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Comment by Cushman | Hacker News Reader

That is damn clever to be sure— but calling it a "very real" threat is a little sensationalist. In this day and age, an attack involving physical access is of little relevance to consumers. In fact, replacing the battery on a MacBook is only marginally more difficult than replacing the hard drive. Of course I'm sure various government organizations are going to have some stern questions for Apple nevertheless...

Anyway, they've already fixed this vulnerability in my MacBook Air. I'm not worried.

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It's kind of a degree beyond the traditional 'physical access' attack though. This means that if you buy a replacement battery for your MacBook, it could contain malware. In fact, even the legitimate battery you purchased from Apple could maintain malware, if someone slipped it in at the manufacturer. You could say that traditional vetting of manufacturers and security processes would prevent this, but really, who's going to think of the potential for a battery to compromise your security?

Then so could the replacement hard drive, any USB sticks you buy, any USB connecting peripheral, etc.

Not quite, there is already heavy protection against nasty peripheral devices.

I don't think so. Certainly not for any peripheral that is allowed to do DMA. Though plugging in a malicious firewire peripheral is a lot more practical than replacing the battery...

http://www.hermann-uwe.de/blog/physical-memory-attacks-via-f...

When there's already semi-legitimate worries that the Chinese government could have spyware chips installed on computer motherboards, this would be a lot more malicious, easier to perform and initially far less detectable.

From the post, the author says the battery could repeatedly install malware or spyware to your computer.

What would be more worrying is if someone found a way to hack directly to you battery. IE a virus you get installs itself to your battery as its resurrection method rather than in a system file. Worse yet would be if someone maliciously wrote a virus that caused your battery to overcharge a month down the road.

Imagine all those stupid MSN virus' if they could fry your laptop battery.

You don't need a government's resources. You need a programmable firewire device, like an embedded Linux device. You also need ten seconds of physical access to their FireWire port. That's a lot easier than hacking a battery and convincing the target to use the battery.

How is that different from hacking the ASIC of the network card?

http://www.links.org/?p=330

Even Charlie Miller says he doesn't know how you would embed malware on a device using this attack.

That's of course beyond the point that a great many other things you buy at a computer store could more easily contain malware.

This attack wouldn't require physical access. The researcher analyzed a firmware update that Apple had sent out to reverse engineer the passwords, which he then used to poke around the code in the battery.

Theoretically, malware could get onto a machine by whatever means, then use the battery as a nasty hiding place, or target the battery itself.

EDIT: It should be noted that a second vulnerability will be needed to get code from the battery into the machine.

I have zero familiarity with Charlie's research, but I have a (passing) familiarity with battery controllers, and the malware-hiding-on-battery thing doesn't add up to me. How does the battery access host memory? It's not like these things do DMA, right?

That's the second vulnerability that would need to be found. Maybe it's locked down and we're okay. Or maybe the code in OSX that reads the battery's health and capacity has a buffer waiting to be overflowed.

My impression is that the "second vulnerability" Charlie is talking about is the remote->kernel transit needed to allow you to talk to the battery in the first place.

This sounds bi-directional, though (as in you could run some software with a payload that overloads/overheats your battery).

Indeed, according to the article, it could be bidirectional:

>Using that password, Miller said that he has been able to do almost anything from giving false readings to the charger and the OS to ruin the device, to completely rewriting the firmware.

I don't know if it would be possible to make the battery burst into flame or explode. After the Sony battery fiasco, I'd expect there to be some kind of hardware interlock preventing short-circuits. However, it is possible to overwrite the battery firmware to prevent the battery from being charged, thus turning your Macbook Pro into a very small form-factor desktop.

Actually, Macbooks use lithium polymer batteries which are highly explosive when overcharged (http://www.youtube.com/watch?v=0MiM2E6pvfg). So by telling the OS that a battery is not charged when it really is can cause it to explode.

That's a bare LiPo cell wired directly to current— not a good demonstration of how a well-designed battery pack would behave, even one with malicious firmware.

I had an internship at a company that made lithium battery packs. The control boards on the packs have primary cell protection provided by a specialized micro controller that monitors cell voltages and prevents over/under charge levels and monitors current, however they also have secondary protection ICs that are hardware based that will shut down the pack should the cells reach dangerously high levels, as well as fuses to prevent dangerous levels of current.

Net result, changing battery firmware can reduce usefulness of battery (higher charging degrades cell life, blow fuses etc) but the packs should have hardware based protection from being a safety hazard

Which is non-threatening for the inverse reason; somebody who owns my OS can probably damage my hardware if they want to. Ruining the SSD in my Air would mean a replacement just as surely as trashing the battery, and would be a lot easier.

Now in fairness, being able to make something in my computer start a fire is on a way different level. But we're getting that from "Miller said that it might even be possible to overload the battery so that it catches fire"— he hasn't done it, and doesn't even know if it's possible. My money is on there are some lower-level safeguards to prevent bugs in the firmware from causing fires, even if they do ruin the battery. Li-ion batteries are designed physically with the knowledge that they're a ticking timebomb waiting to go off, and I can't believe that nobody at Apple has started from asking "But what if I were actually trying to make it explode."

Yeah, _access is ownership_, after all.

background: Mac boots from all media except retail OS X installation media. I try everything including paying $50 to be told "we don't know"... when I resort to resetting the SMC.

observation: Turns out, the battery is secured with Y-cut-head screws, rather than the traditional Phillips screws of the hard drive.

So not only is the hard drive a more obvious target... it's considerably easier to get to in my opinion. (Unless people have Y-shaped screwdrivers lying around, who knows).

SMC reset is done with a key combo on newer MBP's without the latch bottom, you don't have to pull the battery.

You're right, I missed the fine print. Thanks for getting me to look again: http://support.apple.com/kb/ht3964 (look for "Resetting the SMC on portables with a battery you should not remove on your own", how silly of me, I shouldn't remove it because they used proprietary screws)

Regardless, I think it still speaks to the notion that the battery is harder to attack than the hard drive other than the more obvious reasons.

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