2 files changed, 43 insertions, 11 deletions
diff --git a/src/common/util.c b/src/common/util.c
index 525f27b88..c81d0fe87 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -112,19 +112,36 @@ void tv_addms(struct timeval *a, long ms) {
   a->tv_usec %= 1000000;
 }
 
+
+#define IS_LEAPYEAR(y) (!(y % 4) && ((y % 100) || !(y % 400)))
+static int n_leapdays(int y1, int y2) {
+  --y1;
+  --y2;
+  return (y2/4 - y1/4) - (y2/100 - y1/100) + (y2/400 - y1/400);
+}
+static const int days_per_month[] = 
+  { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+
 time_t tor_timegm (struct tm *tm) {
+  /* This is a pretty ironclad timegm implementation, snarfed from Python2.2. 
+   * It's way more brute-force than fiddling with tzset().
+   */
   time_t ret;
-  char *tz;
-
-  tz = getenv("TZ");
-  setenv("TZ", "", 1);
-  tzset();
-  ret = mktime(tm);
-  if (tz)
-      setenv("TZ", tz, 1);
-  else
-      unsetenv("TZ");
-  tzset();
+  unsigned long year, days, hours, minutes;
+  int i;
+  year = tm->tm_year + 1900;
+  assert(year >= 1970);
+  assert(tm->tm_mon >= 0 && tm->tm_mon <= 11);
+  days = 365 * (year-1970) + n_leapdays(1970,year);
+  for (i = 0; i < tm->tm_mon; ++i)
+    days += days_per_month[i];
+  if (tm->tm_mon > 1 && IS_LEAPYEAR(year))
+    ++days;
+  days += tm->tm_mday - 1;
+  hours = days*24 + tm->tm_hour;
+  
+  minutes = hours*60 + tm->tm_min;
+  ret = minutes*60 + tm->tm_sec;
   return ret;
 }
 
diff --git a/src/or/test.c b/src/or/test.c
index 1d3c551b1..bdc6f43fb 100644
--- a/src/or/test.c
+++ b/src/or/test.c
@@ -422,6 +422,7 @@ test_crypto()
 void 
 test_util() {
   struct timeval start, end;
+  struct tm a_time;
 
   start.tv_sec = 5;
   start.tv_usec = 5000;
@@ -447,6 +448,20 @@ test_util() {
 
   test_eq(0L, tv_udiff(&start, &end));
 
+  /* The test values here are confirmed to be correct on a platform
+   * with a working timgm. */
+  a_time.tm_year = 2003-1900;
+  a_time.tm_mon = 7;
+  a_time.tm_mday = 30;
+  a_time.tm_hour = 6;
+  a_time.tm_min = 14;
+  a_time.tm_sec = 55;
+  test_eq((time_t) 1062224095UL, tor_timegm(&a_time));
+  a_time.tm_year = 2004-1900; /* Try a leap year, after feb. */
+  test_eq((time_t) 1093846495UL, tor_timegm(&a_time));
+  a_time.tm_mon = 1;          /* Try a leap year, in feb. */
+  a_time.tm_mday = 10;
+  test_eq((time_t) 1076393695UL, tor_timegm(&a_time));
 }
 
 void