驅動開發：核心封裝WFP防火牆入門

WFP框架是微軟推出來替代TDIHOOK傳輸層驅動介面網路通訊的方案，其預設被設計為分層結構，該框架分別提供了使用者態與核心態相同的AIP函數，在兩種模式下均可以開發防火牆產品，以下程式碼我實現了一個簡單的驅動過濾防火牆。

WFP 框架分為兩大層次模組,使用者態基礎過濾引擎BFE (BaseFilteringEngine) ,以及核心態過濾引擎 KMFE (KMFilteringEngine),基礎過濾引擎對上提供C語言呼叫方式的API以及RPC介面,這些介面都被封裝在FWPUCLNT.dll模組中,開發時可以呼叫該模組中的匯出函數.

• WFP程式工作流程:
• 使用 FwpmEngineOpen() 開啟 WFP 引擎,獲得WFP使用控制程式碼
• 使用 FwpmTransactionBegin() 設定對網路通訊內容的過濾許可權 (唯讀/允許修改)
• 使用 FwpsCalloutRegister(),FwpmCalloutAdd(),FwpmFilterAdd() 選擇要過濾的內容,並新增過濾器物件和回撥函數.
• 使用 FwpmTransactionCommit() 確認剛才的內容,讓剛才新增的回撥函數開始生效.
• 使用 FwpmFilterDeleteById(),FwpmCalloutDeleteById(),FwpsCalloutUnregisterById()函數復原物件和回撥函數.
• 使用 FwpmEngineClose() 關閉WFP引擎類控制程式碼.

預設情況下WFP一次需要註冊3個回撥函數,只有一個是事前回撥,另外兩個是事後回撥,通常情況下我們只關注事前回撥即可,此外WFP能過濾很對內容,我們需要指定過濾條件標誌來輸出我們所需要的資料.

• 一般可設定為FWPM_LAYER_ALE_AUTH_CONNECT_V4意思是設定IPV4過濾.
• 還需要設定一個GUID值,該值可隨意設定,名稱為GUID_ALE_AUTH_CONNECT_CALLOUT_V4宏.

首先我們通過上方的流程實現一個簡單的網路控制驅動，該驅動執行後可對自身機器存取指定地址埠進行控制，例如實現指定應用斷網，禁止指定頁面被存取等，在設定WFP開發環境時需要在連結器索引標籤中的附加依賴項中增加fwpkclnt.lib，uuid.lib這兩個庫檔案，並且需要使用WDM開發模板，否則編譯將不通過。

// 署名權
// right to sign one's name on a piece of work
// PowerBy: LyShark
// Email: [email protected]

#define NDIS_SUPPORT_NDIS6 1
#define DEV_NAME L"\\Device\\MY_WFP_DEV_NAME"
#define SYM_NAME L"\\DosDevices\\MY_WFP_SYM_NAME"

#include <ntifs.h>
#include <fwpsk.h>
#include <fwpmk.h>
#include <stdio.h>

// 過濾器引擎控制程式碼
HANDLE g_hEngine;

// 過濾器引擎中的callout的執行時識別符號
ULONG32 g_AleConnectCalloutId;

// 過濾器的執行時識別符號
ULONG64 g_AleConnectFilterId;

// 指定唯一UUID值(只要不衝突即可,內容可隨意)
GUID GUID_ALE_AUTH_CONNECT_CALLOUT_V4 = { 0x6812fc83, 0x7d3e, 0x499a, 0xa0, 0x12, 0x55, 0xe0, 0xd8, 0x5f, 0x34, 0x8b };

// ------------------------------------------------------------------------------
// 頭部函數宣告
// ------------------------------------------------------------------------------

// 註冊Callout並設定過濾點
NTSTATUS RegisterCalloutForLayer(
	IN PDEVICE_OBJECT pDevObj,
	IN const GUID *layerKey,
	IN const GUID *calloutKey,
	IN FWPS_CALLOUT_CLASSIFY_FN classifyFn,
	IN FWPS_CALLOUT_NOTIFY_FN notifyFn,
	IN FWPS_CALLOUT_FLOW_DELETE_NOTIFY_FN flowDeleteNotifyFn,
	OUT ULONG32 *calloutId,
	OUT ULONG64 *filterId,
	OUT HANDLE *engine);

