objcopy embeds the current time and ignores SOURCE_DATE_EPOCH making the output unreproducible.

bfd
  * peXXigen.c (_bfd_XXi_only_swap_filehdr_out): If inserting a timestamp, use the value held in the SOURCE_DATE_EPOCH environment variable, if it is defined.
binutils
  * doc/binutils.texi (objcopy): Document change in behaviour of objcopy's --preserve-dates command line option.
ld
  * pe-dll.c (fill_edata): If inserting a timestamp, use the value held in the SOURCE_DATE_EPOCH environment variable, if it is defined.
  * ld.texi (--insert-timestamp): Document change in behaviour.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2023-07-24  Johannes Schauer Marin Rodrigues  <josch@debian.org>
+
+	* peXXigen.c (_bfd_XXi_only_swap_filehdr_out): If inserting a
+	timestamp, use the value held in the SOURCE_DATE_EPOCH environment
+	variable, if it is defined.
+
 2023-07-24  Jose E. Marchesi  <jose.marchesi@oracle.com>
 
 	* reloc.c: New reloc BFD_RELOC_BPF_DISPCALL32.

bfd/peXXigen.c

@@ -838,7 +838,20 @@ _bfd_XXi_only_swap_filehdr_out (bfd * abfd, void * in, void * out)
   /* Use a real timestamp by default, unless the no-insert-timestamp
      option was chosen.  */
   if ((pe_data (abfd)->timestamp) == -1)
-    H_PUT_32 (abfd, time (0), filehdr_out->f_timdat);
+    {
+      time_t now;
+      char *source_date_epoch;
+
+      /* If the SOURCE_DATE_EPOCH environment variable is
+	 defined then use that as the time, otherwise use
+	 the current time.  */
+      source_date_epoch = getenv ("SOURCE_DATE_EPOCH");
+      if (source_date_epoch)
+	now = (time_t) strtoll (source_date_epoch, NULL, 10);
+      else
+	now = time (NULL);
+      H_PUT_32 (abfd, now, filehdr_out->f_timdat);
+    }
   else
     H_PUT_32 (abfd, pe_data (abfd)->timestamp, filehdr_out->f_timdat);
 

binutils/ChangeLog

@@ -1,3 +1,8 @@
+2023-07-24  Johannes Schauer Marin Rodrigues  <josch@debian.org>
+
+	* doc/binutils.texi (objcopy): Document change in behaviour of
+	objcopy's --preserve-dates command line option.
+
 2023-07-09  Fangrui Song  <maskray@google.com>
 
 	PR 30592

binutils/doc/binutils.texi

@@ -1626,6 +1626,11 @@ commands.  If the input was '12345678' then the outputs would be
 Set the access and modification dates of the output file to be the same
 as those of the input file.
 
+This option also copies the date stored in a PE format file's header,
+unless the SOURCE_DATE_EPOCH environment variable is defined.  If it
+is defined then this variable will be used as the date stored in the
+header, interpreted as the number of seconds since the Unix epoch.
+
 @item -D
 @itemx --enable-deterministic-archives
 @cindex deterministic archives

ld/ChangeLog

@@ -1,3 +1,10 @@
+2023-07-24  Johannes Schauer Marin Rodrigues  <josch@debian.org>
+
+	* pe-dll.c (fill_edata): If inserting a timestamp, use the value
+	held in the SOURCE_DATE_EPOCH environment variable, if it is
+	defined.
+	* ld.texi (--insert-timestamp): Document change in behaviour.
+
 2023-07-03  Nick Clifton  <nickc@redhat.com>
 
 	* configure: Regenerate.

ld/ld.texi

@@ -3571,6 +3571,11 @@ can be used to insert a zero value for the timestamp, this ensuring
 that binaries produced from identical sources will compare
 identically.
 
+If @option{--insert-timestamp} is active then the time inserted is
+either the time that the linking takes place or, if the
+@code{SOURCE_DATE_EPOCH} environment variable is defined, the number
+of seconds since Unix epoch as specified by that variable.
+
 @kindex --enable-reloc-section
 @item --enable-reloc-section
 @itemx --disable-reloc-section

ld/pe-dll.c

@@ -1231,7 +1231,18 @@ fill_edata (bfd *abfd, struct bfd_link_info *info ATTRIBUTE_UNUSED)
   memset (edata_d, 0, edata_sz);
 
   if (pe_data (abfd)->timestamp == -1)
-    H_PUT_32 (abfd, time (0), edata_d + 4);
+    {
+      time_t now;
+      char *source_date_epoch;
+
+      source_date_epoch = getenv ("SOURCE_DATE_EPOCH");
+      if (source_date_epoch)
+	now = (time_t) strtoll (source_date_epoch, NULL, 10);
+      else
+	now = time (NULL);
+
+      H_PUT_32 (abfd, now, edata_d + 4);
+    }
   else
     H_PUT_32 (abfd, pe_data (abfd)->timestamp, edata_d + 4);