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Bartosz Golaszewski d6369c9aaf dm-verity: add a working example for BeagleBone Black
This adds various bits and pieces to enable generating a working example
of a full chain of trust up to dm-verity-protected rootfs level on Beagle
Bone Black.

The new initramfs is quite generic and should work for other SoCs as well
when using fitImage.

The following config can be used with current master poky,
meta-openembedded & meta-security to generate a BBB image using verified
boot and dm-verity.

  UBOOT_SIGN_KEYDIR = "/tmp/test-keys/"
  UBOOT_SIGN_KEYNAME = "dev"
  UBOOT_SIGN_ENABLE = "1"
  UBOOT_MKIMAGE_DTCOPTS = "-I dts -O dtb -p 2000"
  UBOOT_MACHINE_beaglebone-yocto = "am335x_boneblack_vboot_config"

  IMAGE_CLASSES += "dm-verity-img"
  IMAGE_FSTYPES += "wic.xz ext4"

  DM_VERITY_IMAGE = "core-image-full-cmdline"
  DM_VERITY_IMAGE_TYPE = "ext4"

  KERNEL_CLASSES += "kernel-fitimage"
  KERNEL_IMAGETYPE_beaglebone-yocto = "fitImage"

  IMAGE_INSTALL_remove = " kernel-image-zimage"
  IMAGE_BOOT_FILES_remove = " zImage"
  IMAGE_BOOT_FILES_append = " fitImage-${INITRAMFS_IMAGE}-${MACHINE}-${MACHINE};fitImage"

  # Using systemd is not strictly needed but deals nicely with read-only
  # filesystem by default.
  DISTRO_FEATURES_append = " systemd"
  DISTRO_FEATURES_BACKFILL_CONSIDERED += "sysvinit"
  VIRTUAL-RUNTIME_init_manager = "systemd"
  VIRTUAL-RUNTIME_initscripts = "systemd-compat-units"

  INITRAMFS_IMAGE = "dm-verity-image-initramfs"
  INITRAMFS_FSTYPES = "cpio.gz"
  INITRAMFS_IMAGE_BUNDLE = "1"

  WKS_FILE = "beaglebone-yocto-verity.wks.in"

  KERNEL_FEATURES_append = " features/device-mapper/dm-verity.scc"

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>
2020-05-15 05:28:21 -07:00

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#!/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
RDEV=""
ROOT_DIR="/new_root"
mkdir -p /proc
mkdir -p /sys
mkdir -p /run
mkdir -p /tmp
mount -t proc proc /proc
mount -t sysfs sysfs /sys
mount -t devtmpfs none /dev
udevd --daemon
udevadm trigger --type=subsystems --action=add
udevadm trigger --type=devices --action=add
udevadm settle --timeout=10
for PARAM in $(cat /proc/cmdline); do
case $PARAM in
root=*)
RDEV=${PARAM#root=}
;;
esac
done
if ! [ -b $RDEV ]; then
echo "Missing root command line argument!"
exit 1
fi
case $RDEV in
UUID=*)
RDEV=$(realpath /dev/disk/by-uuid/${RDEV#UUID=})
;;
esac
. /usr/share/dm-verity.env
echo "Mounting $RDEV over dm-verity as the root filesystem"
veritysetup --data-block-size=1024 --hash-offset=$DATA_SIZE create rootfs $RDEV $RDEV $ROOT_HASH
mkdir -p $ROOT_DIR
mount -o ro /dev/mapper/rootfs $ROOT_DIR
exec switch_root $ROOT_DIR /sbin/init