passport-fido2-webauthn

Passport strategy for authenticating with Web Authentication.

This module lets you authenticate using WebAuthn in your Node.js applications. By plugging into Passport, WebAuthn-based sign in can be easily and unobtrusively integrated into any application or framework that supports Connect-style middleware, including Express.

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Install

$ npm install passport-fido2-webauthn

Usage

The WebAuthn authentication strategy authenticates users using a public key-based credential. The authenticator which stores this credential is typically the user's device or an external security key, either of which may be unlocked using a PIN or biometric.

The strategy takes a verify function as an argument, which accepts id and userHandle as arguments. id identifies a public key credential that has been associated with a user's account. userHandle maps the credential to a specific user account. When authenticating a user, this strategy obtains this information from a WebAuthn assertion.

The verify function is responsible for determining the user to which the account at the OP belongs. Once it has made a determination, it invokes cb with the user record and a public key. The public key is used to cryptographically verify the WebAuthn assertion, thus authenticating the user.

This strategy also takes a register function as an argument, which is called when registering a new credential, and accepts user, id and publicKey as arguments. user represents a specific user account with which to associate the credential. id identifies the public key credential. publicKey is the PEM-encoded public key.

The register function is responsible for associating the new credential with the account. Once complete, it invokes cb with the user record.

Because the verify and register functions are supplied by the application, the app is free to use any database of its choosing. The example below illustrates usage of a SQL database.

var WebAuthnStrategy = require('passport-fido2-webauthn');
var SessionChallengeStore = require('passport-fido2-webauthn').SessionChallengeStore;

var store = new SessionChallengeStore();

passport.use(new WebAuthnStrategy({ store: store },
  function verify(id, userHandle, cb) {
    db.get('SELECT * FROM public_key_credentials WHERE external_id = ?', [ id ], function(err, row) {
      if (err) { return cb(err); }
      if (!row) { return cb(null, false, { message: 'Invalid key. '}); }
      var publicKey = row.public_key;
      db.get('SELECT * FROM users WHERE rowid = ?', [ row.user_id ], function(err, row) {
        if (err) { return cb(err); }
        if (!row) { return cb(null, false, { message: 'Invalid key. '}); }
        if (Buffer.compare(row.handle, userHandle) != 0) {
          return cb(null, false, { message: 'Invalid key. '});
        }
        return cb(null, row, publicKey);
      });
    });
  },
  function register(user, id, publicKey, cb) {
    db.run('INSERT INTO users (username, name, handle) VALUES (?, ?, ?)', [
      user.name,
      user.displayName,
      user.id
    ], function(err) {
      if (err) { return cb(err); }
      var newUser = {
        id: this.lastID,
        username: user.name,
        name: user.displayName
      };
      db.run('INSERT INTO public_key_credentials (user_id, external_id, public_key) VALUES (?, ?, ?)', [
        newUser.id,
        id,
        publicKey
      ], function(err) {
        if (err) { return cb(err); }
        return cb(null, newUser);
      });
    });
  }
));

Define Routes

Two routes are needed in order to allow users to log in with their passkey or security key.

The first route generates a randomized challenge, saves it in the ChallengeStore, and sends it to the client-side JavaScript for it to be included in the authenticator response. This is necessary in order to protect against replay attacks.

router.post('/login/public-key/challenge', function(req, res, next) {
  store.challenge(req, function(err, challenge) {
    if (err) { return next(err); }
    res.json({ challenge: base64url.encode(challenge) });
  });
});

The second route authenticates the authenticator assertion and logs the user in.

router.post('/login/public-key',
  passport.authenticate('webauthn', { failWithError: true }),
  function(req, res, next) {
    res.json({ ok: true });
  },
  function(err, req, res, next) {
    res.json({ ok: false });
  });

Examples

• todos-express-webauthn

  Illustrates how to use the WebAuthn strategy within an Express application.

License

The MIT License

Copyright (c) 2019-2022 Jared Hanson <https://www.jaredhanson.me/>