From: Andy Lutomirski <luto@kernel.org> To: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Andy Lutomirski <luto@kernel.org>, Stephen Smalley <sds@tycho.nsa.gov>, Cedric Xing <cedric.xing@intel.com>, LSM List <linux-security-module@vger.kernel.org>, selinux@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>, linux-sgx@vger.kernel.org, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>, James Morris <jmorris@namei.org>, "Serge E. Hallyn" <serge@hallyn.com>, Paul Moore <paul@paul-moore.com>, Eric Paris <eparis@parisplace.org>, Jethro Beekman <jethro@fortanix.com>, Dave Hansen <dave.hansen@intel.com>, Thomas Gleixner <tglx@linutronix.de>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, nhorman@redhat.com, pmccallum@redhat.com, "Ayoun, Serge" <serge.ayoun@intel.com>, "Katz-zamir, Shay" <shay.katz-zamir@intel.com>, "Huang, Haitao" <haitao.huang@intel.com>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, "Svahn, Kai" <kai.svahn@intel.com>, Borislav Petkov <bp@alien8.de>, Josh Triplett <josh@joshtriplett.org>, "Huang, Kai" <kai.huang@intel.com>, David Rientjes <rientjes@google.com>, "Roberts, William C" <william.c.roberts@intel.com>, Philip Tricca <philip.b.tricca@intel.com> Subject: Re: [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux Date: Mon, 17 Jun 2019 10:08:26 -0700 Message-ID: <CALCETrW9Mt70UY3NWGQq3rpxCxSpR4GfsBgt0jTib3bNDMTXkw@mail.gmail.com> (raw) In-Reply-To: <20190617164915.GA25085@linux.intel.com> On Mon, Jun 17, 2019 at 9:49 AM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > On Sun, Jun 16, 2019 at 03:14:51PM -0700, Andy Lutomirski wrote: > > On Fri, Jun 14, 2019 at 8:38 AM Sean Christopherson > > <sean.j.christopherson@intel.com> wrote: > > > > 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... > > > > The most significant issue I see is the following. Consider two > > cases. First, an SGX2 enclave that dynamically allocates memory but > > doesn't execute code from dynamic memory. Second, an SGX2 enclave > > that *does* execute code from dynamic memory. In #1, the untrusted > > stack needs to decide whether to ALLOW_EXEC when the memory is > > allocated, which means that it either needs to assume the worst or it > > needs to know at allocation time whether the enclave ever intends to > > change the permission to X. > > I'm just not convinced that folks running enclaves that can't communicate > their basic functionality will care one whit about SELinux restrictions, > i.e. will happily give EXECMOD even if it's not strictly necessary. At least when permissions are learned, if there's no ALLOW_EXEC for EAUG, then EXECMOD won't get learned if there's no eventual attempt to execute the memory. > > > I suppose there's a middle ground. The driver could use model #1 for > > driver-filled pages and model #2 for dynamic pages. I haven't tried > > to fully work it out, but I think there would be the ALLOW_READ / > > ALLOW_WRITE / ALLOW_EXEC flag for EADD-ed pages but, for EAUG-ed > > pages, there would be a different policy. This might be as simple as > > internally having four flags instead of three: > > > > ALLOW_READ, ALLOW_WRITE, ALLOW_EXEC: as before > > > > ALLOW_EXEC_COND: set implicitly by the driver for EAUG. > > > > As in #1, if you try to mmap or protect a page with neither ALLOW_EXEC > > variant, it fails (-EACCES, perhaps). But, if you try to mmap or > > mprotect an ALLOW_EXEC_COND page with PROT_EXEC, you ask LSM for > > permission. There is no fancy DIRTY tracking here, since it's > > reasonable to just act as though *every* ALLOW_EXEC_COND page is > > dirty. There is no real auditing issue here, since LSM can just log > > what permission is missing. > > > > Does this seem sensible? It might give us the best of #1 and #2. > > It would work and is easy to implement *if* SELinux ties permissions to > the process, as the SIGSTRUCT vma/file won't be available at > EAUG+mprotect(). I already have a set of patches to that effect, I'll > send 'em out in a bit. I'm okay with that. > > FWIW, we still need to differentiate W->X from WX on SGX1, i.e. declaring > ALLOW_WRITE + ALLOW_EXEC shouldn't imply WX. This is also addressed in > the forthcoming updated RFC. Sounds good.
