I am trying to create a TPM-based unlock script using tpm2-tools with instructions from Tevora Secure boot tpm2. I have set up the key, loaded it with cryptsetup luksAddKey secret.bin
, then tested it using tpm2_unlock -c 0x81000000 --auth pci:sha1:0,2,3,7
and returns the value of secret.bin. For extra measures, to make sure it works, I loaded secret.bin into "/etc/crypttab", ran # update-initramfs -u -k all
, and rebooted. Upon reboot, the system unlocked.
I copied over the following code into "/etc/initramfs-tools/hooks/tpm2"
#!/bin/sh -e
if [ "$1" = "prereqs" ]; then exit 0; fi
. /usr/share/initramfs-tools/hook-functions
copy_exec /usr/local/bin/tpm2_unseal
copy_exec /usr/local/lib/libtss2-tcti-device.so
I appended my etc/crypttab from cryptname UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx none luks
to cryptname UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx none luks,keyscript=/usr/local/bin/passphrase-from-tpm
I rewrote the following script because the tpm2-tools command was outdated, edited in the new command, and stored it in /usr/local/bin/passphrase-from-tpm:
#!/bin/sh
set -e
echo "Unlocking via TPM" >&2
export TPM2TOOLS_TCTI="device:/dev/tpm0"
/usr/local/bin/tpm2_unseal -c 0x81000000 --auth pcr:sha1:0,2,3,7
if [ $? -eq 0 ]; then
exit
fi
/lib/cryptsetup/askpass "Unlocking the disk fallback $CRYPTTAB_SOURCE ($CRYPTTAB_NAME)\nEnter passphrase: "
I ran # update-initramfs -u -k all
then rebooted. In reboot, I get the following error: /lib/cryptsetup/scripts/passphrase-from-tpm: line 5: /usr/local/bin/tpm2_unseal: not found
I have tried many times to edit passphrase-from-tpm unsuccessfully, including:
- Moving both passphrase-from-tpm into "/boot/efi/EFI/BOOT/" and referencing crypttab to that file
- Modifying passphrase-from-tpm to use a relative file path to tpm_unseal
Before I figured out how to create a backup linux boot using:
objcopy \
--add-section .osrel=/etc/os-release --change-section-vma .osrel=0x20000 \
--add-section .cmdline=cmdline.txt --change-section-vma .cmdline=0x30000 \
--add-section .linux="/boot/vmlinuz" --change-section-vma .linux=0x40000 \
--add-section .initrd="/boot/initrd.img" --change-section-vma .initrd=0x3000000 \
/usr/lib/systemd/boot/efi/linuxx64.efi.stub /boot/EFI/BOOT/BOOT_RECX64.EFI
I would be locked out of the system completely because of the error and had to reinstall Ubuntu about 40 times. I have suffered a lot and want to quit but I am too stubborn to throw in the flag.