7.6 Windows驱动开发：内核监控FileObject文件回调
本篇文章与上一篇文章《内核注册并监控对象回调》所使用的方式是一样的都是使用ObRegisterCallbacks注册回调事件，只不过上一篇博文中LyShark将回调结构体OB_OPERATION_REGISTRATION中的ObjectType填充为了PsProcessType和PsThreadType格式从而实现监控进程与线程，本章我们需要将该结构填充为IoFileObjectType以此来实现对文件的监控，文件过滤驱动不仅仅可以用来监控文件的打开，还可以用它实现对文件的保护，一旦驱动加载则文件是不可被删除和改动的。
ObRegisterCallbacks是Windows操作系统提供的一个内核API函数，用于注册对象回调函数。对象回调函数是一种内核回调函数，可以用于监视和拦截系统中的对象操作，例如文件、进程、线程等。
在文件系统中，FileObject是内核中表示文件对象的结构体，包含了文件的相关信息，例如文件名、文件句柄、访问权限等。当操作系统执行文件操作时，会使用FileObject结构体来表示文件对象。
通过ObRegisterCallbacks函数，开发者可以注册FileObject的回调函数，并在其中执行自定义逻辑，例如记录文件访问日志、过滤敏感数据等。当操作系统执行与FileObject相关的操作时，例如文件的创建、打开、读取、写入等操作，会调用已注册的回调函数，并将相关的操作信息传递给回调函数。
需要注意的是，FileObject回调函数的注册和取消注册必须在内核模式下进行，并且需要开发者有一定的内核开发经验。同时，回调函数也需要遵守一些约束条件，例如不能阻塞或挂起进程或线程的创建或访问，不能调用一些内核API函数等。
内核监控FileObject文件回调在安全软件、系统监控和调试工具等领域有着广泛的应用。开发者可以利用这个机制来监视和拦截系统中的文件操作，以保护系统安全。
与进程线程回调有少许的不同，文件回调需要开启驱动的TypeInfo.SupportsObjectCallbacks开关，并定义一些微软结构，如下是我们所需要的公开结构体，可在微软官方或WinDBG中获取到最新的，将其保存为lyshark.h方便后期引用。
#include <ntddk.h>
#include <ntstrsafe.h>
typedef struct _CALLBACK_ENTRY
{
LIST_ENTRY CallbackList;
OB_OPERATION Operations;
ULONG Active;
PVOID Handle;
POBJECT_TYPE ObjectType;
POB_PRE_OPERATION_CALLBACK PreOperation;
POB_POST_OPERATION_CALLBACK PostOperation;
ULONG unknown;
} CALLBACK_ENTRY, *PCALLBACK_ENTRY;
typedef struct _LDR_DATA // 24 elements, 0xE0 bytes (sizeof)
{
/*0x000*/ struct _LIST_ENTRY InLoadOrderLinks; // 2 elements, 0x10 bytes (sizeof)
/*0x010*/ struct _LIST_ENTRY InMemoryOrderLinks; // 2 elements, 0x10 bytes (sizeof)
/*0x020*/ struct _LIST_ENTRY InInitializationOrderLinks; // 2 elements, 0x10 bytes (sizeof)
/*0x030*/ VOID* DllBase;
/*0x038*/ VOID* EntryPoint;
/*0x040*/ ULONG32 SizeOfImage;
/*0x044*/ UINT8 _PADDING0_[0x4];
/*0x048*/ struct _UNICODE_STRING FullDllName; // 3 elements, 0x10 bytes (sizeof)
/*0x058*/ struct _UNICODE_STRING BaseDllName; // 3 elements, 0x10 bytes (sizeof)
/*0x068*/ ULONG32 Flags;
/*0x06C*/ UINT16 LoadCount;
/*0x06E*/ UINT16 TlsIndex;
union // 2 elements, 0x10 bytes (sizeof)
{
/*0x070*/ struct _LIST_ENTRY HashLinks; // 2 elements, 0x10 bytes (sizeof)
struct // 2 elements, 0x10 bytes (sizeof)
{
/*0x070*/ VOID* SectionPointer;
/*0x078*/ ULONG32 CheckSum;
/*0x07C*/ UINT8 _PADDING1_[0x4];
};
};
union // 2 elements, 0x8 bytes (sizeof)
{
/*0x080*/ ULONG32 TimeDateStamp;
/*0x080*/ VOID* LoadedImports;
};
/*0x088*/ struct _ACTIVATION_CONTEXT* EntryPointActivationContext;
/*0x090*/ VOID* PatchInformation;
