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=-12.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 9955AC2D0A8 for ; Wed, 23 Sep 2020 18:56:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D912235FD for ; Wed, 23 Sep 2020 18:56:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="qUdFn++L" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726680AbgIWS42 (ORCPT ); Wed, 23 Sep 2020 14:56:28 -0400 Received: from linux.microsoft.com ([13.77.154.182]:44306 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726460AbgIWS42 (ORCPT ); Wed, 23 Sep 2020 14:56:28 -0400 Received: from [192.168.254.38] (unknown [47.187.206.220]) by linux.microsoft.com (Postfix) with ESMTPSA id 557EE20B7179; Wed, 23 Sep 2020 11:56:26 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 557EE20B7179 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1600887387; bh=uwZVH+hKIIVKFv+K1bPzJWqdSDUVXBp6JUcQYxnsRrI=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=qUdFn++LAT4vA2tvu8K1c5Cl/qAqAfZdDZ89KrYyASfOsM4Xmiai4vXaT11vsEf1N 1jZlly6d5QA/+idswdCiva/H0kjaoiZ50IagxTZcPRY8FXTmEHeXrmRQm/DhxP8qz5 3adFTFMbP+ClvkbfYhD+L8lgHluLwPew8dbPIpzw= Subject: Re: [PATCH v2 0/4] [RFC] Implement Trampoline File Descriptor To: Pavel Machek 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, mic@digikod.net References: <210d7cd762d5307c2aa1676705b392bd445f1baa> <20200922215326.4603-1-madvenka@linux.microsoft.com> <20200923084232.GB30279@amd> From: "Madhavan T. Venkataraman" Message-ID: <34257bc9-173d-8ef9-0c97-fb6bd0f69ecb@linux.microsoft.com> Date: Wed, 23 Sep 2020 13:56:25 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200923084232.GB30279@amd> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On 9/23/20 3:42 AM, Pavel Machek wrote: > Hi! > >> Solution proposed in this RFC >> ============================= >> >> >From this RFC's perspective, there are two scenarios for dynamic code: >> >> Scenario 1 >> ---------- >> >> We know what code we need only at runtime. For instance, JIT code generated >> for frequently executed Java methods. Only at runtime do we know what >> methods need to be JIT compiled. Such code cannot be statically defined. It >> has to be generated at runtime. >> >> 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. > > Best regards, > Pavel > 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. Madhavan