35
Grub and the Microsoft Ransomware (lemmy.ml)
submitted 9 hours ago by Moonrise2473@lemmy.ml to c/linux@lemmy.ml
27 comments fedilink hide all child comments

TL;DR: bitlocker does not like grub

Full story:

Months ago I installed fedora on my desktop, dual booting Windows 11.

In all this time I never had the need to boot into windows. I remembered that it worked fine after install, good, and then I forgot about that.

Today I needed a specific windows only software, so at grub I chose the microsoft bootloader and... BITLOCKER.

Huh? Bitlocker? Me? What? Searched frantically for that decryption password in my keepass, did not find. What?? How???

After a few minutes staring at that screen I thought, ok let's just wipe that shit and reclaim the space. I went back to linux, opened the partition manager, then remembered that i had something important in single copy over there. Noooooo

Went back to the boot screen to try again, still failed password.

Then I notice the error:

e_fve_pcr_mismatch

that mismatch lets me think that maybe I had something wrong in my booting.

I try to put windows first in the bios and it works! WHAT THE...?!??

So, if i put linux first, then launch windows from grub, bitlocker takes the windows partition under ransom, i can only access if windows is first. And of course in windows 11 x64 is no longer possible add linux partitions in their boot manager (previously it was possible)

Incompetence or maliciousness?

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[-] spaghettiwestern@sh.itjust.works 8 points 4 hours ago

A few years ago I booted up Windows after months of exclusively using Linux. When I ran Windows Update it deleted and overwrote my Linux partition! This wasn't a grub issue, my files were gone and even file recovery utilities couldn't find much. Plenty of others have experienced the same thing.

This is still happening and unquestionably pure maliciousness on Microsoft part.

[-] tea@lemmy.today 22 points 9 hours ago

I have given up dual-booting and just have a Windows VM for work things that require Windows. Less muss, less fuss and I can move the VM around as needed when moving between primary PCs.

[-] Engywuck@lemmy.zip 4 points 8 hours ago

This. And fuck secure boot. Nowadays almost any of can run VMs flawlessly.

[-] wildbus8979@sh.itjust.works 4 points 6 hours ago

You can even use SecureBoot and TPM in a VM ;) OVMF EDK2 fully supports both ;)

SecureBoot is fine, sucks that vendors won't add distro keys but you can do that yourself, or use the shim.

[-] eldavi@lemmy.ml 2 points 8 hours ago

did you have to buy a windows license to do it?

[-] Engywuck@lemmy.zip 12 points 8 hours ago

You may want to Google for a dev called Massgrave.

[-] tea@lemmy.today 2 points 7 hours ago* (last edited 7 hours ago)

My work has licenses I can apply for VMs when I'm keeping them for longer client work, so yes they are licensed in my case.

I wouldn't do that for my own personal use though.

[-] anon5621@lemmy.ml 1 points 7 hours ago

No why pay money for this assholes,more over I use windows server edition which not possible to get if u are not business client and it cost 800$

[-] 9point6@lemmy.world 1 points 8 hours ago

You don't have to

If you only need it for 90 days before it expires, Microsoft will give you the VM for free (and if you're particularly industrious, you might write a script that then installs a load of your shit for you to run after you fire up a fresh one)

If you don't care about potentially breaking the law you can run it forever with a couple of scripts you can find on GitHub

If you don't want to break the law but also don't want to pay full price you can get a dubious but working key from sites like G2A and cdkeys

If that's still too sketchy there's the OEM licenses (honestly not worth it since they can only activate on a single machine ever)

Or finally you might feel sorry for Microsoft for some strange reason and want to go full retail price.

Basically the same experience with all options for a lot of cases, they're just happy to have users it seems

[-] Goretantath@lemmy.world 1 points 8 hours ago

?? Can't you just use Massgravel?

[-] Buffalox@lemmy.world 14 points 9 hours ago* (last edited 9 hours ago)

Microsoft secure boot is 100% made to be a pain in the ass for Linux users. It doesn't add any security, but is instead a huge added unnecessary risk factor for data loss for users.

[-] wildbus8979@sh.itjust.works 5 points 6 hours ago* (last edited 6 hours ago)

I don't know which distro you're using, but in Fedora and Debian it's pretty easy to install the signed version of grub and the signed shime and get full secure boot in Linux. No setup needed.

