//----------------------------------------------------------------------
//
// HookDrive
//
// Hook the drive specified by determining which device object to
// attach to. The algorithm used here is similar to the one used
// internally by NT to determine which device object a file system request
// is directed at.
//
//----------------------------------------------------------------------
BOOLEAN
HookDrive(
??? IN ULONG Drive,
??? IN PDRIVER_OBJECT DriverObject
??? )
{
??? IO_STATUS_BLOCK???? ioStatus;
??? HANDLE????????????? ntFileHandle;??
??? OBJECT_ATTRIBUTES?? objectAttributes;
??? PDEVICE_OBJECT????? fileSysDevice;
??? PDEVICE_OBJECT????? hookDevice;
??? UNICODE_STRING????? fileNameUnicodeString;
??? PFILE_FS_ATTRIBUTE_INFORMATION fileFsAttributes;
??? ULONG?????????????? fileFsAttributesSize;
??? WCHAR?????????????? filename[] = L" \\DosDevices\\A:\\ ";
??? NTSTATUS??????????? ntStatus;
??? ULONG?????????????? i;
??? PFILE_OBJECT??????? fileObject;
??? PHOOK_EXTENSION???? hookExtension;
???
??? //
??? // Is it a legal drive letter?
??? //
??? if( Drive >= 26 ) {

??????? return FALSE;
??? }

??? //
??? // Has this drive already been hooked?
??? //
??? if( DriveHookDevices[Drive] == NULL ) {

??????? //
??????? // Frob the name to make it refer to the drive specified in the input
??????? // parameter.
??????? //
??????? filename[12] = (CHAR) ('A'+Drive);

??????? //
??????? // We have to figure out what device to hook - first open the volume's
??????? // root directory
??????? //
??????? RtlInitUnicodeString( &fileNameUnicodeString, filename );
??????? InitializeObjectAttributes( &objectAttributes, &fileNameUnicodeString,
??????????????????????????????????? OBJ_CASE_INSENSITIVE, NULL, NULL );
??????? ntStatus = ZwCreateFile( &ntFileHandle, SYNCHRONIZE|FILE_ANY_ACCESS,
???????????????????????????????? &objectAttributes, &ioStatus, NULL, 0, FILE_SHARE_READ|FILE_SHARE_WRITE,
???????????????????????????????? FILE_OPEN,
???????????????????????????????? FILE_SYNCHRONOUS_IO_NONALERT|FILE_DIRECTORY_FILE,
???????????????????????????????? NULL, 0 );
??????? if( !NT_SUCCESS( ntStatus ) ) {

??????????? DbgPrint(("Filemon: Could not open drive %c: %x\n", 'A'+Drive, ntStatus ));
??????????? return FALSE;
??????? }

??????? DbgPrint(("Filemon: opened the root directory!!! handle: %x\n", ntFileHandle));??

??????? //
??????? // Got the file handle, so now look-up the file-object it refers to
??????? //
??????? ntStatus = ObReferenceObjectByHandle( ntFileHandle, FILE_READ_DATA,
????????????????????????????????????????????? NULL, KernelMode, &fileObject, NULL );
??????? if( !NT_SUCCESS( ntStatus )) {

??????????? DbgPrint(("Filemon: Could not get fileobject from handle: %c\n", 'A'+Drive ));
??????????? ZwClose( ntFileHandle );
??????????? return FALSE;
??????? }

??????? //
??????? // Next, find out what device is associated with the file object by getting its related
??????? // device object
??????? //
??????? fileSysDevice = IoGetRelatedDeviceObject( fileObject );

??????? if( ! fileSysDevice ) {

??????????? DbgPrint(("Filemon: Could not get related device object: %c\n", 'A'+Drive ));
??????????? ObDereferenceObject( fileObject );
??????????? ZwClose( ntFileHandle );
??????????? return FALSE;
??????? }

??????? //
??????? // Check the device list to see if we've already attached to this particular device.
??????? // This can happen when more than one drive letter is being handled by the same network
??????? // redirecter
??????? //
??????? for( i = 0; i < 26; i++ ) {

??????????? if( DriveHookDevices[i] == fileSysDevice ) {

??????????????? //
??????????????? // If we're already watching it, associate this drive letter
??????????????? // with the others that are handled by the same network driver. This
??????????????? // enables us to intelligently update the hooking menus when the user
??????????????? // specifies that one of the group should not be watched -we mark all
??????????????? // of the related drives as unwatched as well
??????????????? //
??????????????? ObDereferenceObject( fileObject );
??????????????? ZwClose( ntFileHandle );
??????????????? DriveHookDevices[ Drive ] = fileSysDevice;
??????????????? return TRUE;
??????????? }
??????? }

??????? //
??????? // The file system's device hasn't been hooked already, so make a hooking device
??????? // object that will be attached to it.
??????? //
??????? ntStatus = IoCreateDevice( DriverObject,
?????????????????????????????????? sizeof(HOOK_EXTENSION),
?????????????????????????????????? NULL,
?????????????????????????????????? fileSysDevice->DeviceType,
?????????????????????????????????? 0,
?????????????????????????????????? FALSE,
?????????????????????????????????? &hookDevice );
??????? if( !NT_SUCCESS(ntStatus) ) {

??????????? DbgPrint(("Filemon: failed to create associated device: %c\n", 'A'+Drive ));??

