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=-13.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 1E000C433FE for ; Fri, 11 Dec 2020 03:11:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CB79B23E51 for ; Fri, 11 Dec 2020 03:11:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388169AbgLKDLC (ORCPT ); Thu, 10 Dec 2020 22:11:02 -0500 Received: from linux.microsoft.com ([13.77.154.182]:38126 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729331AbgLKDKv (ORCPT ); Thu, 10 Dec 2020 22:10:51 -0500 Received: from sequoia (162-237-133-238.lightspeed.rcsntx.sbcglobal.net [162.237.133.238]) by linux.microsoft.com (Postfix) with ESMTPSA id 1AA7920B717A; Thu, 10 Dec 2020 19:10:10 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 1AA7920B717A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1607656210; bh=UjXdwP2ZHKFxPJkmlk76kE+9RzmPBF3Xf8HNjv05RPE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iZFK29ut36BwHBbKNBpcvUPr32umM+0qxOCVISeIxhi6k7fwPq+62tCU8Gwl5W5pm 4YhdwUVPbyrQP39Wq9uhsPJcZsLYwJASDupHYEkW6gywDAJqD0U67kwwkSt1aysqwc lWL6VcuecrDcXM5Um1L7FU/qizWs6Gg5YQteOUMI= Date: Thu, 10 Dec 2020 21:10:08 -0600 From: Tyler Hicks To: Mimi Zohar Cc: Sasha Levin , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Maurizio Drocco , Bruno Meneguele , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH AUTOSEL 5.7 03/30] ima: extend boot_aggregate with kernel measurements Message-ID: <20201211031008.GN489768@sequoia> References: <20200708154116.3199728-1-sashal@kernel.org> <20200708154116.3199728-3-sashal@kernel.org> <1594224793.23056.251.camel@linux.ibm.com> <20200709012735.GX2722994@sasha-vm> <5b8dcdaf66fbe2a39631833b03772a11613fbbbf.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5b8dcdaf66fbe2a39631833b03772a11613fbbbf.camel@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On 2020-11-29 08:17:38, Mimi Zohar wrote: > Hi Sasha, > > On Wed, 2020-07-08 at 21:27 -0400, Sasha Levin wrote: > > On Wed, Jul 08, 2020 at 12:13:13PM -0400, Mimi Zohar wrote: > > >Hi Sasha, > > > > > >On Wed, 2020-07-08 at 11:40 -0400, Sasha Levin wrote: > > >> From: Maurizio Drocco > > >> > > >> [ Upstream commit 20c59ce010f84300f6c655d32db2610d3433f85c ] > > >> > > >> Registers 8-9 are used to store measurements of the kernel and its > > >> command line (e.g., grub2 bootloader with tpm module enabled). IMA > > >> should include them in the boot aggregate. Registers 8-9 should be > > >> only included in non-SHA1 digests to avoid ambiguity. > > > > > >Prior to Linux 5.8, the SHA1 template data hashes were padded before > > >being extended into the TPM. Support for calculating and extending > > >the per TPM bank template data digests is only being upstreamed in > > >Linux 5.8. > > > > > >How will attestation servers know whether to include PCRs 8 & 9 in the > > >the boot_aggregate calculation? Now, there is a direct relationship > > >between the template data SHA1 padded digest not including PCRs 8 & 9, > > >and the new per TPM bank template data digest including them. > > > > Got it, I'll drop it then, thank you! > > After re-thinking this over, I realized that the attestation server can > verify the "boot_aggregate" based on the quoted PCRs without knowing > whether padded SHA1 hashes or per TPM bank hash values were extended > into the TPM[1], but non-SHA1 boot aggregate values [2] should always > include PCRs 8 & 9. I'm still not clear on how an attestation server would know to include PCRs 8 and 9 after this change came through a stable kernel update. It doesn't seem like something appropriate for stable since it requires code changes to attestation servers to handle the change. I know this has already been released in some stable releases, so I'm too late, but perhaps I'm missing something. Tyler > > Any place commit 6f1a1d103b48 was backported [2], this commit > 20c59ce010f8 ("ima: extend boot_aggregate with kernel measurements") > should be backported as well. > > thanks, > > Mimi > > [1] commit 1ea973df6e21 ("ima: Calculate and extend PCR with digests in ima_template_entry") > [2] commit 6f1a1d103b48 ("ima: Switch to ima_hash_algo for boot aggregate") >