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Authie

This is a Rails library which provides applications with a database-backed user sessions. This ensures that user sessions can be invalidated from the server and users activity can be easily tracked.

The "traditional" way of simply setting a user ID in your session is insecure and unwise. If you simply do something like the example below, it means that anyone with access to the session cookie can login as the user whenever and wherever they wish.

To clarify: while by default Rails session cookies are encrypted, there is nothing to allow them to be invalidated if someone were to "steal" an encrypted cookie from an authenticated user. This could be stolen using a MITM attack or simply by stealing it directly from their browser when they're off getting a coffee.

if user = User.authenticate(params[:username], params[:password])
  # Don't do this...
  session[:user_id] = user.id
  redirect_to root_path, :notice => "Logged in successfully!"
end

The design goals behind Authie are:

  • Any session can be invalidated instantly from the server without needing to make changes to remote cookies.
  • We can see who is logged in to our application at any point in time.
  • Sessions should automatically expire after a certain period of inactivity.
  • Sessions can be either permanent or temporary.

Installation

As usual, just pop this in your Gemfile:

gem 'authie', '~> 4.0'

You will then need add the database tables Authie needs to your database. You should copy Authie's migrations and then migrate.

rake authie:install:migrations
rake db:migrate

Usage

Authie is just a session manager and doesn't provide any functionality for your authentication or User models. Your User model should implement any methods needed to authenticate a username & password.

Creating a new session

When a user has been authenticated, you can simply set current_user to the user you wish to login. You may have a method like this in a controller.

class SessionsController < ApplicationController

  def create
    if user = User.authenticate(params[:username], params[:password])
      create_auth_session(user)
      redirect_to root_path
    else
      flash.now[:alert] = "Username/password was invalid"
    end
  end

end

Checking whether user's are logged in

On any subsequent request, you should make sure that your user is logged in. You may wish to implement a login_required controller method which is called before every action in your application.

class ApplicationController < ActionController::Base

  before_action :login_required

  private

  def login_required
    return if logged_in?

    redirect_to login_path, :alert => "You must login to view this resource"
  end

end

Accessing the current user (and session)

There are a few controller methods which you can call which will return information about the current session:

  • current_user - returns the currently logged in user
  • auth_session - returns the current auth session
  • logged_in? - returns a true if there's a session or false if no user is logged in

Catching session errors

If there is an issue with an auth session, an error will be raised which you need to catch within your application. The errors which will be raised are:

  • Authie::Session::InactiveSession - is raised when a session has been de-activated.
  • Authie::Session::ExpiredSession - is raised when a session expires.
  • Authie::Session::BrowserMismatch - is raised when the browser ID provided does not match the browser ID associated with the session token provided.
  • Authie::Session::HostMismatch - is raised when the session is used on a hostname that does not match that which created the session

The easiest way to rescue these to use a rescue_from. For example:

class ApplicationController < ActionController::Base

  rescue_from Authie::Session::ValidityError, :with => :auth_session_error

  private

  def auth_session_error
    redirect_to login_path, :alert => "Your session is no longer valid. Please login again to continue..."
  end

end

Logging out

In order to invalidate a session you can simply invalidate it.

def logout
  auth_session.invalidate
  redirect_to login_path, :notice => "Logged out successfully."
end

Default session length

By default, a session will last for however long it is being actively used in browser. If the user stops using your application, the session will last for 12 hours before becoming invalid. You can change this:

Authie.config.session_inactivity_timeout = 2.hours

This does not apply if the session is marked as persistent. See below.

Persisting sessions

In some cases, you may wish users to have a permanent sessions. In this case, you should ask users after they have logged in if they wish to "persist" their session across browser restarts. If they do wish to do this, just do something like this:

def persist_session
  auth_session.persist
  redirect_to root_path, :notice => "You will now be remembered!"
end

By default, persistent sessions will last for 2 months before requring the user logs in again. You can increase (or decrease) this if needed:

Authie.config.persistent_session_length = 12.months

Accessing all user sessions

If you want to provide users with a list of their sessions, you can access all active sessions for a user. The best way to do this will be to add a has_many association to your User model.

class User < ActiveRecord::Base
  has_many :sessions, :class_name => 'Authie::SessionModel', :as => :user, :dependent => :destroy
end

Storing additional data in the user session

If you need to store additional information in your database-backed database session, then you can use the following methods to achieve this:

auth_session.set :two_factor_seen_at, Time.now
auth_session.get :two_factor_seen_at

Invalidating all but current session

You may wish to allow users to easily invalidate all sessions which aren't their current one. Some applications invalidate old sessions whenever a user changes their password. The invalidate_others! method can be called on any Authie::Session object and will invalidate all sessions which aren't itself.

def change_password
  @user.change_password(params[:new_password])
  auth_session.invalidate_others!
end

Sudo functions

In some applications, you may want to require that the user has recently provided their password to you before executing certain sensitive actions. Authie provides some methods which can help you keep track of when a user last provided their password in a session and whether you need to prompt them before continuing.

