA [ %p ] \n", *AddressOfNameOrdinals, FunName, TargetOff);
				return TargetOff;
			}
			// 返回索引
			else if (Flag == 0)
			{
				return *AddressOfNameOrdinals;
			}
		}
	}

	// 结束后释放内存
	ExFreePoolWithTag(BaseAddress, (ULONG)"LyShark");
	return 0;
}

调用该函数很容易，传入模块路径以及该模块内的函数名，解析出RVA地址或Index下标。

NTSTATUS DriverEntry(IN PDRIVER_OBJECT Driver, PUNICODE_STRING RegistryPath)
{
	// 函数分别传入 [模块路径,函数名,标志=1] 返回该导出函数的RVA
	ULONG64 get_rva = GetRvaFromModuleName(L"\\SystemRoot\\system32\\ntoskrnl.exe", "NtReadFile", 1);
	DbgPrint("NtReadFile RVA = %p \n", get_rva);

	// 函数分别传入 [模块路径,函数名,标志=0] 返回该导出函数的ID下标
	ULONG64 get_id = GetRvaFromModuleName(L"\\SystemRoot\\system32\\ntoskrnl.exe", "NtReadFile", 0);
	DbgPrint("NtReadFile ID = %d \n", get_id);

	Driver->DriverUnload = UnDriver;
	return STATUS_SUCCESS;
}

编译并运行程序，分别获取到ntoskrnl.exe模块内NtReadFile函数的RVA,Index索引，调用效果如下；

第二个函数GetModuleNameFromRVA()则实现传入RVA或者函数Index序号，解析出函数名，具体实现方法与如上函数基本一致，仅仅只是在过滤时做了调整。

// 根据传入的函数RVA或Index下标，获取该函数的函数名
PCHAR GetModuleNameFromRVA(WCHAR *wzFileName, ULONG64 uRVA, INT Flag)
{
	// 加载内核模块
	PVOID BaseAddress = LoadKernelFile(wzFileName);

	// 取出导出表
	PIMAGE_DOS_HEADER pDosHeader;
	PIMAGE_NT_HEADERS pNtHeaders;
	PIMAGE_SECTION_HEADER pSectionHeader;
	ULONGLONG FileOffset;
	PIMAGE_EXPORT_DIRECTORY pExportDirectory;

	// DLL内存数据转成DOS头结构
	pDosHeader = (PIMAGE_DOS_HEADER)BaseAddress;

	// 取出PE头结构
	pNtHeaders = (PIMAGE_NT_HEADERS)((ULONGLONG)BaseAddress + pDosHeader->e_lfanew);

	// 判断PE头导出表是否为空
	if (pNtHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress == 0)
	{
		return 0;
	}

	// 取出导出表偏移
	FileOffset = pNtHeaders->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;

	// 取出节头结构
	pSectionHeader = (PIMAGE_SECTION_HEADER)((ULONGLONG)pNtHeaders + sizeof(IMAGE_NT_HEADERS));
	PIMAGE_SECTION_HEADER pOldSectionHeader = pSectionHeader;

	// 遍历节结构进行地址运算
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}

	// 导出表地址
	pExportDirectory = (PIMAGE_EXPORT_DIRECTORY)((ULONGLONG)BaseAddress + FileOffset);

	// 取出导出表函数地址
	PULONG AddressOfFunctions;
	FileOffset = pExportDirectory->AddressOfFunctions;

	// 遍历节结构进行地址运算
	pSectionHeader = pOldSectionHeader;
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}
	AddressOfFunctions = (PULONG)((ULONGLONG)BaseAddress + FileOffset);

	// 取出导出表函数名字
	PUSHORT AddressOfNameOrdinals;
	FileOffset = pExportDirectory->AddressOfNameOrdinals;

	// 遍历节结构进行地址运算
	pSectionHeader = pOldSectionHeader;
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}
	AddressOfNameOrdinals = (PUSHORT)((ULONGLONG)BaseAddress + FileOffset);

	// 取出导出表函数序号
	PULONG AddressOfNames;
	FileOffset = pExportDirectory->AddressOfNames;

	// 遍历节结构进行地址运算
	pSectionHeader = pOldSectionHeader;
	for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
	{
		if (pSectionHeader->VirtualAddress <= FileOffset && FileOffset <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
		{
			FileOffset = FileOffset - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
		}
	}
	AddressOfNames = (PULONG)((ULONGLONG)BaseAddress + FileOffset);

	// 分析导出表
	ULONG uOffset;
	LPSTR FunName;
	ULONG uAddressOfNames;
	ULONG TargetOff = 0;

	for (ULONG uIndex = 0; uIndex < pExportDirectory->NumberOfNames; uIndex++, AddressOfNames++, AddressOfNameOrdinals++)
	{
		uAddressOfNames = *AddressOfNames;
		pSectionHeader = pOldSectionHeader;
		for (UINT16 Index = 0; Index < pNtHeaders->FileHeader.NumberOfSections; Index++, pSectionHeader++)
		{
			if (pSectionHeader->VirtualAddress <= uAddressOfNames && uAddressOfNames <= pSectionHeader->VirtualAddress + pSectionHeader->SizeOfRawData)
			{
				uOffset = uAddressOfNames - pSectionHeader->VirtualAddress + pSectionHeader->PointerToRawData;
			}
		}

		FunName = (LPSTR)((ULONGLONG)BaseAddress + uOffset);
		TargetOff = (ULONG)AddressOfFunctions[*AddressOfNameOrdinals];

		// 等于1则通过RVA返回函数名
		if (Flag == 1)
		{
			if (uRVA == TargetOff)
			{
				return FunName;
			}
		}
		// 返回索引
		else if (Flag == 0)
		{
			if (uRVA == *AddressOfNameOrdinals)
			{
				return FunName;
			}
		}
	}

	// 结束后释放内存
	ExFreePoolWithTag(BaseAddress, (ULONG)"LyShark");
	return "None";
}

调用GetModuleNameFromRVA()并传入相应的RVA偏移或Index下标。

NTSTATUS DriverEntry(IN PDRIVER_OBJECT Driver, PUNICODE_STRING RegistryPath)
{
	DbgPrint("hello lyshark.com \n");

	PCHAR function_name;

	// 传入函数RVA得到函数名
	function_name = GetModuleNameFromRVA(L"\\SystemRoot\\system32\\ntoskrnl.exe", 0x5e5220, 1);
	DbgPrint("根据RVA得到函数名 = %s \n", function_name);

	// 传入函数下标得到函数名
	function_name = GetModuleNameFromRVA(L"\\SystemRoot\\system32\\ntoskrnl.exe", 1472, 0);
	DbgPrint("根据Index得到函数名 = %s \n", function_name);

	Driver->DriverUnload = UnDriver;
	return STATUS_SUCCESS;
}

编译并运行程序，调用后分别获取到RVA=0x5e5220或Index=1472的函数名；