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express-common-wallet

Express middleware for supporting authentication of Common Wallet remote requests.

About

This module interfaces with Bitcoin wallets that support the Common Wallet interface.

Specifically, it interfaces with the commonWallet.login function, which authenticates with the server by retrieving and signing a nonce with commonWallet.signMessage, and commonWallet.request, which wraps the request module with authentication headers related to these signed nonces.

As a precaution against replay attacks a new nonce is created after every request.

Usage

Express server

npm install express-common-wallet

This express router middleware requires a permanent key-value store to associate public Bitcoin wallet addresses with a randomly generated nonce.

For this example, we'll use a simple in-memory store, but we recommend using something like DynamoDB, Redis or Postgres.

var __nonces = {};
var commonWalletNonceStore = {
  get: function(address, callback) {
    callback(false, __nonces[address]);
  },
  set: function(address, nonce, callback) {
    __nonces[address] = nonce;
    callback(false, true);
  }
}

This commonWalletNonceStore is passed in as an option to an instance of our Express router middleware.

It creates a /nonce route at the root of the application, which is used by compatible clients to

var express = require('express');
var expressCommonWallet = require('express-common-wallet');

var app = express();

app.use("/", expressCommonWallet({
  commonWalletNonceStore: commonWalletNonceStore
}));

Using a compatible client will result in a req.verifiedAddress attribute added to the express request object, allowing for additional routes to check for authorized wallets.

app.get("/test", function(req, res) {
  var verifiedAddress = req.verifiedAddress;
  if (!verifiedAddress) {
    return res.status(401).send("Unauthorized");
  } 
  ...
});

commonWallet client

Compliant commonWallet clients have support for both login() and request() functions that are compatible with this module.

In this example we'll be using the test-common-wallet reference implementation.

var commonBlockchain = require('mem-common-blockchain');
var testCommonWallet = require('test-common-wallet');

var commonWallet = testCommonWallet({
  seed: "testing123",
  network: "testnet",
  commonBlockchain: commonBlockchain
});

login

This function retrieves and stores a nonce from the /nonce route created by the expressCommonWallet router middleware.

commonWallet.login("http://localhost:5454", function(err, res, body) {
  
});

request

This function wraps the request module with various headers that return the nonce signed by the commonWallet.

commonWallet.request({host: "http://localhost:5454", path: "/test" }, function(err, res, body) {

});

This method should support the full API for request, including the POST method.

commonWallet.request({host: "http://localhost:5454", path: "/testPost/", method:"POST", form: {"key": "value"} }, function(err, res, body) {

});

For more information about the implementation details, please consult the tests in abstract-common-wallet as well as the reference implementation in test-common-wallet.