驱动开发：内核封装WFP防火墙入门

发表于 2023-06-02 更新于 2023-07-04 分类于《Windows 内核安全编程技术实践》

WFP框架是微软推出来替代TDIHOOK传输层驱动接口网络通信的方案，其默认被设计为分层结构，该框架分别提供了用户态与内核态相同的AIP函数，在两种模式下均可以开发防火墙产品，WFP 框架分为两大层次模块,用户态基础过滤引擎`BFE (BaseFilteringEngine)` ,以及内核态过滤引擎 `KMFE (KMFilteringEngine)`,基础过滤引擎对上提供C语言调用方式的API以及RPC接口,这些接口都被封装在`FWPUCLNT.dll`模块中,开发时可以调用该模块中的导出函数.

WFP框架是微软推出来替代TDIHOOK传输层驱动接口网络通信的方案，其默认被设计为分层结构，该框架分别提供了用户态与内核态相同的AIP函数，在两种模式下均可以开发防火墙产品，以下代码我实现了一个简单的驱动过滤防火墙。

WFP 框架分为两大层次模块,用户态基础过滤引擎BFE (BaseFilteringEngine) ,以及内核态过滤引擎 KMFE (KMFilteringEngine),基础过滤引擎对上提供C语言调用方式的API以及RPC接口,这些接口都被封装在FWPUCLNT.dll模块中,开发时可以调用该模块中的导出函数.

WFP程序工作流程:
使用 FwpmEngineOpen() 开启 WFP 引擎,获得WFP使用句柄
使用 FwpmTransactionBegin() 设置对网络通信内容的过滤权限 (只读/允许修改)
使用 FwpsCalloutRegister(),FwpmCalloutAdd(),FwpmFilterAdd() 选择要过滤的内容,并添加过滤器对象和回调函数.
使用 FwpmTransactionCommit() 确认刚才的内容,让刚才添加的回调函数开始生效.
使用 FwpmFilterDeleteById(),FwpmCalloutDeleteById(),FwpsCalloutUnregisterById()函数撤销对象和回调函数.
使用 FwpmEngineClose() 关闭WFP引擎类句柄.

默认情况下WFP一次需要注册3个回调函数,只有一个是事前回调,另外两个是事后回调,通常情况下我们只关注事前回调即可,此外WFP能过滤很对内容,我们需要指定过滤条件标志来输出我们所需要的数据.

一般可设置为FWPM_LAYER_ALE_AUTH_CONNECT_V4意思是设置IPV4过滤.
还需要设置一个GUID值,该值可随意设置,名称为GUID_ALE_AUTH_CONNECT_CALLOUT_V4宏.

首先我们通过上方的流程实现一个简单的网络控制驱动，该驱动运行后可对自身机器访问指定地址端口进行控制，例如实现指定应用断网，禁止指定页面被访问等，在配置WFP开发环境时需要在链接器选项卡中的附加依赖项中增加fwpkclnt.lib，uuid.lib这两个库文件，并且需要使用WDM开发模板，否则编译将不通过。

#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>

// 过滤器引擎句柄
HANDLE g_hEngine;

// 过滤器引擎中的callout的运行时标识符
ULONG32 g_AleConnectCalloutId;

// 过滤器的运行时标识符
ULONG64 g_AleConnectFilterId;

// 指定唯一UUID值(只要不冲突即可,内容可随意)
GUID GUID_ALE_AUTH_CONNECT_CALLOUT_V4 = { 0x6812fc83, 0x7d3e, 0x499a, 0xa0, 0x12, 0x55, 0xe0, 0xd8, 0x5f, 0x34, 0x8b };

// ------------------------------------------------------------------------------
// 头部函数声明
// ------------------------------------------------------------------------------

// 注册Callout并设置过滤点
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);

// 注册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);

// 设置过滤点
NTSTATUS SetFilter(
	IN const GUID *layerKey,
	IN const GUID *calloutKey,
	OUT ULONG64 *filterId,
	OUT HANDLE *engine);

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

// Callout函数 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函数 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

