JWT tokenize - Postman Pre-Request Script

pre-request-jwt.js

function base64url(source) {
	// Encode in classical base64
	encodedSource = CryptoJS.enc.Base64.stringify(source);

	// Remove padding equal characters
	encodedSource = encodedSource.replace(/=+$/, '');

	// Replace characters according to base64url specifications
	encodedSource = encodedSource.replace(/\+/g, '-');
	encodedSource = encodedSource.replace(/\//g, '_');

	return encodedSource;
}

function addIAT(request) {
	var iat = Math.floor(Date.now() / 1000) + 257;
	data.iat = iat;
	return data;
}


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

var data = {
	"fname": "name",
	"lname": "name",
	"email": "[email protected]",
	"password": "abc123$"
};

data = addIAT(data);

var secret = 'myjwtsecret';

// encode header
var stringifiedHeader = CryptoJS.enc.Utf8.parse(JSON.stringify(header));
var encodedHeader = base64url(stringifiedHeader);

// encode data
var stringifiedData = CryptoJS.enc.Utf8.parse(JSON.stringify(data));
var encodedData = base64url(stringifiedData);

// build token
var token = encodedHeader + "." + encodedData;

// sign token
var signature = CryptoJS.HmacSHA256(token, secret);
signature = base64url(signature);
var signedToken = token + "." + signature;

postman.setEnvironmentVariable("payload", signedToken);

In my case changed secret to base64 worked perfectly. Those who are facing problem can try this out

var signature = CryptoJS.HmacSHA256(token, CryptoJS.enc.Base64.parse(secret));

reference this:
https://www.postman.com/postman/workspace/postman-team-collections/request/8140651-fa914e7e-362a-4698-8a5a-0c81dfebf5f9?tab=scripts

`var navigator = {};
var window = {};
eval(pm.environment.get("jsrsasign-js"));

var scope = pm.environment.get('scope');
var iss = pm.environment.get('iss');
var privateKey = pm.environment.get('privateKey');

const header = {"alg" : "RS256", "typ" : "JWT"};

const claimSet =
{
"iss": iss,
"scope": scope ,
"aud":"https://oauth2.googleapis.com/token",
"exp":KJUR.jws.IntDate.get("now + 1hour").toString(),
"iat": KJUR.jws.IntDate.get("now").toString()
}

console.log(header: ${ JSON.stringify(header)});
console.log(claim set: ${ JSON.stringify(claimSet) });
console.log(Private Key: ${ privateKey });

// let jws = new KJUR.jws.JWS();
var jwt = KJUR.jws.JWS.sign(null, header, claimSet, privateKey);
console.log(jwt);

pm.environment.set('jwt', jwt);`