zumojwt.js

function zumoJwt(expiryDate, aud, userId, masterKey) {
	var crypto = require('crypto');

	function base64(input) {
		return new Buffer(input, 'utf8').toString('base64');
	}

	function urlFriendly(b64)
	{
		return b64.replace(/\+/g, '-').replace(/\//g, '_').replace(/\=/g, '');
	}

	function signature(input) {
	  var key = crypto.createHash('sha256').update(masterKey + "JWTSig").digest('binary');
	  var str = crypto.createHmac('sha256', key).update(input).digest('base64');
	  return urlFriendly(str);
	}

	var s1 = '{"alg":"HS256","typ":"JWT","kid":0}';
	var j2 = {
		"exp":expiryDate.valueOf() / 1000,
		"iss":"urn:microsoft:windows-azure:zumo",
		"ver":1,
		"aud":aud,
		"uid":userId 
	};
	var s2 = JSON.stringify(j2);
	var b1 = urlFriendly(base64(s1));
	var b2 = urlFriendly(base64(s2));
	var b3 = signature(b1 + "." + b2);
	return [b1,b2,b3].join(".");
}