How to log out from basicAuth (Express)

Express' basicAuth uses HTTP Basic Authentication whose implementation doesn't need HTML pages, cookies nor session ids. Its main drawbacks are its not secure and, our concern here, there is no mechanism in the spec for the server to instruct the browser to log out.

express.basicAuth() calls require(blah-blah/connect/lib/utils).unauthorized() which sends a 401 status with header 'WWW-Authenticate: Basic realm="..."'. The browser handles the authentication window and from then on sends a header like 'Authorization: Basic YmFzaWM6YmFzaWM=' which contains the username and password.

(express.basicAuth is not secure, especially over HTTP, because you can get the username:password with

new Buffer('YmFzaWM6YmFzaWM=' , 'base64').toString() 

which gives basic:basic in this case.)

Our problem is the HTTP spec does not provide a way to stop that header being sent. A workaround for HTTPS is to redirect the user to a URL on the same domain having incorrect credentials.

The HTTP workaround I use for Express V3 can be used with app.use(express.basicAuth(...)). I find this easier to use than other solutions which require a call to middleware in every secured route, e.g. app.get('/secure', checkAuth, function (req, res) {...}).

Here is a working example.

var express = require('express'),
    http = require('http'),
    app = express();

app.use(express.favicon()); // prevent interference during test
app.use(express.bodyParser());
app.use(express.cookieParser());
app.use(express.session({ secret: 'winter is coming' }));

app.use(function (req, res, next) {
  if (!req.session.authStatus || 'loggedOut' === req.session.authStatus) {
    req.session.authStatus = 'loggingIn';

    // cause Express to issue 401 status so browser asks for authentication
    req.user = false;
    req.remoteUser = false;
    if (req.headers && req.headers.authorization) { delete req.headers.authorization; }
  }
  next();
});
app.use(express.basicAuth(function(user, pass, callback) {
  callback(null, user === 'basic' && pass === 'basic');
}, '***** Enter user= basic & password= basic'));
app.use(function (req, res, next) {
  req.session.authStatus = 'loggedIn';
  next();
});

app.use(app.router);
app.get('/secure', function (req, res) {
  res.send([
    'You are on a secured page.',
    '<br>',
    '<a href="./secure">Refresh this page without having to log in again.</a>',
    '&lt;br/>',
    '<a href="./logout">Log out.</a>'
  ].join(''));
});
app.get('/logout', function (req, res) {
  delete req.session.authStatus;
  res.send([
    'You are now logged out.',
    '&lt;br/>',
    '<a href="./secure">Return to the secure page. You will have to log in again.</a>',
  ].join(''));
});

http.createServer(app).listen(3000, function(){
  console.log('Express server listening on port 3000. Point browser to route /secure');
});

P.S. Your English is excellent.

For express.js 4 and basicAuth, you can use this method:

app.get('/logout', function (req, res) {
    res.set('WWW-Authenticate', 'Basic realm=Authorization Required');
    return res.sendStatus(401);
});