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, 12 insertions, 0 deletions

diff --git a/packages/linux-kernel/build-mellanox-ofed.sh b/packages/linux-kernel/build-mellanox-ofed.sh
index a157ee61..3f8a50f0 100755
--- a/packages/linux-kernel/build-mellanox-ofed.sh
+++ b/packages/linux-kernel/build-mellanox-ofed.sh
@@ -117,6 +117,18 @@ cp $(find $CWD/$DRIVER_DIR/DEBS/$DEB_DISTRO -type f | grep '\.deb$') "$CWD/"
 
 echo "I: Cleanup ${DRIVER_NAME} source"
 cd ${CWD}
+
+# Sign modules
+DEB_NAME=$(ls mlnx-ofed-kernel-modules_*)
+TMP_DIR="tmp-ofed-sign"
+dpkg-deb --raw-extract ${DEB_NAME} ${TMP_DIR}
+# Sign generated Kernel modules
+${CWD}/sign-modules.sh ${TMP_DIR}
+# Cleanup and repack DEB
+rm -f ${DEB_NAME}
+dpkg-deb --build ${TMP_DIR} ${DEB_NAME}
+rm -rf ${TMP_DIR}
+
 if [ -f ${DRIVER_FILE} ]; then
     rm -f ${DRIVER_FILE}
 fi