Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756611AbcK2VaL (ORCPT ); Tue, 29 Nov 2016 16:30:11 -0500 Received: from b.ns.miles-group.at ([95.130.255.144]:44725 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751537AbcK2VaD (ORCPT ); Tue, 29 Nov 2016 16:30:03 -0500 To: linux-fsdevel Cc: "linux-kernel@vger.kernel.org" , Ext4 Developers List , mhalcrow@google.com, tytso@mit.edu, muslukhovi@gmail.com, David Gstir From: Richard Weinberger Subject: Idea behind EXT4_IOC_GET_ENCRYPTION_PWSALT? Message-ID: Date: Tue, 29 Nov 2016 22:30:00 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 684 Lines: 18 Hi! As the subject states, I'm a bit confused wrt. EXT4_IOC_GET_ENCRYPTION_PWSALT. Will common fscrypt userspace depend on it? IIUC you want to store some salt to seed the user password. But what if /home/rw and /home/dags have different keys? Is it okay to use the same salt for both keys? Or is it an ad-hoc solution to allow an encrypted filesystem root because you need a way to store the seed on the same filesystem but not as file since all files are encrypted? Wouldn't a xattr stored in the filesystem root directory also do it? Long story short, I'm not sure whether we really need this ioctl command in UBIFS and what the designated semantics are. :-) Thanks, //richard