Re: [PATCH v4 1/3] efi/libstub: Copy confidential computing secret area

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Oct 20, 2021 at 08:00:28AM -0400, James Bottomley wrote:
> On Wed, 2021-10-20 at 08:39 +0200, Greg KH wrote:
> > On Wed, Oct 20, 2021 at 06:14:06AM +0000, Dov Murik wrote:
> [...]
> > > +	help
> > > +	  Copy memory reserved by EFI for Confidential Computing (coco)
> > > +	  injected secrets, if EFI exposes such a table entry.
> > 
> > Why would you want to "copy" secret memory?
> > 
> > This sounds really odd here, it sounds like you are opening up a
> > security hole.  Are you sure this is the correct text that everyone
> > on the "COCO" group agrees with?
> 
> The way this works is that EFI covers the secret area with a boot time
> handoff block, which means it gets destroyed as soon as
> ExitBootServices is called as a security measure ... if you do nothing
> the secret is shredded.  This means you need to make a copy of it
> before that happens if there are secrets that need to live beyond the
> EFI boot stub.

Ok, but "copy secrets" does sound really odd, so you all need a much
better description here, and hopefully somewhere else in Documentation/
to describe exactly what this new API is and is to be used for.

Otherwise I read this as "hey a backdoor to read the secrets I wasn't
supposed to be able to see!"

thanks,

greg k-h