Kernel mode driver

Submitted on: 2/28/2019 9:24:26 AM
By: The trick  
Level: Advanced
User Rating: By 5 Users
Compatibility: VB 6.0
Views: 8645
     The 32-bit ring-0 kernel mode driver written in VB6 for reading the arbitrary kernel memory.

This article has accompanying files


Hello everyone (sorry my English). There was a time, and decided to write something unusual on VB6, namely to try to write a driver. I must say before that I never wrote a driver and have no programming experience in kernel mode. The driver, according to my idea, will have to read the memory is not available in user mode, namely in the range 0x80000000 - 0xffffffff (in default mode, without IMAGE_FILE_LARGE_ADDRESS_AWARE). Immediately give the driver source code which is obtained:

' // modTrickMemReader.bas - driver module
' // © Krivous Anatoly Anatolevich (The trick), 2014
Option Explicit
Public Enum NT_STATUS
End Enum
Length As Integer
MaximumLengthAs Integer
lpBufferAs Long
End Type
Public Type LIST_ENTRY
FlinkAs Long
BlinkAs Long
End Type
TypeAs Integer
SizeAs Integer
DeviceListHead As LIST_ENTRY
LockAs Long
BusyAs Long
End Type
Public Type KDPC
TypeAs Byte
Importance As Byte
Number As Integer
DeferredRoutine As Long
DeferredContext As Long
SystemArgument1 As Long
SystemArgument2 As Long
DpcData As Long
End Type
LockAs Long
SignalState As Long
End Type
Public Type KEVENT
End Type
StatusPointerAs Long
Information As Long
End Type
Public Type Tail
DriverContext(3)As Long
Thread As Long
AuxiliaryBuffer As Long
lpCurStackLocation As Long
OriginalFileObject As Long
End Type
Public Type IRP
TypeAs Integer
SizeAs Integer
MdlAddress As Long
FlagsAs Long
AssociatedIrpAs Long
ThreadListEntry As LIST_ENTRY
RequestorModeAs Byte
PendingReturned As Byte
StackCount As Byte
CurrentLocation As Byte
Cancel As Byte
CancelIrql As Byte
ApcEnvironment As Byte
AllocationFlags As Byte
UserIosbAs Long
UserEventAs Long
Overlay As Currency
CancelRoutineAs Long
UserBuffer As Long
TailAs Tail
End Type
OutputBufferLength As Long
InputBufferLengthAs Long
IoControlCodeAs Long
Type3InputBufferAs Long
End Type
MajorFunctionAs Byte
MinorFunctionAs Byte
FlagsAs Byte
Control As Byte
' Поле DeviceIoControl из объединения
DeviceIoControl As DEVICEIOCTL
pDeviceObjectAs Long
pFileObject As Long
pCompletionRoutine As Long
pContextAs Long
End Type
TypeAs Integer
SizeAs Integer
pDeviceObjectAs Long
FlagsAs Long
DriverStart As Long
DriverSize As Long
DriverSectionAs Long
DriverExtension As Long
HardwareDatabaseAs Long
FastIoDispatch As Long
DriverInit As Long
DriverStartIoAs Long
DriverUnloadAs Long
MajorFunction(27)As Long
End Type
TypeAs Integer
SizeAs Integer
ReferenceCount As Long
DriverObjectAs Long
NextDevice As Long
AttachedDevice As Long
CurrentIrp As Long
TimerAs Long
FlagsAs Long
Characteristics As Long
Vpb As Long
DeviceExtension As Long
DeviceType As Long
StackSizeAs Byte
Queue(39)As Byte
AlignRequirementAs Long
ActiveThreadCountAs Long
SecurityDescriptor As Long
DeviceLock As KEVENT
SectorSize As Integer
Spare1 As Integer
DeviceObjExtension As Long
ReservedAs Long
End Type
Private Type BinaryString
D(255) As Integer
End Type
Public Const FILE_DEVICE_UNKNOWNAs Long = &H22
Public Const IO_NO_INCREMENTAs Long = &H0
Public Const IRP_MJ_CREATE As Long = &H0
Public Const IRP_MJ_CLOSEAs Long = &H2
Public Const IRP_MJ_DEVICE_CONTROL As Long = &HE
Public Const FILE_DEVICE_MEMREADER As Long = &H8000&
Public Const IOCTL_READ_MEMORY As Long = &H80002000
Public DeviceNameAs UNICODE_STRING' // Device name unicode string
