[oe-core][RFC 2/3] u-boot: Add infrastructure to SPL verified boot

Klaus Heinrich Kiwi klaus at linux.vnet.ibm.com
Sat Mar 6 22:28:21 AEDT 2021


Add the necessary infrastructure to create a U-boot proper fitimage,
sign it (using the same keys as the kernel-fitimage), and put the public
key in the SPL binary so that verified SPL boot can be accomplished.

Signed-off-by: Klaus Heinrich Kiwi <klaus at linux.vnet.ibm.com>
---
 meta/classes/kernel-fitimage.bbclass |   7 +
 meta/classes/uboot-sign.bbclass      | 306 +++++++++++++++++++++++++--
 2 files changed, 296 insertions(+), 17 deletions(-)

diff --git a/meta/classes/kernel-fitimage.bbclass b/meta/classes/kernel-fitimage.bbclass
index 76e2e6c136..3b72d5495a 100644
--- a/meta/classes/kernel-fitimage.bbclass
+++ b/meta/classes/kernel-fitimage.bbclass
@@ -694,6 +694,13 @@ kernel_do_deploy_append() {
 			# ${UBOOT_DTB_IMAGE} since it contains ${PV} which is aimed
 			# for u-boot, but we are in kernel env now.
 			install -m 0644 ${B}/u-boot-${MACHINE}*.dtb "$deployDir/"
+			if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${UBOOT_BINARY}" -a -n "${SPL_DTB_BINARY}" ] ; then
+				# If we're also signing the uboot fit, now we need to
+				# deploy it, as well as u-boot-spl.dtb
+				install -m 0644 ${B}/u-boot-spl-${MACHINE}*.dtb "$deployDir/"
+				echo "Copying u-boot-fitImage file..."
+				install -m 0644 ${B}/u-boot-fitImage "$deployDir/u-boot-fitImage-${MACHINE}.${UBOOT_SUFFIX}"
+			fi
 		fi
 	fi
 }
diff --git a/meta/classes/uboot-sign.bbclass b/meta/classes/uboot-sign.bbclass
index d57bef6669..c362cbfd9c 100644
--- a/meta/classes/uboot-sign.bbclass
+++ b/meta/classes/uboot-sign.bbclass
@@ -36,6 +36,7 @@ inherit uboot-config
 
 # Signature activation.
 UBOOT_SIGN_ENABLE ?= "0"
+SPL_SIGN_ENABLE ?= "0"
 
 # Default value for deployment filenames.
 UBOOT_DTB_IMAGE ?= "u-boot-${MACHINE}-${PV}-${PR}.dtb"
@@ -77,8 +78,18 @@ FIT_KEY_REQ_ARGS ?= "-batch -new"
 # Standard format for public key certificate
 FIT_KEY_SIGN_PKCS ?= "-x509"
 
-# Functions in this bbclass is for u-boot only
+# Functions on this bbclass can apply to either U-boot or Kernel,
+# depending on the scenario
 UBOOT_PN = "${@d.getVar('PREFERRED_PROVIDER_u-boot') or 'u-boot'}"
+KERNEL_PN = "${@d.getVar('PREFERRED_PROVIDER_virtual/kernel')}"
+
+# We need u-boot-tools-native if we're about to sign the SPL
+python() {
+    if d.getVar('SPL_SIGN_ENABLE') == '1':
+        depends = d.getVar("DEPENDS")
+        depends = "%s u-boot-tools-native dtc-native" % depends
+        d.setVar("DEPENDS", depends)
+}
 
 concat_dtb_helper() {
 	if [ -e "${UBOOT_DTB_BINARY}" ]; then
@@ -92,21 +103,64 @@ concat_dtb_helper() {
 		ln -sf ${UBOOT_NODTB_IMAGE} ${DEPLOYDIR}/${UBOOT_NODTB_BINARY}
 	fi
 
