node-jwks-utils

A set of useful tools when working with JSON Web Key (JWK) and JSON Web Key Set (JWKs).

Install

$ npm install jwks-utils

Example

var jwksUtils = require('jwks-utils');

var jwk = { kid: '1234', kty: 'RSA', n: '12345...XYZ=', e: 'AQAB' };
var jwks = { keys: [ jwk ] }

// Detect a JWK object
if(jwksUtils.isJWK(jwk)) {
    // Do stuff with the JWk
}

// Detect a JWKs object
if(jwksUtils.isJWKset(jwks)) {
    // Do stuff with the JWKs
}

// Find a particilar JWK within a JWKs
var jwk1 = jwkUtils.findJWK('1234', jwks);

// Find the JWK corsponding to a particular JWS (or JWT)
var signature = getJWSFromSomwhere();
jwkUtils.jwkForSignature(signature, false, {timeout: 100}, function(err, jwk2) {
    if (!err) {
        // jwk2 is the corresponding JWK
    }
};

Caching of JSON Web Key Sets (jwks) from a JSON Web Key URI (jku)

This library makes requests to outside web URI's if it determines that a jku is needed to get the public key (jwk) to verify a signature. It expects that URL to have a JSON Web Key Set (jwks according to the standard). Because this process can sometimes be slow, and because in production sometimes networks go down, we have added a small in-memory cache to this library.

When the library decides it needs a jwks from a jku, it will immediately return the cached value if the given signature's key is in the cached keyset. It will also fire off a request in the background that will update the cache to the latest copy of the jwk set. It will consider the cache entry stale after 1 hour and then wait for the request to update the cache.

If the key in the signature was not in a cached jwks (or it was not yet cached at all), the function will wait for the request to finish. Once it finishes, if there was an error in the request, it will check the cache to see if we have a stale cached copy. If so, then it will use that stale cached copy for up to 24 hours before removing it from the cache.

If it does not have an error in the request, even if we've already returned the cached copy for the signature, it will go ahead and put the new response's jwks into the cache and then return it.

In this way, whenever you publish a new kid in your jwks, any clients will immediately be able to use it. However, if you revoke a kid, the client will still allow for 1 valid signature in the first hour, and then any request after the first one, or after an hour, will be invalid.

References

1. JSON Web Key (JWK) Draft 40