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Skype protocol reverse engineered, source available

skype-open-source.blogspot.com

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Re: Skype protocol reverse engineered, source available

#111

Post by skeletonjelly »

VMG wrote: post #78
jcr wrote: post #70

Earlier quoted context omitted.

I think you actually want two answers, the question you asked and "why report it?" The IDA Pro disassembler and the Hex-Rays decompiler are not only very expensive tools, but they are very difficult to purchase. Due to constant problems with piracy, these days they will only sell their products to three areas; (1) governments/law enforcement, (2) very well established corporations (typically well known security resea…

Thanks for your insight. The spelling errors in the blog posts aren't the hallmark of professionalism either, but what about the information in comment header? /*\ |*| |*| Skype 4142 Decompression v1.002 by Sean O'Neil. |*| Copyright (c) 2004-2009 by VEST Corporation. |*| All rights reserved. Strictly Confidential! |*| |*| Date: 29.10.2009 |*| \*/ is this just a special brand of stupid? edit: some info about this cor…

Don't pick on the spelling. Have you considered users who don't have English as their first language? I hear there a few is all ;)

Re: Skype protocol reverse engineered, source available

#112

Post by yuhong »

jcr wrote: post #44

I wouldn't venture to say this doesn't belong on HN since it really is interesting (if it was actually done correctly), but the files available for download are most likely illegal, were most likely created with pirated tools (IDA Pro/Hex-Rays, and yes, as a customer of theirs for over a dozen years I've reported it), and of course, the usual vilification of reverse engineering. If you're reading this on a desktop or…

>If you're reading this on a desktop or laptop system (rather than a phone), then you are most likely using an "IBM PC Compatible" even if you're using an Intel based Apple, and hence, you're using the fruits of completely legal reverse engineering.

Not if you are booting via EFI, for example if you are booting Mac OS X on an Apple.

Re: Skype protocol reverse engineered, source available

#113

Post by angusgr »

cookiecaper wrote: post #68
angusgr wrote: post #49

Earlier quoted context omitted.

(Follow up: JCR's comment seems to make it clear that's what is being distributed here doesn't constitute reverse engineering in the legal sense. I hadn't actually looked at the files. Ah well.)

And what are jcr's credentials? Not everyone that posts on HN is an expert or should be assumed to understand their subject matter.

No, but he seems factually correct that the files are IDA Pro output from Skype binaries, and a patched/modified version of a Skype binary.

This is as opposed to publishing observations/specifications from looking at such dumps, or from a black-box observation of Skype's behaviour. In this case I believe jcr is 100% correct that what's being distributed isn't protected reverse engineering output, it's a derivative work of the original.

In short: Decompiling or cracking a program and posting it online with notes is not the same as reverse engineering it, although it's a step in that direction.

Re: Skype protocol reverse engineered, source available

#116

Post by jcr »

lesterbuck wrote: post #81
jcr wrote: post #51

Earlier quoted context omitted.

IBM released documentation after the PC had been cloned through "clean room" reverse engineering. http://en.wikipedia.org/wiki/IBM_PC_compatible

Then the cloners moved at warp speed. According to Wikipedia, the PC AT shipped in 1984. For nostalgia, I kept my copy of IBM Personal Computer Hardware Reference Library Technical Reference, Pub #1502494. "This manual describes the various units of the IBM Personal Computer AT and how they interact. It also has information about the basic input/output system (BIOS) and about programming support. The information in t…

The first IBM PC was publicly released for sale on August 12, 1981.

The first "100% Compatible" was the Compaq Portable in 1982. It wasn't the first "compatible" to market, but it claimed to be the first that hit the "100%" mark and validated the clone market.

Re: Skype protocol reverse engineered, source available

#117

Post by comex »

Xuzz wrote: post #86
[deleted] wrote: post #84

Earlier quoted context omitted.

[deleted]

That is incorrect. I purchased IDA Pro as an individual this year, and I am a simply a student interested in reverse engineering. (I believe what you are saying may be true for the "advanced" version, but from what I can tell anyone can purchase IDA Pro Standard.)

Assuming that the deleted parent is about the difficulty of purchasing IDA, as you know, it's only somewhat incorrect. I have wanted to buy IDA for almost a year now, but Hex-Rays is very picky about how they receive their money; I could probably arrange for it somehow but it is an completely inordinate amount of hassle. (And no, bank transfers are not only required with a student discount; I was willing to pay twice as much to avoid the requirement but it wasn't possible.)

Re: Skype protocol reverse engineered, source available

#118

Post by evanwolf »

lesterbuck wrote: post #81
jcr wrote: post #51

Earlier quoted context omitted.

IBM released documentation after the PC had been cloned through "clean room" reverse engineering. http://en.wikipedia.org/wiki/IBM_PC_compatible

Then the cloners moved at warp speed. According to Wikipedia, the PC AT shipped in 1984. For nostalgia, I kept my copy of IBM Personal Computer Hardware Reference Library Technical Reference, Pub #1502494. "This manual describes the various units of the IBM Personal Computer AT and how they interact. It also has information about the basic input/output system (BIOS) and about programming support. The information in t…

I was an early Compaq employee. The documentation produced by the research team was vetted for anything not descriptive of behavior, then forwarded through lawyers, who logged each document, to the engineering team designing Compaq's compatible BIOS from the functional specs. A weird side effect: the process reproduced BIOS-level bugs for complete compatibility.

Re: Skype protocol reverse engineered, source available

#119

Post by evanwolf »

peterwwillis wrote: post #58
Animus7 wrote: post #18

If the goal is to open up Skype, this isn't the way. Even if some insane insomniac de-twiddles the pages upon pages of optimized indirection in this code (which I seriously doubt), all Skype has to do is tweak the protocol or encryption and the researcher is back to square one. It's a losing battle. And that's not even getting into the legality of it it all. How about instead of trying to fruitlessly crack Skype, we…

> How about instead of trying to fruitlessly crack Skype, we spend the time making something that's both open and better? There's value in making an open client that works with the existing network (for example, Microsoft recently killed the Skype integration plug-in for Asterix).

Skype is not yet part of Microsoft. Skype retired the little-used app on its own.

Re: Skype protocol reverse engineered, source available

#120

Post by evanwolf »

neworbit wrote: post #91
eleusive wrote: post #36

Earlier quoted context omitted.

Not very easy if they want to maintain compatibility with existing clients (especially considering they haven't updated their linux client for years now).

Backwards compatibility with linux clients probably isn't the top priority of Skype now that they're being rolled into MS, but I suspect embedded deployments on handheld devices might still keep them from deprecating.

Actually Skype runs large clouds of linux clients (or a version of the Linux client) as part of gateways hosted with some mobile operators. They care a great deal about keeping linux compatibility.
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