Function that creates a ZUMO JWT token. Specify the date, the aud, the userId and your Mobile Services master key, e.g. var expiry = new Date().setUTCDate(new Date().getUTCDate() + 1); // expires in one day from nowvar jwt = zumoJwt(expiry, "your-aud", "unique string for this user", "yourmasterkey");

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":2,
		"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(".");
}

Hello. I looking to write a JavaScript code that can do Server to Server OAuth2 (i.e., no user interaction or consent). I have the necessary credentials (ID and private key) set up in my Google domain for a Service account. All I need now is the JavaScript to make it happen. I checked out the Google JS library but it does not seem to support this particular OAuth flow (i.e., Server to Server, also called 2-legged OAuth I believe). Thoughts on this?