Refactor SB signing code and sign official builds with Azure Key Vault

Signed-off-by: James Le Cuirot <jlecuirot@microsoft.com>

build_library/build_image_util.sh

@@ -20,6 +20,7 @@ BUILD_DIR="${FLAGS_output_root}/${BOARD}/${IMAGE_SUBDIR}"
 OUTSIDE_OUTPUT_DIR="../build/images/${BOARD}/${IMAGE_SUBDIR}"
 
 source "${BUILD_LIBRARY_DIR}/reports_util.sh" || exit 1
+source "${BUILD_LIBRARY_DIR}/sbsign_util.sh" || exit 1
 
 set_build_symlinks() {
     local build=$(basename ${BUILD_DIR})
@@ -826,13 +827,8 @@ EOF
   fi
 
   # Sign the kernel after /usr is in a consistent state and verity is calculated
-  if [[ ${COREOS_OFFICIAL:-0} -ne 1 ]]; then
-      sudo sbsign --key /usr/share/sb_keys/shim.key \
-	   --cert /usr/share/sb_keys/shim.pem \
-	   "${root_fs_dir}/boot/flatcar/vmlinuz-a"
-      sudo mv "${root_fs_dir}/boot/flatcar/vmlinuz-a.signed" \
-	   "${root_fs_dir}/boot/flatcar/vmlinuz-a"
-  fi
+  do_sbsign --output "${root_fs_dir}/boot/flatcar/vmlinuz-a"{,}
+  cleanup_sbsign_certs
 
   if [[ -n "${image_kernel}" ]]; then
     # copying kernel from vfat so ignore the permissions

build_library/grub_install.sh

@@ -35,36 +35,38 @@ switch_to_strict_mode
 # must be sourced after flags are parsed.
 . "${BUILD_LIBRARY_DIR}/toolchain_util.sh" || exit 1
 . "${BUILD_LIBRARY_DIR}/board_options.sh" || exit 1
+. "${BUILD_LIBRARY_DIR}/sbsign_util.sh" || exit 1
 
 # Our GRUB lives under flatcar/grub so new pygrub versions cannot find grub.cfg
 GRUB_DIR="flatcar/grub/${FLAGS_target}"
 
 # Modules required to boot a standard CoreOS configuration
 CORE_MODULES=( normal search test fat part_gpt search_fs_uuid gzio search_part_label terminal gptprio configfile memdisk tar echo read btrfs )
 
-# Name of the core image, depends on target
-CORE_NAME=
-
 SBAT_ARG=()
 
 case "${FLAGS_target}" in
-    i386-pc)
-        CORE_MODULES+=( biosdisk serial )
-        CORE_NAME="core.img"
-        ;;
     x86_64-efi)
-        CORE_MODULES+=( serial linux efi_gop efinet pgp http tftp tpm )
-        CORE_NAME="core.efi"
-        SBAT_ARG=( --sbat "${BOARD_ROOT}/usr/share/grub/sbat.csv" )
-        ;;
-    x86_64-xen)
-        CORE_NAME="core.elf"
+        EFI_ARCH="x64"
         ;;
     arm64-efi)
+        EFI_ARCH="aa64"
+        ;;
+esac
+
+case "${FLAGS_target}" in
+    x86_64-efi|arm64-efi)
+        GRUB_IMAGE="EFI/boot/grub${EFI_ARCH}.efi"
         CORE_MODULES+=( serial linux efi_gop efinet pgp http tftp tpm )
-        CORE_NAME="core.efi"
         SBAT_ARG=( --sbat "${BOARD_ROOT}/usr/share/grub/sbat.csv" )
         ;;
+    i386-pc)
+        GRUB_IMAGE="${GRUB_DIR}/core.img"
+        CORE_MODULES+=( biosdisk serial )
+        ;;
+    x86_64-xen)
+        GRUB_IMAGE="xen/pvboot-x86_64.elf"
+        ;;
     *)
         die_notrace "Unknown GRUB target ${FLAGS_target}"
         ;;
@@ -88,6 +90,7 @@ ESP_DIR=
 LOOP_DEV=
 
 cleanup() {
+    cleanup_sbsign_certs
     if [[ -d "${ESP_DIR}" ]]; then
         if mountpoint -q "${ESP_DIR}"; then
             sudo umount "${ESP_DIR}"
@@ -121,7 +124,7 @@ done
 if [[ -z ${MOUNTED} ]]; then
     failboat "${LOOP_DEV}p1 where art thou? udev has forsaken us!"
 fi
-sudo mkdir -p "${ESP_DIR}/${GRUB_DIR}"
+sudo mkdir -p "${ESP_DIR}/${GRUB_DIR}" "${ESP_DIR}/${GRUB_IMAGE%/*}"
 
 info "Compressing modules in ${GRUB_DIR}"
 for file in "${GRUB_SRC}"/*{.lst,.mod}; do
@@ -163,15 +166,15 @@ if [[ ! -f "${ESP_DIR}/flatcar/grub/grub.cfg.tar" ]]; then
       -C "${GRUB_TEMP_DIR}" "grub.cfg"
 fi
 
