[RFC PATCH v4 10/12] security/selinux: Add enclave_load() implementation

[Stephen Smalley]

On 6/21/19 5:22 PM, Xing, Cedric wrote:
>> From: Christopherson, Sean J
>> Sent: Wednesday, June 19, 2019 3:24 PM
>>
>> Intended use of each permission:
>>
>>    - SGX_EXECDIRTY: dynamically load code within the enclave itself
>>    - SGX_EXECUNMR: load unmeasured code into the enclave, e.g. Graphene
> 
> Why does it matter whether a code page is measured or not?

It won't be incorporated into an attestation?

> 
>>    - SGX_EXECANON: load code from anonymous memory (likely Graphene)
> 
> Graphene doesn't load code from anonymous memory. It loads code dynamically though, as in SGX_EXECDIRTY case.

So do we expect EXECANON to never be triggered at all?

> 
>>    - SGX_EXECUTE: load an enclave from a file, i.e. normal behavior
> 
> Why is SGX_EXECUTE needed from security perspective? Or why isn't FILE__EXECUTE sufficient?

Splitting the SGX permissions from the regular ones allows distinctions 
to be made between what can be executed in the host process and what can 
be executed in the enclave.  The host process may be allowed 
FILE__EXECUTE to numerous files that do not contain any code ever 
intended to be executed within the enclave.