C# 4 and .NET 4

546 ❘ ChaPTer 21 security
classes that implement the interface IIdentity. With this interface you have access to the name of the user,
information about whether the user is authenticated, and the authentication type.
A principal is an object that contains the identity of the user and the roles that the user belongs to. The
interface IPrincipal defines the property Identity, which returns an IIdentity object, and the method
IsInRole with which you can verify that the user is a member of a specific role. A role is a collection of
users who have the same security permissions, and it is the unit of administration for users. Roles can be
Windows groups or just a collection of strings that you define.
The principal classes available with .NET are WindowsPrincipal and GenericPrincipal. You can also
create a custom principal class that implements the interface IPrincipal.
In the following example, you create a console application that provides access to the principal in an
application that, in turn, enables you to access the underlying Windows account. You need to import the
System.Security.Principal and System.Threading namespaces. First, you must specify that .NET
should automatically hook up the principal with the underlying Windows account. This must be done
because .NET does not automatically populate the thread’s CurrentPrincipal property for security
reasons. You can do it like this:
using System;
using System.Security.Principal;
using System.Threading;
namespace Wrox.ProCSharp.Security
{
class Program
{
static void Main()
{
AppDomain.CurrentDomain.SetPrincipalPolicy(PrincipalPolicy.WindowsPrincipal);
code snippet WindowsPrincipal/Program.cs
It is possible to use WindowsIdentity.GetCurrent() to access the Windows account details; however,
that method is best used when you are going to look at the principal only once. If you want to access the
principal a number of times, it is more efficient to set the policy so that the current thread provides access
to the principal for you. If you use the SetPrincipalPolicy method, it is specified that the principal in
the current thread should hold a WindowsIdentity object. All identity classes, such as WindowsIdentity,
implement the IIdentity interface. The interface contains three properties (AuthenticationType,
IsAuthenticated, and Name) for all derived identity classes to implement.
Add code to access the principal’s properties from the Thread object:
}
}
}
WindowsPrincipal principal =
(WindowsPrincipal)Thread.CurrentPrincipal;
WindowsIdentity identity = (WindowsIdentity)principal.Identity;
Console.WriteLine("IdentityType: " + identity.ToString());
Console.WriteLine("Name: {0}", identity.Name);
Console.WriteLine("'Users': {0} ",
principal.IsInRole(WindowsBuiltInRole.User));
Console.WriteLine("'Administrators' {0}",
principal.IsInRole(WindowsBuiltInRole.Administrator));
Console.WriteLine("Authenticated: {0}", identity.IsAuthenticated);
Console.WriteLine("AuthType: {0}", identity.AuthenticationType);
Console.WriteLine("Anonymous {0}", identity.IsAnonymous);
Console.WriteLine("Token: {0}", identity.Token);
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