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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 CEAA1C35247 for ; Mon, 3 Feb 2020 21:02:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A824D2087E for ; Mon, 3 Feb 2020 21:02:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726272AbgBCVCG (ORCPT ); Mon, 3 Feb 2020 16:02:06 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:54512 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725372AbgBCVCG (ORCPT ); Mon, 3 Feb 2020 16:02:06 -0500 Received: from static-50-53-33-191.bvtn.or.frontiernet.net ([50.53.33.191] helo=[192.168.192.153]) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1iyir5-00030M-0e; Mon, 03 Feb 2020 21:02:03 +0000 Subject: Re: [PATCH v14 22/23] LSM: Add /proc attr entry for full LSM context To: Stephen Smalley , Casey Schaufler , casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org Cc: keescook@chromium.org, penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com References: <20200124002306.3552-1-casey@schaufler-ca.com> <20200124002306.3552-23-casey@schaufler-ca.com> <1de8338a-9c1c-c13b-16f0-e47ebec0e7ea@tycho.nsa.gov> <9afb8d9d-a590-0e13-bf46-53a347ea15dd@schaufler-ca.com> <6bd3e393-e1df-7117-d15a-81cb1946807b@tycho.nsa.gov> From: John Johansen Organization: Canonical Message-ID: Date: Mon, 3 Feb 2020 13:02:00 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <6bd3e393-e1df-7117-d15a-81cb1946807b@tycho.nsa.gov> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Sender: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org On 1/24/20 12:16 PM, Stephen Smalley wrote: > On 1/24/20 2:28 PM, Casey Schaufler wrote: >> On 1/24/2020 8:20 AM, Stephen Smalley wrote: >>> On 1/24/20 9:42 AM, Stephen Smalley wrote: >>>> On 1/23/20 7:23 PM, Casey Schaufler wrote: >>>>> Add an entry /proc/.../attr/context which displays the full >>>>> process security "context" in compound format:' >>>>>           lsm1\0value\0lsm2\0value\0... >>>>> This entry is not writable. >>>>> >>>>> Signed-off-by: Casey Schaufler >>>>> Cc: linux-api@vger.kernel.org >>>> >>>> As previously discussed, there are issues with AppArmor's implementation of getprocattr() particularly around the trailing newline that dbus-daemon and perhaps others would like to see go away in any new interface.  Hence, I don't think we should implement this new API using the existing getprocattr() hook lest it also be locked into the current behavior forever. >>> >>> Also, it would be good if whatever hook is introduced to support /proc/pid/attr/context could also be leveraged by the SO_PEERCONTEXT implementation in the future so that we are guaranteed a consistent result between the two interfaces, unlike the current situation for /proc/self/attr/current versus SO_PEERSEC. >> >> I don't believe that a new hook is necessary, and that introducing one >> just to deal with a '\n' would be pedantic. We really have two rational >> options. AppArmor could drop the '\n' from their "context". Or, we can >> simply document that the /proc/pid/attr/context interface will trim any >> trailing whitespace. I understand that this would be a break from the >> notion that the LSM infrastructure does not constrain what a module uses >> for its own data. On the other hand, we have been saying that "context"s >> are strings, and ignoring trailing whitespace is usual behavior for >> strings. > > Well, you can either introduce a new common underlying hook for use by /proc/pid/attr/context and SO_PEERCONTEXT to produce the string that is to be returned to userspace (in order to guarantee consistency in format and allowing them to be directly compared, which I think is what the dbus maintainers wanted), or you can modify every security module to provide that guarantee in its existing getprocattr and getpeersec* hook functions (SELinux already provides this guarantee; Smack and AppArmor produce slightly different results with respect to \0 and/or \n), or you can have the framework trim the values it gets from the security modules before composing them.  But you need to do one of those things before this interface gets merged upstream. > > Aside from the trailing newline and \0 issues, AppArmor also has a whitespace-separated (mode) field that may or may not be present in the contexts it presently returns, ala "/usr/sbin/cupsd (enforce)".  Not sure what they want for the new interfaces. > It is not needed for the new interface. And if I could go back and remove it from the old interface I would.