Re: [ISSUE] [CLOSED] Decrypting key for luks root partition fails with recent kernel/dracut

[mithodin <mithodin@users.noreply.github.com>]

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Closed issue by mithodin on void-packages repository

https://github.com/void-linux/void-packages/issues/40703

Description:
### Is this a new report?

Yes

### System Info

Void 5.19.10_1 x86_64 GenuineIntel uptodate rrFFFFFFFF

### Package(s) Affected

linux-6.0_1, dracut-053_5, gnupg-2.3.8_1

### Does a report exist for this bug with the project's home (upstream) and/or another distro?

_No response_

### Expected behaviour

gnupg is used at boot time to decrypt a key that is configured via the grub commandline with rd.luks.key to decrypt my root filesystem.

### Actual behaviour

The root filesystem fails to decrypt because the key file fails to decrypt.

### Steps to reproduce

1. Create a small partition holding a gpg-encrypted key file "root.key.gpg" for the root drive, which is luks encrypted
2. Put the private key capable of decrypting this key onto a yubikey.
3. Configure dracut to use this key at boot time via the grub commandline rd.luks.key=/root.key.gpg:UUID=<root fs UUID>
4. Add add_dracutmodules+=" crypt-gpg " to /etc/dracut.conf
5. Boot the computer with the yubikey plugged in

I have an initramfs with linux-5.19.10_1 where the process works fine. It used to work fine for many kernel versions, in fact. But starting with linux-5.19.15, the decryption fails. The root cause seems to be that gpg fails to decrypt the key file. On the rescue shell, I have confirmed that
 - gpg is able to access the yubikey (gpg --card-status lists it and gpg --edit-card shows the properties correctly)
 - gpg fails to decrypt the key file, giving only the message "unexpected error". Adding --verbose yields no additional information.

I'm at a loss where to go from here. I'm not even sure which of the involved components introduced the failure.