From: Reinette Chatre <reinette.chatre@intel.com>
To: Jarkko Sakkinen <jarkko@kernel.org>,
Nathaniel McCallum <nathaniel@profian.com>
Cc: Haitao Huang <haitao.huang@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>, <dave.hansen@linux.intel.com>,
<tglx@linutronix.de>, <bp@alien8.de>, <mingo@redhat.com>,
<linux-sgx@vger.kernel.org>, <x86@kernel.org>,
<seanjc@google.com>, <kai.huang@intel.com>,
<cathy.zhang@intel.com>, <cedric.xing@intel.com>,
<haitao.huang@intel.com>, <mark.shanahan@intel.com>,
<hpa@zytor.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/25] x86/sgx: Introduce runtime protection bits
Date: Tue, 18 Jan 2022 12:59:38 -0800 [thread overview]
Message-ID: <eb696213-b066-0b6f-19ff-dd655b13209c@intel.com> (raw)
In-Reply-To: <YeYkdUHt7/HsRsZq@iki.fi>
Hi Jarkko,
On 1/17/2022 6:22 PM, Jarkko Sakkinen wrote:
> On Tue, Jan 18, 2022 at 03:59:29AM +0200, Jarkko Sakkinen wrote:
>> On Mon, Jan 17, 2022 at 08:13:32AM -0500, Nathaniel McCallum wrote:
>>> On Sat, Jan 15, 2022 at 6:57 AM Jarkko Sakkinen <jarkko@kernel.org> wrote:
>>>>
>>>> On Sat, Jan 15, 2022 at 03:18:04AM +0200, Jarkko Sakkinen wrote:
>>>>> On Fri, Jan 14, 2022 at 04:41:59PM -0800, Reinette Chatre wrote:
>>>>>> Hi Jarkko,
>>>>>>
>>>>>> On 1/14/2022 4:27 PM, Jarkko Sakkinen wrote:
>>>>>>> On Fri, Jan 14, 2022 at 04:01:33PM -0800, Reinette Chatre wrote:
>>>>>>>> Hi Jarkko,
>>>>>>>>
>>>>>>>> On 1/14/2022 3:15 PM, Jarkko Sakkinen wrote:
>>>>>>>>> On Fri, Jan 14, 2022 at 03:05:21PM -0800, Reinette Chatre wrote:
>>>>>>>>>> Hi Jarkko,
>>>>>>>>>
>>>>>>>>> How enclave can check a page range that EPCM has the expected permissions?
>>>>>>>>
>>>>>>>> Only way to change EPCM permissions from outside enclave is to run ENCLS[EMODPR]
>>>>>>>> that needs to be accepted from within the enclave via ENCLU[EACCEPT]. At that
>>>>>>>> time the enclave provides the expected permissions and that will fail
>>>>>>>> if there is a mismatch with the EPCM permissions (SGX_PAGE_ATTRIBUTES_MISMATCH).
>>>>>>>
>>>>>>> This is a very valid point but that does make the introspection possible
>>>>>>> only at the time of EACCEPT.
>>>>>>>
>>>>>>> It does not give tools for enclave to make sure that EMODPR-ETRACK dance
>>>>>>> was ever exercised.
>>>>>>
>>>>>> Could you please elaborate? EACCEPT is available to the enclave as a tool
>>>>>> and it would fail if ETRACK was not completed (error SGX_NOT_TRACKED).
>>>>>>
>>>>>> Here is the relevant snippet from the SDM from the section where it
>>>>>> describes EACCEPT:
>>>>>>
>>>>>> IF (Tracking not correct)
>>>>>> THEN
>>>>>> RFLAGS.ZF := 1;
>>>>>> RAX := SGX_NOT_TRACKED;
>>>>>> GOTO DONE;
>>>>>> FI;
>>>>>>
>>>>>> Reinette
>>>>>
>>>>> Yes, if enclave calls EACCEPT it does the necessary introspection and makes
>>>>> sure that ETRACK is completed. I have trouble understanding how enclave
>>>>> makes sure that EACCEPT was called.
>>>>
>>>> I'm not concerned of anything going wrong once EMODPR has been started.
>>>>
>>>> The problem nails down to that the whole EMODPR process is spawned by
>>>> the entity that is not trusted so maybe that should further broke down
>>>> to three roles:
>>>>
>>>> 1. Build process B
>>>> 2. Runner process R.
>>>> 3. Enclave E.
>>>>
>>>> And to the costraint that we trust B *more* than R. Once B has done all the
>>>> needed EMODPR calls it would send the file descriptor to R. Even if R would
>>>> have full access to /dev/sgx_enclave, it would not matter, since B has done
>>>> EMODPR-EACCEPT dance with E.