// 註冊Callout
NTSTATUS RegisterCallout(
	PDEVICE_OBJECT pDevObj,
	IN const GUID *calloutKey,
	IN FWPS_CALLOUT_CLASSIFY_FN classifyFn,
	IN FWPS_CALLOUT_NOTIFY_FN notifyFn,
	IN FWPS_CALLOUT_FLOW_DELETE_NOTIFY_FN flowDeleteNotifyFn,
	OUT ULONG32 *calloutId);

// 設定過濾點
NTSTATUS SetFilter(
	IN const GUID *layerKey,
	IN const GUID *calloutKey,
	OUT ULONG64 *filterId,
	OUT HANDLE *engine);

// Callout函數 flowDeleteFn
VOID NTAPI flowDeleteFn(
	_In_ UINT16 layerId,
	_In_ UINT32 calloutId,
	_In_ UINT64 flowContext
	);

// Callout函數 classifyFn
#if (NTDDI_VERSION >= NTDDI_WIN8)
VOID NTAPI classifyFn(
	_In_ const FWPS_INCOMING_VALUES0* inFixedValues,
	_In_ const FWPS_INCOMING_METADATA_VALUES0* inMetaValues,
	_Inout_opt_ void* layerData,
	_In_opt_ const void* classifyContext,
	_In_ const FWPS_FILTER2* filter,
	_In_ UINT64 flowContext,
	_Inout_ FWPS_CLASSIFY_OUT0* classifyOut
	);
#elif (NTDDI_VERSION >= NTDDI_WIN7)                       
VOID NTAPI classifyFn(
	_In_ const FWPS_INCOMING_VALUES0* inFixedValues,
	_In_ const FWPS_INCOMING_METADATA_VALUES0* inMetaValues,
	_Inout_opt_ void* layerData,
	_In_opt_ const void* classifyContext,
	_In_ const FWPS_FILTER1* filter,
	_In_ UINT64 flowContext,
	_Inout_ FWPS_CLASSIFY_OUT0* classifyOut
	);
#else
VOID NTAPI classifyFn(
	_In_ const FWPS_INCOMING_VALUES0* inFixedValues,
	_In_ const FWPS_INCOMING_METADATA_VALUES0* inMetaValues,
	_Inout_opt_ void* layerData,
	_In_ const FWPS_FILTER0* filter,
	_In_ UINT64 flowContext,
	_Inout_ FWPS_CLASSIFY_OUT0* classifyOut
	);
#endif

// Callout函數 notifyFn
#if (NTDDI_VERSION >= NTDDI_WIN8)
NTSTATUS NTAPI notifyFn(
	_In_ FWPS_CALLOUT_NOTIFY_TYPE notifyType,
	_In_ const GUID* filterKey,
	_Inout_ FWPS_FILTER2* filter
	);
#elif (NTDDI_VERSION >= NTDDI_WIN7)
NTSTATUS NTAPI notifyFn(
	_In_ FWPS_CALLOUT_NOTIFY_TYPE notifyType,
	_In_ const GUID* filterKey,
	_Inout_ FWPS_FILTER1* filter
	);
#else
NTSTATUS NTAPI notifyFn(
	_In_ FWPS_CALLOUT_NOTIFY_TYPE notifyType,
	_In_ const GUID* filterKey,
	_Inout_ FWPS_FILTER0* filter
	);
#endif

// ------------------------------------------------------------------------------
// 函數實現部分
// ------------------------------------------------------------------------------

// 協定判斷
NTSTATUS ProtocalIdToName(UINT16 protocalId, PCHAR lpszProtocalName)
{
	NTSTATUS status = STATUS_SUCCESS;

	switch (protocalId)
	{
	case 1:
	{
		// ICMP
		RtlCopyMemory(lpszProtocalName, "ICMP", 5);
		break;
	}
	case 2:
	{
		// IGMP
		RtlCopyMemory(lpszProtocalName, "IGMP", 5);
		break;
	}
	case 6:
	{
		// TCP
		RtlCopyMemory(lpszProtocalName, "TCP", 4);
		break;
	}
	case 17:
	{
		// UDP
		RtlCopyMemory(lpszProtocalName, "UDP", 4);
		break;
	}
	case 27:
	{
		// RDP
		RtlCopyMemory(lpszProtocalName, "RDP", 6);
		break;
	}
	default:
	{
		// UNKNOW
		RtlCopyMemory(lpszProtocalName, "UNKNOWN", 8);
		break;
	}
	}

	return status;
}

// 啟動WFP
NTSTATUS WfpLoad(PDEVICE_OBJECT pDevObj)
{
	NTSTATUS status = STATUS_SUCCESS;

