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@smac89

smac89/jwt.mjs

Last active Aug 5, 2020
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Learning how JWT works
import crypto from 'crypto';
import assert from 'assert';
const header = {"alg":"HS256","typ":"JWT"};
const payload = {"loggedInAs":"admin","iat":1422779638};
const unsignedToken = Buffer.from(JSON.stringify(header)).toString('base64') +
'.' + Buffer.from(JSON.stringify(payload)).toString('base64');
const hmac = crypto.createHmac('sha256', 'secretkey');
hmac.write(unsignedToken);
hmac.end();
const sig = hmac.read(); // sig is a hex string
console.log(`${unsignedToken}.${sig.toString('base64')}`);
// This sig is now stored on the server and can be used to verify a user
// once they make any requests
const token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJsb2dnZWRJbkFzIjoiYWRtaW4iLCJpYXQiOjE0MjI3Nzk2Mzh9.gzSraSYS8EXBxLN/oWnFSRgCzcmJmMjLiuyu5CSpyHI=";
// verify process
const segments = token.split('.');
const [encHeader, encPaylod, encSig] = token.split('.');
const clientHeader = JSON.parse(Buffer.from(encHeader, 'base64').toString());
const clientPayload = JSON.parse(Buffer.from(encPaylod, 'base64').toString());
assert.deepStrictEqual(clientHeader, header);
assert.deepStrictEqual(clientPayload, payload);
if (crypto.timingSafeEqual(Buffer.from(encSig, 'base64'), sig)) {
console.log("Success!");
} else {
console.log('Get out!');
}
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