>>>>
>>>> So what you can achieve with EMODPR is not protection against mistrusted
>>>> *OS*. There's absolutely no chance you could use it for that purpose
>>>> because mistrusted OS controls the whole process.
>>>>
>>>> EMODPR is to help to protect enclave against mistrusted *process*, i.e.
>>>> in the above scenario R.
>>>
>>> There are two general cases that I can see. Both are valid.
>>>
>>> 1. The OS moves from a trusted to an untrusted state. This could be
>>> the multi-process system you've described. But it could also be that
>>> the kernel becomes compromised after the enclave is fully initialized.
>>>
>>> 2. The OS is untrustworthy from the start.
>>>
>>> The second case is the stronger one and if you can solve it, the first
>>> one is solved implicitly. And our end goal is that if the OS does
>>> anything malicious we will crash in a controlled way.
>>>
>>> A defensive enclave will always want to have the least number of
>>> privileges for the maximum protection. Therefore, the enclave will
>>> want the OS to call EMODPR. If that were it, the host could just lie.
>>> But the enclave also verifies that the EMODPR operation was, in fact,
>>> executed by doing EACCEPT. When the enclave calls EACCEPT, if the
>>> kernel hasn't restricted permissions then we get a controlled crash.
>>> Therefore, we have solved the second case.
>>
>> So you're referring to this part of the SDM pseude code in the SDM:
>>
>> (* Check the destination EPC page for concurrency *)
>> IF ( EPC page in use )
>> THEN #GP(0); FI;
>>
>> I wonder does "EPC page in use" unconditionally trigger when EACCEPT
>> is invoked for a page for which all of these conditions hold:
>>
>> - .PR := 0 (no EMODPR in progress)
>> - .MODIFIED := 0 (no EMODT in progress)
>> - .PENDING := 0 (no EMODPR in progress)
>>
>> I don't know the exact scope and scale of "EPC page in use".
>>
>> Then, yes, EACCEPT could be at least used to validate that one of the
>> three operations above was requested. However, enclave thread cannot say
>> which one was it, so it is guesswork.
>
> OK, I got it, and this last paragraph is not true. SECINFO given EACCEPT
> will lock in rest of the details and make the operation deterministic.
Indeed - so the SDM pseudo code that is relevant here can be found under
the "(* Verify that accept request matches current EPC page settings *)"
comment where the enclave can verify that all EPCM values are as they should
and would fail with SGX_PAGE_ATTRIBUTES_MISMATCH if there is anything
amiss.
>
> The only question mark then is the condition when no requests are active.
Could you please elaborate what you mean with this question? If no request
is active then I understand that to mean that no request has started.
Reinette
next prev parent reply other threads:[~2022-01-18 20:59 UTC|newest]
Thread overview: 155+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-01 19:22 [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2 Reinette Chatre
2021-12-01 19:22 ` [PATCH 01/25] x86/sgx: Add shortlog descriptions to ENCLS wrappers Reinette Chatre
2021-12-04 18:30 ` Jarkko Sakkinen
2021-12-06 21:13 ` Reinette Chatre
2021-12-11 5:28 ` Jarkko Sakkinen
2021-12-13 22:06 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 02/25] x86/sgx: Add wrappers for SGX2 functions Reinette Chatre
2021-12-04 22:04 ` Jarkko Sakkinen
2021-12-06 21:15 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 03/25] x86/sgx: Support VMA permissions exceeding enclave permissions Reinette Chatre
2021-12-04 22:25 ` Jarkko Sakkinen
2021-12-04 22:27 ` Jarkko Sakkinen
2021-12-06 21:16 ` Reinette Chatre
