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Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

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Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#41

Post by brokenmachine »

noonespecial wrote: post #23
LeifCarrotson wrote: post #6

This is an interesting attack, and certainly looks highly successful in terms of allowing a determined hardware hacker to gain root/bootloader access to a device that the manufacturer has attempted to lock them out of. Glitching with a 6V supply on a 3.3V bus is certainly something I'd want to be a little cautious of if the hardware was more expensive than a $10 dev board - I wouldn't buy a $800 IoT fridge and use th…

If I'm not mistaken, buying one of a device and tearing it down like this would yield keys that would let you create "official" firmwares for all of the other ones of their kind and set up a fake update site allowing you to remote exploit all of the others, yes? If so this is a fairly serious hack especially for devices that auto-update OTA.

I'm not 100% sure but doesn't each device have its own keys burned at the factory?

So this hack will only work on a single esp32.

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#42

Post by gorgoiler »

Something about e-fuses seems quite mystical. The idea of a computer program deliberately and permanently damaging its own hardware (or hardware it is attached to) using a mechanism so close to regular operation (current flowing in memory) but for a good reason rather than to cause harm, and in such an information rich way.

Different to say a robotic tool using its tooltip to maim itself and different to one robot building another, because at the e-fuse level of detail it’s so much more information sense.

Perhaps it’s like a tattoo? Perhaps I’m thinking of the ship tattoos in Surface Detail by Iain M Banks?

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#43

Post by aspectmin »

Havoc wrote: post #21
MrBuddyCasino wrote: post #7

Props for the effort, but who expects a cheap china MCU for consumer products to be resilient against glitching attacks? You don’t use that stuff in high-security settings anyway. For consumers products resilient to advanced hardware attacks, I can only think of the iPhone and some consoles. Anything else?

>You don’t use that stuff in high-security settings anyway. Forgive my ignorance, but what would one use? i.e. what's the high-sec equivalent of a esp32?

We use these extensively for our higher security needs, yes it's Microsoft, but it's a great product and solves many problems in this space (Updating, security, etc.)

https://azure.microsoft.com/en-us/services/azure-sphere/

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#44

Post by oakwhiz »

gorgoiler wrote: post #42

Something about e-fuses seems quite mystical. The idea of a computer program deliberately and permanently damaging its own hardware (or hardware it is attached to) using a mechanism so close to regular operation (current flowing in memory) but for a good reason rather than to cause harm, and in such an information rich way. Different to say a robotic tool using its tooltip to maim itself and different to one robot bu…

Another way to think of it is, a memory-mapped set of wires that are made too thin, and when read, correspond to ones. If ones are written to that region, they become zeroes every time they are read afterward. This is kind of the reverse of how memory normally works.

Of course the actual mechanism used in OTP memory is different...

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#45

Post by lvturner »

michaelt wrote: post #40
LeifCarrotson wrote: post #6

This is an interesting attack, and certainly looks highly successful in terms of allowing a determined hardware hacker to gain root/bootloader access to a device that the manufacturer has attempted to lock them out of. Glitching with a 6V supply on a 3.3V bus is certainly something I'd want to be a little cautious of if the hardware was more expensive than a $10 dev board - I wouldn't buy a $800 IoT fridge and use th…

> Isn't that a good thing for me as a consumer? I like the ability to decrypt and modify my own devices. If you're the sort of person who buys wifi-based-internet-enabled door bells, but you don't want someone who steals your doorbell to (a) be able to extract your wifi password or (b) be able to get the thing to work at all, you might appreciate resistance to the thief's attacks. Of course, you can also address this…

Or reduce the severity of a breach by using a limited guest network for your IoT devices

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#46

Post by Wowfunhappy »

wildmusings wrote: post #35
jdnenej wrote: post #17

Earlier quoted context omitted.

Almost all computing devices are broken when given physical access. And if they aren't it's just because someone hasn't worked it out yet or is broken secretly by governments.

This is kind of a myth. There is such thing as tamperproof hardware components and they can protect against plenty of threats. Security isn’t all or nothing, it’s about understanding what the different threats are and adequately protecting against them. Not everyone is trying to protect against attackers with millions of dollars at their disposal. There is plenty of value to deterring 99% of attackers with physical a…

I don't disagree with other parts of your post, but I still think protecting against the scenario where an attacker has physical access to your computer is basically pointless. Especially if it comes with a very significant loss of freedom.

