Prevent reuse of TOTP codes (#94)

This change updates the rotp version which now includes support
for preventing TOTP code reuse via tracking the timestamp
of the last used code.

README.md

@@ -33,6 +33,7 @@ Note that Ruby 2.1 or greater is required.
 ### Installation
 
 #### Automatic initial setup
+
 To set up the model and database migration file automatically, run the
 following command:
 
@@ -48,8 +49,10 @@ migration in `db/migrate/`, which will add the following columns to your table:
 - `:encrypted_otp_secret_key_salt`
 - `:direct_otp`
 - `:direct_otp_sent_at`
+- `:totp_timestamp`
 
 #### Manual initial setup
+
 If you prefer to set up the model and migration manually, add the
 `:two_factor_authentication` option to your existing devise options, such as:
 
@@ -61,7 +64,7 @@ devise :database_authenticatable, :registerable, :recoverable, :rememberable,
 Then create your migration file using the Rails generator, such as:
 
 ```
-rails g migration AddTwoFactorFieldsToUsers second_factor_attempts_count:integer encrypted_otp_secret_key:string:index encrypted_otp_secret_key_iv:string encrypted_otp_secret_key_salt:string direct_otp:string direct_otp_sent_at:datetime
+rails g migration AddTwoFactorFieldsToUsers second_factor_attempts_count:integer encrypted_otp_secret_key:string:index encrypted_otp_secret_key_iv:string encrypted_otp_secret_key_salt:string direct_otp:string direct_otp_sent_at:datetime totp_timestamp:timestamp
 ```
 
 Open your migration file (it will be in the `db/migrate` directory and will be
@@ -74,6 +77,7 @@ add_index :users, :encrypted_otp_secret_key, unique: true
 Save the file.
 
 #### Complete the setup
+
 Run the migration with:
 
     bundle exec rake db:migrate
@@ -129,7 +133,7 @@ method on your model:
 user.generate_totp_secret
 ```
 
-This can then be shared via a provisioning uri:
+This must then be shared via a provisioning uri:
 
 ```ruby
 user.provisioning_uri # This assumes a user model with an email attribute

lib/generators/active_record/templates/migration.rb

@@ -6,6 +6,7 @@ class TwoFactorAuthenticationAddTo<%= table_name.camelize %> < ActiveRecord::Mig
     add_column :<%= table_name %>, :encrypted_otp_secret_key_salt, :string
     add_column :<%= table_name %>, :direct_otp, :string
     add_column :<%= table_name %>, :direct_otp_sent_at, :datetime
+    add_column :<%= table_name %>, :totp_timestamp, :timestamp
 
     add_index :<%= table_name %>, :encrypted_otp_secret_key, unique: true
   end

lib/two_factor_authentication/models/two_factor_authenticatable.rb

@@ -16,7 +16,7 @@ module Devise
         ::Devise::Models.config(
           self, :max_login_attempts, :allowed_otp_drift_seconds, :otp_length,
           :remember_otp_session_for_seconds, :otp_secret_encryption_key,
-          :direct_otp_length, :direct_otp_valid_for)
+          :direct_otp_length, :direct_otp_valid_for, :totp_timestamp)
       end
 
       module InstanceMethodsOnActivation
@@ -38,7 +38,10 @@ module Devise
           drift = options[:drift] || self.class.allowed_otp_drift_seconds
           raise "authenticate_totp called with no otp_secret_key set" if totp_secret.nil?
           totp = ROTP::TOTP.new(totp_secret, digits: digits)
-          totp.verify_with_drift(code, drift)
+          new_timestamp = totp.verify_with_drift_and_prior(code, drift, totp_timestamp)
+          return false unless new_timestamp
+          self.totp_timestamp = new_timestamp
+          true
         end
 
         def provisioning_uri(account = nil, options = {})

lib/two_factor_authentication/schema.rb

@@ -23,5 +23,9 @@ module TwoFactorAuthentication
     def direct_otp_sent_at
       apply_devise_schema :direct_otp_sent_at, DateTime
     end
+
+    def totp_timestamp
+      apply_devise_schema :totp_timestamp, Timestamp
+    end
   end
 end

spec/lib/two_factor_authentication/models/two_factor_authenticatable_spec.rb

@@ -70,10 +70,10 @@ describe Devise::Models::TwoFactorAuthenticatable do
   end
 
   describe '#authenticate_totp' do
-
     shared_examples 'authenticate_totp' do |instance|
       before :each do
         instance.otp_secret_key = '2z6hxkdwi3uvrnpn'
+        instance.totp_timestamp = nil
         @totp_helper = TotpHelper.new(instance.otp_secret_key, instance.class.otp_length)
       end
 
@@ -90,6 +90,12 @@ describe Devise::Models::TwoFactorAuthenticatable do
         code = @totp_helper.totp_code(1.minutes.ago.to_i)
         expect(do_invoke(code, instance)).to eq(false)
       end
+
+      it 'prevents code reuse' do
+        code = @totp_helper.totp_code
+        expect(do_invoke(code, instance)).to eq(true)
+        expect(do_invoke(code, instance)).to eq(false)
+      end
     end
 
     it_behaves_like 'authenticate_totp', GuestUser.new

spec/rails_app/app/models/encrypted_user.rb

@@ -8,7 +8,8 @@ class EncryptedUser
                 :encrypted_otp_secret_key_iv,
                 :encrypted_otp_secret_key_salt,
                 :email,
-                :second_factor_attempts_count
+                :second_factor_attempts_count,
+                :totp_timestamp
 
   has_one_time_password(encrypted: true)
 end

spec/rails_app/app/models/guest_user.rb

@@ -5,7 +5,7 @@ class GuestUser
 
   define_model_callbacks :create
   attr_accessor :direct_otp, :direct_otp_sent_at, :otp_secret_key, :email,
-    :second_factor_attempts_count
+    :second_factor_attempts_count, :totp_timestamp
 
   def update_attributes(attrs)
     attrs.each do |key, value|

spec/support/authenticated_model_helper.rb

@@ -49,6 +49,7 @@ module AuthenticatedModelHelper
           t.string    'otp_secret_key'
           t.string    'direct_otp'
           t.datetime  'direct_otp_sent_at'
+          t.timestamp 'totp_timestamp'
         end
       end
     end

two_factor_authentication.gemspec

@@ -27,7 +27,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency 'rails', '>= 3.1.1'
   s.add_runtime_dependency 'devise'
   s.add_runtime_dependency 'randexp'
-  s.add_runtime_dependency 'rotp'
+  s.add_runtime_dependency 'rotp', '>= 3.2.0'
   s.add_runtime_dependency 'encryptor'
 
   s.add_development_dependency 'bundler'