Add an optional dynamic layer enabling dm-verity block-level integrity verification of the root filesystem for TI K3 platforms, using meta-security's stock dm-verity mechanism as-is. Requires meta-security to be present in bblayers.conf.
dm-verity hashes the rootfs at build time; at boot, a dedicated initramfs loads the root hash and the kernel checks every block read against it. Set DM_VERITY_IMAGE to enable all the verity-related recipes for that image; other images build as usual. Signed-off-by: Atharv Dubey <[email protected]> --- v4: - Use ti-core-initramfs instead of a separate dm-verity initramfs - Instead of a DISTRO_FEATURE, just check if DM_VERITY_IMAGE is set v3: - Disabled the automount rules from udev-aragoconf, so don't need the ignorelist for dm-verity v2: - Replaced hardcoded /dev/mmcblk1p2 with a PARTUUID --- meta-ti-bsp/conf/layer.conf | 3 +++ meta-ti-bsp/conf/machine/include/k3.inc | 7 ++++++ .../conf/include/dm-verity-upstream.inc | 23 +++++++++++++++++++ .../udev/udev-aragoconf_%.bbappend | 5 ++++ .../udev/udev-extraconf_%.bbappend | 6 +++++ meta-ti-bsp/files/wic/k3-verity.wks.in | 5 ++++ 6 files changed, 49 insertions(+) create mode 100644 meta-ti-bsp/dynamic-layers/security-layer/conf/include/dm-verity-upstream.inc create mode 100644 meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-aragoconf_%.bbappend create mode 100644 meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-extraconf_%.bbappend create mode 100644 meta-ti-bsp/files/wic/k3-verity.wks.in diff --git a/meta-ti-bsp/conf/layer.conf b/meta-ti-bsp/conf/layer.conf index 3cc54aa4..aca35cd3 100644 --- a/meta-ti-bsp/conf/layer.conf +++ b/meta-ti-bsp/conf/layer.conf @@ -20,12 +20,15 @@ LAYERDEPENDS_meta-ti-bsp = " \ LAYERRECOMMENDS_meta-ti-bsp = " \ openembedded-layer \ tpm-layer \ + security \ " BBFILES_DYNAMIC += " \ openembedded-layer:${LAYERDIR}/dynamic-layers/openembedded-layer/recipes*/*/*.bbappend \ tpm-layer:${LAYERDIR}/dynamic-layers/tpm-layer/recipes*/*/*.bb \ tpm-layer:${LAYERDIR}/dynamic-layers/tpm-layer/recipes*/*/*.bbappend \ + security:${LAYERDIR}/dynamic-layers/security-layer/recipes*/*/*.bb \ + security:${LAYERDIR}/dynamic-layers/security-layer/recipes*/*/*.bbappend \ " SIGGEN_EXCLUDERECIPES_ABISAFE += " \ diff --git a/meta-ti-bsp/conf/machine/include/k3.inc b/meta-ti-bsp/conf/machine/include/k3.inc index 2ebbfb9e..f19db45f 100644 --- a/meta-ti-bsp/conf/machine/include/k3.inc +++ b/meta-ti-bsp/conf/machine/include/k3.inc @@ -64,3 +64,10 @@ FALCON_INCLUDE = "" FALCON_INCLUDE:ti-falcon = "conf/machine/include/ti-falcon.inc" require ${FALCON_INCLUDE} + +# dm-verity protects the rootfs listed in DM_VERITY_IMAGE; see dynamic-layers/security-layer/conf/include/dm-verity-upstream.inc for what that turns on. +DM_VERITY_IMAGE ??