Public DeviceLinkAs UNICODE_STRING' // Device link unicode string
Public DeviceAs DEVICE_OBJECT' // Device object
Dim strName As BinaryString ' // Device name string
Dim strLink As BinaryString ' // Device link string
Public Sub Main()
End Sub
' // If error - false
Public Function NT_SUCCESS( _
ByVal Status As NT_STATUS) As Boolean
End Function
' // Get pointer to IRP stack
Public Function IoGetCurrentIrpStackLocation( _
ByRef pIrp As IRP) As Long
IoGetCurrentIrpStackLocation = pIrp.Tail.lpCurStackLocation
End Function
' // Entry point of driver
Public Function DriverEntry( _
ByRef DriverObject As DRIVER_OBJECT, _
Dim Status As NT_STATUS
' // Strings initialization
Status = Init()
' // This checking is not required but i left it because you can improve Init function
If Not NT_SUCCESS(Status) Then
DriverEntry = Status
Exit Function
End If
' // Create new device
Status = IoCreateDevice(DriverObject, 0, DeviceName, FILE_DEVICE_MEMREADER, 0, False, Device)
' // Check if device has been created
If Not NT_SUCCESS(Status) Then
DriverEntry = Status
Exit Function
End If
' // Create link, in order to access to object from user mode
Status = IoCreateSymbolicLink(DeviceLink, DeviceName)
' // Check if link has been created
If Not NT_SUCCESS(Status) Then
' // If is not created then delete device
IoDeleteDevice Device
DriverEntry = Status
Exit Function
End If
' // Set callback functions
DriverObject.DriverUnload = GetAddr(AddressOf DriverUnload) ' // Driver unloading
DriverObject.MajorFunction(IRP_MJ_CREATE) = GetAddr(AddressOf DriverCreateClose)' // When CreateFile is being called
DriverObject.MajorFunction(IRP_MJ_CLOSE) = GetAddr(AddressOf DriverCreateClose) ' // When CloseHandle is being called
DriverObject.MajorFunction(IRP_MJ_DEVICE_CONTROL) = GetAddr(AddressOf DriverDeviceControl) ' // When DeviceIoControl is being called
' // Everything fine
End Function
' // Unloading driver procedure
Public Sub DriverUnload( _
ByRef DriverObject As DRIVER_OBJECT)
' // Delete link
IoDeleteSymbolicLink DeviceLink
' // Delete device
IoDeleteDevice ByVal DriverObject.pDeviceObject
End Sub
' // This function is being called during opening/closing driver
Public Function DriverCreateClose( _
ByRef DeviceObject As DEVICE_OBJECT, _
pIrp.IoStatus.Information = 0
pIrp.IoStatus.StatusPointer = STATUS_SUCCESS
' // Return IRP packet to IO manager
IoCompleteRequest pIrp, IO_NO_INCREMENT
' // Success
DriverCreateClose = STATUS_SUCCESS
End Function
' // IOCTL processing procedure
Public Function DriverDeviceControl( _
ByRef DeviceObject As DEVICE_OBJECT, _
Dim lpStack As Long
' // Get pointer to IRP stack
lpStack = IoGetCurrentIrpStackLocation(pIrp)
' // If valid pointer
If lpStack Then
' // Copy to local variable
memcpy ioStack, ByVal lpStack, Len(ioStack)
' // Check IOCTL and AssociatedIrp union that contains SystemBuffer
' // SystemBuffer contains the buffer passed from DeviceIoControl
If ioStack.DeviceIoControl.IoControlCode = IOCTL_READ_MEMORY And _
pIrp.AssociatedIrp <> 0 Then
Dim lpPointerAs Long
Dim DataSizeAs Long
' // Copy parameters from SystemBuffer
memcpy lpPointer, ByVal pIrp.AssociatedIrp, 4
memcpy DataSize, ByVal pIrp.AssociatedIrp + 4, 4
' П// Check buffer size
If DataSize <= ioStack.DeviceIoControl.OutputBufferLength Then
' // Get the number of allowed pages
Dim lpStart As Long
Dim pgCount As Long
Dim pgSize As Long
Dim pgOfst As Long
' // Get first address of page
lpStart = lpPointer And &HFFFFF000
