Re: [PATCH v39 15/24] x86/sgx: Add SGX_IOC_ENCLAVE_PROVISION

[Jarkko Sakkinen]

On Fri, Oct 23, 2020 at 04:23:55PM +0200, Jethro Beekman wrote:
> On 2020-10-23 12:17, Jarkko Sakkinen wrote:
> > On Tue, Oct 20, 2020 at 02:19:26PM -0700, Dave Hansen wrote:
> >> On 10/2/20 9:50 PM, Jarkko Sakkinen wrote:
> >>> + * Failure to explicitly request access to a restricted attribute will cause
> >>> + * sgx_ioc_enclave_init() to fail.  Currently, the only restricted attribute
> >>> + * is access to the PROVISION_KEY.
> >>
> >> Could we also justify why access is restricted, please?  Maybe:
> >>
> >> 	Access is restricted because PROVISION_KEY is burned uniquely
> >> 	into each each processor, making it a perfect unique identifier
> >> 	with privacy and fingerprinting implications.
> >>
> >> Are there any other reasons for doing it this way?
> > 
> > AFAIK, if I interperet the SDM correctl, PROVISION_KEY and
> > PROVISION_SEALING_KEY also have random salt added, i.e. they change
> > every boot cycle.
> > 
> > There is "RAND = yes" on those keys in Table 40-64 of Intel SDM volume
> > 3D :-)
> > 
> 
> This is nonsense. The whole point of sealing keys is that they don't
> change every boot. If did they they'd have no value over enclave
> memory. RAND means that the KEYID field from the KEYREQUEST is
> included in the derivation (as noted in the source row of the table
> you looked at).

I just looked that the column name is RAND, the row is called "Provision
key" and the cell has "Yes" in it.

> --
> Jethro Beekman | Fortanix

/Jarkko