From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-sgx@vger.kernel.org, Dave Hansen <dave.hansen@intel.com>,
Cedric Xing <cedric.xing@intel.com>,
Andy Lutomirski <luto@kernel.org>,
Jethro Beekman <jethro@fortanix.com>,
"Dr . Greg Wettstein" <greg@enjellic.com>,
Stephen Smalley <sds@tycho.nsa.gov>
Subject: Re: [RFC PATCH v3 04/12] x86/sgx: Require userspace to define enclave pages' protection bits
Date: Mon, 8 Jul 2019 09:19:32 -0700 [thread overview]
Message-ID: <20190708161932.GE20433@linux.intel.com> (raw)
In-Reply-To: <1b7369a08e98dd08a4f8bb19b16479f12bee130f.camel@linux.intel.com>
On Mon, Jul 08, 2019 at 06:23:46PM +0300, Jarkko Sakkinen wrote:
> On Sun, 2019-07-07 at 12:08 -0700, Sean Christopherson wrote:
> > LGTM but why it isn't like:
> > >
> > > __u16 mrmask;
> > > __u8 prot;
> > > __u8 reserved[5];
> >
> > Because math is hard :-) Though I think we'd want
> >
> > __u16 mrmask
> > __u8 prot
> > __u8 pad[5];
> >
> > with an optional
> >
> > __u64 reserved[?];
> >
> > "pad" can be ignored, e.g. doesn't need to be explicitly zeroed by
> > userspace, whereas "reserved" requires explicit zeroing and probably an
> > associated kernel check.
>
> OK, cool with the change itself. Still need to get a better idea
> how these make sense in architectural sense.
>
> Things that would help with overall picture:
>
> 1. We have to figure out how this can be useful when LSM's are not used.
Declaring PROT_EXEC is useful to enforce noexec filesystems. Beyond that,
I am not aware of any meaningful use case.
> That gives at least some evidence that the security model is overally
> good if it makes sense with and without LSM. Right now this looks like
> dead functionality if not coupled with an LSM.
I agree that it's effectively dead functionality without LSMs, but keep
in mind that this LSM rat hole was opened specifically because SGX could
be used to circumvent existing LSM security policies. In other words,
the purpose of the UAPI extension is to achieve LSM compatibility without
incurring significant complexity in the LSM subsystem.
> 2. Probably some "user story" type of examples would help with the
> discussion overall [1] i.e. how one would use this for
> her own good.
The compelling story is Andy's original concern that userspace could
circumvent existing security policies by running code in an enclave.
AIUI, closing the LSM loophole is the minimal requirement to get SGX
upstreamed. The extensive discussion has largely been focused on
ensuring that whatever mechanism is used to close the loophole will
play nice with future SGX functionality and/or LSM security policies.
> [1] Probably many of the folks who work x86 tree have ignored major
> part of the discussion. Somehow these should be brought to
> nutshell so that anyone can get whatever the model is. Anyone
> should get it basically.
>
> /Jarkko
>
next prev parent reply other threads:[~2019-07-08 16:19 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-17 22:24 [RFC PATCH v3 00/12] security: x86/sgx: SGX vs. LSM, round 3 Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 01/12] x86/sgx: Add mm to enclave at mmap() Sean Christopherson
2019-06-17 22:32 ` Dave Hansen
2019-06-17 23:42 ` Andy Lutomirski
2019-06-18 14:11 ` Sean Christopherson
2019-06-18 16:06 ` Sean Christopherson
2019-06-19 12:56 ` Jarkko Sakkinen
2019-06-19 13:00 ` Jarkko Sakkinen
2019-06-20 20:09 ` Jarkko Sakkinen
2019-06-17 22:24 ` [RFC PATCH v3 02/12] x86/sgx: Do not naturally align MAP_FIXED address Sean Christopherson
2019-06-19 13:24 ` Jarkko Sakkinen
2019-06-19 14:08 ` Sean Christopherson
2019-06-20 22:07 ` Jarkko Sakkinen
2019-06-17 22:24 ` [RFC PATCH v3 03/12] selftests: x86/sgx: Mark the enclave loader as not needing an exec stack Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 04/12] x86/sgx: Require userspace to define enclave pages' protection bits Sean Christopherson
2019-06-19 14:43 ` Jarkko Sakkinen
2019-06-19 15:20 ` Sean Christopherson
2019-06-20 22:17 ` Jarkko Sakkinen
2019-07-07 19:08 ` Sean Christopherson
2019-07-08 15:23 ` Jarkko Sakkinen
2019-07-08 16:19 ` Sean Christopherson [this message]
2019-07-09 16:06 ` Jarkko Sakkinen
2019-07-10 17:25 ` Sean Christopherson
2019-07-15 22:29 ` Andy Lutomirski
2019-08-01 16:38 ` Jarkko Sakkinen
2019-08-04 22:20 ` Andy Lutomirski
2019-08-05 20:51 ` Jarkko Sakkinen
2019-08-05 21:30 ` Andy Lutomirski
2019-08-07 18:51 ` Jarkko Sakkinen
2019-06-17 22:24 ` [RFC PATCH v3 05/12] x86/sgx: Enforce noexec filesystem restriction for enclaves Sean Christopherson
2019-06-19 14:46 ` Jarkko Sakkinen
2019-06-17 22:24 ` [RFC PATCH v3 06/12] mm: Introduce vm_ops->may_mprotect() Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 07/12] LSM: x86/sgx: Introduce ->enclave_map() hook for Intel SGX Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 08/12] security/selinux: Require SGX_EXECMEM to map enclave page WX Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 09/12] LSM: x86/sgx: Introduce ->enclave_load() hook for Intel SGX Sean Christopherson
2019-06-19 14:56 ` Jarkko Sakkinen
2019-06-19 21:13 ` James Morris
2019-06-20 9:28 ` Dr. Greg
2019-06-20 22:22 ` Jarkko Sakkinen
2019-06-23 17:16 ` Dr. Greg
2019-06-26 20:39 ` James Morris
2019-06-17 22:24 ` [RFC PATCH v3 10/12] security/selinux: Add enclave_load() implementation Sean Christopherson
2019-06-18 14:49 ` Stephen Smalley
2019-06-19 20:59 ` Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 11/12] security/apparmor: " Sean Christopherson
2019-06-17 22:24 ` [RFC PATCH v3 12/12] LSM: x86/sgx: Show line of sight to LSM support SGX2's EAUG Sean Christopherson
2019-06-18 13:38 ` [RFC PATCH v3 00/12] security: x86/sgx: SGX vs. LSM, round 3 Stephen Smalley
2019-06-18 13:55 ` Sean Christopherson
2019-06-18 15:13 ` Stephen Smalley
2019-06-25 16:29 ` Jarkko Sakkinen
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