' // Get offset at beginning of page
pgOfst = lpPointer And &HFFF&
' // Go thru pages and check PageFault error
Do While MmIsAddressValid(ByVal lpStart) And (pgSize - pgOfst < DataSize)
lpStart = lpStart + &H1000
pgCount = pgCount + 1
pgSize = pgSize + &H1000
' // If there are allowed pages
If pgCount Then
' // Get size in bytes
pgSize = pgCount * &H1000 - pgOfst
' // Fix size
If DataSize > pgSize Then DataSize = pgSize
' // Return total read bytes
pIrp.IoStatus.Information = DataSize
' // Success to DeviceIoControl
pIrp.IoStatus.StatusPointer = STATUS_SUCCESS
' Copy data to system buffer
memcpy ByVal pIrp.AssociatedIrp, ByVal lpPointer, DataSize
' // Return IRP packet to IO manager
IoCompleteRequest pIrp, IO_NO_INCREMENT
' // Success
DriverDeviceControl = STATUS_SUCCESS
' // Exit
Exit Function
End If
End If
End If
End If
' // Return real size of read bytes
pIrp.IoStatus.Information = 0
' // Error to DeviceIoControl
pIrp.IoStatus.StatusPointer = STATUS_INVALID_PARAMETER
' // Return IRP packet to IO manager
IoCompleteRequest pIrp, IO_NO_INCREMENT
' // Error
End Function
' // Initialize all strings
Private Function Init() As NT_STATUS
' // Initialize device name "\Device\TrickMemReader"
strName.D(0) = &H5C:strName.D(1) = &H44:strName.D(2) = &H65:strName.D(3) = &H76:strName.D(4) = &H69:
strName.D(5) = &H63:strName.D(6) = &H65:strName.D(7) = &H5C:strName.D(8) = &H54:strName.D(9) = &H72:
strName.D(10) = &H69:strName.D(11) = &H63:strName.D(12) = &H6B:strName.D(13) = &H4D:strName.D(14) = &H65:
strName.D(15) = &H6D:strName.D(16) = &H52:strName.D(17) = &H65:strName.D(18) = &H61:strName.D(19) = &H64:
strName.D(20) = &H65:strName.D(21) = &H72
' // Fill UNICODE_STRING structure
RtlInitUnicodeString DeviceName, strName
' // Initialize device link for user mode "\DosDevices\TrickMemReader"
strLink.D(0) = &H5C:strLink.D(1) = &H44:strLink.D(2) = &H6F:strLink.D(3) = &H73:strLink.D(4) = &H44:
strLink.D(5) = &H65:strLink.D(6) = &H76:strLink.D(7) = &H69:strLink.D(8) = &H63:strLink.D(9) = &H65:
strLink.D(10) = &H73:strLink.D(11) = &H5C:strLink.D(12) = &H54:strLink.D(13) = &H72:strLink.D(14) = &H69:
strLink.D(15) = &H63:strLink.D(16) = &H6B:strLink.D(17) = &H4D:strLink.D(18) = &H65:strLink.D(19) = &H6D:
strLink.D(20) = &H52:strLink.D(21) = &H65:strLink.D(22) = &H61:strLink.D(23) = &H64:strLink.D(24) = &H65
strLink.D(25) = &H72
' // Fill UNICODE_STRING structure
RtlInitUnicodeString DeviceLink, strLink
End Function
' // Return passed value
Private Function GetAddr( _
 ByVal Value As Long) As Long
GetAddr = Value
End Function
<--Created using on 2019-02-28 09:02:08 UTC -->
So, the driver must have an entry point DriverEntry, which causes the controller I/O driver is loaded. In the parameters of a pointer to an object-driver and a pointer to a string containing the name of the registry key corresponding to the loadable driver. In the Init procedure, we create two lines, one with the name of the device, the other with reference to the device name. Because we can not use the runtime kernel mode, it is necessary to create a string in the form of a static array, wrapped in a user-defined type, thereby VB6 allocates memory for the array on the stack. If you use a string that will inevitably be caused by one of the functions for runtime and copy assignment line, and we can not allow that. Then we can call IoCreateDevice, which creates a device object. Device object is the recipient of I/O requests and to him we will access when calling CreateFile function from user mode.

