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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input, and therefore no longer represent the actual date and time when a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.
This commit is contained in:
Jon Turney 2020-01-15 17:03:48 +00:00
parent 1957ab1030
commit b5d36aaa8a
No known key found for this signature in database
GPG Key ID: C7C86F0370285C81
2 changed files with 86 additions and 5 deletions
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6
bfd/ChangeLog
View File

@ -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

85
bfd/peXXigen.c
View File

@ -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