2021-12-11 5:39 ` Jarkko Sakkinen
2021-12-13 22:08 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 04/25] x86/sgx: Add pfn_mkwrite() handler for present PTEs Reinette Chatre
2021-12-04 22:43 ` Jarkko Sakkinen
2021-12-06 21:18 ` Reinette Chatre
2021-12-11 7:37 ` Jarkko Sakkinen
2021-12-13 22:09 ` Reinette Chatre
2021-12-28 14:51 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 05/25] x86/sgx: Introduce runtime protection bits Reinette Chatre
2021-12-03 19:28 ` Andy Lutomirski
2021-12-03 22:12 ` Reinette Chatre
2021-12-04 0:38 ` Andy Lutomirski
2021-12-04 1:14 ` Reinette Chatre
2021-12-04 17:56 ` Andy Lutomirski
2021-12-04 23:55 ` Reinette Chatre
2021-12-13 22:34 ` Reinette Chatre
2021-12-04 23:57 ` Jarkko Sakkinen
2021-12-06 21:20 ` Reinette Chatre
2021-12-11 7:42 ` Jarkko Sakkinen
2021-12-13 22:10 ` Reinette Chatre
2021-12-28 14:52 ` Jarkko Sakkinen
2022-01-06 17:46 ` Reinette Chatre
2022-01-07 12:16 ` Jarkko Sakkinen
2022-01-07 16:14 ` Haitao Huang
2022-01-08 15:45 ` Jarkko Sakkinen
2022-01-08 15:51 ` Jarkko Sakkinen
2022-01-08 16:22 ` Jarkko Sakkinen
2022-01-10 22:05 ` Haitao Huang
2022-01-11 1:53 ` Jarkko Sakkinen
2022-01-11 1:55 ` Jarkko Sakkinen
2022-01-11 2:03 ` Jarkko Sakkinen
2022-01-11 2:15 ` Jarkko Sakkinen
2022-01-11 3:48 ` Haitao Huang
2022-01-12 23:48 ` Jarkko Sakkinen
2022-01-13 2:41 ` Haitao Huang
2022-01-14 21:36 ` Jarkko Sakkinen
2022-01-11 17:13 ` Reinette Chatre
2022-01-12 23:50 ` Jarkko Sakkinen
2022-01-12 23:56 ` Jarkko Sakkinen
2022-01-13 20:09 ` Nathaniel McCallum
2022-01-13 21:42 ` Reinette Chatre
2022-01-14 21:53 ` Jarkko Sakkinen
2022-01-14 21:57 ` Jarkko Sakkinen
2022-01-14 22:00 ` Jarkko Sakkinen
2022-01-14 22:17 ` Jarkko Sakkinen
2022-01-14 22:23 ` Jarkko Sakkinen
2022-01-14 22:34 ` Jarkko Sakkinen
2022-01-14 23:05 ` Reinette Chatre
2022-01-14 23:15 ` Jarkko Sakkinen
2022-01-15 0:01 ` Reinette Chatre
2022-01-15 0:27 ` Jarkko Sakkinen
2022-01-15 0:41 ` Reinette Chatre
2022-01-15 1:18 ` Jarkko Sakkinen
2022-01-15 11:56 ` Jarkko Sakkinen
2022-01-15 11:59 ` Jarkko Sakkinen
2022-01-17 13:13 ` Nathaniel McCallum
2022-01-18 1:59 ` Jarkko Sakkinen
2022-01-18 2:22 ` Jarkko Sakkinen
2022-01-18 3:31 ` Jarkko Sakkinen
2022-01-18 20:59 ` Reinette Chatre [this message]
2022-01-20 12:53 ` Jarkko Sakkinen
2022-01-20 16:52 ` Reinette Chatre
2022-01-26 14:41 ` Jarkko Sakkinen
2022-01-15 16:49 ` Jarkko Sakkinen
2022-01-18 21:18 ` Reinette Chatre
2022-01-17 13:27 ` Nathaniel McCallum
2022-01-18 21:11 ` Reinette Chatre
2021-12-04 22:50 ` Jarkko Sakkinen
2021-12-06 21:28 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 06/25] x86/sgx: Use more generic name for enclave cpumask function Reinette Chatre
2021-12-04 22:56 ` Jarkko Sakkinen
2021-12-06 21:29 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 07/25] x86/sgx: Move PTE zap code to separate function Reinette Chatre
2021-12-04 22:59 ` Jarkko Sakkinen
2021-12-06 21:30 ` Reinette Chatre
2021-12-11 7:52 ` Jarkko Sakkinen
2021-12-13 22:11 ` Reinette Chatre
2021-12-28 14:55 ` Jarkko Sakkinen
2022-01-06 17:46 ` Reinette Chatre
2022-01-07 12:26 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 08/25] x86/sgx: Make SGX IPI callback available internally Reinette Chatre
2021-12-04 23:00 ` Jarkko Sakkinen
2021-12-06 21:36 ` Reinette Chatre
2021-12-11 7:53 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 09/25] x86/sgx: Keep record of SGX page type Reinette Chatre
2021-12-04 23:03 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 10/25] x86/sgx: Support enclave page permission changes Reinette Chatre
2021-12-02 23:48 ` Dave Hansen
2021-12-03 18:18 ` Reinette Chatre
2021-12-03 0:32 ` Dave Hansen
2021-12-03 18:18 ` Reinette Chatre
2021-12-03 18:14 ` Dave Hansen
2021-12-03 18:49 ` Reinette Chatre
2021-12-03 19:38 ` Andy Lutomirski
2021-12-03 22:34 ` Reinette Chatre
2021-12-04 0:42 ` Andy Lutomirski
2021-12-04 1:35 ` Reinette Chatre
2021-12-04 23:08 ` Jarkko Sakkinen
2021-12-06 20:19 ` Dave Hansen
2021-12-11 5:17 ` Jarkko Sakkinen
2021-12-06 21:42 ` Reinette Chatre
2021-12-11 7:57 ` Jarkko Sakkinen
2021-12-13 22:12 ` Reinette Chatre
2021-12-28 14:56 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 11/25] selftests/sgx: Add test for EPCM " Reinette Chatre
2021-12-01 19:23 ` [PATCH 12/25] selftests/sgx: Add test for TCS page " Reinette Chatre
2021-12-01 19:23 ` [PATCH 13/25] x86/sgx: Support adding of pages to initialized enclave Reinette Chatre
2021-12-03 0:38 ` Dave Hansen
2021-12-03 18:47 ` Reinette Chatre
2021-12-04 23:13 ` Jarkko Sakkinen
2021-12-06 21:44 ` Reinette Chatre
2021-12-11 8:00 ` Jarkko Sakkinen
2021-12-13 22:12 ` Reinette Chatre
2021-12-28 14:57 ` Jarkko Sakkinen
2022-03-01 15:13 ` Jarkko Sakkinen
2022-03-01 17:08 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 14/25] x86/sgx: Tighten accessible memory range after enclave initialization Reinette Chatre
2021-12-04 23:14 ` Jarkko Sakkinen
2021-12-06 21:45 ` Reinette Chatre
2021-12-11 8:01 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 15/25] selftests/sgx: Test two different SGX2 EAUG flows Reinette Chatre
2021-12-01 19:23 ` [PATCH 16/25] x86/sgx: Support modifying SGX page type Reinette Chatre
2021-12-04 23:45 ` Jarkko Sakkinen
2021-12-06 21:48 ` Reinette Chatre
2021-12-11 8:02 ` Jarkko Sakkinen
2021-12-13 17:43 ` Dave Hansen
2021-12-21 8:52 ` Jarkko Sakkinen
2021-12-01 19:23 ` [PATCH 17/25] x86/sgx: Support complete page removal Reinette Chatre
2021-12-04 23:45 ` Jarkko Sakkinen
2021-12-06 21:49 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 18/25] selftests/sgx: Introduce dynamic entry point Reinette Chatre
2021-12-01 19:23 ` [PATCH 19/25] selftests/sgx: Introduce TCS initialization enclave operation Reinette Chatre
2021-12-01 19:23 ` [PATCH 20/25] selftests/sgx: Test complete changing of page type flow Reinette Chatre
2021-12-01 19:23 ` [PATCH 21/25] selftests/sgx: Test faulty enclave behavior Reinette Chatre
2021-12-01 19:23 ` [PATCH 22/25] selftests/sgx: Test invalid access to removed enclave page Reinette Chatre
2021-12-01 19:23 ` [PATCH 23/25] selftests/sgx: Test reclaiming of untouched page Reinette Chatre
2021-12-01 19:23 ` [PATCH 24/25] x86/sgx: Free up EPC pages directly to support large page ranges Reinette Chatre
2021-12-04 23:47 ` Jarkko Sakkinen
2021-12-06 22:07 ` Reinette Chatre
2021-12-01 19:23 ` [PATCH 25/25] selftests/sgx: Page removal stress test Reinette Chatre
2021-12-02 18:30 ` [PATCH 00/25] x86/sgx and selftests/sgx: Support SGX2 Dave Hansen
2021-12-02 20:38 ` Nathaniel McCallum
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=eb696213-b066-0b6f-19ff-dd655b13209c@intel.com \
--to=reinette.chatre@intel.com \
--cc=bp@alien8.de \
--cc=cathy.zhang@intel.com \
--cc=cedric.xing@intel.com \
--cc=dave.hansen@linux.intel.com \
--cc=haitao.huang@intel.com \
--cc=haitao.huang@linux.intel.com \
--cc=hpa@zytor.com \
--cc=jarkko@kernel.org \
--cc=kai.huang@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-sgx@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mark.shanahan@intel.com \
--cc=mingo@redhat.com \
--cc=nathaniel@profian.com \
--cc=seanjc@google.com \
--cc=tglx@linutronix.de \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).