/*0x098*/ struct _LIST_ENTRY ForwarderLinks; // 2 elements, 0x10 bytes (sizeof)
/*0x0A8*/ struct _LIST_ENTRY ServiceTagLinks; // 2 elements, 0x10 bytes (sizeof)
/*0x0B8*/ struct _LIST_ENTRY StaticLinks; // 2 elements, 0x10 bytes (sizeof)
/*0x0C8*/ VOID* ContextInformation;
/*0x0D0*/ UINT64 OriginalBase;
/*0x0D8*/ union _LARGE_INTEGER LoadTime; // 4 elements, 0x8 bytes (sizeof)
}LDR_DATA, *PLDR_DATA;
typedef struct _OBJECT_TYPE_INITIALIZER // 25 elements, 0x70 bytes (sizeof)
{
/*0x000*/ UINT16 Length;
union // 2 elements, 0x1 bytes (sizeof)
{
/*0x002*/ UINT8 ObjectTypeFlags;
struct // 7 elements, 0x1 bytes (sizeof)
{
/*0x002*/ UINT8 CaseInsensitive : 1; // 0 BitPosition
/*0x002*/ UINT8 UnnamedObjectsOnly : 1; // 1 BitPosition
/*0x002*/ UINT8 UseDefaultObject : 1; // 2 BitPosition
/*0x002*/ UINT8 SecurityRequired : 1; // 3 BitPosition
/*0x002*/ UINT8 MaintainHandleCount : 1; // 4 BitPosition
/*0x002*/ UINT8 MaintainTypeList : 1; // 5 BitPosition
/*0x002*/ UINT8 SupportsObjectCallbacks : 1; // 6 BitPosition
};
};
/*0x004*/ ULONG32 ObjectTypeCode;
/*0x008*/ ULONG32 InvalidAttributes;
/*0x00C*/ struct _GENERIC_MAPPING GenericMapping; // 4 elements, 0x10 bytes (sizeof)
/*0x01C*/ ULONG32 ValidAccessMask;
/*0x020*/ ULONG32 RetainAccess;
/*0x024*/ enum _POOL_TYPE PoolType;
/*0x028*/ ULONG32 DefaultPagedPoolCharge;
/*0x02C*/ ULONG32 DefaultNonPagedPoolCharge;
/*0x030*/ PVOID DumpProcedure;
/*0x038*/ PVOID OpenProcedure;
/*0x040*/ PVOID CloseProcedure;
/*0x048*/ PVOID DeleteProcedure;
/*0x050*/ PVOID ParseProcedure;
/*0x058*/ PVOID SecurityProcedure;
/*0x060*/ PVOID QueryNameProcedure;
/*0x068*/ PVOID OkayToCloseProcedure;
}OBJECT_TYPE_INITIALIZER, *POBJECT_TYPE_INITIALIZER;
typedef struct _EX_PUSH_LOCK // 7 elements, 0x8 bytes (sizeof)
{
union // 3 elements, 0x8 bytes (sizeof)
{
struct // 5 elements, 0x8 bytes (sizeof)
{
/*0x000*/ UINT64 Locked : 1; // 0 BitPosition
/*0x000*/ UINT64 Waiting : 1; // 1 BitPosition
/*0x000*/ UINT64 Waking : 1; // 2 BitPosition
/*0x000*/ UINT64 MultipleShared : 1; // 3 BitPosition
/*0x000*/ UINT64 Shared : 60; // 4 BitPosition
};
/*0x000*/ UINT64 Value;
/*0x000*/ VOID* Ptr;
};
}EX_PUSH_LOCK, *PEX_PUSH_LOCK;
typedef struct _MY_OBJECT_TYPE // 12 elements, 0xD0 bytes (sizeof)
{
/*0x000*/ struct _LIST_ENTRY TypeList; // 2 elements, 0x10 bytes (sizeof)
/*0x010*/ struct _UNICODE_STRING Name; // 3 elements, 0x10 bytes (sizeof)
/*0x020*/ VOID* DefaultObject;
/*0x028*/ UINT8 Index;
