Category: Skype

Skype switched to the MSN Messenger Protocol

Noah Petherbridge
Posted by Noah Petherbridge on Tuesday, December 09 2014 @ 10:21:54 AM

Today, Fedora 21 was released and I upgraded to it immediately, and decided not to install Skype this time.

Skype for Linux has been poorly maintained, going years between updates sometimes, and who knows what kind of unknown zero-day vulnerabilities are in there. On my previous installation of Fedora, Skype twice showed a weird issue where it replaced some of its icons with Chinese (or Korean, or something) symbols. I posted about it on Reddit and the Skype forum with no responses, as if I'm the only one who's ever seen this. Was I hacked? Maybe.

I took the latest Windows version of Skype and dumped all its icons trying to find these weird symbols but came up empty-handed. And I don't know of any way to pry icons out of the Linux binary of Skype. So... for now I just don't trust it.

In other news, I decided to Google the Skype protocol, and see what the progress is on people attempting to reverse engineer it, to be able to build an open source third-party Skype client (e.g. to have support in Pidgin). The Wikipedia article said something interesting:

On June 20, 2014, Microsoft announced the deprecation of the old Skype protocol. [...] The new Skype protocol - Microsoft Notification Protocol 24 - promises better offline messaging and better messages synchronization across Skype devices.

I wrote previously that the MSN Messenger service was still alive but it looks like it's the future of Skype as well.

The Microsoft Notification Protocol (MSNP) is the protocol used by MSN Messenger/Windows Live Messenger. I'm reasonably familiar with it from back in the day when I used to work on chatbots that signed in to MSN Messenger to accept their add requests and carry on conversations with humans.

MSNP is a plain text, line-delimited protocol similar to SMTP. There is some outdated documentation up through MSNP10 that we referenced in developing an MSN module in Perl. As an example, this is what you'd see going over the network if somebody sent a chat message to a friend:

MSG 4 N 133
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
X-MMS-IM-Format: FN=Arial; EF=I; CO=0; CS=0; PF=22

Hello! How are you?

The protocol consisted of command lines, typically three letters long (some I remember offhand: NLN--go online, FLN--go offline, BRB--set status to "be right back", RNG--request a conversation with a contact ("ring"), ANS--accept a conversation request ("answer"), and MSG--send a message). The RNG and ANS commands were invisible to the user in the official client, but allowed for some interesting behaviors in our chatbots (like immediately sending you a message the moment you open their chat window, before you even begin to type anything!)

It's interesting that Skype "downgraded" to the MSNP though, given that Skype's old protocol was an impenetrable fortress of obfuscation and encryption that nobody's ever managed to reverse engineer. Even third party clients like Trillian that had Skype support were technically using SkypeKit, a developer tool that allowed Skype to be remote controlled, but which kept all the proprietary bits a secret still. On the other hand, it makes sense for them to make Skype conform to and their other services that used MSNP, rather than upgrade all their other services to use the Skype protocol.

The last version of Windows Live Messenger used MSNP19 (or MSNP21 depending who you ask), so the new Skype protocol is just the next version of MSNP.

In Googling MSNP24 I found this site where efforts are already underway at reverse engineering it. This other site has a lot more details on the current status of the Messenger protocol.

It's only a matter of time now until Pidgin can natively support Skype accounts. It will also be fun to program chatbots for Skype. :)

Skype and Windows Live Messenger

Noah Petherbridge
Posted by Noah Petherbridge on Friday, February 28 2014 @ 04:17:26 AM
Back in the day, I ran a couple of chatbots on Windows Live Messenger (although it was called MSN Messenger then), so I'm reasonably familiar with how the Microsoft Notification Protocol (MSNP) works. We had a Perl module called which works with the MSNP10 version of the protocol, and it probably still works today.

That's right, the Windows Live Messenger protocol is still perfectly alive and well today. A while back, I booted my Windows OS on my PC where I still had Pidgin set up to sign me into MSN, and surprisingly it still worked. One of my Skype contacts sent me a message over Pidgin, and their "MSN e-mail address" had an "@SkypeDomain.fakedomain" domain part. It seems that now, though, while the MSN servers are still up, they at least block non-Chinese users from authenticating (Pidgin says "invalid response from server").

The Skype/MSN merger was done in a pretty half-assed way by Microsoft:

  • If you sign in with your Skype username, you only see Skype contacts.
  • If you sign in with your MSN username, you see both MSN and Skype contacts.
  • Even though you can use your old MSN username, and chat with existing MSN contacts, there doesn't seem to be a way to add a new MSN contact through Skype.
It appears that the Skype client actually acts like a "mini Pidgin": when you sign in with your old MSN account, Skype actually signs you in separately to the Skype and MSN servers. And, on the MSN side of things, the "@SkypeDomain.fakedomain" extension was probably implemented similarly to what happened when MSN and Yahoo joined forces, and your Yahoo contacts on MSN would have "" domain extensions.

I don't get why Microsoft doesn't just pull the plug on MSNP completely, and force everyone to get a Skype name if they don't already have one linked with their MSN accounts.

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