The first parameter is a pointer to an object-driver; the second parameter is 0, then since we do not have the structure of the expansion device, and we do not need to allocate memory; the third parameter we pass the name of the device, it is we need to implement access to the device; fourth parameter passed to the device type (see below). in the fifth, we pass 0 as we have "non-standard device"; in the sixth pass False, because We do not need single-user mode; the last parameter - the output. As the name of the device we have to use a string like DeviceDeviceName (where DeviceName - TrickMemReader), is the name we need to ensure that we can create a link to it, which in turn need to access the device from user mode.
Device type - FILE_DEVICE_MEMREADER. All non-standard devices must be of type or FILE_DEVICE_UNKNOWN, or the number of 0x8000 - 0xffff. I created FILE_DEVICE_MEMREADER constant with a value of 0x8000, which corresponds to the first free number. On success, the device is created and filled structure DEVICE_OBJECT. After the need to create a connection between the device name of the kernel mode and user mode. As the name we use DosDevicesTrickMemReader, from user mode, we will refer to it via the link '\.TrickMemReader". The link is created through IoCreateSymbolicLink. Next we define callback-procedure that will be called when certain events occur:

  1. DriverUnload - deinitialize driver;
  2. DriverCreateClose - when opening and closing device;
  3. DriverDeviceControl - when calling DeviceIoControl.

And So. Now we return STATUS_SUCCESS, which corresponds to the successful implementation.* Now consider the procedure DriverUnload. It's simple - we remove the connection and set up the device. In the processing functions of opening and closing device DriverCreateClose, the status of the request, we return a success, and return the IRP packet I/O manager. Exchange of data between an application and device via the IRP-packets. IRP-package consists of 2 parts: a header and a stack of variable length. Part of the structure represented by the type of IRP. So now we add functionality to our driver function DriverDeviceControl. In this function I/O Manager will send IRP-data packet transmitted from the client application, which we will generate a call to DeviceIoControl. The parameters we pass 2 Long numbers: 1st address, where produce reading, 2nd number of bytes to read. Also one of the parameters passed to IRP-bag, when calling DeviceIoControl, a control code input / output (IOCTL), which represents the structure of the device type, function number, the type of data and the type of access. You can define several such codes for different operations and use them. I defined the code so IOCTL_READ_MEMORY = 0x80002000, 8000 - corresponds to the type of our device (FILE_DEVICE_MEMREADER); function number = 0x800, values below are reserved for user-defined functions allowed values 0x800 - 0xFFF; the type of data transmission - 0x0 (METHOD_BUFFERED), it means that we will receive / transmit data through the buffer that is specified SystemBuffer IRP-package); access type - FILE_ANY_ACCESS.


So, as a function of DriverDeviceControl we get a pointer to the I/O stack IRP-query using the IoGetCurrentIrpStackLocation, which returns the parameter of lpCurStackLocation. When Successes (if non-zero pointer) is copied to the local structure IO_STACK_LOCATION parameters are referenced by the pointer. Now we check the IOCTL-code field AssociatedIrp, which is a union (in VB6 no associations) which stores a pointer to SystemBuffer. Because we have the type of data corresponds METHOD_BUFFERED, in parameter SystemBuffer contains a pointer to the buffer with the parameters (address and size) DeviceIoControl, in this buffer, we can also recover data that is written to the output buffer DeviceIoControl. Now, if we have data contains the correct values (IOCTL and SystemBuffer), then we copy into local variables (lpPointer, DataSize). Next, check the size of the buffer. Size of the system I/O buffer is contained in the parameter DeviceIoControl.OutputBufferLength. If the requested number of bytes is not larger than the size of the system buffer, then everything is fine. Now we need to calculate the number of memory pages occupied by the data that we want to copy. To do this, we define the virtual address of the beginning of the page corresponding to pass a pointer, and because page size is a multiple of 4 KB (0x1000) we simply vanish 12-bit pointer. Next, we check in the cycle will not be whether an exception is thrown Page fault using the MmIsAddressValid. If the page is not in memory, the function returns False. Thus we check the number of pages that you want us to take a piece of memory and the number of pages that we can read. Then we calculate the actual size of the data that we will be able to read and, if necessary, adjust the size. Next to the title of IRP-package we copy the data size that we can read and a successful status. IoStatus.Information field matches the value returned by DeviceIoControl parameter lpBytesReturned. Next copy in SystemBuffer right amount of bytes using RtlMoveMemory and return IRP-package I/O manager. Return the status of a successful operation. In all other cases, return error STATUS_INVALID_PARAMETER and zero data size. All the driver code is ready.

