DeleteNullRegValue.py

from ctypes import *
from ctypes.wintypes import *
import winreg


NTSTATUS = c_long 
PVOID = c_void_p
PWSTR = c_wchar_p

OBJ_CASE_INSENSITIVE = 0x00000040
STATUS_SUCCESS = NTSTATUS(0x00000000).value

class UNICODE_STRING(Structure): 
    _fields_ = [('Length', USHORT), 
                ('MaximumLength', USHORT), 
                ('Buffer', PWSTR)]

class OBJECT_ATTRIBUTES(Structure):
    _fields_ = [('Length', ULONG),
                ('RootDirectory', HANDLE),
                ('ObjectName', POINTER(UNICODE_STRING)),
                ('Attributes', ULONG),
                ('SecurityDescriptor', PVOID),
                ('SecurityQualityOfService', PVOID)]

def InitializeObjectAttributes(InitializedAttributes,
                               ObjectName,
                               Attributes,
                               RootDirectory=None,
                               SecurityDescriptor=None):
    """
    Initializes the OBJECT_ATTRIBUTES structure which specifies the properties of an object
    handle to routines that open handles.

    VOID InitializeObjectAttributes(
        [out]          POBJECT_ATTRIBUTES   InitializedAttributes,
        [in]           PUNICODE_STRING      ObjectName,
        [in]           ULONG                Attributes,
        [in]           HANDLE               RootDirectory,
        [in, optional] PSECURITY_DESCRIPTOR SecurityDescriptor);
    """
    memset(addressof(InitializedAttributes), 0, sizeof(InitializedAttributes))
    
    InitializedAttributes.Length = sizeof(InitializedAttributes)
    InitializedAttributes.ObjectName = ObjectName
    InitializedAttributes.Attributes = Attributes
    InitializedAttributes.RootDirectory = RootDirectory
    InitializedAttributes.SecurityDescriptor = SecurityDescriptor
    InitializedAttributes.SecurityQualityOfService = None
    
    return

def RtlUnicodeStringInit(DestinationString, Src):
    """
    Initializes a UNICODE_STRING structure.
    
    NTSTATUS RtlUnicodeStringInit(
        [out] PUNICODE_STRING  DestinationString,
        [in]  PCWSTR           pszSrc)
    """
    memset(addressof(DestinationString), 0, sizeof(DestinationString))

    DestinationString.Buffer = cast(Src, PWSTR)
    DestinationString.Length = sizeof(Src)
    DestinationString.MaximumLength = DestinationString.Length
    
    return STATUS_SUCCESS

def main():
    ntdll = WinDLL('ntdll')

    '''
    NTSTATUS ZwOpenKey(
      _Out_ PHANDLE            KeyHandle,
      _In_  ACCESS_MASK        DesiredAccess,
      _In_  POBJECT_ATTRIBUTES ObjectAttributes);
    '''
    hKey = HANDLE()
    DesiredAccess = winreg.KEY_ALL_ACCESS
    
    # Create ObjectName structure
    ObjectName = UNICODE_STRING()
    strKeyPath = '\\Registry\\Machine\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Run\\'
    bufKeyPath = create_unicode_buffer(strKeyPath)
    NtStatus = RtlUnicodeStringInit(ObjectName, bufKeyPath)
    if NtStatus != STATUS_SUCCESS:
        raise WindowsError('RtlUnicodeStringInit failed and returned {!r}'.format(NtStatus))
    
    # Create ObjectAttributes structure
    ObjectAttributes = OBJECT_ATTRIBUTES()
    InitializeObjectAttributes(ObjectAttributes, pointer(ObjectName), OBJ_CASE_INSENSITIVE)

    # Get handle to the desired key
    NtStatus = ntdll.ZwOpenKey(pointer(hKey), DesiredAccess, ObjectAttributes)
    if NtStatus != STATUS_SUCCESS:
        raise WindowsError('ZwOpenKey failed and returned {!r}'.format(NtStatus))

    '''
    NTSTATUS ZwDeleteValueKey(
        _In_ HANDLE          KeyHandle,
        _In_ PUNICODE_STRING ValueName);
    '''
    # Create ValueName structure
    ValueName = UNICODE_STRING()
    strValueName = '\0HuntressLabs'
    bufValueName = create_unicode_buffer(strValueName)
    NtStatus = RtlUnicodeStringInit(ValueName, bufValueName)
    if NtStatus != STATUS_SUCCESS:
        raise WindowsError('RtlUnicodeStringInit failed and returned {!r}'.format(NtStatus))
    
    # Delete the desired value
    NtStatus = ntdll.ZwDeleteValueKey(hKey, 
                                      pointer(ValueName))
    if NtStatus != STATUS_SUCCESS:
        raise WindowsError('ZwDeleteValueKey failed and returned {!r}'.format(NtStatus))

    ntdll.ZwClose(hKey)

if __name__ == '__main__':
    main()