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Photon-Emission-Guided Laser Fault Injection Enables RP2350 Secure Debugdonjon.ledger.com

Differential photon-emission microscopy localized debug enable register activity and narrowed the laser search before SWD-guided injection set the two bits required to restore Secure debug on an RP2350 A4.

219 points•synack•12 days ago•92 comments•
#debug#photon#rp2350#emission#injection#guided#secure#laser

92 comments

BitBangingBytes12 days ago
I appreciate all the details they provide in the post. The $250k in lab gear is useful when initially discovering, exploiting and documenting attacks like this.

Definitely doable in a home lab for under $25k in equipment, likely under $10k.

Same as my replicating Colin O’Flynn’s BAM BAM attack on a MPC5566 chip, he used a ChipShouter ($5,000) and I used a PicoEMP ($50).

https://youtu.be/URmI1VVilek

throwaway8152312 days ago
Nice, thanks. I had wondered whether the $250K in lab gear is something that a serious HW security lab would already have on hand, as opposed to specialized expenditure for just this attack. I mean I rode in a $250K(?) motor vehicle a few days ago (the #2 SF Muni bus towards the Marina) but I didn't have to spend a lot to ride it, since it was already deployed. Nobody had to go out and buy it.
junofan12 days ago
Hah, our new ones are $1.3 million. https://www.sfmta.com/media/44081

Perhaps driven by restrictions on federal grants? https://media.api.sf.gov/documents/Briefing_Book_-_Muni_Fund...

Some cool tech. Wonder if we optioned the inductive charging system. https://www.gillig.com/buses/battery-electric/#1731934845437...

SV_BubbleTime12 days ago
I have an application on an SPC58 that I really want to know more about. But unfortunately; it’s a dual core with lockstep. So if it could be done; I think that automatically double-pluses the budget.
BitBangingBytes11 days ago
Don’t need lasers for that chip, it absolutely can be done with enough time and effort.

Don’t let fancy language like lock-step dissuade you from trying. The people who configured that chip also have to have done their job perfectly or it might still have a way in!

byb12 days ago
The RP2350's secure enclave made it particularly attractive for use as a Yubikey alternative.

There will always be an arms race between safe-crackers and safe-builders. Presumably the lessons learned will help make the next generation tougher to break into.

mitxela12 days ago
In this case the safe belongs to the person who's trying to crack it.
rcxdude12 days ago
Well yeah, but I would like to be able to make my own safe that is at least very difficult to crack if someone steals it. Companies are seemingly hellbent on stopping me owning the stuff they want to sell to me regardless, I might as well benefit from the same tech.
octoberfranklin12 days ago
There will always be an arms race between safe-crackers and safe-builders.

This is dismissive and glib. And it's the wrong lesson.

You wouldn't say this about symmetric cryptography. AES-encrypted ciphertexts from 25 years ago are still secure today, and nothing on the horizon is likely to change that. No arms race.

The "arms race" exists because the security model for trusted hardware is intrinsically flawed. If the attacker has physical posession of the device, your security is transient and at the mercy of the arms race. So stop doing this! Trusted hardware also has extremely negative externalities on the whole computing ecosystem.

(*) or 45 years, if you exclude cryptosystems (56bit single-DES) used only because of silly export laws.

vexed_vulpine12 days ago
I tend to agree that there are issues in the realm of hardware token based security but they largely lie in the failure modes, with substantially increased difficulty of recovery.

For the average user these approaches make data loss MUCH more likely simply because you need a corporate IT department level of competency to consistently avoid data loss with them.

The glib exaggeration of this is that in not being permitted to manage and back up your own keys you actually create the situation where you have to hire someone to extract your keys for you and break into the device you own because of the failings of the technology!

zephen12 days ago
> This is dismissive and glib.

As is your comment.

> And it's the wrong lesson.

It's only the wrong lesson if you believe that making it more difficult for governments to seize and decrypt their own citizens' mobile phones with impunity is not a valid goal.

> the security model for trusted hardware is intrinsically flawed.

It's only intrinsically flawed if you expect absolute perfection.

The fact that some math-based protections may be theoretically better than physical protections does not obviate the utility of physical protections, whether we are discussing computers or phones, or houses or cars.

It has been accepted since before any of us were born that there is no such thing as perfect physical security. Even your putative perfect cryptographic security still relies on the physical security of the plant holding the keys.

ImPostingOnHN11 days ago
>> There will always be an arms race between safe-crackers and safe-builders.

> You wouldn't say this about symmetric cryptography. AES-encrypted ciphertexts from 25 years ago are still secure today, and nothing on the horizon is likely to change that. No arms race.

AES encrypted ciphertexts are not a safe. A safe is a physical object.

> If the attacker has physical posession of the device, your security is transient and at the mercy of the arms race.

That's what we're discussing, yes: a scenario in which physical access to a safe is already acquired. Given that context, don't you think changing the topic to 'non-safes' and 'avoiding physical access' is a little dismissive and glib?

akoboldfrying12 days ago
Impressive work!

I have a side question. I looked into the linked Raspberry Pi hacking challenge, and there's something very basic I couldn't figure out: It looks like the relevant script in the repo just writes 0xc0ff 0xffee a few times to the OTP as the "secret" to unlock. But given that $20000 was up for grabs, this can't possibly be the genuine secret being sought to claim the prize. (Indeed, I can't think of a secure way to install a secret from a public GitHub repo unless it involves running on-device code that encrypts something using some other, factory-installed secret key, which is just kicking the can down the road.) And given that the OTP on a brand new RP23550 is initialised to all zeros, it can't be that the genuine secret is programmed in at the factory either.

What am I missing? How does the genuine secret get installed on a person's RP2350?

striking12 days ago
> If you think you have found a break email us at [email protected] with details - we will ship you a Pico2 with a custom secret hidden in it. If you manage to extract it, you win the $20,000!
akoboldfrying12 days ago
Thank you, don't know how I missed that!
nullc12 days ago
I'm confused by a number of comments here and the article seemingly taking a position that a $250k lab instrument is required.

For one a similar instrument can be constructed from surplus parts for far less. Secondly, it's a single bit flip required. Now knowing the the technique works, a harness could be built that attempts it scattershot without the precise targeting and just has to try a lot of times. Using a different stimulus, e.g. xray it might well be possible without deencapsulating the part.

jacquesm12 days ago
That's reminiscent of when we first found out that if you opened up dram chips you could use them for imaging. Of course the scale at which this is done is extremely impressive.
xattt12 days ago
For the curious: https://hackaday.com/2014/04/05/taking-pictures-with-a-dram-...
jacquesm12 days ago
A lot earlier than that.

https://www.cs.uaf.edu/2007/fall/cs441/support/dram_sensor_1...

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