-info "Generating ${GRUB_DIR}/${CORE_NAME}"
+info "Generating ${GRUB_IMAGE}"
 sudo grub-mkimage \
     --compression=auto \
     --format "${FLAGS_target}" \
     --directory "${GRUB_SRC}" \
     --config "${ESP_DIR}/${GRUB_DIR}/load.cfg" \
     --memdisk "${ESP_DIR}/flatcar/grub/grub.cfg.tar" \
     "${SBAT_ARG[@]}" \
-    --output "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
+    --output "${ESP_DIR}/${GRUB_IMAGE}" \
     "${CORE_MODULES[@]}"
 
 for mod in "${CORE_MODULES[@]}"; do
@@ -180,77 +183,53 @@ done
 
 # Now target specific steps to make the system bootable
 case "${FLAGS_target}" in
-    i386-pc)
-        info "Installing MBR and the BIOS Boot partition."
-        sudo cp "${GRUB_SRC}/boot.img" "${ESP_DIR}/${GRUB_DIR}"
-        sudo grub-bios-setup --device-map=/dev/null \
-            --directory="${ESP_DIR}/${GRUB_DIR}" "${LOOP_DEV}"
-        # boot.img gets manipulated by grub-bios-setup so it alone isn't
-        # sufficient to restore the MBR boot code if it gets corrupted.
-        sudo dd bs=448 count=1 status=none if="${LOOP_DEV}" \
-            of="${ESP_DIR}/${GRUB_DIR}/mbr.bin"
-        ;;
-    x86_64-efi)
-        info "Installing default x86_64 UEFI bootloader."
-        sudo mkdir -p "${ESP_DIR}/EFI/boot"
-        # Use the test keys for signing unofficial builds
-        if [[ ${COREOS_OFFICIAL:-0} -ne 1 ]]; then
-            # Sign the GRUB with the shim-embedded key
-            sudo sbsign --key /usr/share/sb_keys/shim.key \
-                --cert /usr/share/sb_keys/shim.pem \
-                "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}"
-            sudo mv "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}.signed" \
-                "${ESP_DIR}/EFI/boot/grubx64.efi"
-            sudo rm "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}"
-            # Sign the mokmanager(mm) with the shim-embedded key
-            sudo sbsign --key /usr/share/sb_keys/shim.key \
-                --cert /usr/share/sb_keys/shim.pem \
-                "/usr/lib/shim/mmx64.efi"
-            sudo cp "/usr/lib/shim/mmx64.efi.signed" \
-                "${ESP_DIR}/EFI/boot/mmx64.efi"
+    x86_64-efi|arm64-efi)
+        info "Installing default ${FLAGS_target} UEFI bootloader."
 
