Module: Lockbox::Model

Defined in:
lib/lockbox/model.rb

Defined Under Namespace

Modules: Attached

Instance Method Summary collapse

Instance Method Details

#encrypts(*attributes, **options) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/lockbox/model.rb', line 3

def encrypts(*attributes, **options)
  # support objects
  # case options[:type]
  # when Date
  #   options[:type] = :date
  # when Time
  #   options[:type] = :datetime
  # when JSON
  #   options[:type] = :json
  # when Hash
  #   options[:type] = :hash
  # when Array
  #   options[:type] = :array
  # when String
  #   options[:type] = :string
  # when Integer
  #   options[:type] = :integer
  # when Float
  #   options[:type] = :float
  # end

  custom_type = options[:type].respond_to?(:serialize) && options[:type].respond_to?(:deserialize)
  raise ArgumentError, "Unknown type: #{options[:type]}" unless custom_type || [nil, :string, :boolean, :date, :datetime, :time, :integer, :float, :binary, :json, :hash, :array].include?(options[:type])

  activerecord = defined?(ActiveRecord::Base) && self < ActiveRecord::Base
  raise ArgumentError, "Type not supported yet with Mongoid" if options[:type] && !activerecord

  attributes.each do |name|
    # add default options
    encrypted_attribute = "#{name}_ciphertext"

    options = options.dup

    # migrating
    original_name = name.to_sym
    name = "migrated_#{name}" if options[:migrating]

    name = name.to_sym

    options[:attribute] = name.to_s
    options[:encrypted_attribute] = encrypted_attribute
    options[:encode] = true unless options.key?(:encode)

    encrypt_method_name = "generate_#{encrypted_attribute}"
    decrypt_method_name = "decrypt_#{encrypted_attribute}"

    class_eval do
      @lockbox_attributes ||= {}

      if @lockbox_attributes.empty?
        def self.lockbox_attributes
          parent_attributes =
            if superclass.respond_to?(:lockbox_attributes)
              superclass.lockbox_attributes
            else
              {}
            end

          parent_attributes.merge(@lockbox_attributes || {})
        end

        # use same approach as activerecord serialization
        def serializable_hash(options = nil)
          options = options.try(:dup) || {}

          options[:except] = Array(options[:except])
          options[:except] += self.class.lockbox_attributes.flat_map { |_, v| [v[:attribute], v[:encrypted_attribute]] }

          super(options)
        end

        # use same approach as devise
        def inspect
          inspection =
            serializable_hash.map do |k,v|
              "#{k}: #{respond_to?(:attribute_for_inspect) ? attribute_for_inspect(k) : v.inspect}"
            end
          "#<#{self.class} #{inspection.join(", ")}>"
        end

        if activerecord
          # TODO wrap in module?
          def attributes
            # load attributes
            # essentially a no-op if already loaded
            # an exception is thrown if decryption fails
            self.class.lockbox_attributes.each do |_, lockbox_attribute|
              # it is possible that the encrypted attribute is not loaded, eg.
              # if the record was fetched partially (`User.select(:id).first`).
              # accessing a not loaded attribute raises an `ActiveModel::MissingAttributeError`.
              send(lockbox_attribute[:attribute]) if has_attribute?(lockbox_attribute[:encrypted_attribute])
            end
            super
          end

          # needed for in-place modifications
          # assigned attributes are encrypted on assignment
          # and then again here
          before_save do
            self.class.lockbox_attributes.each do |_, lockbox_attribute|
              attribute = lockbox_attribute[:attribute]

              if attribute_changed_in_place?(attribute)
                send("#{attribute}=", send(attribute))
              end
            end
          end
        else
          def reload
            self.class.lockbox_attributes.each do |_, v|
              instance_variable_set("@#{v[:attribute]}", nil)
            end
            super
          end
        end
      end

      raise "Duplicate encrypted attribute: #{original_name}" if lockbox_attributes[original_name]
      @lockbox_attributes[original_name] = options