-	# Concatenate U-Boot w/o DTB & DTB with public key
-	# (cf. kernel-fitimage.bbclass for more details)
-	deployed_uboot_dtb_binary='${DEPLOY_DIR_IMAGE}/${UBOOT_DTB_IMAGE}'
-	if [ "x${UBOOT_SUFFIX}" = "ximg" -o "x${UBOOT_SUFFIX}" = "xrom" ] && \
-		[ -e "$deployed_uboot_dtb_binary" ]; then
-		oe_runmake EXT_DTB=$deployed_uboot_dtb_binary
-		install ${UBOOT_BINARY} ${DEPLOYDIR}/${UBOOT_IMAGE}
-	elif [ -e "${DEPLOYDIR}/${UBOOT_NODTB_IMAGE}" -a -e "$deployed_uboot_dtb_binary" ]; then
+	# If we're not using a signed u-boot fit, concatenate SPL w/o DTB & U-Boot DTB
+	# with public key (otherwise it will be deployed by the equivalent
+	# concat_spl_dtb_helper function - cf. kernel-fitimage.bbclass for more details)
+	if [ "${SPL_SIGN_ENABLE}" != "1" ] ; then
+		deployed_uboot_dtb_binary='${DEPLOY_DIR_IMAGE}/${UBOOT_DTB_IMAGE}'
+		if [ "x${UBOOT_SUFFIX}" = "ximg" -o "x${UBOOT_SUFFIX}" = "xrom" ] && \
+			[ -e "$deployed_uboot_dtb_binary" ]; then
+			oe_runmake EXT_DTB=$deployed_uboot_dtb_binary
+			install ${UBOOT_BINARY} ${DEPLOYDIR}/${UBOOT_IMAGE}
+		elif [ -e "${DEPLOYDIR}/${UBOOT_NODTB_IMAGE}" -a -e "$deployed_uboot_dtb_binary" ]; then
+			cd ${DEPLOYDIR}
+			cat ${UBOOT_NODTB_IMAGE} $deployed_uboot_dtb_binary | tee ${B}/${CONFIG_B_PATH}/${UBOOT_BINARY} > ${UBOOT_IMAGE}
+		else
+			bbwarn "Failure while adding public key to u-boot binary. Verified boot won't be available."
+		fi
+	fi
+}
+
+concat_spl_dtb_helper() {
+	# Deploy the U-boot its file, spl dtb and the spl nodtb binary
+
+	if [ -e "${UBOOT_ITS}" ] ; then
+		echo "Copying uboot-fit-image.its source file..."
+		install -m 0644 ${UBOOT_ITS} "${DEPLOYDIR}/${UBOOT_ITS_IMAGE}"
+		ln -sf ${UBOOT_ITS_IMAGE} ${DEPLOYDIR}/${UBOOT_ITS_SYMLINK}
+		ln -sf ${UBOOT_ITS_IMAGE} ${DEPLOYDIR}/${UBOOT_ITS}
+	fi
+
+	if [ -e "${SPL_DIR}/${SPL_DTB_BINARY}" ] ; then
+		# We only deploy u-boot-spl.dtb real file if we are NOT
+		# signing the kernel, otherwise the kernel PN will do
+		# it for us (see kernel-fitimage.bbclass)
+		if [ "${UBOOT_SIGN_ENABLE}" != "1" ] ; then
+			install -m 0644 ${SPL_DIR}/${SPL_DTB_BINARY} \
+			    ${DEPLOYDIR}/${SPL_DTB_IMAGE}
+		fi;
+		ln -sf ${SPL_DTB_IMAGE} ${DEPLOYDIR}/${SPL_DTB_SYMLINK}
+		ln -sf ${SPL_DTB_IMAGE} ${DEPLOYDIR}/${SPL_DTB_BINARY}
+	fi
+
+	if [ -f "${SPL_DIR}/${SPL_NODTB_BINARY}" ] ; then
+		echo "Copying u-boot-nodtb binary..."
+		install -m 0644 ${SPL_DIR}/${SPL_NODTB_BINARY} ${DEPLOYDIR}/${SPL_NODTB_IMAGE}
+		ln -sf ${SPL_NODTB_IMAGE} ${DEPLOYDIR}/${SPL_NODTB_SYMLINK}
+		ln -sf ${SPL_NODTB_IMAGE} ${DEPLOYDIR}/${SPL_NODTB_BINARY}
+	fi
+
+	# Concatenate the SPL nodtb binary and u-boot.dtb (with pubkey)
+	deployed_spl_dtb_binary='${DEPLOY_DIR_IMAGE}/${SPL_DTB_IMAGE}'
+	if [ -e "${DEPLOYDIR}/${SPL_NODTB_IMAGE}" -a -e "$deployed_spl_dtb_binary" ] ; then
 		cd ${DEPLOYDIR}
-		cat ${UBOOT_NODTB_IMAGE} $deployed_uboot_dtb_binary | tee ${B}/${CONFIG_B_PATH}/${UBOOT_BINARY} > ${UBOOT_IMAGE}
+		cat ${SPL_NODTB_IMAGE} $deployed_spl_dtb_binary | tee ${B}/${CONFIG_B_PATH}/${SPL_BINARY} > ${SPL_IMAGE}
 	else
-		bbwarn "Failure while adding public key to u-boot binary. Verified boot won't be available."
+		bbwarn "Failure while adding public key to spl binary. Verified U-Boot boot won't be available."
 	fi
 }
 
