linux-kernel - Re: [PATCH v39 15/24] x86/sgx: Add SGX_IOC_ENCLAVE

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Date:   Fri, 23 Oct 2020 13:17:36 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     x86@...nel.org, linux-sgx@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Jethro Beekman <jethro@...tanix.com>,
        Darren Kenny <darren.kenny@...cle.com>,
        Andy Lutomirski <luto@...nel.org>, akpm@...ux-foundation.org,
        andriy.shevchenko@...ux.intel.com, asapek@...gle.com, bp@...en8.de,
        cedric.xing@...el.com, chenalexchen@...gle.com,
        conradparker@...gle.com, cyhanish@...gle.com,
        haitao.huang@...el.com, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, nhorman@...hat.com,
        npmccallum@...hat.com, puiterwijk@...hat.com, rientjes@...gle.com,
        sean.j.christopherson@...el.com, tglx@...utronix.de,
        yaozhangx@...gle.com, mikko.ylinen@...el.com
Subject: Re: [PATCH v39 15/24] x86/sgx: Add SGX_IOC_ENCLAVE_PROVISION

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 :-)

/Jarkko