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Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

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Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#51

Post by brainwad »

naturalmovement wrote: post #27
steve918 wrote: post #23

Earlier quoted context omitted.

I wonder if you think other OSes are any different? TempleOS is the only thing that comes to mind that doesn't fit your description and it's not practically useful. Any sufficiently large codebase is a mix of ideas and concepts implemented by different people with different priorities over a large timespan and if you can fit the entire thing in your head it's not very interesting or complex.

The *BSDs, Mac, and Windows all keep critical code in the same tree as the OS. Something like disk encryption would be immediately visible. So you don't have this mess of 80 different distros with 60 different versions of systemd, 20 that don't use it, a million kernel versions and it's all thrown together in a Costco-sized trash bag and we call the output "Linux".

Windows for ages did not really keep all the code in one repo. There were like a dozen parallel repos for e.g. the shell, kernel, IE, etc. Also every feature was developed on team-level branches; integrating all those branches often caused unexpected bugs.

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#52

Post by briHass »

nacs wrote: post #32
naturalmovement wrote: post #24

Earlier quoted context omitted.

It absolutely is and they have most the enterprise market.

Reminder that by using Bitlocker, you're using a closed source encryption for which Microsoft will happily hand out your recovery key on request. https://www.forbes.com/sites/thomasbrewster/2026/01/22/micro...

Bitlocker can use keys that are local only, but the default for home editions of Windows was to use the online account to back it up.

'Happily' is also a stretch, as they really don't have a choice if served a valid court order.

If you want encryption that is safe from the US government, keys need to be stored in your head. Anything physical is subject to court orders.

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#53

Post by acdha »

nicce wrote: post #40
deng wrote: post #30

> Except that, for more than two years, the encryption key remained resident in memory across suspend, leaving it there for the taking by anyone who seized the still-powered laptop. I don't get it. Obviously, the laptop is locked when it resumes, how is that key "for the taking by anyone"? I'm not saying it is impossible to read out RAM from a locked laptop, but surely not by "anyone".

Anyone with physical access. I think it is understandable from the phrase. There is a common misconception about how lock-screens in general work - they usually just prevents using the current hardware and software as it is to access the current OS. But the disk encryption is the main thing that prevents modification and other kind of access to actual data. And if the disk encryption key is lying in the memory, then…

Anyone with physical access, significant tools, and experience. The FBI has people who can pull data out of memory after freezing the RAM but the average laptop thief doesn’t so how serious this is depends significantly on your threat model. If you’re not a major criminal, bitcoin whale, or intelligence target this is almost certainly academic.

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#54

Post by IngoBlechschmid »

deng wrote: post #42
nicce wrote: post #40

Earlier quoted context omitted.

Anyone with physical access. I think it is understandable from the phrase. There is a common misconception about how lock-screens in general work - they usually just prevents using the current hardware and software as it is to access the current OS. But the disk encryption is the main thing that prevents modification and other kind of access to actual data. And if the disk encryption key is lying in the memory, then…

> Anyone with physical access. I think it is understandable from the phrase. Sorry, I'm probably dense, I still don't get it. You steal a laptop, you open it, the screen is locked with a password/fingerprint whatever. How do you read out the RAM from that laptop?

Several options. One is you restart and boot from a live system where you are root, and then dump all memory. This is described in the paper with the witty title "Lest We Remember: Cold Boot Attacks on Encryption Keys":

https://www.usenix.org/legacy/event/sec08/tech/full_papers/h...

Other options: DMA attacks. Also you never know what the Intel Management Engine hidden in your computer is doing. It's running a version of Minix you don't have any control over, and it has full access to memory.

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#55

Post by john_strinlai »

dijit wrote: post #50
john_strinlai wrote: post #36

Earlier quoted context omitted.

for enterprises, where this doesn't really matter, bitlocker is great.

if by "great" you really mean "fine". It's still brittle, awkward and puzzlingly awful UX despite being the literal standard for the platform. Compare it to any of the actively maintained alternatives, Filevault for MacOS (which is wonderful and never sends your key to be kept somewhere else) or LUKS on Linux.. heck, even Veracrypt is actually easier to understand and more robust.

>if by "great" you really mean "fine".

no, i mean great.

managing a fleet of 100+ laptops with bitlocker is a breeze. its so seemless that the users don't even realize its enabled (i.e. no UX issues, at all).

on the other hand, i am not managing 100+ laptops that use veracrypt. sounds absolutely awful. i've never managed an apple fleet, so i can't speak to that, and will take your word on it.

for personal use, i do not recommend bitlocker (or windows, really), but for already-windows enterprises? absolutely

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#56

Post by deng »

john_strinlai wrote: post #49
deng wrote: post #42

Earlier quoted context omitted.

> Anyone with physical access. I think it is understandable from the phrase. Sorry, I'm probably dense, I still don't get it. You steal a laptop, you open it, the screen is locked with a password/fingerprint whatever. How do you read out the RAM from that laptop?

> How do you read out the RAM from that laptop? the term to look up is "cold boot attack" ( https://en.wikipedia.org/wiki/Cold_boot_attack ). tons of cool live demonstrations of how it works on youtube if you've got the 20-40 minutes to spare

Still, this is a pretty crazy definition of "anyone".

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#57

Post by ksbd-pls-finish »

unethical_ban wrote: post #48
wrs wrote: post #16

Earlier quoted context omitted.

Obviously your distro isn’t using cryptsetup-luksSuspend.

Correct. The point being made is: If one isn't re-entering their passphrase after suspend, how are they surprised that the encryption keys are somewhere in memory during suspend? edit: I see now that the prompt was being given and the keys still resided in memory.

Because debian users with luks-suspend have to re-enter their boot password after sleep.

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#58

Post by dist-epoch »

bitbasher wrote: post #9

I don't see any other way? When you sleep (suspend to RAM), everything is stored in RAM and is encrypted but the master key is present in kernel memory (if I recall correctly). However, if you hibernate (suspend to disk) the entire contents of RAM (including the master key) is written/encrypted to disk and the RAM is cleared. When you wake the machine up you have to re-enter the passphrase to decrypt the master key t…

Both Intel/AMD CPUs produced in the last 5 years or so support full transparent (to the OS) memory encryption. So cold boot attacks are a thing of the past if you enable this feature (it's typically disabled because it reduces RAM speed by about 0.5%).

Re: Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

#59

Post by akerl_ »

john_strinlai wrote: post #55
dijit wrote: post #50

Earlier quoted context omitted.

if by "great" you really mean "fine". It's still brittle, awkward and puzzlingly awful UX despite being the literal standard for the platform. Compare it to any of the actively maintained alternatives, Filevault for MacOS (which is wonderful and never sends your key to be kept somewhere else) or LUKS on Linux.. heck, even Veracrypt is actually easier to understand and more robust.

> if by "great" you really mean "fine". no, i mean great. managing a fleet of 100+ laptops with bitlocker is a breeze. its so seemless that the users don't even realize its enabled (i.e. no UX issues, at all). on the other hand, i am not managing 100+ laptops that use veracrypt. sounds absolutely awful. i've never managed an apple fleet, so i can't speak to that, and will take your word on it. for personal use, i do…

Managing an Apple fleet is similarly fine, and that includes using any of the MDM tooling that also does key escrow on enterprise Filevault devices.
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