Example to convert existing OpenSSH key to PEM format

v0.8-1

ChangeLog

@@ -1,3 +1,21 @@
+2021-08-15 Julien Coloos <julien.coloos [at] gmail [dot] com>
+
+        * v0.8-1
+        Include 'libgcc_s.so.1' which is necessary for (at least) proper LUKS v2 handling
+
+
+2020-07-14 Julien Coloos <julien.coloos [at] gmail [dot] com>
+
+        * v0.7-1
+        Dropped 'dsa' private key support; added 'ed25519' private key support
+
+
+2018-03-13 Julien Coloos <julien.coloos [at] gmail [dot] com>
+
+        * v0.6-1
+        Dropped '-m' option when calling dropbear (latest ArchLinux version does not handle it)
+
+
 2017-06-25 Julien Coloos <julien.coloos [at] gmail [dot] com>
 
         * v0.5-1

PKGBUILD

@@ -1,6 +1,6 @@
 # Maintainer: Julien Coloos <julien.coloos [at] gmail [dot] com>
 pkgname=initrd-ssh-cryptsetup
-pkgver=0.5
+pkgver=0.8
 pkgrel=1
 pkgdesc="Allows for LUKS-encrypted devices to be unlocked remotely over SSH"
 arch=('any')
@@ -10,7 +10,7 @@ depends=('dropbear' 'cryptsetup' 'mkinitcpio-nfs-utils' 'iproute2')
 install=$pkgname.install
 changelog='ChangeLog'
 source=("http://julien.coloos.free.fr/archlinux/$pkgname-$pkgver.tar.xz" "$pkgname.install")
-md5sums=('d87a35adbef55db89f32a89f4966a27a'
+md5sums=('ac5a53fbc288ccce61874488bcbbf58a'
          'ac60109d80e7bb2af0d66e69aaf178a6')
 
 package() {

README.md

@@ -1,16 +1,37 @@
 Personal ArchLinux package combining dropbear and cryptsetup in initrd for unlocking LUKS-encrypted devices either locally (boot console) or remotely over SSH.  
-The code was reworked from [dropbear_initrd_encrypt](https://aur.archlinux.org/packages/dropbear_initrd_encrypt/).
+The code was reworked from legacy dropbear_initrd_encrypt AUR package.
 
 
 ## Installation
-After cloning the repo, installation is done as for an AUR package.
+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 SSH public key to `/etc/dropbear/initrd.authorized_keys`
+   * 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)
+      - e.g. with `grub`: add `ip=:::::eth0:dhcp` to `GRUB_CMDLINE_LINUX_DEFAULT` in `/etc/default/grub`, and re-generate the configuration with `grub-mkconfig -o /boot/grub/grub.cfg`
    * 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`.
 
@@ -37,9 +58,10 @@ For example:
 ## Building notes
 1. Modify the sources (features in `src`, and/or package building files)
 2. If `src` was modified
-   * archive the `src` folder in `$pkgname-$pkgver.tar.xz` file; e.g.: `tar -cJf initrd-ssh-cryptsetup-0.4.tar.xz src`
+   * archive the `src` folder in `$pkgname-$pkgver.tar.xz` file; e.g.: `tar -cJf initrd-ssh-cryptsetup-0.7.tar.xz src`
    * upload the archive on the online repository (pointed by `PKGBUILD`)
-3. Update `PKGBUILD`
+3. Update ChangeLog
+4. Update `PKGBUILD`
    * bump `pkgver` if `src` was modified, or `pkgrel` if building files were modified
    * refresh `md5sums` if necessary (based on `md5sum initrd-ssh-cryptsetup-*.tar.xz initrd-ssh-cryptsetup.install` output)
-4. Delete generated archive file if any
+5. Delete generated archive file if any

src/hooks/ssh-cryptsetup

@@ -163,7 +163,7 @@ EOF
     touch "/var/log/lastlog"
 
     msg "Starting dropbear ..."
-    dropbear -Emsgjk -P "${path_dropbear_pid}" ${sshcs_opt_listen}
+    dropbear -Esgjk -P "${path_dropbear_pid}" ${sshcs_opt_listen}
 
     # Actual unlocking
     sshcs_unlock

src/install/ssh-cryptsetup

@@ -32,7 +32,7 @@ build() {
     local etc_crypttab="/etc/crypttab"
     local dropbear_authorized_keys="/etc/dropbear/initrd.authorized_keys"
     local sshcs_env="/etc/initcpio/sshcs_env"
-    local dropbear_key_types=( "dss" "rsa" "ecdsa" )
+    local dropbear_key_types=( "rsa" "ecdsa" "ed25519" )
     local dropbear_keyfile_prefix="/etc/dropbear/dropbear_"
     local dropbear_keyfile_suffix="_host_key"
     local openssh_keyfile_prefix="/etc/ssh/ssh_host_"
@@ -53,6 +53,9 @@ build() {
     sshcs_check_keys
 
     add_checked_modules "/drivers/net/"
+    # Note: parts of this script (modules/binaries added) are the same than the
+    # 'encrypt' install script (/usr/lib/initcpio/install/encrypt) which is the
+    # nominal one to deal with encrypted volumes at boot time.
     add_module dm-crypt
     # Note: crypto modules are necessary
     if [ -n "${CRYPTO_MODULES}" ]; then
@@ -79,9 +82,9 @@ build() {
 
     # SSH-related files
     add_file "${dropbear_authorized_keys}" "/root/.ssh/authorized_keys"
-    add_file "/etc/dropbear/dropbear_rsa_host_key"
-    add_file "/etc/dropbear/dropbear_dss_host_key"
-    add_file "/etc/dropbear/dropbear_ecdsa_host_key"
+    for keytype in "${dropbear_key_types[@]}"; do
+        add_file "${dropbear_keyfile_prefix}${keytype}${dropbear_keyfile_suffix}"
+    done
 
     # cryptsetup-related files
     add_file "${etc_crypttab}"
@@ -90,6 +93,11 @@ build() {
     add_file "/usr/lib/udev/rules.d/95-dm-notify.rules"
     add_file "/usr/lib/initcpio/udev/11-dm-initramfs.rules" "/usr/lib/udev/rules.d/11-dm-initramfs.rules"
 
+    # At least with LUKS v2 volumes, cryptsetup calls pthread_cancel(), which
+    # dlopen()s libgcc_s.so.1.
+    # See the nominal 'encrypt' module, and similar/related bug reports (e.g.
+    # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=950254).
+    add_binary "/usr/lib/libgcc_s.so.1"
 
     add_runscript
 }
@@ -113,8 +121,8 @@ initrd shell):
    - default (and minimum value): 2 minutes
    - negative value to deactivate
 
-Each SSH server key ('dropbear_rsa_host_key', 'dropbear_dss_host_key' and
-'dropbear_ecdsa_host_key' in '/etc/dropbear' folder) is imported from OpenSSH
+Each SSH server key ('dropbear_rsa_host_key', 'dropbear_ecdsa_host_key' and
+'dropbear_ed25519_host_key' in '/etc/dropbear' folder) is imported from OpenSSH
 if present or generated if missing. Fingerprints are displayed upon building
 the initramfs image.
 EOF