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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 EB51BC432C3 for ; Fri, 15 Nov 2019 17:29:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C888C2073B for ; Fri, 15 Nov 2019 17:29:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727626AbfKOR3x (ORCPT ); Fri, 15 Nov 2019 12:29:53 -0500 Received: from mga04.intel.com ([192.55.52.120]:14118 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727543AbfKOR3x (ORCPT ); Fri, 15 Nov 2019 12:29:53 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Nov 2019 09:29:52 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,308,1569308400"; d="scan'208";a="288613668" Received: from sgaffney-mobl3.amr.corp.intel.com (HELO localhost) ([10.252.4.81]) by orsmga001.jf.intel.com with ESMTP; 15 Nov 2019 09:29:45 -0800 Date: Fri, 15 Nov 2019 19:29:44 +0200 From: Jarkko Sakkinen To: David Howells , 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 , g@linux.intel.com Subject: Re: [PATCH] fscrypt: support passing a keyring key to FS_IOC_ADD_ENCRYPTION_KEY Message-ID: <20191115172944.GB21300@linux.intel.com> References: <20191107001259.115018-1-ebiggers@kernel.org> <20191113203550.GI221701@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191113203550.GI221701@gmail.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo 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 13, 2019 at 12:35:51PM -0800, Eric Biggers wrote: > 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? Thanks for reminding. Still catching up with keyring. I gave some feedback to the patch. /Jarkko