From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:38488 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751362AbdHVRgE (ORCPT ); Tue, 22 Aug 2017 13:36:04 -0400 Date: Tue, 22 Aug 2017 10:36:00 -0700 From: Eric Biggers To: Anand Jain Cc: "Theodore Y . Ts'o" , linux-fscrypt@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Jaegeuk Kim , Richard Weinberger , Michael Halcrow , Eric Biggers Subject: Re: [PATCH] fscrypt: add a documentation file for filesystem-level encryption Message-ID: <20170822173600.GB9587@gmail.com> References: <20170818194730.61575-1-ebiggers3@gmail.com> <9dcef6c6-a758-ea57-0d51-55f33e365931@oracle.com> <20170821230821.GB8847@gmail.com> <7a34337d-3214-0a8a-5521-7727364cceb4@oracle.com> <20170822030730.GB3577@zzz.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Aug 22, 2017 at 11:35:20PM +0800, Anand Jain wrote: > >> > >> I think AE is the only good solution for this, File-name encryption at > >>this stage won't solve any kind of Evil Maid attack, (as it was quoted > >>somewhere else in ML). > >> > >> > >> Further, below, is define but not used. > >>----- > >> #define FS_AES_256_GCM_KEY_SIZE 32 > >>----- > >> > > > >Yes, authenticated encryption with AES-256-GCM was in an older version of the > >ext4 encryption design document. But unfortunately it was never really thought > >through. The primary problem, even ignoring rollback protection, is that there > >is nowhere to store the per-block metadata (GCM authentication tag and IV) *and* > >have it updated atomicly with the block contents. Recently, dm-integrity solves > >this at the block device layer, but it uses data journaling which is very > >inefficient. This maybe could be implemented more efficiently on a COW > >filesystem like BTRFS. But even after that, another problem is that > >authenticated encryption of file contents only would not stop an attacker from > >swapping around blocks, files, directories, or creating links, etc. > > > Some of the problems to be solved in this area are quite > interesting and challenging and IMO BTRFS fits nicely. Per extent AE > for BTRFS is drafted, it needs scrutiny and constructive feedback. > > Thanks, Anand > > > >Eric > > Where is the code? Is there a design document, and it is it readable by people not as familiar with btrfs? Is the API compatible with ext4, f2fs, and ubifs? Eric