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submitted 11 months ago by Chewy7324@discuss.tchncs.de to c/linux@lemmy.ml
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[-] _edge@discuss.tchncs.de 162 points 11 months ago

There are several ways to exploit LogoFAIL. Remote attacks work by first exploiting an unpatched vulnerability in a browser, media player, or other app and using the administrative control gained to replace the legitimate logo image processed early in the boot process with an identical-looking one that exploits a parser flaw. The other way is to gain brief access to a vulnerable device while it’s unlocked and replace the legitimate image file with a malicious one.

In short, the adversary requires elevated access to replace a file on the EFI partition. In this case, you should consider the machine compromised with or without this flaw.

You weren't hoping that Secure Boot saves your ass, were you?

[-] deadcade@lemmy.deadca.de 45 points 11 months ago

Since the EFI partition is unencrypted, physical access would do the trick here too, even with every firmware/software security measure.

[-] _edge@discuss.tchncs.de 23 points 11 months ago

True, but this was the case without this finding, wasn't it? With write access to the EFI you could replace the boot loader and do whatever you please.

[-] deadcade@lemmy.deadca.de 3 points 11 months ago

Unless a proper secure boot + FDE setup is in place.

[-] blindsight@beehaw.org 18 points 11 months ago* (last edited 11 months ago)

The idea is also that a compromised system will remains compromised after all storage drives are removed.

[-] plinky@hexbear.net 18 points 11 months ago

The worst part it persists through reinstalls (if i understood correctly)

[-] _edge@discuss.tchncs.de 11 points 11 months ago

This is also my understanding, at least of you keep the EFI partition.

[-] Bitrot@lemmy.sdf.org 24 points 11 months ago* (last edited 11 months ago)

It can outlast those too.

In many of these cases, however, it’s still possible to run a software tool freely available from the IBV or device vendor website that reflashes the firmware from the OS. To pass security checks, the tool installs the same cryptographically signed UEFI firmware already in use, with only the logo image, which doesn’t require a valid digital signature, changed.

[-] Bipta@kbin.social 10 points 11 months ago
[-] Bitrot@lemmy.sdf.org 12 points 11 months ago

It's reminiscent of boot sector viruses in the DOS days.

[-] InnerScientist@lemmy.world 15 points 11 months ago

replace a file on the EFI partition.

Doesn't this mean that secure boot would save your ass? If you verify that the boot files are signed (secure boot) then you can't boot these modified files or am I missing something?

[-] _edge@discuss.tchncs.de 14 points 11 months ago

Well, not an expert. We learned now that logos are not signed. I'm not sure the boot menu config file is not either. So on a typical linux setup you can inject a command there.

[-] fl42v@lemmy.ml 4 points 11 months ago* (last edited 11 months ago)

If it can execute in ram (as far as I understand, they've been talking about fileless attacks, so... Possible?), it can just inject whatever

Addit: also, sucure boot on most systems, well, sucks, unless you remove m$ keys and flash yours, at least. The thing is, they signed shim and whatever was the alternative chainable bootloader (mako or smth?) effectively rendering the whole thing useless; also there was a grub binary distributed as part of some kaspersky's livecd-s with unlocked config, so, yet again, load whatever tf you want

[-] InnerScientist@lemmy.world 3 points 11 months ago

Last time I enabled secure boot it was with a unified kernel image, there was nothing on the EFI partition that was unsigned.

Idk about the default shim setup but using dracut with uki, rolled keys and luks it'd be secure.

After this you're protected from offline attacks only though, unless you sign the UKI on a different device any program with root could still sign the modified images itself but no one could do an Evil Maid Attack or similar.

[-] fl42v@lemmy.ml 1 points 11 months ago

The point with m$ keys was that you should delete them as they're used to sign stuff that loads literally anything given your maid is insistent enough.

[note: it was mentioned in the arch wiki that sometimes removing m$ keys bricks some (which exactly wasn't mentioned) devices]

[-] hottari@lemmy.ml 4 points 11 months ago

If I can replace a file in your EFI, how hard would it be to sign the same file.

[-] InnerScientist@lemmy.world 3 points 11 months ago

Well, it rules out an evil maid attack and maybe jumping over a dual boot setup.

[-] Ithorian@hexbear.net 11 points 11 months ago

So if I have my computer set that it needs a sudo password for most changes am I good?

[-] _edge@discuss.tchncs.de 14 points 11 months ago

Yes, that's my understanding. A normal user cannot do this. (And of course, an attacker shouldn't not control a local user in the first place.)

Physical access is also a risk, but physical access trumps everything.

[-] Ithorian@hexbear.net 11 points 11 months ago

Thanks for the answer. Unless my dog learns how to code I think I'm safe from anyone getting physical access

[-] PhatInferno@midwest.social 13 points 11 months ago

As a hacker imma start teaching dogs to code as part of my breakin process, sorry bud

[-] Murdoc@sh.itjust.works 5 points 11 months ago

Ah, so the next Air Bud movie will be what, Hack Bud?
"There's nothing in the specifications that says that a dog can't have admin access."
"Nothing but 'net!"

[-] FigMcLargeHuge@sh.itjust.works 5 points 11 months ago

Introduce him or her to FidoNet.

[-] fl42v@lemmy.ml 6 points 11 months ago

Unless they find another way to escalate privileges... A bug, a random binary with suid, etc

[-] peopleproblems@lemmy.world 7 points 11 months ago

See, I knew there were other reasons I wouldn't touch secure boot lol

[-] timicin@lemmygrad.ml 5 points 11 months ago

You weren’t hoping that Secure Boot saves your ass, were you?

i wonder if containerized firefox (eg snap/flatpak) will

[-] falsem@kbin.social 2 points 11 months ago

Yeah, if someone has write access to your boot partition then you're kind of already screwed.

this post was submitted on 06 Dec 2023
354 points (96.3% liked)

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