From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752493AbdHNH7Z (ORCPT ); Mon, 14 Aug 2017 03:59:25 -0400 Received: from mail-yw0-f196.google.com ([209.85.161.196]:35274 "EHLO mail-yw0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752464AbdHNH7V (ORCPT ); Mon, 14 Aug 2017 03:59:21 -0400 MIME-Version: 1.0 X-Originating-IP: [217.140.96.140] In-Reply-To: References: <20170602122446.2427-1-david@sigma-star.at> <20170628132710.97278-1-david@sigma-star.at> From: Gilad Ben-Yossef Date: Mon, 14 Aug 2017 10:59:20 +0300 Message-ID: Subject: Re: [PATCH] crypto: caam - properly set IV after {en,de}crypt To: =?UTF-8?Q?Horia_Geant=C4=83?= Cc: David Gstir , Dan Douglass , "herbert@gondor.apana.org.au" , "davem@davemloft.net" , "richard@sigma-star.at" , "linux-crypto@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v7E7xUxE018479 Hi, On Thu, Jun 29, 2017 at 1:19 PM, Horia Geantă 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: # 4.8+ >>> Signed-off-by: David Gstir >> Reviewed-by: Horia Geantă >> > 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? 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. Thanks! Gilad -- Gilad Ben-Yossef Chief Coffee Drinker "If you take a class in large-scale robotics, can you end up in a situation where the homework eats your dog?" -- Jean-Baptiste Queru