index.js

/*jshint node:true*/
'use strict';
module.exports = {
  backend: function evercookieMiddlewareBackendFactory(opts) {
    opts = opts || {};
    var defaultOptionMap = {
      etagCookieName: 'evercookie_etag',
      cacheCookieName: 'evercookie_cache',
      authPath: '/evercookie_auth.php',
      pngPath: '/evercookie_png.php',
      etagPath: '/evercookie_etag.php',
      cachePath: '/evercookie_cache.php'
    };
    var optionMap = {};
    for (var key in defaultOptionMap) {
      var overidenValue = opts[key];
      if (overidenValue) {
        optionMap[key] = opts[key];
      } else {
        optionMap[key] = defaultOptionMap[key];
      }
    }
    function evercookieMiddlewareBackend(req, res, next) {
      var cookieValue;
      switch (req.path) {
        case optionMap.authPath:
          try {
            cookieValue = Buffer.from(
              req.headers.authorization.split(' ')[1],
              'base64'
            )
              .toString()
              .split(':')[0];
          } catch (e) {}
          if (cookieValue) {
            res.send(cookieValue);
            return;
          }
          res.setHeader('WWW-Authenticate', 'Basic');
          res.sendStatus(401);
          return;
        case optionMap.pngPath:
          /**
           * PNG cache is technically no difference than text cache, but adds much more overhead to encode and decode.
           * Return 201 No content
           */
          res.sendStatus(201);
          return;
        case optionMap.etagPath:
          /**
           * Port to NodeJS by TruongSinh <i@truongsinh.pro>
           * Defined by samy kamkar, https://github.com/samyk/evercookie/blob/master/evercookie_etag.php
           *
           * This is the server-side ETag software which tags a user by
           * using the Etag HTTP header, as well as If-None-Match to check
           * if the user has been tagged before.
           */
          cookieValue = req.cookies[optionMap.etagCookieName];
          if (!cookieValue) {
            cookieValue = req.get('If-None-Match');
          }
          if (cookieValue) {
            res.set('Etag', cookieValue);
            res.send(cookieValue);
            return;
          }
          res.sendStatus(304);
          return;
        case optionMap.cachePath:
          cookieValue = req.cookies[optionMap.cacheCookieName];
          if (cookieValue) {
            res.set({
              'Content-Type': 'text/html',
              Expires: 'Tue, 31 Dec 2030 23:30:45 GMT',
              'Cache-Control': 'private, max-age=630720000'
            });
            res.send(cookieValue);
            return;
          }
          res.sendStatus(304);
          return;
        default:
          next();
      }
    }
    return evercookieMiddlewareBackend;
  }
};