When Wordpress is behind reverse proxy, it will think and reply only to HTTP only instead of HTTPS. But the original request from the reverse proxy will HTTPS, causing a mismatch.
To fix this issue, we simply need to trick Wordpress to think that it is running as HTTPS instead of HTTP.
The reverse proxy will pass the variables:
HTTP_X_FORWARDED_PROTO
Adding the following to wp-config.php will trick Wordpress to think it is running HTTPS:
if (!empty($_SERVER['HTTP_X_FORWARDED_PROTO']) && $_SERVER['HTTP_X_FORWARDED_PROTO'] === 'https') {
$_SERVER['HTTPS'] = 'on';
}
