Jabbering with Google Talk over XMPP

I am writing an XMPP client that can talk to Google and maybe implement some cool things on top of it. So this weekend I began exploring the specs and intend to maintain an account of how it is going. XMPP is a widely discussed/implemented topic and has many many clients - so it is no research topic. Why did I choose to do this? Just for fun to try something new (for me) out. I know I can get the XMPP library from Jive Software but thats no fun. Sometimes re-inventing the wheel has its own pleasures :-).

The XMPP specs are an open standard on which Jabber and Google Talk are based. There are a number of extensions which are under consideration and most of the cool things have already been thought of such as RPC over XMPP.

So far as a prototype, I have managed to get connected to talk.google.com, perform starttls and authenticate myself followed by resource binding and initiating a session. Now, my prototype code is hitting its limitations and I will have to spend some time fixing it to be able to do some serious talking with XMPP. I have also managed to get my account successfuly blocked for authenticating incorrectly as well - but got out of that mess. :-)

I was hoping to sniff out the conversation that the Google Talk client is having with the server using Ethereal as per this blog that describes X-GOOGLE-TOKEN, a Google mechanism for Single Sign-on. As per that blog, the Google Chat client does not do starttls but does an XMPP authentication over an un-secure socket using a Google generated token (the actual authentication with the Google token server is over https) so all the communication can be sniffed. However, my client seems to be doing a starttls and I can't sniff any details out after the proceed response. Too bad - appears that Google Talk has changed since the blog was written.

Here's the sequence of communication with the Google Talk server - (formatted for readability with text sent from me in this colour and the response in this colour and comments in this colour).

<stream:stream
          to='gmail.com'
          xmlns='jabber:client'
          xmlns:stream='http://etherx.jabber.org/streams'
          version='1.0'>
<?xml version="1.0" encoding="UTF-8"?>
<stream:stream from="gmail.com" id="X0B367FC8A9597BA4" version="1.0" xmlns:stream="http://etherx.jabber.org/streams" xmlns="jabber:client">
 <stream:features>
                <starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls"/>
                <mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl">
                        <mechanism>X-GOOGLE-TOKEN</mechanism>
                </mechanisms>
 </stream:features>

<starttls xmlns="urn:ietf:params:xml:ns:xmpp-tls" /> <--- Start TLS - basically the rest of the communication is over SSL
<proceed xmlns="urn:ietf:params:xml:ns:xmpp-tls"/>

TLS Succeeded - we are good to go...

<stream:stream
          to='gmail.com'
          xmlns='jabber:client'
          xmlns:stream='http://etherx.jabber.org/streams'
          version='1.0'>
<?xml version="1.0" encoding="UTF-8"?>
<stream:stream from="gmail.com" id="X1A565C1E8E3FD7CA" version="1.0" xmlns:stream="http://etherx.jabber.org/streams" xmlns="jabber:client">
 <stream:features>
  <mechanisms xmlns="urn:ietf:params:xml:ns:xmpp-sasl">
   <mechanism>PLAIN</mechanism>\
   <mechanism>X-GOOGLE-TOKEN</mechanism>
  </mechanisms>
 </stream:features>

Now we get the PLAIN auth mechanism which is basically base64 encoded \u0000username\u0000password string which I have blacked out here.
<auth xmlns='urn:ietf:params:xml:ns:xmpp-sasl' mechanism='PLAIN'>XXXXXXXXXXXXXXXXXX</auth>
<success xmlns="urn:ietf:params:xml:ns:xmpp-sasl"/> <--- authenticated

<stream:stream
          to='gmail.com'
          xmlns='jabber:client'
          xmlns:stream='http://etherx.jabber.org/streams'
          version='1.0'>
<?xml version="1.0" encoding="UTF-8"?>
<stream:stream from="gmail.com" id="X77D6827CD0B365BA" version="1.0" xmlns:stream="http://etherx.jabber.org/streams" xmlns="jabber:client">
 <stream:features>
  <bind xmlns="urn:ietf:params:xml:ns:xmpp-bind"/><session xmlns="urn:ietf:params:xml:ns:xmpp-session"/>
 </stream:features>

<iq type='set' id='bind_1'>
 <bind xmlns='urn:ietf:params:xml:ns:xmpp-bind'/>
</iq>
<iq id="bind_1" type="result">
 <bind xmlns="urn:ietf:params:xml:ns:xmpp-bind">
  <jid>XXXXXXXX@gmail.com/D922F673</jid>
 </bind>
</iq>


<iq to='gmail.com' type='set' id='sess_1'><session xmlns='urn:ietf:params:xml:ns:xmpp-session'/></iq>
<iq from="gmail.com" type="result" id="sess_1"/>

Authenticated, Resource bound and Session created. Now, I need to send a message!

</stream:stream>

Next article on this, I hope to have successfully sent a message.