RailsMFA

A pluggable, provider-agnostic multi-factor authentication (MFA/2FA) gem for Ruby on Rails applications. RailsMFA makes it simple to add secure authentication via SMS, email, or authenticator apps (TOTP) to any Rails application, regardless of your authentication system.

Features

  • Multiple Authentication Methods: Support for SMS, email, and TOTP-based authenticator apps (like Google Authenticator, Authy, 1Password, Microsoft Authenticator)
  • Fully Provider Agnostic: Works with ANY SMS provider (Twilio, AWS SNS, Vonage, MessageBird, etc.) and ANY authentication system (Devise, Authlogic, Clearance, or custom)
  • Pluggable Delivery: Easy-to-customize SMS and email delivery adapters - bring your own service
  • Secure by Default: Uses timing-safe comparison and one-time use tokens
  • Flexible Storage: Works with Rails.cache, Redis, or any custom cache store
  • QR Code Generation: Built-in support for generating QR codes for authenticator app setup
  • Rails Generators: Quick setup with rails generate commands
  • Simple Configuration: Minimal setup with sensible defaults

Installation

Add this line to your application’s Gemfile:

gem 'rails_mfa'

And then execute:

bundle install

Or install it yourself as:

gem install rails_mfa

Quick Start

1. Run the installer

rails generate rails_mfa:install

This creates an initializer at config/initializers/rails_mfa.rb with configuration options.

2. Generate the migration

rails generate rails_mfa:migration User

This creates a migration to add MFA columns to your User model (or any model you specify).

3. Run the migration

rails db:migrate

Security Note: The mfa_secret column should be encrypted in production. Use Rails 7’s encrypts feature or attr_encrypted:

class User < ApplicationRecord
  encrypts :mfa_secret
end

4. Include the Model concern in your User model

class User < ApplicationRecord
  include RailsMFA::Model

  # Optional: specify which MFA methods this model supports
  enable_mfa_for :sms, :email, :totp
end

5. Configure Your Providers

Edit config/initializers/rails_mfa.rb and configure your preferred SMS and email providers:

RailsMFA.configure do |config|
  # Use ANY SMS provider - Twilio, AWS SNS, Vonage, MessageBird, etc.
  # Just provide a lambda that sends the SMS
  config.sms_provider = lambda do |phone_number, message|
    # Your SMS provider implementation here
    # Example: YourSmsService.send(phone_number, message)
  end

  # Use ANY email provider - ActionMailer, SendGrid, Postmark, etc.
  # Just provide a lambda that sends the email
  config.email_provider = lambda do |email, subject, body|
    # Your email provider implementation here
    # Example: YourMailer.send_code(email, subject, body).deliver_now
  end

  # Optional: customize token settings
  config.code_length = 6              # Default: 6 digits
  config.code_expiry_seconds = 300    # Default: 5 minutes

  # Optional: use custom cache store (Redis, Memcached, etc.)
  # config.token_store = Redis.new
end

Usage

Email-based MFA

# Send a verification code
user = User.find(params[:id])
code = user.send_numeric_code(via: :email)

# Verify the code
if user.verify_numeric_code(params[:code])
  # Code is valid and user is authenticated
  session[:mfa_verified] = true
  redirect_to dashboard_path
else
  # Code is invalid
  flash[:error] = "Invalid verification code"
end

SMS-based MFA

# Send a verification code
code = user.send_numeric_code(via: :sms)

# Verify the code (same as email)
if user.verify_numeric_code(params[:code])
  session[:mfa_verified] = true
  redirect_to dashboard_path
end

Authenticator App (TOTP) - Google Authenticator, Authy, 1Password, Microsoft Authenticator

Authenticator apps provide the most secure MFA method using time-based one-time passwords (TOTP).

Setup Flow

# 1. Generate a secret for the user (do this once during setup)
user.generate_totp_secret!

# 2. Get the provisioning URI for QR code generation
provisioning_uri = user.totp_provisioning_uri(issuer: "MyApp")

# 3. Generate QR code for the user to scan
require 'rqrcode'
qrcode = RQRCode::QRCode.new(provisioning_uri)

# For HTML view:
@qr_svg = qrcode.as_svg(
  module_size: 4,
  standalone: true,
  use_path: true
)

# Or for PNG:
@qr_png = qrcode.as_png(size: 300)

Verification

# Verify the TOTP code from the authenticator app
if user.verify_totp(params[:code])
  user.update(mfa_enabled: true, mfa_method: 'totp')
  session[:mfa_verified] = true
  redirect_to dashboard_path
else
  flash[:error] = "Invalid authenticator code"
  render :verify
end

Example Controller (Complete Setup Flow)

# app/controllers/mfa/authenticator_controller.rb
class Mfa::AuthenticatorController < ApplicationController
  before_action :authenticate_user!

