Chromium Blog: A Tale Of Two Pwnies (Part 2)

http://blog.chromium.org/2012/06/tale-of-two-pwnies-part-2.html

by cleverjake • 14 years ago

197 63 14 years ago

blog.chromium.org

tptacek• 14 years ago

Once again, there's two ways of reading this story. One way is from the attacker's perspective, baffling yourself as to how Glazunov could have found all these bugs and assembled them in the right order. The other is from the defender's perspective, gaining an appreciation for how well the security model is working that it takes an exploit this intricate to break it.

Either way, you're doing something right when your documentation of a security vulnerability in your product actually serves to market the security of that product. The Chrome security team is doing a lot of stuff right.

Splines• 14 years ago

It'd be interesting to read about how Glazunov & Pinkie Pie figured all this out. What did they try that worked, what didn't work, how long did they spend on this, what tools did they use?

tedunangst5• 14 years ago

For this exploit, the security defenses didn't impress me as much. The immediate question I have is why are there chrome:// URLs at all? It seems you could achieve a much stronger sandbox by using native UI controls that are simply not attached to the webview. Then it would not be possible to trick it into making a same origin mistake.

I mean, this is standard advice for web apps and services, right? You build the control interface completely outside the main user app.

ajross2• 14 years ago

A lot of it is just "The Way It's Done", I'm sure. The "about://" and "about://plugins" urls have worked since the very early days of Netscape (and still do in chrome, which redirects them appropriately). It's an interface that Chrome inherited. They didn't design it, so it didn't receive the same security attention.

aboodman2• 14 years ago

There are a lot of answers to this question:

1) From a UX perspective, we prefer to have the majority of the UI within a tab. We don't want to build up an entirely separate UI hierarchy outside tabs.

2) We tried putting native UI within a tab in early versions of Chrome, and it did not feel right. There was an uncanny valley effect. If the content of a tab doesn't feel like HTML, it feels wrong. And it isn't practical to emulate the feel of HTML perfectly with native code.

3) The Chrome team puts a lot of engineering effort into making the web platform as strong as it can be. We would like to eat our own dogfood when possible.

emmelaich• 14 years ago

I agree that these urls would be a target for exploits; an obvious place to target. I even guessed that this change to 'unreachables' was part of closing the security hole: http://news.ycombinator.com/item?id=3686730

petegrif• 14 years ago

Mind blowing. And so great you publish it all to improve the product.

datr• 14 years ago

In Part 1 it's mentioned that they held up publishing this issue as it affects many other products:

"While these issues are already fixed in Chrome, some of them impact a much broader array of products from a range of companies. So, we won’t be posting that part until we’re comfortable that all affected products have had an adequate time to push fixes to their users."

Presumably this is referring to other webkit browsers and the wordpad.exe exploit. Does anyone know if these problems have been fixed yet?

tedunangst5• 14 years ago

The wordpad exploit, unless I'm mistaken, is basically just the equivalent of LD_PRELOAD. As such, there's nothing to fix.

This may be of some interest, as it there's some discussion of when it's an exploit and when it's just the way things are supposed to be. http://news.ycombinator.com/item?id=3005832

kvnn• 14 years ago

Google has changed the relationship between exploiters and themselves into something symbiotic and fun.

How refreshing it is to hear excitement and admiration when a large tech company speaks about an exploit made in one of its products.

Super awesome.

[ See http://blog.chromium.org/2012/02/expanding-chromium-security... ]

vibrunazo• 14 years ago

$60k seems kind of cheap after reading all that.

rosstafarian• 14 years ago

yeah it's a pretty amazing hack. I believe the guy who wrote it is a university student from russia(who also found other holes in chrome) so for him the $60k will go quite a bit further then for some one else and the prestige/job offers associated with it will go even further then that.

When the event was going on, another group called vupen(french company that deals in selling 0day exploits to govts) that found a hole in chrome during that contest refused to give up their method, when offered $120k instead of $60 and their ceo half jokingly said he might give it up for the entire million dollars worth of prizes google was offering

jmillikin8• 14 years ago

Is anyone else dismayed by the implicit view of these sorts of articles, that browsers should be complicated and full of all these insecure features?

It reminds me strongly of PDF and Acrobat. PDF is great for mailing around print-ready documents, which are more-or-less guaranteed to look the same for every viewer. Writing a PDF renderer is not easy, but it is straightforward, and there are multiple stable implementations without significant security problems.

Then Adobe comes along and they add forms, and 3D charts, or Javascript, or multimedia, and Acrobat grows from a document viewer into what is essentially a backdoor on every Windows computer.

A similar thing is happening with browsers. The core purpose of a web browser is the ability to render HTML+CSS into a human-readable document. Then browser vendors added forms and Javascript, so XSS was invented. They added persistent data storage, so looking at cat pictures can compromise my bank account. And now, Chrome+Firefox are /competing/ to see who can add more features, security be damned.

