[Node.js] Creating JWTs (JSON Web Tokens) in Node

In this lesson we will look at all of the pieces that combine together to create a JWT (j AWT) or JSON Web Token. You will use node to create a JWT, and then verify it in the JWT debugger.

What is the JSON Web Token structure?

JSON Web Tokens consist of three parts separated by dots (.), which are:

• Header
• Payload
• Signature

Therefore, a JWT typically looks like the following.

xxxxx.yyyyy.zzzzz

Let's break down the different parts.

Create a header:

The header typically consists of two parts: the type of the token, which is JWT, and the hashing algorithm being used, such as HMAC SHA256 or RSA.

let header = {
  typ: 'JWT',
  alg: 'HS256'
};

header = new Buffer(JSON.stringify(header)).toString('base64');

console.log(header);

Create a paylaod:

The second part of the token is the payload, which contains the claims. Claims are statements about an entity (typically, the user) and additional metadata. There are three types of claims: reserved, public, and privateclaims.

let payload = {
  iat: Date.now(),
  iss: 'nodebotanist',
  username: 'nodebotanist'
};

payload = new Buffer(JSON.stringify(payload)).toString('base64');

console.log("payload", payload);

Create a signature:

To create the signature part you have to take the encoded header, the encoded payload, a secret, the algorithm specified in the header, and sign that.

For example if you want to use the HMAC SHA256 algorithm, the signature will be created in the following way:

HMACSHA256(
  base64UrlEncode(header) + "." +
  base64UrlEncode(payload),
  secret)

let key = header + '.' + payload;
let signature = crypto.createHmac('sha256', 'zhentian');
signature.update(key);
key = signature.digest('base64');

let token = header + '.' +payload + '.' + key
console.log("token", token)

----------------

let header = {
  typ: 'JWT',
  alg: 'HS256'
};

header = new Buffer(JSON.stringify(header)).toString('base64');

console.log(header);

let payload = {
  iat: Date.now(),
  iss: 'nodebotanist',
  username: 'nodebotanist'
};

payload = new Buffer(JSON.stringify(payload)).toString('base64');

console.log("payload", payload);

let key = header + '.' + payload;
let signature = crypto.createHmac('sha256', 'zhentian');
signature.update(key);
key = signature.digest('base64');

let token = header + '.' +payload + '.' + key
console.log("token", token)

Debugger