Creating JWT and signing it

Found this link and started with this:

var header = {
  "alg": "HS256",
  "typ": "JWT"
};

var data = {
  "id": 1337,
  "username": "john.doe"
};

var encodedHeader = btoa(JSON.stringify(header));
var encodedData = btoa(JSON.stringify(data));
var token = encodedHeader + "." + encodedData;
var secret = "My very confidential secret!";

print(token);

/* struggled at this point, no clue if there i an existing solution for this 
var signature = CryptoJS.HmacSHA256(token, secret);
*/

signature = btoa(signature);
var signedToken = token + "." + signature;

Any hints howto?

Would https://www.espruino.com/Reference#l_cry­pto_SHA256 work?

That doesn't have the HMAC but you might be able to use https://www.espruino.com/hmac

Seems like there's a convenience function for SHA1 but hmac=require("hmac"); ... = new hmac.HMAC(key, require('crypto').SHA256, 64, 20); might do it (if you know what block size HmacSHA256 uses?)

Nice, thank for sharing, will try to write a HmacSHA256 module.

sha-256 64 32

Maybe you could do a PR to add that to the hmac module?

Yes, definitely - on my way but struggling a fresh LINUX build and a working connecting via tcp.

There should be a new module named hmac2, because not all boards include SHA256.

Missing a last piece, how to encode the Uint8Array([...]).bufferto a base64. The method toString only allow option 2 and 16, base64 is not implemented, any hint?

got it

signature = HmacSHA256(token, secret);
print(btoa(String.fromCharCode.apply(nul­l, signature)));

Using module hmac256 to create JSON Web Token. A PR is wating for verification and comments.

const HMAC = require('hmac2256');
HmacSHA256 = function(token, secret) {
      var hmac = HMAC.SHA256(E.toArrayBuffer(secret));
     return btoa(String.fromCharCode.apply(null,  hmac.digest(E.toArrayBuffer(token)))).re­place(/=+$/, ''); 
};

var header = { "alg": "HS256", "typ": "JWT"};
var data = { "id": 1337,"username": "john.doe"};
var secret = "My very confidential secret!";
var encodedHeader = btoa(JSON.stringify(header));
var encodedData = btoa(JSON.stringify(data));
var token = encodedHeader + "." + encodedData;
var signature = HmacSHA256(token, secret);
var jwt = (token+'.'+signature);