T861: sign all Kernel modules with an ephemeral key

The shim review board (which is the secure boot base loader) recommends using
ephemeral keys when signing the Linux Kernel. This commit enables the Kernel
build system to generate a one-time ephemeral key that is used to:

* sign all build-in Kernel modules
* sign all other out-of-tree Kernel modules

The key lives in /tmp and is destroyed after the build container exits and is
named: "VyOS build time autogenerated kernel key".

In addition the Kernel now uses CONFIG_MODULE_SIG_FORCE. This now makes it
unable to load any Kernel Module to the image that is NOT signed by the
ephemeral key.

1 files changed, 7 insertions, 1 deletions

diff --git a/scripts/package-build/linux-kernel/build-openvpn-dco.sh b/scripts/package-build/linux-kernel/build-openvpn-dco.sh
index fd427825..518729ee 100755
--- a/scripts/package-build/linux-kernel/build-openvpn-dco.sh
+++ b/scripts/package-build/linux-kernel/build-openvpn-dco.sh
@@ -15,13 +15,19 @@ fi
 
 . ${KERNEL_VAR_FILE}
 
-cd ${SRC} && make KERNEL_SRC=$KERNEL_DIR
+cd ${SRC}
+git reset --hard HEAD
+git clean --force -d -x
+make KERNEL_SRC=$KERNEL_DIR
 
 # Copy binary to package directory
 DEBIAN_DIR=tmp/lib/modules/${KERNEL_VERSION}${KERNEL_SUFFIX}/extra
 mkdir -p ${DEBIAN_DIR}
 cp drivers/net/ovpn-dco/ovpn-dco-v2.ko ${DEBIAN_DIR}
 
+# Sign generated Kernel modules
+${CWD}/sign-modules.sh ${DEBIAN_DIR}
+
 # Build Debian Package
 fpm --input-type dir --output-type deb --name openvpn-dco \
     --version $(git describe | sed s/^v//) --deb-compression gz \