	// 註冊Callout並設定過濾點
	// classifyFn, notifyFn, flowDeleteFn 註冊三個回撥函數,一個事前回撥,兩個事後回撥
	status = RegisterCalloutForLayer(pDevObj, &FWPM_LAYER_ALE_AUTH_CONNECT_V4, &GUID_ALE_AUTH_CONNECT_CALLOUT_V4,
		classifyFn, notifyFn, flowDeleteFn, &g_AleConnectCalloutId, &g_AleConnectFilterId, &g_hEngine);
	if (!NT_SUCCESS(status))
	{
		DbgPrint("註冊回撥失敗 \n");
		return status;
	}

	return status;
}

// 解除安裝WFP
NTSTATUS WfpUnload()
{
	if (NULL != g_hEngine)
	{
		// 刪除FilterId
		FwpmFilterDeleteById(g_hEngine, g_AleConnectFilterId);
		// 刪除CalloutId
		FwpmCalloutDeleteById(g_hEngine, g_AleConnectCalloutId);
		// 清空Filter
		g_AleConnectFilterId = 0;
		// 反註冊CalloutId
		FwpsCalloutUnregisterById(g_AleConnectCalloutId);
		// 清空CalloutId
		g_AleConnectCalloutId = 0;
		// 關閉引擎
		FwpmEngineClose(g_hEngine);
		g_hEngine = NULL;
	}

	return STATUS_SUCCESS;
}

// 註冊Callout並設定過濾點
NTSTATUS RegisterCalloutForLayer(IN PDEVICE_OBJECT pDevObj, IN const GUID *layerKey, IN const GUID *calloutKey, IN FWPS_CALLOUT_CLASSIFY_FN classifyFn, IN FWPS_CALLOUT_NOTIFY_FN notifyFn, IN FWPS_CALLOUT_FLOW_DELETE_NOTIFY_FN flowDeleteNotifyFn, OUT ULONG32 *calloutId, OUT ULONG64 *filterId, OUT HANDLE *engine)
{
	NTSTATUS status = STATUS_SUCCESS;

	// 註冊Callout
	status = RegisterCallout(pDevObj, calloutKey, classifyFn, notifyFn, flowDeleteNotifyFn, calloutId);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	// 設定過濾點
	status = SetFilter(layerKey, calloutKey, filterId, engine);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	return status;
}

// 註冊Callout
NTSTATUS RegisterCallout(PDEVICE_OBJECT pDevObj, IN const GUID *calloutKey, IN FWPS_CALLOUT_CLASSIFY_FN classifyFn, IN FWPS_CALLOUT_NOTIFY_FN notifyFn, IN FWPS_CALLOUT_FLOW_DELETE_NOTIFY_FN flowDeleteNotifyFn, OUT ULONG32 *calloutId)
{
	NTSTATUS status = STATUS_SUCCESS;
	FWPS_CALLOUT sCallout = { 0 };

	// 設定Callout
	sCallout.calloutKey = *calloutKey;
	sCallout.classifyFn = classifyFn;
	sCallout.flowDeleteFn = flowDeleteNotifyFn;
	sCallout.notifyFn = notifyFn;

	// 註冊Callout
	status = FwpsCalloutRegister(pDevObj, &sCallout, calloutId);
	if (!NT_SUCCESS(status))
	{
		DbgPrint("註冊Callout失敗 \n");
		return status;
	}

	return status;
}

// 設定過濾點
NTSTATUS SetFilter(IN const GUID *layerKey, IN const GUID *calloutKey, OUT ULONG64 *filterId, OUT HANDLE *engine)
{
	HANDLE hEngine = NULL;
	NTSTATUS status = STATUS_SUCCESS;
	FWPM_SESSION session = { 0 };
	FWPM_FILTER mFilter = { 0 };
	FWPM_CALLOUT mCallout = { 0 };
	FWPM_DISPLAY_DATA mDispData = { 0 };

