ghost/core/frontend/services/theme-engine/middleware/update-local-template-data.js

function updateLocalTemplateData(req, res, next) {
    // Pass 'secure' flag to the view engine
    // so that templates can choose to render https or http 'url', see url utility
    res.locals.secure = req.secure;

    next();
}

module.exports = updateLocalTemplateData;