On Sun, Apr 26, 2020 at 11:57:53AM -0500, Dr. Greg wrote: > In closing, it is important to note that the proposed SGX driver is > not available as a module. This effectively excludes any alternative > implementations of the driver without replacement of the kernel at > large. No it doesn't. The SGX subsytem won't allocate EPC pages unless userspace creates an enclave, i.e. preventing unprivileged userspace from accessing /dev/sgx/enclave will allow loading an alternative out-of-tree SGX module. Yes, SGX sanitizes the EPC on boot, but that's arguably a good thing for out-of-tree modules. And if you want to get crafty and squash in-kernel SGX altogether, boot with "clearcpuid=<SGX_LC>" and/or "clearcpuid=<SGX>" to disable in-kernel support entirely. SGX won't be correctly enumerated in /proc/cpuinfo relative to the existence of an out-of-tree module, but that seems like a very minor issue if you're running with a completely different SGX driver. > It also means that any platform, with SGX hardware support, > running a kernel with this driver, has the potential for the > security/privacy issues noted above. Unless I'm mistaken, /dev/sgx is root-only by default. There are far scarier mechanisms available to root for hosing the system. > If key based policy management is not allowed, then the driver needs > to be re-architected to have modular support so that alternative > implementations or the absence of any driver support are at least > tenable. As above, using an alternative implementation is teneble, albeit a bit kludgy.
