SSDTHook实例--编写稳定的Hook过滤函数

#ifndef _SSDT_H_
#define _SSDT_H_

#include <ntifs.h>

//内核导出的SSDT表的结构
typedef struct _SERVICE_DESCRIPTOR_TABLE {
	/*
	* Table containing cServices elements of pointers to service handler
	* functions, indexed by service ID.
	*/
	PULONG   ServiceTable;
	/*
	* Table that counts how many times each service is used. This table
	* is only updated in checked builds.
	*/
	PULONG  CounterTable;
	/*
	* Number of services contained in this table.
	*/
	ULONG   TableSize;
	/*
	* Table containing the number of bytes of parameters the handler
	* function takes.
	*/
	PUCHAR  ArgumentTable;
} SERVICE_DESCRIPTOR_TABLE, *PSERVICE_DESCRIPTOR_TABLE;

//全局变量
PMDL  pmdl_system_call;
PVOID *pdword_mapped_table;


//******************** SSDT Hook宏（固定的） ****************************************************************
//获取Hook函数的Index
#define SYSCALL_INDEX(_Function) *(PULONG)((PUCHAR)_Function+1)
//实现SSDT表的Hook
#define HOOK_SYSCALL(_Function, _Hook, _Orig )  
	_Orig = (PVOID) InterlockedExchange( (PLONG) &pdword_mapped_table[SYSCALL_INDEX(_Function)], (LONG) _Hook)
//恢复SSDT表的Hook
#define UNHOOK_SYSCALL(_Function, _Hook, _Orig )  
	InterlockedExchange( (PLONG) &pdword_mapped_table[SYSCALL_INDEX(_Function)], (LONG) _Hook)

//声明SSDT的导出 
extern PSERVICE_DESCRIPTOR_TABLE KeServiceDescriptorTable;

#endif

SSDTHook.h 头文件的编码：

#ifndef _SSDT_HOOK_H_
#define _SSDT_HOOK_H_

#include <ntifs.h>
#include "SSDT.h"  

//声明没有文档化的函数PsGetProcessImageFileName
UCHAR* PsGetProcessImageFileName(
		__in PEPROCESS Process
		); 
//*************************************************************************************************************************

//定义原函数的指针类型
typedef NTSTATUS (__stdcall *REALZWOPENPROCESS)(OUT PHANDLE ProcessHandle,
	IN ACCESS_MASK DesiredAccess,
	IN POBJECT_ATTRIBUTES ObjectAttributes,
	IN PCLIENT_ID ClientId
	);
//定义该函数指针
REALZWOPENPROCESS RealZwOpenProcess;

//保存要Hook函数的真实地址
ULONG_PTR ul_ZwOpenProcess;
//保存要Hook函数的名称
UNICODE_STRING unicode_string;


//Mdl方式的SSDT表的Hook
NTSTATUS MdlSSDTHook(ULONG_PTR ul_real_function, ULONG_PTR hook_function_addr ,ULONG_PTR *ul_save_real_function_addr);

//移除Mdl方式的SSDT表的Hook
NTSTATUS MdlRemoveSSDTHook(ULONG_PTR ul_real_function, ULONG_PTR hook_function_addr, ULONG_PTR *ul_save_real_function_addr);

#endif

SSDT.c 文件的编写

#include "SSDT.h"

//******************************************************************************************
//採用比較安全的方法改动ssdt表
//由于SSDT的虚拟地址分页属性是仅仅读的，我们不能够直接改动它，否则会产生蓝屏
//我们借助Mdl分配一段虚拟地址映射到SSDT所在的物理地址，
//同一时候由于我们映射的MDL内存属性却能够是可写，所以就能够改动ssdt，这样就替代了cr0方式。
//******************************************************************************************

//Mdl方式的SSDT表的Hook
NTSTATUS MdlSSDTHook(ULONG_PTR ul_real_function, ULONG_PTR hook_function_addr, ULONG_PTR *ul_save_real_function_addr)
{
	//构建内存描写叙述符MDL
	pmdl_system_call = MmCreateMdl(NULL, KeServiceDescriptorTable->ServiceTable, KeServiceDescriptorTable->TableSize*sizeof(ULONG_PTR));
	if(!pmdl_system_call)
	{
		return STATUS_UNSUCCESSFUL;
	}
	
