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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham 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 AF759C31E4B for ; Fri, 14 Jun 2019 17:45:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 80782217D6 for ; Fri, 14 Jun 2019 17:45:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726632AbfFNRp6 (ORCPT ); Fri, 14 Jun 2019 13:45:58 -0400 Received: from mga14.intel.com ([192.55.52.115]:53669 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726082AbfFNRp5 (ORCPT ); Fri, 14 Jun 2019 13:45:57 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Jun 2019 10:45:56 -0700 X-ExtLoop1: 1 Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.36]) by orsmga008.jf.intel.com with ESMTP; 14 Jun 2019 10:45:56 -0700 Date: Fri, 14 Jun 2019 10:45:56 -0700 From: Sean Christopherson To: "Xing, Cedric" Cc: Stephen Smalley , "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" , "Hansen, Dave" , "tglx@linutronix.de" , "torvalds@linux-foundation.org" , "akpm@linux-foundation.org" , "nhorman@redhat.com" , "pmccallum@redhat.com" , "Ayoun, Serge" , "Katz-zamir, Shay" , "Huang, Haitao" , "andriy.shevchenko@linux.intel.com" , "Svahn, Kai" , "bp@alien8.de" , "josh@joshtriplett.org" , "Huang, Kai" , "rientjes@google.com" , "Roberts, William C" , "Tricca, Philip B" Subject: Re: [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux Message-ID: <20190614174556.GJ12191@linux.intel.com> References: <20190611220243.GB3416@linux.intel.com> <8d99d8fb-a921-286a-8cf0-cd522e09b37c@tycho.nsa.gov> <20190614004600.GF18385@linux.intel.com> <960B34DE67B9E140824F1DCDEC400C0F65504665@ORSMSX116.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <960B34DE67B9E140824F1DCDEC400C0F65504665@ORSMSX116.amr.corp.intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On Fri, Jun 14, 2019 at 10:16:55AM -0700, Xing, Cedric wrote: > > From: Christopherson, Sean J > > Sent: Thursday, June 13, 2019 5:46 PM > > > > On Thu, Jun 13, 2019 at 01:02:17PM -0400, Stephen Smalley wrote: > > > On 6/11/19 6:02 PM, Sean Christopherson wrote: > > > >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.christopherso > > > >n@intel.com > > > > > > Given the complexity tradeoff, what is the clear motivating example > > > for why > > > #1 isn't the obvious choice? That the enclave loader has no way of > > > knowing a priori whether the enclave will require W->X or WX? But > > > aren't we better off requiring enclaves to be explicitly marked as > > > needing such so that we can make a more informed decision about > > > whether to load them in the first place? > > > > Andy and/or Cedric, can you please weigh in with a concrete (and > > practical) use case that will break if we go with #1? The auditing > > issues for #2/#3 are complex to say the least... > > How does enclave loader provide per-page ALLOW_* flags? Unchanged from my RFC, i.e. specified at SGX_IOC_ENCLAVE_ADD_PAGE(S). > And a related question is why they are necessary for enclaves but > unnecessary for regular executables or shared objects. Because at mmap()/mprotect() time we don't have the source file of the enclave page to check SELinux's FILE__EXECUTE or AppArmor's AA_EXEC_MMAP. > What's the story for SGX2 if mmap()'ing non-existing pages is not allowed? Userspace will need to invoke an ioctl() to tell SGX "this range can be EAUG'd". > > What's the story for auditing? It happens naturally when security_enclave_load() is called. Am I missing something? > After everything above has been taken care of properly, will #1 still be > simpler than #2/#3? The state tracking of #2/#3 doesn't scare me, it's purely the auditing. Holding an audit message for an indeterminate amount of time is a nightmare. Here's a thought. What if we simply require FILE__EXECUTE or AA_EXEC_MAP to load any enclave page from a file? Alternatively, we could add an SGX specific file policity, e.g. FILE__ENCLAVELOAD and AA_MAY_LOAD_ENCLAVE. As in my other email, SELinux's W^X restrictions can be tied to the process, i.e. they can be checked at mmap()/mprotect() without throwing a wrench in auditing.