initrd_luks_pkcs/README.md

initrd_luks_pkcs

Acknowledgment

It has been tested on a debian laptop and a mobian pinephone. The smartcard generation come from inspired by https://github.com/swoopla/smartcard-luks . The OSK-SDL parts are inspired by Mobian package https://salsa.debian.org/DebianOnMobile-team/osk-sdl.

The general steps:

• Erase and initialize card
• Create public/private key pair on smartcard
• Create key file and add it to a LUKS key slot
• Encrypt key file using public key from smartcard
• Modify initramfs to use smartcard to decrypt the encrypted keyfile
• Modify decrypt_opensc script to swicth between smartcard and luks password and add osk-sdl support for touchscreen device

The details:

1. Install smartcard middleware

   sudo apt-get install pcscd opensc

2. Erase smartcard

   pkcs15-init -E

3. Initialize smartcard

   pkcs15-init --create-pkcs15 -p pkcs15+onepin --pin 1234 --puk 4321

4. Create public/private key pair on smartcard

   pkcs15-init -G rsa/2048 -i 01 -a 01 -u decrypt --pin 1234

5. Create a random key file and add it to a LUKS key slot

   sudo touch /root/rootkey

   sudo chmod 600 /root/rootkey

   sudo dd if=/dev/random of=/root/rootkey bs=1 count=245 #change to urandom if you can't wait

   sudo cryptsetup luksAddKey /dev/sda2 /root/rootkey

6. Export the public key from smartcard

   pkcs15-tool --read-public-key 01 -o public_key_rsa2048.pem

7. Encrypt key file using public key

   sudo openssl rsautl -encrypt -pubin -inkey public_key_rsa2048.pem -in /root/rootkey -out /root/rootkey.enc

   sudo rm /root/rootkey

8. Edit crypttab. This change sends the encrypted key file as a param to the keyscript

   This should be of the form:

   mapped_device_name source_block_device key_file luks,keyscript=decrypt_pkcs

   For example:

   sda2_crypt UUID=d332ecc5-ce8b-4900-a04a-a79abd029d6d /root/rootkey.enc luks,keyscript=decrypt_pkcs

9. Install the cryptsetup script and the initramfs-tool hook

   sudo cp decrypt_pkcs /lib/cryptsetup/script/

   sudo cp decrypt_pkcs_hook /etc/initramfs-tools/hooks && chmod +x /etc/initramfs-tools/hooks/decrypt_pkcs_hook

   sudo cp decrypt_pkcs_default /etc/default/decrypt_pkcs

   sudo update-initramfs -u

10. Test smartcard (without USB Key)

11. Test LUKS Password (without Smartcard)