ROTP and Google Authenticator Example

example run

# install dependency
pabs@meh:~/git/test/rotp> sudo gem install rotp

# generate new secret and QR code URL
pabs@meh:~/git/test/rotp> ruby ./rotp-example.rb new asdf@example.com
QR Code URL: https://chart.googleapis.com/chart?chs=200x200&chld=M|0&cht=qr&chl=otpauth%3A%2F%2Ftotp%2FAlonzo%27s%2520Totally%2520Secure%2520App%3Aasdf%40example.com%3Fsecret%3Dr7eslax2okb2dkr4%26issuer%3DAlonzo%2527s%2BTotally%2BSecure%2BApp
Secret: r7eslax2okb2dkr4
Provisioning URL: otpauth://totp/Alonzo's%20Totally%20Secure%20App:asdf@example.com?secret=r7eslax2okb2dkr4&issuer=Alonzo%27s+Totally+Secure+App

# at this point i used the QR Code URL above to configure Google Authenticator on my phone
# if this was a real application, it would store the secret along with the email in a database here
# then the "510461" code below came from my phone

# test with correct code
pabs@meh:~/git/test/rotp> ruby ./rotp-example.rb test r7eslax2okb2dkr4 510461
Result: success

# test with incorrect code
pabs@meh:~/git/test/rotp> ruby ./rotp-example.rb test r7eslax2okb2dkr4 123356
Result: failure

rotp-example.rb

#!/usr/bin/env ruby

require 'rotp'
require 'erb'
# require 'optparse'

module ROTPExample
  APP_NAME = "Alonzo's Totally Secure App"

  TEMPLATES = {
    qr: %{
      https://chart.googleapis.com/chart?chs=200x200&chld=M|0&cht=qr&chl=%s
    }.strip,

    new: %{
QR Code URL: %s
Secret: %s
Provisioning URL: %s
    }.strip,

    usage: %{
Usage: %s [ new EMAIL | test SECRET CODE ]

Examples:

    # create new shared secret for hello@example.com
    %s new hello@example.com

    # test code
    %s test 
    }.strip,
  }

  class QRCode
    def initialize(data) 
      @data = data
    end

    def to_s
      TEMPLATES[:qr] % [ERB::Util.url_encode(@data)]
    end
  end

  class Generator
    def initialize(secret, email, app_name = APP_NAME)
      @secret, @email, @app_name = secret, email, app_name
      # generate provisioning uri
      @uri = ROTP::TOTP.new(@secret, issuer: @app_name).provisioning_uri(@email)
    end

    def to_s
      TEMPLATES[:new] % [QRCode.new(@uri), @secret, @uri]
    end
  end

  def self.print_usage(app)
    $stderr.puts TEMPLATES[:usage] % ([app]  * 3)
    exit -1
  end

  def self.run(app, args)
    print_usage(app) unless args.length > 1

    case args.shift
    when 'new'
      # get email from args
      email = args.shift

      # generate shared secret
      secret = ROTP::Base32.random_base32

      # generate and print result
      puts Generator.new(secret, email)
    when 'test'
      print_usage unless args.length == 2
      secret, code = args

      # verify code with 120 seconds of drift
      ok = ROTP::TOTP.new(secret).verify_with_drift(code, 60, Time.now - 30)

      # print result
      puts 'Result: %s' % [ok ? 'success' : 'failure']
    else
      print_usage(app)
    end
  end
end

# run app
ROTPExample.run($0, ARGV) if __FILE__ == $0