	// 建立Session
	session.flags = FWPM_SESSION_FLAG_DYNAMIC;
	status = FwpmEngineOpen(NULL, RPC_C_AUTHN_WINNT, NULL, &session, &hEngine);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	// 開始事務
	status = FwpmTransactionBegin(hEngine, 0);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	// 設定Callout引數
	mDispData.name = L"MY WFP LyShark";
	mDispData.description = L"WORLD OF DEMON";
	mCallout.applicableLayer = *layerKey;
	mCallout.calloutKey = *calloutKey;
	mCallout.displayData = mDispData;

	// 新增Callout到Session中
	status = FwpmCalloutAdd(hEngine, &mCallout, NULL, NULL);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	// 設定過濾器引數
	mFilter.action.calloutKey = *calloutKey;
	mFilter.action.type = FWP_ACTION_CALLOUT_TERMINATING;
	mFilter.displayData.name = L"MY WFP LyShark";
	mFilter.displayData.description = L"WORLD OF DEMON";
	mFilter.layerKey = *layerKey;
	mFilter.subLayerKey = FWPM_SUBLAYER_UNIVERSAL;
	mFilter.weight.type = FWP_EMPTY;

	// 新增過濾器
	status = FwpmFilterAdd(hEngine, &mFilter, NULL, filterId);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	// 提交事務
	status = FwpmTransactionCommit(hEngine);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	*engine = hEngine;
	return status;
}

// Callout函數 classifyFn 事前回撥函數
VOID NTAPI classifyFn(_In_ const FWPS_INCOMING_VALUES0* inFixedValues, _In_ const FWPS_INCOMING_METADATA_VALUES0* inMetaValues, _Inout_opt_ void* layerData, _In_opt_ const void* classifyContext, _In_ const FWPS_FILTER2* filter, _In_ UINT64 flowContext, _Inout_ FWPS_CLASSIFY_OUT0* classifyOut)
{
	// 封包的方向,取值 FWP_DIRECTION_INBOUND = 1 或 FWP_DIRECTION_OUTBOUND = 0
	WORD wDirection = inFixedValues->incomingValue[FWPS_FIELD_ALE_FLOW_ESTABLISHED_V4_DIRECTION].value.int8;

	// 定義本機地址與本機埠
	ULONG ulLocalIp = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_LOCAL_ADDRESS].value.uint32;
	UINT16 uLocalPort = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_LOCAL_PORT].value.uint16;

	// 定義對端地址與對端埠
	ULONG ulRemoteIp = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_REMOTE_ADDRESS].value.uint32;
	UINT16 uRemotePort = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_REMOTE_PORT].value.uint16;

	// 獲取當前程序IRQ
	KIRQL kCurrentIrql = KeGetCurrentIrql();

	// 獲取程序ID
	ULONG64 processId = inMetaValues->processId;
	UCHAR szProcessPath[256] = { 0 };
	CHAR szProtocalName[256] = { 0 };
	RtlZeroMemory(szProcessPath, 256);

	// 獲取程序路徑
	for (ULONG i = 0; i < inMetaValues->processPath->size; i++)
	{
		// 裡面是寬字元儲存的
		szProcessPath[i] = inMetaValues->processPath->data[i];
	}

	// 獲取當前協定型別
	ProtocalIdToName(inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_PROTOCOL].value.uint16, szProtocalName);

	// 設定預設規則 允許連線
	classifyOut->actionType = FWP_ACTION_PERMIT;

	// 禁止指定程序網路連線
	if (NULL != wcsstr((PWCHAR)szProcessPath, L"iexplore.exe"))
	{
		// 設定拒絕規則 拒絕連線
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
		DbgPrint("[LyShark.com] 攔截IE網路連結請求... \n");
	}

