Apache VirtualHost with reverse proxy

This post documents the process of setting up a reverse proxy to load one (Origin) website in the subdirectory of another. During this process the reverse proxy directives will also append HTML to the head and body of the origin website.

Prerequisites

The instructions below are based on an Apache Linux server running cPanel/ Web Host Manager. The set-up requires the following Apache modules:

mod_proxy
mod_proxy_http
od_include
mod_headers
mod_rewrite
mod_sed

mod_sed is the only uncommon module, however it is only required if you are using the OutputSed directives, if you don't plan on making any modifications to the origin website you can skip it.

VirtualHost

The server will already be preconfigured to listen for additional .conf files for each domain once they're added to the correct directories. For the standard WHM/cPanel/Apache combination:

/etc/apache2/conf.d/userdata/ssl/2_4/$user/$domainname/$file.conf

Where $user is the Linux user account associated with the hosting package, $domainname is your cPanel domain name and $file is the .conf filename.

/etc/apache2/conf.d/userdata/ssl/2_4/example/example.com/reverseproxy.conf

ProxyPass Directives

Inside reverseproxy.conf the Reverse proxy directives are added:

/subdirectory where the origin website will be displayed (could be root "/")
https://origin-website.example.com/ is the origin website

ProxyPreserveHost off
SSLProxyEngine on
SSLProxyVerify off
SSLProxyCheckPeerCN off
SSLProxyCheckPeerName off
SSLProxyCheckPeerExpire off
ProxyPass "/subdirectory" "https://origin-website.example.com/"
ProxyPassReverse "/subdirectory" "https://origin-website.example.com/"

## Stop any existing rewrites on subdirectory
RewriteRule ^(subdirectory)($|/) - [L]

<Location "/subdirectory">

     <IfModule mod_headers.c>
        RequestHeader unset accept-encoding
        Header unset Content-Length
     </IfModule>

     # Add new layout fields
     Options +Includes
     AddOutputFilterByType Sed;INCLUDES text/html
     OutputSed "/<!--#[a-zA-z]/d"
     OutputSed "s/\\(<\/head>\\)/\\<!--#include virtual=\"\/layout\/head.inc.php\"--><\/head>/g"
     OutputSed "s/\\(<body[^>]*>\\)/\\<!--#include virtual=\"\/layout\/header.inc.php\"-->/g"
     OutputSed "s/\\(<\/body>\\)/\\<!--#include virtual=\"\/layout\/footer.inc.php\"--><\/body>/g"

</Location>

The above code will automatically try to include additional files in the pages processed by ProxyPass.

layout/head.inc.php will be appended to the <head>
layout/header.inc.php will be added to the start of <body> tag
layout/footer.inc.php will be added just before the </body> tag

These files can be used to apply style/scripting on top of the code supplied by the proxy.

Rebuild and Restart Apache

Once the reverse proxy directives have been added to the Apache configuration, the live conf file needs to be rebuilt to include the new directives:

/usr/local/cpanel/scripts/rebuildhttpdconf

The rebuild process will flag any errors with the reverse proxy code. These can then be rectified before a successful rebuild.

Then the obligatory Apache restart:

/usr/local/cpanel/scripts/restartsrv_httpd