驅動開發：通過Async反向與內核通信

在前幾篇文章中給大家具體解釋了驅動與應用層之間正向通信的一些經典案例，本章將繼續學習驅動通信，不過這次我們學習的是通過運用Async異步模式實作的反向通信，反向通信機制在開發中時常被用到，例如一個殺毒軟體如果監控到有例外行程運行或有例外注冊表被改寫后，該驅動需要主動的通知應用層行程讓其知道，這就需要用到驅動反向通信的相關知識點，如下將循序漸進的實作一個反向通信案例，

在開始學習Async反向通信之前先來研究一個Sync正向通信案例，不論是正向反向通信其在通信模式上與《驅動開發：通過ReadFile與內核層通信》所介紹的通信模式基本一致，都是通過ReadFile觸發驅動中的IRP_MJ_READ讀取派遣，唯一的區別是在傳輸資料時使用了MmGetSystemAddressForMdl方式，它將給定MDL描述的物理頁面映射到系統空間，并呼叫RtlCopyMemory()將全域字串復制到這個空間內，這樣客戶端就可以回圈讀取內核傳出的資料，

我們來看驅動端代碼是如何實作的這個功能，代碼并沒有什么特殊的無法理解的點，只是需要注意我們在驅動入口呼叫IoCreateDevice()時傳入了第二個引數FILE_DEVICE_EXTENSION，該引數的作用是，創建設備時，指定設備擴展記憶體的大小，傳一個值進去，就會給設備分配一塊非頁面記憶體，

#include <ntddk.h>
#include <stdio.h>

// 保存一段非分頁記憶體,用于給全域變數使用
#define FILE_DEVICE_EXTENSION 4096

// 定義全域字串
static int global_count = 0;
static char global_char[5][128] = { 0 };

// 驅動系結默認派遣函式
NTSTATUS _DefaultDispatch(PDEVICE_OBJECT _pDeviceObject, PIRP _pIrp)
{
	_pIrp->IoStatus.Status = STATUS_NOT_SUPPORTED;
	_pIrp->IoStatus.Information = 0;
	IoCompleteRequest(_pIrp, IO_NO_INCREMENT);
	return _pIrp->IoStatus.Status;
}

// 驅動創建后觸發
NTSTATUS _SyncCreateCloseDispatch(PDEVICE_OBJECT _pDevcieObject, PIRP _pIrp)
{
	_pIrp->IoStatus.Status = STATUS_SUCCESS;
	_pIrp->IoStatus.Information = 0;
	IoCompleteRequest(_pIrp, IO_NO_INCREMENT);
	return _pIrp->IoStatus.Status;
}

// 應用層讀資料后觸發
NTSTATUS _SyncReadDispatch(PDEVICE_OBJECT _pDeviceObject, PIRP _pIrp)
{
	NTSTATUS status = STATUS_SUCCESS;
	PIO_STACK_LOCATION pIrpStack = IoGetCurrentIrpStackLocation(_pIrp);
	PVOID pBuffer = NULL;
	ULONG uBufferLen = 0;

	do
	{
		// 讀寫請求使用的是直接I/O方式
		pBuffer = MmGetSystemAddressForMdl(_pIrp->MdlAddress);
		if (pBuffer == NULL)
		{
			status = STATUS_UNSUCCESSFUL;
			break;
		}
		uBufferLen = pIrpStack->Parameters.Read.Length;
		DbgPrint("讀位元組長度: %d \n", uBufferLen);

		// 最大支持20位元組讀請求
		uBufferLen = uBufferLen >= 20 ? 20 : uBufferLen;

		// 輸出五次字串
		if (global_count < 5)
		{
			RtlCopyMemory(pBuffer, global_char[global_count], uBufferLen);
			global_count = global_count + 1;
		}

	} while (FALSE);

	// 填寫回傳狀態及回傳大小
	_pIrp->IoStatus.Status = status;
	_pIrp->IoStatus.Information = uBufferLen;

