Windows Authentication in winform Application

Today one of my friend asked me how we can perform validating user windows login credentials. In past also i saw in many forums people asking similar questions.

actaully there are 2 different scenarios

1) Get the currently logged in windows user name.

2) Prompt the user for user and password, and validate the provided user name and password are a valid user credentials

following is the c# code which will answer these scenarios.

1)  Get currently logged in user details: This is pretty straight forward approach. We can achieve this by using the WindowsIdentity class of System.Security.Principal namespace. This class provides a static method, getCurrent(), which return a object of WindowsIdentity.

Bellow is the code you can use to get the current logged in user details.

public string GetloggedinUserName() {
  System.Security.Principal.WindowsIdentity currentUser =
      System.Security.Principal.WindowsIdentity.GetCurrent();
  return currentUser.Name;
}

2) Validate windows credentials provided by user: This is little complex compared to above as we need to call a windows API using IntropServices. To accomplish this we need to add a extern function declaration, and then call the function. Following code will help you to understand this better.

class Program {
  [System.Runtime.InteropServices.DllImport("advapi32.dll")]
  public static extern bool LogonUser(string userName, string domainName,
                                      string password, int LogonType,
                                      int LogonProvider, ref IntPtr phToken);

  static void Main(string[] args) {
    Program obj = new Program();
    bool isValid =
        obj.IsValidateCredentials("myUserName", "MyPassword", "MyDomain");
    Console.WriteLine(isValid == true ? "Valid User details"
                                      : "Invalid User Details");
    Console.Read();
  }

  public bool IsValidateCredentials(string userName, string password,
                                    string domain) {
    IntPtr tokenHandler = IntPtr.Zero;
    bool isValid =
        LogonUser(userName, domain, password, 2, 0, ref tokenHandler);
    return isValid;
  }
}

Hope this will be useful for people who want to perform windows authentication in winform applications…

Happy coding  

posted on Tuesday, July 14, 2009 6:08 AM