handleopen.c

NTSTATUS HandleOpen(PDEVICE_OBJECT DeviceObject, IRP *Irp)
{
  NTSTATUS ntStatus;
  BOOL bAllowed;
  PIO_SECURITY_CONTEXT SecurityContext; 
  PACCESS_STATE AccessState; 
  PACCESS_TOKEN Token;
  DWORD IsTokenElevated; 
  DWORD tokenIntegrityLevel;
  PTOKEN_ELEVATION tokenElevation; 
  
  ntStatus = STATUS_SUCCESS;
  bAllowed = TRUE;
  
  UNREFERENCED_PARAMETE(DeviceObject);

  if ( Irp->RequestorMode == UserMode )                
  {
    SecurityContext = Irp->Tail.Overlay.CurrentStackLocation->Parameters.Create.SecurityContext;
    if ( SecurityContext
      && (AccessState = SecurityContext->AccessState) != NULL
      && ((Token = AccessState->SubjectSecurityContext.ClientToken) != NULL
       || (Token = AccessState->SubjectSecurityContext.PrimaryToken) != NULL) )
    {
      tokenElevation = NULL;
      ntStatus = SeQueryInformationToken(Token, TokenElevation, &tokenElevation);
      if ( NT_SUCCESS(ntStatus) )
      {
        IsTokenElevated = tokenElevation->TokenIsElevated;
        ExFreePoolWithTag(tokenElevation, 0);
        tokenIntegrityLevel = 0;
        ntStatus = SeQueryInformationToken(Token, TokenIntegrityLevel, &tokenIntegrityLevel);
        if ( NT_SUCCESS(ntStatus) )
        {
          if ( !IsTokenElevated || tokenIntegrityLevel < SECURITY_MANDATORY_HIGH_RID )
            bAllowed = 0;
          ntStatus = (bAllowed == 0) ? STATUS_ACCESS_DENIED : STATUS_SUCCESS;
        }
      }
    }
    else
    {
      ntStatus = STATUS_ACCESS_DENIED;
    }
  }
  Irp->IoStatus.Information = 0i64;
  Irp->IoStatus.Status = ntStatus;
  IofCompleteRequest(Irp, 0);
  return ntStatus;
}