	// 輸出對端地址字串 並阻斷連結
	char szRemoteAddress[256] = { 0 };
	char szRemotePort[128] = { 0 };

	char szLocalAddress[256] = { 0 };
	char szLocalPort[128] = { 0 };

	sprintf(szRemoteAddress, "%u.%u.%u.%u", (ulRemoteIp >> 24) & 0xFF, (ulRemoteIp >> 16) & 0xFF, (ulRemoteIp >> 8) & 0xFF, (ulRemoteIp)& 0xFF);
	sprintf(szRemotePort, "%d", uRemotePort);

	sprintf(szLocalAddress, "%u.%u.%u.%u", (ulLocalIp >> 24) & 0xFF, (ulLocalIp >> 16) & 0xFF, (ulLocalIp >> 8) & 0xFF, (ulLocalIp)& 0xFF);
	sprintf(szLocalPort, "%d", uLocalPort);

	// DbgPrint("本端: %s : %s --> 對端: %s : %s \n", szLocalAddress, szLocalPort, szRemoteAddress, szRemotePort);

	// 如果對端地址是 8.141.58.64 且對端埠是 443 則拒絕連線
	if (strcmp(szRemoteAddress, "8.141.58.64") == 0 && strcmp(szRemotePort, "443") == 0)
	{
		DbgPrint("[LyShark.com] 攔截網站存取請求 --> %s : %s \n", szRemoteAddress, szRemotePort);
		// 設定拒絕規則 拒絕連線
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}
	else if (strcmp(szRemotePort, "0") == 0)
	{
		DbgPrint("[LyShark.com] 攔截Ping存取請求 --> %s \n", szRemoteAddress);

		// 設定拒絕規則 拒絕連線
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}

	// 顯示
	DbgPrint("[LyShark.com] 方向: %d -> 協定型別: %s -> 本端地址: %u.%u.%u.%u:%d -> 對端地址: %u.%u.%u.%u:%d -> IRQL: %d -> 程序ID: %I64d -> 路徑: %S \n",
	wDirection,
	szProtocalName,
	(ulLocalIp >> 24) & 0xFF,
	(ulLocalIp >> 16) & 0xFF,
	(ulLocalIp >> 8) & 0xFF,
	(ulLocalIp)& 0xFF,
	uLocalPort,
	(ulRemoteIp >> 24) & 0xFF,
	(ulRemoteIp >> 16) & 0xFF,
	(ulRemoteIp >> 8) & 0xFF,
	(ulRemoteIp)& 0xFF,
	uRemotePort,
	kCurrentIrql,
	processId,
	(PWCHAR)szProcessPath);

}

// Callout函數 notifyFn 事後回撥函數
NTSTATUS NTAPI notifyFn(_In_ FWPS_CALLOUT_NOTIFY_TYPE notifyType, _In_ const GUID* filterKey, _Inout_ FWPS_FILTER2* filter)
{
	NTSTATUS status = STATUS_SUCCESS;
	return status;
}

// Callout函數 flowDeleteFn 事後回撥函數
VOID NTAPI flowDeleteFn(_In_ UINT16 layerId, _In_ UINT32 calloutId, _In_ UINT64 flowContext)
{
	return;
}

// 預設派遣函數
NTSTATUS DriverDefaultHandle(PDEVICE_OBJECT pDevObj, PIRP pIrp)
{
	NTSTATUS status = STATUS_SUCCESS;
	pIrp->IoStatus.Status = status;
	pIrp->IoStatus.Information = 0;
	IoCompleteRequest(pIrp, IO_NO_INCREMENT);

	return status;
}

// 建立裝置
NTSTATUS CreateDevice(PDRIVER_OBJECT pDriverObject)
{
	NTSTATUS status = STATUS_SUCCESS;
	PDEVICE_OBJECT pDevObj = NULL;
	UNICODE_STRING ustrDevName, ustrSymName;
	RtlInitUnicodeString(&ustrDevName, DEV_NAME);
	RtlInitUnicodeString(&ustrSymName, SYM_NAME);

	status = IoCreateDevice(pDriverObject, 0, &ustrDevName, FILE_DEVICE_NETWORK, 0, FALSE, &pDevObj);
	if (!NT_SUCCESS(status))
	{
		return status;
	}
	status = IoCreateSymbolicLink(&ustrSymName, &ustrDevName);
	if (!NT_SUCCESS(status))
	{
		return status;
	}
	return status;
}

// 解除安裝驅動
VOID UnDriver(PDRIVER_OBJECT driver)
{
	// 刪除回撥函數和過濾器,關閉引擎
	WfpUnload();

