Implementing .NET Security in C#

-->

Environment: C#, .NET

Since my company, Harrissoft.co.uk, does a lot of .NET consultancy, one of our recent projects required that file i/o access be denied if the user running the application did not have administrator privileges. A lot has been written about the command line utility caspol.exe, however, this can seem a little over the top and quite complex when considering code groups, policy levels and zone management.

I basically wanted to programmatically check whether the user had the relevant permissions by accessing their windows account. Fortunately, .NET provides this through the System.Security.Principal namespace. I also wanted to deny access to particular drives - this is done through the namespace System.Security.Permissions.

Below is a skeleton example, where if the user is not an administrator the contents of a text file cannot be read and displayed in a list box:

try
{
  // By default deny access to the C Drive.....
  CodeAccessPermission UserPermission = 
     new FileIOPermission(FileIOPermissionAccess.AllAccess,@"c:\");

  //Check whether the user is part of the administrator group
  AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal);
  WindowsPrincipal principal = (WindowsPrincipal)Thread.CurrentPrincipal;
  WindowsIdentity identity = (WindowsIdentity)principal.Identity;
  
  bIsAdmin = principal.IsInRole(WindowsBuiltInRole.Administrator);

  //It's not, so deny access to the file
  if(!bIsAdmin)
  {
    UserPermission.Deny();
  }
  else
  {
    //Do the read
    din = ReadTheFile.DoTheRead();
  }

  if(!bIsAdmin)
  {
    //Reset deny permissions in  current stack frame
    CodeAccessPermission.RevertDeny();
  }

  //If we got this far .... we read in the file
  String str;
  
  while ((str=din.ReadLine()) != null) 
  {
    listBox1.Items.Add(str);
  }
}
catch (SecurityException exception)
{
  //Failed to pass the security checks - so flag up error to user 
  listBox1.Items.Add("Permission denied accessing file");
}

The zip download file contains the .NET project so you can build and run this example.

If you have any comments on this article please email: simonharris@harrissoft.co.uk

Downloads

Download demo project - 22 Kb


Comments

  • I did'nt see that

    Posted by Legacy on 06/05/2002 12:00am

    Originally posted by: sdfs

    I did'nt see that

    Reply
  • good , very useful

    Posted by Legacy on 04/29/2002 12:00am

    Originally posted by: Transbuerg Tian

    good , very useful

    Reply
Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • U.S. companies are desperately trying to recruit and hire skilled software engineers and developers, but there is simply not enough quality talent to go around. Tiempo Development is a nearshore software development company. Our headquarters are in AZ, but we are a pioneer and leader in outsourcing to Mexico, based on our three software development centers there. We have a proven process and we are experts at providing our customers with powerful solutions. We transform ideas into reality.

  • When individual departments procure cloud service for their own use, they usually don't consider the hazardous organization-wide implications. Read this paper to learn best practices for setting up an internal, IT-based cloud brokerage function that service the entire organization. Find out how this approach enables you to retain top-down visibility and control of network security and manage the impact of cloud traffic on your WAN.

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date