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When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

thunderspy.io

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Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#41

Post by zinodaur »

mjg59 wrote: post #30
zinodaur wrote: post #29

Earlier quoted context omitted.

An example: Macbook chargers these days have charge ports that are also used for USB devices. This means that if a user plugs in a compromised "charger", it can set its own HID type (and pretend it is a keyboard or a mouse), open a terminal and start typing malware into the computer. All of this is a bit silly though, because physical intervention implies a level of commitment that lends itself to more reliable appro…

And a thing you can do for machines that have built-in keyboards is refuse to enable new HID devices until the user provides affirmative consent. The people who have reason to care about these attacks have defenses, and research that demonstrates those defenses are incomplete is useful research.

Yeah thats a good point - I personally have the bad habit of clicking "yes" to that dialogue whenever I see it, since it does sometimes spuriously appear. I certainly wouldn't attempt a teardown of all of the equipment currently plugged into my machine when I saw a message like that. Do you know if HIDs can impersonate other HIDs? E.g., if you attached a dongle to a usb keyboard, could that dongle claim the identity of the keyboard and thereby avoid the prompt?

My favorite "security interface failure" is the fact that OSX apps frequently demand a user login and password in a popup window. E.g., Slack does this. It would be so easy for an app render this popup (even on a webpage!) and I would totally type my password into it. I feel like the only answer to this is to have a sacred corner of the screen that only the OS is allowed to write to

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#42

Post by ashtonkem »

nine_k wrote: post #37
ashtonkem wrote: post #12

Earlier quoted context omitted.

I just bring my own brick for such circumstances. It takes no effort for me to evaluate the security, and it’s more flexible than counting on built in USB ports.

But buses, trains, planes — they all offer a USB socket, not a power socket.

That’s not been my experience, but I’m sure it’s hyper location/company specific.

As another commenter mentioned, I too carry a battery for longer trips, which is useful for charging devices when physically on the move and away from outlets. The model I chose from Anker can also top up a MBP, albeit slowly.

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#43

Post by justaguyonline »

jeffbee wrote: post #36
justaguyonline wrote: post #5

What would it take to have a Thunderbolt/USB C condom? You know, like those standard USB adapter that just drops the data leads on a usb charger to make attacks like this impossible. Maybe we would have to implement a hardware switch on the device itself? I'm not going to feel safe charging with a public use charger until I find some way to insure only power and not data is making it to my device. Even POE feels like…

USB power delivery does not use the data lines at all. It negotiates the permissible voltage and current using Vbus pin only. There's no reason why your USB data port needs to be enabled while charging. Just disable it. I actually have a charge-only thunderbolt cable in my desk ... it's incredibly irritating because the only way to tell the difference between it and a real thunderbolt cable is that it doesn't work.

Sounds like exactly what I was looking for, where did you pick it up?

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#44

Post by ryan-c »

maxbond wrote: post #38
mjg59 wrote: post #26

Earlier quoted context omitted.

> As a general rule, anyone with physical access to your machine already owns it. People frequently say this, but never really explain it. As far as I can tell, it translates to "Nobody cares about physical security" - except it's clear that people /do/. Things like Boot Guard are only really relevant to physical attacks. DMA protection in firmware is only really relevant to physical attacks. It's extremely obvious t…

Physical access is just such a rich attack surface that keeping your computer away from malicious actors is the right and proper solution. An extreme example a pentester imparted to me once was, if someone could spend sufficient time alone with my laptop, they could remove my hard drive and insert it into an identical laptop with a hardware or firmware backdoor preinstalled. We were discussing nation-state adversarie…

> they could remove my hard drive and insert it into an identical laptop

Does that make having a layer of stickers on one's laptop also a layer of defense?

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#45

Post by AceJohnny2 »

tptacek wrote: post #10

I skimmed the paper and while the research looks solid, just in terms of the digging they did and the documentation they're providing, this website really buries its lede: if you've got a Macbook running macOS, the Macbook IOMMU breaks the DMA attack, which is the thing you're actually worried about here. Additionally, regardless of the OS you run, Macbooks aren't affected by the Security Level/SPI flash hacks they c…

Last time Tunderbolt was broken (Thunderclap [1]), it was found that the Linux driver didn't activate the IOMMU. I assume that's since been fixed.

[1] https://lwn.net/Articles/782381/

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#46

Post by microtonal »

AceJohnny2 wrote: post #45
tptacek wrote: post #10

I skimmed the paper and while the research looks solid, just in terms of the digging they did and the documentation they're providing, this website really buries its lede: if you've got a Macbook running macOS, the Macbook IOMMU breaks the DMA attack, which is the thing you're actually worried about here. Additionally, regardless of the OS you run, Macbooks aren't affected by the Security Level/SPI flash hacks they c…

Last time Tunderbolt was broken (Thunderclap [1]), it was found that the Linux driver didn't activate the IOMMU. I assume that's since been fixed. [1] https://lwn.net/Articles/782381/

It seems to do that now:

https://christian.kellner.me/2019/07/09/bolt-0-8-with-suppor...