	// 完成IRP
	IoCompleteRequest(_pIrp, IO_NO_INCREMENT);
	return status;
}

// 卸載驅動
VOID _UnloadDispatch(PDRIVER_OBJECT _pDriverObject)
{
	// 洗掉創建的設備
	UNICODE_STRING  Win32DeviceName;
	RtlInitUnicodeString(&Win32DeviceName, L"\\DosDevices\\LySharkSync");
	IoDeleteDevice(_pDriverObject->DeviceObject);
}

// 驅動入口
NTSTATUS DriverEntry(PDRIVER_OBJECT _pDriverObject, PUNICODE_STRING _pRegistryPath)
{
	UNICODE_STRING DeviceName, Win32DeivceName;
	PDEVICE_OBJECT pDeviceObject = NULL;
	NTSTATUS status;
	HANDLE hThread;
	OBJECT_ATTRIBUTES ObjectAttributes;

	// 設定符號名
	RtlInitUnicodeString(&DeviceName, L"\\Device\\LySharkSync");
	RtlInitUnicodeString(&Win32DeivceName, L"\\DosDevices\\LySharkSync");

	// 回圈初始化IRP函式
	for (ULONG i = 0; i <= IRP_MJ_MAXIMUM_FUNCTION; i++)
	{
		_pDriverObject->MajorFunction[i] = _DefaultDispatch;
	}

	// 再次覆寫派遣函式
	_pDriverObject->MajorFunction[IRP_MJ_CREATE] = _SyncCreateCloseDispatch;
	_pDriverObject->MajorFunction[IRP_MJ_CLOSE] = _SyncCreateCloseDispatch;
	_pDriverObject->MajorFunction[IRP_MJ_READ] = _SyncReadDispatch;
	_pDriverObject->DriverUnload = _UnloadDispatch;

	// 分配一個自定義擴展 大小為sizeof（DEVEXT）
	// By: LyShark.com
	status = IoCreateDevice(_pDriverObject, sizeof(FILE_DEVICE_EXTENSION), &DeviceName, FILE_DEVICE_UNKNOWN, 0, FALSE, &pDeviceObject);
	if (!NT_SUCCESS(status))
		return status;
	
	if (!pDeviceObject)
		return STATUS_UNEXPECTED_IO_ERROR;

	// 為全域變數賦值
	strcpy(global_char[0], "hi,lyshark A");
	strcpy(global_char[1], "hi,lyshark B");
	strcpy(global_char[2], "hi,lyshark C");
	strcpy(global_char[3], "hi,lyshark D");
	strcpy(global_char[4], "hi,lyshark E");

	// 指定讀寫方式為 直接I/O MDL模式
	pDeviceObject->Flags |= DO_DIRECT_IO;

	// 資料傳輸時地址校驗大小
	pDeviceObject->AlignmentRequirement = FILE_WORD_ALIGNMENT;
	status = IoCreateSymbolicLink(&Win32DeivceName, &DeviceName);

	pDeviceObject->Flags &= ~DO_DEVICE_INITIALIZING;
	return STATUS_SUCCESS;
}

對于應用層來說并沒有什么特別的，同樣呼叫ReadFile讀取內核中的引數，同樣for回圈讀取五次，代碼如下：

#include <stdio.h>
#include <Windows.h>

int main(int argc, char *argv[])
{
	HANDLE hFile;
	char Buffer[10] = { 0 };
	DWORD dwRet = 0;
	BOOL bRet;

	hFile = CreateFileA("\\\\.\\LySharkSync", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
	if (hFile == INVALID_HANDLE_VALUE)
		return 0;

	for (int x = 0; x < 5; x++)
	{
		bRet = ReadFile(hFile, Buffer, 20, &dwRet, NULL);
		if (!bRet)
		{
			CloseHandle(hFile);
			return 0;
		}
		printf("讀入資料: %s -> 讀取長度: %d \n", Buffer, dwRet);
	}
	return 0;
}

