4 ms·

Hmmm... Can't pam_duress be used to fix https://xkcd.com/538/ https://xkcd.com/538/ ?

by marcodiego 5y ago

mholt 5y ago
No, because if the adversary is convinced you used a duress password, they'll just keep hitting you with a hammer.
- deleted 5y ago
  [deleted]
- emptyparadise 5y ago
  That won't help them if the duress password is used to erase secrets in a way that would prevent even you from unlocking the drive again.
  - 41b696ef1113 5y ago
    Step one for any kind of serious data extraction project would be to make a bit-for-bit duplicate of the origin.
    - emptyparadise 5y ago
      Thankfully a lot of data extraction projects serious enough to beat somebody with a hammer are not serious enough to tamper with TPM.
  - Skunkleton 5y ago
    The downside is they will keep hitting you with that hammer :(
    - emptyparadise 5y ago
      Unfortunately they'd most likely do that even if you could give them the keys :(
  - boring_twenties 5y ago
    That's worthless, they will copy the drive before trying anything.
    - emptyparadise 5y ago
      What if you don't store the keys on the drive?
      - deleted 5y ago
        [deleted]
  - munchler 5y ago
    That scenario only works out in your favor if you prefer severe injury or death over disclosing the secret.
    - emptyparadise 5y ago
      I'm sure that it adds a certain zen aspect to interrogation technique resistance.
- Brian_K_White 5y ago
  There are levels of interest and risk etc. They aren't murdering everyone whos phone / laptop they check at a border. It would be perfectly fine to have an encrypted disk drive that presented different contents based on what password was used to unlock for instance. And with something fully arbitrarily scriptable like this, it doesn't have to simply wipe stuff, it can do practically anything. It could fake having a dead battery, or suffering some kind of crash or other normal annoying service interruption. It could fake a Microsoft account login problem due to some problem with the wifi or borked corporate account control etc. You could increase the believability by pretending to have very common bad security habits like having the duress password written down somewhere on your person or with the machine. If you are a spy and they have you in a hole, then your cover is already blown. They will remove and dissect the storage without even trying to boot it. But things like this could keep you from being noticed in the first place, and could sufficiently handle the vast majority of situations. In Russia right now, they are stopping random people on the street to look for certain telegram groups on people's phones. The randos aren't spies and aren't specifically targeted. The police are really only doing it to scare everyone else away from accepting any communication about Ukraine from outsiders. It would be exactly perfectly good enough if they simply didn't see what they were looking for.
bombcar 5y ago
If they don’t really care, they’re not going to look hard and so most anything would work (hide it in a folder or etc). If they are using the pipe, then anything that isn’t what they’re looking for will result in the pipe.
praptak 5y ago
Determined attacker will have your disk physically copied before attempting anything, so "delete all my files" won't work. For such scenarios plausible deniability is what you want. Ideally, you need a whole parallel system which plausibly appears to attackers as if it is legitimately authorized/decrypted. StegFS is an example building block for such systems. If they know you work on breeding war rabbits, you better have some fake files with records of failed attempts to breed war rabbits and your real files hidden in deeper layers.
- labcomputer 5y ago
  Right, but that’s sort of the reason some OSes like MacOS use a hardware security module to store the key used for encrypting the disk contents. Your adversary can make as many copies of the disk as they want, but they need the HSM (which is, by design, hard to clone) to read the plaintext. An HSM can even enforce policies like rate limiting brute force attempts and/or erasing itself after too many attempts. It could even support a duress password which immediately erases the keys. Without the ability to clone the HSM, the attacker doesn’t get a “second chance” if they attempt to use the duress password.
  - RegnisGnaw 5y ago
    At that point, the attacker will re-aim the wrench at your head instead of your body.
- Retric 5y ago
  Determined attacker might be a mugger trying to get your ATM pin. Assuming they will always have access to the underlying system being protected is missing out on a huge range of security issues.
  - bombcar 5y ago
    ATM is an example where it might match the threat level - a pin that reveals an account with $450 or so in it instead of the real accounts.
- 5y ago
emptyparadise 5y ago
This xkcd comic single-handedly set security threat modeling back by decades.
- TacticalCoder 5y ago
  Yup, honestly it's pathetic and getting on my nerves every single time it's posted.

