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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 CCB7EC433F4 for ; Fri, 31 Aug 2018 20:05:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79B3E2054F for ; Fri, 31 Aug 2018 20:05:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 79B3E2054F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727474AbeIAAOg (ORCPT ); Fri, 31 Aug 2018 20:14:36 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:51939 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726987AbeIAAOg (ORCPT ); Fri, 31 Aug 2018 20:14:36 -0400 Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1fvpfa-0001L3-Dr; Fri, 31 Aug 2018 22:05:26 +0200 Received: from localhost ([127.0.0.1]) by ptx.hi.pengutronix.de with esmtp (Exim 4.89) (envelope-from ) id 1fvpfZ-0004tU-3o; Fri, 31 Aug 2018 22:05:25 +0200 Message-ID: <1535745923.25742.1.camel@pengutronix.de> Subject: Re: [RFC PATCH 00/10] fs-verity: filesystem-level integrity protection From: Jan =?ISO-8859-1?Q?L=FCbbe?= Reply-To: jlu@pengutronix.de To: Eric Biggers , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Cc: linux-integrity@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-kernel@vger.kernel.org, Mimi Zohar , Dmitry Kasatkin , Michael Halcrow , Victor Hsieh Date: Fri, 31 Aug 2018 22:05:23 +0200 In-Reply-To: <20180824161642.1144-1-ebiggers@kernel.org> References: <20180824161642.1144-1-ebiggers@kernel.org> Organization: Pengutronix Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: jlu@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2018-08-24 at 09:16 -0700, Eric Biggers wrote: [...] > Since fs-verity provides the Merkle tree root hash in constant time and > verifies data blocks on-demand, it is useful for efficiently verifying > the authenticity of, or "appraising", large files of which only a small > portion may be accessed -- such as Android application (APK) files.  It > can also be useful in "audit" use cases where file hashes are logged. > fs-verity also provides better protection against malicious disk > firmware than an ahead-of-time hash, since fs-verity re-verifies data > each time it's paged in. [...] > Feedback on the design and implementation is greatly appreciated. Hi, I've looked at the series and the slides linked form the recent lwn.net article, but I'm not sure how fs-verity intends to protect against malicious firmware (or offline modification). Similar to IMA/EVM, fs- verity doesn't seem to include the name/location of the file into it's verification. So the firmware/an attacker could replace one fs-verity- protected file with another (maybe a trusted system APK with another one for which a vulnerability was discovered, or /sbin/init with /bin/sh). Is the expected root hash of the file provided from somewhere else, so this is not a problem on Android? Or is this problem out-of-scope for fs-verity? For IMA/EVM, there were patches by Dmitry to address this class of attacks (they were not merged, though): https://lwn.net/Articles/574221/ Thanks, Jan [1] https://events.linuxfoundation.org/wp-content/uploads/2017/11/fs-ve rify_Mike-Halcrow_Eric-Biggers.pdf -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |