letmein

letmein is a minimalistic authentication plugin for Rails 3 applications. It doesn't have anything other than the UserSession (or WhateverSession) object that you can use to authenticate logins.

Setup

Plug the thing below into Gemfile and you know what to do after.

gem 'letmein'

If you want to authenticate User with database fields email, password_hash and password_salt you don't need to do anything. If you're authenticating something else, you want something like this in your initializers:

LetMeIn.configure do |conf|
  conf.model      = 'Account'
  conf.attribute  = 'username'
  conf.password   = 'password_crypt'
  conf.salt       = 'salty_salt'
end

When creating/updating a record you have access to password accessor.

>> user = User.new(:email => 'example@example.com', :password => 'letmein')
>> user.save!
=> true
>> user.password_hash 
=> $2a$10$0MeSaaE3I7.0FQ5ZDcKPJeD1.FzqkcOZfEKNZ/DNN.w8xOwuFdBCm
>> user.password_salt
=> $2a$10$0MeSaaE3I7.0FQ5ZDcKPJe

Authentication

You authenticate using UserSession object. Example:

>> session = UserSession.new(:email => 'example@example.com', :password => 'letmein')
>> session.save
=> true
>> session.user
=> #<User id: 1, email: "example@example.com" ... >

When credentials are invalid:

>> session = UserSession.new(:email => 'example@example.com', :password => 'bad_password')
>> session.save
=> false
>> session.user
=> nil

Usage

There are no built-in routes/controllers/views/helpers or anything. I'm confident you can do those yourself, because you're awesome. But here's an example how you can implement the controller handling the login:

class SessionsController < ApplicationController
  def create
    @session = UserSession.new(params[:user_session])
    @session.save!
    session[:user_id] = @session.user.id
    flash[:notice] = "Welcome back #{@session.user.name}!"
    redirect_to '/'
    
  rescue LetMeIn::Error
    flash.now[:error] = 'Invalid Credentials'
    render :action => :new
  end
end

Upon successful login you have access to session[:user_id]. The rest is up to you.

Authenticating Multiple Models

Yes, you can do that too. Let's assume you also want to authenticate admins that don't have email addresses, but have usernames.

LetMeIn.configure do |conf|
  conf.models     = ['User', 'Admin']
  conf.attributes = ['email', 'username']
end

Bam! You're done. Now you have an AdminSession object that will use username and password to authenticate.

Token-Based Authentication

Token authentication provides a simple solution for exposing APIs. When enabled, Letmein will automatically generate a token (40 character hex) for each new user. Instead of passing email and password to the UserSession, you merely pass auth_token. To enable tokens:

LetMeIn.configure do |conf|
  conf.generate_token = true
end

Its usage differs from the email/password combo in only one way:

@session = UserSession.new(:auth_token => "258082e5588dea110592154f48ef1e309a8bbff5")

This will successfully (or not) authenticate you with the token above.

Overriding Session Authentication

By default user will be logged in if provided email and password match. If you need to add a bit more logic to that you'll need to create your own session object. In the following example we do an additional check to see if user is 'approved' before letting him in.

class MySession < LetMeIn::Session
  # Model that is being authenticated is derived from the class name
  # If you're authenticating multiple models you need to specify which one
  @model = 'User'
  
  def authenticate
    super # need to authenticate with email/password first
    unless user && user.is_approved?
      # adding a validation error will prevent login
      errors.add :base, "You are not approved yet, #{user.name}."
    end
  end
end

Copyright

(c) 2011 Oleg Khabarov, released under the MIT license