      if activerecord
        # preference:
        # 1. type option
        # 2. existing virtual attribute
        # 3. default to string (which can later be overridden)
        if options[:type]
          attribute_type =
            case options[:type]
            when :json, :hash, :array
              :string
            when :integer
              ActiveModel::Type::Integer.new(limit: 8)
            else
              options[:type]
            end

          attribute name, attribute_type

          serialize name, JSON if options[:type] == :json
          serialize name, Hash if options[:type] == :hash
          serialize name, Array if options[:type] == :array
        elsif !attributes_to_define_after_schema_loads.key?(name.to_s)
          # when migrating it's best to specify the type directly
          # however, we can try to use the original type if its already defined
          if attributes_to_define_after_schema_loads.key?(original_name.to_s)
            attribute name, attributes_to_define_after_schema_loads[original_name.to_s].first
          else
            attribute name, :string
          end
        end

        define_method("#{name}_was") do
          send(name) # writes attribute when not already set
          super()
        end

        # restore ciphertext as well
        define_method("restore_#{name}!") do
          super()
          send("restore_#{encrypted_attribute}!")
        end

        if ActiveRecord::VERSION::STRING >= "5.1"
          define_method("#{name}_in_database") do
            send(name) # writes attribute when not already set
            super()
          end
        end
      else
        # keep this module dead simple
        # Mongoid uses changed_attributes to calculate keys to update
        # so we shouldn't mess with it
        m = Module.new do
          define_method("#{name}=") do |val|
            instance_variable_set("@#{name}", val)
          end

          define_method(name) do
            instance_variable_get("@#{name}")
          end
        end

        include m

        alias_method "#{name}_changed?", "#{encrypted_attribute}_changed?"

        define_method "#{name}_was" do
          ciphertext = send("#{encrypted_attribute}_was")
          self.class.send(decrypt_method_name, ciphertext, context: self)
        end

        define_method "#{name}_change" do
          ciphertexts = send("#{encrypted_attribute}_change")
          ciphertexts.map { |v| self.class.send(decrypt_method_name, v, context: self) } if ciphertexts
        end

        define_method "reset_#{name}!" do
          instance_variable_set("@#{name}", nil)
          send("reset_#{encrypted_attribute}!")
          send(name)
        end

        define_method "reset_#{name}_to_default!" do
          instance_variable_set("@#{name}", nil)
          send("reset_#{encrypted_attribute}_to_default!")
          send(name)
        end
      end

      define_method("#{name}?") do
        send("#{encrypted_attribute}?")
      end

      define_method("#{name}=") do |message|
        # decrypt first for dirty tracking
        # don't raise error if can't decrypt previous
        begin
          send(name)
        rescue Lockbox::DecryptionError
          # this is expected for hybrid cryptography
          warn "[lockbox] Decrypting previous value failed" unless options[:algorithm] == "hybrid"
          nil
        end

        send("lockbox_direct_#{name}=", message)

        # warn every time, as this should be addressed
        # maybe throw an error in the future
        if !options[:migrating]
          if activerecord
            if self.class.columns_hash.key?(name.to_s)
              warn "[lockbox] WARNING: Unencrypted column with same name: #{name}. Set `ignored_columns` or remove it to protect the data."
            end
          else
            if self.class.fields.key?(name.to_s)
              warn "[lockbox] WARNING: Unencrypted field with same name: #{name}. Remove it to protect the data."
            end
          end
        end

        super(message)
      end

      # separate method for setting directly
      # used to skip blind indexes for key rotation
      define_method("lockbox_direct_#{name}=") do |message|
        ciphertext = self.class.send(encrypt_method_name, message, context: self)
        send("#{encrypted_attribute}=", ciphertext)
      end
      private :"lockbox_direct_#{name}="

      define_method(name) do
        message = super()

        # possibly keep track of decrypted attributes directly in the future
        # Hash serializer returns {} when nil, Array serializer returns [] when nil
        # check for this explicitly as a layer of safety
        if message.nil? || ((message == {} || message == []) && activerecord && @attributes[name.to_s].value_before_type_cast.nil?)
          ciphertext = send(encrypted_attribute)
          message = self.class.send(decrypt_method_name, ciphertext, context: self)

          if activerecord
            # set previous attribute so changes populate correctly
            # it's fine if this is set on future decryptions (as is the case when message is nil)
            # as only the first value is loaded into changes
            @attributes[name.to_s].instance_variable_set("@value_before_type_cast", message)

