qr code generator asp net c# User and Data Security in Visual C#

Make QR Code ISO/IEC18004 in Visual C# User and Data Security

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the computer agrees that you are who you claim to be. However, it doesn t yet know whether you are allowed to access the resource you are requesting. For example, help desk support staff should have the right to reset a user s password, but members of the accounting department should be able to change only their own passwords. To authorize the user, the computer system typically checks an ACL, which lists users and groups of users who are permitted to access a resource.

The System.Security.Principal.WindowsIdentity class represents a Windows user account. This class provides access to the current user s name, authentication type, and account token. It does not allow you to authenticate a user; Windows has already taken care of the authentication. WindowsIdentity simply stores the results of the authentication, including the user s name and authentication token. Generally, when you create an instance of the WindowsIdentity class, you call one of three methods to create the object:

GetAnonymous Returns a WindowsIdentity object that represents an anony-

mous, unauthenticated Windows user. You can use this method to impersonate an anonymous user to ensure that your code operates without credentials.

GetCurrent Returns a WindowsIdentity object that represents the current Win-

Impersonate Returns a WindowsImpersonationContext object that represents a specified user on the system. You can use this method to impersonate a particular user account when your application has access to the user s credentials.

For example, the following code (which requires the System.Security.Principal namespace) creates a WindowsIdentity object named currentIdentity that represents the current user:

' VB Dim currentIdentity As WindowsIdentity = WindowsIdentity.GetCurrent()

// C# WindowsIdentity currentIdentity = WindowsIdentity.GetCurrent();

After the variable is assigned, you can access several useful properties that provide information about the user:

IsAnonymous A Boolean value set to true if the user is anonymous. IsAuthenticated A Boolean value set to true if the user is authenticated. IsGuest A Boolean value set to true if the user is a guest. IsSystem A Boolean value set to true if the user is part of the system. Name A string representing the authentication domain and user name of the

user, separated by a backslash in the format, DOMAIN\Username . If the user s account is in the local user database, the domain is the machine name. Otherwise, domain represents the name of the Active Directory domain.

Token An integer representing the user s authentication token, assigned by the computer that authenticated the user.

Use the WindowsIdentity class to examine the current user s name and authentication type to determine whether the user is authorized to run privileged portions of your code. Examining objects of this class is useful if, for example, a section of your code displays information that should be available only to authenticated users. The following simple console application (which requires the System.Security.Principal namespace) demonstrates the use of the WindowsIdentity class by displaying information about the current user:

' VB ' Grab the current user Dim currentIdentity As WindowsIdentity = WindowsIdentity.GetCurrent() ' Display the name, token, and authentication type ' for the current user Console.WriteLine("Name: " + currentIdentity.Name) Console.WriteLine("Token: " + currentIdentity.Token.ToString()) Console.WriteLine("Authentication Type: " _ + currentIdentity.AuthenticationType) ' Display information based on Boolean properties of the current user If currentIdentity.IsAnonymous = True Then Console.WriteLine("Is an anonymous user") End If If currentIdentity.IsAuthenticated = True Then Console.WriteLine("Is an authenticated user") End If If currentIdentity.IsSystem = True Then Console.WriteLine("Is part of the system") End If If currentIdentity.IsGuest = True Then Console.WriteLine("Is a guest") End If

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// C# // Grab the current user WindowsIdentity currentIdentity = WindowsIdentity.GetCurrent(); // Display the name, token, and authentication type // for the current user Console.WriteLine("Name: " + currentIdentity.Name); Console.WriteLine("Token: " + currentIdentity.Token.ToString()); Console.WriteLine("Authentication Type: " + currentIdentity.AuthenticationType); // Display information based on Boolean properties of // the current user if (currentIdentity.IsAnonymous) Console.WriteLine("Is an anonymous user"); if (currentIdentity.IsAuthenticated) Console.WriteLine("Is an authenticated user"); if (currentIdentity.IsGuest) Console.WriteLine("Is a guest"); if (currentIdentity.IsSystem) Console.WriteLine("Is part of the system");