From: Debian DNS Packaging <pkg-dns-devel@lists.alioth.debian.org>
Date: Fri, 24 Nov 2017 16:26:54 +0000
Subject: _reproducible_build

---
 lib/dns/gen.c | 35 +++++++++++++++++++++++++++++++++--
 1 file changed, 33 insertions(+), 2 deletions(-)

diff --git a/lib/dns/gen.c b/lib/dns/gen.c
index 2a3b94b..b26a509 100644
--- a/lib/dns/gen.c
+++ b/lib/dns/gen.c
@@ -32,6 +32,8 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <errno.h>
+#include <limits.h>
 
 #ifdef WIN32
 #include "gen-win32.h"
@@ -528,6 +530,9 @@ main(int argc, char **argv) {
 	char *prefix = NULL;
 	char *suffix = NULL;
 	char *file = NULL;
+	char *source_date_epoch;
+	unsigned long long epoch;
+	char *endptr;
 	isc_dir_t dir;
 
 	for (i = 0; i < TYPENAMES; i++)
@@ -618,8 +623,34 @@ main(int argc, char **argv) {
 	INSIST(n > 0 && (unsigned)n < sizeof(srcdir));
 	sd(0, "", buf, filetype);
 
-	if (time(&now) != -1) {
-		if ((tm = localtime(&now)) != NULL && tm->tm_year > 104) {
+	source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+	if (source_date_epoch) {
+		errno = 0;
+		epoch = strtoull(source_date_epoch, &endptr, 10);
+		if ((errno == ERANGE && (epoch == ULLONG_MAX || epoch == 0))
+				|| (errno != 0 && epoch == 0)) {
+			fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: strtoull: %s\n", strerror(errno));
+			exit(EXIT_FAILURE);
+		}
+		if (endptr == source_date_epoch) {
+			fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: No digits were found: %s\n", endptr);
+			exit(EXIT_FAILURE);
+		}
+		if (*endptr != '\0') {
+			fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: Trailing garbage: %s\n", endptr);
+			exit(EXIT_FAILURE);
+		}
+		if (epoch > ULONG_MAX) {
+			fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: value must be smaller than or equal to: %lu but was found to be: %llu \n", ULONG_MAX, epoch);
+			exit(EXIT_FAILURE);
+		}
+		now = epoch;
+	} else {
+		time(&now);
+	}
+
+	if (now != -1) {
+		if ((tm = gmtime(&now)) != NULL && tm->tm_year > 104) {
 			n = snprintf(year, sizeof(year), "-%d",
 				     tm->tm_year + 1900);
 			INSIST(n > 0 && (unsigned)n < sizeof(year));