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 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('jwks-rsa');

const client = jwksClient({
  jwksUri: 'https://sandrino.auth0.com/.well-known/jwks.json',
  requestHeaders: {}, // Optional
  timeout: 30000 // Defaults to 30s
});

const kid = 'RkI5MjI5OUY5ODc1N0Q4QzM0OUYzNkVGMTJDOUEzQkFCOTU3NjE2Rg';
const key = await client.getSigningKey(kid);
const signingKey = key.getPublicKey();

Integrations

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

API

JwksClient Options

• jwksUri: a string that represents the JWKS URI
• timeout = 30000: (optional) an integer in miliseconds that controls the request timeout
• cache = true: (optional) enables a LRU Cache (details)
• rateLimit: (optional) the default fetcher function (details)
• fetcher: (optional) a Promise returning function to fetch data from the JWKS URI
• requestHeaders: (optional) an object of headers to pass to the request
• requestAgent: (optional) a Node http.Agent to be passed to the http(s) request
• getKeysInterceptor: (optional) a promise returning function hook (details)

Caching

By default, signing key verification results are cached in order to prevent excessive HTTP requests to the JWKS endpoint. 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. The caching behavior can be configured as seen below:

const jwksClient = require('jwks-rsa');

const client = jwksClient({
  cache: true, // Default Value
  cacheMaxEntries: 5, // Default value
  cacheMaxAge: 600000, // Defaults to 10m
  jwksUri: 'https://sandrino.auth0.com/.well-known/jwks.json'
});

const kid = 'RkI5MjI5OUY5ODc1N0Q4QzM0OUYzNkVGMTJDOUEzQkFCOTU3NjE2Rg';
const key = await client.getSigningKey(kid);
const signingKey = key.getPublicKey();

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('jwks-rsa');

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

const kid = 'RkI5MjI5OUY5ODc1N0Q4QzM0OUYzNkVGMTJDOUEzQkFCOTU3NjE2Rg';
const key = await client.getSigningKey(kid);
const signingKey = key.getPublicKey();

Using Request Agent for TLS/SSL Configuration

The requestAgent property can be used to configure SSL/TLS options. An example use case is providing a trusted private (i.e. enterprise/corporate) root certificate authority to establish TLS communication with the jwks_uri.

const jwksClient = require("jwks-rsa");
const https = require('https');
const client = jwksClient({
  jwksUri: 'https://my-enterprise-id-provider/.well-known/jwks.json',
  requestHeaders: {}, // Optional
  requestAgent: new https.Agent({
    ca: fs.readFileSync(caFile)
  })
});

Proxy configuration

You can configure a proxy with using a custom http(s) agent in the requestAgent option.

Loading keys from local file, environment variable, or other externals

The getKeysInterceptor property can be used to fetch keys before sending a request to the jwksUri endpoint. This can be helpful when wanting to load keys from a file, env variable, or an external cache. If a KID cannot be found in the keys returned from the interceptor, it will fallback to the jwksUri endpoint. This property will continue to work with the provided LRU cache, if the cache is enabled.

  const client = new JwksClient({ 
    jwksUri: 'https://my-enterprise-id-provider/.well-known/jwks.json',
    getKeysInterceptor: () => {
      const file = fs.readFileSync(jwksFile);
      return file.keys;
    }
  });

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' } ]

License

This project is licensed under the MIT license. See the LICENSE file for more info.