next prev parent reply index Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-06-06 2:11 [RFC PATCH v2 0/5] security: x86/sgx: SGX vs. LSM Sean Christopherson 2019-06-06 2:11 ` [RFC PATCH v2 1/5] mm: Introduce vm_ops->may_mprotect() Sean Christopherson 2019-06-10 15:06 ` Jarkko Sakkinen 2019-06-10 15:55 ` Sean Christopherson 2019-06-10 17:47 ` Xing, Cedric 2019-06-10 19:49 ` Sean Christopherson 2019-06-10 22:06 ` Xing, Cedric 2019-06-06 2:11 ` [RFC PATCH v2 2/5] x86/sgx: Require userspace to define enclave pages' protection bits Sean Christopherson 2019-06-10 15:27 ` Jarkko Sakkinen 2019-06-10 16:15 ` Sean Christopherson 2019-06-10 17:45 ` Jarkko Sakkinen 2019-06-10 18:17 ` Sean Christopherson 2019-06-12 19:26 ` Jarkko Sakkinen 2019-06-10 18:29 ` Xing, Cedric 2019-06-10 19:15 ` Andy Lutomirski 2019-06-10 22:28 ` Xing, Cedric 2019-06-12 0:09 ` Andy Lutomirski 2019-06-12 14:34 ` Sean Christopherson 2019-06-12 18:20 ` Xing, Cedric 2019-06-06 2:11 ` [RFC PATCH v2 3/5] x86/sgx: Enforce noexec filesystem restriction for enclaves Sean Christopherson 2019-06-10 16:00 ` Jarkko Sakkinen 2019-06-10 16:44 ` Andy Lutomirski 2019-06-11 17:21 ` Stephen Smalley 2019-06-06 2:11 ` [RFC PATCH v2 4/5] LSM: x86/sgx: Introduce ->enclave_load() hook for Intel SGX Sean Christopherson 2019-06-07 19:58 ` Stephen Smalley 2019-06-10 16:21 ` Sean Christopherson 2019-06-10 16:05 ` Jarkko Sakkinen 2019-06-06 2:11 ` [RFC PATCH v2 5/5] security/selinux: Add enclave_load() implementation Sean Christopherson 2019-06-07 21:16 ` Stephen Smalley 2019-06-10 16:46 ` Sean Christopherson 2019-06-17 16:38 ` Jarkko Sakkinen 2019-06-10 7:03 ` [RFC PATCH v1 0/3] security/x86/sgx: SGX specific LSM hooks Cedric Xing 2019-06-10 7:03 ` [RFC PATCH v1 1/3] LSM/x86/sgx: Add " Cedric Xing 2019-06-10 7:03 ` [RFC PATCH v1 2/3] LSM/x86/sgx: Implement SGX specific hooks in SELinux Cedric Xing 2019-06-11 13:40 ` Stephen Smalley 2019-06-11 22:02 ` Sean Christopherson 2019-06-12 9:32 ` Dr. Greg 2019-06-12 14:25 ` Sean Christopherson 2019-06-13 7:25 ` Dr. Greg 2019-06-12 19:30 ` Andy Lutomirski 2019-06-12 22:02 ` Sean Christopherson 2019-06-13 0:10 ` Xing, Cedric 2019-06-13 1:02 ` Xing, Cedric 2019-06-13 17:02 ` Stephen Smalley 2019-06-13 23:03 ` Xing, Cedric 2019-06-13 23:17 ` Sean Christopherson 2019-06-14 0:31 ` Xing, Cedric 2019-06-14 0:46 ` Sean Christopherson 2019-06-14 15:38 ` Sean Christopherson 2019-06-16 22:14 ` Andy Lutomirski 2019-06-17 16:49 ` Sean Christopherson 2019-06-17 17:08 ` Andy Lutomirski [this message] 2019-06-18 15:40 ` Dr. Greg 2019-06-14 17:16 ` Xing, Cedric 2019-06-14 17:45 ` Sean Christopherson 2019-06-14 17:53 ` Sean Christopherson 2019-06-14 20:01 ` Sean Christopherson 2019-06-16 22:16 ` Andy Lutomirski 2019-06-14 23:19 ` Dr. Greg 2019-06-11 22:55 ` Xing, Cedric 2019-06-13 18:00 ` Stephen Smalley 2019-06-13 19:48 ` Sean Christopherson 2019-06-13 21:09 ` Xing, Cedric 2019-06-13 21:02 ` Xing, Cedric 2019-06-14 0:37 ` Sean Christopherson 2019-06-10 7:03 ` [RFC PATCH v1 3/3] LSM/x86/sgx: Call new LSM hooks from SGX subsystem Cedric Xing 2019-06-10 17:36 ` [RFC PATCH v1 0/3] security/x86/sgx: SGX specific LSM hooks Jarkko Sakkinen
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