            # cache
            # decrypt method does type casting
            if respond_to?(:write_attribute_without_type_cast, true)
              write_attribute_without_type_cast(name.to_s, message) if !@attributes.frozen?
            else
              raw_write_attribute(name, message) if !@attributes.frozen?
            end
          else
            instance_variable_set("@#{name}", message)
          end
        end

        message
      end

      # for fixtures
      define_singleton_method encrypt_method_name do |message, **opts|
        table = activerecord ? table_name : collection_name.to_s

        unless message.nil?
          # TODO use attribute type class in 0.5.0
          case options[:type]
          when :boolean
            message = ActiveRecord::Type::Boolean.new.serialize(message)
            message = nil if message == "" # for Active Record < 5.2
            message = message ? "t" : "f" unless message.nil?
          when :date
            message = ActiveRecord::Type::Date.new.serialize(message)
            # strftime should be more stable than to_s(:db)
            message = message.strftime("%Y-%m-%d") unless message.nil?
          when :datetime
            message = ActiveRecord::Type::DateTime.new.serialize(message)
            message = nil unless message.respond_to?(:iso8601) # for Active Record < 5.2
            message = message.iso8601(9) unless message.nil?
          when :time
            message = ActiveRecord::Type::Time.new.serialize(message)
            message = nil unless message.respond_to?(:strftime)
            message = message.strftime("%H:%M:%S.%N") unless message.nil?
            message
          when :integer
            message = ActiveRecord::Type::Integer.new(limit: 8).serialize(message)
            message = 0 if message.nil?
            # signed 64-bit integer, big endian
            message = [message].pack("q>")
          when :float
            message = ActiveRecord::Type::Float.new.serialize(message)
            # double precision, big endian
            message = [message].pack("G") unless message.nil?
          when :string, :binary
            # do nothing
            # encrypt will convert to binary
          else
            type = (try(:attribute_types) || {})[name.to_s]
            message = type.serialize(message) if type
          end
        end

        if message.nil? || (message == "" && !options[:padding])
          message
        else
          Lockbox::Utils.build_box(opts[:context], options, table, encrypted_attribute).encrypt(message)
        end
      end

      define_singleton_method decrypt_method_name do |ciphertext, **opts|
        message =
          if ciphertext.nil? || (ciphertext == "" && !options[:padding])
            ciphertext
          else
            table = activerecord ? table_name : collection_name.to_s
            Lockbox::Utils.build_box(opts[:context], options, table, encrypted_attribute).decrypt(ciphertext)
          end

        unless message.nil?
          # TODO use attribute type class in 0.5.0
          case options[:type]
          when :boolean
            message = message == "t"
          when :date
            message = ActiveRecord::Type::Date.new.deserialize(message)
          when :datetime
            message = ActiveRecord::Type::DateTime.new.deserialize(message)
          when :time
            message = ActiveRecord::Type::Time.new.deserialize(message)
          when :integer
            message = ActiveRecord::Type::Integer.new(limit: 8).deserialize(message.unpack("q>").first)
          when :float
            message = ActiveRecord::Type::Float.new.deserialize(message.unpack("G").first)
          when :string
            message.force_encoding(Encoding::UTF_8)
          when :binary
            # do nothing
            # decrypt returns binary string
          else
            type = (try(:attribute_types) || {})[name.to_s]
            message = type.deserialize(message) if type
            message.force_encoding(Encoding::UTF_8) if !type || type.is_a?(ActiveModel::Type::String)
          end
        end

        message
      end

      if options[:migrating]
        # TODO reuse module
        m = Module.new do
          define_method "#{original_name}=" do |value|
            result = super(value)
            send("#{name}=", send(original_name))
            result
          end

          unless activerecord
            define_method "reset_#{original_name}!" do
              result = super()
              send("#{name}=", send(original_name))
              result
            end
          end
        end
        prepend m
      end
    end
  end
end