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Lowering JavaScript Timer Resolution Thwarts Meltdown And Spectre

January 6, 2018 by 35 Comments

The computer security vulnerabilities Meltdown and Spectre can infer protected information based on subtle differences in hardware behavior. It takes less time to access data that has been cached versus data that needs to be retrieved from memory, and precisely measuring time difference is a critical part of these attacks.

Our web browsers present a huge potential surface for attack as JavaScript is ubiquitous on the modern web. Executing JavaScript code will definitely involve the processor cache and a high-resolution timer is accessible via browser performance API.

Web browsers can’t change processor cache behavior, but they could take away malicious code’s ability to exploit them. Browser makers are intentionally degrading time measurement capability in the API to make attacks more difficult. These changes are being rolled out for Google Chrome, Mozilla Firefox, Microsoft Edge and Internet Explorer. Apple has announced Safari updates in the near future that is likely to follow suit.

After these changes, the time stamp returned by performance.now will be less precise due to lower resolution. Some browsers are going a step further and degrade the accuracy by adding a random jitter. There will also be degradation or outright disabling of other features that can be used to infer data, such as SharedArrayBuffer.

These changes will have no impact for vast majority of users. The performance API are used by developers to debug sluggish code, the actual run speed is unaffected. Other features like SharedArrayBuffer are relatively new and their absence would go largely unnoticed. Unfortunately, web developers will have a harder time tracking down slow code under these changes.

Browser makers are calling this a temporary measure for now, but we won’t be surprised if they become permanent. It is a relatively simple change that blunts the immediate impact of Meltdown/Spectre and it would also mitigate yet-to-be-discovered timing attacks of the future. If browser makers offer a “debug mode” to restore high precision timers, developers could activate it just for their performance tuning work and everyone should be happy.

This is just one part of the shock wave Meltdown/Spectre has sent through the computer industry. We have broader coverage of the issue here.

Let’s Talk Intel, Meltdown, And Spectre

January 5, 2018 by 150 Comments

This week we’ve seen a tsunami of news stories about a vulnerability in Intel processors. We’re certain that by now you’ve heard of (and are maybe tired of hearing about) Meltdown and Spectre. However, as a Hackaday reader, you are likely the person who others turn to when they need to get the gist of news like this. Since this has bubbled up in watered-down versions to the highest levels of mass media, let’s take a look at what Meltdown and Spectre are, and also see what’s happening in the other two rings of this three-ring circus.

Meltdown and Spectre in a Nutshell

These two attacks are similar. Meltdown is specific to Intel processors and kernel fixes (basically workarounds implemented by operating systems) will result in a 5%-30% speed penalty depending on how the CPU is being used. Spectre is not limited to Intel, but also affects AMD and ARM processors and kernel fixes are not expected to come with a speed penalty.

Friend of Hackaday and security researcher extraordinaire Joe Fitz has written a superb layman’s explanation of these types of attacks. His use of the term “layman” may be a little more high level than normal — this is something you need to read.

The attack exploits something called branch prediction. To boost speed, these processors keep a cache of past branch behavior in memory and use that to predict future branching operations. Branch predictors load data into memory before checking to see if you have permissions to access that data. Obviously you don’t, so that memory will not be made available for you to read. The exploit uses a clever guessing game to look at other files also returned by the predictor to which you do have access. If you’re clever enough, you can reconstruct the restricted data by iterating on this trick many many times.

For the most comprehensive info, you can read the PDF whitepapers on Meltdown and Spectre.

Update: Check Alan Hightower’s explanation of the Meltdown exploit left as a comment below. Quite good for helping deliver better understanding of how this works.

Frustration from Kernel Developers

These vulnerabilities are in silicon — they can’t be easily fixed with a microcode update which is how CPU manufacturers usually workaround silicon errata (although this appears to be an architectural flaw and not errata per se). An Intel “fix” would amount to a product recall. They’ve already said they won’t be doing a recall, but how would that work anyway? What’s the lead time on spinning up the fabs to replace all the Intel chips in use — yikes!

