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Julien Coloos f20941d376 Options to re-enable WOL and start a full shell 6 months ago
src Options to re-enable WOL and start a full shell 6 months ago
ChangeLog Options to re-enable WOL and start a full shell 6 months ago
LICENSE Initial commit 8 years ago
PKGBUILD Options to re-enable WOL and start a full shell 6 months ago
README.md Options to re-enable WOL and start a full shell 6 months ago
initrd-ssh-cryptsetup.install Handle optional ipconfig timeout 7 years ago

README.md

Personal ArchLinux package combining dropbear and cryptsetup in initramfs for unlocking LUKS-encrypted devices either locally (boot console) or remotely over SSH.
The code was reworked from legacy dropbear_initrd_encrypt AUR package.

Installation

After cloning the repo, installation is done as for an AUR package, e.g.:

makepkg -sri

Dropbear

SSH server key need to be generated for dropbear.
Either a new key can be generated with dropbearkey, e.g.:

dropbearkey -t ecdsa -f /etc/dropbear/dropbear_ecdsa_host_key

Or an existing OpenSSH key can be converted with dropbearconvert (useful so that the server fingerprint is the same with both), e.g.:

dropbearconvert openssh dropbear /etc/ssh/ssh_host_ecdsa_key /etc/dropbear/dropbear_ecdsa_host_key

Notes:

  • rsa and ed25519 types are also handled
  • OpenSSH keys must be in PEM format for dropbearconvert to properly work

If necessary an existing key file can be converted to PEM format using ssh-keygen:

ssh-keygen -A -p -m PEM -f /etc/ssh/ssh_host_ecdsa_key

Configuration

As explained upon installation, the following things need to be done:

  • add the authorized SSH public key to /etc/dropbear/initrd.authorized_keys
  • add the ip= kernel command parameter to the bootloader configuration (see https://wiki.archlinux.org/index.php/Mkinitcpio#Using_net)
  • in the HOOKS section of /etc/mkinitcpio.conf, add ssh-cryptsetup before filesystems; then rebuild the initramfs: mkinitcpio -p linux
    • when using a non-standard keyboard layout, it is also useful to add the keymap hook before ssh-cryptsetup, and also move keyboard before keymap

The LUKS-encrypted devices to unlock are derived from /etc/crypttab.

Some options can be set in /etc/initcpio/sshcs_env (file is sourced in initramfs shell):

  • sshcs_opt_debug: whether to be more verbose about ongoing actions
    • default: 0
    • any non-zero value to enable
  • sshcs_opt_net_wol: Wake-on-LAN option to set on network device
    • default: g (MagicPacket™)
    • usually WOL is disabled once in initramfs shell
    • set empty to not change network device WOL setting
  • sshcs_opt_timeout_ipconfig: time (in seconds) to configure IP
    • default: 10
  • sshcs_opt_listen: SSH listening port
    • default: 22
  • sshcs_opt_timeout_poweroff: time (in seconds) to unlock devices before automatic powering off
    • default (and minimum value): 120 (2 minutes)
    • negative value to deactivate
  • sshcs_opt_use_shell: whether to start a full ash shell
    • default: 0
    • 1 to enable
    • when disabled (the default), a script to unlock devices is executed instead

For example:

sshcs_opt_timeout_ipconfig=30
sshcs_opt_listen=2222
sshcs_opt_timeout_poweroff=-1
sshcs_opt_use_shell=1

Building notes

  1. Modify the sources (features in src, and/or package building files)
  2. If src was modified
    • bump pkgver in PKGBUILD
    • archive the src folder in $pkgname-$pkgver.tar.xz file; e.g.: tar -cJf initrd-ssh-cryptsetup-$(grep "^pkgver=" PKGBUILD | cut -d'=' -f2).tar.xz src
    • upload the archive on the online repository (pointed by PKGBUILD)
  3. Update ChangeLog
  4. Update PKGBUILD
    • bump pkgrel if only building files were modified
    • refresh sha256sums with updpkgsums if necessary
      • or manually, based on sha256sum initrd-ssh-cryptsetup-*.tar.xz initrd-ssh-cryptsetup.install output
  5. Delete generated archive file if any