這段代碼運行效果如下：

與同步模式不同，異步模式雖然同樣使用ReadFile實作通信，但在通信中引入了Event事件通知機制，這也是異步與同步最大的區別所在，用戶層可以分別創建多個Event事件，等待內核依次做出相應并最終一并回傳，

首先驅動內定義了_DeviceExtension自定義介面，該介面用于保存此次事件所對應的Irp以及其所對應的DPC時間等，

異步分發函式_AsyncReadDispatch同樣是被IRP_MJ_READ派遣函式觸發的，觸發后其內部會首先IoGetCurrentIrpStackLocation得到當前IRP的堆疊資訊，然后設定IoMarkIrpPending()并最終將該IRP通過InsertTailList()插入到IRP鏈表內等待被處理，

• IoMarkIrpPending
  • 用于標記指定的IRP，標志著某個驅動的分發例程（分發函式）因需要被其他的驅動程式進一步處理最侄訓傳STATUS_PENDING狀態，

函式_CustomDpc則是定時器內部要執行的具體操作，在DriverEntry驅動入口處做了如下初始化，初始化了鏈表，并初始化了一個定時器，最后啟動這個定時器每隔1秒都會執行一次_CustomDpc如果我們的IRP鏈表內IsListEmpty() 檢測存在資料，則會主動拷貝記憶體RtlCopyMemory并推送到應用層，

// 初始化IRP鏈表
InitializeListHead(&pDevExt->IrpList);
// 初始化定時器
KeInitializeTimer(&(pDevExt->timer));
// 初始化DPC pDevExt是傳給_CustomDpc函式的引數
KeInitializeDpc(&pDevExt->dpc, (PKDEFERRED_ROUTINE)_CustomDpc, pDevExt);

// 設定定時時間位1s
pDevExt->liDueTime = RtlConvertLongToLargeInteger(-10000000);
// 啟動定時器
KeSetTimer(&pDevExt->timer, pDevExt->liDueTime, &pDevExt->dpc);

驅動層完成代碼如下所示：

#include <ntddk.h>

// 自定義介面擴展
typedef struct _DeviceExtension
{
	LIST_ENTRY IrpList;
	KTIMER timer;
	LARGE_INTEGER liDueTime;
	KDPC dpc;
}DEV_EXT, *PDEV_EXT;

// 默認派遣函式
NTSTATUS _DefaultDispatch(PDEVICE_OBJECT _pDeviceObject, PIRP _pIrp)
{
	_pIrp->IoStatus.Status = STATUS_NOT_SUPPORTED;
	_pIrp->IoStatus.Information = 0;
	IoCompleteRequest(_pIrp, IO_NO_INCREMENT);
	return _pIrp->IoStatus.Status;
}

// 創建派遣函式
NTSTATUS _AsyncCreateCloseDispatch(PDEVICE_OBJECT _pDevcieObject, PIRP _pIrp)
{
	_pIrp->IoStatus.Status = STATUS_SUCCESS;
	_pIrp->IoStatus.Information = 0;
	IoCompleteRequest(_pIrp, IO_NO_INCREMENT);
	return  _pIrp->IoStatus.Status;
}

// 讀取派遣函式
NTSTATUS _AsyncReadDispatch(PDEVICE_OBJECT _pDeviceObject, PIRP _pIrp)
{
	NTSTATUS status;
	PIO_STACK_LOCATION pIrpStack = IoGetCurrentIrpStackLocation(_pIrp);
	PDEV_EXT pDevExt = (PDEV_EXT)_pDeviceObject->DeviceExtension;

	IoMarkIrpPending(_pIrp);

	// 將IRP插入自定義鏈表中插入的是ListEntry
	InsertTailList(&pDevExt->IrpList, &_pIrp->Tail.Overlay.ListEntry);

	// 回傳pending 主要回傳給I/O管理器的值必須和IRP的Pending標志位一致
	// By: LyShark.com
	// 即呼叫iomarkirppending和回傳值要一致 
	return STATUS_PENDING;
}

