authenticated?

# File actionmailbox/app/controllers/action_mailbox/ingresses/mandrill/inbound_emails_controller.rb, line 46
      def authenticated?
        if key.present?
          Authenticator.new(request, key).authenticated?
        else
          raise ArgumentError, <<~MESSAGE.squish
            Missing required Mandrill API key. Set action_mailbox.mandrill_api_key in your application's
            encrypted credentials or provide the MANDRILL_INGRESS_API_KEY environment variable.
          MESSAGE
        end
      end

      def key
        Rails.application.credentials.dig(:action_mailbox, :mandrill_api_key) || ENV["MANDRILL_INGRESS_API_KEY"]
      end

      class Authenticator
        attr_reader :request, :key

        def initialize(request, key)
          @request, @key = request, key
        end

        def authenticated?
          ActiveSupport::SecurityUtils.secure_compare given_signature, expected_signature
        end

        private
          def given_signature
            request.headers["X-Mandrill-Signature"]
          end

          def expected_signature
            Base64.strict_encode64 OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, key, message)
          end

          def message
            request.url + request.POST.sort.flatten.join
          end
      end
  end
end