Is it possible to replace content on every page passed through a proxy similar to how mod_rewrite is used for URLs?

Solution 1:

There's an apache module called mod_substitute that can do this. Here's a short example:

<Location "/">
    AddOutputFilterByType SUBSTITUTE text/html
    Substitute "s/"

Or, when combined with mod_proxy:

ProxyPass /
ProxyPassReverse /

Substitute "s|||i"

There's more information at the Apache documentation for mod_substitute.

Solution 2:

If you haven't restarted Apache, be sure to do that, but if you've already done so, you could try a global output filter that runs a custom PHP script to do your replacing just to see if that solves it for some reason.

EDIT: based on your comment, it could be that substitute isn't working because the content is compressed. To turn off compression, add these lines to your VirtualHost:

RequestHeader unset Accept-Encoding
RequestHeader set Accept-Encoding identity

If that doesn't work, try the following:

Add these to your conf, updating the paths of course:

#add this outside of any VirtualHost tags
ExtFilterDefine proxiedcontentfilter mode=output cmd="/usr/bin/php /var/www/proxyfilter.php"

#add these in your VirtualHost tag
RequestHeader unset Accept-Encoding 
RequestHeader set Accept-Encoding identity
SetOutputFilter proxiedcontentfilter

In proxyfilter.php have some code like the following:

$html = file_get_contents('php://stdin');
$html = str_ireplace('', '', $html);
file_put_contents('php://stdout', $html);

If this works, then narrow the focus of this to just text/html content as you have in your example.