Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

youtube.com

Post reply on HN
Print view View original

31–40 of 74 posts

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#31

Post by p_l »

matsz wrote: post #3

This is particularly interesting considering that TrueCrypt recommended migration to BitLocker as the main option for Windows: https://truecrypt.sourceforge.net/ IIRC Apple's version of TPM (Secure Enclave) should be immune to such attacks (since it's on the SoC, but I'm not sure whether the communication is encrypted or not), and the main data encryption method for GNU/Linux (LUKS) does not utilize TPM by default (m…

TPM 2.0 supports encrypted sessions, which block this kind of attack (TPM 2.0 is wholly different beast than TPM 1.x series).

I do not recall if cryptsetup's TPM2 support sets up encrypted session, but for BitLocker just setting it to require PIN breaks this attack (the PIN is used as part of TPM policy preventing automatic decryption).

Additionally, some laptops at the very least attempt to erase TPM on case open.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#32

Post by p_l »

jsmith99 wrote: post #7

Nothing new. This attack is demonstrated here many times and the Microsoft docs discuss a similar attack using self encrypting drives. The counter measure is to use a virtual TPM built into the CPU or to use TPM+PIN (which is standard practice for security).

Another piece is to use encrypted session where the traffic between OS and TPM is encrypted as well.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#33

Post by p_l »

bugbuddy wrote: post #4

I predict that this will necessitate an upgrade to TPM 3.0 with a key exchange handshake mitigation along with it being a requirement to upgrade to Windows 12. That’s fine though because it will help with economic growth and all the relevant companies’ bottom lines.

TPM2 already has encrypted session support which does exactly that.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#34

Post by Terr_ »

FirmwareBurner wrote: post #23
northern-lights wrote: post #20

Earlier quoted context omitted.

There is nothing that is safe against physical attacks practically. You can always find a point where you can do a MITM attack as the communication channels between the TPM and anything else is almost always insecure.

>There is nothing that is safe against physical attacks practically. This! If security is your prime directive in your line of work(government, highly sensitive data, etc), then as long as your device has been outside your physical possession and in the hands of an untrusted third party, then it's automatically considered compromised and gets wiped or discarded by your IT department. Because no amount of marketing se…

Also, physical security is sometimes the best thing because it maps well to all of our human intuitions and senses for enforcing it and detecting when it was violated.

Consider how different a wireless hacking attack is from one where somebody has to sneak up and stab your device with an RJ-45 plug.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#35

Post by briHass »

ghostpepper wrote: post #15
aquova wrote: post #2

Very interesting video. For those who can't watch, he creates a PCB with a RPi Pico and some data pins which can sniff the BitLocker key as it's sent from the TPM chip back to the CPU. I was surprised to see that this was sent in plaintext, so although his board probably will only work for that particular motherboard, the method would be sound for other computers as well. I'll leave the comments about MS requiring TP…

It's a bit of a chicken-egg problem when the TPM is the root of trust for the entire system. Sure you can encrypt the data on the bus, but where do you store that key?

Exactly. An attacker that has full access to the device can get past encrypted TPM parameters, it would just slow them down. The best method is pre-boot auth where the TPM itself requires a PIN to release the keys. Windows doesn't use that by default, but it can be enabled.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#36

Post by Arnavion »

mjg59 wrote: post #18
osy wrote: post #10

TPM is insecure against physical attacks by design: https://gist.github.com/osy/45e612345376a65c56d0678834535166 The only secure implementation is called D-RTM which requires a level of chip, OEM, and OS support that's not done in practice.

Not really? Encrypted sessions block the trivial attack of just watching the secret go across the bus. Pushing people to MITM attacks is already an improvement, and while generating initial trust in the TPM for that purpose isn't straightforward, it's not impossible. The almost universal implementation of TPM-backed secret management isn't secure against physical attack, but that's very different to "insecure by desi…

>All the primitives to make this work reasonably are there, OS and firmware vendors just aren't using them.

To be precise, both Windows (according to the article) and Linux+systemd (since systemd v251) support letting the user specify a TPM PIN and then use parameter encryption. But yes, both make it optional.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#38

Post by mjg59 »

jpalomaki wrote: post #37

Does Microsoft Pluton [1] help here? I noticed at least some recent ThinkPad AMD models support it. [1] https://learn.microsoft.com/en-us/windows/security/hardware-...

Yes, it does, as does using any other CPU or chipset based TPM (Intel PTT, the AMD PSP-based TPM, running in Trustzone on ARM). The non-Pluton approaches potentially have greater overall attack surface, so Pluton is probably the best choice if available.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#39

Post by jeroenhd »

p_l wrote: post #31
matsz wrote: post #3

This is particularly interesting considering that TrueCrypt recommended migration to BitLocker as the main option for Windows: https://truecrypt.sourceforge.net/ IIRC Apple's version of TPM (Secure Enclave) should be immune to such attacks (since it's on the SoC, but I'm not sure whether the communication is encrypted or not), and the main data encryption method for GNU/Linux (LUKS) does not utilize TPM by default (m…

TPM 2.0 supports encrypted sessions, which block this kind of attack (TPM 2.0 is wholly different beast than TPM 1.x series). I do not recall if cryptsetup's TPM2 support sets up encrypted session, but for BitLocker just setting it to require PIN breaks this attack (the PIN is used as part of TPM policy preventing automatic decryption). Additionally, some laptops at the very least attempt to erase TPM on case open.

I think the "on case open" bypass was shown quite well in this video (the picture of the Surface device with a hole drilled in the back).

Such measures should protect against backdooring attempts (by the visible physical damage to the case) but they won't prevent an attacker from reading the secret key.

Re: Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

#40

Post by jeroenhd »

whyoh wrote: post #12

To decrypt a drive with a TPM-only key you just need to turn on the PC . So what's the big deal here? It's disappointing that TPM-only is the default for Bitlocker, but you can just use something else (pin/password, key file, ...).

I think TPM-only encryption is still good enough for cases where a thief may try to swipe the hard drive out to steal the information on it later.

Plus, in a business where laptops may get reused, it could be a method to make an old Windows install inaccessible by wiping the backup key from the cloud and clearing the TPM on the device without any formatting. You may want to do a quick format to be sure (you never know if someone kept their private files in the EFI partition) but it'll protect you against data recovery risks from reassigned sectors without having to force everyone to enter a password twice every time they boot their laptop.

Post reply on HN