+
 concat_dtb() {
 	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${UBOOT_DTB_BINARY}" ]; then
 		mkdir -p ${DEPLOYDIR}
@@ -124,6 +178,24 @@ concat_dtb() {
 	fi
 }
 
+concat_spl_dtb() {
+	if [ "${SPL_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${SPL_DTB_BINARY}" ]; then
+		mkdir -p ${DEPLOYDIR}
+		if [ -n "${UBOOT_CONFIG}" ]; then
+			for config in ${UBOOT_MACHINE}; do
+				CONFIG_B_PATH="${config}"
+				cd ${B}/${config}
+				concat_spl_dtb_helper
+			done
+		else
+			CONFIG_B_PATH=""
+			cd ${B}
+			concat_spl_dtb_helper
+		fi
+	fi
+}
+
+
 # Install UBOOT_DTB_BINARY to datadir, so that kernel can use it for
 # signing, and kernel will deploy UBOOT_DTB_BINARY after signs it.
 install_helper() {
@@ -138,30 +210,230 @@ install_helper() {
 	fi
 }
 
+# Install SPL dtb and u-boot nodtb to datadir, 
+install_spl_helper() {
+	if [ -f "${SPL_DIR}/${SPL_DTB_BINARY}" ]; then
+		install -d ${D}${datadir}
+		install ${SPL_DIR}/${SPL_DTB_BINARY} ${D}${datadir}/${SPL_DTB_IMAGE}
+		ln -sf ${SPL_DTB_IMAGE} ${D}${datadir}/${SPL_DTB_BINARY}
+	else
+		bbwarn "${SPL_DTB_BINARY} not found"
+	fi
+	if [ -f "${UBOOT_NODTB_BINARY}" ] ; then
+		install ${UBOOT_NODTB_BINARY} ${D}${datadir}/${UBOOT_NODTB_IMAGE}
+		ln -sf ${UBOOT_NODTB_IMAGE} ${D}${datadir}/${UBOOT_NODTB_BINARY}
+	else
+		bbwarn "${UBOOT_NODTB_BINARY} not found"
+	fi
+}
+
 do_install_append() {
-	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a "${PN}" = "${UBOOT_PN}" -a -n "${UBOOT_DTB_BINARY}" ]; then
+	if [ "${PN}" = "${UBOOT_PN}" ]; then
 		if [ -n "${UBOOT_CONFIG}" ]; then
 			for config in ${UBOOT_MACHINE}; do
 				cd ${B}/${config}
-				install_helper
+				if [ "${UBOOT_SIGN_ENABLE}" = "1" -a -n "${UBOOT_DTB_BINARY}" ]; then
+					install_helper
+				fi
+				if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ]; then
+					install_spl_helper
+				fi
 			done
 		else
 			cd ${B}
-			install_helper
+			if [ "${UBOOT_SIGN_ENABLE}" = "1" -a -n "${UBOOT_DTB_BINARY}" ]; then
+				install_helper
+			fi
+			if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ]; then
+				install_spl_helper
+			fi
+		fi
+	fi
+}
+
+do_generate_rsa_keys() {
+	if [ "${UBOOT_SIGN_ENABLE}" = "0" ] && [ "${FIT_GENERATE_KEYS}" = "1" ]; then
+		bbwarn "FIT_GENERATE_KEYS is set to 1 eventhough UBOOT_SIGN_ENABLE is set to 0. The keys will not be generated as they won't be used."
+	fi
+
+	if [ "${UBOOT_SIGN_ENABLE}" = "1" ] && [ "${FIT_GENERATE_KEYS}" = "1" ]; then
+
+		# Generate keys only if they don't already exist
+		if [ ! -f "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".key ] || \
+			[ ! -f "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".crt ]; then
+
+			# make directory if it does not already exist
+			mkdir -p "${UBOOT_SIGN_KEYDIR}"
+
+			echo "Generating RSA private key for signing fitImage"
+			openssl genrsa ${FIT_KEY_GENRSA_ARGS} -out \
+				"${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".key \
+				"${FIT_SIGN_NUMBITS}"
+
+			echo "Generating certificate for signing fitImage"
+			openssl req ${FIT_KEY_REQ_ARGS} "${FIT_KEY_SIGN_PKCS}" \
+				-key "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".key \
+				-out "${UBOOT_SIGN_KEYDIR}/${UBOOT_SIGN_KEYNAME}".crt
+		fi
+	fi
+}
+
+addtask generate_rsa_keys before do_uboot_assemble_fitimage after do_compile
+
+# Create a ITS file for the U-boot FIT, for use when
+# we want to sign it so that the SPL can verify it
+uboot_fitimage_assemble() {
+	uboot_its="${1}"
+	uboot_nodtb_bin="${2}"
+	uboot_dtb="${3}"
+	uboot_bin="${4}"
+	spl_dtb="${5}"
+	uboot_csum="${FIT_HASH_ALG}"
+	uboot_sign_algo="${FIT_SIGN_ALG}"
+	uboot_sign_keyname="${UBOOT_SIGN_KEYNAME}"
+
+	rm -f ${uboot_its} ${uboot_bin}
+
+	# First we create the ITS script
+	cat << EOF >> ${uboot_its}
+/dts-v1/;
+
+/ {
+    description = "U-boot FIT";
