This series intends to make the new SGX subsystem and the existing LSM architecture work together smoothly so that, say, SGX cannot be abused to work around restrictions set forth by LSM. This series applies on top of Jarkko Sakkinen's SGX series v20 (https://lkml.org/lkml/2019/4/17/344), where abundant details of this SGX/LSM problem could be found. This series is an alternative to Sean Christopherson's recent RFC series (https://lkml.org/lkml/2019/6/5/1070) that was trying to solve the same problem. The key problem is for LSM to determine the "maximal (most permissive) protection" allowed for individual enclave pages. Sean's approach is to take that from user mode code as a parameter of the EADD ioctl, validate it with LSM ahead of time, and then enforce it inside the SGX subsystem. The major disadvantage IMHO is that a priori knowledge of "maximal protection" is needed, but it isn't always available in certain use cases. In fact, it is an unusual approach to take "maximal protection" from user code, as what SELinux is doing today is to determine "maximal protection" of a vma using attributes associated with vma->vm_file instead. When it comes to enclaves, vma->vm_file always points /dev/sgx/enclave, so what's missing is a new way for LSM modules to remember origins of enclave pages so that they don't solely depend on vma->vm_file to determine "maximal protection". This series takes advantage of the fact that enclave pages cannot be remapped (to different linear address), therefore the pair of { vma->vm_file, linear_address } can be used to uniquely identify an enclave page. Then by notifying LSM on creation of every enclave page (via a new LSM hook - security_enclave_load), LSM modules would be able to track origin and protection changes of every page, hence be able to judge correctly upon mmap/mprotect requests. Cedric Xing (3): LSM/x86/sgx: Add SGX specific LSM hooks LSM/x86/sgx: Implement SGX specific hooks in SELinux LSM/x86/sgx: Call new LSM hooks from SGX subsystem arch/x86/kernel/cpu/sgx/driver/ioctl.c | 72 +++++- arch/x86/kernel/cpu/sgx/driver/main.c | 12 +- include/linux/lsm_hooks.h | 33 +++ include/linux/security.h | 26 +++ security/security.c | 21 ++ security/selinux/Makefile | 2 + security/selinux/hooks.c | 77 ++++++- security/selinux/include/intel_sgx.h | 18 ++ security/selinux/include/objsec.h | 3 + security/selinux/intel_sgx.c | 292 +++++++++++++++++++++++++ 10 files changed, 545 insertions(+), 11 deletions(-) create mode 100644 security/selinux/include/intel_sgx.h create mode 100644 security/selinux/intel_sgx.c -- 2.17.1
