ftp-manager/app/services/crypt_serializer.rb

# frozen_string_literal: true
require 'openssl'
require 'base64'

class CryptSerializer
  attr_reader :cipher

  class << self
    # pulling from DB - return plain value
    def load value
      new.decrypt value
    end

    # saving to DB - return encrypted value
    def dump value
      new.encrypt value
    end
  end

  def initialize
    @cipher = OpenSSL::Cipher::AES.new(256, :CBC)
  end

  def encrypt(value)
    return value if value.nil?
    unless value.is_a?(String)
      raise "Attribute was supposed to be a `String`, but was instead a `#{value.class}`"
    end

    build_cipher value
  end

  def decrypt(value)
    return value if value.nil?

    parts = Marshal.load Base64.urlsafe_decode64(value)
    decode_cipher parts
  end

  private

    def build_cipher value
      cipher.encrypt
      parts = [cipher.random_key, cipher.random_iv, cipher.update(value) + cipher.final]
      Base64.urlsafe_encode64 Marshal.dump(parts)
    end

    def decode_cipher parts
      cipher.decrypt
      cipher.key = parts[0]
      cipher.iv = parts[1]
      cipher.update(parts[2]) + cipher.final
    end
end