WebGL exposes your graphics drivers (never security-audited before) to the internet. <audio> and <video> expose multimedia codecs, which in the past have caused numerous security problems. Flash is, essentially, a cross-platform way to let arbitrary people run exploits on your machine.

When will it stop? When will browser vendors take a collective breath, look around, and realize the insanity they've been perpetrating?

ajross2• 14 years ago

If browsers didn't do it then some other software would fill the niche. Having general purpose computers to run code written by other people is something everyone wants. Your attitude above seems to be that Javascript is a bad thing, which IMHO is just insane.

And the bit about "security be damned" is just flat wrong, as evidenced by the linked article. They're working very hard at getting the sandbox architecture right, and have been so successful that it takes a hack of this magnitude to actually break it.

jmillikin8• 14 years ago

  > If browsers didn't do it then some other software would
  > fill the niche. Having general purpose computers to run
  > code written by other people is something everyone wants.

It's fine to run code written by other people, but that code should be run in a safe, completely sandboxed environment. Modern smartphones have it right -- the user downloads an application, typically written in native code (or pseudo-native, for Android), and that application has only very limited access to the system.

The $0.99 game I downloaded does not have the ability to inject keylogging code into my bank management application, and this is enforced by the OS itself.

  > Your attitude above seems to be that Javascript is a bad
  > thing, which IMHO is just insane.

I don't think it's insane at all. Implementing applications as the moral equivalent of a highly-dynamic text document is what's insane. The concept of a "web app" is fundamentally broken, but despite users largely rejecting it (see: popularity of native apps vs safari apps on iPhone), nerds keep pushing it because it seems like a cool plot to a sci-fi novel.

  > And the bit about "security be damned" is just flat
  > wrong, as evidenced by the linked article. They're
  > working very hard at getting the sandbox architecture
  > right, and have been so successful that it takes a hack
  > of this magnitude to actually break it.

This is security after the fact. If they actually cared about security, they'd disable Javascript, disable Flash, disable WebGL, and turn Chrome back into a web browser.

When a boat is sinking because the hull was made of cardboard, don't point to the conveniently-placed bailing buckets as evidence of good engineering.

obeattie• 14 years ago

So… what are you proposing? We go back to the web as it was in 1995?

jmillikin8• 14 years ago

I propose we give up on the flawed idea of "web apps", and go back to native applications. Mac OS, iOS, and Android show us that this is both possible and practical.

The web can continue to be what it was and should be, a set of interlinked documents to be interpreted by applications installed on the local computer.

azakai3• 14 years ago

> Is anyone else dismayed by the implicit view of these sorts of articles, that browsers should be complicated and full of all these insecure features?

You're taking a position 100% against all additions to web browsers, it seems. And some people responding to you are taking the 100% opposite position. But there is a middle ground.

Browsers should include the minimal amount of technology possible, and strike a compromise between number of features and security (because more features always means less security). What the right compromise is, is of course debatable.

But I don't want to just say "extremes are wrong, the right middle way is best" in a generic manner because that's always true. More specifically, Google is the browser vendor including the most nonstandard technologies these days, and therefore incurring the most risk. For example, NaCl, WebSQL, a large extension API (even including things like text to speech), a closed-source PDF reader, Adobe Flash, Chrome Web Store frontend, and apparently soon Dart. All those things add to the attack surface of Chrome, I would argue needlessly.

Of course other browsers are guilty of similar things, just to a lesser extent. At least Microsoft does not bundle Silverlight with IE (but it will apparently bundle Flash..).

jmillikin8• 14 years ago

I don't think my position is extreme. I'm not advocating for a removal of all browser features, merely removal of those which are unrelated to the browser's core purpose of document navigation and rendering.

If browser vendors spent less money on implementing audio synthesis or OpenGL, they could spend more on font rendering, SPDY, and standards compliance.

recoiledsnake2• 14 years ago

>At least Microsoft does not bundle Silverlight with IE (but it will apparently bundle Flash..).

If I remember correctly, Flash is only enabled for a set of whitelisted sites. But, as we see, someone will probably chain that to some other vulnerability.

gringomorcego• 14 years ago

I think people are ignoring the end plan.

Native Client isn't for running apps quickly. It's for finally letting Google create a sandbox that they can run their own browser in.

Probably won't happen until HVM support is growing at a certain level.

nikic• 14 years ago

This comment is wrong on just so many levels.

You seem to think that browser are less secure than running native software. This is totally absurd. And this blog entry shows exactly that. In order to bypass the advanced sandboxing techniques employed by modern browsers you have to build up complex chains of dozens of bugs.

This is very different with desktop software. Desktop software is protected far less than code running in the browser.

So the idea that running apps in the browser makes you more vulnerable than running native applications seems very unrealistic.