// DPC執行緒
VOID _CustomDpc(PKDPC Dpc, PVOID DeferredContext, PVOID SystemArgument1, PVOID SystemArgument2)
{
	PIRP pIrp;
	PDEV_EXT pDevExt = (PDEV_EXT)DeferredContext;
	PVOID pBuffer = NULL;
	ULONG uBufferLen = 0;
	PIO_STACK_LOCATION pIrpStack = NULL;

	do
	{
		if (!pDevExt)
		{
			break;
		}

		// 檢查尾端IRP鏈表是否為空 為空則跳出
		if (IsListEmpty(&pDevExt->IrpList))
		{
			break;
		}

		// 從IRP鏈表中取出一個IRP并完成該IRP 取出的是ListEntry的地址
		PLIST_ENTRY pListEntry = (PLIST_ENTRY)RemoveHeadList(&pDevExt->IrpList);
		if (!pListEntry)
			break;

		pIrp = (PIRP)CONTAINING_RECORD(pListEntry, IRP, Tail.Overlay.ListEntry);
		pIrpStack = IoGetCurrentIrpStackLocation(pIrp);

		DbgPrint("當前DPC Irp: 0x%x\n", pIrp);

		// 驅動程式的讀寫方式位直接I/O
		pBuffer = MmGetSystemAddressForMdl(pIrp->MdlAddress);
		if (pBuffer == NULL)
		{
			pIrp->IoStatus.Status = STATUS_UNSUCCESSFUL;
			pIrp->IoStatus.Information = 0;
			IoCompleteRequest(pIrp, IO_NO_INCREMENT);

			break;
		}
		uBufferLen = pIrpStack->Parameters.Read.Length;
		DbgPrint("讀取DPC長度: %d\n", uBufferLen);

		// 支持5位元組以下的讀請求
		uBufferLen = uBufferLen > 13 ? 13 : uBufferLen;

		// 復制請求內容
		RtlCopyMemory(pBuffer, "hello lyshark", uBufferLen);

		pIrp->IoStatus.Status = STATUS_SUCCESS;
		pIrp->IoStatus.Information = uBufferLen;

		// 完成該IRP
		IoCompleteRequest(pIrp, IO_NO_INCREMENT);
	} while (FALSE);

	// 重新設定定時器
	KeSetTimer(&pDevExt->timer, pDevExt->liDueTime, &pDevExt->dpc);
}

// 卸載驅動
VOID _UnloadDispatch(PDRIVER_OBJECT _pDriverObject)
{
	UNICODE_STRING Win32DeviceName;
	PDEV_EXT pDevExt = (PDEV_EXT)_pDriverObject->DeviceObject->DeviceExtension;

	RtlInitUnicodeString(&Win32DeviceName, L"\\DosDevices\\LySharkAsync");

	// 洗掉定時器
	// LyShark
	KeCancelTimer(&pDevExt->timer);
	// 洗掉創建的設備
	IoDeleteDevice(_pDriverObject->DeviceObject);
}

// 驅動入口
NTSTATUS DriverEntry(PDRIVER_OBJECT _pDriverObject, PUNICODE_STRING _pRegistryPath)
{
	UNICODE_STRING DeviceName, Win32DeivceName;
	PDEVICE_OBJECT pDeviceObject = NULL;
	NTSTATUS status;
	PDEV_EXT pDevExt = NULL;
	HANDLE hThread;
	OBJECT_ATTRIBUTES ObjectAttributes;
	CLIENT_ID CID;

	RtlInitUnicodeString(&DeviceName, L"\\Device\\LySharkAsync");
	RtlInitUnicodeString(&Win32DeivceName, L"\\DosDevices\\LySharkAsync");

	for (ULONG i = 0; i <= IRP_MJ_MAXIMUM_FUNCTION; i++)
	{
		_pDriverObject->MajorFunction[i] = _DefaultDispatch;
	}

