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build: gate firmware image signing behind SIGN_FIRMWARE

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Firmware image signing in append-metadata/append-gl-metadata was conditional
only by the presence of the build key. Add an explicit SIGN_FIRMWARE option
(default enabled except with BUILDBOT) so appending the fwtool signature can be
toggled on its own.

It's disable on buildbot since we use a decentralized building with no
individual keys on builders. Instead, a fake key is currently used, which adds
an insecure signature.

The future of signing firmware  and key distribution across the build
infrastructure should be discussed separately.

Link: https://github.com/openwrt/openwrt/pull/24291
Signed-off-by: Paul Spooren <mail@aparcar.org>
This commit is contained in:
Paul Spooren 2026-07-19 11:30:17 +02:00
parent 3ec398f0c3
commit ff41ddea1c
No known key found for this signature in database
2 changed files with 13 additions and 4 deletions
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9
config/Config-build.in
View file

@ -83,6 +83,15 @@ menu "Global build settings"
--allow-untrusted when installing self-compiled packages to a
firmware compiled by the same buildhost as public key matches.
config SIGN_FIRMWARE
bool "Cryptographically sign firmware images"
default n if BUILDBOT
default y
help
Append a signature to firmware images so that sysupgrade can verify
their authenticity before flashing. OpenWrt's build infrastructure
signs images with temporary keys; disabling this drops the signature.
comment "General build options"
config TESTING_KERNEL

8
include/image-commands.mk
View file

@ -91,12 +91,12 @@ metadata_json = \
define Build/append-metadata
$(if $(SUPPORTED_DEVICES),-echo $(call metadata_json) | fwtool -I - $@)
sha256sum "$@" | cut -d" " -f1 > "$@.sha256sum"
[ ! -s "$(BUILD_KEY)" -o ! -s "$(BUILD_KEY).ucert" -o ! -s "$@" ] || { \
$(if $(CONFIG_SIGN_FIRMWARE),[ ! -s "$(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 "$@.sig" ;\
fwtool -S "$@.ucert" "$@" ;\
}
})
endef
metadata_gl_json = \
@ -122,12 +122,12 @@ metadata_gl_json = \
define Build/append-gl-metadata
$(if $(SUPPORTED_DEVICES),-echo $(call metadata_gl_json,$(SUPPORTED_DEVICES)) | fwtool -I - $@)
sha256sum "$@" | cut -d" " -f1 > "$@.sha256sum"
[ ! -s "$(BUILD_KEY)" -o ! -s "$(BUILD_KEY).ucert" -o ! -s "$@" ] || { \
$(if $(CONFIG_SIGN_FIRMWARE),[ ! -s "$(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 "$@.sig" ;\
fwtool -S "$@.ucert" "$@" ;\
}
})
endef
define Build/append-teltonika-metadata