Also you seem to have the very nostalgic view that the web should be just static websites with a few links in between. This concept again seems completely absurd. From my point of view as a PHP programmer the dynamic web is pretty much the best thing that happened to mankind. It allows you to run software without having to install it. From everywhere. From the the point of view of the end user this is still true. Just look around. Look at Facebook, Twitter and stuff.

tytr• 14 years ago

Yes. I too am dismayed.

There used to be something called MIME. There used to be separate specialised applications for different tasks.

Guess what? There still are.

Browsers have long had the ability to decode image formats. That much we expect from the browser.

But audio? Video? "Web sockets"?

There are better applications to handle these formats and tasks than a web browser.

When I want to listen to audio, I use an application that is designed for that.

When I want to watch video, I use an application that is designed for that.

When I want to open sockets for peer-to-peer communication, I use an application that is designed for that.

Everyone knows browsers suck for downloading. So why are we using them to download content (whether to a file or to a buffered cache)?

Download the content using a program that is designed for downloading.

View/play the content with applications designed for those tasks.

Anyone who would criticise this approach is criticising the "UNIX way". Do one thing well. But watch how people will criticise it.

Yes, it is insanity.

These browsers are always going to have performance issues. If you want the best audio, video, peer-to-peer, etc., use applications that were designed for those purposes. As simple as possible. Simple applications. That is how you achieve performance, reliability and security.

"Do-everything" browsers and Javascript are not not worth the risks they present.

adhipg• 14 years ago

The problem with such an approach is that it makes computers hard to use - hard enough that 99% will not want to use it.

icebraining2• 14 years ago

Web sockets are not for P2P. They're just raw TCP sockets to servers with an initial HTTP-like handshake.

Personally, I can fully understand your points, and I actually take exactly that approach (using youtube-dl + mplayer for Youtube, extracting the streaming URLs from online radios and plugging them in MPD, etc).

But, as a Linux user, I'm all too accustomed to be left out from many applications because this platform isn't profitable enough to develop to.

Browser applications break with the monoculture of Windows (or, on mobile, iOS+Android) because they're portable and open by default. And I think that has some value.

richardw• 14 years ago

I'd just like to point out that Google significantly raised the state of the art with respect to browser security, specifically because they made it central to their effort. They had a more secure browser within a year than the other vendors had created since the birth of the web.

This is a minor setback and I have no doubt that they've learned not only just how to fix this set of bugs, but the bug classes they represent.

Netscape won (at the time) partly on "features", so browser competitors have to release features, balanced with their other priorities. Can't go back, can only go forward as responsibly as possible. Chrome has done this admirably.

I suggest looking at these tests through a half-full glass. There's a huge benefit in discovering multi-bug exploits, for Chrome, Google, other browser vendors and all users. When an attacker is looking to break into a computer, Chrome is not their most obvious starting point. In fact, IIRC Kevin Mitnick said this:

"KH: What’s the most secure OS? Is there one that you can recommend?

KM: I don’t know of any secure OS. In the past eight years, I’ve had 100% success at penetration testing on all of them. Wait, ChromeOS, ChromeOS is the most secure because of its very limited attack vector–there’s just nothing to exploit."

http://www.zdnet.com/blog/security/ghost-in-the-wires-the-ke...

That's progress, surely.

nikcub• 14 years ago

browsers are the new operating system, but what was learned in security architecture of operating systems wasn't carried across.

chrome et al at the moment (and other browsers) are the security equivalent of DOS - single user, unprotected memory, no file permissions etc.

a lot has been done well with isolating the browser from the operating system, but within the browser itself is where more and more interesting information is being held, and the security model there is almost non-existant.

mcot2• 14 years ago

The idea of "perfect security" is a myth. The best approach to security is doing exactly what google is doing:

Off the top of my head:

1.) Spend a lot of time and money on security engineering. 2.) Constantly update, make sure it is not a hassle for users to update. Preferably force them to update, design with patching and updates built in and with minimal impact. 3.) Hire/pay a lot of people to try to break your shit. 4.) Keep a keen eye out for undisclosed vulnerabilities/exploits on the black market and have an easily accessible reporting mechanism for white hats which you do not pay. 5.) Notify the crap out of your uses when something goes wrong.

You can easily see why programs such as old versions of Adobe Flash and Reader were terrible from a security perspective if you try to compare them to the above criteria.

Talking about complexity and operating system design opens up a new can of worms. With iOS I think Apple is taking the extreme approach which works for like 99% of people who are not power users...

1.) Isolate everything. 2.) No third party apps that Apple does not approve. 3.) Everything is digitally signed. 4.) Limit apps from running other code. 5.) Be able to kill switch apps or wipe the device remotely.

Chromium Blog: A Tale Of Two Pwnies (Part 2)

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