node-auth.js

var username, password, creds;
var challenge = function( res ) {
  res.writeHead( 401, { 'WWW-Authenticate': 'Basic realm="Acme Web Application"'} );
  res.end();
};
if ( req.headers.authorization ) {
  creds = new Buffer(req.headers.authorization.split(' ')[1], 'base64').toString('utf8').split(':');
  username = creds[0];
  password = creds[1];
  // authenticate here
} else {
  challenge(res);
}