SecureBoot, yay or nay?

Since moving to a commodity Dell laptop I’ve butted up against a few issues with specific Linux distros and SecureBoot, which was enabled by default on this machine. The big names like Ubuntu and Fedora work with it, but some others like PopOS and openSuSE don’t.

My question then - is SecureBoot a good thing? Bad thing? Something I should turn off immediately and exorcise with proverbial fire? I confess I don’t fully understand what it’s supposed to do in the first place. What problem does it solve?


Nay, if you can get away with it!

The problem which UEFI solves for Microsoft (the inventors of UEFI) seems to be to make life extremely difficult for Linux distro devs and end users to boot any other Operating System than Windows. It’s like 100x more complex than it needs to be, and has been described as a “dumpster fire”, at conferences which are about this sort of thing (Coreboot, Libreboot devs).

A better name for UEFI would have been “LinuxCripple”, or something like that.


I did some digging @FriarDest, I hope this helps,

  • Secure Boot allows you to whitelist which files are permitted to boot

  • It verifies their signature so they won’t boot if they’ve been tampered with.

  • In order for verification to work, all firmware, bootloader and kernel code (including modules) must be trusted or they can circumvent verification.

  • It requires all BIOS firmware updates be signed by the vendor (unless installing from within the BIOS?).

  • “Secure Boot is not an effective DRM mechanism, because you cannot guaranteed that the firmware is telling you the truth. It’s not TPM based, there’s no hardware protections to insure you’ve booted securely.” - Matthew Garret, 2012

  • Turning Secure Boot on or off does not turn off UEFI

What problem does it solve?

This is what I got from what I watched,

If you’re dual booting Windows or booting other untrusted OSs on the same system any one of them can inject malware into your Linux boot files unless Secure Boot is enabled.

This defeats full disk encryption (FDE) as the boot files can’t be encrypted (else they can’t boot). So the next time you use an infected boot, you’ll unlock FDE, the malware gains unlimited access and now knows your key. It can for example edit the kernel in memory and remain near undetectable while listening to key strokes, infecting files and the like.

Without Secure Boot anything you run or install with root / sudo priveleges will be able to infect your boot files or install firmware on your BIOS which allows malware to survive between hard drive swaps and formats to infect future boot files.

While UEFI is very complicated and bloated which increases attack surface, turning off Secure Boot doesn’t turn off UEFI so given the option it seems like a good idea.

There’s some ambiguity to how well it works as related to things like unsigned configs in initd (see: 2nd link) but it does it’s described job relatively well.

If you only boot one OS on the system and your hardware is physically safe it’s not a huge benefit because infection would require root and if malware gets root you’re pretty screwed already. The exception being BIOS malware though that’s relatively rare.

Best of the videos I watched in order of usefulness:

Matthew Garret, Jan 2012
Red Hat Kernel Dev, specializing in power management and firmware development

EFI and Linux: the future is here, and it's awful - Matthew Garrett - YouTube

Matthew Garret, Jan 2018
Security Dev at Google, former Red Hat Kernel Dev

Securing the Linux boot process - YouTube

Daniel Kiper, May 2018
Oracle Dev, GRUB upstream maintainer

UEFI Secure Boot, Shim and Xen — Daniel Kiper, Oracle — Platform Security Summit 2018 - YouTube

UEFI Sponsored Forum, Aug 2018

Webinar: UEFI Firmware Security 101 - YouTube


Nicely put! Thanks for the ‘layman’s take’ style approach. It helped me understand what was ALSO an confusing topic for me as well.

You would be a great talent for writing articles, you know that? Thank you.

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Yes, fantastic answer.

Excellent answer, thank you! I’ll do some watching tonight.

Just a FYI,

If your going to dual boot, Please make sure to put each OS on a separate drive, Your life will be sooooo much easier should a mistake happen or Windows update decide to destroy your MBR. It’s better to install windows first so it can do what it needs to the MBR, Then install Linux so Grub can become the main menu in the MBR and you can then boot to both without issues.

Any other way, and you will then have to edit GRUB manually and that can be a whole lot of work.

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