Sample JavaScript Middleware to sign requests

requestSign.js

var crypto = require('crypto-js');

module.exports = function requestSign(options) {
  options = options || {};

  return function requestSign(req, res, next) {
    if (!(options.accessKey && options.secretAccessKey && options.proxy)) {
      return next(new Error("options 'accessKey', 'secretAccessKey', and 'proxy' are required"));
    }

    var proxy        = options.proxy,
        protocol     = options.protocol || req.protocol,
        paramArray   = [],
        paramString  = '',
        signatureUrl = '',
        signature    = '';

    req.query.key = options.accessKey;

    for (param in req.query) {
      paramArray.push(param + '=' + req.query[param]);
    }

    // Update the url with the additional key param
    req.url = req.path + '?' + paramArray.join('&');

    // Set the final destination as the correct host
    // Otherwise, the server will use this server's host
    // to calculate the signature. They must
    // match.
    req.headers.host = proxy

    // Include post data in our signature
    if (req.method === 'POST') {
      for (param in req.body) {
        paramArray.push(param + '=' + req.body[param]);
      }
    }

    paramArray.sort();
    signatureUrl = protocol + '://' + proxy + req.path;
    paramArray.unshift(req.method, signatureUrl);
    paramString = paramArray.join('&');

    signature   = encodeURIComponent(paramString);
    signature   = crypto.HmacSHA1(signature, options.secretAccessKey);
    signature   = crypto.enc.Base64.stringify(signature);
    signature   = encodeURIComponent(signature);

    req.headers['Authorization'] = signature;
    if (options.forceSign) req.headers['FORCE_SIGN'] = "true";

    if (options.debug) {
      console.log("=== Request Sign ===");
      console.log("Proxy:            ", proxy);
      console.log("URL:              ", req.url);
      console.log("Query:            ", req.query);
      console.log("Body:             ", req.body);
      console.log("Signature String: ", paramString);
      console.log("Signature:        ", signature);
      console.log("Force Sign:       ", options.forceSign);
    }

    return next();
  };
};