ad.js

function login(login, password){
  return new Promise(function(resolve, reject){
    ad.findUserAsync(login)
      .then(function(user){
        var context = {
          user: user,
          password: password
        };
        return resolve(context);
      })
      .catch(function(err){
        return reject(err);
      });
  });
}

function authenticate(context){
  return new Promise(function(resolve, reject){
    ad.authenticateAsync(context.user.mail, context.password)
      .then(function(auth){
        context.auth = auth
        return resolve(context);
      })
      .catch(function(err){
        return reject(err);
      });
  })
}

login(username, password)
      .then(authenticate)
      .then(function(context){
        if(!context.auth) return res.status(403).send({"message": "user not authenticated"});
        return res.status(200).send({"message": "user authenticated","data": context.user});
      })
      .catch(function(err){
        return next(err);
      });