menush.rb

#!/usr/bin/env ruby

require 'etc'
require 'yaml'
require 'syslog'
require 'rubygems'
require 'highline'

# Path to shared 'default' menu definition file
DEFAULT_MENU_PATH = '/etc/menush/__default__'
# Directory containing per-user config files
USER_MENU_DIR = '/etc/menush'
# Logfile path
LOG_PATH = '/var/log/menush.log'

exit_status = 0

def die(msg, code=1)
  STDERR.puts(msg)
  Syslog.err(msg)
  exit_status = code
  throw :exit
end

def clear
  puts "\033[2J"
  puts "\033[0;0H"
end

# We keep looping until the user asks to exit
catch(:exit) do
  # Set up syslog-based audit log 
  Syslog.open('menush', Syslog::LOG_PID|Syslog::LOG_CONS, Syslog::LOG_AUTHPRIV)

  current_user = Etc.getlogin
  full_config_path = File.join(USER_MENU_DIR, current_user)

  # We use the default config file if none exists for the current user
  menu_path = File.exists?(full_config_path) ? full_config_path : DEFAULT_MENU_PATH

  die('No menu definition found!') unless File.readable?(menu_path)
  Syslog.info("Loading menu shell definition for user #{current_user} from #{menu_path}")

  menu_def = open(menu_path) {|fh| YAML.load(fh) }

  # Verify the menu file format *first*
  menu_def.each do |params|
    path = params['path']
    die('Bad command menu format') if (path.nil? or params['prompt'].nil?)
    die("Invalid command: #{path}") unless File.executable?(path)
  end

  begin
    while true
      clear
      cli = HighLine.new
      selected = nil

      puts "Please choose a command:\n\n"

      cli.choose do |menu|
        menu.prompt = "\n[1-#{menu_def.size + 1}]: "
        menu_def.each_with_index do |params, index|
          prompt = params['prompt']
          menu.choice(prompt) { selected = index }
        end
        menu.choice('Exit')
      end

      die('Exiting.') if selected.nil?

      cmd_params = menu_def[selected]

      # TODO: smart escaping of arguments. For now, we just disallow any input 
      # which contains shell special characters
      cmd_args = ''
      if cmd_params['allow_args']
        safe_char_pat = %r|^[-.+=_/,a-zA-Z0-9 ]+$|
        cmd_args = cli.ask("Command arguments: ") {|q| q.validate = safe_char_pat }
      end

      cmd_string = "#{cmd_params['path']} #{cmd_params['defaults']} #{cmd_args}".strip
      Syslog.info("About to run command for #{current_user}: #{cmd_string.inspect}")

      clear
      puts "Running '#{cmd_string}'...\n\n"
      status = system(cmd_string)
      if $? != 0
        Syslog.info("Command exited with non-zero status (#{$?})")
      end
      puts "\n\nPress Return/Enter key to continue..."
      STDIN.gets
    end
  rescue Interrupt, EOFError
    die('Exiting.')
  end # while true
end # catch(:exit)

# If we get here, the user chose to exit, so clean up and shut down
Syslog.close
exit exit_status