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MacOS FileVault2 Password Retrieval

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Re: MacOS FileVault2 Password Retrieval

#11

Post by gommm »

teddyh wrote: post #9
nicolas_t wrote: post #6

Earlier quoted context omitted.

> And, of course, once it's woken up and unlocked --- which every attacker who actually challenges FDE can arrange for, all bets are off. I'm not sure what you mean by that? Do you mean that the attacker can force you to wake up and unlock the computer? In that case FDE is not moot anyway, no? For me, the reason I use FDE is in the case I lose or forget my computer somewhere, I do not want the legal liabilities with…

Even though the computer may be “locked”, if the OS is running and accessing the disk, it means that the key is present somewhere in memory. There are various methods of accessing this key, the fallback brute-force method being the ( https://en.wikipedia.org/wiki/Cold_boot_attack ). The method from the article only removes the need to physically remove and cool the memory chips.

Ok, I thought that Apple would scrub all keys from memory when the computer goes to sleep so that a computer that's asleep would not be vulnerable to the Cold Boot Attack. Seems strange they don't do that? Or would it make waking up too slow?

Re: MacOS FileVault2 Password Retrieval

#12

Post by wlesieutre »

nicolas_t wrote: post #3

Has Apple released patches for El Capitan? I'm still using it instead of Sierra because of Karabiner but this could force me to upgrade. That vulnerability seems to be a pretty obvious oversight. I remember hearing about DMA (in the context of Firewire) as an attack vector since people first started talking of Truecrypt and Filevault and scrubbing the memory seems obvious... It's worrying that this could have been ov…

Is Karabiner Elements missing features you need? https://github.com/tekezo/Karabiner-Elements

I haven't tried it because I can't find the wireless mouse that I needed Karabiner for, but my impression was it has most of the functionality running, especially the key/button remapping which seems to be their biggest use case.

Re: MacOS FileVault2 Password Retrieval

#13

Post by mtgx »

tptacek wrote: post #4

Things like this are a reason I unhesitatingly recommend that people stick with their OS's built in FDE: 1. FDE is extremely limited. This particular attack is a clever abuse of sleep/reboot cycles, but of course people intimately familiar with FDE know that if a laptop is sleeping but not shut down it's already perilously close to the boundary at which FDE breaks down. And, of course, once it's woken up and unlocked…

I don't know about Apple but Microsoft has a pretty nasty way of handling user's Bitlocker keys.

If you use a Microsoft account, your key is automatically backed-up in Microsoft's cloud. Red flag #1.

Also, as the recent Bitlocker bypass "bug" showed us, Microsoft has some way of bypassing Bitlocker encryption when it performs updates on the system. I don't know if they have some kind of key escrow or what, but either way - red flag #2.

Of course, I'd say the bigger problem is that Microsoft doesn't even give the majority of Windows users the option to encrypt their computers, by restricting Bitlocker to expensive computers and Windows licenses, while every other operating system does. So the advice to "just use the built-in FDE" doesn't work for the majority of Windows users.

Re: MacOS FileVault2 Password Retrieval

#14

Post by nicolas_t »

wlesieutre wrote: post #12
nicolas_t wrote: post #3

Has Apple released patches for El Capitan? I'm still using it instead of Sierra because of Karabiner but this could force me to upgrade. That vulnerability seems to be a pretty obvious oversight. I remember hearing about DMA (in the context of Firewire) as an attack vector since people first started talking of Truecrypt and Filevault and scrubbing the memory seems obvious... It's worrying that this could have been ov…

Is Karabiner Elements missing features you need? https://github.com/tekezo/Karabiner-Elements I haven't tried it because I can't find the wireless mouse that I needed Karabiner for, but my impression was it has most of the functionality running, especially the key/button remapping which seems to be their biggest use case.

I haven't found a way to configure Karabiner Elements to replace Caps lock with Escape when I only press that key (for vim) and with Ctrl when I press it in combination with other keys (for the terminal).

I also have both Shift keys bound to () when pressed alone and Shift when pressed in combination with other keys.

