How to Store the Authenticated User Name in a Session Variable (196074)

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Typically, when permissions are applied to a Web page and a client browses the page, a status code of 401 is returned to the browser and it displays a logon dialog. When the user enters a name and password, the client is either allowed to enter the site or denied access. If the user is allowed access, the server environment variable named LOGON_USER will contain the user name as entered by the client.

The following example simulates when permissions are applied to a Web page by checking this variable and returning a 401 status if it is empty. If the user has been authenticated, then it stores the user name in a session variable so it can be used later without having to force authentication.

Paste the following ASP code into Notepad and save the file in the root directory of your Web site as "401LogonUser.inc" (without the quotation marks):

<%
  ' Check to see if the session variable is already populated.
  If Session("LOGON_USER") = "" Then
    ' Check to see if the user has logged on at all.
    If Request.ServerVariables("LOGON_USER") = "" Then
      ' Force authentication if not.
      Response.Clear
      Response.Status = "401 Access Denied"
      Response.End
    Else
      ' Store the client's user name in a session variable.
      Session("LOGON_USER") = Request.ServerVariables("LOGON_USER")
      ' Strip out an NT domain from the user name.
      If InStr(Session("LOGON_USER"),"\") then
        Session("LOGON_USER") = Mid(Session("LOGON_USER"),InStr(Session("LOGON_USER"),"\")+1)

      End If
    End If
  End If
%>

Then include the following code at the very top of (at least) the first ASP page that needs the variable:

   <%@ LANGUAGE="VBSCRIPT"%>
   <!--#include virtual="/401LogonUser.inc"-->

You can include the code on every page if you want to be sure that a client has bypassed the starting page for a Web site or Web application.

When the variable has been populated, you can then reference it when you need it, as follows:

   <% somevariable = Session("LOGON_USER") %>

You can also force the authentication process at any time by abandoning the session:

   <%Session.Abandon%>

The following page illustrates the above examples in a page that will set the timeout to one minute, authenticate the user, and then authenticate the user if the page is refreshed after being left idle for the one minute timeout.

NOTE: Even after abandoning the session, the browser is still holding the logon credentials.

   <%@ LANGUAGE="VBSCRIPT"%>
   <%Session.Timeout = 1%>
   <!--#include virtual="/401LogonUser.inc"-->
   <html>
   <head><title>LOGON_USER Test</title></head>
   <body>
   Hello <%=UCase(Session("LOGON_USER"))%>!
   </body>
   </html>

How to Store the Authenticated User Name in a Session Variable (196074)

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