build: separate signing logic

This separates the options for signature creation and verification

* SIGNED_PACKAGES create Packages.sig
* SIGNED_IMAGES add ucert signature to created images
* CHECK_SIGNATURE add verification capabilities to images
* INSTALL_LOCAL_KEY add local key-build to /etc/opkg/keys

Right now the buildbot.git contains some hacks to create images that
have signature verification capabilities while not storing private keys
on buildbot slaves. This commit allows to disable these steps for the
buildbots and only perform signing on the master.

Signed-off-by: Paul Spooren <mail@aparcar.org>

config/Config-build.in

@@ -37,13 +37,21 @@ menu "Global build settings"
 		  - Enabling per-device rootfs support
 		  ...
 
+	config INSTALL_LOCAL_KEY
+		bool "Install local usign key into image"
+		default n
+
 	config SIGNED_PACKAGES
 		bool "Cryptographically signed package lists"
-		default y
+		default n
+
+	config SIGNED_IMAGES
+		bool "Cryptographically signed firmware images"
+		default n
 
 	config SIGNATURE_CHECK
 		bool "Enable signature checking in opkg"
-		default SIGNED_PACKAGES
+		default y
 
 	comment "General build options"
 

include/image-commands.mk

@@ -373,7 +373,10 @@ metadata_json = \
 
 define Build/append-metadata
 	$(if $(SUPPORTED_DEVICES),-echo $(call metadata_json,$(SUPPORTED_DEVICES)) | fwtool -I - $@)
-	[ ! -s "$(BUILD_KEY)" -o ! -s "$(BUILD_KEY).ucert" -o ! -s "$@" ] || { \
+	[ -z "$(SIGNED_IMAGES)" \
+		-o ! -s "$(BUILD_KEY)" \
+		-o ! -s "$(BUILD_KEY).ucert" \
+		-o ! -s "$@" ] || { \
 			cp "$(BUILD_KEY).ucert" "$@.ucert" ;\
 			usign -S -m "$@" -s "$(BUILD_KEY)" -x "$@.sig" ;\
 			ucert -A -c "$@.ucert" -x "$@.sig" ;\

package/base-files/Makefile

@@ -37,7 +37,7 @@ endif
 define Package/base-files
   SECTION:=base
   CATEGORY:=Base system
-  DEPENDS:=+netifd +libc +procd +jsonfilter +SIGNED_PACKAGES:usign +SIGNED_PACKAGES:openwrt-keyring +NAND_SUPPORT:ubi-utils +fstools +fwtool
+  DEPENDS:=+netifd +libc +procd +jsonfilter +SIGNATURE_CHECK:usign +SIGNATURE_CHECK:openwrt-keyring +NAND_SUPPORT:ubi-utils +fstools +fwtool
   TITLE:=Base filesystem for OpenWrt
   URL:=http://openwrt.org/
   VERSION:=$(PKG_RELEASE)-$(REVISION)
@@ -116,12 +116,6 @@ ifdef CONFIG_SIGNED_PACKAGES
 		$(STAGING_DIR_HOST)/bin/ucert -I -c $(BUILD_KEY).ucert -p $(BUILD_KEY).pub -s $(BUILD_KEY)
 
   endef
-
-  define Package/base-files/install-key
-	mkdir -p $(1)/etc/opkg/keys
-	$(CP) $(BUILD_KEY).pub $(1)/etc/opkg/keys/`$(STAGING_DIR_HOST)/bin/usign -F -p $(BUILD_KEY).pub`
-
-  endef
 endif
 
 ifeq ($(CONFIG_NAND_SUPPORT),)
@@ -130,9 +124,16 @@ ifeq ($(CONFIG_NAND_SUPPORT),)
   endef
 endif
 
+ifdef CONFIG_INSTALL_LOCAL_KEY
+  define Package/base-files/install-local-key
+	mkdir -p $(1)/etc/opkg/keys
+	$(CP) $(BUILD_KEY).pub $(1)/etc/opkg/keys/`$(STAGING_DIR_HOST)/bin/usign \
+		-F -p $(BUILD_KEY).pub`
+endef
+
 define Package/base-files/install
 	$(CP) ./files/* $(1)/
-	$(Package/base-files/install-key)
+	$(Package/base-files/install-local-key)
 	$(Package/base-files/nand-support)
 	if [ -d $(GENERIC_PLATFORM_DIR)/base-files/. ]; then \
 		$(CP) $(GENERIC_PLATFORM_DIR)/base-files/* $(1)/; \