	//依据MDL申请分配内存
	MmBuildMdlForNonPagedPool(pmdl_system_call);

	//设置MDL_MAPPED_TO_SYSTEM_VA标识。让这块内存变可写
	pmdl_system_call->MdlFlags = pmdl_system_call->MdlFlags | MDL_MAPPED_TO_SYSTEM_VA;

	//锁定内存
	pdword_mapped_table = MmMapLockedPages(pmdl_system_call, KernelMode);
	if (pdword_mapped_table)
	{
		//SSDT表的Hook
		HOOK_SYSCALL(ul_real_function, hook_function_addr, *ul_save_real_function_addr);
	}

	return STATUS_SUCCESS;
}


//移除Mdl方式的SSDT表的Hook
NTSTATUS MdlRemoveSSDTHook(ULONG_PTR ul_real_function, ULONG_PTR hook_function_addr, ULONG_PTR *ul_save_real_function_addr)
{
	//恢复SSDT表的Hook
	UNHOOK_SYSCALL(ul_real_function, *ul_save_real_function_addr,hook_function_addr);

	if(pmdl_system_call)
	{
		//解除内存锁定
		MmUnmapLockedPages(pdword_mapped_table, pmdl_system_call);

		//释放申请内存
		IoFreeMdl(pmdl_system_call);

		return STATUS_SUCCESS;
	}

	return STATUS_UNSUCCESSFUL;
}

SSDTHook.c 文件的编写

#include "SSDTHook.h"


//深度的字符串效验
BOOLEAN ValidateUnicodeString(PUNICODE_STRING usStr)
{
	ULONG i;

	__try
	{
		//推断字符串的内存是否可訪问
		if (!MmIsAddressValid(usStr))
		{
			return FALSE;
		}

		//推断是否为NULL
		if (usStr->Buffer == NULL || usStr->Length == 0)
		{
			return FALSE;
		}

		//每个字节都要检查
		for (i = 0; i < usStr->Length; i++)
		{
			if (!MmIsAddressValid((PUCHAR)usStr->Buffer + i))
			{
				return FALSE;
			}
		}

	}
	__except(EXCEPTION_EXECUTE_HANDLER)
	{
		//触发异常  
        return FALSE;  
	}

	return TRUE;
}

//自己定义的ZwOpenProcess函数（NewZwOpenProcess）
NTSTATUS __stdcall NewZwOpenProcess(OUT PHANDLE ProcessHandle,
	IN ACCESS_MASK DesiredAccess,
	IN POBJECT_ATTRIBUTES ObjectAttributes,
	IN PCLIENT_ID ClientId)
{
	NTSTATUS status;
	ULONG PID;
	HANDLE handle_process_handle;
	PEPROCESS eprocess_process_object;
	KPROCESSOR_MODE PreMode;

	//获取当前的系统模式MODE
	PreMode = ExGetPreviousMode();

	//*******************************假设非内核模式,就要開始检查IN的这些參数都否可读****************************

	//每Hook一个函数之前，你都要先对比WRK：
	if(PreMode != KernelMode)
	{
		__try
		{
			//这里用ProbeForRead来对參数ClientId进行測试，然后加try捕获
			//检查用户模式地址的可读性必须在ring0调用
			ProbeForRead(ClientId, sizeof(CLIENT_ID), sizeof(ULONG));
		}
		__except(EXCEPTION_EXECUTE_HANDLER)
		{
			//返回异常代码
			return GetExceptionCode();
		}
	}

	//运行到这里说明改參数是能够訪问，那我们还要效验ClientId是否为NULL
	if(ClientId != NULL && MmIsAddressValid(ClientId))
	{
		//更安全的訪问
		PID = (ULONG)ClientId->UniqueProcess;

		DbgPrint("OpenProcess %d by %s[0x%08X]
", PID, PsGetProcessImageFileName(PsGetCurrentProcess()), PsGetCurrentProcess());
	}