	UNICODE_STRING ustrSymName;
	RtlInitUnicodeString(&ustrSymName, SYM_NAME);
	IoDeleteSymbolicLink(&ustrSymName);
	if (driver->DeviceObject)
	{
		IoDeleteDevice(driver->DeviceObject);
	}
}

// 驅動入口
NTSTATUS DriverEntry(IN PDRIVER_OBJECT Driver, PUNICODE_STRING RegistryPath)
{
	NTSTATUS status = STATUS_SUCCESS;
	Driver->DriverUnload = UnDriver;
	for (ULONG i = 0; i < IRP_MJ_MAXIMUM_FUNCTION; i++)
	{
		Driver->MajorFunction[i] = DriverDefaultHandle;
	}

	// 建立裝置
	CreateDevice(Driver);

	// 啟動WFP
	WfpLoad(Driver->DeviceObject);

	Driver->DriverUnload = UnDriver;
	return STATUS_SUCCESS;
}

上方程式碼是一個最基本的WFP過濾框架頭部函數，宣告部分來源於微軟的定義此處不做解釋，需要注意GUID_ALE_AUTH_CONNECT_CALLOUT_V4代表的是一個隨機UUID值，該值可以任意定義只要不一致即可，驅動程式執行後會率先執行WfpLoad()這個函數，該函數內部通過RegisterCalloutForLayer()註冊了一個過濾點，此處我們必須要注意三個回撥函數，classifyFn, notifyFn, flowDeleteFn 他們分別的功能時，事前回撥，事後回撥，事後回撥，而WFP框架中我們最需要注意的也就是對這三個函數進行重定義，也就是需要重寫函數來實現我們特定的功能。

NTSTATUS RegisterCalloutForLayer
(
    IN const GUID* layerKey,
    IN const GUID* calloutKey,
    IN FWPS_CALLOUT_CLASSIFY_FN classifyFn,
    IN FWPS_CALLOUT_NOTIFY_FN notifyFn,
    IN FWPS_CALLOUT_FLOW_DELETE_NOTIFY_FN flowDeleteNotifyFn,
    OUT UINT32* calloutId,
    OUT UINT64* filterId
}

既然是防火牆那麼必然classifyFn事前更重要一些，如果需要監控網路流量則需要在事前函數中做處理，而如果是監視則可以在事後做處理，既然要在事前進行處理，那麼我們就來看看事前是如何處理的流量。

// Callout函數 classifyFn 事前回撥函數
VOID NTAPI classifyFn(_In_ const FWPS_INCOMING_VALUES0* inFixedValues, _In_ const FWPS_INCOMING_METADATA_VALUES0* inMetaValues, _Inout_opt_ void* layerData, _In_opt_ const void* classifyContext, _In_ const FWPS_FILTER2* filter, _In_ UINT64 flowContext, _Inout_ FWPS_CLASSIFY_OUT0* classifyOut)
{
	// 封包的方向,取值 FWP_DIRECTION_INBOUND = 1 或 FWP_DIRECTION_OUTBOUND = 0
	WORD wDirection = inFixedValues->incomingValue[FWPS_FIELD_ALE_FLOW_ESTABLISHED_V4_DIRECTION].value.int8;

	// 定義本機地址與本機埠
	ULONG ulLocalIp = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_LOCAL_ADDRESS].value.uint32;
	UINT16 uLocalPort = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_LOCAL_PORT].value.uint16;

	// 定義對端地址與對端埠
	ULONG ulRemoteIp = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_REMOTE_ADDRESS].value.uint32;
	UINT16 uRemotePort = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_REMOTE_PORT].value.uint16;

	// 獲取當前程序IRQ
	KIRQL kCurrentIrql = KeGetCurrentIrql();

	// 獲取程序ID
	ULONG64 processId = inMetaValues->processId;
	UCHAR szProcessPath[256] = { 0 };
	CHAR szProtocalName[256] = { 0 };
	RtlZeroMemory(szProcessPath, 256);

	// 獲取程序路徑
	for (ULONG i = 0; i < inMetaValues->processPath->size; i++)
	{
		// 裡面是寬字元儲存的
		szProcessPath[i] = inMetaValues->processPath->data[i];
	}

