驱动开发：内核运用LoadImage屏蔽驱动

在笔者上一篇文章《内核监视LoadImage映像回调》中LyShark简单介绍了如何通过PsSetLoadImageNotifyRoutine函数注册回调来监视驱动模块的加载，注意我这里用的是监视而不是监控之所以是监视而不是监控那是因为PsSetLoadImageNotifyRoutine无法实现参数控制，而如果我们想要控制特定驱动的加载则需要自己做一些事情来实现，如下LyShark将解密如何实现屏蔽特定驱动的加载。

要想实现驱动屏蔽其原理很简单，通过ImageInfo->ImageBase得到镜像基地址，然后调用GetDriverEntryByImageBase函数来得到程序的入口地址，找NT头的OptionalHeader节点，该节点里面就是被加载驱动入口，通过汇编在驱动头部写入ret返回指令，即可实现屏蔽加载特定驱动文件。

原理其实很容易理解，如果我们需要实现则只需要在《内核监视LoadImage映像回调》这篇文章的代码上稍加改进即可，当检测到lyshark.sys驱动加载时，直接跳转到入口处快速写入一个Ret让驱动返回即可，至于如何写出指令的问题如果不懂建议回头看看《内核CR3切换读写内存》文章中是如何读写内存的，这段代码实现如下所示。

#include <ntddk.h>
#include <intrin.h>
#include <ntimage.h>

PVOID GetDriverEntryByImageBase(PVOID ImageBase)
{
	PIMAGE_DOS_HEADER pDOSHeader;
	PIMAGE_NT_HEADERS64 pNTHeader;
	PVOID pEntryPoint;
	pDOSHeader = (PIMAGE_DOS_HEADER)ImageBase;
	pNTHeader = (PIMAGE_NT_HEADERS64)((ULONG64)ImageBase + pDOSHeader->e_lfanew);
	pEntryPoint = (PVOID)((ULONG64)ImageBase + pNTHeader->OptionalHeader.AddressOfEntryPoint);
	return pEntryPoint;
}

VOID UnicodeToChar(PUNICODE_STRING dst, char *src)
{
	ANSI_STRING string;
	RtlUnicodeStringToAnsiString(&string, dst, TRUE);
	strcpy(src, string.Buffer);
	RtlFreeAnsiString(&string);
}

// 使用开关写保护需要在[C/C++]->[优化]->启用内部函数
// 关闭写保护
KIRQL  WPOFFx64()
{
	KIRQL  irql = KeRaiseIrqlToDpcLevel();
	UINT64  cr0 = __readcr0();
	cr0 &= 0xfffffffffffeffff;
	_disable();
	__writecr0(cr0);
	return  irql;
}

// 开启写保护
void  WPONx64(KIRQL  irql)
{
	UINT64  cr0 = __readcr0();
	cr0 |= 0x10000;
	_enable();
	__writecr0(cr0);
	KeLowerIrql(irql);
}

BOOLEAN DenyLoadDriver(PVOID DriverEntry)
{
	UCHAR fuck[] = "\xB8\x22\x00\x00\xC0\xC3";
	KIRQL kirql;
	/* 在模块开头写入以下汇编指令
	Mov eax,c0000022h
	ret
	*/
	if (DriverEntry == NULL) return FALSE;
	kirql = WPOFFx64();
	memcpy(DriverEntry, fuck, sizeof(fuck) / sizeof(fuck[0]));
	WPONx64(kirql);
	return TRUE;
}

VOID MyLySharkComLoadImageNotifyRoutine(PUNICODE_STRING FullImageName, HANDLE ModuleStyle, PIMAGE_INFO ImageInfo)
{
	PVOID pDrvEntry;
	char szFullImageName[256] = { 0 };

	// MmIsAddress 验证地址可用性
	if (FullImageName != NULL && MmIsAddressValid(FullImageName))
	{
		// ModuleStyle为零表示加载sys
		if (ModuleStyle == 0)
		{
			pDrvEntry = GetDriverEntryByImageBase(ImageInfo->ImageBase);
			UnicodeToChar(FullImageName, szFullImageName);
			if (strstr(_strlwr(szFullImageName), "lyshark.sys"))
			{
				DbgPrint("[LyShark] 拦截SYS内核模块：%s", szFullImageName);
				DenyLoadDriver(pDrvEntry);
			}
		}
	}
}

