On Sep 8, 2021, at 10:03 AM, Jarkko Sakkinen [off-list ref] wrote:

On Tue, 2021-09-07 at 12:00 -0400, Eric Snowberg wrote:

quoted

Many UEFI Linux distributions boot using shim.  The UEFI shim provides
what is called Machine Owner Keys (MOK).  Shim uses both the UEFI Secure
Boot DB and MOK keys to validate the next step in the boot chain.  The
MOK facility can be used to import user generated keys.  These keys can
be used to sign an end-user development kernel build.  When Linux boots,
pre-boot keys (both UEFI Secure Boot DB and MOK keys) get loaded in the
Linux .platform keyring.  

Currently, pre-boot keys are not trusted within the Linux trust boundary
[1]. These platform keys can only be used for kexec. If an end-user

What exactly is "trust boundary"? And what do you mean when you say that
Linux "trusts" something? AFAIK, software does not have feelings. Please,
just speak about exact things.

I am using terminology used previously by others when addressing this issue.  
If I should be using different terminology, please advise. The kernel does not 
trust pre-boot keys within it, meaning these pre-boot keys can not be used to 
validate items within the kernel. This is the “trust boundary”. Preboot keys are
on one side of the boundary, compiled-in keys are on the other.  MOK keys are 
pre-boot keys.  Currently they can not be used to validate things within the 
kernel itself (kernel modules, IMA keys, etc).