security/intel/cbnt: Add an option to generate an unsigned KM
This is useful if you have external infrastructure to sign KM.
Change-Id: If5e9306366230b75d97e4e1fb271bcd7615abd5f
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51572
Reviewed-by: Christian Walter <christian.walter@9elements.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/security/intel/cbnt/Kconfig b/src/security/intel/cbnt/Kconfig
index 0f4c216..6142a24 100644
--- a/src/security/intel/cbnt/Kconfig
+++ b/src/security/intel/cbnt/Kconfig
@@ -20,12 +20,25 @@
bool "Generate Key Manifest (KM)"
default y
select INTEL_CBNT_NEED_KM_PUB_KEY
- select INTEL_CBNT_NEED_KM_PRIV_KEY
+ select INTEL_CBNT_NEED_KM_PRIV_KEY if !INTEL_CBNT_KM_ONLY_UNSIGNED
select INTEL_CBNT_NEED_BPM_PUB_KEY if !INTEL_CBNT_BG_PROV_KM_USE_CFG_FILE
help
Select y to generate the Key Manifest (KM).
Select n to include a KM binary.
+config INTEL_CBNT_KM_ONLY_UNSIGNED
+ bool "Only unsigned key manifest (KM)"
+ depends on INTEL_CBNT_GENERATE_KM
+ help
+ Skip signing the KM.
+ The resulting unsigned KM will be placed at build/km_unsigned.bin.
+ The resulting coreboot image will not be functional with CBnT.
+ After the unsigned KM is signed externally you can either rebuild
+ coreboot using that binary or add it to cbfs and fit:
+ "$ cbfstool build/coreboot.rom add -f km.bin -n key_manifest.bin -t raw -a 16"
+ "$ ifittool -r COREBOOT -a -n key_manifest.bin -t 11 -s 12 -f build/coreboot.rom"
+ '-s 12' where 12 is CONFIG_CPU_INTEL_NUM_FIT_ENTRIES.
+
config INTEL_CBNT_BG_PROV_KM_USE_CFG_FILE
bool "KM: use a CBnT json config file"
depends on INTEL_CBNT_GENERATE_KM
diff --git a/src/security/intel/cbnt/Makefile.inc b/src/security/intel/cbnt/Makefile.inc
index 62b12f0..eae3079 100644
--- a/src/security/intel/cbnt/Makefile.inc
+++ b/src/security/intel/cbnt/Makefile.inc
@@ -71,6 +71,19 @@
endif
ifneq ($(KM_FILE),"")
+ifeq ($(CONFIG_INTEL_CBNT_KM_ONLY_UNSIGNED),y)
+$(call add_intermediate, gen_unsigned_km, $(obj)/km_unsigned.bin)
+ @printf "Generating unsgined KM\n"
+
+build_complete::
+ @printf "\n** WARNING **\n"
+ @printf "Build generated an unsigned KM image: build/km_unsiged.bin.\n"
+ @printf "The resulting image will not work with CBnT.\n"
+ @printf "After you have externally signed the image you can add it to the coreboot image:\n"
+ @printf "$$ cbfstool build/coreboot.rom add -f km.bin -n key_manifest.bin -t raw -a 16\n"
+ @printf "$$ ifittool -r COREBOOT -a -n key_manifest.bin -t 11 -s 12 -f build/coreboot.rom\n"
+
+else
cbfs-files-y += key_manifest.bin
key_manifest.bin-file := $(KM_FILE)
key_manifest.bin-type := raw
@@ -80,4 +93,5 @@
$(IFITTOOL) -r COREBOOT -a -n key_manifest.bin -t 11 -s $(CONFIG_CPU_INTEL_NUM_FIT_ENTRIES) -f $<
endif
+endif # CONFIG_INTEL_CBNT_KM_ONLY_UNSIGNED
endif # CONFIG_INTEL_CBNT_SUPPORT