Merge pull request #20858 from benpicco/suit_multi_key-2

makefiles/suit: store public keys, make it easier to work with multiple keys

makefiles/suit.base.inc.mk

@@ -6,10 +6,14 @@ SUIT_TOOL ?= $(RIOTBASE)/dist/tools/suit/suit-manifest-generator/bin/suit-tool
 # SUIT encryption keys
 #
 
-# Specify key to use.
+# Specify key(s) to use.
 # Will use $(SUIT_KEY_DIR)/$(SUIT_KEY).pem as combined private/public key
 # files.
+# Multiple keys can be specified, that means that the firmware will accept
+# updates signed with either one of those keys.
+# If the firmware accepts multiple keys, let the first key be the signing key.
 SUIT_KEY ?= default
+SUIT_KEY_SIGN ?= $(word 1, $(SUIT_KEY))
 XDG_DATA_HOME ?= $(HOME)/.local/share
 
 ifeq (1, $(RIOT_CI_BUILD))
@@ -18,39 +22,60 @@ else
   SUIT_KEY_DIR ?= $(XDG_DATA_HOME)/RIOT/keys
 endif
 
-SUIT_SEC ?= $(SUIT_KEY_DIR)/$(SUIT_KEY).pem
+# we may accept multiple keys for the firmware
+SUIT_SEC ?= $(foreach item,$(SUIT_KEY),$(SUIT_KEY_DIR)/$(item).pem)
+# but there can only be one signing key
+SUIT_SEC_SIGN ?= $(SUIT_KEY_DIR)/$(SUIT_KEY_SIGN).pem
 
-# Multiple keys can be specified with "key0:pw0 key1:pw1 …" (pw may be empty)
-SUIT_SECS ?= $(SUIT_SEC):$(SUIT_SEC_PASSWORD)
+# generate a list of the public keys
+SUIT_PUBS ?= $(SUIT_SEC:.pem=.pem.pub)
 
 SUIT_PUB_HDR = $(BINDIR)/riotbuild/public_key.h
 SUIT_PUB_HDR_DIR = $(dir $(SUIT_PUB_HDR))
 CFLAGS += -I$(SUIT_PUB_HDR_DIR)
 BUILDDEPS += $(SUIT_PUB_HDR)
 
+# OpenSSL leaves an empty file if key generation fails - remove it manually
+# see https://github.com/openssl/openssl/issues/25440
 $(SUIT_SEC): | $(CLEAN)
 	$(Q)echo suit: generating key in $(SUIT_KEY_DIR)
 	$(Q)mkdir -p $(SUIT_KEY_DIR)
-	$(Q)$(RIOTBASE)/dist/tools/suit/gen_key.py $(SUIT_SEC) $(SUIT_SEC_PASSWORD)
+	$(Q)(										\
+	printf "0) none\n";								\
+	printf "1) aes-256-cbc\n";							\
+	printf "Choose encryption for key file $@: ";					\
+	if [ -z "$(RIOT_CI_BUILD)" ]; then read encryption; else encryption=0; fi;	\
+	case $$encryption in								\
+		0)									\
+			openssl genpkey -algorithm ed25519 -out $@;			\
+			;;								\
+		1)									\
+			openssl genpkey -algorithm ed25519 -aes-256-cbc -out $@ || :;	\
+			;;								\
+		*)									\
+			echo "Invalid choice";						\
+			exit 1;								\
+			;;								\
+	esac;										\
+	)
+	$(Q)if [ ! -s $@ ]; then rm $@; fi
 
+%.pem.pub: %.pem
+	$(Q)openssl ec -inform pem -in $< -outform pem -pubout -out $@
+
+# Convert public keys to C headers - only last 32 bytes are key material
+#
 # set FORCE so switching between keys using "SUIT_KEY=foo make ..."
 # triggers a rebuild even if the new key would otherwise not (because the other
 # key's mtime is too far back).
-$(SUIT_PUB_HDR): $(SUIT_SEC) FORCE | $(CLEAN)
+$(SUIT_PUB_HDR): $(SUIT_PUBS) FORCE | $(CLEAN)
 	$(Q)mkdir -p $(SUIT_PUB_HDR_DIR)
 	$(Q)(							\
 		echo "const uint8_t public_key[][32] = {";	\
-		for i in $(SUIT_SECS); do			\
-			key=$${i%:*};				\
-			pw=$${i#*:};				\
-			if [ "$$key" = "$$pw" ]; then		\
-				unset pw;			\
-			fi;					\
-			if [ -z "$$pw" ]; then			\
-				$(SUIT_TOOL) pubkey -f header -k $$key; \
-			else					\
-				$(SUIT_TOOL) pubkey -f header -k $$key -p $$pw; \
-			fi					\
+		for i in $(SUIT_PUBS); do			\
+			echo " {";				\
+			openssl ec -inform pem -pubin -in $$i -outform der | tail -c 32 | xxd -i; \
+			echo " },";				\
 		done;						\
 		echo "};"					\
 	) | '$(LAZYSPONGE)' $(LAZYSPONGE_FLAGS) '$@'

makefiles/suit.inc.mk

@@ -32,6 +32,10 @@ SUIT_MANIFEST_SIGNED_LATEST ?= $(BINDIR_SUIT)/$(SUIT_MANIFEST_BASENAME).latest.b
 SUIT_NOTIFY_VERSION ?= latest
 SUIT_NOTIFY_MANIFEST ?= $(SUIT_MANIFEST_BASENAME).$(SUIT_NOTIFY_VERSION).bin
 
+ifneq (,$(SUIT_SEC_PASSWORD))
+  SUIT_TOOL_ARGS += -p $(SUIT_SEC_PASSWORD)
+endif
+
 # Long manifest names require more buffer space when parsing
 export CFLAGS += -DCONFIG_SOCK_URLPATH_MAXLEN=128
 export CFLAGS += -DSUIT_VENDOR_DOMAIN="\"$(SUIT_VENDOR)\""
@@ -54,7 +58,7 @@ $(SUIT_MANIFEST): $(SUIT_MANIFEST_PAYLOADS) $(BINDIR_SUIT)
 	$(Q)rm -f $@.tmp
 
 $(SUIT_MANIFEST_SIGNED): $(SUIT_MANIFEST) $(SUIT_SEC)
-	$(Q)$(SUIT_TOOL) sign $(SUIT_TOOL_ARGS) -k $(SUIT_SEC) -m $(SUIT_MANIFEST) -o $@
+	$(Q)$(SUIT_TOOL) sign $(SUIT_TOOL_ARGS) -k $(SUIT_SEC_SIGN) -m $(SUIT_MANIFEST) -o $@
 
 $(SUIT_MANIFEST_LATEST): $(SUIT_MANIFEST)
 	$(Q)ln -f -s $< $@