Proceed to the compilation. Because we can not use the runtime, all the API-functions, we declare a TLB, so that they fall into the import:

library ImportFunctionsForTrickMemReaderDriver
module Ntoskrnl
[entry("IoCreateDevice")]int IoCreateDevice
int DeviceExtensionSize,
int DeviceType,
int DeviceCharacteristics,
int Exclusive,
[entry("IoCreateSymbolicLink")]int IoCreateSymbolicLink
[entry("IoDeleteDevice")]void IoDeleteDevice
[entry("IoDeleteSymbolicLink")]int IoDeleteSymbolicLink
[entry("IoCompleteRequest")]void IoCompleteRequest
unsigned charPriorityBoost);
[entry("RtlInitUnicodeString")]int RtlInitUnicodeString
[entry("RtlMoveMemory")]void memcpy
int Length);
[entry("MmIsAddressValid")]int MmIsAddressValid
[entry("InterlockedExchange")]int InterlockedExchange
<--Created using on 2019-02-28 09:03:56 UTC -->
PS. InterlockedExchange - I left because first driver had a bit of a different structure, subsequently left the ad in the TLB. In the driver, it does not fall into imports.
To the driver worked to do three things:
  1. In the field Subsystem, structure IMAGE_OPTIONAL_HEADER PE-driver file should be the value that corresponds to IMAGE_SUBSYSTEM_NATIVE kernel-mode driver.
  2. Specify as the entry point of our procedure DriverEntry
  3. Add a relocation section, in order that the driver can be loaded at any address.
  4. Exclude MSVBVM60 of imports.

For the first 3 points are added to the compilation keys vbp-file with the following contents:

Compile the project with all the default optimization. To exclude the runtime of the import, I use a utility Patch, I used here. I'm a little modify it, as initially could not start the driver and long puzzled because of what it does, and the reason was the checksum. After exclusion of the import library checksum has changed, and I do not update it. And EXE, DLL, etc. this field is not checked, and the driver checks. To check the watch imports in any viewer PE:


As you can see there is no runtime. What we required.

To test driver I wrote a simple program that loads the driver and works with him.

