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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 5BE86C4332E for ; Thu, 19 Mar 2020 20:19:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 224E620775 for ; Thu, 19 Mar 2020 20:19:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726619AbgCSUTp (ORCPT ); Thu, 19 Mar 2020 16:19:45 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:54897 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725817AbgCSUTp (ORCPT ); Thu, 19 Mar 2020 16:19:45 -0400 Received: from callcc.thunk.org (pool-72-93-95-157.bstnma.fios.verizon.net [72.93.95.157]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 02JKJEjG024401 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 19 Mar 2020 16:19:14 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id 38C4F420EBA; Thu, 19 Mar 2020 16:19:14 -0400 (EDT) Date: Thu, 19 Mar 2020 16:19:14 -0400 From: "Theodore Y. Ts'o" To: Eric Biggers Cc: linux-fscrypt@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org Subject: Re: [PATCH 1/4] fscrypt: add FS_IOC_GET_ENCRYPTION_NONCE ioctl Message-ID: <20200319201914.GD1067245@mit.edu> References: <20200314205052.93294-1-ebiggers@kernel.org> <20200314205052.93294-2-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200314205052.93294-2-ebiggers@kernel.org> Sender: linux-fscrypt-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fscrypt@vger.kernel.org On Sat, Mar 14, 2020 at 01:50:49PM -0700, Eric Biggers wrote: > From: Eric Biggers > > Add an ioctl FS_IOC_GET_ENCRYPTION_NONCE which retrieves the nonce from > an encrypted file or directory. The nonce is the 16-byte random value > stored in the inode's encryption xattr. It is normally used together > with the master key to derive the inode's actual encryption key. > > The nonces are needed by automated tests that verify the correctness of > the ciphertext on-disk. Except for the IV_INO_LBLK_64 case, there's no > way to replicate a file's ciphertext without knowing that file's nonce. > > The nonces aren't secret, and the existing ciphertext verification tests > in xfstests retrieve them from disk using debugfs or dump.f2fs. But in > environments that lack these debugging tools, getting the nonces by > manually parsing the filesystem structure would be very hard. > > To make this important type of testing much easier, let's just add an > ioctl that retrieves the nonce. > > Signed-off-by: Eric Biggers Reviewed-by: Theodore Ts'o