Hmmm... Can't pam_duress be used to fix https://xkcd.com/538/ https://xkcd.com/538/ ?

mholt 5y ago

No, because if the adversary is convinced you used a duress password, they'll just keep hitting you with a hammer.

deleted 5y ago
[deleted]
emptyparadise 5y ago
That won't help them if the duress password is used to erase secrets in a way that would prevent even you from unlocking the drive again.
- 41b696ef1113 5y ago
  Step one for any kind of serious data extraction project would be to make a bit-for-bit duplicate of the origin.
  - emptyparadise 5y ago
    Thankfully a lot of data extraction projects serious enough to beat somebody with a hammer are not serious enough to tamper with TPM.
- Skunkleton 5y ago
  The downside is they will keep hitting you with that hammer :(
  - emptyparadise 5y ago
    Unfortunately they'd most likely do that even if you could give them the keys :(
- boring_twenties 5y ago
  That's worthless, they will copy the drive before trying anything.
  - emptyparadise 5y ago
    What if you don't store the keys on the drive?
    - deleted 5y ago
      [deleted]
- munchler 5y ago
  That scenario only works out in your favor if you prefer severe injury or death over disclosing the secret.
  - emptyparadise 5y ago
    I'm sure that it adds a certain zen aspect to interrogation technique resistance.
Brian_K_White 5y ago
There are levels of interest and risk etc. They aren't murdering everyone whos phone / laptop they check at a border. It would be perfectly fine to have an encrypted disk drive that presented different contents based on what password was used to unlock for instance. And with something fully arbitrarily scriptable like this, it doesn't have to simply wipe stuff, it can do practically anything. It could fake having a dead battery, or suffering some kind of crash or other normal annoying service interruption. It could fake a Microsoft account login problem due to some problem with the wifi or borked corporate account control etc. You could increase the believability by pretending to have very common bad security habits like having the duress password written down somewhere on your person or with the machine. If you are a spy and they have you in a hole, then your cover is already blown. They will remove and dissect the storage without even trying to boot it. But things like this could keep you from being noticed in the first place, and could sufficiently handle the vast majority of situations. In Russia right now, they are stopping random people on the street to look for certain telegram groups on people's phones. The randos aren't spies and aren't specifically targeted. The police are really only doing it to scare everyone else away from accepting any communication about Ukraine from outsiders. It would be exactly perfectly good enough if they simply didn't see what they were looking for.

bombcar 5y ago

If they don’t really care, they’re not going to look hard and so most anything would work (hide it in a folder or etc). If they are using the pipe, then anything that isn’t what they’re looking for will result in the pipe.

praptak 5y ago

Determined attacker will have your disk physically copied before attempting anything, so "delete all my files" won't work. For such scenarios plausible deniability is what you want. Ideally, you need a whole parallel system which plausibly appears to attackers as if it is legitimately authorized/decrypted. StegFS is an example building block for such systems. If they know you work on breeding war rabbits, you better have some fake files with records of failed attempts to breed war rabbits and your real files hidden in deeper layers.

labcomputer 5y ago
Right, but that’s sort of the reason some OSes like MacOS use a hardware security module to store the key used for encrypting the disk contents. Your adversary can make as many copies of the disk as they want, but they need the HSM (which is, by design, hard to clone) to read the plaintext. An HSM can even enforce policies like rate limiting brute force attempts and/or erasing itself after too many attempts. It could even support a duress password which immediately erases the keys. Without the ability to clone the HSM, the attacker doesn’t get a “second chance” if they attempt to use the duress password.
- RegnisGnaw 5y ago
  At that point, the attacker will re-aim the wrench at your head instead of your body.
Retric 5y ago
Determined attacker might be a mugger trying to get your ATM pin. Assuming they will always have access to the underlying system being protected is missing out on a huge range of security issues.
- bombcar 5y ago
  ATM is an example where it might match the threat level - a pin that reveals an account with $450 or so in it instead of the real accounts.
5y ago

emptyparadise 5y ago

This xkcd comic single-handedly set security threat modeling back by decades.

TacticalCoder 5y ago
Yup, honestly it's pathetic and getting on my nerves every single time it's posted.