= "" + +DM_VERITY_UPSTREAM_INCLUDE = "${@'dynamic-layers/security-layer/conf/include/dm-verity-upstream.inc' if d.getVar('DM_VERITY_IMAGE') else ''}" + +require ${DM_VERITY_UPSTREAM_INCLUDE} diff --git a/meta-ti-bsp/dynamic-layers/security-layer/conf/include/dm-verity-upstream.inc b/meta-ti-bsp/dynamic-layers/security-layer/conf/include/dm-verity-upstream.inc new file mode 100644 index 00000000..3ff2b7d6 --- /dev/null +++ b/meta-ti-bsp/dynamic-layers/security-layer/conf/include/dm-verity-upstream.inc @@ -0,0 +1,23 @@ +# Enables dm-verity to check the rootfs for tampering on TI K3 boards. +DM_VERITY_IMAGE_TYPE = "ext4" +IMAGE_CLASSES += "dm-verity-img" + +# ti-core-initramfs.bbappend already wires the initramfs into the boot partition once dm-verity is enabled, so we don't need to do it here. + +# Derive the root partition's UUID from MACHINE so everyone computes the same one. +python () { + import uuid + + if not d.getVar('DM_VERITY_ROOT_PARTUUID'): + d.setVar('DM_VERITY_ROOT_PARTUUID', + str(uuid.uuid5(uuid.NAMESPACE_DNS, 'dm-verity-root-%s' % d.getVar('MACHINE')))) +} + +python () { + if d.getVar('PN') != d.getVar('DM_VERITY_IMAGE'): + return + + d.setVar('WKS_FILE', 'k3-verity.wks.in') + d.appendVar('EXTRA_IMAGE_FEATURES', ' read-only-rootfs') + d.appendVar('WICVARS', ' DM_VERITY_IMAGE DM_VERITY_IMAGE_TYPE IMAGE_NAME_SUFFIX IMGDEPLOYDIR DM_VERITY_ROOT_PARTUUID') +} diff --git a/meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-aragoconf_%.bbappend b/meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-aragoconf_%.bbappend new file mode 100644 index 00000000..e5f6c1b2 --- /dev/null +++ b/meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-aragoconf_%.bbappend @@ -0,0 +1,5 @@ +do_install:append() { + if ${@'true' if d.getVar('DM_VERITY_IMAGE') else 'false'}; then + : > ${D}${libdir}/udev/rules.d/50-arago.rules + fi +} diff --git a/meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-extraconf_%.bbappend b/meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-extraconf_%.bbappend new file mode 100644 index 00000000..a14e21ea --- /dev/null +++ b/meta-ti-bsp/dynamic-layers/security-layer/recipes-core/udev/udev-extraconf_%.bbappend @@ -0,0 +1,6 @@ +# Nothing should ever get auto-mounted under dm-verity, so just kill the automounter. +do_install:append() { + if ${@'true' if d.getVar('DM_VERITY_IMAGE') else 'false'}; then + : > ${D}${sysconfdir}/udev/rules.d/automount.rules + fi +} diff --git a/meta-ti-bsp/files/wic/k3-verity.wks.in b/meta-ti-bsp/files/wic/k3-verity.wks.in new file mode 100644 index 00000000..62ae0ec1 --- /dev/null +++ b/meta-ti-bsp/files/wic/k3-verity.wks.in @@ -0,0 +1,5 @@ +# Disk layout for a board that boots with dm-verity enabled. + +bootloader --timeout=3 --append="rootfstype=ext4 root=PARTUUID=${DM_VERITY_ROOT_PARTUUID} ${TI_WKS_BOOTLOADER_APPEND}" +part --source bootimg-efi --sourceparams="loader=${EFI_PROVIDER}${TI_WKS_INITRAMFS}" --fstype=vfat --label boot --active --align 1024 --use-uuid --fixed-size 128M +part / --source rawcopy --sourceparams="file=${IMGDEPLOYDIR}/${DM_VERITY_IMAGE}-${MACHINE}${IMAGE_NAME_SUFFIX}.${DM_VERITY_IMAGE_TYPE}.verity" --align 1024 --uuid ${DM_VERITY_ROOT_PARTUUID} -- 2.34.1
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