+    #address-cells = <1>;
+
+    images {
+        uboot {
+            description = "U-Boot image";
+            data = /incbin/("${uboot_nodtb_bin}");
+            type = "standalone";
+            os = "U-Boot";
+            arch = "${UBOOT_ARCH}";
+            compression = "none";
+            load = <${UBOOT_LOADADDRESS}>;
+            entry = <${UBOOT_ENTRYPOINT}>;
+            hash {
+                algo = "${uboot_csum}";
+            };
+            signature {
+                algo = "${uboot_csum},${uboot_sign_algo}";
+                key-name-hint = "${uboot_sign_keyname}";
+            };
+        };
+        fdt {
+            description = "U-Boot FDT";
+            data = /incbin/("${uboot_dtb}");
+            type = "flat_dt";
+            arch = "${UBOOT_ARCH}";
+            compression = "none";
+            hash {
+                algo = "${uboot_csum}";
+            };
+            signature {
+                algo = "${uboot_csum},${uboot_sign_algo}";
+                key-name-hint = "${uboot_sign_keyname}";
+            };
+        };
+    };
+
+    configurations {
+        default = "conf";
+        conf {
+            description = "Boot with signed U-Boot FIT";
+            loadables = "uboot";
+            fdt = "fdt";
+            hash {
+                algo = "${uboot_csum}";
+            };
+            signature {
+                algo = "${uboot_csum},${uboot_sign_algo}";
+                key-name-hint = "${uboot_sign_keyname}";
+                sign-images = "loadables", "fdt";
+            };
+        };
+    };
+};
+EOF
+
+	#
+	# Assemble the U-boot FIT image
+	#
+	${UBOOT_MKIMAGE} \
+		${@'-D "${UBOOT_MKIMAGE_DTCOPTS}"' if len('${UBOOT_MKIMAGE_DTCOPTS}') else ''} \
+		-f ${uboot_its} \
+		${uboot_bin}
+
+	#
+	# Sign the U-boot FIT image and add public key to SPL dtb
+	#
+	${UBOOT_MKIMAGE_SIGN} \
+		${@'-D "${UBOOT_MKIMAGE_DTCOPTS}"' if len('${UBOOT_MKIMAGE_DTCOPTS}') else ''} \
+		-F -k "${UBOOT_SIGN_KEYDIR}" \
+		-K "${spl_dtb}" \
+		-r ${uboot_bin} \
+		${UBOOT_MKIMAGE_SIGN_ARGS}
+
+}
+
+do_uboot_assemble_fitimage() {
+	# This function runs in both UBOOT_PN as well as KERNEL_PN contexts. The reason
+	# for that is that we need to be able to support SPL verified boot standalone,
+	# as well as in the scenario where U-boot verified boot is enabled. On the latter
+	# case, we can only sign our U-BOOT fit after the KERNEL_PN signed the fitimage,
+	# as well as placed the pubkey in the U-boot DTB. Note that the Signed U-boot
+	# FIT and SPL with the pubkey will only be available in the deploy dir, not on
+	# the u-boot package
+	if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ] ; then
+		if [ "${PN}" = "${UBOOT_PN}" ] ; then
+			if [ -n "${UBOOT_CONFIG}" ]; then
+				for config in ${UBOOT_MACHINE}; do
+					cd ${B}/${config}
+					uboot_fitimage_assemble ${UBOOT_ITS} ${UBOOT_NODTB_BINARY} ${UBOOT_DTB_BINARY} u-boot-fitImage ${SPL_DIR}/${SPL_DTB_BINARY}
+				done
+			else
+				cd ${B}
+				uboot_fitimage_assemble ${UBOOT_ITS} ${UBOOT_NODTB_BINARY} ${UBOOT_DTB_BINARY} u-boot-fitImage ${SPL_DIR}/${SPL_DTB_BINARY}
+			fi
+		elif [ "${UBOOT_SIGN_ENABLE}" = "1" -a "${PN}" = "${KERNEL_PN}" ] ; then
+			# As we are in the kernel context, we need to copy u-boot-spl.dtb from staging first.
+			# Unfortunately, need to glob on top of ${SPL_DTB_BINARY} since _IMAGE and _SYMLINK
+			# will contain U-boot's PV
+			# As for the u-boot.dtb (with fitimage's pubkey), it should come from the dependent
+			# do_assemble_fitimage task
+			cp -P ${STAGING_DATADIR}/${@os.path.splitext(d.getVar("SPL_DTB_BINARY"))[0]}*.dtb ${B}
+			cp -P ${STAGING_DATADIR}/u-boot-nodtb*.${UBOOT_SUFFIX} ${B}
+			cd ${B}
+			uboot_fitimage_assemble ${UBOOT_ITS} ${UBOOT_NODTB_BINARY} ${UBOOT_DTB_BINARY} u-boot-fitImage ${SPL_DTB_BINARY}
 		fi
 	fi
 }
 
