Add support for labels for the rd.luks option

[MorningLightMountain713]

Describe the enhancement

Add option for rd.luks.label=<label>

First off - maybe there is a much easier way to do what I'm doing, but I can't see it.

I'm using dracut to build a NON hostonly initrd. This initrd is part of a signed UKI that I distribute, so to make it portable, I'm using labels on the crypt block device. (and in fstab)

Since I can't specify the label as a kernel option, I have to resort to using crypttab, but that only works for hostonly.

The hack I'm using to get around this at the moment is the following in 90crypt/module-setup.sh:

(remove hostonly check and add label match)

    if [[ -f $dracutsysrootdir/etc/crypttab ]]; then
        # filter /etc/crypttab for the devices we need
        while read -r _mapper _dev _luksfile _luksoptions || [ -n "$_mapper" ]; do
            [[ $_mapper == \#* ]] && continue
            [[ $_dev ]] || continue

            [[ $_dev == PARTUUID=* ]] &&
                _dev="/dev/disk/by-partuuid/${_dev#PARTUUID=}"

            [[ $_dev == UUID=* ]] &&
                _dev="/dev/disk/by-uuid/${_dev#UUID=}"

            [[ $_dev == ID=* ]] &&
                _dev="/dev/disk/by-id/${_dev#ID=}"

            [[ $_dev == LABEL=* ]] &&
                _dev="/dev/disk/by-label/${_dev#LABEL=}"

            echo "$_dev $(blkid "$_dev" -s UUID -o value)" >>"${initdir}/etc/block_uuid.map"

I also have to add a udev rule as /usr/lib/udev/rules.d/60-persistent-storage-dm.rules does not add the disk by label for some reason.

Here is missing cryto for disk by label:

ENV{ID_FS_USAGE}=="filesystem|other|crypto", ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-uuid/$env{ID_FS_UUID_ENC}"
ENV{ID_FS_USAGE}=="filesystem|other", ENV{ID_FS_LABEL_ENC}=="?*", SYMLINK+="disk/by-label/$env{ID_FS_LABEL_ENC}"

Here is /etc/udev/rules.d/99-add-label.rules, my added udev rule:

ATTR{dm/name}=="vg_1-lvm_system", SYMLINK+="disk/by-label/os_luks"

and finally, here is the crypttab:

os_crypt  LABEL=os_luks  none    try-empty-password=1,luks,tpm2-device=auto,discard,force

This all works, but it's super hack and I would much prefer to be able to just pass a label as a kernel option, as I don't know what the uuid will be at build time.

Thanks