From: Sami Kerola <kerolasa@iki.fi>
Date: Sun, 15 May 2016 08:50:40 +0000 (+0100)
Subject: utmpdump: use always UTC-0 timezone in textual output
X-Git-Tag: v2.29-rc1~169^2~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3749bdcecfb799619555de2eff9636cb93509eb5;p=thirdparty%2Futil-linux.git

utmpdump: use always UTC-0 timezone in textual output

Converting a time structure from text format that has timezone markup is
practically impossible.  See reference links for more information.  This
leads to situation where multiple utmpdump(1) conversions from binary to
text and back make timestamps to shift amount of timezone offset to UTC-0.

The easiest way to make multiple conversions to work without timeshifts is
to always use UTC-0 timezone.  Downside of this approach is that the textual
format is less human readable than local timestamps would be.

Reference: http://www.catb.org/esr/time-programming/#_strptime_3_and_getdate_3
Reference: http://man7.org/linux/man-pages/man3/strptime.3.html
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
---

diff --git a/login-utils/utmpdump.c b/login-utils/utmpdump.c
index 03cf4a94a6..6eaf202bde 100644
--- a/login-utils/utmpdump.c
+++ b/login-utils/utmpdump.c
@@ -47,10 +47,10 @@
 
 static char *timetostr(const time_t time)
 {
-	static char s[29];	/* [Sun Sep 01 00:00:00 1998 PST] */
+	static char s[29];	/* [Tue Sep 01 00:00:00 1998 GMT] */
 	struct tm *tmp;
 
-	if (time != 0 && (tmp = localtime(&time)))
+	if (time != 0 && (tmp = gmtime(&time)))
 		strftime(s, 29, "%a %b %d %T %Y %Z", tmp);
 	else
 		s[0] = '\0';
@@ -73,7 +73,7 @@ static time_t strtotime(const char *s_time)
 	if (s_time[26] == 'D')
 		tm.tm_isdst = 1;
 
-	return mktime(&tm);
+	return timegm(&tm);
 }
 
 #define cleanse(x) xcleanse(x, sizeof(x))