How to prevent anonymous users from accessing a file using forms authentication?

Question

We are using forms authentication to authenticate users. In our application there is a page to download an exe.

When I am debugging the code in visual studio, it allows only logged-in users to download the file. When other users try to download the file, they are automatically redirected to the login page.

But when I am running this from a virtual directory, all users (whether logged-in or not) can download the file by accessing the direct path like http://testappln/foldername/test.exe.

How to prevent accessing of unauthorized users in this situation?

Answer 1

One possibility is to put the file inside the App_Data folder which is forbidden direct access to and then have a generic ASHX handler to read the contents of the file and return it to the client. Then you could restrict the access to this generic handler to only authenticated users:

<%@ WebHandler Language="C#" Class="Download" %>

using System;
using System.Web;

public class Download : IHttpHandler 
{
    public void ProcessRequest (HttpContext context) 
    {
        context.Response.ContentType = "application/octet-stream";
        context.Response.WriteFile("~/App_Data/test.exe");
    }

    public bool IsReusable 
    {
        get 
        {
            return false;
        }
    }
}

and in your web.config you restrict the access to the Download.ashx handler:

<location path="Download.ashx">
    <system.web>
        <authorization>
            <deny users="?"/>
        </authorization>
    </system.web>
</location>