Full disk encryption protects from somebody yanking a hard drive from running server (actually happens) or stealing a laptop. Calling it useless because it doesn't match your threat model... I hate todays security people, can't threat model for shit.
> Full disk encryption protects from somebody yanking a hard drive from running server (actually happens) or stealing a laptop.
Both of these are super easy to solve without secure boot: The device uses FDE and the key is provided over the network during boot, in the laptop case after the user provides a password. Doing it this way is significantly more secure than using a TPM because the network can stop providing the key as soon as the device is stolen and then the key was never in non-volatile storage anywhere on the device and can't be extracted from a powered off device even with physical access and specialized equipment.
> The device uses FDE and they key is provided over the network during boot, in the laptop case after the user provides a password.
Sounds nice on paper, has issues in practice:
1. no internet (e.g. something like Iran)? Your device is effectively bricked.
2. heavily monitored internet (e.g. China, USA)? It's probably easy enough for the government to snoop your connection metadata and seize the physical server.
3. no security at all against hardware implants / base firmware modification. Secure Boot can cryptographically prove to the OS that your BIOS, your ACPI tables and your bootloader didn't get manipulated.
> no internet (e.g. something like Iran)? Your device is effectively bricked.
If your threat model is Iran and you want the device to boot with no internet then you memorize the long passphrase.
> heavily monitored internet (e.g. China, USA)? It's probably easy enough for the government to snoop your connection metadata and seize the physical server.
The server doesn't have to be in their jurisdiction. It can also use FDE itself and then the key for that is stored offline in an undisclosed location.
> no security at all against hardware implants / base firmware modification. Secure Boot can cryptographically prove to the OS that your BIOS, your ACPI tables and your bootloader didn't get manipulated.
If your BIOS or bootloader is compromised then so is your OS.
Well... they wouldn't be the first ones to black out the Internet either. And I'm not just talking about threats specific to oneself here because that is a much different threat model, but the effects of being collateral damage as well. Say, your country's leader says something that makes the US President cry - who's to say he doesn't order SpaceX to disable Starlink for your country? Or that Russia decides to invade yet another country and disables internet satellites [1]?
And it doesn't have to be politically related either, say that a natural disaster in your area takes out everything smarter than a toaster for days if not weeks [2].
> If your BIOS or bootloader is compromised then so is your OS.
well, that's the point of the TPM design and Secure Boot: that is not true any more. The OS can verify everything being executed prior to its startup back to a trusted root. You'd need 0-day exploits - while these are available including unpatchable hardware issues (iOS checkm8 [3]), they are incredibly rare and expensive.
> Say, your country's leader says something that makes the US President cry - who's to say he doesn't order SpaceX to disable Starlink for your country?
Then you tether to your phone or visit the local library or coffee shop and use the WiFi, or call into the system using an acoustic coupler on an analog phone line or find a radio or build a telegraph or stand on a tall hill and use flag semaphore in your country that has zero cell towers or libraries, because you only have to transfer a few hundred bytes of protocol overhead and 32 bytes of actual data.
At which point you could unlock your laptop, assuming it wasn't already on when you lost internet, but it still wouldn't have internet.
> The OS can verify everything being executed prior to its startup back to a trusted root.
Code that asks for the hashes and verifies them can do that, but that part of your OS was replaced with "return true;" by the attacker's compromised firmware.
That's premised on the attacker never having write access to the encrypted partition, which is the thing storing the FDE key on a remote system or removable media does better than a TPM. If the key is in a TPM and they can extract it using a TPM vulnerability or specialized equipment. Or boot up the system and unlock the partition by running the original signed boot chain, giving the attacker the opportunity to compromise the now-running OS using DMA attacks, cold-boot attacks, etc. Or they can stick it in a drawer without network access to receive updates until someone publishes a relevant vulnerability in the version of the OS that was on it when it was stolen.
Notice that if they can modify/replace the device without you noticing then they can leave you one that displays the same unlock screen as the original but sends any credentials you enter to the attacker. Once they've had physical access to the device you can't trust it. The main advantage of FDE is that they can't read what was on a powered off device they blatantly steal, and then the last thing you want is for the FDE key to be somewhere on the device that they could potentially extract instead of on a remote system or removable media that they don't have access to.
I (the commenter you responded to) am a security engineer by trade and I'm arguing that SB is useful. I'm not sure if the parent commenter is or isn't a security person but my interactions with other people in the security field have given me the impression that most of them think it's good, too.
So I'm a little confused about the "can't threat model for shit part," I think these sorts of attacks are definitely within most security folks threat models, haha
Security professionals wanting to have security solutions they can sell to people doesn't mean that those people actually need or benefit from those solutions. Security professionals tend to vastly overestimate the relevant threat models relevant for regular people and have no concern for anything other than so-called security.
