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.js 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 an Expo project.
| HS256 | HS384 | HS512 | RS256 | RS384 | RS512 | ES256 | ES384 | ES512 |
|---|---|---|---|---|---|---|---|---|
| Yes | Yes | Yes | No | No | No | No | No | No |
| exp | nbf | iat | sub | iss | aud | jti |
|---|---|---|---|---|---|---|
| Yes | Yes | Yes | Yes | Yes | Yes | No |
npm install --save expo-jwtimport JWT, { SupportedAlgorithms } from 'expo-jwt';
const key = 'shh';
JWT.encode({ foo: 'bar' }, key);
// => eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIifQ.YVoZ0LkWCMCnwEf7Nju2SJt_9mseJP1Q3RvCz4frGwM
JWT.encode({ foo: 'bar' }, key, { algorithm: SupportedAlgorithms.HS512 });
// => eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIifQ.Kyojwz8Z5SckLbMU-EImuzHEjjg_1apSOLz_tsZQj1025OH--qaORzkHUkScScd8-RZnWUdCu0epiaofQZNkBA
JWT.encode({ foo: 'bar' }, key, { algorithm: SupportedAlgorithms.NONE });
// => eyJhbGciOiJub25lIiwidHlwIjoiSldUIn0.eyJmb28iOiJiYXIifQ.import JWT from 'expo-jwt';
const key = 'shh';
const token =
'eyJhbGciOiJIUzUxMiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJiYXIifQ.Kyojwz8Z5SckLbMU-EImuzHEjjg_1apSOLz_tsZQj1025OH--qaORzkHUkScScd8-RZnWUdCu0epiaofQZNkBA';
JWT.decode(token, key);
// => { foo: 'bar' }If you would like to take advantage of a typed decode object body, you may pass a generic:
const foo = JWT.decode(token, key);
// foo.body === any
type MyType = Record<string, number>;
const bar = JWT.decode<MyType>(token, key);
// bar.body === MyTypeThe 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' });As mentioned in issue 7
certain device clocks may be slightly off, causing time based claims to fail. If
you are experiencing this issue you can pass the option timeSkew to
JWT.decode which will take this into account.
The value of this parameter is the number of seconds that the claim can be skewed by. Example:
// Allow verification of tokens that include "exp", "nbf", or "iat" claims
// within an additional 30 seconds of the system time.
JWT.decode(token, key, { timeSkew: 30 });
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