The Best Way to Force HTTPS for Your Entire ASP.NET Site

Ensuring that your website operates over a secure connection is essential not only for protecting user data but also for building trust with your audience. Many developers face the challenge of enforcing HTTPS across all pages of their ASP.NET site. Traditionally, developers used on-page checks during the loading events to redirect users to HTTPS. This method, while functional, can be tedious and inefficient.

In this blog post, we’ll explore a more streamlined solution to ensure every request to your ASP.NET site is conducted over HTTPS.

The Problem with HTTPS Redirection

About six months ago, a developer rolled out a website that required every page to be accessed securely over HTTPS. The common solution was to check whether the current request was secure during the page load event, and then manually redirect to the HTTPS version of the site if it wasn’t.

Here’s a basic example of that traditional approach:

protected void Application_BeginRequest(Object sender, EventArgs e)
{
   if (HttpContext.Current.Request.IsSecureConnection.Equals(false) && !HttpContext.Current.Request.IsLocal)
   {
    Response.Redirect("https://" + Request.ServerVariables["HTTP_HOST"] + HttpContext.Current.Request.RawUrl);
   }
}

While this method works, it can be cumbersome and may add unnecessary overhead.

A Better Solution: HTTP Strict Transport Security (HSTS)

A much more efficient approach is to implement HTTP Strict Transport Security (HSTS), which instructs browsers to always use HTTPS for your site. This not only simplifies your configuration but also enhances the security of your web application.

Steps to Implement HSTS in Your ASP.NET Site

1. Update Your Web.Config File: You can enforce HTTPS and implement HSTS through your web.config by using URL rewrites. Here’s how you can do this:

   <?xml version="1.0" encoding="UTF-8"?>
   <configuration>
       <system.webServer>
           <rewrite>
               <rules>
                   <rule name="HTTP to HTTPS redirect" stopProcessing="true">
                       <match url="(.*)" />
                       <conditions>
                           <add input="{HTTPS}" pattern="off" ignoreCase="true" />
                       </conditions>
                       <action type="Redirect" url="https://{HTTP_HOST}/{R:1}" redirectType="Permanent" />
                   </rule>
               </rules>
               <outboundRules>
                   <rule name="Add Strict-Transport-Security when HTTPS" enabled="true">
                       <match serverVariable="RESPONSE_Strict_Transport_Security" pattern=".*" />
                       <conditions>
                           <add input="{HTTPS}" pattern="on" ignoreCase="true" />
                       </conditions>
                       <action type="Rewrite" value="max-age=31536000" />
                   </rule>
               </outboundRules>
           </rewrite>
       </system.webServer>
   </configuration>
   

   Breakdown of the Configuration:

   • HTTP to HTTPS redirect: This rule checks if the request is not secure (HTTP) and redirects it to HTTPS.
   • Strict-Transport-Security: This rule adds the HSTS header to responses served over HTTPS, specifying how long browsers should remember to always use HTTPS (in this example, 31536000 seconds, which is equivalent to one year).

2. Verify Your Implementation: Once you have configured the settings, test your site to ensure that all requests are being redirected to HTTPS. Also, check the response headers to ensure that the Strict-Transport-Security header is present.

Conclusion

By implementing HSTS through your web.config file, you streamline the security of your ASP.NET applications significantly. This method not only saves resources but also enhances user security by ensuring that all connections to your site are performed over HTTPS.

Adopting these best practices is vital in today’s web environment, where security is paramount. Simplify your code, enhance security, and provide your users with a safer browsing experience!

If you have any questions or additional tips regarding HTTPS implementation, feel free to share in the comments below.