redirect.js

/*
 * Copyright (c) 2014-2020 Bjoern Kimminich.
 * SPDX-License-Identifier: MIT
 */

const utils = require('../lib/utils')
const insecurity = require('../lib/insecurity')
const challenges = require('../data/datacache').challenges

module.exports = function performRedirect () {
  return ({ query }, res, next) => {
    const toUrl = query.to
    if (insecurity.isRedirectAllowed(toUrl)) {
      utils.solveIf(challenges.redirectCryptoCurrencyChallenge, () => { return toUrl === 'https://explorer.dash.org/address/Xr556RzuwX6hg5EGpkybbv5RanJoZN17kW' || toUrl === 'https://blockchain.info/address/1AbKfgvw9psQ41NbLi8kufDQTezwG8DRZm' || toUrl === 'https://etherscan.io/address/0x0f933ab9fcaaa782d0279c300d73750e1311eae6' })
      utils.solveIf(challenges.redirectChallenge, () => { return isUnintendedRedirect(toUrl) })
      res.redirect(toUrl)
    } else {
      res.status(406)
      next(new Error('Unrecognized target URL for redirect: ' + toUrl))
    }
  }
}

function isUnintendedRedirect (toUrl) {
  let unintended = true
  for (const allowedUrl of insecurity.redirectWhitelist) {
    unintended = unintended && !utils.startsWith(toUrl, allowedUrl)
  }
  return unintended
}