# Protect a Node.js API

> Add OneiD to a Node.js API API with jose with Express, step by step.

Source: https://oltinid.com/docs/quickstarts/api-node/ · Section: Quickstarts · All OneiD documentation: https://oltinid.com/llms.txt

This quickstart adds OneiD to a api with **jose with Express**. Every file is complete and runs as it is.

> **Tip:** Using an AI coding agent? Give it this page as Markdown (add `.md` to the address) together with the [Connector specification](https://oltinid.com/docs/ai/connector-specification/). See [Build with AI coding agents](https://oltinid.com/docs/ai/build-with-ai/).

## Before you start

- A OneiD address, for example `https://YOUR_ONEID`. The code below uses the demonstration instance `https://auth.oltinid.com`; replace it with your own.
- An access token with the scope `orders.read` to test with.

## 1. Register the application

An API is not a client: it does not sign in. It needs an **API scope** that clients can request.

1. Ask your OneiD administrator to create the API scope `orders.read` (or a scope named after your API) in the admin console.
2. Ask for the scope to be allowed on the client that will call the API.
3. Get an access token with that scope: from a [server or browser application](https://oltinid.com/docs/quickstarts/), or with the [client credentials grant](https://oltinid.com/docs/quickstarts/curl/).

> **Note:** OneiD access tokens have no `aud` claim. The API accepts a token because it was issued by your OneiD, is unexpired and carries the scope the API requires. Give each API its own scopes. See [Protect an API](https://oltinid.com/docs/guides/protect-an-api/).

## 2. Install

```bash
npm install express jose
```

## 3. Add the code

`server.js`

```js
import express from 'express';
import { createRemoteJWKSet, jwtVerify } from 'jose';

// Reads the issuer name and the address of the signing keys from OneiD.
const oneid = await (await fetch('https://auth.oltinid.com/.well-known/openid-configuration')).json();

// jose downloads the public keys on first use and again when OneiD rotates them.
const keys = createRemoteJWKSet(new URL(oneid.jwks_uri));

// Lets a request pass only with a valid access token that carries the scope.
const requireScope = (scope) => async (req, res, next) => {
  const token = req.headers.authorization?.replace(/^Bearer /, '');
  try {
    // Checks the signature, the issuer and the expiry. No audience: OneiD tokens have no aud claim.
    const { payload } = await jwtVerify(token, keys, { issuer: oneid.issuer, algorithms: ['RS256'] });
    req.user = payload;
  } catch {
    return res.sendStatus(401); // no token, or the token is not valid
  }

  // The scope claim is one string with a space between the scopes.
  if (!req.user.scope?.split(' ').includes(scope)) return res.sendStatus(403);
  next();
};

const app = express();

app.get('/orders', requireScope('orders.read'), (req, res) => {
  res.json({ sub: req.user.sub });
});

app.listen(4000, () => console.log('http://localhost:4000/orders'));
```

## 4. Run it

Set "type": "module" in package.json, then run: node server.js.

The API listens on http://localhost:4000. GET /orders answers 401 without a valid token, 403 without the scope orders.read, and otherwise returns the sub of the caller.

Test it with a token:

```bash
curl -i http://localhost:4000/orders
# HTTP/1.1 401 Unauthorized

curl -i http://localhost:4000/orders -H "Authorization: Bearer $ACCESS_TOKEN"
# HTTP/1.1 200 OK when the token carries orders.read, 403 when it does not
```

> **Checkpoint:** Without a token the API answers 401. With a valid token that carries `orders.read` it answers 200 and returns your `sub`; with a valid token without that scope it answers 403.

## Common issues

- **401 with a token that looks valid.** Check the issuer: OneiD’s issuer ends with a slash (`https://YOUR_ONEID/`).
- **The API checks `aud` and rejects every token.** OneiD access tokens carry no `aud`; remove the audience check and check the scope instead.
- More errors and fixes: [Errors and troubleshooting](https://oltinid.com/docs/reference/errors/).

## Learn more

- [Protect an API](https://oltinid.com/docs/guides/protect-an-api/)
- [Tokens](https://oltinid.com/docs/reference/tokens/)
- [Client credentials for services](https://oltinid.com/docs/guides/client-credentials/)