  def new
    # Show setup page
  end

  def create
    # Generate secret and show QR code
    current_user.generate_totp_secret!
    provisioning_uri = current_user.totp_provisioning_uri(issuer: "MyApp")
    @qrcode = RQRCode::QRCode.new(provisioning_uri)
  end

  def verify
    # Verify the code from authenticator app
    if current_user.verify_totp(params[:code])
      current_user.update!(mfa_enabled: true, mfa_method: 'totp')
      flash[:success] = "Authenticator app configured successfully!"
      redirect_to profile_path
    else
      flash[:error] = "Invalid code. Please try again."
      redirect_to mfa_authenticator_path
    end
  end
end

Example View (QR Code Display)

<div class="authenticator-setup">
  <h2>Set Up Authenticator App</h2>

  <p>Scan this QR code with your authenticator app:</p>

  <div class="qr-code">
    &lt;%= @qrcode.as_svg(module_size: 4).html_safe %&gt;
  </div>

  <p>Or enter this secret key manually:</p>
  <code>&lt;%= current_user.mfa_secret %&gt;</code>

  <p>After scanning, enter the 6-digit code from your app to verify:</p>

  &lt;%= form_with url: verify_mfa_authenticator_path, method: :post do |f| %&gt;
    &lt;%= f.text_field :code, placeholder: "000000", maxlength: 6, autofocus: true %&gt;
    &lt;%= f.submit "Verify and Enable" %&gt;
  &lt;% end %&gt;
</div>

Integration Examples

With Devise

# app/controllers/users/mfa_controller.rb
class Users::MfaController &lt; ApplicationController
  before_action :authenticate_user!

  def show
    # Display MFA setup page
  end

  def create
    if current_user.verify_numeric_code(params[:code])
      sign_in current_user, bypass: true
      redirect_to root_path
    else
      flash[:alert] = "Invalid code"
      redirect_to users_mfa_path
    end
  end

  def send_code
    current_user.send_numeric_code(via: params[:method].to_sym)
    flash[:notice] = "Verification code sent"
    redirect_to users_mfa_path
  end
end

Add routes:

# config/routes.rb
devise_for :users
namespace :users do
  resource :mfa, only: [:show, :create] do
    post :send_code
  end
end

With Custom Authentication

# app/controllers/sessions_controller.rb
class SessionsController &lt; ApplicationController
  def create
    user = User.find_by(email: params[:email])

    if user&amp;.authenticate(params[:password])
      if user.mfa_enabled?
        # Store user ID in session temporarily
        session[:pending_mfa_user_id] = user.id
        user.send_numeric_code(via: :sms)
        redirect_to mfa_verification_path
      else
        # No MFA required, log them in
        session[:user_id] = user.id
        redirect_to dashboard_path
      end
    else
      flash[:error] = "Invalid credentials"
      render :new
    end
  end
end

# app/controllers/mfa_verifications_controller.rb
class MfaVerificationsController &lt; ApplicationController
  def show
    # Display MFA verification form
  end

  def create
    user = User.find(session[:pending_mfa_user_id])

    if user.verify_numeric_code(params[:code])
      session.delete(:pending_mfa_user_id)
      session[:user_id] = user.id
      redirect_to dashboard_path
    else
      flash[:error] = "Invalid verification code"
      render :show
    end
  end
end

Provider Configuration Examples

RailsMFA is fully provider-agnostic. You can use any SMS or email service by providing a simple lambda function. Here are examples for popular providers:

SMS Provider Examples

Twilio

# config/initializers/rails_mfa.rb
RailsMFA.configure do |config|
  config.sms_provider = lambda do |to, message|
    require 'twilio-ruby'

    client = Twilio::REST::Client.new(
      ENV['TWILIO_ACCOUNT_SID'],
      ENV['TWILIO_AUTH_TOKEN']
    )

    client.messages.create(
      from: ENV['TWILIO_PHONE_NUMBER'],
      to: to,
      body: message
    )
  end
end

AWS SNS

# config/initializers/rails_mfa.rb
RailsMFA.configure do |config|
  config.sms_provider = lambda do |to, message|
    require 'aws-sdk-sns'

    sns = Aws::SNS::Client.new(
      region: ENV['AWS_REGION'],
      access_key_id: ENV['AWS_ACCESS_KEY_ID'],
      secret_access_key: ENV['AWS_SECRET_ACCESS_KEY']
    )

    sns.publish(
      phone_number: to,
      message: message
    )
  end
end

Vonage (Nexmo)

RailsMFA.configure do |config|
  config.sms_provider = lambda do |to, message|
    require 'vonage'

    client = Vonage::Client.new(
      api_key: ENV['VONAGE_API_KEY'],
      api_secret: ENV['VONAGE_API_SECRET']
    )

    client.sms.send(
      from: ENV['VONAGE_PHONE_NUMBER'],
      to: to,
      text: message
    )
  end
end

