BUG/MINOR: log: Don't use strftime() which can clobber timezone if chrooted
The strftime() function can call tzset() internally on some platforms.
When haproxy is chrooted, the /etc/localtime file is not found, and some
implementations will clobber the content of the current timezone.
The GMT offset is computed by diffing the times returned by gmtime_r() and
localtime_r(). These variants are guaranteed to not call tzset() and were
already used in haproxy while chrooted, so they should be safe.
This patch must be backported to 1.6 and 1.5.
diff --git a/src/standard.c b/src/standard.c
index e08795f..2fe92ba 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -2552,31 +2552,66 @@
return dst;
}
+/* Base year used to compute leap years */
+#define TM_YEAR_BASE 1900
+
+/* Return the difference in seconds between two times (leap seconds are ignored).
+ * Retrieved from glibc 2.18 source code.
+ */
+static int my_tm_diff(const struct tm *a, const struct tm *b)
+{
+ /* Compute intervening leap days correctly even if year is negative.
+ * Take care to avoid int overflow in leap day calculations,
+ * but it's OK to assume that A and B are close to each other.
+ */
+ int a4 = (a->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (a->tm_year & 3);
+ int b4 = (b->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (b->tm_year & 3);
+ int a100 = a4 / 25 - (a4 % 25 < 0);
+ int b100 = b4 / 25 - (b4 % 25 < 0);
+ int a400 = a100 >> 2;
+ int b400 = b100 >> 2;
+ int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);
+ int years = a->tm_year - b->tm_year;
+ int days = (365 * years + intervening_leap_days
+ + (a->tm_yday - b->tm_yday));
+ return (60 * (60 * (24 * days + (a->tm_hour - b->tm_hour))
+ + (a->tm_min - b->tm_min))
+ + (a->tm_sec - b->tm_sec));
+}
+
/* Return the GMT offset for a specific local time.
+ * Both t and tm must represent the same time.
* The string returned has the same format as returned by strftime(... "%z", tm).
* Offsets are kept in an internal cache for better performances.
*/
-const char *get_gmt_offset(struct tm *tm)
+const char *get_gmt_offset(time_t t, struct tm *tm)
{
/* Cache offsets from GMT (depending on whether DST is active or not) */
static char gmt_offsets[2][5+1] = { "", "" };
- int old_isdst = tm->tm_isdst;
char *gmt_offset;
-
- /* Pretend DST not active if its status is unknown, or strftime() will return an empty string for "%z" */
- if (tm->tm_isdst < 0) {
- tm->tm_isdst = 0;
- }
+ struct tm tm_gmt;
+ int diff;
+ int isdst = tm->tm_isdst;
- /* Fetch the offset and initialize it if needed */
- gmt_offset = gmt_offsets[tm->tm_isdst & 0x01];
- if (unlikely(!*gmt_offset)) {
- strftime(gmt_offset, 5+1, "%z", tm);
- }
+ /* Pretend DST not active if its status is unknown */
+ if (isdst < 0)
+ isdst = 0;
- /* Restore previous DST flag */
- tm->tm_isdst = old_isdst;
+ /* Fetch the offset and initialize it if needed */
+ gmt_offset = gmt_offsets[isdst & 0x01];
+ if (unlikely(!*gmt_offset)) {
+ get_gmtime(t, &tm_gmt);
+ diff = my_tm_diff(tm, &tm_gmt);
+ if (diff < 0) {
+ diff = -diff;
+ *gmt_offset = '-';
+ } else {
+ *gmt_offset = '+';
+ }
+ diff /= 60; /* Convert to minutes */
+ snprintf(gmt_offset+1, 4+1, "%02d%02d", diff/60, diff%60);
+ }
return gmt_offset;
}
@@ -2616,16 +2651,17 @@
/* localdate2str_log: write a date in the format :
* "%02d/%s/%04d:%02d:%02d:%02d +0000(local timezone)" without using snprintf
- * * return a pointer to the last char written (\0) or
- * * NULL if there isn't enough space.
+ * Both t and tm must represent the same time.
+ * return a pointer to the last char written (\0) or
+ * NULL if there isn't enough space.
*/
-char *localdate2str_log(char *dst, struct tm *tm, size_t size)
+char *localdate2str_log(char *dst, time_t t, struct tm *tm, size_t size)
{
const char *gmt_offset;
if (size < 27) /* the size is fixed: 26 chars + \0 */
return NULL;
- gmt_offset = get_gmt_offset(tm);
+ gmt_offset = get_gmt_offset(t, tm);
dst = utoa_pad((unsigned int)tm->tm_mday, dst, 3); // day
*dst++ = '/';