[-] 9point6@lemmy.world 9 points 8 hours ago

It technically does add security in that it prevents a load of attack vectors that would dodge most anti malware tools (i.e. the ones before the anti malware tool can start)

But you're right in that the execution of the idea is unnecessarily painful for Linux

[-] Buffalox@lemmy.world 2 points 7 hours ago

OK so when did you hear of an actual successful attack that could have been avoided if the user had used secure boot?

[-] 9point6@lemmy.world 6 points 7 hours ago* (last edited 4 hours ago)

Well boot sector viruses used to be all the rage in the 90s, they're entirely impossible under secure boot

Malware rootkits were a pretty big problem about a decade ago, I understand the techniques those mostly used are more or less impossible under secure boot now too

Then we could go into all the government and adjacent industry use cases where state-sponsored targeted attacks are a real concern. Measures like filling USB ports with super glue and desoldering microphones on company laptops is not unheard of in those circles, so blocking unknown bootloaders from executing is an absolute no brainer.

Saying it provides no security is just not true. Your front door isn't only secure if someone has failed to break in

[-] non_burglar@lemmy.world 3 points 6 hours ago

Secure Boot keys are considered compromised.

https://arstechnica.com/security/2024/07/secure-boot-is-completely-compromised-on-200-models-from-5-big-device-makers/

If you are recommending secure boot as a security measure, you should stop doing so.

[-] 9point6@lemmy.world 4 points 6 hours ago

I'm not recommending it, I'm describing why saying it adds no security is silly.

The keys being compromised on some motherboards doesn't mean the whole concept is suddenly inert for every single user

If everyone has a copy of my passwords and authenticator keys, that wouldn't suddenly make 2 factor auth a compromised idea.

Hell, even if you are one of those people running a machine with the compromised keys, it's still going to block malware that was written before the keys were leaked unless malware authors have also figured out time travel.

[-] non_burglar@lemmy.world 1 points 4 hours ago

If everyone has a copy of my passwords and authenticator keys, that wouldn't suddenly make 2 factor auth a compromised idea.

Not sure how this relates. If you're saying it was a good idea at the outset, then sure.... If the keys hadn't almost all been leaked by AMI and Phoenix. MS was supposed to have created a Microsoft Certified hardware vendor program for this, which fell apart pretty quickly.

Secure Boot is a joke, both practically (there are many, many tools in use to bypass it) and in my professional circles, it is considered obsolete like WEP. My audit controls for Secure Boot demand that an endpoint management solution like InTune is deployed.

You don't have to take my word for it, obviously. I'm not trying to tell you how to live your life.

[-] stupid_asshole69@hexbear.net 3 points 7 hours ago

Yeah you gotta disable bitlocker.

[-] M33@lemmy.sdf.org 6 points 9 hours ago

Why not both?

[-] cassandrafatigue@lemmy.dbzer0.com 2 points 7 hours ago

While there is a strong argument for incompetence, generally:

"Windows isn't done until lotus doesn't run"

[-] just_another_person@lemmy.world 3 points 8 hours ago

PCR is the name of a registered value in your TPM module.

Did you disable or otherwise changed your Secure Settings in your BIOS? That would do it.

[-] Static_Rocket@lemmy.world 4 points 7 hours ago

Any changes in the boot process should change various PCR registers. https://wiki.archlinux.org/title/Trusted_Platform_Module#Accessing_PCR_registers

[-] just_another_person@lemmy.world 1 points 6 hours ago

Nah. Specific field registers for specific things, and something like Bitlocker doesn't watch ALL of them.

From the few docs I can find, it looks like 0,2,4, and 11. Pretty common.

[-] Static_Rocket@lemmy.world 3 points 5 hours ago* (last edited 5 hours ago)

I suppose I could have phrased that better. The registers themselves correspond to particular applications/stages, but the values store in those registers should change based on how the application/stage was loaded. Switch the order or inject a new binary and the hash from that stage on should change.

[-] Frederic@beehaw.org 2 points 8 hours ago

I think the first time I installed linux/grub on a repartionned windows drive, my first boot in windows it asked for the bitlocker key, I have it on a USB drive, it's like 30 chars/number. Since then dual booting has always worked. Laptop is win10/linux and desktop is win11/linux.

[-] bastion@feddit.nl 1 points 4 hours ago

distro?

this post was submitted on 09 Dec 2025
35 points (94.9% liked)

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