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=-9.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 14DE6C433E1 for ; Tue, 26 May 2020 20:44:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5BE0207CB for ; Tue, 26 May 2020 20:44:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="olk2fkRf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403849AbgEZUor (ORCPT ); Tue, 26 May 2020 16:44:47 -0400 Received: from linux.microsoft.com ([13.77.154.182]:52886 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389486AbgEZUor (ORCPT ); Tue, 26 May 2020 16:44:47 -0400 Received: by linux.microsoft.com (Postfix, from userid 1029) id 2C25420B717B; Tue, 26 May 2020 13:44:45 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 2C25420B717B DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1590525885; bh=bFXC2Zh5D+I68ggrZKLkI2DpVS0uyoI3IfAdnK2YDA0=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=olk2fkRfYTmHWVnOEJgWmvdb9kqKsOIxBirUKfxKOh2x/rNdAuN7objslotuhcg/F tu+WrrTYUk1xit3OKtRtTRmj1/csitNlv+beFg1IIadF1sNipjQK5uyqqQ5mKp/18c 8Wiup0o53J2BhaLhCbWA24HTXQBBu3J6qLV3cPcI= Received: from localhost (localhost [127.0.0.1]) by linux.microsoft.com (Postfix) with ESMTP id 284A430705CE; Tue, 26 May 2020 13:44:45 -0700 (PDT) Date: Tue, 26 May 2020 13:44:45 -0700 (PDT) From: Jaskaran Singh Khurana X-X-Sender: jaskarankhurana@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net To: =?ISO-8859-15?Q?Micka=EBl_Sala=FCn?= cc: Deven Bowers , agk@redhat.com, axboe@kernel.dk, snitzer@redhat.com, jmorris@namei.org, serge@hallyn.com, zohar@linux.ibm.com, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, dm-devel@redhat.com, linux-block@vger.kernel.org, jannh@google.com, tyhicks@linux.microsoft.com, pasha.tatashin@soleen.com, sashal@kernel.org, nramas@linux.microsoft.com, mdsakib@linux.microsoft.com, linux-kernel@vger.kernel.org, corbet@lwn.net Subject: Re: [RFC PATCH v3 00/12] Integrity Policy Enforcement LSM (IPE) In-Reply-To: Message-ID: References: <20200415162550.2324-1-deven.desai@linux.microsoft.com> <0001755a-6b2a-b13b-960c-eb0b065c8e3c@linux.microsoft.com> <8ba7b15f-de91-40f7-fc95-115228345fce@linux.microsoft.com> <44fb36ae-959d-4ff7-ed1f-ccfc2e292232@digikod.net> User-Agent: Alpine 2.21 (LRH 202 2017-01-01) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="656392-1229694672-1590525885=:83057" Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --656392-1229694672-1590525885=:83057 Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Transfer-Encoding: 8BIT Hello Mickael, Could you please share your thoughts for the below proposal. Regards, JK On Sat, 16 May 2020, Jaskaran Singh Khurana wrote: > > Hello Mickael, > > On Thu, 14 May 2020, Mickaël Salaün wrote: > >> >> On 12/05/2020 22:46, Deven Bowers wrote: >>> >>> >>> On 5/11/2020 11:03 AM, Deven Bowers wrote: >>>> >>>> >>>> On 5/10/2020 2:28 AM, Mickaël Salaün wrote: >>>> >>>> [...snip] >>>> >>>>>> >>>>>> Additionally, rules are evaluated top-to-bottom. As a result, any >>>>>> revocation rules, or denies should be placed early in the file to >>>>>> ensure >>>>>> that these rules are evaluated before a rule with "action=ALLOW" is >>>>>> hit. >>>>>> >>>>>> IPE policy is designed to be forward compatible and backwards >>>>>> compatible, >>>>>> thus any failure to parse a rule will result in the line being >>>>>> ignored, >>>>>> and a warning being emitted. If backwards compatibility is not >>>>>> required, >>>>>> the kernel commandline parameter and sysctl, ipe.strict_parse can be >>>>>> enabled, which will cause these warnings to be fatal. >>>>> >>>>> Ignoring unknown command may lead to inconsistent beaviors. To achieve >>>>> forward compatibility, I think it would be better to never ignore >>>>> unknown rule but to give a way to userspace to known what is the >>>>> current >>>>> kernel ABI. This could be done with a securityfs file listing the >>>>> current policy grammar. >>>>> >>>> >>>> That's a fair point. From a manual perspective, I think this is fine. >>>> A human-user can interpret a grammar successfully on their own when new >>>> syntax is introduced. >>>> >>>>  From a producing API perspective, I'd have to think about it a bit >>>> more. Ideally, the grammar would be structured in such a way that the >>>> userland >>>> interpreter of this grammar would not have to be updated once new syntax >>>> is introduced, avoiding the need to update the userland binary. To do so >>>> generically ("op=%s") is easy, but doesn't necessarily convey sufficient >>>> information (what happens when a new "op" token is introduced?). I think >>>> this may come down to regular expression representations of valid values >>>> for these tokens, which worries me as regular expressions are incredibly >>>> error-prone[1]. >>>> >>>> I'll see what I can come up with regarding this. >>> >>> I have not found a way that I like to expose some kind of grammar >>> through securityfs that can be understood by usermode to parse the >>> policy. Here's what I propose as a compromise: >>> >>>     1. I remove the unknown command behavior. This address your >>> first point about inconsistent behaviors, and effectively removes the >>> strict_parse sysctl (as it is always enabled). >>> >>>     2. I introduce a versioning system for the properties >>> themselves. The valid set of properties and their versions >>> can be found in securityfs, under say, ipe/config in a key=value >>> format where `key` indicates the understood token, and `value` >>> indicates their current version. For example: >>> >>>     $ cat $SECURITYFS/ipe/config >>>     op=1 >>>     action=1 >>>     policy_name=1 >>>     policy_version=1 >>>     dmverity_signature=1 >>>     dmverity_roothash=1 >>>     boot_verified=1 >> >> The name ipe/config sounds like a file to configure IPE. Maybe something >> like ipe/config_abi or ipe/config_grammar? >> >>> >>> if new syntax is introduced, the version number is increased. >>> >>>     3. The format of those versions are documented as part of >>> the admin-guide around IPE. If user-mode at that point wants to rip >>> the documentation formats and correlate with the versioning, then >>> it fulfills the same functionality as above, with out the complexity >>> around exposing a parsing grammar and interpreting it on-the-fly. >>> Many of these are unlikely to move past version 1, however. >>> >>> Thoughts? >>> >> >> That seems reasonable. >> > > There is a use case for not having strict parsing in the cloud world where > there are multiple versions of OS deployed across a large number of systems > say 100,000 nodes. An OS update can take weeks to complete across all the > nodes, and we end up having a heterogeneous mix of OS versions. > > Without non-strict parsing, to fix an issue in a policy we will need to > update the various versions of the policy (one each for all OS versions > which have different IPE policy schema). We will lose the agility we need to > fix and deploy something urgently in the policy, the nodes might be failing > some critical workloads meanwhile. All the various versions of the policy > will need to be changed and production signed then deployed etc. Further some > versions might introduce newer issues and we will need to see what all > versions of the policy have that bug. > > I propose keeping the non-strict option as well to cater to this use case. > Let me know your thoughts on this. > > Regards, > JK > --656392-1229694672-1590525885=:83057--