If a malicious person has entered your home or workplace, access to your computer should be low on the list of worries.

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#47

Post by pas »

wildmusings wrote: post #35
jdnenej wrote: post #17

Earlier quoted context omitted.

Almost all computing devices are broken when given physical access. And if they aren't it's just because someone hasn't worked it out yet or is broken secretly by governments.

This is kind of a myth. There is such thing as tamperproof hardware components and they can protect against plenty of threats. Security isn’t all or nothing, it’s about understanding what the different threats are and adequately protecting against them. Not everyone is trying to protect against attackers with millions of dollars at their disposal. There is plenty of value to deterring 99% of attackers with physical a…

Yes, but no. I mean you are probably familiar with FIPS-140-2's security levels [0], and the ESP32 is probably on neither. (Not even Level 1. Which is roughly something that you can do almost purely at just in software, that's why OpenSSL has this mode.)

I'd argue that if you want to use some kind of device as part of your security system, and that part has to endure temporary physical access from unauthorized third parties, then you need something that is designed for that. Considering a software broken when it's clearly not designed to withstand physical tampering ... is a bit silly. (Though considering it broken in terms of IP protection is not surprising, it was never really designed for that either.)

Though, of course, you're absolutely correct that compared to its price (or cost), it's a lot more secure than an empty floppy (yet similarly simple - except you can't toggle an efuse with hand), or early smart phones (or early anything, that was complex, ran every kind of software as root, and so naturally was full of holes).

[0] https://en.wikipedia.org/wiki/FIPS_140#Security_levels

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#48

Post by zigzaggy »

lvturner wrote: post #45
michaelt wrote: post #40

Earlier quoted context omitted.

> Isn't that a good thing for me as a consumer? I like the ability to decrypt and modify my own devices. If you're the sort of person who buys wifi-based-internet-enabled door bells, but you don't want someone who steals your doorbell to (a) be able to extract your wifi password or (b) be able to get the thing to work at all, you might appreciate resistance to the thief's attacks. Of course, you can also address this…

Or reduce the severity of a breach by using a limited guest network for your IoT devices

This is how I handle all the IoT devices in my household. It’s one of the first things I implemented after I flashed my router over to DDWRT.

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#49

Post by swiley »

jeremyjh wrote: post #37
jws wrote: post #3

Synopsis: Secret keys are embedded in the device's e-fuses and are not readable by normal means because of a protection e-fuse. By measuring current draw during power up an interval is determined to be the time when the CPU is reading the e-fuses. At that time the power supplies are "glitched" from 3.3v to 6v using unspecified patterns from a signal generator. This causes errors in the e-fuse reading, one of which is…

Just piggy backing on the top comment to point out that the primary concern here is not necessarily for the security of the devices that you own and physically control (although that could be an issue in some cases, if others can access them too), but for the IP of the OEM which can now be extracted and flashed to cloned boards. So this may well be a serious issue for some of Espressif's customers, who are mostly OEM…

In other words, it’s good for users, who’s should have access to the source much less the binary anyway.

Re: Pwn the ESP32 Forever: Flash Encryption and SEC. Boot Keys Extraction

#50

Post by userbinator »

LeifCarrotson wrote: post #6

This is an interesting attack, and certainly looks highly successful in terms of allowing a determined hardware hacker to gain root/bootloader access to a device that the manufacturer has attempted to lock them out of. Glitching with a 6V supply on a 3.3V bus is certainly something I'd want to be a little cautious of if the hardware was more expensive than a $10 dev board - I wouldn't buy a $800 IoT fridge and use th…

This is only bad for draconian IoT manufacturers who want to enforce their terms of service and artificial limitations on hardware they think consumers are leasing but consumers think they are buying.

No kidding. What really grinds my gears is the fact that these authoritarian "security" people are effectively helping to tighten the nooses around everyone else, and very eager to do it too. It's one thing to post about an exploit you've found and help the community, but I'll never agree or help anyone who goes snitching to the company about it. In the "old school" hacking culture you would be called a corporate sellout, or worse, for doing that.

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