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=-9.8 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 A82D0C433E0 for ; Mon, 15 Jun 2020 16:45:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 815CF2078A for ; Mon, 15 Jun 2020 16:45:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="aUYzJCzF" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731012AbgFOQpu (ORCPT ); Mon, 15 Jun 2020 12:45:50 -0400 Received: from linux.microsoft.com ([13.77.154.182]:55090 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728585AbgFOQpt (ORCPT ); Mon, 15 Jun 2020 12:45:49 -0400 Received: from [192.168.0.104] (c-73-42-176-67.hsd1.wa.comcast.net [73.42.176.67]) by linux.microsoft.com (Postfix) with ESMTPSA id A5BB520B4780; Mon, 15 Jun 2020 09:45:48 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com A5BB520B4780 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1592239548; bh=XWqIoID6oSJi5sFAyDXKdR658vGMUI/XhOZPL0DsKnA=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=aUYzJCzFeQs+E1ArnYzFlomMA/IssGZNCua/12Ubl8cVtJJPgf1aW8IEd6Hb54Zuv 6iWDu3Nyl7+Q6Nu4kCWvt/q8Yq6G05vX28voSp3QubdOutU2hmwJ6pOurhIk+bCe0D ScAH/mqlpvnydpdE9sHA5BOsIkhYeyDjbuQ/DqpY= Subject: Re: [PATCH 4/5] LSM: Define SELinux function to measure security state To: Stephen Smalley Cc: Mimi Zohar , Stephen Smalley , Casey Schaufler , James Morris , linux-integrity@vger.kernel.org, LSM List , linux-kernel References: <20200613024130.3356-1-nramas@linux.microsoft.com> <20200613024130.3356-5-nramas@linux.microsoft.com> From: Lakshmi Ramasubramanian Message-ID: Date: Mon, 15 Jun 2020 09:45:48 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/15/20 4:57 AM, Stephen Smalley wrote: Hi Stephen, Thanks for reviewing the patches. >> +void security_state_change(char *lsm_name, void *state, int state_len) >> +{ >> + ima_lsm_state(lsm_name, state, state_len); >> +} >> + > > What's the benefit of this trivial function instead of just calling > ima_lsm_state() directly? One of the feedback Casey Schaufler had given earlier was that calling an IMA function directly from SELinux (or, any of the Security Modules) would be a layering violation. LSM framework (security/security.c) already calls IMA functions now (for example, ima_bprm_check() is called from security_bprm_check()). I followed the same pattern for measuring LSM data as well. Please let me know if I misunderstood Casey's comment. >> +static int selinux_security_state(char **lsm_name, void **state, >> + int *state_len) >> +{ >> + int rc = 0; >> + char *new_state; >> + static char *security_state_string = "enabled=%d;enforcing=%d"; >> + >> + *lsm_name = kstrdup("selinux", GFP_KERNEL); >> + if (!*lsm_name) >> + return -ENOMEM; >> + >> + new_state = kzalloc(strlen(security_state_string) + 1, GFP_KERNEL); >> + if (!new_state) { >> + kfree(*lsm_name); >> + *lsm_name = NULL; >> + rc = -ENOMEM; >> + goto out; >> + } >> + >> + *state_len = sprintf(new_state, security_state_string, >> + !selinux_disabled(&selinux_state), >> + enforcing_enabled(&selinux_state)); > > I think I mentioned this on a previous version of these patches, but I > would recommend including more than just the enabled and enforcing > states in your measurement. Other low-hanging fruit would be the > other selinux_state booleans (checkreqprot, initialized, > policycap[0..__POLICYDB_CAPABILITY_MAX]). Going a bit further one > could take a hash of the loaded policy by using security_read_policy() > and then computing a hash using whatever hash ima prefers over the > returned data,len pair. You likely also need to think about how to > allow future extensibility of the state in a backward-compatible > manner, so that future additions do not immediately break systems > relying on older measurements. > Sure - I will address this one in the next update. thanks, -lakshmi