this post was submitted on 24 Feb 2024
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If you're having it automatically unlock the drive at boot, it kind of defeats the purpose. If someone steals your tower, they can boot it and copy the unencrypted contents since it automatically unlocks.
OP isn't asking for it to decrypt automatically. OP is asking for the entering the decryption password to also log you in. That way you only have to type the password once, instead of twice.
GDM has an autologin feature, OP should use it.
It depends on where the encryption data is stored. If the bootloader and bios/efi are locked down and the data to unlock is stored in an encrypted enclave or one is using a TPM (and not an external chip one that can be sniffed with a pi), that's a reasonable protection for the OS even if somebody gains physical access.
You could also store the password in the EFI, or on a USB stick etc. It doesn't help you much against longer-term physical access but it can help if somebody just grabs the drive. It's also useful to protect the drive if it's being disposed of as the crypto is tied to other hardware.
Even just encrypting the main OS with the keys in the boot/initrd has benefit, as ensuring that part is well-wiped makes asset disposal safe(r). Some motherboards have an on-board SDCard or USB slot which your can use for the boot partition. It means I don't have to take a drill to my drives before I dispose of them
Bypassing login is not difficult on a lot of OS.
Yeah, but a lot of those things will trip the TPM module, so you will get a different decryption key if you for example try to use the
singlekernel parameter to boot into a root shell. And different decryption key means no access to the data.At least on Windows that requires booting the PC from some other media, and that wouldn't work with the drive encrypted because you have no access to the files you need to modify.
Is it similar with Linux, or do you mean you can actually bypass login from the OS that's already booted up??
It is similar in Linux. Vulnerabilities, bugs, or enough time will get through on any OS so people have to decide on their personal level of paranoia. A lot of people have very little idea how a TPM or sealing key material works.
By intercepting the key on hardware level
Perfect security doesn't exist. If they've got the engineering capital required to design and manufacture key retrieval hardware, you lost the moment they gained physical access to your equipment.
Most brute-force attacks can be hardened against. Again there's no perfect security, just better security.
I agree. Physical access to the device and its often game over.
Sadly reading off the key is already trivial in some cases as showcased in this recent video by stacksmashing
Since the key has to be sent to the cpu in plain text it can easily be sniffed. If however the TPM is integrated in the cpu its not so easy, but then the os can be manipulated or hacked after boot with known exploits.
If you have a long and secure password for you encryption the absolute only way in is to brute force the key which is significantly harder if not impossible regardless of capital
If he uses TPM. I'm not aginst OP using it but he needs to understand the drawbacks. At least I hope he will.
I dont think you can. Can you read SSD storage while that is running? The drive needs to be decrypted using the TPM, and that should only work when its plugged in.