So the fixes fall on the operating systems at the kernel level. Intel should be (and probably is behind the scenes) bowing down to the kernel developers who are saving their bacon. It is understandably frustrating to have to spend time and resources patching these vulnerabilities, which displaces planned feature updates and improvements. Linus Torvalds has been throwing shade at Intel — anecdotal evidence of this frustration:

“I think somebody inside of Intel needs to really take a long hard look at their CPU’s, and actually admit that they have issues instead of writing PR blurbs that say that everything works as designed.”

That’s the tamest part of his message posted on the Linux Kernel Mailing List.

Stock Sales Kerfuffle is Just a Distraction

The first thing I did on hearing about these vulnerabilities on Tuesday was to check Intel’s stock price and I was surprised it hadn’t fallen much. In fact, peak to peak it’s only seen about an 8% drop this week and has recovered some from that low.

Of course, it came out that back in November Intel’s CEO Bryan Krzanich sold off his Intel stock to the tune of $24 Million, bringing him down to his contractual minimum of shares. He likely knew about Meltdown when arranging that sale. Resist the urge to flame on this decision. Whether it’s legal or not, hating on this guy is just a distraction.

What’s more interesting to me is this: Intel is too big to fail. What are we all going to do, stop using Intel and start using something else? You can’t just pull the chip and put a new one in, in the case of desktop computers you need a new motherboard plus all the supporting stuff like memory. For servers, laptops, and mobile devices you need to replace the entire piece of equipment. Intel has a huge market share, and silicon has a long production cycle. Branch prediction has been commonplace in consumer CPUs going back to 1995 when the Pentium Pro brought it to the x86 architecture. This is a piece of the foundation that will be yanked out and replaced with new designs that provide the same speed benefits without the same risks — but that will take time to make it into the real world.

CPUs are infrastructure and this is the loudest bell to date tolling to signal how important their design is to society. It’s time to take a hard look at what open silicon design would bring to the table. You can’t say this would have been prevented with Open design. You can say that the path to new processors without these issues would be a shorter one if there were more than two companies producing all of the world’s processors — both of which have been affected by these vulnerabilities.

Guide: Why Etch A PCB When You Can Mill?

January 4, 2018 by 83 Comments

I recall the point I started taking electronics seriously, although excited, a sense of dread followed upon the thought of facing the two main obstacles faced by hobbyists and even professionals: Fabricating you own PCB’s and fiddling with the ever decreasing surface mount footprints. Any resistance to the latter proves futile, expensive, and frankly a bit silly in retrospect. Cheap SMD tools have made it extremely easy to store, place, and solder all things SMD.

Once you’ve restricted all your hobbyist designs/experiments to SMD, how do you go about producing the PCBs needed for prototyping? Personally, I dread the thought of etching my own boards. The process is laborious and involves messy chemicals and specially sensitized PCB’s — none of which interest me. I’ve only ever done it a few times, and have promised myself never to do it again. Professional but cheap PCB manufacturing is more like it board pooling services such as OSH park have made this both easy and affordable — if you can wait for the turnaround.

So what are the alternatives? If you are really serious about swift prototyping from your own Lab, I put forth the case of milling your own PCB’s. Read on as I take you through the typical workflow from design to prototype and convince you to put up with the relatively high start up cost of purchasing a PCB mill.

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Upgrading A 3D Printer With OctoPrint

January 3, 2018 by 56 Comments

If you’ve been hanging around 3D printing communities, or reading the various 3D printing posts that have popped up here on Hackaday, you’ve almost certainly heard of OctoPrint. Created and maintained by Gina Häußge, OctoPrint allows you to turn an old computer (or more commonly a small ARM board like the Raspberry Pi or BeagleBone) into a network-accessible control panel for your 3D printer. Thanks to a thriving collection of community developed plugins, it can even control other hardware such as lights, enclosure heaters, smart plugs, or anything else you can think to hook onto the GPIO pins of your chosen ARM board. The project has become so popular that the new Prusa i3 MK3 has a header on the control board specifically for connecting a Pi Zero W running OctoPrint.

Even still, I never personally “got” OctoPrint. I was happy enough with my single printer connected to my computer and controlled directly from my slicer over USB. The majority of the things I print are of my own design, so when setting up the printer it only seemed logical that I would have it connected to the machine I’d be doing my designing on. If I’m sitting at my computer, I just need to rotate my chair to the right and I’m at my printer. What do I need to control the thing over WiFi for?

