web.config - use current page protocol (http/https) as a variable in a redirect rule

Question

On my web.config file, first I need to redirect users requesting URL on http to https. Then, afterwards, I need to do further stuff, I need to make sure www is there in the beginning of the URL. When redirecting users from non-www to www, I want to use the https already set on the previous rule. But I want to do it dinamically, I don't want to hardcode 'https://' on the beginning of my rewrite rule.

The goal is: in the future, if for some reason I need to change this rule from https back to http (I don't think I will, but I may need this), I don't have to go on checking all the redirect rules below to change from 'https' to 'http'. If I use a variable (not sure I should call things inside brackets like {HTTPS} as 'variables'), all I have to do is change the first rule and ignore the rest.

Here is an example so things can get clearer; the key issue I am trying to solve is the item where I have written {WHAT TO USE HERE TO MAKE SURE I USE THE SAME PROTOCOL (HTTP/HTTPS) ALREADY DEFINED ABOVE?}:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <location path="." inheritInChildApplications="false">
    <system.webServer>
      <rewrite>
        <rules>
          <!-- The first rule will do a 301 redirect to https -->
          <rule name="Redirect to https" stopProcessing="false">
            <match url="(.*)" />
            <conditions>
              <add input="{HTTPS}" pattern="off" ignoreCase="true" />
            </conditions>
            <action type="Redirect" url="https://{HTTP_HOST}{REQUEST_URI}" redirectType="Permanent" appendQueryString="false" />
          </rule>

          <!-- Now, let's make sure we have www if request does not carry it -->
          <rule name="Redirect to www" stopProcessing="false">
            <match url="(.*)" />
            <conditions trackAllCaptures="false">
              <add input="{HTTP_HOST}" pattern="^mydomain.com$" />
            </conditions>
            <action type="Redirect" url="{WHAT TO USE HERE TO MAKE SURE I USE THE SAME PROTOCOL (HTTP/HTTPS) ALREADY DEFINED ABOVE?}www.mydomain.com/{R:1}" />
          </rule>              
        </rules>
      </rewrite>
    </system.webServer>
  </location>
</configuration>

Thank you so much, any help appreciated.

Victor Leontyev Victor Leontyev · Accepted Answer · 2017-06-12T19:08:14

Best way is to use rewrite map to identify protocol. In your case it will be like that:

<rewrite>
    <rules>
        <rule name="Redirect to www" stopProcessing="false">
            <match url="(.*)" />
            <conditions trackAllCaptures="false">
                <add input="{HTTP_HOST}" pattern="^mydomain.com$" />
            </conditions>
            <action type="Redirect" url="{MapProtocol:{HTTPS}}://www.mydomain.com/{R:1}" />
        </rule>   
    </rules>
    <rewriteMaps>
        <rewriteMap name="MapProtocol">
            <add key="on" value="https" />
            <add key="off" value="http" />
    </rewriteMap>
    </rewriteMaps>
</rewrite>

web.config - use current page protocol (http/https) as a variable in a redirect rule

1 Answers