AES256

AES256.rb

require 'base64'
require 'openssl'
require 'singleton'
require 'forwardable'

class AES256
  class Config
    class << self
      attr_accessor :key
    end
  end

  module KeyLength
    SIZE = 32

    class Error < StandardError
      def initialize(str)
        super("key length too short (given: #{str.size}, expected: #{SIZE})")
      end
    end

    def self.validate(str)
      return str if Kind::String[str].size >= SIZE

      raise Error.new(str)
    end
  end

  module Cipher
    def self.new
      OpenSSL::Cipher::AES256.new(:CBC)
    end

    def self.random_key
      new.random_key
    end
  end

  def self.from_password(arg)
    new(OpenSSL::Digest::SHA256.new.digest(arg))
  end

  attr_reader :cipher

  def initialize(arg = nil)
    @key = KeyLength.validate(arg || Config.key)

    @cipher = Cipher.new
  end

  def encrypt(str)
    call(@cipher.encrypt, str)
  end

  def encrypt_base64(str)
    Base64.encode64(encrypt(str))
  end

  def decrypt(str)
    call(@cipher.decrypt, str)
  end

  def decrypt_base64(str)
    decrypt(Base64.decode64(str))
  end

  def inspect
    "#<AES256 @key=\"#{@key[0..2]}#{'.' * 24}#{@key[-3..-1]}\">"
  end

  private

    def call(cipher, str)
      cipher.key = @key
      cipher.update(str) + cipher.final
    end
end