From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com; receiver=edk2-devel@lists.01.org Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 75F0B2119F062 for ; Thu, 13 Dec 2018 04:36:15 -0800 (PST) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0A99E3002307; Thu, 13 Dec 2018 12:36:15 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-134.rdu2.redhat.com [10.10.120.134]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5E7A753C28; Thu, 13 Dec 2018 12:36:10 +0000 (UTC) To: Matthew Garrett References: <20181213011750.bfzfyhrr4ufsiu6j@srcf.ucam.org> Cc: edk2-devel@lists.01.org, Jiewen Yao , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , Stefan Berger From: Laszlo Ersek Message-ID: Date: Thu, 13 Dec 2018 13:36:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181213011750.bfzfyhrr4ufsiu6j@srcf.ucam.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Thu, 13 Dec 2018 12:36:15 +0000 (UTC) Subject: Re: Obtaining TCG final events on systems without TCG2 log support X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 13 Dec 2018 12:36:16 -0000 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit + Jiewen, Marc-André, Stefan On 12/13/18 02:17, Matthew Garrett wrote: > SetupEventLog() in Tcg2Dxe.c only installs the final event log > configuration table if SupportedEventLogs includes the TCG2 log format. > If the platform only supports the TCG1.2 log format then the final > events table isn't installed. However, ExitBootServices() should > generate an event even on systems that don't support the TCG2 log > format. How is an OS supposed to obtain the log of the > ExitBootServices() events in that case? > I don't think it can. You probably refer to the code below the comment "No need to handle EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2", in SetupEventLog(). This code dates back to commit fd46e831bc33 ("SecurityPkg: Update final event log calculation.", 2016-01-18). And the commit message says, "... there is no need to record TCG12 format log to final event log area ...". Hence, the code is intentional. I even think the code is valid (according to the spec [*]); I just think the commit message should have said, "there is no *way* to record TCG12 format log to final event log area". Because, IMO, the bug is in the spec. [*] TCG EFI Protocol Specification Family “2.0” Level 00 Revision 00.13 March 30, 2016 Here's why I think it's a spec bug: (1) If EFI_TCG2_EVENT_LOG_FORMAT_TCG_2 is *clear* in SupportedEventLogs, then the platform advertizes GetEventLog() as unable to produce the crypto agile log format. In other words, the platform is unable to produce a log which consists of TCG_PCR_EVENT2 entries, beyond the sole TCG_PCR_EVENT ("SHA1 format") header entry. Accordingly, GetEventLog() will fail with EFI_INVALID_PARAMETER, when called with EventLogFormat=EFI_TCG2_EVENT_LOG_FORMAT_TCG_2. (BTW, I think EFI_UNSUPPORTED would have been better for this, but I digress.) (2) EFI_TCG2_FINAL_EVENTS_TABLE is defined with TCG_PCR_EVENT2 entries *only*. TCG_PCR_EVENT is not accommodated. That's the contradiction. If a platform is unable to produce TCG_PCR_EVENT2 entries in GetEventLog(), it is fairly certainly also unable to produce them in the final events table. And, while the first *instance* of the limitation is conformant, via SupportedEventLogs, the second instance of the same limitation isn't. Thanks, Laszlo