jwks-rsa

What is jwks-rsa?

The jwks-rsa npm package is a library that helps to retrieve RSA signing keys from a JWKS (JSON Web Key Set) endpoint. It is primarily used in scenarios where you need to verify the signature of JSON Web Tokens (JWTs) against public keys published in a JWKS. This is common in modern authentication flows, especially those implementing OpenID Connect.

What are jwks-rsa's main functionalities?

Retrieving RSA signing keys

This feature allows you to retrieve RSA signing keys from a JWKS endpoint. The `getSigningKey` method is used to fetch the key using the `kid` (key ID) from the JWT header. This is useful for verifying JWT signatures.

const jwksClient = require('jwks-rsa');
const client = jwksClient({
  jwksUri: 'https://your-domain.com/.well-known/jwks.json'
});

function getKey(header, callback){
  client.getSigningKey(header.kid, function(err, key) {
    var signingKey = key.publicKey || key.rsaPublicKey;
    callback(null, signingKey);
  });
}

Integrating with Express.js for JWT authentication

This code snippet demonstrates how to use jwks-rsa with express-jwt middleware for securing Express.js applications. The `expressJwtSecret` method is used to dynamically provide a signing key based on the incoming JWT's `kid`.

const jwt = require('express-jwt');
const jwksRsa = require('jwks-rsa');

const checkJwt = jwt({
  secret: jwksRsa.expressJwtSecret({
    cache: true,
    rateLimit: true,
    jwksRequestsPerMinute: 5,
    jwksUri: 'https://your-domain.com/.well-known/jwks.json'
  }),
  audience: 'your-audience',
  issuer: 'https://your-domain.com/',
  algorithms: ['RS256']
});

Other packages similar to jwks-rsa

node-jose

A package for JavaScript Object Signing and Encryption (JOSE) and JSON Web Token (JWT) implementation. It offers similar functionalities for handling JWKS but is more comprehensive in terms of JOSE standards support, including encryption and decryption capabilities, which jwks-rsa does not directly offer.

jsonwebtoken

This package is primarily focused on creating and verifying JSON Web Tokens (JWTs). While it doesn't directly handle JWKS, it is often used in conjunction with libraries like jwks-rsa for verifying JWT signatures against public keys obtained from a JWKS endpoint.

README

jwks-rsa

A library to retrieve RSA signing keys from a JWKS (JSON Web Key Set) endpoint.

npm install --save jwks-rsa

Usage

You'll provide the client with the JWKS endpoint which exposes your signing keys. Using the getSigningKey you can then get the signing key that matches a specific kid.

const jwksClient = require('jwksClient');

const client = jwksClient({
  strictSsl = true, // Default value
  jwksUri: 'https://sandrino.auth0.com/.well-known/jwks.json'
});

const kid = 'RkI5MjI5OUY5ODc1N0Q4QzM0OUYzNkVGMTJDOUEzQkFCOTU3NjE2Rg';
client.getSigningKey(kid, (err, key) => {
  const signingKey = key.publicKey || key.rsaPublicKey;

  // Now I can use this to configure my Express or Hapi middleware
});

Integrations are also provided with:

• express/express-jwt
• hapi/hapi-auth-jwt2

Caching

In order to prevent a call to be made each time a signing key needs to be retrieved you can also configure a cache as follows. If a signing key matching the kid is found, this will be cached and the next time this kid is requested the signing key will be served from the cache instead of calling back to the JWKS endpoint.

const jwksClient = require('jwksClient');

const client = jwksClient({
  cache: true,
  cacheMaxEntries: 5, // Default value
  cacheMaxAge = ms('10h'), // Default value
  jwksUri: 'https://sandrino.auth0.com/.well-known/jwks.json'
});

const kid = 'RkI5MjI5OUY5ODc1N0Q4QzM0OUYzNkVGMTJDOUEzQkFCOTU3NjE2Rg';
client.getSigningKey(kid, (err, key) => {
  const signingKey = key.publicKey || key.rsaPublicKey;

  // Now I can use this to configure my Express or Hapi middleware
});

Rate Limiting

Even if caching is enabled the library will call the JWKS endpoint if the kid is not available in the cache, because a key rotation could have taken place. To prevent attackers to send many random kids you can also configure rate limiting. This will allow you to limit the number of calls that are made to the JWKS endpoint per minute (because it would be highly unlikely that signing keys are rotated multiple times per minute).

const jwksClient = require('jwksClient');

const client = jwksClient({
  cache: true,
  rateLimit: true,
  jwksRequestsPerMinute: 10, // Default value
  jwksUri: 'https://sandrino.auth0.com/.well-known/jwks.json'
});

const kid = 'RkI5MjI5OUY5ODc1N0Q4QzM0OUYzNkVGMTJDOUEzQkFCOTU3NjE2Rg';
client.getSigningKey(kid, (err, key) => {
  const signingKey = key.publicKey || key.rsaPublicKey;

  // Now I can use this to configure my Express or Hapi middleware
});

Running Tests

npm run test

Showing Trace Logs

To show trace logs you can set the following environment variable:

DEBUG=jwks

Output:

jwks Retrieving keys from http://my-authz-server/.well-known/jwks.json +5ms
jwks Keys: +8ms [ { alg: 'RS256',
  kty: 'RSA',
  use: 'sig',
  x5c: [ 'pk1' ],
  kid: 'ABC' },
{ alg: 'RS256', kty: 'RSA', use: 'sig', x5c: [], kid: '123' } ]