Re: [PATCH v20 00/28] Intel SGX1 support

[Jarkko Sakkinen]

On Thu, May 16, 2019 at 08:07:05AM +0300, Jarkko Sakkinen wrote:
> On Wed, May 15, 2019 at 07:27:02AM -0700, Andy Lutomirski wrote:
> > 
> > > On May 15, 2019, at 4:00 AM, Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> > > 
> > >> On Wed, May 15, 2019 at 01:35:31PM +0300, Jarkko Sakkinen wrote:
> > >> This brings me to an open question in Andy's model: lets say that we
> > >> change the source for SIGSTRUCT from memory address to fd. How can the
> > >> policy prevent the use not creating a file containing a SIGSTRUCT and
> > >> passing fd of that to the EINIT ioctl?
> > > 
> > 
> > The policy will presumably check the label on the file that the fd points to.
> 
> Right (checked SELinux documentation).
> 
> Got one idea from this. Right now creation and initialization does not
> require any VMAs to be created (since v20). Requiring to map a VMA for
> copying the data would bring in my opinion a glitch to this model that
> we have done effort to build up.
> 
> What if we similarly change EADD ioctl in a way that it'd take an fd
> and an offset? This way we can enforce policy to the source where the
> enclave data is loaded from. On the other hand, loading SIGSTRUCT from
> fd enforces a legit structure for the enclave.
> 
> This would still allow to construct enclaves in VMA independent way.

The API would turn into this:

/**
 * struct sgx_enclave_add_page - parameter structure for the
 *                               %SGX_IOC_ENCLAVE_ADD_PAGE ioctl
 * @fd:		file containing the page data
 * @offset:	offset in the file containing the page data
 * @secinfo:	address for the SECINFO data
 * @mrmask:	bitmask for the measured 256 byte chunks
 */
struct sgx_enclave_add_page {
	__u64	fd;
	__u64	offset;
	__u64	secinfo;
	__u16	mrmask;
} __attribute__((__packed__));


/**
 * struct sgx_enclave_init - parameter structure for the
 *                           %SGX_IOC_ENCLAVE_INIT ioctl
 * @fd:		file containing the sigstruct
 * @offset:	offset in the file containing the sigstruct
 */
struct sgx_enclave_init {
	__u64	fd;
	__u64	offset;
};

/Jarkko