' // frmTestTrickVBDriver.frm - test form for driver
' // © Krivous Anatoly Anatolevich (The trick), 2014
Option Explicit
dwServiceTypeAs Long
dwCurrentState As Long
dwControlsAccepted As Long
dwWin32ExitCode As Long
dwServiceSpecificExitCodeAs Long
dwCheckPointAs Long
dwWaitHint As Long
End Type
Private Declare Function ControlService Lib "advapi32.dll" ( _
 ByVal hService As Long, _
 ByVal dwControl As Long, _
 ByRef lpServiceStatus As SERVICE_STATUS) As Long
Private Declare Function OpenSCManager Lib "advapi32.dll" _
 Alias "OpenSCManagerW" ( _
 ByVal lpMachineName As Long, _
 ByVal lpDatabaseName As Long, _
 ByVal dwDesiredAccess As Long) As Long
Private Declare Function CloseServiceHandle Lib "advapi32.dll" ( _
 ByVal hSCObject As Long) As Long
Private Declare Function OpenService Lib "advapi32.dll" _
 Alias "OpenServiceW" ( _
 ByVal hSCManager As Long, _
 ByVal lpServiceName As Long, _
 ByVal dwDesiredAccess As Long) As Long
Private Declare Function CreateService Lib "advapi32.dll" _
 Alias "CreateServiceW" ( _
 ByVal hSCManager As Long, _
 ByVal lpServiceName As Long, _
 ByVal lpDisplayName As Long, _
 ByVal dwDesiredAccess As Long, _
 ByVal dwServiceType As Long, _
 ByVal dwStartType As Long, _
 ByVal dwErrorControl As Long, _
 ByVal lpBinaryPathName As Long, _
 ByVal lpLoadOrderGroup As String, _
 ByRef lpdwTagId As Long, _
 ByVal lpDependencies As Long, _
 ByVal lp As Long, _
 ByVal lpPassword As Long) As Long
Private Declare Function StartService Lib "advapi32.dll" _
 Alias "StartServiceW" ( _
 ByVal hService As Long, _
 ByVal dwNumServiceArgs As Long, _
 ByVal lpServiceArgVectors As Long) As Long
Private Declare Function DeleteService Lib "advapi32.dll" ( _
 ByVal hService As Long) As Long
Private Declare Function CreateFile Lib "kernel32" _
 Alias "CreateFileW" ( _
 ByVal lpFileName As Long, _
 ByVal dwDesiredAccess As Long, _
 ByVal dwShareMode As Long, _
 ByRef lpSecurityAttributes As Any, _
 ByVal dwCreationDisposition As Long, _
 ByVal dwFlagsAndAttributes As Long, _
 ByVal hTemplateFile As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" ( _
 ByVal hObject As Long) As Long
Private Declare Function DeviceIoControl Lib "kernel32" ( _
 ByVal hDevice As Long, _
 ByVal dwIoControlCode As Long, _
 ByRef lpInBuffer As Any, _
 ByVal nInBufferSize As Long, _
 ByRef lpOutBuffer As Any, _
 ByVal nOutBufferSize As Long, _
 ByRef lpBytesReturned As Long, _
 ByRef lpOverlapped As Any) As Long
Private Const ERROR_SERVICE_EXISTS As Long = 1073&
Private Const SERVICE_CONTROL_STOP As Long = &H1
Private Const SC_MANAGER_ALL_ACCESS As Long = &HF003F
Private Const SERVICE_ALL_ACCESSAs Long = &HF01FF
Private Const SERVICE_KERNEL_DRIVER As Long = &H1
Private Const SERVICE_DEMAND_START As Long = &H3
Private Const SERVICE_ERROR_NORMAL As Long = &H1
Private Const GENERIC_READ As Long = &H80000000
Private Const GENERIC_WRITE As Long = &H40000000
Private Const FILE_SHARE_READAs Long = &H1
Private Const FILE_SHARE_WRITE As Long = &H2
Private Const OPEN_EXISTING As Long = 3
Private Const FILE_ATTRIBUTE_NORMAL As Long = &H80
Private Const INVALID_HANDLE_VALUE As Long = -1
Private Const IOCTL_READ_MEMORY As Long = &H80002000
Private Const DriverNameAs String = "TrickMemReader"
