this post was submitted on 24 Feb 2024
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Encrypted hard drive asking for password every time (lemy.lol)
submitted 8 months ago* (last edited 8 months ago) by [email protected] to c/[email protected]
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I recently switched to Linux (Zorin OS) and I selected "use ZFS and encrypt" during installation. Now before I can log in it asks me "please unlock disk keystore-rpool" and I have to type in the encryption password it before I'm able to get to the login screen.

Is there a way to do this automatically like with Windows or MacOS? Zorin has biometric login which is nice but this defeats the purpose especially because the encryption password is long and tedious to type in.

Also might TPM have anything to do with this?

EDIT: Based on the responses I have to assume some of you guys live in windowless underground bunkers sealed off with concrete because door locks "aren't secure against battering rams". Normal people don't need perfect encryption they just want to add an extra hurdle or two for the crackhead who steals the PC. I assumed Linux had a system similar to what Windows or MacOS has been doing for a decade but I am apparently wrong.

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[–] [email protected] 16 points 8 months ago (2 children)

Assuming you want:

  1. Single password prompt instead of auto-decrypt with tpm
  2. User's files to be encrypted

There are several ways to achieve this:

  1. autologin (recommended for single user system): / is encrypted using luks or zfs native encryption and user's home needs to be unencrypted. User's password may be same as encryption password for convenience, though they still are two passwords used for different purposes.

  2. pam mount: / is unencrypted or auto-decrypted and user's home is encrypted independently from / using zfs,luks,fscrypt,etc. In this case, user's login password must be same as user's home encryption password. It's suitable for multi-user system. NOTE: It cannot be used with autologin since user's home needs to be decrypted to log in.

WARNING: For tpm usage, using secure boot is highly recommended to prevent unauthorized user from accessing key stored in tpm.

To prevent auto-decrypt with tpm, tpm-pin can be used (with autologin for requirement #1).

  1. systemd-cryptenroll with/without tpm: As far as I know it can be only used to unlock disk encrypted with luks2. It can be used without tpm with pkcs11-token (e.g. YubiKey) or fido2-device. It also uses parameter encryption while key is unsealed, so safe from key sniffing via communication bus. This is easy if secure boot is enabled and luks2 is used for encryption.

  2. clevis with tpm: It can be used in place of systemd-cryptenroll. May be used with zfs native encryption. Though I'm not sure if it uses parameter encryption (correct me).

  3. unencrypted keyfile on usb: Not sure about zfs, but you can use keyfile on a usb drive to decrypt luks containers.

NOTE: I'm not a forensic/security expert. I listed a brief overview of methods I could think of to keep user's files encrypted while providing single password till login.

[–] [email protected] 4 points 8 months ago (1 children)

Auto decrypt with TPM sounds fine to me but I have no idea what TPM is as this is my first PC with it.

Thanks for the great response though I'll look into these

[–] [email protected] 6 points 8 months ago* (last edited 8 months ago)

I have no idea what TPM is

Read Skull giver's reply or look it up.

Re-reading your post, I take you want to avoid typing long and tedious password? And that's why you want to auto-decrypt?

  1. (Recommended) You could use strong memorable passwords that are not difficult to type and enable autologin. Related xfcd comic:

  1. systemd-cryptenroll: For TPM usage, I highly recommend using secure boot. Though not sure if you can easily do that. A less secure alternative using systemd-cryptenroll would be use tpm2-pin and bind key to no pcrs (discouraged). But then you'll have to use luks2 for encryption. Notice from man systemd-cryptenroll regarding tpm2-pin:

Note that incorrect PIN entry when unlocking increments the TPM dictionary attack lockout mechanism, and may lock out users for a prolonged time, depending on its configuration. The lockout mechanism is a global property of the TPM, systemd-cryptenroll does not control or configure the lockout mechanism. You may use tpm2-tss tools to inspect or configure the dictionary attack lockout, with tpm2_getcap(1) and tpm2_dictionarylockout(1) commands, respectively Also tpm2-pin is not disk encryption password and short alphanumeric password needed so tpm decrypts the device; so encryption password should be secured in a safe place. Also check if your distro supports systemd-cryptenroll.

  1. usb drive: read previous comment

  2. clevis: It probably isn't as simple as systemd-cryptenroll but I guess you can use zfs and combine that with tpm2-pin if not using secure boot (discouraged).

You'll have to make a compromise somewhere between security and convenience. Even if you use pam mount, you'll have to enter the password, biometrics won't do.

Edit: remove unnecessary user tag and add img uri

[–] [email protected] 2 points 8 months ago (1 children)

systemd-homed can also do it.

[–] [email protected] 1 points 8 months ago

oh, I forgot. Thanks for mentioning that :)