+ /*
+ * Checking for two-digit years first in an
+ * attempt to work around GNU libc's strptime()
+ * reporting negative year values when using %Y.
+ */
+ static const char time_formats[][22] = {
+ /* Tue, 02-Jun-37 20:00:00 */
+ "%a, %d-%b-%y %H:%M:%S",
+ /* Tue, 02 Jun 2037 20:00:00 */
+ "%a, %d %b %Y %H:%M:%S",
+ /* Tue, 02-Jun-2037 20:00:00 */
+ "%a, %d-%b-%Y %H:%M:%S",
+ /* Tuesday, 02-Jun-2037 20:00:00 */
+ "%A, %d-%b-%Y %H:%M:%S",
+ /* Tuesday Jun 02 20:00:00 2037 */
+ "%A %b %d %H:%M:%S %Y"
+ };
+ unsigned int i;
+
+ for (i = 0; i < SZ(time_formats); i++)
+ {
+ /*
+ * Zero out gmt to prevent time zone offsets.
+ * Documented to be required for GNU libc.
+ */
+ memset(&gmt, 0, sizeof(gmt));
+
+ if (NULL != strptime(header_time, time_formats[i], &gmt))
+ {
+ /* Sanity check for GNU libc. */
+ if (gmt.tm_year < 0)
+ {
+ log_error(LOG_LEVEL_HEADER,
+ "Failed to parse '%s' using '%s'. Moving on.",
+ header_time, time_formats[i]);
+ continue;
+ }
+ *result = timegm(&gmt);
+
+#ifdef FEATURE_STRPTIME_SANITY_CHECKS
+ /*
+ * Verify that parsing the date recreated from the first
+ * parse operation gets the previous result. If it doesn't,
+ * either strptime() or strftime() are malfunctioning.
+ *
+ * We could string-compare the recreated date with the original
+ * header date, but this leads to false positives as strptime()
+ * may let %a accept all day formats while strftime() will only
+ * create one.
+ */
+ {
+ char recreated_date[100];
+ struct tm *tm;
+ struct tm storage;
+ time_t result2;
+
+ tm = privoxy_gmtime_r(result, &storage);
+ if (!strftime(recreated_date, sizeof(recreated_date),
+ time_formats[i], tm))
+ {
+ log_error(LOG_LEVEL_ERROR, "Failed to recreate date '%s' with '%s'.",
+ header_time, time_formats[i]);
+ continue;
+ }
+ memset(&gmt, 0, sizeof(gmt));
+ if (NULL == strptime(recreated_date, time_formats[i], &gmt))
+ {
+ log_error(LOG_LEVEL_ERROR,
+ "Failed to parse '%s' generated with '%s' to recreate '%s'.",
+ recreated_date, time_formats[i], header_time);
+ continue;
+ }
+ result2 = timegm(&gmt);
+ if (*result != result2)
+ {
+ log_error(LOG_LEVEL_ERROR, "strftime() and strptime() disagree. "
+ "Format: '%s'. In: '%s', out: '%s'. %ld != %ld. Rejecting.",
+ time_formats[i], header_time, recreated_date, *result, result2);
+ continue;
+ }
+ }
+#endif
+
+ return JB_ERR_OK;
+ }
+ }
+
+ return JB_ERR_PARSE;
+
+}
+
+/*********************************************************************
+ *
+ * Function : parse_time_header
+ *
+ * Description : Parses the time in an HTTP time header to get
+ * the numerical respresentation.
+ *
+ * Parameters :
+ * 1 : header = HTTP header with a time value
+ * 2 : result = storage for header_time in seconds
+ *
+ * Returns : JB_ERR_OK if the time format was recognized, or
+ * JB_ERR_PARSE otherwise.
+ *
+ *********************************************************************/
+static jb_err parse_time_header(const char *header, time_t *result)
+{
+ const char *header_time;
+
+ header_time = strchr(header, ':');