JWKs Fetch

jwks-fetch is a NodeJS library which retrieves asymmetric keys in JWKs format. It supports both RSA and EC keys.

npm install --save jwks-fetch

It implements a Promise based API. NodeJS 8 or above is required. For now it's only compatible with Node, but isomorphic support is planned.

const {JWKSClient, HTTPError} = require('jwks-fetch');

const client = JWKSClient({ cache: true, ttl: 60, strictSSL: false });
const url = 'https://demo.com/static/jwks.json';
const kid = 'auth';

client.retrieve(url, kid)
    .then(r => {
        console.log(r);

        /*
         * -----BEGIN PUBLIC KEY-----
         * MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA+Mv6SZ2mcGjVBwfAIfCZ
         * 9MjnMuJpKrSFCcLJQ44TIh01zmOogxvobC+tm4sv+hiJ8F9S7CDxVJ7Xs6JNV+I8
         * XgqK+ZfrjCLNTsuxv5Y/ByFaq0pjHmWa8mKfsQ389qo4AuoILaj40f1Ai4KXkjWu
         * UkKj1t+PAusOazpN3InOLHfUKWhXNMyWFuVfACDlHuOPq9wzbD+AmrM76GwY/xSO
         * DvtNCM4pSF4FWTBRTZhelr7POERxd5Lb2uZxfiXCcyLVNf7DTzHjPB40lyrQ+bv4
         * t5/FuaqMBMCtOPYNUqBwdQ79k3jJkPQNoyjuyXwzeP90jkBEZxmR/j/si56r0urQ
         * tQIDAQAB
         * -----END PUBLIC KEY-----
         */
    })
    .catch(err => {
        if (err instanceof HTTPError) {
            console.error(`status code ${err.status}`);
        }
        console.error(err);
    });

Options

{
    cache: false // Enable or disable cache
    ttl: 60, // Amount of time in seconds to cache a key
    strictSSL: true // Throw error if SSL certificate could not be validated
}

HTTPError

If the jwks_uri didn't respond with an HTTP status code 200 a custom HTTPError exception will be thrown. From there you can access the raw response with err.res and the status code with err.status. If an exception occurs when requesting the JWKs an HTTPError will also be thrown, but with a null res.

Useful links

• JSON Web Key
• JSON Web Algorithms
• mkjwk