Re: MacOS FileVault2 Password Retrieval

#15

Post by mweibel »

nicolas_t wrote: post #3

Has Apple released patches for El Capitan? I'm still using it instead of Sierra because of Karabiner but this could force me to upgrade. That vulnerability seems to be a pretty obvious oversight. I remember hearing about DMA (in the context of Firewire) as an attack vector since people first started talking of Truecrypt and Filevault and scrubbing the memory seems obvious... It's worrying that this could have been ov…

If that's the update: https://support.apple.com/en-us/HT207423 then yes.

Re: MacOS FileVault2 Password Retrieval

#16

Post by tptacek »

nicolas_t wrote: post #6
tptacek wrote: post #4

Things like this are a reason I unhesitatingly recommend that people stick with their OS's built in FDE: 1. FDE is extremely limited. This particular attack is a clever abuse of sleep/reboot cycles, but of course people intimately familiar with FDE know that if a laptop is sleeping but not shut down it's already perilously close to the boundary at which FDE breaks down. And, of course, once it's woken up and unlocked…

> And, of course, once it's woken up and unlocked --- which every attacker who actually challenges FDE can arrange for, all bets are off. I'm not sure what you mean by that? Do you mean that the attacker can force you to wake up and unlock the computer? In that case FDE is not moot anyway, no? For me, the reason I use FDE is in the case I lose or forget my computer somewhere, I do not want the legal liabilities with…

Assume that there are generally two kinds of physical attackers:

* Casual, opportunistic attackers who will steal any available laptop.

* Targeted attackers who want your laptop in particular.

Against a casual attacker, even if your laptop is stolen unlocked, it's not going to be carefully kept unlocked. Doing so requires sophistication, care, and extra risk. Instead, the laptop is just going to get wiped.

Against a targeted attacker, like the FBI when they took down Ross Ulbricht (who FDE'd his laptop), the attacker will simply wait until the laptop is unlocked.

Re: MacOS FileVault2 Password Retrieval

#17

Post by eeeeeeeeeeeee »

Although this is an exploit and should be fixed, FDE rarely works if your computer is on / sleeping.

Same thing with the iPhone. Even though it has solid FDE, there have been exploits if the phone is on (even with a passcode, etc).

Turning off your device is the best protection, even if you have FDE.

Re: MacOS FileVault2 Password Retrieval

#18

Post by eeeeeeeeeeeee »

kalleboo wrote: post #8

While I'm not excusing this bug (didn't they already go through this round of DMA bugs with FireWire?), this reinforces my belief that once you have physical access to a personal computer - all bets are off. If you lost your laptop, rotate all keys. Change all passwords. Assume everything is compromised.

There is a huge difference between physical access and the computer being on. That is the first thing this exploit says -- it doesn't work if the computer was turned off previously.

This has always been the way to protect a computer that uses full disk encryption. Turn it off. Sleep mode will not protect you.

Re: MacOS FileVault2 Password Retrieval

#20

Post by mikeash »

gommm wrote: post #11
teddyh wrote: post #9

Earlier quoted context omitted.

Even though the computer may be “locked”, if the OS is running and accessing the disk, it means that the key is present somewhere in memory. There are various methods of accessing this key, the fallback brute-force method being the ( https://en.wikipedia.org/wiki/Cold_boot_attack ). The method from the article only removes the need to physically remove and cool the memory chips.

Ok, I thought that Apple would scrub all keys from memory when the computer goes to sleep so that a computer that's asleep would not be vulnerable to the Cold Boot Attack. Seems strange they don't do that? Or would it make waking up too slow?

Apple wants the computer to be able to wake up on its own in order to fetch new emails and such. Just a few minutes ago, I used Screen Sharing to connect to my sleeping MacBook from another room to check for updates based on this article's recommendation. Quite convenient, but it does imply that the OS keeps the keys around.

I'd bet that if you turn all that stuff off, they keys are scrubbed. That could be a good compromise instead of turning the computer completely off all the time.

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