Re: [PATCH v33 12/21] x86/sgx: Allow a limited use of ATTRIBUTE.PROVISIONKEY for attestation

Jarkko Sakkinen
2020-07-03T02:32:30Z

On Mon, Jun 29, 2020 at 06:02:42PM +0200, Borislav Petkov wrote:
> On Thu, Jun 18, 2020 at 01:08:34AM +0300, Jarkko Sakkinen wrote:
> > Provisioning Certification Enclave (PCE), the root of trust for other
> > enclaves, generates a signing key from a fused key called Provisioning
> > Certification Key. PCE can then use this key to certify an attestation key
> > of a QE, e.g. we get the chain of trust down to the hardware if the Intel
>
> What's a QE?
>
> I don't see this acronym resolved anywhere in the whole patchset.

Quoting Enclave.

>
> > signed PCE is used.
> >
> > To use the needed keys, ATTRIBUTE.PROVISIONKEY is required but should be
> > only allowed for those who actually need it so that only the trusted
> > parties can certify QE's.
> >
> > Obviously the attestation service should know the public key of the used
> > PCE and that way detect illegit attestation, but whitelisting the legit
> > users still adds an additional layer of defence.
> >
> > Add new device file called /dev/sgx/provision. The sole purpose of this
> > file is to provide file descriptors that act as privilege tokens to allow
> > to build enclaves with ATTRIBUTE.PROVISIONKEY set. A new ioctl called
> > SGX_IOC_ENCLAVE_SET_ATTRIBUTE is used to assign this token to an enclave.
>
> So I'm sure I'm missing something here: what controls which
> enclave can open /dev/sgx/provision and thus pass the FD to
> SGX_IOC_ENCLAVE_SET_ATTRIBUTE?
>
> And in general, how does that whole flow look like: what calls
> SGX_IOC_ENCLAVE_SET_ATTRIBUTE when?

I've documented it in the Remote Attestation section:

https://github.com/jsakkine-intel/linux-sgx/blob/master/Documentation/x86/sgx.rst

/Jarkko