From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A472C67872 for ; Thu, 13 Dec 2018 07:57:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2BD2F20873 for ; Thu, 13 Dec 2018 07:57:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2BD2F20873 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727051AbeLMH5d (ORCPT ); Thu, 13 Dec 2018 02:57:33 -0500 Received: from lhrrgout.huawei.com ([185.176.76.210]:32808 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726500AbeLMH5d (ORCPT ); Thu, 13 Dec 2018 02:57:33 -0500 Received: from LHREML711-CAH.china.huawei.com (unknown [172.18.7.108]) by Forcepoint Email with ESMTP id 1779B5AF6435B; Thu, 13 Dec 2018 07:57:30 +0000 (GMT) Received: from [10.204.65.144] (10.204.65.144) by smtpsuk.huawei.com (10.201.108.34) with Microsoft SMTP Server (TLS) id 14.3.408.0; Thu, 13 Dec 2018 07:57:22 +0000 Subject: Re: [PATCH v6 7/7] tpm: pass an array of tpm_bank_list structures to tpm_pcr_extend() To: Jarkko Sakkinen CC: , , , , , , References: <20181204082138.24600-1-roberto.sassu@huawei.com> <20181204082138.24600-8-roberto.sassu@huawei.com> <20181205001417.GF1233@linux.intel.com> <9d6e47d9-3b88-86f6-1b60-6652dfe8dc00@huawei.com> <20181212182734.GH6333@linux.intel.com> From: Roberto Sassu Message-ID: Date: Thu, 13 Dec 2018 08:57:17 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <20181212182734.GH6333@linux.intel.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.204.65.144] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/12/2018 7:27 PM, Jarkko Sakkinen wrote: > On Thu, Dec 06, 2018 at 07:38:30PM +0100, Roberto Sassu wrote: >> On 12/5/2018 1:14 AM, Jarkko Sakkinen wrote: >>> On Tue, Dec 04, 2018 at 09:21:38AM +0100, Roberto Sassu wrote: >>>> The new tpm_bank_list structure has been preferred to the tpm_digest >>>> structure, to let the caller specify the size of the digest (which may be >>>> unknown to the TPM driver). >>> >>> Why is that? Didn't previous commit query these? >> >> Since the TPM driver pads/truncates the first digest passed by the >> caller to extend PCRs for which no digest was provided, it must know >> which amount of data it can use. It is possible that the algorithm of >> the first digest is unknown for the TPM driver, if the caller of >> tpm_pcr_extend() didn't check chip->allocated_banks. >> >> By requiring that the caller passes also the digest size, this problem >> does not arise. It seems reasonable to me to pass this information, as >> the caller calculated the digest and it should know the digest size. > > OK. I noticed something other things that look to alarming: > > 1. The function does not fail if alg_id is not found. This will go > silent. It is intentional. If alg_id is not found, the PCR is extended with the first digest passed by the caller of tpm_pcr_extend(). If no digest was provided, the PCR is extended with 0s. This is done to prevent that PCRs in unused banks are extended later with fake measurements. > 2. The function does not fail if there is a mismatch with the digest > sizes. The data passed by the caller of tpm_pcr_extend() is copied to dummy_hash, which has the maximum length. Then, tpm2_pcr_extend() takes from dummy_hash as many bytes as needed, depending on the current algorithm. Roberto > /Jarkko > -- HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Bo PENG, Jian LI, Yanli SHI