CPUSecurity [FreeBSD WIKI]

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**Session Leader:** emaste

**Notes:** https://hackmd.io/oZVxl9w7RkSMZmXow_3Gig (content has been migrated to this page)

====== CPU Security ======
===== Architectural Security Features =====
  * SGX
    * Ruslan update
    * theraven: having paging support in %%FreeBSD%% is useful
    * GELI
    * QEMU, hardware in test cluster perhaps
  * MKTME - per-page-table encryption
    * https://lwn.net/Articles/758313/
    * and AMD equivalent
  * TPM support
    * libtrousers
  * IBT (Indirect Branch Tracking)
    * toolchain support: available for amd64 today
    * amd64 requires kernel support for alternate permission bits (not in PTEs)
  * Shadow Stack
    * breaks retpoline
    * Google thing: xor RA with stack pointer
  * Pointer Authentication (Arm)
    * http://events17.linuxfoundation.org/sites/events/files/slides/slides_23.pdf
    * ARMv8.3-A paciasp autiasp
    * PAC in previously reserved bits (e.g. 7 or 15 bits)
    * auth failure results in invalid pointer (non-canonical)
    * Clang support state unknown
    * subset are in nop space on previous
    * Linux using for PLTGOT
    * Return address protection
    * can use return address as stack canary
  * PXN, UXN, PAN, SMAP, SMEP
    * arm64, amd64 - believe done?
    * RISC-V not yet
    * POWER ???
  * IOMMU use
    * who will do it?
  * Tagged pointers
    * research area
    * software implementations - high overhead
    * may appear in llvm
  * CHERI
    * how do we promote the knowledge that pointers are not integers?
    * type-aware copyin/copyout ; clang-generated marshal/unmarshal code

===== Speculative Execution =====
  * RH talk - static analysis
  * smatch - some support for finding v1 gadgets
  * Clang SLH http://llvm.org/docs/SpeculativeLoadHardening.html

===== Policy Questions =====
  * How do we ensure this actually gets used?
    * e.g. GELI TPM
    * ssh-agent
  * shipping kernel modules as LLVM IR?
  * Windows virtualization based security
    * hyper-v enclaves
    * virtual TPM

===== Vulnerability Mitigations =====
  * Kernel memory permissions
    * kernel segments done for amd64, needs to be done for everything else
    * kernel modules
      * fairly straightforward
      * mips, amd64 use .o, everything else .so
    * opportunity to find RW memory that could be demoted to RO
  * W^X
  * ASLR