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Comment by lakeviewterrace | Hacker News Reader

Extraordinary how Linux continues to be 20 years behind Microsoft and Apple when it comes to FDE. This is a hilariously stupid level of complexity for something that should have a universal solution across distros by now.

This is literally a one click process in Windows (plus a couple shell commands to enable TPM+PIN).

I'm not disparaging the author in any way — he's merely documenting the stupidity.

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On both my Fedora laptop and on my MacBook, I have to enter a password at boot to unlock the hard drive, and both had similar complexity to set it up (in Fedora I clicked a button and entered a password during the install, on Mac I clicked a button and wrote down a backup key after the install).

I think this is specifically for the TPM2 integration, which isn’t required for FDE. But I assume it makes it smoother. System updates that requires multiple reboots for example are more annoying on Fedora, since every reboot requires re-entering the password, while on Mac I just login after the final reboot.

FDE without TPM requires the passphrase to have as many bits of security as you want the encryption to have. With a TPM you can have something as short as a PIN, since the TPM can limit the rate at which password attempts are made. I assume most users are satisfied with the weak security implied by a short passphrase, but a dedicated attacker could likely crack it.

FDE uses a key derivation function to limit the rate at which offline password attempts can be made. Not as limited as a TPM can be but not unlimited either and you can adjust it depending on how long you want to wait every time you unlock.

So for example "4" would work ?

Doesn't MS use bitlocker? Or did for a long time, and haven't serious vulns been found in it? If so, I'm not even sure it's a valid comparison. One is real encryption the other is crypto-theater.

Also, isn't the insanity due to MS' influence? They were rumored to do this with influencing the UEFI spec, making Linux less desirable because it was so difficult to dual boot or even single boot UEFI when it came out. This conveniently helped windows hold market share (I'm going back to ballmer Linux=cancer days).

It would stand to reason MS would use their influence to make TPMs insane for end users to manage in Linux but a breeze in windows for the same reason. This is presuming we both agree that MS exerts control over hw manufacturers, I think this is clearly the case.

TPMs aren’t insane to manage in Linux for any technical reason, distros have simply not yet implemented user-friendly tools for automatically managing measured boot.

Has nothing to do with distros. This is you encrypting your disk for the kernel to open during boot. It literally prompts you normally when it hits the step where it attempts to mount the main partition. The way Linux does it is far more flexible and secure because the keys aren't sent to some third party and no one can unlock it without your keys. You are free to use anything to sign the LUKS partition besides a TPM or some silly pin like a Yubikey or whatever the hell you want.

It has EVERYTHING to do with distros.

The process is wholly dependent on bootloaders, systemd versions, and a bunch of other version-specific tooling.

Which none of the distros can ever agree on, so there are 50 variations of implementing disk encryption.

It's all luks2 and kernel negotiation. You use fdisk or similiar to partition and then the kernel mounts it based on the bootloader config.

Literally the only thing distros can do is give you options during install for the partitioning but that is a personal decision for people and it's basically remaking gparted.

please have an llm explain it to you.

What problem is this solving though? The post says they're doing this to avoid typing passphrases. Why would you want the private key hidden in the tpm chip of that device? How will you decrypt if the laptop goes bust or if you move the drive elsewhere?

The TPM generates a strong, non-exportable key in hardware that is far less susceptible to brute-force attacks.

As opposed to accidentally creating your own key of "4", for instance.

A PIN can be used to protect the TPM from unlocking. Even if you set a PIN of "1234" — it would still be far more secure if the disk and laptop were ever to become separated, because the TPM will have generated a strong key anyway.

The TPM is basically a smart card soldered to the motherboard.

> How will you decrypt if the laptop goes bust or if you move the drive elsewhere

Windows and Apple both generate a recovery key as part of the enrollment process which you can store offline.

When you format LUKS you can add multiple decryption keys in case the TPM is hosed for some reason like the mobo failing. Can even use a Yubikey instead of a TPM. Or both. Or none. It's really up to you.

That's a minor convenience to not type passphrases and a fairly high risk of you losing the backup key. Not to mention, the entirely separate problem of storing the backup key securely. It doesn't pass the xkcd "correct horse battery staple" test for me.

All your arguments amount to "i don't understand why smart cards/yubikeys/etc exist when you can just use passwords"

No, yubikey in the fido/webauthn form protects against phishing/TOTP snooping and replay over the web. TPMs for luks don't. See the other thread about evil maid.

Do you not have backups? Why do you need to transplant the SSD to a different laptop to access the data using the backup key?

The SSD is also at risk of dying, so you need the backups anyway.

Fedora uses LUKS where your backup key can just be a regular passphrase. A key derivation function is used internally to help with mitigating brute force attacks.

Fairly sure that if the correct GPOs are set, there is no need for any shell commands needed for a TPM PIN enrollment.

Windows and macOS both can do FDE with good UI/UX compared to Linux.

This is 100% correct, my comment was referring to non-domain joined PCs with no policies set.

I mean, Linux has perfectly good FDE - just the user has to type in their password at boot, no TPM involved.

And it's been possible to get Windows-style self-unlocking FDE for 10+ years, such as by using Ubuntu Core - it just costs a bit, and most users aren't willing to pay $$$ to type one less password.

The design of the TPM makes much more sense for a closed-source operating system, where making it impossible to run a non-microsoft-signed OS protects you against rootkits. Open source OSes don't get that benefit, and the remaining benefits are very minor (and come with big downsides) so I can see why open source developers weren't in a hurry.

> The design of the TPM makes much more sense for a closed-source operating system

I don't think that's the case. The great thing about TPMs is that they measure what's on your system. As long as you modify things properly, your changes get measured and stored in the TPM.

Secure Boot is the more closed-sourced way. By default it relies on Microsoft keys unless you enroll your own and sign your stuff.

Secure Boot also works with Linux, no self-enrolled keys required for poular distros.

TPM measured boot is supported, but it’s a bit fussy to set up using traditional Linux boot, because the firmware, kernel, kernel command line, initrd, grub executable, grub environment, and the complete sequence of grub commands all need to be measured, and some of these things can change for valid reasons other than the obvious case of system updates or reconfiguration (e.g., the Red Hat grub-boot-success mechanism which sets a grub environment variable 2 minutes after a successful boot, so a reboot during or shortly after boot is enough to make measurements taken with this variable set fail).

Also, as in any auto-unlock scenario, the boot process all the way to the login prompt needs to be secured against any interruption that may enable the user to get unauthenticated system access after the disk is unlocked.

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