VOID UnDriver(PDRIVER_OBJECT driver)
{
	PsRemoveLoadImageNotifyRoutine((PLOAD_IMAGE_NOTIFY_ROUTINE)MyLySharkComLoadImageNotifyRoutine);
	DbgPrint("驱动卸载完成...");
}

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

	PsSetLoadImageNotifyRoutine((PLOAD_IMAGE_NOTIFY_ROUTINE)MyLySharkComLoadImageNotifyRoutine);
	DbgPrint("驱动加载完成...");
	Driver->DriverUnload = UnDriver;
	return STATUS_SUCCESS;
}

首先运行我们的驱动，然后我们接着加载lyshark.sys则你会发现驱动被拦截了。

我们看下驱动加载器，提示的信息是拒绝访问，因为这个驱动其实是加载了的，只是入口处被填充了返回而已。

除了使用Ret强制返回的方法意外，屏蔽驱动加载还可以使用另一种方式实现禁用模块加载，例如当驱动被加载首先回调函数内可以接收到，当接收到以后直接调用MmUnmapViewOfSection函数强制卸载掉即可，如果使用这种方法实现则这段代码需要改进成如下样子。

// 署名权
// right to sign one's name on a piece of work
// PowerBy: LyShark
// Email: me@lyshark.com
#include <ntifs.h>
#include <ntimage.h>
#include <intrin.h>

NTSTATUS MmUnmapViewOfSection(PEPROCESS Process, PVOID BaseAddress);
NTSTATUS SetNotifyRoutine();
NTSTATUS RemoveNotifyRoutine();

VOID LoadImageNotifyRoutine(PUNICODE_STRING FullImageName, HANDLE ProcessId, PIMAGE_INFO ImageInfo);
NTSTATUS U2C(PUNICODE_STRING pustrSrc, PCHAR pszDest, ULONG ulDestLength);
VOID ThreadProc(_In_ PVOID StartContext);

// 拒绝加载驱动
NTSTATUS DenyLoadDriver(PVOID pImageBase);

// 拒绝加载DLL模块
NTSTATUS DenyLoadDll(HANDLE ProcessId, PVOID pImageBase);

typedef struct _MY_DATA
{
	HANDLE ProcessId;
	PVOID pImageBase;
}MY_DATA, *PMY_DATA;

// 设置消息回调
NTSTATUS SetNotifyRoutine()
{
	NTSTATUS status = STATUS_SUCCESS;
	status = PsSetLoadImageNotifyRoutine(LoadImageNotifyRoutine);
	return status;
}

// 关闭消息回调
NTSTATUS RemoveNotifyRoutine()
{
	NTSTATUS status = STATUS_SUCCESS;
	status = PsRemoveLoadImageNotifyRoutine(LoadImageNotifyRoutine);
	return status;
}

VOID LoadImageNotifyRoutine(PUNICODE_STRING FullImageName, HANDLE ProcessId, PIMAGE_INFO ImageInfo)
{
	DbgPrint("PID: %d --> 完整路径: %wZ --> 大小: %d --> 基地址: 0x%p \n", ProcessId, FullImageName, ImageInfo->ImageSize, ImageInfo->ImageBase);

	HANDLE hThread = NULL;
	CHAR szTemp[1024] = { 0 };
	U2C(FullImageName, szTemp, 1024);
	if (NULL != strstr(szTemp, "lyshark.sys"))
	{
		// EXE或者DLL
		if (0 != ProcessId)
		{
			// 创建多线程 延时1秒钟后再卸载模块
			PMY_DATA pMyData = ExAllocatePool(NonPagedPool, sizeof(MY_DATA));
			pMyData->ProcessId = ProcessId;
			pMyData->pImageBase = ImageInfo->ImageBase;
			PsCreateSystemThread(&hThread, 0, NULL, NtCurrentProcess(), NULL, ThreadProc, pMyData);
			DbgPrint("[LyShark] 禁止加载DLL文件 \n");
		}
		// 驱动
		else
		{
			DenyLoadDriver(ImageInfo->ImageBase);
			DbgPrint("[LyShark] 禁止加载SYS驱动文件 \n");
		}
	}
}

