How to Securely Enforce HTTPS Site-Wide in ASP.NET?

Enforcing HTTPS Site-Wide in ASP.NET

Background: Several months ago, a site was implemented where all requests were required to be made over HTTPS. The only viable solution at the time involved checking the request during the page load event and redirecting to HTTPS if necessary.

Alternative Solution:

A more robust approach is to utilize HTTP Strict Transport Security (HSTS). By implementing HSTS, you can prevent unsecured HTTP requests and enforce HTTPS connections for a specified period.

Web.config Configuration:

To configure HSTS in ASP.NET, add the following code to the section of your web.config file:

<rewrite>
  <rules>
    <rule name="HTTP to HTTPS redirect" stopprocessing="true">
      <match url="(.*)"></match>
      <conditions>
        <add input="{HTTPS}" pattern="off" ignorecase="true"></add>
      </conditions>
      <action type="Redirect" url="https://{HTTP_HOST}/{R:1}" redirecttype="Permanent"></action>
    </rule>
  </rules>
  <outboundrules>
    <rule name="Add Strict-Transport-Security when HTTPS" enabled="true">
      <match servervariable="RESPONSE_Strict_Transport_Security" pattern=".*"></match>
      <conditions>
        <add input="{HTTPS}" pattern="on" ignorecase="true"></add>
      </conditions>
      <action type="Rewrite" value="max-age=31536000"></action>
    </rule>
  </outboundrules>
</rewrite>

Global.asax.cs Code (Alternative Method):

While HSTS is the recommended approach, an alternative solution involves adding the following code to the Application_BeginRequest event in Global.asax.cs:

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

Comparison:

Using HSTS offers the advantage of securing HTTPS connections at the browser level, whereas the code-based approach in Global.asax.cs handles the redirection only within the ASP.NET application. HSTS is, therefore, a more comprehensive and recommended solution.

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