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=-3.8 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 7D1D9C3F68F for ; Fri, 3 Jan 2020 16:57:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5533A222C4 for ; Fri, 3 Jan 2020 16:57:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578070650; bh=RL+yaap+s7Gb++esPrb+ddyBAFUgLJGNTPp2fhE5Iv0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=mveQWkPBKzPaopzkK2TkNtghClW98rk5a05OjWMrTs7Ed4u83hGajQaydEVZONGUY Y08+wmXS5BVCFTc8HnHxN/GEkvc4Q59Kl8aYrLgPFPfWhNLwYL2hol9A8ivRwhvNRq Du2QCCV8pr6CsoAViRmwNZgn13Jfpb5pcjqYZtcM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728061AbgACQ5a (ORCPT ); Fri, 3 Jan 2020 11:57:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:49830 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727969AbgACQ53 (ORCPT ); Fri, 3 Jan 2020 11:57:29 -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 C5DA7206DB; Fri, 3 Jan 2020 16:57:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578070649; bh=RL+yaap+s7Gb++esPrb+ddyBAFUgLJGNTPp2fhE5Iv0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kxXw7SXw9knA6E1AFwsb7GlSx8TbEgrh+y/7fgxxpaTXB0F5IZCHr/2+nyXyPozfw ILl+8PJ4ckpEtM8xPBGI2xuFFCndo7KoiDhyzVqKfQU8Jg6s2/6sW1x7+8GxdVCmlv Etw2e1txnGpwPLJlYb/D0D+m8j+Y3f1VWe9VXDjA= Date: Fri, 3 Jan 2020 08:57:27 -0800 From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: keyrings@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, "Theodore Y . Ts'o" , Jaegeuk Kim , David Howells , Jarkko Sakkinen , Paul Crowley , Paul Lawrence , Ondrej Mosnacek , Ondrej Kozina Subject: Re: [PATCH v2] fscrypt: support passing a keyring key to FS_IOC_ADD_ENCRYPTION_KEY Message-ID: <20200103165727.GB19521@gmail.com> References: <20191119222447.226853-1-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191119222447.226853-1-ebiggers@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Tue, Nov 19, 2019 at 02:24:47PM -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. > > This patch has been tested using an xfstest which I wrote to test it. > > Signed-off-by: Eric Biggers Applied to fscrypt.git#master for 5.6. - Eric