mod_md: some strong advice about the consequences of permanent MDRequireHttps in the manual

                </highlight>

            </example>

            <p>you announce that you want all traffic via http: URLs to be redirected 

            to the https: ones, for now. If you want client to no longer use the

            to the https: ones, for now. This is safe and you can remove this again at

            any time.

            </p><p>

                <strong>The following has consequences: </strong>if you want client to <strong>no longer</strong> use the

             http: URLs, configure:

            </p>

            <example><title>Example</title>

            <example><title>Permanent (for at least half a year!)</title>

                <highlight language="config">

MDRequireHttps permanent                

                </highlight>

            </example>

            <p>This does two things:

            </p>

            <ol>

                <li>All request to the <code>http:</code> resources are redirected to the

                    same url with the <code>https:</code> scheme using the <code>301</code>

                status code. This tells clients that this is intended to be forever and

                the should update any links they have accodingly.

                </li>

                <li>All answers to <code>https:</code> requests will carry the header

                    <code>Strict-Transport-Security</code> with a life time of half a year.

                    This tells the browser that it <strong>never</strong> (for half a year) shall use <code>http:</code>

                    when talking to this domain name. Browsers will, after having seen this, refuse

                    to contact your unencrypted site. This prevents malicious middleware to

                    downgrade connections and listen/manipulate the traffic. Which is good. But

                    you cannot simply take it back again.

                </li>

            </ol>

            <p>You can achieve the same with mod_alias and some Redirect configuration,

            basically. If you do it yourself, please make sure to exclude the paths 

            /.well-known/* from your redirection, otherwise mod_md might have trouble 

            <example><title>Example</title>

                <highlight language="config">

<ManagedDomain xxx.yyy>

  MDRequireHttps permanent

  MDRequireHttps temporary

</ManagedDomain>

                </highlight>

            </example>

            <p>When you configure MDRequireHttps permanent, an additional security 

            feature is automatically applied: HSTS. This adds the header 

            Strict-Transport-Security to responses sent out via https:. 

            Basically, this instructs the browser to only perform secure 

            communications with that domain. This instruction holds for the 

            amount of time specified in the header as 'max-age'. 

            This is about half a year as generated by mod_md.

            </p><p>

            It is therefore advisable to first test the MDRequireHttps temporary 

            configuration and switch to permanent only once that works satisfactory.

            </p>

        </usage>

    </directivesynopsis>