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=-5.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 680C2C432C3 for ; Wed, 13 Nov 2019 20:35:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11742206F4 for ; Wed, 13 Nov 2019 20:35:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573677356; bh=F7ZEXH3Tifjy9sGUrwh8Fhs+H6mYs1GYZonZpiJuwEo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=isyeFmURv77b7l0WiDCbu5tYNYoFMXAeRWxA2/C40Fi8k38YePC5Z5QQWsxbBC1b2 nWT20v/G1bED+EfLcny9JP1T1J8KVWvIY6zVJ/FvYlanm+TepVWcriM0gWK4c9fPVi 2Kve81p/wfQ0yZWkl/MRGJ9HE8U8TmqPiHEHVZV4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726516AbfKMUfz (ORCPT ); Wed, 13 Nov 2019 15:35:55 -0500 Received: from mail.kernel.org ([198.145.29.99]:53674 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726162AbfKMUfy (ORCPT ); Wed, 13 Nov 2019 15:35:54 -0500 Received: from gmail.com (unknown [104.132.1.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D1D53206F0; Wed, 13 Nov 2019 20:35:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573677354; bh=F7ZEXH3Tifjy9sGUrwh8Fhs+H6mYs1GYZonZpiJuwEo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cN+5BXj91Btq6Ry/bO1VhiaNdo4x1+Lt3QDXuQLQyXlsCVgrWNJGKLW3Zy0M3qYgf kZYrGKdT5NAbCuJckqXAScixPVqWmbN98LNs2qdXXxKYYq+xhab0ygSaprMlJrUDjc 2Rl8cQmt+I9y4p/mks0qpzDMku7DMTI2kzVonDxM= Date: Wed, 13 Nov 2019 12:35:51 -0800 From: Eric Biggers To: David Howells , Jarkko Sakkinen , keyrings@vger.kernel.org Cc: linux-fscrypt@vger.kernel.org, "Theodore Y . Ts'o" , Ondrej Mosnacek , linux-f2fs-devel@lists.sourceforge.net, Paul Lawrence , linux-mtd@lists.infradead.org, Ondrej Kozina , Jaegeuk Kim , linux-ext4@vger.kernel.org, Paul Crowley Subject: Re: [PATCH] fscrypt: support passing a keyring key to FS_IOC_ADD_ENCRYPTION_KEY Message-ID: <20191113203550.GI221701@gmail.com> Mail-Followup-To: David Howells , Jarkko Sakkinen , keyrings@vger.kernel.org, linux-fscrypt@vger.kernel.org, "Theodore Y . Ts'o" , Ondrej Mosnacek , linux-f2fs-devel@lists.sourceforge.net, Paul Lawrence , linux-mtd@lists.infradead.org, Ondrej Kozina , Jaegeuk Kim , linux-ext4@vger.kernel.org, Paul Crowley References: <20191107001259.115018-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191107001259.115018-1-ebiggers@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fscrypt-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org On Wed, Nov 06, 2019 at 04:12:59PM -0800, Eric Biggers wrote: > From: Eric Biggers > > Extend the FS_IOC_ADD_ENCRYPTION_KEY ioctl to allow the raw key to be > specified by a Linux keyring key, rather than specified directly. > > This is useful because fscrypt keys belong to a particular filesystem > instance, so they are destroyed when that filesystem is unmounted. > Usually this is desired. But in some cases, userspace may need to > unmount and re-mount the filesystem while keeping the keys, e.g. during > a system update. This requires keeping the keys somewhere else too. > > The keys could be kept in memory in a userspace daemon. But depending > on the security architecture and assumptions, it can be preferable to > keep them only in kernel memory, where they are unreadable by userspace. > > We also can't solve this by going back to the original fscrypt API > (where for each file, the master key was looked up in the process's > keyring hierarchy) because that caused lots of problems of its own. > > Therefore, add the ability for FS_IOC_ADD_ENCRYPTION_KEY to accept a > Linux keyring key. This solves the problem by allowing userspace to (if > needed) save the keys securely in a Linux keyring for re-provisioning, > while still using the new fscrypt key management ioctls. > > This is analogous to how dm-crypt accepts a Linux keyring key, but the > key is then stored internally in the dm-crypt data structures rather > than being looked up again each time the dm-crypt device is accessed. > > Use a custom key type "fscrypt-provisioning" rather than one of the > existing key types such as "logon". This is strongly desired because it > enforces that these keys are only usable for a particular purpose: for > fscrypt as input to a particular KDF. Otherwise, the keys could also be > passed to any kernel API that accepts a "logon" key with any service > prefix, e.g. dm-crypt, UBIFS, or (recently proposed) AF_ALG. This would > risk leaking information about the raw key despite it ostensibly being > unreadable. Of course, this mistake has already been made for multiple > kernel APIs; but since this is a new API, let's do it right. > > Signed-off-by: Eric Biggers David and Jarkko, are you okay with this patch from a keyrings subsystem perspective? - Eric