# When the user logs into your application, run the see_password method to note
# that we have just seen their password.
def login
  if user = User.authenticate(params[:username], params[:password])
    create_auth_session(user, see_password: true)
    redirect_to root_path
  end
end

# Before executing any dangerous actions, check to see whether the password has
# recently been seen.
def change_password
  if auth_session.recently_seen_password?
    # Allow the user to change their password as normal.
  else
    # Redirect the user a page which allows them to re-enter their password.
    # The method here should verify the password is correct and call the
    # see_password method as above. Once verified, you can return them back to
    # this page.
    redirect_to reauth_path(:return_to => request.fullpath)
  end
end

By default, a password will be said to have been recently seen if it has been seen in the last 10 minutes. You can change this configuration if needed:

Authie.config.sudo_session_timeout = 30.minutes

Working with two factor authentication

Authie provides a couple of methods to help you determine when two factor authentication is required for a request. Whenever a user logs in and has enabled two factor authentication, you can mark sessions as being permitted.

You can add the following to your application controller and ensure that it runs on every request to your application.

class ApplicationController < ActionController::Base

  before_action :check_two_factor_auth

  def check_two_factor_auth
    if logged_in? && current_user.has_two_factor_auth? && !auth_session.two_factored?
      # If the user has two factor auth enabled, and we haven't already checked it
      # in this auth session, redirect the user to an action which prompts the user
      # to do their two factor auth check.
      redirect_to two_factor_auth_path
    end
  end

end

Then, on your two factor auth action, you need to ensure that you mark the auth session as being verified with two factor auth.

class LoginController < ApplicationController

  skip_before_action :check_two_factor_auth

  def two_factor_auth
    if user.verify_two_factor_token(params[:token])
      auth_session.mark_as_two_factored
      redirect_to root_path, :notice => "Logged in successfully!"
    end
  end

end

Storing IP address countries

Authie has support for storing the country that an IP address is located in whenever they are saved to the database. To use this, you need to specify a backend to use in the Authie configuration. The backend should respond to #call(ip_address).

Authie.config.lookup_ip_country_backend = proc do |ip_address|
  SomeService.lookup_country_from_ip(ip_address)
end

Instrumentation/Notification

Authie will publish events to the ActiveSupport::Notification instrumentation system. The following events are published with the given attributes.

  • set_browser_id.authie - when a new browser ID is set for a user. Provides :browser_id and :controller arguments.
  • cleanup.authie - when session cleanup is run. Provides no arguments.
  • touch.authie - when a session is touched. Provides :session argument.
  • see_password.authie - when a session sees a password. Provides :session argument.
  • mark_as_two_factor.authie - when a session has two factor credentials provided. Provides :session argument.
  • session_start.authie - when a session is started. Provides :session argument.
  • session_invalidate.authie - when a session is intentionally invalidated. Provides :session argument with session model instance.
  • browser_id_mismatch_error.authie - when a session is validated when the browser ID does not match. Provides :session argument.
  • invalid_session_error.authie - when a session is validated when invalid. Provides :session argument.
  • expired_session_error.authie - when a session is validated when expired. Provides :session argument.
  • inactive_session_error.authie - when a session is validated when inactive. Provides :session argument.
  • host_mismatch_error.authie - when a session is validated and the host does not match. Provides :session argument.

Differences for Authie 4.0

Authie 4.0 introduces a number of changes to the library which are worth noting when upgrading from any version less than 4.

  • Authie 4.0 removes the impersonation features which may make a re-appearance in a futre version.
  • All previous callback/events have been replaced with standard ActiveSupport instrumentation notifications.
  • Authie::SessionModel has been introduced to represent the instance of the underlying database record.
  • Various methods on Authie::Session (more commonly known as auth_session) have been renamed as follows.
    • check_security! is now validate
    • persist! is now persist
    • invalidate! is now invalidate
    • touch! is now touch
    • set_cookie! is now set_cookie and is now a private method and should not be called directly.
    • see_password! is now see_password
    • mark_as_two_factored! is now mark_as_two_factored
  • A new Authie::Session#reset_token has been added which will generate a new token for a session, save it and update the cookie.
  • When starting a session using Authie::Session.start or create_auth_session you can provide the following additional options:
    • persistent: true to mark the session as persistent (i.e. give it an expiry time)
    • see_password: true to set the password seen timestamp at the same time as creation
  • If the extend_session_expiry_on_touch config option is set to true (default is false), the expiry time for a persistent session will be extended whenver a session is touched.
  • When making a request, the session will be touched after the action rather than before. Previously, the touch_auth_session method was added before every action and it both validated the session and touched it. Now, there are two separate methods - validate_auth_session which is run before every action and touch_auth_session runs after every action. If you don't want to touch a session in a request you can either use skip_around_action :touch_auth_session or call skip_touch_auth_session! anywhere in the action.
  • A new config option called session_token_length is available which allows you to change the length of the random token used for sessions (default 64).