	/*
	typedef struct _OBJECT_ATTRIBUTES {
	ULONG           Length;
	HANDLE          RootDirectory;
	PUNICODE_STRING ObjectName; //Buffer
	ULONG           Attributes;
	PVOID           SecurityDescriptor;
	PVOID           SecurityQualityOfService;
	}  OBJECT_ATTRIBUTES, *POBJECT_ATTRIBUTES;
	*/
	if (ObjectAttributes != NULL && MmIsAddressValid(ObjectAttributes))
	{
		//这个成员是一个指针 ObjectName。效验指针是否为空，接着能否够訪问。这是第二层的效验
		if (ObjectAttributes->ObjectName != NULL && MmIsAddressValid(ObjectAttributes->ObjectName))
		{
			//深度校验检查
			if (ObjectAttributes->ObjectName->Buffer != NULL && ValidateUnicodeString(ObjectAttributes->ObjectName->Buffer))
			{
				//如今才干够安全不蓝屏的訪问这个Buffer
				DbgPrint("OpenObjectName %ws
", ObjectAttributes->ObjectName->Buffer);
			}
		}
	}


	//假设我们要取ProcessHandle怎么办？
	status = RealZwOpenProcess(ProcessHandle, 
		DesiredAccess, 
		ObjectAttributes, 
		ClientId
		);
	if (NT_SUCCESS(status))
	{
		//为什么我们这里不用效验ProcessHandle？
		//由于函数调用成功了
		handle_process_handle = *ProcessHandle;

		//然后我们还能够通过handle，得到eprocess。即 handle->eprocess。另一堆的转换，比方eprocess->handle, handle->fileobject
		status = ObReferenceObjectByHandle(handle_process_handle, 
			GENERIC_READ,
			*PsProcessType, 
			KernelMode, 
			(PVOID*)&eprocess_process_object, 
			0); 
		if(NT_SUCCESS(status))
		{
			DbgPrint("@@ OpenProcess %s by %s
", PsGetProcessImageFileName(eprocess_process_object), PsGetProcessImageFileName(PsGetCurrentProcess()));

			//这里非常重要，消除引用计数
			ObDereferenceObject(eprocess_process_object);
		}

		//仅仅要RealZwOpenProcess调用成功，不管怎样一定要返回成功
		status = STATUS_SUCCESS;
	}

	return status;
}

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

//驱动卸载的例程函数
VOID DriverUnload(IN PDRIVER_OBJECT DriverObject)
{
	//卸载Hook
	if (ul_ZwOpenProcess)
	{
		//移除SSDT表的Hook
		if (MdlRemoveSSDTHook((ULONG_PTR)ul_ZwOpenProcess, NewZwOpenProcess, &RealZwOpenProcess) == STATUS_SUCCESS)
		{
			DbgPrint("ZwOpenProcess Remove hook success
");
		}
	}

	DbgPrint("DriverUnload
");
}


//驱动入口例程函数
NTSTATUS DriverEntry(IN PDRIVER_OBJECT DriverObject,PUNICODE_STRING RegistryPath)
{
	//设置驱动的卸载例程函数
	DriverObject->DriverUnload = DriverUnload;


	RtlInitUnicodeString(&unicode_string, L"ZwOpenProcess");

	//获取要Hook函数的真实函数地址
	ul_ZwOpenProcess = (ULONG_PTR)MmGetSystemRoutineAddress(&unicode_string);
	if (ul_ZwOpenProcess)
	{
		if (MdlSSDTHook((ULONG_PTR)ul_ZwOpenProcess, NewZwOpenProcess, &RealZwOpenProcess) == STATUS_SUCCESS)
		{
			DbgPrint("ZwZwOpenProcess hook success
");
		}
	}
	return STATUS_SUCCESS;
}

makefile文件的编写：

#
# DO NOT EDIT THIS FILE!!!  Edit .sources. if you want to add a new source
# file to this component.  This file merely indirects to the real make file
# that is shared by all the driver components of the Windows NT DDK
#

!INCLUDE $(NTMAKEENV)makefile.def

sources文件的编写：

# $Id$
TARGETNAME=SSDTHook
TARGETPATH=obj
TARGETTYPE=DRIVER


# Create browse info
#BROWSER_INFO=1
#BROWSERFILE=<some path>

# Additional defines for the C/C++ preprocessor
C_DEFINES=$(C_DEFINES)

SOURCES=SSDTHook.c
	SSDT.c

參考资料：

AGP讲课资料的改动和整理。