// 拒绝加载驱动
NTSTATUS DenyLoadDriver(PVOID pImageBase)
{
	NTSTATUS status = STATUS_SUCCESS;
	PMDL pMdl = NULL;
	PVOID pVoid = NULL;
	ULONG ulShellcodeLength = 16;
	UCHAR pShellcode[16] = { 0xB8, 0x22, 0x00, 0x00, 0xC0, 0xC3, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90, 0x90 };
	PIMAGE_DOS_HEADER pDosHeader = pImageBase;
	PIMAGE_NT_HEADERS pNtHeaders = (PIMAGE_NT_HEADERS)((PUCHAR)pDosHeader + pDosHeader->e_lfanew);
	PVOID pDriverEntry = (PVOID)((PUCHAR)pDosHeader + pNtHeaders->OptionalHeader.AddressOfEntryPoint);

	pMdl = MmCreateMdl(NULL, pDriverEntry, ulShellcodeLength);
	MmBuildMdlForNonPagedPool(pMdl);
	pVoid = MmMapLockedPages(pMdl, KernelMode);
	RtlCopyMemory(pVoid, pShellcode, ulShellcodeLength);
	MmUnmapLockedPages(pVoid, pMdl);
	IoFreeMdl(pMdl);

	return status;
}

// 调用 MmUnmapViewOfSection 函数来卸载已经加载的 DLL 模块
NTSTATUS DenyLoadDll(HANDLE ProcessId, PVOID pImageBase)
{
	NTSTATUS status = STATUS_SUCCESS;
	PEPROCESS pEProcess = NULL;

	status = PsLookupProcessByProcessId(ProcessId, &pEProcess);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	// 卸载模块
	status = MmUnmapViewOfSection(pEProcess, pImageBase);
	if (!NT_SUCCESS(status))
	{
		return status;
	}
	return status;
}

VOID ThreadProc(_In_ PVOID StartContext)
{
	PMY_DATA pMyData = (PMY_DATA)StartContext;
	LARGE_INTEGER liTime = { 0 };

	// 延时 1 秒 负值表示相对时间
	liTime.QuadPart = -10 * 1000 * 1000;
	KeDelayExecutionThread(KernelMode, FALSE, &liTime);

	// 卸载
	DenyLoadDll(pMyData->ProcessId, pMyData->pImageBase);

	ExFreePool(pMyData);
}

NTSTATUS U2C(PUNICODE_STRING pustrSrc, PCHAR pszDest, ULONG ulDestLength)
{
	NTSTATUS status = STATUS_SUCCESS;
	ANSI_STRING strTemp;

	RtlZeroMemory(pszDest, ulDestLength);
	RtlUnicodeStringToAnsiString(&strTemp, pustrSrc, TRUE);
	if (ulDestLength > strTemp.Length)
	{
		RtlCopyMemory(pszDest, strTemp.Buffer, strTemp.Length);
	}
	RtlFreeAnsiString(&strTemp);

	return status;
}

VOID UnDriver(PDRIVER_OBJECT driver)
{
	PsRemoveLoadImageNotifyRoutine((PLOAD_IMAGE_NOTIFY_ROUTINE)RemoveNotifyRoutine);
	DbgPrint("驱动卸载完成...");
}

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

	PsSetLoadImageNotifyRoutine((PLOAD_IMAGE_NOTIFY_ROUTINE)SetNotifyRoutine);
	DbgPrint("驱动加载完成...");
	Driver->DriverUnload = UnDriver;
	return STATUS_SUCCESS;
}

加载这段驱动程序，当有DLL文件被加载后，则会强制弹出，从而实现屏蔽模块加载的作用。

当然用LoadImage回调做监控并不靠谱，因为它很容易被绕过，其实系统里存在一个开关，叫做PspNotifyEnableMask如果它的值被设置为0，那么所有的相关操作都不会经过回调，所有回调都会失效。