	// 獲取當前協定型別
	ProtocalIdToName(inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_PROTOCOL].value.uint16, szProtocalName);

	// 設定預設規則 允許連線
	classifyOut->actionType = FWP_ACTION_PERMIT;

	// 禁止指定程序網路連線
	if (NULL != wcsstr((PWCHAR)szProcessPath, L"qq.exe"))
	{
		// 設定拒絕規則 拒絕連線
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}

	// 輸出對端地址字串 並阻斷連結
	char szRemoteAddress[256] = { 0 };
	char szRemotePort[128] = { 0 };

	char szLocalAddress[256] = { 0 };
	char szLocalPort[128] = { 0 };

	sprintf(szRemoteAddress, "%u.%u.%u.%u", (ulRemoteIp >> 24) & 0xFF, (ulRemoteIp >> 16) & 0xFF, (ulRemoteIp >> 8) & 0xFF, (ulRemoteIp)& 0xFF);
	sprintf(szRemotePort, "%d", uRemotePort);

	sprintf(szLocalAddress, "%u.%u.%u.%u", (ulLocalIp >> 24) & 0xFF, (ulLocalIp >> 16) & 0xFF, (ulLocalIp >> 8) & 0xFF, (ulLocalIp)& 0xFF);
	sprintf(szLocalPort, "%d", uLocalPort);

	// DbgPrint("本端: %s : %s --> 對端: %s : %s \n", szLocalAddress, szLocalPort, szRemoteAddress, szRemotePort);

	// 如果對端地址是 8.141.58.64 且對端埠是 443 則拒絕連線
	if (strcmp(szRemoteAddress, "8.141.58.64") == 0 && strcmp(szRemotePort, "443") == 0)
	{
		DbgPrint("攔截網站存取請求 --> %s : %s \n", szRemoteAddress, szRemotePort);
		// 設定拒絕規則 拒絕連線
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}
	else if (strcmp(szRemotePort, "0") == 0)
	{
		DbgPrint("攔截Ping存取請求 --> %s \n", szRemoteAddress);

		// 設定拒絕規則 拒絕連線
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}

	/*
	// 顯示
	DbgPrint("方向: %d -> 協定型別: %s -> 本端地址: %u.%u.%u.%u:%d -> 對端地址: %u.%u.%u.%u:%d -> IRQL: %d -> 程序ID: %I64d -> 路徑: %S \n",
	wDirection,
	szProtocalName,
	(ulLocalIp >> 24) & 0xFF,
	(ulLocalIp >> 16) & 0xFF,
	(ulLocalIp >> 8) & 0xFF,
	(ulLocalIp)& 0xFF,
	uLocalPort,
	(ulRemoteIp >> 24) & 0xFF,
	(ulRemoteIp >> 16) & 0xFF,
	(ulRemoteIp >> 8) & 0xFF,
	(ulRemoteIp)& 0xFF,
	uRemotePort,
	kCurrentIrql,
	processId,
	(PWCHAR)szProcessPath);
	*/
}

當有新的網路封包路由到事前函數時，程式中會通過如下案例直接得到我們所需要的封包頭，ProtocalIdToName函數則是一個將特定型別數位轉為字串的轉換函數。

// 封包的方向,取值 FWP_DIRECTION_INBOUND = 1 或 FWP_DIRECTION_OUTBOUND = 0
WORD wDirection = inFixedValues->incomingValue[FWPS_FIELD_ALE_FLOW_ESTABLISHED_V4_DIRECTION].value.int8;

// 定義本機地址與本機埠
ULONG ulLocalIp = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_LOCAL_ADDRESS].value.uint32;
UINT16 uLocalPort = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_LOCAL_PORT].value.uint16;

// 定義對端地址與對端埠
ULONG ulRemoteIp = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_REMOTE_ADDRESS].value.uint32;
UINT16 uRemotePort = inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_REMOTE_PORT].value.uint16;

// 獲取當前程序IRQ
KIRQL kCurrentIrql = KeGetCurrentIrql();

// 獲取程序ID
ULONG64 processId = inMetaValues->processId;
UCHAR szProcessPath[256] = { 0 };
CHAR szProtocalName[256] = { 0 };
RtlZeroMemory(szProcessPath, 256);

