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=-7.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 842E2C4338F for ; Tue, 17 Aug 2021 13:05:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62DA560FA0 for ; Tue, 17 Aug 2021 13:05:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237541AbhHQNFn (ORCPT ); Tue, 17 Aug 2021 09:05:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229721AbhHQNFm (ORCPT ); Tue, 17 Aug 2021 09:05:42 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F0BB6C061764 for ; Tue, 17 Aug 2021 06:05:08 -0700 (PDT) Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=[IPv6:::1]) by metis.ext.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1mFymB-0006MT-9m; Tue, 17 Aug 2021 15:05:07 +0200 Subject: Re: [PATCH v2] fscrypt: support trusted keys To: Mimi Zohar , Eric Biggers , Jarkko Sakkinen Cc: "Theodore Y. Ts'o" , Jaegeuk Kim , kernel@pengutronix.de, James Morris , "Serge E. Hallyn" , James Bottomley , Sumit Garg , David Howells , linux-fscrypt@vger.kernel.org, linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, keyrings@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210806150928.27857-1-a.fatoum@pengutronix.de> <20210809094408.4iqwsx77u64usfx6@kernel.org> <20210810180636.vqwaeftv7alsodgn@kernel.org> <20210810212140.sdq5dq2wy5uaj7h7@kernel.org> <20210811001743.ofzkwdwa6rcjsf4d@kernel.org> <0e69a0aa394dd20347b06ae4e700aa17d52583ef.camel@linux.ibm.com> From: Ahmad Fatoum Message-ID: Date: Tue, 17 Aug 2021 15:04:59 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <0e69a0aa394dd20347b06ae4e700aa17d52583ef.camel@linux.ibm.com> Content-Type: text/plain; charset=iso-8859-15 Content-Language: en-US Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: a.fatoum@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On 12.08.21 02:54, Mimi Zohar wrote: > On Wed, 2021-08-11 at 10:16 -0700, Eric Biggers wrote: > >> Neither of you actually answered my question, which is whether the support for >> trusted keys in dm-crypt is a mistake. I think you're saying that it is? That >> would imply that fscrypt shouldn't support trusted keys, but rather encrypted >> keys -- which conflicts with Ahmad's patch which is adding support for trusted >> keys. Note that your reasoning for this is not documented at all in the >> trusted-encrypted keys documentation; it needs to be (email threads don't really >> matter), otherwise how would anyone know when/how to use this feature? > > True, but all of the trusted-encrypted key examples in the > documentation are "encrypted" type keys, encrypted/decrypted based on a > "trusted" type key. There are no examples of using the "trusted" key > type directly. Before claiming that adding "trusted" key support in > dm-crypt was a mistake, we should ask Ahmad why he felt dm-crypt needed > to directly support "trusted" type keys. I wanted to persist the dm-crypt key as a sealed blob. With encrypted keys, I would have to persist and unseal two blobs (load trusted key blob, load encrypted key blob rooted to trusted key) with no extra benefit. I thus added direct support for trusted keys. Jarkko even commented on the thread, but didn't voice objection to the approach (or agreement for that matter), so I assumed the approach is fine. I can see the utility of using a single trusted key for TPMs, but for CAAM, I see none and having an encrypted key for every trusted key just makes it more cumbersome. In v1 here, I added encrypted key support as well, but dropped it for v2, because I am not in a position to justify its use. Now that you and Eric discussed it, should I send v3 with support for both encrypted and trusted keys like with dm-crypt or how should we proceed? Cheers, Ahmad > > Mimi > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |