Two factor authentication for Devise

Features

• Support for 2 types of OTP codes

1. Codes delivered directly to the user
2. TOTP (Google Authenticator) codes based on a shared secret (HMAC)

• Configurable OTP code digit length
• Configurable max login attempts
• Customizable logic to determine if a user needs two factor authentication
• Configurable period where users won't be asked for 2FA again
• Option to encrypt the TOTP secret in the database, with iv and salt

Configuration

Initial Setup

In a Rails environment, require the gem in your Gemfile:

gem 'two_factor_authentication'

Once that's done, run:

bundle install

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:

bundle exec rails g two_factor_authentication MODEL

Where MODEL is your model name (e.g. User or Admin). This generator will add :two_factor_authenticatable to your model's Devise options and create a migration in db/migrate/, which will add the following columns to your table:

• :second_factor_attempts_count
• :encrypted_otp_secret_key
• :encrypted_otp_secret_key_iv
• :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:

devise :database_authenticatable, :registerable, :recoverable, :rememberable,
       :trackable, :validatable, :two_factor_authenticatable

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 totp_timestamp:timestamp

Open your migration file (it will be in the db/migrate directory and will be named something like 20151230163930_add_two_factor_fields_to_users.rb), and add unique: true to the add_index line so that it looks like this:

add_index :users, :encrypted_otp_secret_key, unique: true

Save the file.

Complete the setup

Run the migration with:

bundle exec rake db:migrate

Add the following line to your model to fully enable two-factor auth:

has_one_time_password(encrypted: true)

Set config values in config/initializers/devise.rb:

config.max_login_attempts = 3  # Maximum second factor attempts count.
config.allowed_otp_drift_seconds = 30  # Allowed TOTP time drift between client and server.
config.otp_length = 6  # TOTP code length
config.direct_otp_valid_for = 5.minutes  # Time before direct OTP becomes invalid
config.direct_otp_length = 6  # Direct OTP code length
config.remember_otp_session_for_seconds = 30.days  # Time before browser has to perform 2fA again. Default is 0.
config.otp_secret_encryption_key = ENV['OTP_SECRET_ENCRYPTION_KEY']
config.second_factor_resource_id = 'id' # Field or method name used to set value for 2fA remember cookie
config.delete_cookie_on_logout = false # Delete cookie when user signs out, to force 2fA again on login

The otp_secret_encryption_key must be a random key that is not stored in the DB, and is not checked in to your repo. It is recommended to store it in an environment variable, and you can generate it with bundle exec rake secret.

Override the method in your model in order to send direct OTP codes. This is automatically called when a user logs in unless they have TOTP enabled (see below):

def send_two_factor_authentication_code(code)
  # Send code via SMS, etc.
end

Customisation and Usage

By default, second factor authentication is required for each user. You can change that by overriding the following method in your model:

def need_two_factor_authentication?(request)
  request.ip != '127.0.0.1'
end

In the example above, two factor authentication will not be required for local users.

This gem is compatible with Google Authenticator. To enable this a shared secret must be generated by invoking the following method on your model:

user.generate_totp_secret

This must then be shared via a provisioning uri:

user.provisioning_uri # This assumes a user model with an email attribute

This provisioning uri can then be turned in to a QR code if desired so that users may add the app to Google Authenticator easily. Once this is done, they may retrieve a one-time password directly from the Google Authenticator app.

Overriding the view

The default view that shows the form can be overridden by adding a file named show.html.erb (or show.html.haml if you prefer HAML) inside app/views/devise/two_factor_authentication/ and customizing it. Below is an example using ERB:

<h2>Hi, you received a code by email, please enter it below, thanks!</h2>

<%= form_tag([resource_name, :two_factor_authentication], :method => :put) do %>
  <%= text_field_tag :code %>
  <%= submit_tag "Log in!" %>
<% end %>

<%= link_to "Sign out", destroy_user_session_path, :method => :delete %>

Upgrading from version 1.X to 2.X

The following database fields are new in version 2.

• direct_otp
• direct_otp_sent_at
• totp_timestamp

To add them, generate a migration such as:

$ rails g migration AddTwoFactorFieldsToUsers direct_otp:string direct_otp_sent_at:datetime totp_timestamp:timestamp

The otp_secret_key is only required for users who use TOTP (Google Authenticator) codes, so unless it has been shared with the user it should be set to nil. The following pseudo-code is an example of how this might be done:

User.find_each do |user| do
  if !uses_authenticator_app(user)
    user.otp_secret_key = nil
    user.save!
  end
end

Adding the TOTP encryption option to an existing app

If you've already been using this gem, and want to start encrypting the OTP secret key in the database (recommended), you'll need to perform the following steps:

1. Generate a migration to add the necessary columns to your model's table:

   rails g migration AddEncryptionFieldsToUsers encrypted_otp_secret_key:string:index encrypted_otp_secret_key_iv:string encrypted_otp_secret_key_salt:string
   

   Open your migration file (it will be in the db/migrate directory and will be named something like 20151230163930_add_encryption_fields_to_users.rb), and add unique: true to the add_index line so that it looks like this:

   add_index :users, :encrypted_otp_secret_key, unique: true

   Save the file.

2. Run the migration: bundle exec rake db:migrate

3. Update the gem: bundle update two_factor_authentication

4. Add encrypted: true to has_one_time_password in your model. For example: has_one_time_password(encrypted: true)

5. Generate a migration to populate the new encryption fields:

   rails g migration PopulateEncryptedOtpFields
   

   Open the generated file, and replace its contents with the following:

   class PopulateEncryptedOtpFields < ActiveRecord::Migration
      def up
        User.reset_column_information
   
        User.find_each do |user|
          user.otp_secret_key = user.read_attribute('otp_secret_key')
          user.save!
        end
      end
   
      def down
        User.reset_column_information
   
        User.find_each do |user|
          user.otp_secret_key = ROTP::Base32.random_base32
          user.save!
        end
      end
    end

6. Generate a migration to remove the :otp_secret_key column:

   rails g migration RemoveOtpSecretKeyFromUsers otp_secret_key:string
   

7. Run the migrations: bundle exec rake db:migrate

If, for some reason, you want to switch back to the old non-encrypted version, use these steps:

1. Remove (encrypted: true) from has_one_time_password

2. Roll back the last 3 migrations (assuming you haven't added any new ones after them):

   bundle exec rake db:rollback STEP=3
   

Example App

TwoFactorAuthenticationExample