Fix SMPP timestamp decoding when the current date/time's offset to UTC is

different from the timestamp's offset to UTC.

The fix for bug 6712 ignored the fact that daylight savings will affect the
offset from UTC--and whether daylight savings is in effect today might be
different than whether it was in effect in the timestamp we're decoding.

Bug: 10672
Change-Id: Ie513c361cff41007f2328cd9ca9ca4800ffef500
Reviewed-on: https://code.wireshark.org/review/5245
Petri-Dish: Michael Mann <mmann78@netscape.net>
Petri-Dish: Jeff Morriss <jeff.morriss.ws@gmail.com>
Reviewed-by: Michael Mann <mmann78@netscape.net>

1 files changed, 18 insertions, 17 deletions

diff --git a/epan/dissectors/packet-smpp.c b/epan/dissectors/packet-smpp.c
index a067a02e5f..5bfac61b80 100644
--- a/epan/dissectors/packet-smpp.c
+++ b/epan/dissectors/packet-smpp.c
@@ -1180,34 +1180,35 @@ smpp_mktime(const char *datestr, time_t *secs, int *nsecs)
     if (relative == FALSE) {
         struct tm *gm, *local_time;
         int gm_hour, gm_min;
-        time_t current_time;
 
         *secs = mktime(&r_time);
+        *nsecs = (datestr[12] - '0') * 100000000;
+
+        t_diff = (10 * (datestr[13] - '0') + (datestr[14] - '0')) * 900;
+        if (datestr[15] == '-')
+            /* Represented time is behind UTC, shift it forward to UTC */
+            *secs += t_diff;
+        else if (datestr[15] == '+')
+            /* Represented time is ahead of UTC, shift it backward to UTC */
+            *secs -= t_diff;
 
-        /* Subtract out the timezone information since we will adjust for
-         * the presented time's timezone below and then display in UTC.
+        /* Subtract out the timezone information since we adjusted for
+         * the presented time's timezone above and will display in UTC.
          *
-         * To do that, first determine the current timezone's offset to UTC.
+         * To do that, first determine how the time is represented in the
+         * local time zone and in UTC.
          */
-        current_time = time(NULL);
-        gm = gmtime(&current_time);
+        gm = gmtime(secs);
         gm_hour = gm->tm_hour;
         gm_min = gm->tm_min;
-        local_time = localtime(&current_time);
-        /* Then subtract out that difference (whether the difference is
-         * measured in hours, minutes, or both).
+        local_time = localtime(secs);
+
+        /* Then subtract out the difference between those times (whether the
+         * difference is measured in hours, minutes, or both).
          */
         *secs -= 3600*(gm_hour - local_time->tm_hour);
         *secs -= 60*(gm_min - local_time->tm_min);
 
-        *nsecs = (datestr[12] - '0') * 100000000;
-        t_diff = (10 * (datestr[13] - '0') + (datestr[14] - '0')) * 900;
-        if (datestr[15] == '-')
-            /* Represented time is behind UTC, shift it forward to UTC */
-            *secs += t_diff;
-        else if (datestr[15] == '+')
-            /* Represented time is ahead of UTC, shift it backward to UTC */
-            *secs -= t_diff;
     } else {
         *secs = r_time.tm_sec + 60 *
             (r_time.tm_min + 60 *