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Sign in with Apple strategy for Passport

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Passport strategy for authenticating with Sign in with Apple.

Install

$ npm install @nicokaiser/passport-apple

Usage

Create a Service

Before using this module, you must register a service with Apple. You need an Apple Developer Account for this.

Configure Strategy

The Sign in with Apple authentication strategy authenticates users using an Apple ID and OAuth 2.0 tokens. The strategy options are supplied in the step above. The strategy also requires a verify callback, which receives an access token and profile, and calls cb providing a user.

passport.use(new AppleStrategy({
    clientID: 'com.example.account', // Services ID
    teamID: '1234567890', // Team ID of your Apple Developer Account
    keyID: 'ABCDEFGHIJ', // Key ID, received from https://developer.apple.com/account/resources/authkeys/list
    key: fs.readFileSync(path.join('path', 'to', 'AuthKey_XYZ1234567.p8')), // Private key, downloaded from https://developer.apple.com/account/resources/authkeys/list
    scope: ['name', 'email'],
    callbackURL: 'https://example.com/auth/apple/callback'
  },
  (accessToken, refreshToken, profile, cb) => {
    User.findOrCreate({ exampleId: profile.id }, (err, user) => {
      return cb(err, user);
    });
  }
));

If passReqToCallback is set to true, req will be passed as the first argument to the verify callback:

passport.use(new AppleStrategy({
    clientID: 'com.example.account', // Services ID
    ...
    passReqToCallback: true
  },
  (req, accessToken, refreshToken, profile, cb) => {
    ...
  }
));

Authenticate Requests

Use passport.authenticate(), specifying the 'apple' strategy, to authenticate requests. The authorization code is passed via the code POST parameter, so your endpoint callback needs to support HTTPS POST and provide the req.body property.

For example, as route middleware in an Express application, using express.urlencoded to provide req.body:

app.get('/auth/apple',
  passport.authenticate('apple'));

app.post('/auth/apple/callback',
  express.urlencoded(),
  passport.authenticate('apple', { failureRedirect: '/login' }),
  (req, res) => {
    // Successful authentication, redirect home.
    res.redirect('/');
  });

You can find a complete example at examples/server.js.

Nonce Verification

To supply and verify a nonce to prevent a login session from being replayed, use the verifyNonce option when creating the strategy:

const generatedNonces = new NodeCache();

passport.use(new AppleStrategy({
    ...
    verifyNonce: function(req, nonce, callback){
        if(generatedNonces.take(nonce)){
            callback(null, true);
        }else{
            callback(new Error('invalid nonce'), false);
        }
    },
  },
  ...
);

And supply a nonce value in the options to each authenticate call:

app.post('/auth/apple/callback',
  express.urlencoded(),
  function(req, res, next){
      const nonce = crypto.randomBytes(16).toString('hex');
      generatedNonces.set(nonce, 1);
      passport.authenticate('apple', { failureRedirect: '/login', nonce: nonce })(req, res, next);
  },
  (req, res) => {
    // Successful authentication, redirect home.
    res.redirect('/');
  });

For multi-server applications the nonces must be shared between all servers, for example by storing them in a shared cache or database.

FAQ

Which fields are provided in the user profile?

Apple currently returns a User ID that is tied to you Team ID. That means, the same Apple ID will result in the same User ID returned for authentication requests done with your Team ID. Other Teams will get a different ID for this User.

Also, if the User wants to, their name and email address is returned:

{ id, name: { firstName, lastName }, email, emailVerified, isPrivateEmail } = profile;

Note that on subsequent logins, only id is being returned, the other properties are only returned on the first login

Why not just use passport-oauth2?

The login flow for Sign in with Apple is similar to OAuth 2 and OpenID Connect, but there are quite some differences. The OpenID Foundation published a document about this: How Sign In with Apple differs from OpenID Connect.

Namely, instead of a static client_secret, a JWT is used, however in a non-standard way. Also, user data is submitted alongside the authentication code via HTTP POST (and only if the "form_post" response mode is used!).

Apple is still working on the interfaces, as Sign in with Apple is still in beta, so it may be OIDC compliant at some point in the future.

How does this module differ from passport-apple?

passport-apple uses passport-oauth2 and replaces its client secret methods. This works, however it does not support retrieving user data (like name and email). In order to properly support this, you would need to basically re-write a slimmed down version of passport-oauth2, which basically is what this module provides.

License

Licensed under MIT.