// 獲取程序路徑
for (ULONG i = 0; i < inMetaValues->processPath->size; i++)
{
	// 裡面是寬字元儲存的
	szProcessPath[i] = inMetaValues->processPath->data[i];
}

// 獲取當前協定型別
ProtocalIdToName(inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_PROTOCOL].value.uint16, szProtocalName);

攔截瀏覽器上網： 防火牆的預設規則我們將其改為放行所有classifyOut->actionType = FWP_ACTION_PERMIT;，當我們需要攔截特定程序上網時則只需要判斷呼叫原，如果時特定程序則直接設定拒絕網路存取。

// 設定預設規則 允許連線
classifyOut->actionType = FWP_ACTION_PERMIT;

// 禁止指定程序網路連線
if (NULL != wcsstr((PWCHAR)szProcessPath, L"iexplore.exe"))
{
	// 設定拒絕規則 拒絕連線
	classifyOut->actionType = FWP_ACTION_BLOCK;
	classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
	classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	DbgPrint("[LyShark.com] 攔截IE網路連結請求... \n");
}

當這段驅動程式被載入後，則使用者使用IE存取任何頁面都將提示無法存取。

攔截指定IP地址： 防火牆的另一個重要功能就是攔截主機自身存取特定網段，此功能只需要增加過濾條件即可實現，如下當用戶存取8.141.58.64這個IP地址是則會被攔截，如果監測到使用者時Ping請求則也會被攔截。

// 如果對端地址是 8.141.58.64 且對端埠是 443 則拒絕連線
if (strcmp(szRemoteAddress, "8.141.58.64") == 0 && strcmp(szRemotePort, "443") == 0)
{
	DbgPrint("攔截網站存取請求 --> %s : %s \n", szRemoteAddress, szRemotePort);
	// 設定拒絕規則 拒絕連線
	classifyOut->actionType = FWP_ACTION_BLOCK;
	classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
	classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
}
else if (strcmp(szRemotePort, "0") == 0)
{
	DbgPrint("攔截Ping存取請求 --> %s \n", szRemoteAddress);

	// 設定拒絕規則 拒絕連線
	classifyOut->actionType = FWP_ACTION_BLOCK;
	classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
	classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
}

當這段驅動程式被載入後，則使用者主機無法存取8.141.58.64且無法使用ping命令。

抓取底層封包： 如果僅僅只是想要輸出流經自身主機的封包，則只需要對特定封包進行解碼即可得到原始資料。

// 輸出對端地址字串 並阻斷連結
char szRemoteAddress[256] = { 0 };
char szRemotePort[128] = { 0 };

char szLocalAddress[256] = { 0 };
char szLocalPort[128] = { 0 };

sprintf(szRemoteAddress, "%u.%u.%u.%u", (ulRemoteIp >> 24) & 0xFF, (ulRemoteIp >> 16) & 0xFF, (ulRemoteIp >> 8) & 0xFF, (ulRemoteIp)& 0xFF);
sprintf(szRemotePort, "%d", uRemotePort);

sprintf(szLocalAddress, "%u.%u.%u.%u", (ulLocalIp >> 24) & 0xFF, (ulLocalIp >> 16) & 0xFF, (ulLocalIp >> 8) & 0xFF, (ulLocalIp)& 0xFF);
sprintf(szLocalPort, "%d", uLocalPort);

// 顯示
DbgPrint("[LyShark.com] 方向: %d -> 協定型別: %s -> 本端地址: %u.%u.%u.%u:%d -> 對端地址: %u.%u.%u.%u:%d -> IRQL: %d -> 程序ID: %I64d -> 路徑: %S \n",
wDirection,
szProtocalName,
(ulLocalIp >> 24) & 0xFF,
(ulLocalIp >> 16) & 0xFF,
(ulLocalIp >> 8) & 0xFF,
(ulLocalIp)& 0xFF,
uLocalPort,
(ulRemoteIp >> 24) & 0xFF,
(ulRemoteIp >> 16) & 0xFF,
(ulRemoteIp >> 8) & 0xFF,
(ulRemoteIp)& 0xFF,
uRemotePort,
kCurrentIrql,
processId,
(PWCHAR)szProcessPath);

當這段驅動程式被載入後，則使用者可看到流經本機的所有封包。