// ------------------------------------------------------------------------------
// 函数实现部分
// ------------------------------------------------------------------------------

// 协议判断
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;
}

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

	// 注册Callout并设置过滤点
	// classifyFn, notifyFn, flowDeleteFn 注册三个回调函数,一个事前回调,两个事后回调
	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("注册回调失败 \n");
		return status;
	}

	return status;
}

// 卸载WFP
NTSTATUS WfpUnload()
{
	if (NULL != g_hEngine)
	{
		// 删除FilterId
		FwpmFilterDeleteById(g_hEngine, g_AleConnectFilterId);
		// 删除CalloutId
		FwpmCalloutDeleteById(g_hEngine, g_AleConnectCalloutId);
		// 清空Filter
		g_AleConnectFilterId = 0;
		// 反注册CalloutId
		FwpsCalloutUnregisterById(g_AleConnectCalloutId);
		// 清空CalloutId
		g_AleConnectCalloutId = 0;
		// 关闭引擎
		FwpmEngineClose(g_hEngine);
		g_hEngine = NULL;
	}

	return STATUS_SUCCESS;
}

// 注册Callout并设置过滤点
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;

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

	// 设置过滤点
	status = SetFilter(layerKey, calloutKey, filterId, engine);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

	return status;
}

// 注册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 };

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

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

	return status;
}

// 设置过滤点
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 };

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

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

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

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

	// 设置过滤器参数
	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;

	// 添加过滤器
	status = FwpmFilterAdd(hEngine, &mFilter, NULL, filterId);
	if (!NT_SUCCESS(status))
	{
		return status;
	}

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

	*engine = hEngine;
	return status;
}

// Callout函数 classifyFn 事前回调函数
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)
{
	// 数据包的方向,取值 FWP_DIRECTION_INBOUND = 1 或 FWP_DIRECTION_OUTBOUND = 0
	WORD wDirection = inFixedValues->incomingValue[FWPS_FIELD_ALE_FLOW_ESTABLISHED_V4_DIRECTION].value.int8;

	// 定义本机地址与本机端口
	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;

	// 定义对端地址与对端端口
	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;

	// 获取当前进程IRQ
	KIRQL kCurrentIrql = KeGetCurrentIrql();

	// 获取进程ID
	ULONG64 processId = inMetaValues->processId;
	UCHAR szProcessPath[256] = { 0 };
	CHAR szProtocalName[256] = { 0 };
	RtlZeroMemory(szProcessPath, 256);

	// 获取进程路径
	for (ULONG i = 0; i < inMetaValues->processPath->size; i++)
	{
		// 里面是宽字符存储的
		szProcessPath[i] = inMetaValues->processPath->data[i];
	}

	// 获取当前协议类型
	ProtocalIdToName(inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_PROTOCOL].value.uint16, szProtocalName);

	// 设置默认规则 允许连接
	classifyOut->actionType = FWP_ACTION_PERMIT;

	// 禁止指定进程网络连接
	if (NULL != wcsstr((PWCHAR)szProcessPath, L"iexplore.exe"))
	{
		// 设置拒绝规则 拒绝连接
		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] 拦截IE网络链接请求... \n");
	}

	// 输出对端地址字符串 并阻断链接
	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 --> 对端: %s : %s \n", szLocalAddress, szLocalPort, szRemoteAddress, szRemotePort);

	// 如果对端地址是 8.141.58.64 且对端端口是 443 则拒绝连接
	if (strcmp(szRemoteAddress, "8.141.58.64") == 0 && strcmp(szRemotePort, "443") == 0)
	{
		DbgPrint("[LyShark.com] 拦截网站访问请求 --> %s : %s \n", szRemoteAddress, szRemotePort);
		// 设置拒绝规则 拒绝连接
		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] 拦截Ping访问请求 --> %s \n", szRemoteAddress);

