Add support for remembering a user's 2FA session in a cookie

This makes the gem store a signed cookie for a configurable amount of
time that allows the user to bypass 2FA. Our use-case for this is that
we expire user’s Devise sessions after 12 hours, but don’t want to
force them to authenticate using 2FA every day.

Signed cookies are available since Rails 3. This requires the signing
functionality to be properly configured, but is disabled by setting the
config variable to `0`, the default.

README.md

@@ -9,6 +9,7 @@
 * configure max login attempts
 * per user level control if he really need two factor authentication
 * your own sms logic
+* configurable period where users won't be asked for 2FA again
 
 ## Configuration
 
@@ -38,12 +39,13 @@ Add the following line to your model to fully enable two-factor auth:
 
     has_one_time_password
 
-Set config values, if desired, for maximum second factor attempts count, allowed time drift, and OTP length.
+Set config values, if desired:
 
 ```ruby
-config.max_login_attempts = 3
+config.max_login_attempts = 3  # Maximum second factor attempts count
-config.allowed_otp_drift_seconds = 30
+config.allowed_otp_drift_seconds = 30  # Allowed time drift
-config.otp_length = 6
+config.otp_length = 6  # OTP code length
+config.remember_otp_session_for_seconds = 30.days  # Time before browser has to enter OTP code again
 ```
 
 Override the method to send one-time passwords in your model, this is automatically called when a user logs in:
@@ -67,12 +69,13 @@ Add the following line to your model to fully enable two-factor auth:
 
     has_one_time_password
 
-Set config values, if desired, for maximum second factor attempts count, allowed time drift, and OTP length.
+Set config values, if desired:
 
 ```ruby
-config.max_login_attempts = 3
+config.max_login_attempts = 3  # Maximum second factor attempts count
-config.allowed_otp_drift_seconds = 30
+config.allowed_otp_drift_seconds = 30  # Allowed time drift
-config.otp_length = 6
+config.otp_length = 6  # OTP code length
+config.remember_otp_session_for_seconds = 30.days  # Time before browser has to enter OTP code again
 ```
 
 Override the method to send one-time passwords in your model, this is automatically called when a user logs in:

app/controllers/devise/two_factor_authentication_controller.rb

@@ -9,6 +9,13 @@ class Devise::TwoFactorAuthenticationController < DeviseController
     render :show and return if params[:code].nil?
 
     if resource.authenticate_otp(params[:code])
+      expires_seconds = resource.class.remember_otp_session_for_seconds
+      if expires_seconds && expires_seconds > 0
+        cookies.signed[TwoFactorAuthentication::REMEMBER_TFA_COOKIE_NAME] = {
+          value: true,
+          expires: expires_seconds.from_now
+        }
+      end
       warden.session(resource_name)[TwoFactorAuthentication::NEED_AUTHENTICATION] = false
       sign_in resource_name, resource, :bypass => true
       set_flash_message :notice, :success

lib/two_factor_authentication.rb

@@ -16,10 +16,14 @@ module Devise
 
   mattr_accessor :otp_length
   @@otp_length = 6
+
+  mattr_accessor :remember_otp_session_for_seconds
+  @@remember_otp_session_for_seconds = 0
 end
 
 module TwoFactorAuthentication
   NEED_AUTHENTICATION = 'need_two_factor_authentication'
+  REMEMBER_TFA_COOKIE_NAME = "remember_tfa"
 
   autoload :Schema, 'two_factor_authentication/schema'
   module Controllers

lib/two_factor_authentication/hooks/two_factor_authenticatable.rb

@@ -1,5 +1,6 @@
 Warden::Manager.after_authentication do |user, auth, options|
-  if user.respond_to?(:need_two_factor_authentication?)
+  if user.respond_to?(:need_two_factor_authentication?) &&
+      !auth.env["action_dispatch.cookies"].signed[TwoFactorAuthentication::REMEMBER_TFA_COOKIE_NAME]
     if auth.session(options[:scope])[TwoFactorAuthentication::NEED_AUTHENTICATION] = user.need_two_factor_authentication?(auth.request)
       user.send_two_factor_authentication_code
     end

lib/two_factor_authentication/models/two_factor_authenticatable.rb

@@ -20,7 +20,7 @@ module Devise
             end
           end
         end
-        ::Devise::Models.config(self, :max_login_attempts, :allowed_otp_drift_seconds, :otp_length)
+        ::Devise::Models.config(self, :max_login_attempts, :allowed_otp_drift_seconds, :otp_length, :remember_otp_session_for_seconds)
       end
 
       module InstanceMethodsOnActivation

spec/features/two_factor_authenticatable_spec.rb

@@ -84,5 +84,43 @@ feature "User of two factor authentication" do
       expect(page).to have_content("Access completely denied")
       expect(page).to have_content("You are signed out")
     end
+
+    describe "rememberable TFA" do
+      before do
+        @original_remember_otp_session_for_seconds = User.remember_otp_session_for_seconds
+        User.remember_otp_session_for_seconds = 30.days
+      end
+
+      after do
+        User.remember_otp_session_for_seconds = @original_remember_otp_session_for_seconds
+      end
+
+      scenario "doesn't require TFA code again within 30 days" do
+        visit user_two_factor_authentication_path
+        fill_in "code", with: user.otp_code
+        click_button "Submit"
+
+        logout
+
+        login_as user
+        visit dashboard_path
+        expect(page).to have_content("Your Personal Dashboard")
+        expect(page).to have_content("You are signed in as Marissa")
+      end
+
+      scenario "requires TFA code again after 30 days" do
+        visit user_two_factor_authentication_path
+        fill_in "code", with: user.otp_code
+        click_button "Submit"
+
+        logout
+
+        Timecop.travel(30.days.from_now)
+        login_as user
+        visit dashboard_path
+        expect(page).to have_content("You are signed in as Marissa")
+        expect(page).to have_content("Enter your personal code")
+      end
+    end
   end
 end

spec/spec_helper.rb

@@ -2,6 +2,7 @@ ENV["RAILS_ENV"] ||= "test"
 require File.expand_path("../rails_app/config/environment.rb",  __FILE__)
 
 require 'rspec/rails'
+require 'timecop'
 
 # See http://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
 RSpec.configure do |config|
@@ -17,6 +18,8 @@ RSpec.configure do |config|
   # the seed, which is printed after each run.
   #     --seed 1234
   config.order = 'random'
+
+  config.after(:each) { Timecop.return }
 end
 
 Dir["#{Dir.pwd}/spec/support/**/*.rb"].each {|f| require f}

two_factor_authentication.gemspec

@@ -34,4 +34,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec-rails', '>= 3.0.1'
   s.add_development_dependency 'capybara', '2.4.1'
   s.add_development_dependency 'pry'
+  s.add_development_dependency 'timecop'
 end