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Breaking Bitlocker – Bypassing the Windows Disk Encryption [video]

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

#21

Post by northern-lights »

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?

TPM can always store the (root) private key inside the TPM, but where will the other side of the channel (CPU, HD etc.) store their private key?

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

#22

Post by whyoh »

shawnz wrote: post #13
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, ...).

These kinds of attacks aside, the intent is that you need to turn on the PC and then actually boot to the intended operating system, which is then protected with a login screen

Yeah fair enough. The login screen should still provide good protection in a TPM-only scenario. (Although it had some vulnerabilities in the past: https://secret.club/2021/01/15/bitlocker-bypass.html)

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

#23

Post by FirmwareBurner »

northern-lights wrote: post #20
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.

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 security fluff from Microsoft, Apple, Google can stand against targeted attacks of state actors or knowledgeable motivated well funded actors with freshly acquired zero days.

The security they provide is only good enough against the average thief off the street, which I guess covers 98% of Average Joe's threats.

Even CC security certifications never judge a device whether it's hackable or not, but only on how long it takes for it to be hacked by an accredited lab, because nothing with outside physical access is ever unbackable. With enough time and six figure equipment off the publicly available commercial market, everything reveals its secrets eventually. And that's without zero days off the black market.

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

#24

Post by [deleted] »

dist-epoch wrote: post #9
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…

If you worry about someone sniffing your hardware buses, you should also worry about them intercepting your keyboard connection when you type the TrueCrypt password.

[deleted]

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

#25

Post by H8crilA »

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?

You use a Diffie-Hellman key exchange, signed by a cert stored in the CPU on one side and verified by the TPM on the other. CPUs already have such secret certs inside of them, for example for Intels' SGX.

But as you can read in the article linked by /u/osy, the TPM ecosystem is a victim of design by committee where such things as a threat model are not a thing. They were focused on building a "generic security solution" or some other nonsense, instead of making a threat model, then a protocol, then a verification of the protocol under the threat model - like people did for example with TLS 1.3.

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

#26

Post by shawnz »

ale42 wrote: post #17
shawnz wrote: post #13

Earlier quoted context omitted.

These kinds of attacks aside, the intent is that you need to turn on the PC and then actually boot to the intended operating system, which is then protected with a login screen

Except that if you can sniff the encryption keys, you can tamper with the OS and for example remove the password...

That's why I caveated my explanation with "these kinds of attacks aside": this video describes such a bus sniffing attack

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

#27

Post by p_l »

mike_hock wrote: post #14
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.

I hope this attempt at shoving hardware DRM down our throats tanks just like the last one did.

It's not actually used for DRM, that's part of Intel ME and why AMD PSP is closed source. Both of those are involved in setting up "protected media path" which is all about setting up encrypted channel between display and media player to prevent sniffing.

TPM could be used for DRM in the sense that DRM software could refuse to run on system that isn't approved, but it's not going to stop you from enjoying a DRM free system - in fact it can help by explicitly supporting clearing of TPM state by owner.

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

#28

Post by Arnavion »

dist-epoch wrote: post #8
linarism wrote: post #5

Worth noting that modern AMD CPUs incorporate the TPM functionality in the CPU itself, not sure about Intel.

The most recent AMD CPUs, Zen4 also incorporate Pluton, the TPM designed by Microsoft based on Xbox security experience.

Also given AMD's repeated bungling of the fTPM, Pluton is probably the better option if you must enable one.

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

#29

Post by p_l »

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…

TPM 2.0 provides encrypted sessions specifically to handle this problem.

Of course you need to first use them...

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

#30

Post by briHass »

No big deal here. This attack looks like it's using a crusty old TPM 1.2 laptop, so encrypted parameters to the TPM aren't supported. Even with Win11 and TPM2.0 (required for Win11), encrypted parameters to the TPM would just slow down an attacker.

You need to use pre-boot auth, like a PIN. Obviously, the TPM needs to have some kind of authentication to release the key, not just the default mode where Windows just needs to request it. This is all outlined in MS documentation: https://learn.microsoft.com/en-us/windows/security/operating...

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