Hello,
While investigating reproducible ISO images for Guix¹, I found that
‘grub-mkrescue’ would invoke ’mformat’ without the ‘-N’ option.
Consequently, ‘mformat’ would pick a random serial number, thereby
making the ‘efi.img’ build process non-deterministic.
I came up with the gross hack attached: the ‘grub-mkrescue’ caller can
set the ‘GRUB_FAT_SERIAL_NUMBER’ environment variable, which
‘grub-mkrescue’ translates into a ‘-N’ flag for ‘mformat’.
We could perhaps achieve the same result differently, for instance by
adding an option to ‘grub-mkrescue’.
WDYT?
Thanks,
Ludo’.
¹ https://issues.guix.info/issue/35283
Change 'grub-mkrescue' to honor the 'GRUB_FAT_SERIAL_NUMBER'
environment variable. That way, the caller can specify a fixed
serial number (instead of the randomly chosen one) to create EFI
images (the 'efi.img' file) that are reproducible bit-for-bit.
Patch by Ludovic Courtès <l...@gnu.org>.
--- grub-2.02/util/grub-mkrescue.c 2019-04-20 19:15:26.180242812 +0200
+++ grub-2.02/util/grub-mkrescue.c 2019-04-20 21:56:34.672370849 +0200
@@ -788,8 +788,15 @@ main (int argc, char *argv[])
efiimgfat = grub_util_path_concat (2, iso9660_dir, "efi.img");
int rv;
- rv = grub_util_exec ((const char * []) { "mformat", "-C", "-f", "2880", "-L", "16", "-i",
- efiimgfat, "::", NULL });
+
+ const char *fat_serial_number = getenv ("GRUB_FAT_SERIAL_NUMBER");
+ const char *mformat_args[] =
+ { "mformat", "-C", "-f", "2880", "-L", "16",
+ fat_serial_number != NULL ? "-N" : "-C",
+ fat_serial_number != NULL ? fat_serial_number : "-C",
+ "-i", efiimgfat, "::", NULL };
+
+ rv = grub_util_exec (mformat_args);
if (rv != 0)
grub_util_error ("`%s` invocation failed\n", "mformat");
rv = grub_util_exec ((const char * []) { "mcopy", "-s", "-i", efiimgfat, efidir_efi, "::/", NULL });
_______________________________________________
Bug-grub mailing list
Bug-grub@gnu.org
https://lists.gnu.org/mailman/listinfo/bug-grub
