From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752663AbdEVH2P (ORCPT ); Mon, 22 May 2017 03:28:15 -0400 Received: from lhrrgout.huawei.com ([194.213.3.17]:27059 "EHLO lhrrgout.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751726AbdEVH2M (ORCPT ); Mon, 22 May 2017 03:28:12 -0400 Subject: Re: [PATCH v2 2/5] tpm: introduce tpm_pcr_algo_to_crypto() and tpm_pcr_algo_from_crypto() To: Jarkko Sakkinen References: <20170505142152.29795-1-roberto.sassu@huawei.com> <20170505142152.29795-3-roberto.sassu@huawei.com> <20170515111629.urjvbhqzohv4vakc@intel.com> <0deed9be-d0c3-3a69-d510-1c8aa3513ba8@huawei.com> <20170520132217.t7n7l2pjn7i63hbm@intel.com> CC: , , , , From: Roberto Sassu Message-ID: <0b04a33c-248b-6597-473f-c5bc4ccaba62@huawei.com> Date: Mon, 22 May 2017 09:21:28 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20170520132217.t7n7l2pjn7i63hbm@intel.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.220.96.113] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.59229182.00AB,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 3a9a11b3d427ecc2ac917fd5a319e992 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/20/2017 3:22 PM, Jarkko Sakkinen wrote: > On Mon, May 15, 2017 at 04:22:22PM +0200, Roberto Sassu wrote: >> On 5/15/2017 1:16 PM, Jarkko Sakkinen wrote: >>> On Fri, May 05, 2017 at 04:21:49PM +0200, Roberto Sassu wrote: >>>> tpm_pcr_algorithms() returns to its callers the IDs of the hash algorithms >>>> supported by the TPM. This patch introduces tpm_pcr_algo_to_crypto(), >>>> so that the callers can use the crypto subsystem to calculate the digest >>>> to be passed to tpm_pcr_extend(). >>>> >>>> tpm_pcr_algo_from_crypto(), implemented for completeness, is instead used >>> >>> What do you mean by completeness? Please, never add unused stuff. >>> >>>> by tpm2_seal_trusted() to perform the opposite conversion. >>>> >>>> Signed-off-by: Roberto Sassu >>>> --- >>>> v2 >>>> >>>> - fixed return values of tpm2_pcr_algo_to_crypto() and >>>> tpm2_pcr_algo_from_crypto() if TPM support is disabled in the kernel >>> >>> Change Log only to the cover letter. >>> >>>> drivers/char/tpm/tpm-interface.c | 51 ++++++++++++++++++++++++++++++++++++++++ >>>> drivers/char/tpm/tpm2-cmd.c | 42 +++++++++------------------------ >>>> include/linux/tpm.h | 13 ++++++++++ >>>> 3 files changed, 75 insertions(+), 31 deletions(-) >>> >>> This commit is just deadly wrong in so many ways. >>> >>> I would suggest to make extend always just take crypto ID in so you >>> don't have to add these bizarre conversion functions. >> >> The reason of this choice (as I explained in the cover letter) >> is that TPM users might want to produce an event log with >> the TCG format (which includes the TPM algorithm ID). Also, >> TPM IDs should be preferred because, with them, TPM users >> can calculate a digest directly with the TPM. >> >> Taking crypto IDs means relying on the fact that there >> is always a mapping between TPM IDs and crypto IDs. >> Otherwise, tpm_pcr_algorithms() cannot return the algorithms >> to its callers and PCRs cannot be extended. If TPM IDs are used, >> TPM users have two alternatives: calculate the digest with >> the TPM, or pass a SHA1 digest to tpm_pcr_extend(), so that >> it can be padded to extend remanining PCR banks. >> >> However, this second option will work only when the TPM driver >> determines the size of an algorithm without relying on the crypto >> subsystem. At the moment, if a TPM ID is not mapped to a crypto ID, >> tpm2_pcr_extend() ignores the digest. >> >> Roberto > > What if tpm_pcr_algorithms would convert TPM IDs to crypto IDs? > > Externally other subsystems would have to then deal with only crypto > IDs. Then, other subsystems cannot: - use the TPM to calculate a digest - create an event log with the TCG format Roberto