blog.crox.net

I'm trying out the "Nextcloud Office" app together with "Collabora Online - Built-in CODE Server". That Nextcloud instance is behind a reverse proxy.

The problem I encountered was that regardless of the 'overwritehost' and 'overwriteprotocol' settings, the WOPI URL kept being automatically changed from https to http.

From other posts regarding similar issues I figured out that the WOPI URL is obtained by querying https://[yourinstance]/apps/richdocumentscode/proxy.php?req=/hosting/discovery

Looking at the proxy.php source code, I found the reason for the issue:

// URL into this server of the proxy script.
if ((isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off')
        || (isset($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https' )
        || (isset($_SERVER['HTTP_X_FORWARDED_SSL']) && $_SERVER['HTTP_X_FORWARDED_SSL'] === 'on')
) { 
    $proxyURL = "https://";
} else {
    $proxyURL = "http://";
}

I then modified my reverse proxy (Apache) config to add the missing header:

RequestHeader set X-Forwarded-Proto "https"

Now everything works as expected