bake: Add signed verity format

This uses systemd-repart for image generation, but requires the unreleased v255
due to bugs and missing features in earlier versions.

Signed-off-by: Jeremi Piotrowski <[email protected]>

Author: jepio

README.md

@@ -177,3 +177,14 @@ In case you have an existing Torcx image you can convert it with the `convert_to
 ```
 
 Please make also sure that your don't have a `containerd.service` drop in file under `/etc` that uses Torcx paths.
+
+
+### Verity
+
+To generate sysext protected by dm-verity with a signed root hash pass `FORMAT=verity` before invoking any of the scripts. This requires `systemd-repart` with a version >= v255. This also requires passing a path to a private key and certificate through `KEY` and `CERT`.
+
+Here's an example:
+```
+openssl req -batch -new -x509 -sha256 -newkey rsa:2048 -nodes -out root_key.crt -keyout root_key.pem -days 3650
+FORMAT=verity KEY=root_key.pem CERT=root_key.crt ./create_kubernetes_sysext.sh v1.27.3 k8s
+```

bake.sh

@@ -4,6 +4,13 @@ set -euo pipefail
 OS="${OS-flatcar}"
 FORMAT="${FORMAT:-squashfs}"
 ARCH="${ARCH-}"
+KEY="${KEY-}"
+CERT="${CERT-}"
+
+die() {
+  echo >&2 "$@"
+  exit 1
+}
 
 # This script is to be called as helper by other scripts but can also be used standalone
 if [ $# -lt 1 ]; then
@@ -19,12 +26,20 @@ elif [ "$1" = "-h" ] || [ "$1" = "--help" ]; then
   exit 1
 fi
 
+if [ "${FORMAT}" = "verity" ]; then
+  [ -z "${KEY}" ] && die "\$KEY required for verity"
+  [ -z "${CERT}" ] && die "\$CERT required for verity"
+fi
+
 SYSEXTNAME="$1"
 
-if [ "${FORMAT}" != "squashfs" ] && [ "${FORMAT}" != "btrfs" ] && [ "${FORMAT}" != "ext4" ] && [ "${FORMAT}" != "ext2" ]; then
-  echo "Expected FORMAT=squashfs, FORMAT=btrfs, FORMAT=ext4, or FORMAT=ext2, got '${FORMAT}'" >&2
-  exit 1
-fi
+case ${FORMAT} in
+  squashfs) ;;
+  btrfs) ;;
+  ext4|ext2) ;;
+  verity) ;;
+  *) die "Unsupported format: '${FORMAT}'" ;;
+esac
 
 # Map to valid values for https://www.freedesktop.org/software/systemd/man/os-release.html#ARCHITECTURE=
 if [ "${ARCH}" = "amd64" ] || [ "${ARCH}" = "x86_64" ]; then
@@ -54,7 +69,11 @@ elif [ "${FORMAT}" = "ext4" ] || [ "${FORMAT}" = "ext2" ]; then
   # Note: We didn't chown to root:root, meaning that the file ownership is left as is
   mkfs."${FORMAT}" -E root_owner=0:0 -d "${SYSEXTNAME}" "${SYSEXTNAME}".raw
   resize2fs -M "${SYSEXTNAME}".raw
-else
+elif [ "${FORMAT}" = "squashfs" ]; then
   mksquashfs "${SYSEXTNAME}" "${SYSEXTNAME}".raw -all-root
+elif [ "${FORMAT}" = "verity" ]; then
+  systemd-repart --private-key="${KEY}" --certificate="${CERT}" --root="${SYSEXTNAME}" --no-pager --empty=create --size=auto --definitions=repart.d "${SYSEXTNAME}.raw"
+else
+  die "Unsupported format: ${FORMAT}"
 fi
 echo "Created ${SYSEXTNAME}.raw"

repart.d/01-root.conf

@@ -0,0 +1,7 @@
+[Partition]
+Type=root
+CopyFiles=/:/
+Format=squashfs
+Minimize=best
+Verity=data
+VerityMatchKey=sysext

repart.d/02-verity.conf

@@ -0,0 +1,7 @@
+[Partition]
+Type=root-verity
+Verity=hash
+VerityMatchKey=sysext
+# Only works from v255
+Minimize=best
+SizeMinBytes=4K

repart.d/03-verity-sig.conf

@@ -0,0 +1,4 @@
+[Partition]
+Type=root-verity-sig
+Verity=signature
+VerityMatchKey=sysext