secureboot: Enable signing SONiC kernel (sonic-net#10557)

Why I did it
To sign SONiC kernel image and allow secure boot based system to verify SONiC image before loading into the system.

How I did it
Pass following parameter to rules/config.user
Ex:
SONIC_ENABLE_SECUREBOOT_SIGNATURE := y
SIGNING_KEY := /path/to/key/private.key
SIGNING_CERT := /path/to/public/public.cert

How to verify it
Secure boot enabled system enrolled with right public key of the, image in the platform UEFI database will able to verify image before load.

Alternatively one can verify with offline sbsign tool as below.

export SBSIGN_KEY=/abc/bcd/xyz/
sbverify --cert $SBSIGN_KEY/public_cert.cert fsroot-platform-XYZ/boot/vmlinuz-5.10.0-8-2-amd64 mage

O/P:
Signature verification OK

Author: sacnaik

Makefile.work

@@ -182,6 +182,17 @@ ifneq ($(SONIC_DPKG_CACHE_SOURCE),)
 	DOCKER_RUN += -v "$(SONIC_DPKG_CACHE_SOURCE):/dpkg_cache:rw"
 endif
 
+ifeq ($(SONIC_ENABLE_SECUREBOOT_SIGNATURE), y)
+ifneq ($(SIGNING_KEY),)
+	DOCKER_SIGNING_SOURCE := $(shell dirname $(SIGNING_KEY))
+	DOCKER_RUN += -v "$(DOCKER_SIGNING_SOURCE):$(DOCKER_SIGNING_SOURCE):ro"
+endif
+ifneq ($(SIGNING_CERT),)
+	DOCKER_SIGNING_SOURCE := $(shell dirname $(SIGNING_CERT))
+	DOCKER_RUN += -v "$(DOCKER_SIGNING_SOURCE):$(DOCKER_SIGNING_SOURCE):ro"
+endif
+endif
+
 ifeq ($(SONIC_CONFIG_USE_NATIVE_DOCKERD_FOR_BUILD), y)
     DOCKER_RUN += -v /var/run/docker.sock:/var/run/docker.sock
 endif
@@ -278,6 +289,7 @@ SONIC_BUILD_INSTRUCTION :=  make \
                            EXTRA_DOCKER_TARGETS=$(EXTRA_DOCKER_TARGETS) \
                            BUILD_LOG_TIMESTAMP=$(BUILD_LOG_TIMESTAMP) \
                            SONIC_ENABLE_IMAGE_SIGNATURE=$(ENABLE_IMAGE_SIGNATURE) \
+                           SONIC_ENABLE_SECUREBOOT_SIGNATURE=$(SONIC_ENABLE_SECUREBOOT_SIGNATURE) \
                            SONIC_DEFAULT_CONTAINER_REGISTRY=$(DEFAULT_CONTAINER_REGISTRY) \
                            SLAVE_DIR=$(SLAVE_DIR) \
                            $(SONIC_OVERRIDE_BUILD_VARS)

build_debian.sh

@@ -143,6 +143,23 @@ if [[ $CONFIGURED_ARCH == amd64 ]]; then
     sudo LANG=C DEBIAN_FRONTEND=noninteractive chroot $FILESYSTEM_ROOT apt-get -y install dmidecode hdparm
 fi
 
+## Sign the Linux kernel
+if [ "$SONIC_ENABLE_SECUREBOOT_SIGNATURE" = "y" ]; then
+    if [ ! -f $SIGNING_KEY ]; then
+       echo "Error: SONiC linux kernel signing key missing"
+       exit 1
+    fi
+    if [ ! -f $SIGNING_CERT ]; then
+       echo "Error: SONiC linux kernel signing certificate missing"
+       exit 1
+    fi
+
+    echo '[INFO] Signing SONiC linux kernel image'
+    K=$FILESYSTEM_ROOT/boot/vmlinuz-${LINUX_KERNEL_VERSION}-amd64
+    sbsign --key $SIGNING_KEY --cert $SIGNING_CERT --output /tmp/${K##*/} ${K}
+    sudo cp -f /tmp/${K##*/} ${K}
+fi
+
 ## Update initramfs for booting with squashfs+overlay
 cat files/initramfs-tools/modules | sudo tee -a $FILESYSTEM_ROOT/etc/initramfs-tools/modules > /dev/null
 

rules/config

@@ -169,6 +169,13 @@ K8s_GCR_IO_PAUSE_VERSION = 3.4.1
 # The relative path is build root folder.
 SONIC_ENABLE_IMAGE_SIGNATURE ?= n
 
+# SONIC_ENABLE_SECUREBOOT_SIGNATURE - enable SONiC kernel signing to support UEFI secureboot
+# To support UEFI secureboot chain of trust requires EFI kernel to be signed as a PE binary
+#     SIGNING_KEY =
+#     SIGNING_CERT =
+# The absolute path should be provided.
+SONIC_ENABLE_SECUREBOOT_SIGNATURE ?= n
+
 # PACKAGE_URL_PREFIX - the package url prefix
 PACKAGE_URL_PREFIX ?= https://packages.trafficmanager.net/public/packages
 

slave.mk

@@ -1042,6 +1042,9 @@ $(addprefix $(TARGET_PATH)/, $(SONIC_INSTALLERS)) : $(TARGET_PATH)/% : \
 	TARGET_PATH=$(TARGET_PATH) \
 	SONIC_ENFORCE_VERSIONS=$(SONIC_ENFORCE_VERSIONS) \
 	TRUSTED_GPG_URLS=$(TRUSTED_GPG_URLS) \
+	SONIC_ENABLE_SECUREBOOT_SIGNATURE="$(SONIC_ENABLE_SECUREBOOT_SIGNATURE)" \
+	SIGNING_KEY="$(SIGNING_KEY)" \
+	SIGNING_CERT="$(SIGNING_CERT)" \
 	PACKAGE_URL_PREFIX=$(PACKAGE_URL_PREFIX) \
 	MULTIARCH_QEMU_ENVIRON=$(MULTIARCH_QEMU_ENVIRON) \
 		./build_debian.sh $(LOG)

sonic-slave-buster/Dockerfile.j2

@@ -124,6 +124,7 @@ RUN apt-get update && apt-get install -y \
         devscripts \
         quilt \
         stgit \
+        sbsigntool \
 # For platform-modules build
         module-assistant \
 # For thrift build\