	_pDriverObject->MajorFunction[IRP_MJ_CREATE] = _AsyncCreateCloseDispatch;
	_pDriverObject->MajorFunction[IRP_MJ_CLOSE] = _AsyncCreateCloseDispatch;
	_pDriverObject->MajorFunction[IRP_MJ_READ] = _AsyncReadDispatch;
	_pDriverObject->DriverUnload = _UnloadDispatch;

	// 分配自定義擴展
	status = IoCreateDevice(_pDriverObject, sizeof(DEV_EXT), &DeviceName, FILE_DEVICE_UNKNOWN, 0, FALSE, &pDeviceObject);
	if (!NT_SUCCESS(status))
		return status;
	if (!pDeviceObject)
		return STATUS_UNEXPECTED_IO_ERROR;

	pDeviceObject->Flags |= DO_DIRECT_IO;
	pDeviceObject->AlignmentRequirement = FILE_WORD_ALIGNMENT;
	status = IoCreateSymbolicLink(&Win32DeivceName, &DeviceName);

	pDeviceObject->Flags &= ~DO_DEVICE_INITIALIZING;
	pDevExt = (PDEV_EXT)pDeviceObject->DeviceExtension;

	// 初始化IRP鏈表
	InitializeListHead(&pDevExt->IrpList);
	// 初始化定時器
	KeInitializeTimer(&(pDevExt->timer));
	// 初始化DPC pDevExt是傳給_CustomDpc函式的引數
	KeInitializeDpc(&pDevExt->dpc, (PKDEFERRED_ROUTINE)_CustomDpc, pDevExt);

	// 設定定時時間位1s
	pDevExt->liDueTime = RtlConvertLongToLargeInteger(-10000000);
	// 啟動定時器
	KeSetTimer(&pDevExt->timer, pDevExt->liDueTime, &pDevExt->dpc);

	return STATUS_SUCCESS;
}

驅動層說完了，接下來是應用層，對于應用層來說，需要使用CreateEvent打開通知事件，或者叫做事件物件，然后當有通知時，則直接使用ReadFile讀取對應的緩沖區，當所有讀取全部結束WaitForMultipleObjects等待結束即輸出結果，

#include <stdio.h>
#include <Windows.h>

int main(int argc, char *argv[])
{
	HANDLE hFile;
	char Buffer[3][32] = { 0 };
	DWORD dwRet[3] = { 0 };
	OVERLAPPED ol[3] = { 0 };
	HANDLE hEvent[3] = { 0 };

	// By:LyShark
	hFile = CreateFileA("\\\\.\\LySharkAsync", GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING,
		FILE_ATTRIBUTE_NORMAL | FILE_FLAG_OVERLAPPED,
		NULL);
	if (INVALID_HANDLE_VALUE =https://www.cnblogs.com/LyShark/archive/2022/10/03/= hFile)
		return  0;

	// event用來通知請求完成
	hEvent[0] = CreateEvent(NULL, TRUE, FALSE, NULL);
	ol[0].hEvent = hEvent[0];

	hEvent[1] = CreateEvent(NULL, TRUE, FALSE, NULL);
	ol[1].hEvent = hEvent[1];

	hEvent[2] = CreateEvent(NULL, TRUE, FALSE, NULL);
	ol[2].hEvent = hEvent[2];

	// 讀取事件內容到快取
	ReadFile(hFile, Buffer[0], 13, &dwRet[0], &ol[0]);
	ReadFile(hFile, Buffer[1], 13, &dwRet[1], &ol[1]);
	ReadFile(hFile, Buffer[2], 13, &dwRet[2], &ol[2]);

	// 等待三個事件執行完畢
	WaitForMultipleObjects(3, hEvent, TRUE, INFINITE);

	// 輸出結果
	printf("快取LyShark A: %s \n", Buffer[0]);
	printf("快取LyShark B: %s \n", Buffer[1]);
	printf("快取LyShark C: %s \n", Buffer[2]);

	CloseHandle(hFile);
	return  0;
}

這段代碼最終運行效果如下：

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