		// 设置拒绝规则 拒绝连接
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}

	// 显示
	DbgPrint("[LyShark.com] 方向: %d -> 协议类型: %s -> 本端地址: %u.%u.%u.%u:%d -> 对端地址: %u.%u.%u.%u:%d -> IRQL: %d -> 进程ID: %I64d -> 路径: %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函数 notifyFn 事后回调函数
NTSTATUS NTAPI notifyFn(_In_ FWPS_CALLOUT_NOTIFY_TYPE notifyType, _In_ const GUID* filterKey, _Inout_ FWPS_FILTER2* filter)
{
	NTSTATUS status = STATUS_SUCCESS;
	return status;
}

// Callout函数 flowDeleteFn 事后回调函数
VOID NTAPI flowDeleteFn(_In_ UINT16 layerId, _In_ UINT32 calloutId, _In_ UINT64 flowContext)
{
	return;
}

// 默认派遣函数
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;
}

// 创建设备
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;
}

// 卸载驱动
VOID UnDriver(PDRIVER_OBJECT driver)
{
	// 删除回调函数和过滤器,关闭引擎
	WfpUnload();

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

// 驱动入口
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;
	}

	// 创建设备
	CreateDevice(Driver);

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

	Driver->DriverUnload = UnDriver;
	return STATUS_SUCCESS;
}

上方代码是一个最基本的WFP过滤框架头部函数，声明部分来源于微软的定义此处不做解释，需要注意GUID_ALE_AUTH_CONNECT_CALLOUT_V4代表的是一个随机UUID值，该值可以任意定义只要不一致即可，驱动程序运行后会率先执行WfpLoad()这个函数，该函数内部通过RegisterCalloutForLayer()注册了一个过滤点，此处我们必须要注意三个回调函数，classifyFn, notifyFn, flowDeleteFn 他们分别的功能时，事前回调，事后回调，事后回调，而WFP框架中我们最需要注意的也就是对这三个函数进行重定义，也就是需要重写函数来实现我们特定的功能。

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
}

既然是防火墙那么必然classifyFn事前更重要一些，如果需要监控网络流量则需要在事前函数中做处理，而如果是监视则可以在事后做处理，既然要在事前进行处理，那么我们就来看看事前是如何处理的流量。

// Callout函数 classifyFn 事前回调函数
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)
{
	// 数据包的方向,取值 FWP_DIRECTION_INBOUND = 1 或 FWP_DIRECTION_OUTBOUND = 0
	WORD wDirection = inFixedValues->incomingValue[FWPS_FIELD_ALE_FLOW_ESTABLISHED_V4_DIRECTION].value.int8;

	// 定义本机地址与本机端口
	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;

	// 定义对端地址与对端端口
	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;

	// 获取当前进程IRQ
	KIRQL kCurrentIrql = KeGetCurrentIrql();

	// 获取进程ID
	ULONG64 processId = inMetaValues->processId;
	UCHAR szProcessPath[256] = { 0 };
	CHAR szProtocalName[256] = { 0 };
	RtlZeroMemory(szProcessPath, 256);

	// 获取进程路径
	for (ULONG i = 0; i < inMetaValues->processPath->size; i++)
	{
		// 里面是宽字符存储的
		szProcessPath[i] = inMetaValues->processPath->data[i];
	}

	// 获取当前协议类型
	ProtocalIdToName(inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_PROTOCOL].value.uint16, szProtocalName);

	// 设置默认规则 允许连接
	classifyOut->actionType = FWP_ACTION_PERMIT;

	// 禁止指定进程网络连接
	if (NULL != wcsstr((PWCHAR)szProcessPath, L"qq.exe"))
	{
		// 设置拒绝规则 拒绝连接
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}

	// 输出对端地址字符串 并阻断链接
	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 --> 对端: %s : %s \n", szLocalAddress, szLocalPort, szRemoteAddress, szRemotePort);

	// 如果对端地址是 8.141.58.64 且对端端口是 443 则拒绝连接
	if (strcmp(szRemoteAddress, "8.141.58.64") == 0 && strcmp(szRemotePort, "443") == 0)
	{
		DbgPrint("拦截网站访问请求 --> %s : %s \n", szRemoteAddress, szRemotePort);
		// 设置拒绝规则 拒绝连接
		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("拦截Ping访问请求 --> %s \n", szRemoteAddress);

