From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/13597 Path: news.gmane.org!.POSTED!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: Use local time in syslog() function Date: Mon, 14 Jan 2019 15:27:26 -0500 Message-ID: <20190114202726.GE23599@brightrain.aerifal.cx> References: <20190114102303.Horde.cORQXioih5pWeAh2Yr2gztG@webmail.michael-kaufmann.ch> <20190114162534.GD23599@brightrain.aerifal.cx> <20190114205345.Horde.IcnVhJs0RGJWUQBLwJoyrNv@webmail.michael-kaufmann.ch> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1547497533 2346 195.159.176.226 (14 Jan 2019 20:25:33 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 14 Jan 2019 20:25:33 +0000 (UTC) User-Agent: Mutt/1.5.21 (2010-09-15) To: musl@lists.openwall.com Original-X-From: musl-return-13613-gllmg-musl=m.gmane.org@lists.openwall.com Mon Jan 14 21:25:29 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.84_2) (envelope-from ) id 1gj8nZ-0000V3-Hl for gllmg-musl@m.gmane.org; Mon, 14 Jan 2019 21:25:29 +0100 Original-Received: (qmail 22132 invoked by uid 550); 14 Jan 2019 20:27:39 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 22105 invoked from network); 14 Jan 2019 20:27:38 -0000 Content-Disposition: inline In-Reply-To: <20190114205345.Horde.IcnVhJs0RGJWUQBLwJoyrNv@webmail.michael-kaufmann.ch> Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:13597 Archived-At: On Mon, Jan 14, 2019 at 08:53:45PM +0100, Michael Kaufmann wrote: > >>I have found a bug in the implementation of syslog(). It should use > >>the local time instead of UTC when sending the message to /dev/log. > >>So in src/misc/syslog.c, the call to gmtime_r() should be replaced > >>with localtime_r(). > > > >This is not a bug; rather, use of local time there in glibc and other > >systems is a bug. Local time varies by the sending process and > >produces inconsistent and uninterpretable log messages. Moreover the > >syslog() function is not specified to depend on the environment and > >thereby is not allowed to call any function whose behavior is > >dependant on the environment. > > Thank you for responding! > > I agree that GMT would have been a better choice, but I think local > time is also mandated by RFC 3164, > https://tools.ietf.org/html/rfc3164#section-4.1.2 : "The TIMESTAMP > field is the local time". Or does this RFC not apply for syslog() on > Linux? I'm not sure. Nominally it governs the udp protocol over a network, not the interface between local processes and syslogd over /dev/log (unix domain socket), so in that sense the answer is no, but of course in some sense it's the same protocol. 4.2 goes on to say: "It should be reiterated here that the payload of any IP packet destined to UDP port 514 MUST be considered to be a valid syslog message. It is, however, RECOMMENDED that the syslog packet have all of the parts described in Section 4.1..." and: "If the originally formed message has a TIMESTAMP in the HEADER part, then it SHOULD be the local time of the device within its timezone." "Local time of the device" is not defined anywhere, and in an environment where processes on a "device" (host?) could all have different local times, again the only reasonable choice for the device zone seems to be UTC. One possible interpretation would be using /etc/localtime unconditionally (ignoring $TZ) for syslog purposes, but that would be a lot more work and would reintroduce all of the problems of local time log messages. It's far cleaner to simply configure the logging process to be aware that the zone of the system sending the log messages is UTC, if it needs to be. > There's also this older discussion: > https://www.openwall.com/lists/musl/2014/01/28/2 - sorry, I have not > found it before. Yes, I should have cited it but didn't have it handy. Rich