From b5d36aaa8ad9b0aee720b7a6b3270d561a27cb6f Mon Sep 17 00:00:00 2001
From: Jon Turney <jon.turney@dronecode.org.uk>
Date: Wed, 15 Jan 2020 17:03:48 +0000
Subject: [PATCH] Identify reproducible builds in 'objdump -p' output for PE
files
These are produced by MSVC when the '/Brepro' flag is used.
To quote from the PE specification [1]:
"The presence of an entry of type IMAGE_DEBUG_TYPE_REPRO indicates the
PE file is built in a way to achieve determinism or reproducibility. If
the input does not change, the output PE file is guaranteed to be
bit-for-bit identical no matter when or where the PE is produced.
Various date/time stamp fields in the PE file are filled with part or
all the bits from a calculated hash value that uses PE file content as
input, and therefore no longer represent the actual date and time when a
PE file or related specific data within the PE is produced. The raw data
of this debug entry may be empty, or may contain a calculated hash value
preceded by a four-byte value that represents the hash value length."
[1] https://docs.microsoft.com/en-us/windows/win32/debug/pe-format
bfd/ChangeLog:
2020-01-16 Jon Turney <jon.turney@dronecode.org.uk>
* peXXigen.c (pe_is_repro): New function.
(_bfd_XX_print_private_bfd_data_common): Note timestamp is
actually a build hash if PE_IMAGE_DEBUG_TYPE_REPRO is present.
---
bfd/ChangeLog | 6 ++++
bfd/peXXigen.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 86 insertions(+), 5 deletions(-)
diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 43f99b35afd..30766c113e3 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,9 @@
+2020-01-16 Jon Turney <jon.turney@dronecode.org.uk>
+
+ * peXXigen.c (pe_is_repro): New function.
+ (_bfd_XX_print_private_bfd_data_common): Note timestamp is
+ actually a build hash if PE_IMAGE_DEBUG_TYPE_REPRO is present.
+
2020-01-16 Jon Turney <jon.turney@dronecode.org.uk>
* peXXigen.c (debug_type_names): Add names for new debug data type
diff --git a/bfd/peXXigen.c b/bfd/peXXigen.c
index dc7951f8d9f..d9bf0e46236 100644
--- a/bfd/peXXigen.c
+++ b/bfd/peXXigen.c
@@ -2746,6 +2746,71 @@ pe_print_debugdata (bfd * abfd, void * vfile)
return TRUE;
}
+static bfd_boolean
+pe_is_repro (bfd * abfd)
+{
+ pe_data_type *pe = pe_data (abfd);
+ struct internal_extra_pe_aouthdr *extra = &pe->pe_opthdr;
+ asection *section;
+ bfd_byte *data = 0;
+ bfd_size_type dataoff;
+ unsigned int i;
+ bfd_boolean res = FALSE;
+
+ bfd_vma addr = extra->DataDirectory[PE_DEBUG_DATA].VirtualAddress;
+ bfd_size_type size = extra->DataDirectory[PE_DEBUG_DATA].Size;
+
+ if (size == 0)
+ return FALSE;
+
+ addr += extra->ImageBase;
+ for (section = abfd->sections; section != NULL; section = section->next)
+ {
+ if ((addr >= section->vma) && (addr < (section->vma + section->size)))
+ break;
+ }
+
+ if ((section == NULL)
+ || (!(section->flags & SEC_HAS_CONTENTS))
+ || (section->size < size))
+ {
+ return FALSE;
+ }
+
+ dataoff = addr - section->vma;
+
+ if (size > (section->size - dataoff))
+ {
+ return FALSE;
+ }
+
+ if (!bfd_malloc_and_get_section (abfd, section, &data))
+ {
+ if (data != NULL)
+ free (data);
+ return FALSE;
+ }
+
+ for (i = 0; i < size / sizeof (struct external_IMAGE_DEBUG_DIRECTORY); i++)
+ {
+ struct external_IMAGE_DEBUG_DIRECTORY *ext
+ = &((struct external_IMAGE_DEBUG_DIRECTORY *)(data + dataoff))[i];
+ struct internal_IMAGE_DEBUG_DIRECTORY idd;
+
+ _bfd_XXi_swap_debugdir_in (abfd, ext, &idd);
+
+ if (idd.Type == PE_IMAGE_DEBUG_TYPE_REPRO)
+ {
+ res = TRUE;
+ break;
+ }
+ }
+
+ free(data);
+
+ return res;
+}
+
/* Print out the program headers. */
bfd_boolean
@@ -2777,11 +2842,21 @@ _bfd_XX_print_private_bfd_data_common (bfd * abfd, void * vfile)
PF (IMAGE_FILE_BYTES_REVERSED_HI, "big endian");
#undef PF
- /* ctime implies '\n'. */
- {
- time_t t = pe->coff.timestamp;
- fprintf (file, "\nTime/Date\t\t%s", ctime (&t));
- }
+ /*
+ If a PE_IMAGE_DEBUG_TYPE_REPRO entry is present in the debug directory, the
+ timestamp is to be interpreted as the hash of a reproducible build.
+ */
+ if (pe_is_repro (abfd))
+ {
+ fprintf (file, "\nTime/Date\t\t%08lx", pe->coff.timestamp);
+ fprintf (file, "\t(This is a reproducible build file hash, not a timestamp)\n");
+ }
+ else
+ {
+ /* ctime implies '\n'. */
+ time_t t = pe->coff.timestamp;
+ fprintf (file, "\nTime/Date\t\t%s", ctime (&t));
+ }
#ifndef IMAGE_NT_OPTIONAL_HDR_MAGIC
# define IMAGE_NT_OPTIONAL_HDR_MAGIC 0x10b
--
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