From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751987AbcHIFTm (ORCPT ); Tue, 9 Aug 2016 01:19:42 -0400 Received: from mail-pa0-f66.google.com ([209.85.220.66]:33375 "EHLO mail-pa0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750810AbcHIFTi (ORCPT ); Tue, 9 Aug 2016 01:19:38 -0400 Subject: Re: [PATCH 0/7] ima: carry the measurement list across kexec To: Mimi Zohar , linux-security-module@vger.kernel.org References: <1470313475-20090-1-git-send-email-zohar@linux.vnet.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Thiago Jung Bauermann , linux-ima-devel@lists.sourceforge.net, Dave Young From: Balbir Singh Message-ID: <91fa2f95-4d70-a056-d599-01cb3bbe6771@gmail.com> Date: Tue, 9 Aug 2016 15:19:31 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.0 MIME-Version: 1.0 In-Reply-To: <1470313475-20090-1-git-send-email-zohar@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/08/16 22:24, Mimi Zohar wrote: > The TPM PCRs are only reset on a hard reboot. In order to validate a > TPM's quote after a soft reboot (eg. kexec -e), the IMA measurement list > of the running kernel must be saved and then restored on the subsequent > boot. > > The existing securityfs binary_runtime_measurements file conveniently > provides a serialized format of the IMA measurement list. This patch > set serializes the measurement list in this format and restores it. > > This patch set pre-req's Thiago Bauermann's "kexec_file: Add buffer > hand-over for the next kernel" patch set* for actually carrying the > serialized measurement list across the kexec. > > Mimi > Hi, Mimi I am trying to convince myself of the security of the solution. I asked Thiago as well, but may be I am be lagging behind in understanding. We trust the kernel to hand over PCR values of the old kernel (which cannot be validated) to the IMA subsystem in the new kernel for storage. I guess the idea is for ima_add_boot_aggregate to do the right thing? How do we validate what the old kernel is giving us? Why do we care for the old measurement list? Is it still of significance in the new kernel? Balbir Singh.