verify-rsa-jwt-cloudflare-worker

verify-rsa-jwt-cloudflare-worker

This is a lightweight library that verifies a JWT (JSON Web Token) signed with RS256. This is built for Cloudflare Workers.

Although, the project itself has no dependencies. If the runtime supports Web Standard APIs, it should just work :tm:

This package includes the Hono Middleware :fire:

It uses JWKS to verify a JWT. To fetch JWKS, you need to provide the JWKs endpoint URL to JWKS_URI.

Install

npm install verify-rsa-jwt-cloudflare-worker

Usage

Module Worker

import {
  getJwks,
  useKVStore,
  verify,
  VerifyRsaJwtEnv,
} from "verify-rsa-jwt-cloudflare-worker";

export default {
  async fetch(request: Request, env: VerifyRsaJwtEnv): Promise<Response> {
    const token =
      request.headers.get("Authorization")?.replace(/Bearer\s+/i, "") || "";
    try {
      const jwks = await getJwks(env.JWKS_URI, useKVStore(env.VERIFY_RSA_JWT));
      const { payload } = await verify(token, jwks);
      // Then, you could validate the payload and return a response
      return new Response(JSON.stringify({ payload }), {
        headers: { "content-type": "application/json" },
      });
    } catch (error: any) {
      return new Response((error as Error).message, { status: 401 });
    }
  },
};

wrangler.toml

name = "verify-rsa-jwt-cloudflare-worker"
compatibility_date = "2023-05-18"

[vars]
JWKS_URI = "https://<your-authorization-server-host>/.well-known/jwks.json"
VERIFY_RSA_JWT_JWKS_CACHE_KEY = ""

[[kv_namespaces]]
binding = "VERIFY_RSA_JWT"
id = "<ID CREATED BY WRANGLER>"
preview_id = "<ID CREATED BY WRANGLER>"

Use Without a KV Store

If you do not want to use a KV store to cache the JWKS returned by getJwks(), you can omit the second parameter.

const jwks = await getJwks("https://<myurl>/.well-known/jwks.json");

[!WARNING] Not caching the JWKS in a KV store will result in longer response times since the JWKS must be refetched on every request. It can also lead to request throttling from the JWKS provider if your Worker receives a lot of traffic.

Hono Middleware

The middleware provides authentication by verifying the token with RSA-JWT. Authorization header value or cookie value specified by the cookie option will be used as a token.

If you are working on a Cloudflare Workers based project, the following parameters can be set via wrangler.toml.

VerifyRsaJwtEnv

Variable	Description
VERIFY_RSA_JWT	KVNamespace. It want to store downloaded JWKS
VERIFY_RSA_JWT_JWKS_CACHE_KEY	Optional string to specify what key we want to sue to store JWKS. Default: verify-rsa-jwt-cloudflare-worker-jwks-cache-key
JWKS_URI	A URI for downloading JWKS. Typically https://<host>/.well-known/jwks.json
JWKS	Optional. Instead of giving the URI, You could provide hardcoded jwks.

Additionally, or, if you are working on a non-Cloudflare Workers based project, such as Node.js, the following optional config values are available:

VerifyRsaJwtConfig

Variable	Description
jwksUri	A URI for downloading JWKS.
jwks	Optional. Instead of giving the URI, You could provide hardcoded jwks.
kvStore	Any storage manager that has get and put. It's used for storing JWKS.
payloadValidator	Every authentication vendor would configure JWT payload differently. Please give a function that validates the payload and throw an error.
verbose	A debug flag.

Import

import { Hono } from "hono";
import {
  verifyRsaJwt,
  getPayloadFromContext,
  createGetCookieByKey,
} from "verify-rsa-jwt-cloudflare-worker";

Hono Middleware Usage

Scenario 1: When the token is given via the Authorization header.

const app = new Hono()

app.use(
  '/auth/*',
  verifyRsaJwt({
    jwksUri: "https://<host>/.well-known/jwks.json",
    kvStore: // Anything that keeps a value, KVNamespace should work too.
    payloadValidator: ({payload, ctx}) => { /* Validate the payload, throw an error if invalid */ },
  })
)

Scenario 2: When the token is given via the Cookie header.

import { getCookie } from "hono/cookie";
const app = new Hono()

app.use(
  '/auth/*',
  verifyRsaJwt({
    getCookieByKey: createGetCookieByKey(getCookie, "access_token"), // "access_token" is an example cookie key name where you want to fetch a JWT from.
    jwksUri: "https://<host>/.well-known/jwks.json",
    kvStore: // Anything that keeps a value, KVNamespace should work too.
    payloadValidator: ({payload, ctx}) => { /* Validate the payload, throw an error if invalid */ },
  })
)

Get payload:

app.get("/auth/page", (c) => {
  const claims = getPayloadFromContext(c);
  return c.text("You are authorized");
});

Test

Automated tests

Some tests use PEM files to create JWT tokens / imitate JWKS. You need the following setup to prepare them.

• Create a .env file.

  echo PEM_NAME="test-pem" > .env
  

• Run npm run gen-pem-keys to generate PEM files.

• Then, as you may be familiar, test with npm test.

Manual test

For testing through src/worker.ts, you can:

• Launch a local server

  npm run start src/worker.ts
  

• cURL with your JWT!

  url -H "Authorization: Bearer <YOUR-JWT>" http://127.0.0.1:<YOUR-DEV-SERVER-PORT>/
  

• Then, if everything is set correctly, you'd expect to see something like this:

  {
    "payload": {
      "iss": " ... ",
      "sub": " ... ",
      "aud": " ... ",
      "iat": 1690401415,
      "exp": 1690487815,
      "azp": " ... ",
      "gty": " ... "
    }
  }
  

Development

Use Wrangler CLI

Please follow this document. https://developers.cloudflare.com/workers/get-started/guide/.

Learn more about Authentication

Auth0 provides amazing documents.