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#47

Post by AnthonyMouse »

ryan-c wrote: post #44
maxbond wrote: post #38

Earlier quoted context omitted.

Physical access is just such a rich attack surface that keeping your computer away from malicious actors is the right and proper solution. An extreme example a pentester imparted to me once was, if someone could spend sufficient time alone with my laptop, they could remove my hard drive and insert it into an identical laptop with a hardware or firmware backdoor preinstalled. We were discussing nation-state adversarie…

> they could remove my hard drive and insert it into an identical laptop Does that make having a layer of stickers on one's laptop also a layer of defense?

Stickers are an inconvenience, especially when applied over a screw hole required for disassembly or similar, but it's not exactly cryptographically secure. What stops the attacker from buying the same sticker as you, or taking a good picture of it before destroying it and printing a new one off?

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#48

Post by mjg59 »

maxbond wrote: post #38
mjg59 wrote: post #26

Earlier quoted context omitted.

> As a general rule, anyone with physical access to your machine already owns it. People frequently say this, but never really explain it. As far as I can tell, it translates to "Nobody cares about physical security" - except it's clear that people /do/. Things like Boot Guard are only really relevant to physical attacks. DMA protection in firmware is only really relevant to physical attacks. It's extremely obvious t…

Physical access is just such a rich attack surface that keeping your computer away from malicious actors is the right and proper solution. An extreme example a pentester imparted to me once was, if someone could spend sufficient time alone with my laptop, they could remove my hard drive and insert it into an identical laptop with a hardware or firmware backdoor preinstalled. We were discussing nation-state adversarie…

> Physical access is just such a rich attack surface that keeping your computer away from malicious actors is the right and proper solution.

Keeping attackers away from your computer is certainly the best solution, just as keeping your computer off the network is the simplest answer to avoiding network security issues. But that's not always an option, so we still need to care about it.

> An extreme example a pentester imparted to me once was, if someone could spend sufficient time alone with my laptop, they could remove my hard drive and insert it into an identical laptop with a hardware or firmware backdoor preinstalled.

That'll be detected with any properly implemented remote attestation solution (switching the machine will change the endorsement key, so attestation will fail)

> If a computer is booted and the drive is decrypted, an attacker with physical access could open the computer, remove the RAM, and download it's contents, thereby stealing the encryption key.

Removing soldered-on RAM from a motherboard fast enough to maintain the contents is not a straightforward attack. Not theoretically impossible, but you're not going to have a good time of it.

> If the computer is powered down, it's still vulnerable to other attacks; enrypted drives necessarily have cleartext code for accepting the password & decrypting the drive. You could modify this code to log the decryption key, or broadcast it over your device's radios.

Will be detected via remote attestation.

> There's also the classic Windows "sticky key" exploit, where you replace the sticky key binary with a program that gives you administrator access, reboot the computer, and then activate sticky keys.

How do you do that with an encrypted drive? Look, yes, it's not easy to guard against physical attacks. But some organisations that genuinely do have to deal with state level attackers care about physical security and care about mitigating it, and we have moved well beyond the "physical access means you've lost" state of affairs. Finding new cases that allow attackers with physical access to subvert our understanding of the security boundaries of a machine is of significant interest.

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#49

Post by mjg59 »

AnthonyMouse wrote: post #47
ryan-c wrote: post #44

Earlier quoted context omitted.

> they could remove my hard drive and insert it into an identical laptop Does that make having a layer of stickers on one's laptop also a layer of defense?

Stickers are an inconvenience, especially when applied over a screw hole required for disassembly or similar, but it's not exactly cryptographically secure. What stops the attacker from buying the same sticker as you, or taking a good picture of it before destroying it and printing a new one off?

An example is using glitter-containing nail polish to cover the screws, taking a high resolution picture and then having an app that checks whether the glitter particles are still in the same position. There are companies selling solutions along these lines.

Re: When Lightning Strikes Thrice: Breaking Thunderbolt 3 Security

#50

Post by mjg59 »

osy wrote: post #23

This is the kind of garbage that the infosec community often memes about. A marketing website, a domain name, a cute logo for a vanity project masquerading as security research. Basically every one of the "seven" vulnerabilities boils down to "if someone can flash the SPI of the thunderbolt controller then xxx" but if they can flash the TB SPI, then they can also flash the BIOS SPI which has a lot of the same "vulner…

> they can also flash the BIOS SPI

Boot Guard makes that impractical in most cases. The point here is that on machines that don't implement kernel DMA protection, you're able to drop the Thunderbolt config to the lowest security level and then write-protect the Thunderbolt SPI so the system firmware can't re-enable it, making it easier to perform a DMA attack over Thunderbolt and sidestep the Boot Guard protections.

This isn't a world-ending vulnerability, but it's of interest to anyone who has physical attacks as part of their threat model.

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