Private Const NumOfRows As Long = 32
Private DriverFile As String
Private hMgrAs Long
Private hSrvAs Long
Private hDevAs Long
Private buffer()As Byte
Private bufLen As Long
Private Address As Long
' // Read memory from kernel space
Private Sub cmdRead_Click()
Dim param(1)As Long
On Error GoTo Cancel
Address = CLng("&H" & Trim(txtAddress.Text))
' // Make parameters
param(0) = Address
param(1) = 16 * NumOfRows
' // Send request
If DeviceIoControl(hDev, IOCTL_READ_MEMORY, param(0), 8, buffer(0), UBound(buffer) + 1, bufLen, ByVal 0&) = 0 Then
bufLen = 0
End If
End Sub
Private Sub Form_Load()
Dim sw As Long
Dim sh As Long
' // Allocate buffer
ReDim buffer(16 * NumOfRows - 1)
' // Get driver file name
DriverFile = App.Path & "\" & DriverName & ".sys"
' // Open SC manager database
hMgr = OpenSCManager(0, 0, SC_MANAGER_ALL_ACCESS)
If hMgr = 0 Then
MsgBox "Unable to establish connection with SC manager"
End If
' // Create servise
hSrv = CreateService(hMgr, StrPtr(DriverName), StrPtr(DriverName), SERVICE_ALL_ACCESS, _
0, 0, 0, 0, 0)
' // If service already has beend launched
If hSrv = 0 And Err.LastDllError = ERROR_SERVICE_EXISTS Then
' // Open existing service
hSrv = OpenService(hMgr, StrPtr(DriverName), SERVICE_ALL_ACCESS)
End If
If hSrv = 0 Then
MsgBox "Unable to create service"
Unload Me
End If
' // Launch driver
If StartService(hSrv, 0, 0) = 0 Then
MsgBox "Unable to start service"
Unload Me
End If
End If
' // Connect to driver
hDev = CreateFile(StrPtr("\\.\" & DriverName), GENERIC_READ Or FILE_SHARE_WRITE, FILE_SHARE_READ Or FILE_SHARE_WRITE, ByVal 0&, _
MsgBox "Unable to connect to driver"
Unload Me
End If
' // Determine control size and position
sw = picDump.TextWidth("_")
sh = picDump.TextHeight("_")
picDump.Move 5, 5, (sw * 77) + (picDump.Width - picDump.ScaleWidth), (sh * NumOfRows) + (picDump.Height - picDump.ScaleHeight)
lblAddress.Top = picDump.Top + picDump.Height + 5
txtAddress.Top = lblAddress.Top
cmdRead.Top = txtAddress.Top
Me.Width = (picDump.Width + 10 - Me.ScaleWidth) * Screen.TwipsPerPixelX + Me.Width
Me.Height = (txtAddress.Top + 5 + txtAddress.Height - Me.ScaleHeight) * Screen.TwipsPerPixelY + Me.Height
End Sub
' // Refresh data on window
Private Sub Update()
Dim col As Long
Dim row As Long
Dim ptr As Long
Dim hxd As String
Dim asi As String
Dim adr As String
Dim out As String
For row = 0 To NumOfRows - 1
adr = Hex(Address + row * 16)
adr = String(8 - Len(adr), "0") & adr
asi = ""
hxd = ""
For col = 0 To 15
If ptr < bufLen Then
hxd = hxd & " " & IIf(buffer(ptr) < &H10, "0" & Hex(buffer(ptr)), Hex(buffer(ptr)))
asi = asi & IIf(buffer(ptr) >= 32, Chr$(buffer(ptr)), "?")
hxd = hxd & " ??"
asi = asi & "?"
End If
ptr = ptr + 1
If row Then out = out & vbNewLine
out = out & adr & ":" & hxd & " | " & asi
picDump.Print out
End Sub
Private Sub Form_Unload( _
ByRef Cancel As Integer)
' // Disconnect driver
CloseHandle hDev
' // Stop driver
ControlService hSrv, SERVICE_CONTROL_STOP, Status
' // Remove service
DeleteService hSrv
' // Close handles
CloseServiceHandle hSrv
CloseServiceHandle hMgr
End Sub
<--Created using on 2019-02-28 09:04:55 UTC -->
The driver must be in the same folder as the program. Code is commented, so I will not describe his work.

