Add JWT tokens to session cookie

add_jwt_to_session_cookie.rb

# Modification of https://gist.github.com/pdfrod/9c3b6b6f9aa1dc4726a5

require 'rubygems'
require 'cgi'
require 'active_support'

def add_jwt_stuff_to_session_cookie(cookie, key)
  cookie = CGI::unescape(cookie)

  # Default values for Rails 4 apps
  key_iter_num = 1000
  key_size     = 64
  salt         = "encrypted cookie"
  signed_salt  = "signed encrypted cookie"

  key_generator = ActiveSupport::KeyGenerator.new(key, iterations: key_iter_num)
  secret = key_generator.generate_key(salt)
  sign_secret = key_generator.generate_key(signed_salt)

  encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
  decrypted_cookie = encryptor.decrypt_and_verify(cookie)

  new_cookie = '{"expires_at":0,"access_token":"blah","refresh_token":"blah",' + decrypted_cookie[1..-1]
  puts CGI::escape(encryptor.encrypt_and_sign(new_cookie))
end

# Paste your stuff here
cookie = 'Your "_session_id" cookie'
key = 'SECRET_KEY_BASE for the review app'

add_jwt_stuff_to_session_cookie(cookie, key)