fugadalcontrollo/routes/tor.js

const { promisify } = require('util')
const dns = require('dns')
const lookup = promisify(dns.lookup)

// https://www.torproject.org/projects/tordnsel.html.en
// check if request comes from tor
module.exports = async (req, res, next) => {
  const source_ip = req.headers['x-forwarded-for'] || req.connection.remoteAddress
  const ip = source_ip.split('.').reverse().join('.')
  const server_ip = '51.68.126.235'.split('.').reverse().join('.')
  const domain = `${ip}.80.${server_ip}.ip-port.exitlist.torproject.org`
  try {
    const ret = await lookup(domain, {})
    req.fromTor = (ret.address === '127.0.0.2')
  } catch(e) {
    req.fromTor = false
  }
  next()
}