expo-jwt

A library for encoding or decoding JSON Web Tokens (JWT) in an Expo based React Native project.

In an Expo project the JavaScript environment is not node so specific objects such as Stream are not available, rendering many of the popular node-based JWT libraries on NPM unusable with Expo.

Additionally, unless the Expo project is "ejected" there is no access to the iOS/Android native code as other React Native specific JWT libraries have done.

This library implements HMAC-SHA signing for JWT by using Crypto.JS in pure JavaScript so it can be used inside of Expo.

Supported Algorithms

HS256	HS384	HS512	RS256	RS384	RS512	ES256	ES384	ES512
Yes	Yes	Yes	No	No	No	No	No	No

Supported Claims

exp	nbf	iat	sub	iss	aud	jti
Yes	Yes	Yes	Yes	Yes	Yes	No

Installation

npm install expo-jwt

or

yarn add expo-jwt

Usage

Encode

import JWT from 'expo-jwt';

const key = 'shh';

JWT.encode({ foo: 'bar' }, key);
// => eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIifQ==.MwMPn+JotG0ADbVQz8KgAXQkwT4Dd37499WucrGC6M4=

JWT.encode({ foo: 'bar' }, key, { algorithm: 'HS512' });
// => eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIifQ==.mdsKdpOymFm2IqXTTtS1JLA/9XM1c/Cjo9IwZoRlFd8MshIjp/RifniPlz9Nq5LCVwa8xIFeKYeNu0pvNJl4JQ==

JWT.encode({ foo: 'bar' }, key, { algorithm: 'none' });
// => eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0=.eyJmb28iOiJiYXIifQ==.

Decode

import JWT from 'expo-jwt';

const key = 'shh';
const token =
  'eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIifQ==.mdsKdpOymFm2IqXTTtS1JLA/9XM1c/Cjo9IwZoRlFd8MshIjp/RifniPlz9Nq5LCVwa8xIFeKYeNu0pvNJl4JQ==';

JWT.decode(token, key);
// => { foo: 'bar' }

JWT Claims

The claims exp, nbf, and iat will automatically be verified if the decoded payload of the JWT contains any of them.

The iss, sub, and aud claims can be verified by passing in the expected value to the decode options.

// Issuer - iss
JWT.decode(token, key, { iss: 'expected-issuer' });

// Subject - sub
JWT.decode(token, key, { sub: 'expected-subject' });

// Audience - aud
JWT.decode(token, key, { aud: 'expected-audience' });