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An attacker with physical access can abruptly restart the device and dump RAM, as analysis of this memory may reveal FVEK keys from recently running Windows instances, compromising data encryption.

The effectiveness of this attack is, however, limited because the data stored in RAM degrades rapidly after the power is cut off.

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[-] BaroqueInMind@lemmy.one 30 points 1 day ago

This exploit requires physical access, and if you have physical access, anything is possible. Secure your shit better.

[-] fmstrat@lemmy.nowsci.com 17 points 1 day ago* (last edited 16 hours ago)

Physical access to a running device, for clarity.

Edit: Unless you use a TPM with no pin/password, which is dumb.

[-] narc0tic_bird@lemm.ee 21 points 1 day ago

It doesn't already have to be running. BitLocker retrieves its keys from TPM by default, so just booting a device will place the keys in memory.

To minimize downtime, abruptly restart the target system during the Windows boot process, specifically before the login screen appears, as this approach has proven effective in scenarios involving the retrieval of Full Volume Encryption Keys (FVEKs).

By kernel-level debugging with WinDbg, the researcher observed BitLocker operations during the Windows boot process, which revealed that while Microsoft attempts to erase encryption keys using functions like SymCryptSessionDestroy, some keys persist on the heap, potentially due to incomplete key destruction mechanisms.

[-] fmstrat@lemmy.nowsci.com 7 points 1 day ago* (last edited 1 day ago)

You're misreading that, I'm afraid. Direct from the researcher:

This can be done in a variety of ways but the goal is to minimize how much time the computer is completely powered off. In my experience I have had the most success restarting the system while Windows is loading but before the login screen has appeared, at least in the case of finding FVEK keys.

"While Windows is loading" ... You must restart after the BitLocker password has been entered and the key is stored in RAM, that's how this exploit works. He had the best luck at that point durong boot, but it could be attempted at any time when RAM is powered and BitLocker is already unlocked. A shutdown or hibernated system is not vulnerable.

[-] narc0tic_bird@lemm.ee 3 points 21 hours ago

A lot of BitLocker setups unlock using just TPM though, which was my point. No password/PIN needs to be entered at boot time to unlock it, it uses the TPM to unlock. This is the default setup that many companies use. Password/PIN unlock is completely optional.

I'm not misreading that.

[-] fmstrat@lemmy.nowsci.com 2 points 16 hours ago

Not the default at any company I've been at. What's the point of encryption if it's unlocked right away? Whoever's doing that deserves this exploit. However, since that's factually correct I'll edit my original comment to add in:

unless you use a TPM with no pin/password, which is dumb

[-] sugar_in_your_tea@sh.itjust.works 3 points 10 hours ago

Exactly.

I don't use BitLocker, but I do use FDE on Linux, and I use a password at the bootloader level. Why would I bother with all the downsides of FDE if it isn't actually secured by a password?

[-] Railcar8095@lemm.ee 1 points 21 hours ago

If the computer doesn't password protection and the attacker has physical access... They can just copy the data, why care about the keys?

I think that's already a worst case scenario.

[-] narc0tic_bird@lemm.ee 2 points 18 hours ago

The user still has to login to their user account. The assumption is that the Windows login is secure so BitLocker can decrypt using TPM and an attacker still won't have access to the data without being able to log in.

This article obviously shows a method how an attacker can potentially still get access to the data without logging in.

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this post was submitted on 06 Jan 2025
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