"Evil Thug" goes after Full-Disk Encryption

Dominic White

 

"Evil Thug" goes after Full-Disk Encryption

Boy do I have news for you security people out there; I have a 100% reliable way of breaking all encryption! I call it the "Evil Thug" attack. I provide this service for a small fee. The entry level service will get me or an employee for a hour, this is all it will take to break any encryption in the world (and no we don't need a prostitute, even for 2048bit RSA encryption).

The basic methodology is to approach the encrypted device... and punch the owner in the face until they decrypt the device. The premium service will have this punch-up upgraded to a rubber hosing, and the platinum version will get you some drugs and a $5 wrench. Unlike our competitors, you won't need to involve a notoriously unreliable Latino third-party stereotype.

Okay, jokes aside. Joanna Rutkowska, who has done some hardcore stuff in the past, has done a write-up and released a tool showing how easily the passphrase for a full-disk encryption product can be retrieved by an example person who has access to your physical laptop, even if powered off and without requiring the complexity of coldboot attacks. While she acknowledges that "the concept behind the Evil Maid Attack is neither new, nor l33t in any way" the amount of non-critical coverage it has gotten has irked me.

Her scenario involves someone who not only has access to your laptop without you being around, but has repeat access to your living space, and if they choose, *you*. Of the one squillion options available to a thief at this point, some complicated boot-loader jiggery pokery (not to mention extensions to support other full disk encryption software, AV evasion and the inevitable arms-race/maintenance overhead these things turn into) seems far less viable than beating it out of the victim, or even poisoning their toothpaste and only giving them the antidote once decryption has occurred.

Arguably, actually beating someone exposes you to all sorts of potential law enforcement nastiness, like getting ID'ed in a perp walk. However, if you are going to train an army of maids, *and* have them chain gang laptops out of hotels, you can still get ID'ed by a maid, and you're setting up a fairly big bread trail to your operation by involving that many people, and stealing that much stuff. In short; No, this does not provide you some magic-anti-police ability to scale the theft and is less violent but no more effective than our platinum wrench service.

In future, please don't look to encryption to stop bullets, or pretend that when it doesn't something interesting has happened.

Monday, October 19. 2009
Posted by Dominic White in Security
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#1 Allen Baranov wrote (Link) (Reply)
Posted on Tuesday, October 20. 2009
While I agree that this attack has gathered a lot of geeky following - its because it is technically unique and interesting. Its not just-another-trojan. However, I disagree with your argument. It is almost like the "the world is going to end anyhow, so why bother?" argument. Why lock your windows box when someone can just steal it? Why use a firewall when viruses can come in via web pages? Why worry about "Evil-Maid" when someone can use force? Just because there may be another potentially easier vulnerability to exploit doesn't mean that we should ignore the other vulnerabilities. I wasn't very happy with TrueCrypt's answer to the vulnerability which was something like "sure someone who has access to your box may be able to crack the encryption and if you are truly paranoid then use a safe or physical security." The thing is that full disk encryption has no other purpose but to protect the information on a laptop against physical access by a dedicated intruder with time on his hands. This vulnerability makes full disk encryption a heck of a lot less useful than it was before.
 
#2 Dominic White wrote (Link) (Reply)
Posted on Tuesday, October 20. 2009
(btw, Allen, I like arguing with you, thanks for always commenting) But I never said "we should never do anything about it". If I had gone on to say what we should do about it, and what I hoped I had implied, was that "doing something about this, is a waste of time when you could spend time on more useful defences." We know that physical access get around a whole whack of IT controls, the trick is to use appropriate physical controls. This scenario blurs the lines between the two, but the appropriate response is to not leave your laptop in hotel rooms, or if you do, make sure they're in a safe (my company policy even explicitly states this). I sometimes resort to hiding it when I can't take it with me and the safe isn't big enough though :( A locked case ala the TrueCrypt recommendation is a good one in this case. But it still doesn't defeat the beating scenario. Here 'hidden' partitions can buy you some protection against disclosure, not beatings, if the attacker doesn't have a specific piece of data in mind. To join your point in the beginning and end. This isn't just another trojan. A trojan would be far more successful in retrieving this data because once you're booted and logged in, FDE isn't much use. That's why I don't put much truck in FDE in the first place. See my 'underground fortress' encryption principle /blog/archives/879-The-Towelie-Encryption-Principle.html This stuff should be encrypted higher up the app stack. But, encryption still doesn't stop bullets ;)
 
#3 mh (Reply)
Posted on Friday, October 23. 2009
im not as anti this attack as you seem to be. While i buy that disk encryption never promised to make you coffee and stop bullets, i think joannas attack (and tool) makes a long known theoretical attack tangible, which is sometimes whats needed for it to move into peoples threat models. i can imagine many an intelligence org. which will have no problem breaking into your house/business/car on 2 different days of the week, once for deployment and once for retrieval while the paranoid exec rests peacefully on his "full disk crypto" protection.. shes also not saying it invalidates the use of it.. shes just adding a line to your threat model..
 
#4 Dominic White wrote (Link) (Reply)
Posted on Saturday, October 24. 2009
@mh: A few responses to your few points: * I'm not anti the attack (the research), I'm anti the coverage. I'm not anti Joanna, or calling her dumb. My core point is that you should know this attack is possible and place it on the shelf with several other "physical access" attacks, and make sure your defences take into account the possibility that someone can punch you in the face until you hand over your password. * Her tool does make a long known theoretical attack possible, but given we usually need to assume bad buys have done that, this will only help correct people who had the wrong idea. If anything, my vuln life cycle says that this will make the attack more popular, until vendors do stuff to make it harder. The getting vendors to make this harder is the benefit of her work, which I won't argue with. * As for intelligence orgs, I can imagine them doing all sorts of things. Including drugging you so you forget after they replace your kidney with a GPS tracking device, but it isn't reasonable for your threat model to include this as a regular or likely attack in anything but very rare instances. The use of the "evil maid" analogy was to make it look like this is easy, and the "likelihood" component of the risk is increased, my counter is that given and end-to-end look at the crime it doesn't look like this tool will increase "likelihood" for any other reason that "tool is now freely available". * Full disk crypto has serious flaws. I don't think it should be used at all, because app-level crypto buys you more (but it also buys you more hassle the specifics of the situation matter etc. etc.). If she had said that with everything else the same, I may have been more forgiving. But, getting people with an error in their TM to fix it, is useful I guess, but it wasn't characterised or received as that.
 

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