Fix SOURCE_DATE_EPOCH bug; use UTC

Thanks to Juro Bystricky for the suggestion and prototype.
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4644)

crypto/cversion.c

@@ -18,41 +18,22 @@ unsigned long OpenSSL_version_num(void)
 
 const char *OpenSSL_version(int t)
 {
-    if (t == OPENSSL_VERSION)
+    switch (t) {
+    case OPENSSL_VERSION:
         return OPENSSL_VERSION_TEXT;
-    if (t == OPENSSL_BUILT_ON) {
-#ifdef DATE
-# ifdef OPENSSL_USE_BUILD_DATE
+    case OPENSSL_BUILT_ON:
         return DATE;
-# else
-        return "built on: reproducible build, date unspecified";
-# endif
-#else
-        return "built on: date not available";
-#endif
-    }
-    if (t == OPENSSL_CFLAGS) {
-#ifdef CFLAGS
-        return CFLAGS;
-#else
-        return "compiler: information not available";
-#endif
-    }
-    if (t == OPENSSL_PLATFORM) {
-#ifdef PLATFORM
+    case OPENSSL_CFLAGS:
+        return compiler_flags;
+    case OPENSSL_PLATFORM:
         return PLATFORM;
-#else
-        return "platform: information not available";
-#endif
-    }
-    if (t == OPENSSL_DIR) {
+    case OPENSSL_DIR:
 #ifdef OPENSSLDIR
         return "OPENSSLDIR: \"" OPENSSLDIR "\"";
 #else
         return "OPENSSLDIR: N/A";
 #endif
-    }
-    if (t == OPENSSL_ENGINES_DIR) {
+    case OPENSSL_ENGINES_DIR:
 #ifdef ENGINESDIR
         return "ENGINESDIR: \"" ENGINESDIR "\"";
 #else

util/mkbuildinf.pl

 #! /usr/bin/env perl
-# Copyright 2014-2016 The OpenSSL Project Authors. All Rights Reserved.
+# Copyright 2014-2017 The OpenSSL Project Authors. All Rights Reserved.
 #
 # Licensed under the OpenSSL license (the "License").  You may not use
 # this file except in compliance with the License.  You can obtain a copy
 # in the file LICENSE in the source distribution or at
 # https://www.openssl.org/source/license.html
 
+use strict;
+use warnings;
 
 my ($cflags, $platform) = @ARGV;
-
 $cflags = "compiler: $cflags";
-$date = localtime();
+
+my $date = gmtime($ENV{'SOURCE_DATE_EPOCH'} || time()) . " UTC";
+
 print <<"END_OUTPUT";
-/* auto-generated by util/mkbuildinf.pl for crypto/cversion.c */
-#define CFLAGS cflags
 /*
- * Generate CFLAGS as an array of individual characters. This is a
+ * WARNING: do not edit!
+ * Generated by util/mkbuildinf.pl
+ *
+ * Copyright 2014-2017 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the OpenSSL license (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#define PLATFORM "platform: $platform"
+#define DATE "built on: $date"
+
+/*
+ * Generate compiler_flags as an array of individual characters. This is a
  * workaround for the situation where CFLAGS gets too long for a C90 string
  * literal
  */
-static const char cflags[] = {
+static const char compiler_flags[] = {
 END_OUTPUT
+
 my $ctr = 0;
 foreach my $c (split //, $cflags) {
     $c =~ s|([\\'])|\\$1|;
@@ -36,6 +53,4 @@ foreach my $c (split //, $cflags) {
 print <<"END_OUTPUT";
 '\\0'
 };
-#define PLATFORM "platform: $platform"
-#define DATE "built on: $date"
 END_OUTPUT