[PATCH v10 10/15] FWU: Add support for the FWU Multi Bank Update feature

[Jassi Brar]

Hi Ilias,

On Mon, Oct 3, 2022 at 7:21 AM Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Hi Jassi,
>
> On Wed, Sep 28, 2022 at 10:16:53AM -0500, Jassi Brar wrote:
> > Hi Etienne,
> >
> > On Wed, Sep 28, 2022 at 2:30 AM Etienne Carriere
> > <etienne.carriere at linaro.org> wrote:
> > > Hello Jassi, Sughosh and all,
> > >
> > >  >>> But a malicious user may force some old vulnerable image back into use
> > >  >>> by updating all but that image.
> > >
> > > When the system boots with accepted images (referring to fwu-mdata
> > > regular/trial state), the platform monotonic counter is updated
> > > against booted image version number if needed, preventing older images
> > > to be booted when an accepted image has been deployed.
> > > @Jassi, does this answer your question?
> > >
> > As I said in my earlier post, I know we can employ security+integrity
> > techniques to prevent such misuse.
> > My point is FWU should still be implemented assuming no such technique
> > might be available due to any reason, and we do the best we can. Just
> > as we don't say lets not care about buffer-overflow vulnerabilities
> > because the system can implement secure boot and other such
> > techniques.
> >
> > For example, the spec warns : "The metadata can be maliciously
> > crafted, it should be treated as an insecure information source." So
> > clearly the spec doesn't count on rollback and authentication
> > mechanisms to be always available - and that is how it should be.
>
> We've discussed this extensively during drafting the spec.  You are right
> that we would be better off trying to protect the fwu metadata somehow.  In
> fact Heinrich had similar concerns when the original RFC was posted.  i
>
Actually I never said we should protect the metadata.
If you read the whole thread, the point was that we should try to
protect against partial bank updates - accidental or malicious. We can
not assume a user updating only partially, knows what they are doing.

cheers.