Ruby D-Bus -> ffwd

Ruby D-Bus provides an implementation of the D-Bus protocol such that the D-Bus system can be used in the Ruby programming language.

You can switch between REXML and Hpricot as XML parsers!

Still a little bumpy with multiple threads, but getting there.

This is my personal dev-fork of mvidners upstream.

If you’d like to contrib to this fork, let me know.

Most of my work here is actually for another project: github.com/pangdudu/robots/tree/master

Peace.

Requirements

* Ruby 1.8 (>= 1.8.6?)

Installation

sudo gem install pangdudu-ruby-dbus --source=http://gems.github.com

Features

Ruby D-Bus currently supports the following features:

* Connecting to local buses.
* Accessing remote services, objects and interfaces.
* Invoking methods on remote objects synchronously and asynchronously.
* Catch signals on remote objects and handle them via callbacks.
* Remote object introspection.
* Walking object trees.
* Creating services and registering them on the bus.
* Exporting objects with interfaces on a bus for remote use.
* Rubyish D-Bus object and interface syntax support that automatically
  allows for introspection.
* Emitting signals on exported objects.

* Connection to a local or remote bus over TCP/IP using 'Dbus::RemoteBus.new(socket_name)'
* Authentification mechanisms working now: External,CookieSHA1

Usage

Basics:

View a tutorial online on trac.luon.net/data/ruby-dbus/tutorial/.

TCP/Remote stuff:

Take a look at ‘config/remote.session.dbus.conf’ and start ‘config/start_dbus_session.sh’.

You can now try and run one of the tests e.g. ‘test/simple_socket_test.rb’.

Problems you’ll have with ‘CookieSHA1’ when using it remotely:

Unless we [including you :)] write a funkier SASL authentification mechanism that makes sense when using it over-wire, we’re stuck with the cookie auth.

Works like this:

There is a file in ‘~/.dbus-keyrings’ named ‘org_freedesktop_general’. It is ‘-rw——-’ so that only you can read it (if you change the permissions, dbus-daemon will most likely ignore the file leaving you with ‘External’, which is even worse remotely). It’s kind of a secret key you use to auth against yourself later on.

If you take a look at ‘dbus/auth.rb line 40+’ you’ll see the problem:

# Search cookie file for id
path = File.join(ENV['HOME'], '.dbus-keyrings', context)

So if you’re starting ‘config/start_dbus_session.sh’ on one host and ‘config/start_dbus_session.sh’ on another one, you’ll need to make sure that the content in ‘~/.dbus-keyrings/org_freedesktop_general’ is the same on both machines, in order for the ‘CookieSHA1’ auth to work.

Not cool. I can think of hacks with nfs,smb or fuse:sshfs making it less painful to use.

The file content also get’s updated every 5 minutes (when a client fails to auth etc.). Making copy and paste from one shell to another very frolic.

Hackish solution from pangdudu/robots/lib/robots_agent.rb

#because dbus remote auth still betrays us, we need to hack it
def get_remote_cookie
  if @config[:robots_socket_name].include? "tcp:"
    af, port, daemon_name, daemon_addr = (Socket::getaddrinfo(@config[:daemonhost],@config[:daemonhost].to_i)).first
    ilog "Trying to get/hack remote cookie from: #{daemon_name}."
    begin
      cookiepath = "#{ENV['HOME']}/.dbus-keyrings/org_freedesktop_general"
      #oki, the scp magic only works, if you use sshkeys
      `scp #{daemon_addr}:.dbus-keyrings/org_freedesktop_general #{cookiepath}`
      if File.exist? cookiepath
        cookie = File.open(cookiepath) 
        dlog "Got cookie: #{cookie.gets}"
      end
    rescue
      elog "Oops, something is wrong."
    end
  else
    dlog "Nothing to hack, boring."
  end
end

in principle, this is ok. we can now do what we want and it is save to exchange cookies over a ssh session. However I’m still not feeling comfortable doing this. I guess everything else would mean touching the reference C dbus-daemon implementation.

more infos:

http://dbus.freedesktop.org/doc/dbus-specification.html#auth-mechanisms
http://lists.freedesktop.org/archives/dbus/2007-June/008067.html

Booyaa.

License

Ruby D-Bus is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.