ASP.Net's Built-in Web Security

Securing files and folders has always been an option for web applications, but in the past it was necessary to use either a third-party tool like Authentix or to use NTFS and Windows user accounts.
Security with ASP.Net is configured from within the web.config file. This is a standard ASCII file, with an XML format, that is located in the root of your web application. Here is a sample web.config file:




















The very first line is standard for a web.config file and has no bearing on the security.
The next section specifies that you are configuring the security for this web application. First we set the authentication mode to use a cookie in this specific example. You can specify a unique name for your cookie. In ASP.Net Beta 1 you could also set a decryption key but this is now controlled at the server-level in the machine.config file. This section also specifies the page or URL that will contain the authentication code (login.aspx in this case) and how long the authentication cookie should be persisted.
The next two lines specify valid usernames and passwords for this web application. As far as I know there is no limit to the number of user accounts you can place in the web.config, but if there were a large number - or if they change frequently - it might be better to place this information in an external file like a database or an XML file instead (I'll show this in a future article).
Now that we have specified some valid logon accounts, we need to actually specify that we want to password protect. For this example I have decided to password protect a folder under the web root named "admin". The "location path" attribute specifies this folder as the one we will manage. Once we have specified the path to manage, we can work with specific settings - we are interested in the "authorization" setting for this folder. We set the authorization to deny all non-authenticated users (deny users="?").
For the config.web, that is all that is needed. If someone tries to access the /admin/ folder and the user has not already authenticated, they will be redirected to the /login.aspx page.
Now of course this is only half the battle. We now need to create the login.aspx page to actually allow the user to authenticate to our application.
Here is the complete source of the sample login.aspx page:
<%@Page Language="VB" Trace="false"%>
<%@ Import Namespace="System.Web.Security" %>



Username:

Password: