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

  • On-demand Event Event Date: May 18, 2015 While the idea of using facial and/or gesture recognition to create a modern, intuitive game seems attractive, some developers may want to leverage Unity 3D as a way to accelerate their development efforts. There are many different ways in which Intel and Unity Technologies have been working together to help speed the development of games with the Intel&reag; RealSense™ SDK (software developer kit). Check out this webcast to join a panel of experts as they …

  • On-Demand eSeminar DevOps and Cloud are all the rage in IT, but the two terms relating process and computing aren't mutually exclusive. Join us to see how your movement into cloud changes the way you develop, deploy, test and manage, and how DevOps can actually be a good thing when coupled with cloud.

Most Popular Programming Stories

More for Developers

RSS Feeds

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