On Wed, May 15, 2019 at 01:35:31PM +0300, Jarkko Sakkinen wrote: > On Tue, May 14, 2019 at 01:45:27PM -0700, Sean Christopherson wrote: > > On Tue, May 14, 2019 at 08:13:36AM -0700, Andy Lutomirski wrote: > > > I think it's as simple as requiring that, if SECINFO.X is set, then > > > the src pointer points to the appropriate number of bytes of > > > executable memory. (Unless there's some way for an enclave to change > > > SECINFO after the fact -- is there?) > > > > Nit: SECINFO is just the struct passed to EADD, I think what you're really > > asking is "can the EPCM permissions be changed after the fact". > > > > And the answer is, yes. > > > > On SGX2 hardware, the enclave can extend the EPCM permissions at runtime > > via ENCLU[EMODPE], e.g. to make a page writable. > > Small correction: it is EMODPR. No, I'm referring to EMODPE, note the ENCLU classification. > Anyway, it is good to mention that these would require EACCEPT from the > enclave side. In order to take advantage of this is in a malicous > enclave, one would require SELinux/IMA/whatnot policy to have permitted > it in the first place. EMODPE doesn't require EACCEPT or any equivalent from the kernel. As you alluded to, the page tables would still need to allow PROT_EXEC. I was simply trying to answer Andy's question regarding SECINFO. > Thus, it cannot be said that it breaks the security policy if this would > happen because policy has allowed to use the particular enclave.
