4 ms·

The “tamper with product, then return product to e-commerce site” is an interesting attack vector. It seems impractical for any platform to defend against such

The “tamper with product, then return product to e-commerce site” is an interesting attack vector. It seems impractical for any platform to defend against such an attack, short of recycling returned products instead of reselling them. Has anyone written more about this from the defender’s perspective?

freedomben 3y ago
For software, I don't think it's all that impractical. You could cryptographically verify that the factory firmware is signed and valid, and if it isn't then you re-flash it before reselling. This should be (and often is) a standard practice for "refurbished" goods. Even at a small scale you should already have the means of verifying the software/firmware loaded on the device because you don't want to ship a broken product. Using that to verify should generally speaking be fairly easy to do. For hardware it does get a little more difficult, but if the attacker isn't allowed to run their own (modified) version of the firmware/software, then such attacks are very, very difficult to do. You would want to design your product in such a way that you can check the storage/flash contents without having to trust the product to self-report, otherwise a modified software build could easily lie to the verifier about it's hash. So for most use cases, both hardware and software are mitigated substantially by verifying the software build. An important note here is that it doesn't need to require distrusting the user. Of course modern tech companies love to distrust the user because it gives them substantially more control over how their product is used, so the "security" justification of using anti-tamper technologies is highly attractive to them.
dzaima 3y ago
I don't really see that being a feasible attack vector for any attacker - you can't really control who's gonna buy the tampered-with thing, so it can't be a targeted attack (unless the buyers are all high-value victims, in which case, don't resell; otherwise, add a random delay on reselling), and it's gonna be much more expensive than alternative methods for a non-targeted attack.
- michaelt 3y ago
  I always thought this would be a good attack vector for hardware bitcoin wallets. You make a subtly backdoored version (for example, tamper with the RNG so it only has a few bits of entropy) and you either return it, or sign up as a third-party seller and ship it to Amazon yourself, to be commingled with existing legitimate inventory. Then a year or two later, because you know all but a few bits of the private key, you grab the money and run. No need to control who gets the backdoored devices, just ship enough that you luck into some rich buyers.
  - dzaima 3y ago
    I dearly hope that there isn't much reselling of hardware keys/wallets going on, that's indeed a nice and simple recipe for disasters.

freedomben 3y ago

For software, I don't think it's all that impractical. You could cryptographically verify that the factory firmware is signed and valid, and if it isn't then you re-flash it before reselling. This should be (and often is) a standard practice for "refurbished" goods. Even at a small scale you should already have the means of verifying the software/firmware loaded on the device because you don't want to ship a broken product. Using that to verify should generally speaking be fairly easy to do. For hardware it does get a little more difficult, but if the attacker isn't allowed to run their own (modified) version of the firmware/software, then such attacks are very, very difficult to do. You would want to design your product in such a way that you can check the storage/flash contents without having to trust the product to self-report, otherwise a modified software build could easily lie to the verifier about it's hash. So for most use cases, both hardware and software are mitigated substantially by verifying the software build. An important note here is that it doesn't need to require distrusting the user. Of course modern tech companies love to distrust the user because it gives them substantially more control over how their product is used, so the "security" justification of using anti-tamper technologies is highly attractive to them.

dzaima 3y ago

I don't really see that being a feasible attack vector for any attacker - you can't really control who's gonna buy the tampered-with thing, so it can't be a targeted attack (unless the buyers are all high-value victims, in which case, don't resell; otherwise, add a random delay on reselling), and it's gonna be much more expensive than alternative methods for a non-targeted attack.

michaelt 3y ago
I always thought this would be a good attack vector for hardware bitcoin wallets. You make a subtly backdoored version (for example, tamper with the RNG so it only has a few bits of entropy) and you either return it, or sign up as a third-party seller and ship it to Amazon yourself, to be commingled with existing legitimate inventory. Then a year or two later, because you know all but a few bits of the private key, you grab the money and run. No need to control who gets the backdoored devices, just ship enough that you luck into some rich buyers.
- dzaima 3y ago
  I dearly hope that there isn't much reselling of hardware keys/wallets going on, that's indeed a nice and simple recipe for disasters.