To debug a driver you want to use the kernel-mode debugger. Debug going on a virtual system (VMware) - Windows XP. As a debugger take Syser, choose our driver and click Load. The system stops and we go to the debugger:


We are in the beginning of the function DriverEntry. The first "CALL" corresponds to a function call Init. If we follow step by step (F8) what's inside, we see how to complete the structure and called RtlInitUnicodeString for the device name and a symbolic link. The second "CALL" corresponds to the function "NT_SUCCESS", look it returns TRUE (in the register EAX) and code jumps after checking (TEST EAX, EAX) zero (False) on:


As can be seen code pushes the stack parameters for the IoCreateDevice from last to first using the instructions "PUSH". We start checking parameters. Check the name of the device (the third parameter - PUSH 0f8a2c010), for example, type "d 0f8a2c010" (which means to view a memory dump at f8a2c010, addresses are valid only for the current debugging) and see the contents:


the first 8 bytes - this is our variable DeviceName. The first two words - respectively the length of the line and the maximum length of the string in bytes. Next double word - a pointer to a string, look (d f8a2c0d8 consider the byte order little-endian):


there Unicode string with the name of the device. If you look at parameter Device (last output parameter - PUSH 0f8a2c020), we can see that it is different from the name on the 0x10 byte. Now look at the declaration of variables, the variable "Device" is declared after the DeviceName and DeviceLink, a total length of 8 + 8 = 0x10 bytes. Ie the order of the variables in the memory corresponds to the order in the ad code. Check the first non-const parameter ESI, in the beginning it is copied to the value at ESP + 0xC. Register ESP - points to the top of the stack. If you walk to the top function DriverEntry, you can see the preservation of the stack of two registers ESI and EDI (by agreement StdCall these registers are saved in the list, ie, the procedure should not change them after the call). DriverObject transmitted in the first variable, i.e. closest to the top of the stack, and after all the settings saved return address - ie DriverObject parameter before executing the first instruction in the DriverEntry function is located at ESP + 4 (the stack grows downward addresses), after two instructions "PUSH" he accordingly shifted by 8 bytes, as a result DriverObject located at ESP + 0C, all right . Correct settings, you can call the function. Hit F10 to not go inside and look IoCreateDevice value of the EAX register after the call, there must be a non-negative integer that indicates that the function worked without error. I have it returned 0 (STATUS_SUCCESS), everything is fine. Next comes the familiar procedure at 0xF8A2B750 - NT_SUCCESS:


If successful, go jump on 0xf8a2b7bf, where there is the pushing of the stack parameters for the function IoCreateSymbolicLink. Parameter DeviceName we have checked, check DeviceLink:


What you need. Hit F10, test EAX, if successful go further if it fails, remove the device and exit with an error. Procedure at 0xf8a2bbb0 - it GetAddr, which simply returns its this value:


Next there is copying of addresses at offsets DriverObject, if you look at the declaration you can see that at offset 0x34 is written address DriverUnload, at offset 0x38 - MajorFunction (0), etc. Recorded values correspond to the address of the function in our driver. Then there is zero EAX (the returned value) and exit from the procedure DriverEntry. Everything works without error, go ahead. So, to track the performance of the driver we will put a breakpoint on the function DriverDeviceControl. Address it is possible to take on the newly written offsets in the structure of DRIVER_OBJECT or find easy viewing and by analyzing the code. In my test, the address is 0xf8a2b870, go to him (. 0xf8a2b870) and press F9, set breakpoints. On the contrary instructions to set a marker:


Now, when this function is called the debugger will stop code execution and enables us to step through the code. Function "DriverCreateClose" and "DriverUnload" I will not describe, because everything is simple. Hit F5, thereby continuing to perform normally. We were immediately transferred back to Windows. Now we run our test application, enter any address (eg 81234567) and click on the button Read. Our challenge intercepts debugger and we can continue to test the function code DriverDeviceControl. Details inside I will not describe the code will focus on the copy:


Immediately look at the stack (register ESP), we see that the correct parameters are passed. In any case, do a dump, then compare:


Press F5 - and return to Windows. We look at the dump is already in our program:


As you can see everything is fine copy. Let's try to copy the data to a page boundary, so that one page was missing. Experimental method was found such a page that's what we get:


As we can see that the data is copied correctly, which did not work there, we displayed a question mark. The output parameter DeviceIoControl we actually returns the number of bytes read, we use it to display a question mark. _________________________________________________________________
As you can see on VB6, you can write a simple driver, and if you use inline assembly can be more serious and write something. Thank you for your attention. Good Luck!

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4/14/2019 8:31:07 AMThomas Sturm

Visual Basic set books
If anyone was to write a book about Visual Basic nowadays they would have to add a chapter (at least) based on this tutorial. I have never read anything as surprising and informative in computer science before. In fact, If anyone was to write a book about Visual Basic nowadays it should be "The trick" - put me down for a firm order already.
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