passport-ethereum-siwe

Passport strategy for authenticating with Sign-In with Ethereum.

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

Install

$ npm install passport-ethereum-siwe

Usage

The Ethereum authentication strategy authenticates users using an Ethereum wallet.

The strategy takes a verify function as an argument, which accepts address as an argument. address is the user's Ethereum address. When authenticating a user, this strategy obtains this information from a message signed by the user's wallet.

The verify function is responsible for determining the user to which the address belongs. In cases where the account is logging in for the first time, a new user record is typically created automatically. On subsequent logins, the existing user record will be found via its relation to the address.

Because the verify function is 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 EthereumStrategy = require('passport-ethereum-siwe');
var SessionNonceStore = require('passport-ethereum-siwe').SessionNonceStore;

var store = new SessionChallengeStore();

passport.use(new EthereumStrategy({ store: store },
  function verify(address, cb) {
    db.get('SELECT * FROM blockchain_credentials WHERE chain = ? AND address = ?', [
      'eip155:1',
      address
    ], function(err, row) {
      if (err) { return cb(err); }
      if (!row) {
        db.run('INSERT INTO users (username) VALUES (?)', [
          address
        ], function(err) {
          if (err) { return cb(err); }
          var id = this.lastID;
          db.run('INSERT INTO blockchain_credentials (user_id, chain, address) VALUES (?, ?, ?)', [
            id,
            'eip155:1',
            address
          ], function(err) {
            if (err) { return cb(err); }
            var user = {
              id: id,
              username: address
            };
            return cb(null, user);
          });
        });
      } else {
        db.get('SELECT rowid AS id, * FROM users WHERE rowid = ?', [ row.user_id ], function(err, row) {
          if (err) { return cb(err); }
          if (!row) { return cb(null, false); }
          return cb(null, row);
        });
      }
    });
  }
));

Define Routes

Two routes are needed in order to allow users to log in with their Ethereum wallet.

The first route generates a randomized nonce, saves it in the NonceStore, and sends it to the client-side JavaScript for it to be included in the signed message. This is necessary in order to protect against replay attacks.

router.post('/login/ethereum/challenge', function(req, res, next) {
  store.challenge(req, function(err, nonce) {
    if (err) { return next(err); }
    res.json({ nonce: nonce });
  });
});

The second route authenticates the signed message and logs the user in.

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

Examples

• todos-express-ethereum

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

License

The MIT License

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