this post was submitted on 06 Dec 2023
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Linux

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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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[–] [email protected] 15 points 11 months ago (3 children)

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?

[–] [email protected] 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.

[–] [email protected] 4 points 11 months ago* (last edited 11 months ago) (1 children)

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

[–] [email protected] 3 points 11 months ago (1 children)

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.

[–] [email protected] 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]

[–] [email protected] 4 points 11 months ago (1 children)

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

[–] [email protected] 3 points 11 months ago

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