-            sudo sbsign --key /usr/share/sb_keys/DB.key \
+        # Sign GRUB and mokmanager(mm) with the shim-embedded key.
+        do_sbsign --output "${ESP_DIR}/${GRUB_IMAGE}"{,}
+        do_sbsign --output "${ESP_DIR}/EFI/boot/mm${EFI_ARCH}.efi" \
+            "${BOARD_ROOT}/usr/lib/shim/mm${EFI_ARCH}.efi"
+
+        if [[ ${COREOS_OFFICIAL:-0} -ne 1 ]]; then
+            # Unofficial build: Sign shim with our development key.
+            sudo sbsign \
+                --key /usr/share/sb_keys/DB.key \
                 --cert /usr/share/sb_keys/DB.crt \
-                --output "${ESP_DIR}/EFI/boot/bootx64.efi" \
-                "/usr/lib/shim/shim.efi"
+                --output "${ESP_DIR}/EFI/boot/boot${EFI_ARCH}.efi" \
+                "${BOARD_ROOT}/usr/lib/shim/shim${EFI_ARCH}.efi"
         else
-            sudo mv "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
-                "${ESP_DIR}/EFI/boot/grubx64.efi"
-            sudo cp "/usr/lib/shim/shim.efi" \
-                "${ESP_DIR}/EFI/boot/bootx64.efi"
-            sudo cp "/usr/lib/shim/mmx64.efi" \
-                "${ESP_DIR}/EFI/boot/mmx64.efi"
+            # Official build: Copy our pre-signed shim.
+            sudo cp "${BOARD_ROOT}/usr/lib/shim/shim${EFI_ARCH}.efi.signed" \
+                "${ESP_DIR}/EFI/boot/boot${EFI_ARCH}.efi"
         fi
+
         # copying from vfat so ignore permissions
-        if [[ -n "${FLAGS_copy_efi_grub}" ]]; then
-            cp --no-preserve=mode "${ESP_DIR}/EFI/boot/grubx64.efi" \
+        if [[ -n ${FLAGS_copy_efi_grub} ]]; then
+            cp --no-preserve=mode "${ESP_DIR}/${GRUB_IMAGE}" \
                 "${FLAGS_copy_efi_grub}"
         fi
-        if [[ -n "${FLAGS_copy_shim}" ]]; then
-            cp --no-preserve=mode "${ESP_DIR}/EFI/boot/bootx64.efi" \
+        if [[ -n ${FLAGS_copy_shim} ]]; then
+            cp --no-preserve=mode "${ESP_DIR}/EFI/boot/boot${EFI_ARCH}.efi" \
                 "${FLAGS_copy_shim}"
         fi
         ;;
+    i386-pc)
+        info "Installing MBR and the BIOS Boot partition."
+        sudo cp "${GRUB_SRC}/boot.img" "${ESP_DIR}/${GRUB_DIR}"
+        sudo grub-bios-setup --device-map=/dev/null \
+            --directory="${ESP_DIR}/${GRUB_DIR}" "${LOOP_DEV}"
+        # boot.img gets manipulated by grub-bios-setup so it alone isn't
+        # sufficient to restore the MBR boot code if it gets corrupted.
+        sudo dd bs=448 count=1 status=none if="${LOOP_DEV}" \
+            of="${ESP_DIR}/${GRUB_DIR}/mbr.bin"
+        ;;
     x86_64-xen)
         info "Installing default x86_64 Xen bootloader."
-        sudo mkdir -p "${ESP_DIR}/xen" "${ESP_DIR}/boot/grub"
-        sudo mv "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
-            "${ESP_DIR}/xen/pvboot-x86_64.elf"
+        sudo mkdir -p "${ESP_DIR}/boot/grub"
         sudo cp "${BUILD_LIBRARY_DIR}/menu.lst" \
             "${ESP_DIR}/boot/grub/menu.lst"
         ;;
-    arm64-efi)
-        info "Installing default arm64 UEFI bootloader."
-        sudo mkdir -p "${ESP_DIR}/EFI/boot"
-        #FIXME(andrejro): shim not ported to aarch64
-        sudo mv "${ESP_DIR}/${GRUB_DIR}/${CORE_NAME}" \
-            "${ESP_DIR}/EFI/boot/bootaa64.efi"
-        if [[ -n "${FLAGS_copy_efi_grub}" ]]; then
-            # copying from vfat so ignore permissions
-            cp --no-preserve=mode "${ESP_DIR}/EFI/boot/bootaa64.efi" \
-                "${FLAGS_copy_efi_grub}"
-        fi
-        ;;
 esac
 
 cleanup

build_library/sbsign_util.sh

@@ -0,0 +1,55 @@
+# Copyright (c) 2024 The Flatcar Maintainers.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+if [[ ${COREOS_OFFICIAL:-0} -ne 1 ]]; then
+    SBSIGN_KEY="/usr/share/sb_keys/shim.key"
+    SBSIGN_CERT="/usr/share/sb_keys/shim.pem"
+else
+    SBSIGN_KEY="pkcs11:token=flatcar-dev-cert"
+    unset SBSIGN_CERT
+fi
+
+PKCS11_MODULE_PATH="/usr/$(get_sdk_libdir)/pkcs11/azure_kms_pkcs11.so"
+
+PKCS11_ENV=(
+    AZURE_KEYVAULT_URL="https://chewi-test.vault.azure.net/"
+    PKCS11_MODULE_PATH="${PKCS11_MODULE_PATH}"
+    AWS_KMS_PKCS11_DEBUG=1
+)
+
+get_sbsign_cert() {
+    if [[ ${SBSIGN_KEY} != pkcs11:* || -s ${SBSIGN_CERT} ]]; then
+        return
+    fi
+
+    SBSIGN_CERT=$(mktemp -t signing-cert.XXXXXXXXXX.pem)
+    info "Fetching ${SBSIGN_KEY} from Azure"
+
+    # Needs Key Vault Reader role.
+    env "${PKCS11_ENV[@]}" p11-kit export-object \
+        --provider "${PKCS11_MODULE_PATH}" \
+        "${SBSIGN_KEY};type=cert" \
+        | tee "${SBSIGN_CERT}"
+}
+
+cleanup_sbsign_certs() {
+    if [[ ${SBSIGN_CERT-} = "${TMPDIR-/tmp}"/* ]]; then
+        rm -f -- "${SBSIGN_CERT}"
+    fi
+}
+
+do_sbsign() {
+    get_sbsign_cert
+    info "Signing ${@:$#} with ${SBSIGN_KEY}"
+
+    if [[ ${SBSIGN_KEY} == pkcs11:* ]]; then
+        set -- --engine pkcs11 "${@}"
+    fi
+
+    # Needs Key Vault Crypto User role.
+    sudo env "${PKCS11_ENV[@]}" sbsign \
+        --key "${SBSIGN_KEY}" \
+        --cert "${SBSIGN_CERT}" \
+        "${@}"
+}