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.
This adds support for UEFI Secure Boot. It adds the missing pieces to the Linux
Kernel and enforces module signing. This results in an additional security
layer where untrusted (unsigned) Kernel modules can no longer be loaded into
the live system.
NOTE: This commit will not work unless signing keys are present. Arbitrary
keys can be generated using instructions found in:
data/live-build-config/includes.chroot/var/lib/shim-signed/mok/README.md