/*0x029*/ UINT8 _PADDING0_[0x3];
/*0x02C*/ ULONG32 TotalNumberOfObjects;
/*0x030*/ ULONG32 TotalNumberOfHandles;
/*0x034*/ ULONG32 HighWaterNumberOfObjects;
/*0x038*/ ULONG32 HighWaterNumberOfHandles;
/*0x03C*/ UINT8 _PADDING1_[0x4];
/*0x040*/ struct _OBJECT_TYPE_INITIALIZER TypeInfo; // 25 elements, 0x70 bytes (sizeof)
/*0x0B0*/ struct _EX_PUSH_LOCK TypeLock; // 7 elements, 0x8 bytes (sizeof)
/*0x0B8*/ ULONG32 Key;
/*0x0BC*/ UINT8 _PADDING2_[0x4];
/*0x0C0*/ struct _LIST_ENTRY CallbackList; // 2 elements, 0x10 bytes (sizeof)
}MY_OBJECT_TYPE, *PMY_OBJECT_TYPE;
对于开启了TypeInfo.SupportsObjectCallbacks属性的驱动来说自然就支持文件路径转换，当系统中有文件被加载则自动执行LySharkFileObjectpreCall回调事件，过滤掉无效路径后即可直接输出，完整代码如下所示；
#include "lyshark.h"
PVOID obHandle;
DRIVER_INITIALIZE DriverEntry;
// 文件回调
OB_PREOP_CALLBACK_STATUS LySharkFileObjectpreCall(PVOID RegistrationContext, POB_PRE_OPERATION_INFORMATION OperationInformation)
{
UNICODE_STRING DosName;
PFILE_OBJECT fileo = OperationInformation->Object;
HANDLE CurrentProcessId = PsGetCurrentProcessId();
UNREFERENCED_PARAMETER(RegistrationContext);
if (OperationInformation->ObjectType != *IoFileObjectType)
{
return OB_PREOP_SUCCESS;
}
// 过滤无效指针
if (fileo->FileName.Buffer == NULL ||
!MmIsAddressValid(fileo->FileName.Buffer) ||
fileo->DeviceObject == NULL ||
!MmIsAddressValid(fileo->DeviceObject))
{
return OB_PREOP_SUCCESS;
}
// 过滤无效路径
if (!_wcsicmp(fileo->FileName.Buffer, L"\\Endpoint") ||
!_wcsicmp(fileo->FileName.Buffer, L"?") ||
!_wcsicmp(fileo->FileName.Buffer, L"\\.\\.") ||
!_wcsicmp(fileo->FileName.Buffer, L"\\"))
{
return OB_PREOP_SUCCESS;
}
// 将对象转为DOS路径
RtlVolumeDeviceToDosName(fileo->DeviceObject, &DosName);
DbgPrint("[LyShark] 进程PID = %ld | 文件路径 = %wZ%wZ \n", (ULONG64)CurrentProcessId, &DosName, &fileo->FileName);
return OB_PREOP_SUCCESS;
}
VOID EnableObType(POBJECT_TYPE ObjectType)
{
PMY_OBJECT_TYPE myobtype = (PMY_OBJECT_TYPE)ObjectType;
myobtype->TypeInfo.SupportsObjectCallbacks = 1;
}
VOID UnDriver(PDRIVER_OBJECT driver)
{
UNREFERENCED_PARAMETER(driver);
ObUnRegisterCallbacks(obHandle);
}
NTSTATUS DriverEntry(IN PDRIVER_OBJECT Driver, PUNICODE_STRING RegistryPath)
{
NTSTATUS status = STATUS_SUCCESS;
PLDR_DATA ldr;
DbgPrint("hello lyshark \n");
OB_CALLBACK_REGISTRATION obRegFileCallBack;
OB_OPERATION_REGISTRATION opRegFileCallBack;
// enable IoFileObjectType
EnableObType(*IoFileObjectType);
// bypass MmVerifyCallbackFunction
ldr = (PLDR_DATA)Driver->DriverSection;
ldr->Flags |= 0x20;