But things got tricky when I wanted to set up a second printer to help with speeding up larger projects. I couldn’t control them both from the same machine, and while I could print from SD on the second printer if I really had to, the idea seemed painfully antiquated. It would be like when Scotty tried talking into the computer’s mouse in “Voyage Home”. Whether I “got it” or not, I was about to dive headfirst into the world of OctoPrint.

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When A Skimmer Isn’t A Skimmer

January 2, 2018 by 163 Comments

I have a confession to make: ever since the first time I read about them online, I’ve been desperate to find an ATM skimmer in the wild. It’s the same kind of morbid curiosity that keeps us from turning away from a car accident, you don’t want to be witness to anyone getting hurt, but there’s still that desire to see the potential for danger up close. While admittedly my interest is largely selfish (I already know on which shelf I would display it), there would still be tangible benefits to the community should an ATM skimmer cross my path. Obviously I would remove it from the machine and prevent others from falling prey to it, and the inevitable teardown would make interesting content for the good readers of Hackaday. It’s a win for everyone, surely fate should be on my side in this quest.

So when my fingers brushed against that unmistakable knobby feel of 3D printed plastic as I went to insert my card at a local ATM, my heart skipped a beat. After all these years, my dream had come true. Nobody should ever be so excited about potentially being a victim of fraud, but there I was, grinning like an idiot in the farmer’s market. Like any hunter I quickly snapped a picture of my quarry for posterity, and then attempted to free it from the host machine.

But things did not go as expected. I spend most of my free time writing blog posts for Hackaday, so it’s safe to say that physical strength is not an attribute I possess in great quantity, but even still it seemed odd I couldn’t get the skimmer detached. I yanked it in every direction, tried to spin it, did everything short of kicking it; but absolutely no movement. In fact, I noticed that when pulling on the skimmer the whole face plate of the ATM bulged out a bit. I realized this thing wasn’t just glued onto the machine, it must have actually been installed inside of it.

I was heartbroken to leave my prize behind, but at the very least I would be able to alert the responsible party. The contact info for the ATM’s owner was written on the machine, so I emailed them the picture as well as all the relevant information in hopes that they could come check the machine out before anyone got ripped off.

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Great People And Culture At 34th Chaos Communication Congress

January 2, 2018 by 18 Comments

If you’ve been to a Chaos Communication Congress, you know the feeling — the strange realization after it’s all over that you’re back in the “real world”. It’s somehow alienating and unfriendly in comparison to being surrounded by computer freaks, artists, hackers, activists, coders, and other like-minded individuals over the four days of the Congress. A hand-written poster by the podcasting center read “Endlich, normale Leute” — “At last, normal people” — which is irony piled on irony but the sentiment is still right for certain strange values of “normal”. Normal hackers? You’d probably fit right in.

We cover a lot of the talks from the Congress, because they’re first-class and because you can play along at home, but the real soul of the Congress is people getting together, making something temporary and crazy, talking over their common plans, learning new things directly from one-another, and simply having fun. Here’s our chance to give you a little of the other side of the Congress.
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34C3: North Korea’s Consumer Technology

December 30, 2017 by 19 Comments

[Will Scott] and [Gabe Edwards] shed some light on the current state of consumer computing technology at 34C3 in their talk DPRK Consumer Technology. The pair has also created a website to act as a clearinghouse for this information — including smartphone OS images up at koreaComputerCenter.org.

Not a whole lot is known about what technology North Korean citizens have available to them. We have seen Red Star OS, the Mac-like Linux based operating system used on PC based desktops. But what about other systems like smartphones?

[Will] and [Gabe] found that cell phones in North Korea are typically manufactured by Chinese companies, running a custom version of the Android Operating system. The phone hardware is common — the phone sold as the Pyongyang 2407 in North Korea is also sold in India as the Genie v5. If you can get your hands on the Genie, you can run the Korean version of the Android OS on that hardware.

Continue reading “34C3: North Korea’s Consumer Technology” →