??????????? ObDereferenceObject( fileObject );
??????????? ZwClose( ntFileHandle );

??????????? return FALSE;
??????? }

??????? //
??????? // Clear the device's init flag as per NT DDK KB article on creating device
??????? // objects from a dispatch routine
??????? //
??????? hookDevice->Flags &= ~DO_DEVICE_INITIALIZING;

??????? //
??????? // Setup the device extensions. The drive letter and file system object are stored
??????? // in the extension.
??????? //
??????? hookExtension = hookDevice->DeviceExtension;
??????? hookExtension->LogicalDrive = 'A'+Drive;
??????? hookExtension->FileSystem?? = fileSysDevice;
??????? hookExtension->Hooked?????? = TRUE;
??????? hookExtension->Type???????? = STANDARD;

??????? //
??????? // Finally, attach to the device. The second we're successfully attached, we may
??????? // start receiving IRPs targetted at the device we've hooked.
??????? //
??????? ntStatus = IoAttachDeviceByPointer( hookDevice, fileSysDevice );
??????? if( !NT_SUCCESS(ntStatus) ) {

??????????? //
??????????? // Couldn' attach for some reason
??????????? //
??????????? DbgPrint(("Filemon: Connect with Filesystem failed: %c (%x) =>%x\n",
????????????????????? 'A'+Drive, fileSysDevice, ntStatus ));

??????????? //
??????????? // Derefence the object and get out
??????????? //
??????????? ObDereferenceObject( fileObject );
??????????? ZwClose( ntFileHandle );

??????????? return FALSE;

??????? } else {

??????????? //
??????????? // Make a new drive group for the device,l if it does not have one
??????????? // already
??????????? //
??????????? DbgPrint(("Filemon: Successfully connected to Filesystem device %c\n", 'A'+Drive ));
??????? }

??????? //
??????? // Determine if this is a NTFS drive
??????? //
??????? fileFsAttributesSize = sizeof( FILE_FS_ATTRIBUTE_INFORMATION) + MAXPATHLEN;
??????? hookExtension->FsAttributes = (PFILE_FS_ATTRIBUTE_INFORMATION) ExAllocatePool( NonPagedPool,
?????????????????????????????????????????????????????????????????????????????????????? fileFsAttributesSize );
??????? if( hookExtension->FsAttributes &&
??????????? !NT_SUCCESS( IoQueryVolumeInformation( fileObject, FileFsAttributeInformation,
?????????????????????????????????????????????????? fileFsAttributesSize, hookExtension->FsAttributes,
?????????????????????????????????????????????????? &fileFsAttributesSize ))) {

??????????? //
??????????? // On failure, we just don't have attributes for this file system
??????????? //
??????????? ExFreePool( hookExtension->FsAttributes );
??????????? hookExtension->FsAttributes = NULL;
??????? }

??????? //
??????? // Close the file and update the hooked drive list by entering a
??????? // pointer to the hook device object in it.
??????? //
??????? ObDereferenceObject( fileObject );

??????? ZwClose( ntFileHandle );

??????? DriveHookDevices[Drive] = hookDevice;
???????
??? } else {

??????? hookExtension = DriveHookDevices[Drive]->DeviceExtension;
??????? hookExtension->Hooked = TRUE;
??? }
??? return TRUE;
}

以上摘自FileMon源碼，作者在獲得要hook的設備的DeviceObject的時候用了以下方式：

ZwCreateFile——》ObReferenceObjectByHandle——》IoGetRelatedDeviceObject

另外，這個設備對象也可以直接用一個函數獲得IoGetDeviceObjectPointer，該函數原型如下：

NTSTATUS
IoGetDeviceObjectPointer(
??? IN PUNICODE_STRING ObjectName ,
??? IN ACCESS_MASK DesiredAccess ,
??? OUT PFILE_OBJECT * FileObject ,
??? OUT PDEVICE_OBJECT * DeviceObject
??? );

直接由名字獲得設備對象和文件對象，而該函數內部的實現方式combojiang大俠也給出過c的逆向代碼如下： 逆向為c的代碼：
NTSTATUS
IoGetDeviceObjectPointer(
???? IN PUNICODE_STRING ObjectName,
???? IN ACCESS_MASK DesiredAccess,
???? OUT PFILE_OBJECT *FileObject,
???? OUT PDEVICE_OBJECT *DeviceObject
???? )
{
???? IO_STATUS_BLOCK ioStatus;
???? OBJECT_ATTRIBUTES objectAttributes;
????
???? //額外定義出來的棧變量。由于C與匯編的游戲規則不同。
???? PFILE_OBJECT fileObject;
???? HANDLE fileHandle;
???? NTSTATUS status;
????
???? InitializeObjectAttributes( &objectAttributes,
???????????????????????????????? ObjectName,
???????????????????????????????? OBJ_KERNEL_HANDLE,
???????????????????????????????? (HANDLE) NULL,
???????????????????????????????? (PSECURITY_DESCRIPTOR) NULL );
????????????????????????????????
??? status = ZwOpenFile( &fileHandle,
????????????????????????? DesiredAccess,
????????????????????????? &objectAttributes,
????????????????????????? &ioStatus,
????????????????????????? 0,
????????????????????????? 0x40 );

???? if (status >= 0)
???? {

????????? status = ObReferenceObjectByHandle( fileHandle,
???????????????????????????????????????????? 0,
???????????????????????????????????????????? IoFileObjectType,
???????????????????????????????????????????? 0,
???????????????????????????????????????????? (PVOID *) &fileObject,
???????????????????????????????????????????? 0 );
???????? if (status >= 0)
???????? {

???????????? *FileObject = fileObject;
???????????? *DeviceObject = IoGetRelatedDeviceObject( fileObject );
???????? }

???????? ZwClose( fileHandle );
???? }

???? return status;
}
與FileMon的源碼使用的方法類似，所以FileMon源碼里面應該可以用這個函數直接替代，但是原作者沒有直接調用這個函數，不知道原因是什么，難道是寫FileMon的時候還沒提供這個函數，所以要自己來實現嗎？