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From: Stephen Smalley <sds@tycho.nsa.gov>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
	linux-sgx@vger.kernel.org, akpm@linux-foundation.org,
	dave.hansen@intel.com, sean.j.christopherson@intel.com,
	nhorman@redhat.com, npmccallum@redhat.com, serge.ayoun@intel.com,
	shay.katz-zamir@intel.com, haitao.huang@intel.com,
	andriy.shevchenko@linux.intel.com, tglx@linutronix.de,
	kai.svahn@intel.com, bp@alien8.de, josh@joshtriplett.org,
	luto@kernel.org, kai.huang@intel.com, rientjes@google.com,
	cedric.xing@intel.com, puiterwijk@redhat.com,
	linux-security-module@vger.kernel.org,
	Suresh Siddha <suresh.b.siddha@intel.com>
Subject: Re: [PATCH v23 12/24] x86/sgx: Linux Enclave Driver
Date: Fri, 1 Nov 2019 09:16:16 -0400
Message-ID: <f91d788c-b372-8e2f-7ffb-995f501b5d6b@tycho.nsa.gov> (raw)
In-Reply-To: <20191031211721.GD10507@linux.intel.com>

On 10/31/19 5:17 PM, Jarkko Sakkinen wrote:
> On Wed, Oct 30, 2019 at 09:45:05AM -0400, Stephen Smalley wrote:
>> On 10/28/19 5:03 PM, Jarkko Sakkinen wrote:
>>> Intel Software Guard eXtensions (SGX) is a set of CPU instructions that
>>> can be used by applications to set aside private regions of code and
>>> data. The code outside the SGX hosted software entity is disallowed to
>>> access the memory inside the enclave enforced by the CPU. We call these
>>> entities as enclaves.
>>>
>>> This commit implements a driver that provides an ioctl API to construct
>>> and run enclaves. Enclaves are constructed from pages residing in
>>> reserved physical memory areas. The contents of these pages can only be
>>> accessed when they are mapped as part of an enclave, by a hardware
>>> thread running inside the enclave.
>>>
>>> The starting state of an enclave consists of a fixed measured set of
>>> pages that are copied to the EPC during the construction process by
>>> using ENCLS leaf functions and Software Enclave Control Structure (SECS)
>>> that defines the enclave properties.
>>>
>>> Enclave are constructed by using ENCLS leaf functions ECREATE, EADD and
>>> EINIT. ECREATE initializes SECS, EADD copies pages from system memory to
>>> the EPC and EINIT check a given signed measurement and moves the enclave
>>> into a state ready for execution.
>>>
>>> An initialized enclave can only be accessed through special Thread Control
>>> Structure (TCS) pages by using ENCLU (ring-3 only) leaf EENTER.  This leaf
>>> function converts a thread into enclave mode and continues the execution in
>>> the offset defined by the TCS provided to EENTER. An enclave is exited
>>> through syscall, exception, interrupts or by explicitly calling another
>>> ENCLU leaf EEXIT.
>>>
>>> The permissions, which enclave page is added will set the limit for maximum
>>> permissions that can be set for mmap() and mprotect(). This will
>>> effectively allow to build different security schemes between producers and
>>> consumers of enclaves. Later on we can increase granularity with LSM hooks
>>> for page addition (i.e. for producers) and mapping of the enclave (i.e. for
>>> consumers)
>>
>> Where do things stand wrt to ensuring that SGX cannot be used to introduce
>> executable mappings that were never authorized by the LSM (or never measured
>> by IMA)?
> 
> This was the latest discussion about that subject:
> 
> https://lore.kernel.org/linux-sgx/CALCETrWDLX68Vi4=9Dicq9ATmJ5mv36bzrc02heNYaHaBeWumQ@mail.gmail.com/

So, IIUC, that means that merging the driver will create a regression 
with respect to LSM control over executable mappings that will only be 
rectified at some future point in time if/when someone submits LSM hooks 
or calls to existing hooks to restore such control.  That doesn't seem 
like a good idea.  Why can't you include at least that basic level of 
control now?  It is one thing to defer finer grained control or 
SGX-specific access controls to the future - that I can understand.  But 
introducing a regression in the existing controls is not really ok.

  reply index

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20191028210324.12475-1-jarkko.sakkinen@linux.intel.com>
2019-10-28 21:03 ` Jarkko Sakkinen
2019-10-29  9:29   ` Jarkko Sakkinen
2019-10-30  9:30     ` Sean Christopherson
2019-10-31 21:12       ` Jarkko Sakkinen
2019-11-05 11:11         ` Jarkko Sakkinen
2019-11-08  8:20           ` Jarkko Sakkinen
2019-10-30 13:45   ` Stephen Smalley
2019-10-31 21:17     ` Jarkko Sakkinen
2019-11-01 13:16       ` Stephen Smalley [this message]
2019-11-01 13:28         ` Stephen Smalley
2019-11-01 15:32           ` Sean Christopherson
2019-11-01 17:16             ` Stephen Smalley
2019-11-08  8:05               ` Jarkko Sakkinen
2019-11-28 18:24   ` Greg KH
2019-12-06 20:38     ` Jarkko Sakkinen
2019-12-07  8:09       ` Greg KH
2019-12-09 19:57         ` Jarkko Sakkinen
2019-10-28 21:03 ` [PATCH v23 15/24] x86/sgx: Add provisioning Jarkko Sakkinen

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