options: treat time strings as UTC times

When parsing user supplied time strings, calculate an UTC time instant by
substracting the current zone offset from the result of mktime(3), then use
gmtime_r(3) to turn the time_t value back into a sanitized time structure.

This ensures that user supplied dates are not interpreted as local time.

Fixes FS#1483.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

diff --git a/options.c b/options.c
index b5d5c02ff2fa24f0c1f6bc057b56dd1c64451cb8..087aa630469afa8eea81238a4fb9c6accc44d414 100644 (file)
--- a/options.c
+++ b/options.c
@@ -641,6 +641,7 @@ fw3_parse_date(void *ptr, const char *val, bool is_list)
 {
        unsigned int year = 1970, mon = 1, day = 1, hour = 0, min = 0, sec = 0;
        struct tm tm = { 0 };
+       time_t ts;
        char *p;
 
        year = strtoul(val, &p, 10);
@@ -685,9 +686,11 @@ ret:
        tm.tm_min  = min;
        tm.tm_sec  = sec;
 
-       if (mktime(&tm) >= 0)
+       ts = mktime(&tm) - timezone;
+
+       if (ts >= 0)
        {
-               *((struct tm *)ptr) = tm;
+               gmtime_r(&ts, (struct tm *)ptr);
                return true;
        }