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=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 8659DC2D0E2 for ; Thu, 24 Sep 2020 16:45:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 46DB42396D for ; Thu, 24 Sep 2020 16:45:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727330AbgIXQpC (ORCPT ); Thu, 24 Sep 2020 12:45:02 -0400 Received: from smtp-42ac.mail.infomaniak.ch ([84.16.66.172]:47395 "EHLO smtp-42ac.mail.infomaniak.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726645AbgIXQpC (ORCPT ); Thu, 24 Sep 2020 12:45:02 -0400 Received: from smtp-2-0001.mail.infomaniak.ch (unknown [10.5.36.108]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4By19B01Y1zlhTqt; Thu, 24 Sep 2020 18:44:30 +0200 (CEST) Received: from ns3096276.ip-94-23-54.eu (unknown [94.23.54.103]) by smtp-2-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4By1972FNszlh8Yx; Thu, 24 Sep 2020 18:44:27 +0200 (CEST) Subject: Re: [PATCH v2 0/4] [RFC] Implement Trampoline File Descriptor To: Pavel Machek , "Madhavan T. Venkataraman" Cc: kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, oleg@redhat.com, x86@kernel.org, luto@kernel.org, David.Laight@ACULAB.COM, fweimer@redhat.com, mark.rutland@arm.com References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200922215326.4603-1-madvenka@linux.microsoft.com> <20200923084232.GB30279@amd> <34257bc9-173d-8ef9-0c97-fb6bd0f69ecb@linux.microsoft.com> <20200923205156.GA12034@duo.ucw.cz> From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= Message-ID: Date: Thu, 24 Sep 2020 18:44:26 +0200 User-Agent: MIME-Version: 1.0 In-Reply-To: <20200923205156.GA12034@duo.ucw.cz> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 23/09/2020 22:51, Pavel Machek wrote: > Hi! > >>>> Scenario 2 >>>> ---------- >>>> >>>> We know what code we need in advance. User trampolines are a good example of >>>> this. It is possible to define such code statically with some help from the >>>> kernel. >>>> >>>> This RFC addresses (2). (1) needs a general purpose trusted code generator >>>> and is out of scope for this RFC. >>> >>> This is slightly less crazy talk than introduction talking about holes >>> in W^X. But it is very, very far from normal Unix system, where you >>> have selection of interpretters to run your malware on (sh, python, >>> awk, emacs, ...) and often you can even compile malware from sources. >>> >>> And as you noted, we don't have "a general purpose trusted code >>> generator" for our systems. >>> >>> I believe you should simply delete confusing "introduction" and >>> provide details of super-secure system where your patches would be >>> useful, instead. >> >> This RFC talks about converting dynamic code (which cannot be authenticated) >> to static code that can be authenticated using signature verification. That >> is the scope of this RFC. >> >> If I have not been clear before, by dynamic code, I mean machine code that is >> dynamic in nature. Scripts are beyond the scope of this RFC. >> >> Also, malware compiled from sources is not dynamic code. That is orthogonal >> to this RFC. If such malware has a valid signature that the kernel permits its >> execution, we have a systemic problem. >> >> I am not saying that script authentication or compiled malware are not problems. >> I am just saying that this RFC is not trying to solve all of the security problems. >> It is trying to define one way to convert dynamic code to static code to address >> one class of problems. > > Well, you don't have to solve all problems at once. > > But solutions have to exist, and AFAIK in this case they don't. You > are armoring doors, but ignoring open windows. FYI, script execution is being addressed (for the kernel part) by this patch series: https://lore.kernel.org/lkml/20200924153228.387737-1-mic@digikod.net/ > > Or very probably you are thinking about something different than > normal desktop distros (Debian 10). Because on my systems, I have > python, gdb and gcc... It doesn't make sense for a tailored security system to leave all these tools available to an attacker. > > It would be nice to specify what other pieces need to be present for > this to make sense -- because it makes no sense on Debian 10. Not all kernel features make sense for a generic/undefined usage, especially specific security mechanisms (e.g. SELinux, Smack, Tomoyo, SafeSetID, LoadPin, IMA, IPE, secure/trusted boot, lockdown, etc.), but they can still be definitely useful. > > Best regards, > Pavel >