From: "Horia Geantă" <horia.geanta@nxp.com>
To: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: David Gstir <david@sigma-star.at>,
Dan Douglass <dan.douglass@nxp.com>,
"herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
"davem@davemloft.net" <davem@davemloft.net>,
"richard@sigma-star.at" <richard@sigma-star.at>,
"linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] crypto: caam - properly set IV after {en,de}crypt
Date: Tue, 5 Sep 2017 15:33:01 +0000 [thread overview]
Message-ID: <VI1PR0402MB3342A3AB9EEC3B36A79F253698960@VI1PR0402MB3342.eurprd04.prod.outlook.com> (raw)
In-Reply-To: CAOtvUMfa66v6_MfasHRG8Qk9h81GMTnObuBSObBGcSL4QoOMDQ@mail.gmail.com
On 8/14/2017 10:59 AM, Gilad Ben-Yossef wrote:
> Hi,
>
> On Thu, Jun 29, 2017 at 1:19 PM, Horia Geantă <horia.geanta@nxp.com> wrote:
>> On 6/28/2017 4:42 PM, Horia Geantă wrote:
>>> On 6/28/2017 4:27 PM, David Gstir wrote:
>>>> Certain cipher modes like CTS expect the IV (req->info) of
>>>> ablkcipher_request (or equivalently req->iv of skcipher_request) to
>>>> contain the last ciphertext block when the {en,de}crypt operation is done.
>>>> This is currently not the case for the CAAM driver which in turn breaks
>>>> e.g. cts(cbc(aes)) when the CAAM driver is enabled.
>>>>
>>>> This patch fixes the CAAM driver to properly set the IV after the
>>>> {en,de}crypt operation of ablkcipher finishes.
>>>>
>>>> This issue was revealed by the changes in the SW CTS mode in commit
>>>> 0605c41cc53ca ("crypto: cts - Convert to skcipher")
>>>>
>>>> Cc: <stable@vger.kernel.org> # 4.8+
>>>> Signed-off-by: David Gstir <david@sigma-star.at>
>>> Reviewed-by: Horia Geantă <horia.geanta@nxp.com>
>>>
>> Btw, instead of updating the IV in SW, CAAM engine could be programmed
>> to do it - by saving the Context Register of the AES accelerator.
>>
>> Unfortunately this would require changes in quite a few places: shared
>> descriptor, HW S/G generation logic, IV dma (un)mapping and maybe others.
>>
>> So it's better to have this fix now (which, considering size, is
>> appropriate for -stable) and later, if needed, offload IV updating in HW.
>>
>
> My apologies for reviving this thread from the dead, but doesn't the patch fail
> for in-place decryption since we are copying from req->dst after
> the operation is done, and therefore it no longer contains the ciphertext?
>
You are right, thanks! Will follow up with a fix.
Though cts(cbc(aes)) in particular is working, see below.
> I'm asking since I ran into a similar issue in the ccree driver and thought
> to deploy a similar fix but could not convince myself why this works.
>
IIUC cts(cbc(aes)) in-place decryption (with cbc(aes) offloaded to CAAM
engine) works since SW implementation of cts, when performing the
ciphertext stealing phase in cts_cbc_decrypt() does not use req->iv, but
a previously value, saved before staring decryption in crypto_cts_decrypt():
if (cbc_blocks <= 1)
memcpy(space, req->iv, bsize);
else
scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
bsize, 0);
Horia
next prev parent reply other threads:[~2017-09-05 15:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-02 12:24 [RFC PATCH 0/2] crypto: caam - fix cts(cbc(aes)) with CAAM driver David Gstir
2017-06-02 12:24 ` [RFC PATCH 1/2] crypto: caam - properly set IV after {en,de}crypt David Gstir
2017-06-19 10:31 ` Horia Geantă
2017-06-20 1:28 ` Herbert Xu
2017-06-26 5:40 ` David Gstir
2017-06-26 6:47 ` Herbert Xu
2017-06-28 8:32 ` Horia Geantă
2017-06-28 9:03 ` David Gstir
2017-06-02 12:24 ` [RFC PATCH 2/2] crypto: caam - fix k*alloc if called from own cipher callback David Gstir
2017-06-13 11:53 ` [RFC PATCH 0/2] crypto: caam - fix cts(cbc(aes)) with CAAM driver David Gstir
2017-06-15 14:57 ` Horia Geantă
2017-06-16 7:57 ` Horia Geantă
2017-06-16 7:59 ` Herbert Xu
2017-06-16 21:01 ` Horia Geantă
2017-06-17 9:05 ` David Gstir
2017-06-19 8:44 ` [PATCH 1/2] crypto: caam - fix gfp allocation flags (part I) Horia Geantă
2017-06-19 8:44 ` [PATCH 2/2] crypto: caam - fix gfp allocation flags (part II) Horia Geantă
2017-06-22 9:00 ` Herbert Xu
2017-06-22 9:00 ` [PATCH 1/2] crypto: caam - fix gfp allocation flags (part I) Herbert Xu
2017-06-28 13:27 ` [PATCH] crypto: caam - properly set IV after {en,de}crypt David Gstir
2017-06-28 13:42 ` Horia Geantă
2017-06-29 10:19 ` Horia Geantă
2017-08-14 7:59 ` Gilad Ben-Yossef
2017-09-05 15:33 ` Horia Geantă [this message]
2017-09-06 10:14 ` Gilad Ben-Yossef
2017-09-07 10:12 ` Horia Geantă
2017-07-12 10:51 ` Herbert Xu
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