		// 设置拒绝规则 拒绝连接
		classifyOut->actionType = FWP_ACTION_BLOCK;
		classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
		classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
	}

	/*
	// 显示
	DbgPrint("方向: %d -> 协议类型: %s -> 本端地址: %u.%u.%u.%u:%d -> 对端地址: %u.%u.%u.%u:%d -> IRQL: %d -> 进程ID: %I64d -> 路径: %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);
	*/
}

当有新的网络数据包路由到事前函数时，程序中会通过如下案例直接得到我们所需要的数据包头，ProtocalIdToName函数则是一个将特定类型数字转为字符串的转换函数。

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

// 定义本机地址与本机端口
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;

// 定义对端地址与对端端口
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;

// 获取当前进程IRQ
KIRQL kCurrentIrql = KeGetCurrentIrql();

// 获取进程ID
ULONG64 processId = inMetaValues->processId;
UCHAR szProcessPath[256] = { 0 };
CHAR szProtocalName[256] = { 0 };
RtlZeroMemory(szProcessPath, 256);

// 获取进程路径
for (ULONG i = 0; i < inMetaValues->processPath->size; i++)
{
	// 里面是宽字符存储的
	szProcessPath[i] = inMetaValues->processPath->data[i];
}

// 获取当前协议类型
ProtocalIdToName(inFixedValues->incomingValue[FWPS_FIELD_ALE_AUTH_CONNECT_V4_IP_PROTOCOL].value.uint16, szProtocalName);

拦截浏览器上网

防火墙的默认规则我们将其改为放行所有classifyOut->actionType = FWP_ACTION_PERMIT;，当我们需要拦截特定进程上网时则只需要判断调用原，如果时特定进程则直接设置拒绝网络访问。

// 设置默认规则 允许连接
classifyOut->actionType = FWP_ACTION_PERMIT;

// 禁止指定进程网络连接
if (NULL != wcsstr((PWCHAR)szProcessPath, L"iexplore.exe"))
{
	// 设置拒绝规则 拒绝连接
	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] 拦截IE网络链接请求... \n");
}

当这段驱动程序被加载后，则用户使用IE访问任何页面都将提示无法访问。

拦截指定IP地址

防火墙的另一个重要功能就是拦截主机自身访问特定网段，此功能只需要增加过滤条件即可实现，如下当用户访问8.141.58.64这个IP地址是则会被拦截，如果监测到用户时Ping请求则也会被拦截。

// 如果对端地址是 8.141.58.64 且对端端口是 443 则拒绝连接
if (strcmp(szRemoteAddress, "8.141.58.64") == 0 && strcmp(szRemotePort, "443") == 0)
{
	DbgPrint("拦截网站访问请求 --> %s : %s \n", szRemoteAddress, szRemotePort);
	// 设置拒绝规则 拒绝连接
	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("拦截Ping访问请求 --> %s \n", szRemoteAddress);

	// 设置拒绝规则 拒绝连接
	classifyOut->actionType = FWP_ACTION_BLOCK;
	classifyOut->rights = classifyOut->rights & (~FWPS_RIGHT_ACTION_WRITE);
	classifyOut->flags = classifyOut->flags | FWPS_CLASSIFY_OUT_FLAG_ABSORB;
}

当这段驱动程序被加载后，则用户主机无法访问8.141.58.64且无法使用ping命令。

抓取底层数据包

如果仅仅只是想要输出流经自身主机的数据包，则只需要对特定数据包进行解码即可得到原始数据。

// 输出对端地址字符串 并阻断链接
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);

// 显示
DbgPrint("[LyShark.com] 方向: %d -> 协议类型: %s -> 本端地址: %u.%u.%u.%u:%d -> 对端地址: %u.%u.%u.%u:%d -> IRQL: %d -> 进程ID: %I64d -> 路径: %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);

当这段驱动程序被加载后，则用户可看到流经本机的所有数据包。