MessageBird

RailsMFA.configure do |config|
  config.sms_provider = lambda do |to, message|
    require 'messagebird'

    client = MessageBird::Client.new(ENV['MESSAGEBIRD_API_KEY'])

    client.message_create(
      ENV['MESSAGEBIRD_PHONE_NUMBER'],
      to,
      message
    )
  end
end

Plivo

RailsMFA.configure do |config|
  config.sms_provider = lambda do |to, message|
    require 'plivo'

    client = Plivo::RestClient.new(
      ENV['PLIVO_AUTH_ID'],
      ENV['PLIVO_AUTH_TOKEN']
    )

    client.messages.create(
      src: ENV['PLIVO_PHONE_NUMBER'],
      dst: to,
      text: message
    )
  end
end

Email Provider Examples

SendGrid

# config/initializers/rails_mfa.rb
RailsMFA.configure do |config|
  config.email_provider = lambda do |to, subject, body|
    require 'sendgrid-ruby'
    include SendGrid

    from = Email.new(email: 'noreply@example.com')
    to = Email.new(email: to)
    content = Content.new(type: 'text/plain', value: body)
    mail = Mail.new(from, subject, to, content)

    sg = SendGrid::API.new(api_key: ENV['SENDGRID_API_KEY'])
    sg.client.mail._('send').post(request_body: mail.to_json)
  end
end

Custom ActionMailer Example

# app/mailers/mfa_mailer.rb
class MfaMailer &lt; ApplicationMailer
  def send_code(to, subject, body)
    @code = body
    mail(to: to, subject: subject)
  end
end

# config/initializers/rails_mfa.rb
RailsMFA.configure do |config|
  config.email_provider = lambda do |to, subject, body|
    MfaMailer.send_code(to, subject, body).deliver_now
  end
end

Configuration Options

RailsMFA.configure do |config|
  # SMS provider (required for SMS-based MFA)
  # Lambda that takes (phone_number, message) as arguments
  config.sms_provider = -&gt;(to, message) { ... }

  # Email provider (required for email-based MFA)
  # Lambda that takes (email, subject, body) as arguments
  config.email_provider = -&gt;(to, subject, body) { ... }

  # Length of numeric codes (default: 6)
  config.code_length = 6

  # Code expiration time in seconds (default: 300 = 5 minutes)
  config.code_expiry_seconds = 300

  # Token storage backend (default: Rails.cache or SimpleStore)
  config.token_store = Redis.new
end

Testing

RailsMFA uses RSpec for testing. To run the test suite:

bundle exec rspec

Testing in Your Application

You can stub the providers in your tests:

RSpec.describe "MFA", type: :request do
  before do
    RailsMFA.configure do |config|
      config.sms_provider = -&gt;(to, message) { "SMS sent" }
      config.email_provider = -&gt;(to, subject, body) { "Email sent" }
    end
  end

  it "sends verification code" do
    user = create(:user)
    post send_code_path, params: { method: 'sms' }

    expect(response).to have_http_status(:success)
  end
end

Security Considerations

  1. Encrypt MFA Secrets: Always encrypt the mfa_secret column in your database using Rails’ built-in encryption or a gem like attr_encrypted.

  2. HTTPS Only: Always use HTTPS in production to prevent code interception.

  3. Rate Limiting: Implement rate limiting on MFA endpoints to prevent brute-force attacks:

# Use rack-attack or similar
throttle('mfa/verify', limit: 5, period: 5.minutes) do |req|
  req.ip if req.path == '/mfa/verify' &amp;&amp; req.post?
end

  1. Secure Storage: Use secure session storage (encrypted cookies or server-side sessions).

  2. Backup Codes: Consider implementing backup codes for account recovery.

Advanced Usage

Using with Redis

# config/initializers/rails_mfa.rb
RailsMFA.configure do |config|
  config.token_store = Redis.new(
    host: ENV['REDIS_HOST'],
    port: ENV['REDIS_PORT'],
    db: 1
  )
end

Custom Token Length and Expiration

# Generate an 8-digit code that expires in 10 minutes
user.send_numeric_code(via: :email)

# Configure globally
RailsMFA.configure do |config|
  config.code_length = 8
  config.code_expiry_seconds = 600
end

Checking TOTP Status

# Check if user has TOTP set up
if user.mfa_secret.present? &amp;&amp; user.mfa_enabled?
  # User has TOTP configured
end

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/shoaibmalik786/rails_mfa.

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

License

The gem is available as open source under the terms of the MIT License.

Credits

Created by Shoaib Malik

Support

If you have any questions or need help integrating RailsMFA, please open an issue on GitHub.