talka.rb

require 'rubygems'
require 'eventmachine'
require 'digest/md5'
require 'base64'
require 'socket'

# Dunno, may need this later on.
class Session < Struct.new(:username, :id)
  
end

SESSIONS = {}

module Jabber
  
  def domain_name
    "example.com"
  end
  
  def time_hash
    Digest::MD5.hexdigest(Time.now.to_f.to_s)
  end
  
  def determine_ip
    @port, @ip = Socket.unpack_sockaddr_in(get_peername)
  end
  
  def receive_data(data)
    determine_ip
    # Client is connecting.
    if stream = /<stream:stream.*to='(.*?)'/.match(data)
      send_data("<stream:stream xmlns:stream='http://etherx.jabber.org/streams' xmlns='jabber:client' from='#{stream[1]}' xml:lang='en' version='1.0'>")
      # They are trying to log in, send them features.
      if !(session = SESSIONS[@ip])
        send_data("<stream:features><mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'><mechanism>DIGEST-MD5</mechanism><mechanism>PLAIN</mechanism></mechanisms></stream:features>")
      # They have logged in, and now are starting a new stream. Welcome them.
      else
        puts "Welcome aboard, captain."
        send_data("<stream:stream xmlns='jabber:client' xmlns:stream='http://etherx.jabber.org/streams' id='#{session.username}_#{time_hash}' from='example.com' version='1.0'><stream:features><bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/><session xmlns='urn:ietf:params:xml:ns:xmpp-session'/></stream:features>")
      end
      
      
      # Client is trying to auth...
    elsif auth = /^<auth(.*?)mechanism='(.*?)'(.*?)\/>/.match(data)
      if auth[2] == "DIGEST-MD5"
        @server_nonce = time_hash
        encodee = "realm=\"talka\",nonce=\"#{@nonce}\",qop=\"auth\",charset=utf-8,algorithm=md5-sess\n"
        encoded = Base64.encode64(encodee)
        # Challenge the client to auth correctly.
        send_data("<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
        #{encoded}
        </challenge>")
      else
        puts "UNKNOW AUTH PROTOCOL SENT"
      end
      
    # Client sends back response from our auth challenge
    elsif response = /^<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>(.*?)<\/response>$/.match(data)
      decoded = Base64.decode64(response[1])
      
      # Gather valuable resources...
      username = /username="(.*?)"/.match(decoded)[1]
      nonce = /nonce="(.*?)"/.match(decoded)[1]
      
      if nonce = @server_nonce
        puts "LOGGING IN!"
        SESSIONS[@ip] = Session.new(username, nonce)
        # Client responds to challenge and then server tells client they are successfully authenticated.
        # Even though this isn't a real server we still have to go through the motions.
        encoded = "rspauth=#{time_hash}"
        send_data("<challenge xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>#{encoded}</challenge>")
      else
        # I don't know how this would happen, but better to assume it can rather than it can not.
        puts "BAD NONCE"
        # Bad nonce
        send_data("<failure xmlns='urn:ietf:params:xml:ns:xmpp-sasl'><temporary-auth-failure/></failure></stream:stream>")
      end
    
    # Responding to the next challenge.
    elsif response = /<response xmlns='urn:ietf:params:xml:ns:xmpp-sasl'\/>/.match(data)
      # Welcome aboard, you are now logged in.
      send_data("<success xmlns='urn:ietf:params:xml:ns:xmpp-sasl'/>")
      
    # Client asks if it can auth, of course you can!
    elsif iq = /<iq type='set' id='(\d+)'><query xmlns='jabber:iq:auth'><username>(.*?)<\/username><digest>(.*?)<\/digest><\/query><\/iq>/.match(data)
      send_data("<iq type='result' id='#{iq[1]}'><query xmlns='jabber:iq:auth'><username>#{iq[2]}<\/username><digest>#{iq[3]}<\/digest><\/query></iq>")
    
    # Client asks if it can bind resources, of course you can!
    elsif iq = /<iq type='set' id='(\d+)'><bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'\/><\/iq>/.match(data)
      SESSIONS[ip].id = time_hash[0..7].upcase
      session = SESSIONS[ip]
      send_data("<iq type='result' id='#{iq[1]}'><bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'><jid>#{session.username}@#{name}/#{session.id}</jid></bind></iq>")
    
    # Client asks if it can have a session, of course you can!
    elsif iq = /<iq type='set' id='(\d+)'><session xmlns='urn:ietf:params:xml:ns:xmpp-session'\/><\/iq>/.match(data)
      send_data("<iq type='result' id='#{iq[1]}' />")
      
    # Client asks if there's anybody out there...
    elsif presence = /^<presence\/>$/.match(data)
      session = SESSIONS[ip]
      # Since this is not a real server, we'll lie and say there's some people.
      send_data("<presence from='alice@#{domain}.111A111' to='#{session.username}@#{domain}/#{session.id}'><priority>1</priority></presence>")
      send_data("<presence from='bobby@#{domain}.222A222' to='#{session.username}@#{domain}/#{session.id}'><priority>1</priority></presence>")

    else 
      puts "UNKNOWN: #{data}"
    end


  end
  
end

EM.run {
  EM.start_server "0.0.0.0", 5222, Jabber
}