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

On 2020-10-23 12:17, Jarkko Sakkinen wrote:

On Tue, Oct 20, 2020 at 02:19:26PM -0700, Dave Hansen wrote:

quoted

On 10/2/20 9:50 PM, Jarkko Sakkinen wrote:

quoted

+ * 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).

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Jethro Beekman | Fortanix