// 初始化回调
memset(&obRegFileCallBack, 0, sizeof(obRegFileCallBack));
obRegFileCallBack.Version = ObGetFilterVersion();
obRegFileCallBack.OperationRegistrationCount = 1;
obRegFileCallBack.RegistrationContext = NULL;
RtlInitUnicodeString(&obRegFileCallBack.Altitude, L"321000");
obRegFileCallBack.OperationRegistration = &opRegFileCallBack;
memset(&opRegFileCallBack, 0, sizeof(opRegFileCallBack));
opRegFileCallBack.ObjectType = IoFileObjectType;
opRegFileCallBack.Operations = OB_OPERATION_HANDLE_CREATE | OB_OPERATION_HANDLE_DUPLICATE;
opRegFileCallBack.PreOperation = (POB_PRE_OPERATION_CALLBACK)&LySharkFileObjectpreCall;
status = ObRegisterCallbacks(&obRegFileCallBack, &obHandle);
if (!NT_SUCCESS(status))
{
DbgPrint("注册回调错误 \n");
status = STATUS_UNSUCCESSFUL;
}
UNREFERENCED_PARAMETER(RegistryPath);
Driver->DriverUnload = &UnDriver;
return status;
}
运行这个驱动程序，当系统中有新文件被加载时则自动输出该文件所属进程PID以及该文件的详细路径。
至于如何阻止打开一个文件其实与《内核注册并监控对象回调》文章中使用的方法是一致的，首先判断OperationInformation->Operation是不是OB_OPERATION_HANDLE_CREATE或OB_OPERATION_HANDLE_DUPLICATE如果是，则直接设置Parameters->CreateHandleInformation.DesiredAccess为0直接拒绝加载。
// 文件回调
OB_PREOP_CALLBACK_STATUS LySharkFileObjectpreCall(PVOID RegistrationContext, POB_PRE_OPERATION_INFORMATION OperationInformation)
{
UNICODE_STRING DosName;
PFILE_OBJECT fileo = OperationInformation->Object;
HANDLE CurrentProcessId = PsGetCurrentProcessId();
UNREFERENCED_PARAMETER(RegistrationContext);
if (OperationInformation->ObjectType != *IoFileObjectType)
{
return OB_PREOP_SUCCESS;
}
// 过滤无效指针
if (fileo->FileName.Buffer == NULL ||
!MmIsAddressValid(fileo->FileName.Buffer) ||
fileo->DeviceObject == NULL ||
!MmIsAddressValid(fileo->DeviceObject))
{
return OB_PREOP_SUCCESS;
}
// 过滤无效路径
if (!_wcsicmp(fileo->FileName.Buffer, L"\\Endpoint") ||
!_wcsicmp(fileo->FileName.Buffer, L"?") ||
!_wcsicmp(fileo->FileName.Buffer, L"\\.\\.") ||
!_wcsicmp(fileo->FileName.Buffer, L"\\"))
{
return OB_PREOP_SUCCESS;
}
// 阻止打开lyshark_com.txt文本
if (wcsstr(_wcslwr(fileo->FileName.Buffer), L"lyshark_com.txt"))
{
if (OperationInformation->Operation == OB_OPERATION_HANDLE_CREATE)
{
OperationInformation->Parameters->CreateHandleInformation.DesiredAccess = 0;
}
if (OperationInformation->Operation == OB_OPERATION_HANDLE_DUPLICATE)
{
OperationInformation->Parameters->DuplicateHandleInformation.DesiredAccess = 0;
}
DbgPrint("[LyShark] 已拦截 lyshark_com 文件打开 \n");
}
return OB_PREOP_SUCCESS;
}
运行修改后的驱动程序，然后尝试打开lyshark_com.txt则会提示系统找不到指定文件。
