The basis of a secrets editor that works from Rails. I'd probably ditch the file and instead ask for the secret, which I'd store in a cookie with a 10 min ttl (or something)

credentials_controller.rb

class NoPassword::CredentialsController < ApplicationController
  before_action :assign_credentials

  class Editor < Phlex::HTML
    def initialize(credentials:)
      @credentials = credentials
    end

    def template(&)
      style do
        unsafe_raw """
        dd > dl { margin-left: 1rem; }
        body { margin: 1rem; }
        """
      end
      h1 { "Your Secrets" }
      list_credentials @credentials
    end

    private
      def list_credentials(credentials)
        dl do
          credentials.each do |key, value|
            dt { key }
            dd do
              case value
              when Hash
                list_credentials value
              else
                value
              end
            end
          end
        end
      end
  end

  def index
    render Editor.new(credentials: @credentials)
  end

  private
    def config
      Rails.application.config.credentials
    end

    def content_path
      @content_path ||= Rails.root.join("config/credentials.yml.enc")
    end

    def key_path
      @key_path ||= Rails.root.join("config/master.key")
    end

    def assign_credentials
      @credentials = Rails.application.encrypted(content_path, key_path: key_path)
    end
end