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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 D40BFC4321D for ; Tue, 21 Aug 2018 07:21:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D0F4214C4 for ; Tue, 21 Aug 2018 07:21:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D0F4214C4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726698AbeHUKkT (ORCPT ); Tue, 21 Aug 2018 06:40:19 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38446 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726253AbeHUKkT (ORCPT ); Tue, 21 Aug 2018 06:40:19 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D0FFC7D84D; Tue, 21 Aug 2018 07:21:20 +0000 (UTC) Received: from localhost (unknown [10.43.134.11]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C0BDA10075DF; Tue, 21 Aug 2018 07:21:15 +0000 (UTC) Date: Tue, 21 Aug 2018 09:21:14 +0200 From: Miroslav Lichvar To: Ondrej Mosnacek Cc: Thomas Gleixner , linux-audit@redhat.com, Paul Moore , Richard Guy Briggs , Steve Grubb , John Stultz , Stephen Boyd , LKML Subject: Re: [RFC PATCH ghak10 v4 0/2] audit: Log modifying adjtimex(2) calls Message-ID: <20180821072114.GC23069@localhost> References: <20180820123818.27547-1-omosnace@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.0 (2018-05-17) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.3 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Tue, 21 Aug 2018 07:21:20 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Tue, 21 Aug 2018 07:21:20 +0000 (UTC) for IP:'10.11.54.3' DOMAIN:'int-mx03.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mlichvar@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Mon, 20 Aug 2018, Ondrej Mosnacek wrote: > > @John or other timekeeping/NTP folks: We had a discussion on the audit > > ML on which of the internal timekeeping/NTP variables we should actually > > log changes for. We are only interested in variables that can (directly > > or indirectly) cause noticeable changes to the system clock, but since we > > have only limited understanding of the NTP code, we would like to ask > > you for advice on which variables are security relevant. I guess that mostly depends on whether you consider setting the clock to run faster or slower than real time to be an important event for the audit. > > - NTP value adjustments: > > - time_offset (probably important) This can adjust the clock by up to 0.5 seconds per call and also speed it up or slow down by up to about 0.05% (43 seconds per day). > > - time_freq (maybe not important?) This can speed up or slow down by up to about 0.05%. > > - time_status (likely important, can cause leap second injection) Yes, it can insert/delete leap seconds and it also enables/disables synchronization of the hardware real-time clock. > > - time_maxerror (maybe not important?) > > - time_esterror (maybe not important?) These two change the error estimates that are reported to applications using ntp_gettime()/adjtimex(). If an application was periodically checking that the clock is synchronized with some specified accuracy and setting the maxerror to a larger value would cause the application to abort, would it be an important event in the audit? > > - time_constant (???) This controls the speed of the clock adjustments that are made when time_offset is set. Probably not important for the audit. > > - time_adjust (sounds important) This is similar to time_freq. It can temporarily speed up or slow down the clock by up to 0.05%. > > - tick_usec (???) This is a more extreme version of time_freq. It can speed up or slow down the clock by up to 10%. -- Miroslav Lichvar