From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2DD04C31E44 for ; Tue, 11 Jun 2019 22:02:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0BD7A205ED for ; Tue, 11 Jun 2019 22:02:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390411AbfFKWCr (ORCPT ); Tue, 11 Jun 2019 18:02:47 -0400 Received: from mga03.intel.com ([134.134.136.65]:21062 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392014AbfFKWCr (ORCPT ); Tue, 11 Jun 2019 18:02:47 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Jun 2019 15:02:45 -0700 X-ExtLoop1: 1 Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.36]) by fmsmga006.fm.intel.com with ESMTP; 11 Jun 2019 15:02:44 -0700 Date: Tue, 11 Jun 2019 15:02:43 -0700 From: Sean Christopherson To: Stephen Smalley Cc: Cedric Xing , linux-security-module@vger.kernel.org, selinux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sgx@vger.kernel.org, jarkko.sakkinen@linux.intel.com, luto@kernel.org, jmorris@namei.org, serge@hallyn.com, paul@paul-moore.com, eparis@parisplace.org, jethro@fortanix.com, dave.hansen@intel.com, tglx@linutronix.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, nhorman@redhat.com, pmccallum@redhat.com, serge.ayoun@intel.com, shay.katz-zamir@intel.com, haitao.huang@intel.com, andriy.shevchenko@linux.intel.com, kai.svahn@intel.com, bp@alien8.de, josh@joshtriplett.org, kai.huang@intel.com, rientjes@google.com, william.c.roberts@intel.com, philip.b.tricca@intel.com Subject: Re: [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux Message-ID: <20190611220243.GB3416@linux.intel.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Tue, Jun 11, 2019 at 09:40:25AM -0400, Stephen Smalley wrote: > I haven't looked at this code closely, but it feels like a lot of > SGX-specific logic embedded into SELinux that will have to be repeated or > reused for every security module. Does SGX not track this state itself? SGX does track equivalent state. There are three proposals on the table (I think): 1. Require userspace to explicitly specificy (maximal) enclave page permissions at build time. The enclave page permissions are provided to, and checked by, LSMs at enclave build time. Pros: Low-complexity kernel implementation, straightforward auditing Cons: Sullies the SGX UAPI to some extent, may increase complexity of SGX2 enclave loaders. 2. Pre-check LSM permissions and dynamically track mappings to enclave pages, e.g. add an SGX mprotect() hook to restrict W->X and WX based on the pre-checked permissions. Pros: Does not impact SGX UAPI, medium kernel complexity Cons: Auditing is complex/weird, requires taking enclave-specific lock during mprotect() to query/update tracking. 3. Implement LSM hooks in SGX to allow LSMs to track enclave regions from cradle to grave, but otherwise defer everything to LSMs. Pros: Does not impact SGX UAPI, maximum flexibility, precise auditing Cons: Most complex and "heaviest" kernel implementation of the three, pushes more SGX details into LSMs. My RFC series[1] implements #1. My understanding is that Andy (Lutomirski) prefers #2. Cedric's RFC series implements #3. Perhaps the easiest way to make forward progress is to rule out the options we absolutely *don't* want by focusing on the potentially blocking issue with each option: #1 - SGX UAPI funkiness #2 - Auditing complexity, potential enclave lock contention #3 - Pushing SGX details into LSMs and complexity of kernel implementation [1] https://lkml.kernel.org/r/20190606021145.12604-1-sean.j.christopherson@intel.com