+addtask uboot_assemble_fitimage before do_install after do_compile
+
+python () {
+    if d.getVar('UBOOT_SIGN_ENABLE') == '1' and d.getVar('PN') == d.getVar('KERNEL_PN'):
+        d.appendVarFlag('do_uboot_assemble_fitimage', 'depends', ' %s:do_assemble_fitimage' % d.getVar('KERNEL_PN'))
+}
+
 do_deploy_prepend_pn-${UBOOT_PN}() {
-	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a -n "${UBOOT_DTB_BINARY}" ]; then
+	if [ "${UBOOT_SIGN_ENABLE}" = "1" -a -n "${UBOOT_DTB_BINARY}" ] ; then
 		concat_dtb
 	fi
+	if [ "${SPL_SIGN_ENABLE}" = "1" -a -n "${SPL_DTB_BINARY}" ] ; then
+		concat_spl_dtb
+	fi
+}
+
+do_deploy_append_pn-${UBOOT_PN}() {
+	if [ "${SPL_SIGN_ENABLE}" = "1" -a "${UBOOT_SIGN_ENABLE}" != "1" ] ; then
+		# Only deploy u-boot-fitimage if the KERNEL_PN is not already doing so
+		install -m 0644 ${B}/u-boot-fitImage "${DEPLOYDIR}/u-boot-fitImage-${MACHINE}.${UBOOT_SUFFIX}"
+	fi
 }
 
 python () {
     if d.getVar('UBOOT_SIGN_ENABLE') == '1' and d.getVar('PN') == d.getVar('UBOOT_PN') and d.getVar('UBOOT_DTB_BINARY'):
-        kernel_pn = d.getVar('PREFERRED_PROVIDER_virtual/kernel')
 
         # Make "bitbake u-boot -cdeploy" deploys the signed u-boot.dtb
-        d.appendVarFlag('do_deploy', 'depends', ' %s:do_deploy' % kernel_pn)
+        d.appendVarFlag('do_deploy', 'depends', ' %s:do_deploy' % d.getVar('KERNEL_PN'))
 }
-- 
2.25.1



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