Re: [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux

From: Sean Christopherson
Date: Fri Jun 14 2019 - 16:06:12 EST

On Fri, Jun 14, 2019 at 10:53:39AM -0700, Sean Christopherson wrote:
> On Fri, Jun 14, 2019 at 10:45:56AM -0700, Sean Christopherson wrote:
> > The state tracking of #2/#3 doesn't scare me, it's purely the auditing.
> > Holding an audit message for an indeterminate amount of time is a
> > nightmare.
> >
> > Here's a thought. What if we simply require FILE__EXECUTE or AA_EXEC_MAP
> > to load any enclave page from a file? Alternatively, we could add an SGX
> > specific file policity, e.g. FILE__ENCLAVELOAD and AA_MAY_LOAD_ENCLAVE.
> > As in my other email, SELinux's W^X restrictions can be tied to the process,
> > i.e. they can be checked at mmap()/mprotect() without throwing a wrench in
> > auditing.
> We would also need to require VM_MAYEXEC on all enclave pages, or forego
> enforcing path_noexec() for enclaves.

Scratch that thought. Tying W^X restrictions to the process only works
if its done at load time. E.g. If process A maps a page W and process B
maps the same page X, then which process needs W^X depends on the order of
mmap()/mprotect() between the two processes.