[Buildroot] [PATCH 11/12] reproducibility/fs/iso9660: reproducible iso images

[Yann E. MORIN]

Gilles, All,

On 2016-06-14 17:32 +0200, Gilles Chanteperdrix spake thusly:
> When reproducibility is required, we:
> - run genisoimage with the -creation-date option to avoid using the
>   build date for files in the iso image automatically created by
>   genisoimage (such as the catalog)
> - disable the rockridge extension, as it stores each file "ctime", which
>   can not be changed easily on the host filesystem
> - force using an initrd, as a trying and booting an iso image without
>   the rockridge extensions will not work
> - use isohybrid -i option to avoid embedding a random number in the
>   generated iso.

I'm not too fond of having a huge patch in Buildroot, that has no chance
of ever getting upstream (since upstream is virtually dead as there's
been no activity since Oct 2010, and their homepage is now a blank
page).

Instead, when programs can't be told what date to use, I'd prefer we
have a look at libfaketime:
    https://github.com/wolfcw/libfaketime

Then one can use the 'faketime' wrapper to force a specific date:

    faketime '2016-07-17 21:28:42' genisoimage blablalba

In which case, it might be worth doing it directly in the fs infra so
that all filesystem images are handled once and for all.

Thoughts?

Regards,
Yann E. MORIN.

> Signed-off-by: Gilles Chanteperdrix <gilles.chanteperdrix at xenomai.org>
> ---
>  fs/iso9660/Config.in  |  9 +++++++++
>  fs/iso9660/iso9660.mk | 20 ++++++++++++++++++--
>  2 files changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/iso9660/Config.in b/fs/iso9660/Config.in
> index 2482e44..bb82d03 100644
> --- a/fs/iso9660/Config.in
> +++ b/fs/iso9660/Config.in
> @@ -71,6 +71,15 @@ config BR2_TARGET_ROOTFS_ISO9660_INITRD
>  	  contain a kernel image, an initrd image (unless an initramfs
>  	  linked into the kernel is used) and the bootloader.
>  
> +config BR2_TARGET_ROOTFS_ISO9660_REPRODUCIBLE
> +       def_bool BR2_REPRODUCIBLE
> +       select BR2_TARGET_ROOTFS_ISO9660_INITRD
> +
> +if BR2_REPRODUCIBLE
> +comment "A reproducible build requires disabling the RockRidge extensions"
> +comment "Which makes using an initrd the only sane solution"
> +endif
> +
>  config BR2_TARGET_ROOTFS_ISO9660_HYBRID
>  	bool "Build hybrid image"
>  	depends on BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
> diff --git a/fs/iso9660/iso9660.mk b/fs/iso9660/iso9660.mk
> index 32d79d7..f97a9d7 100644
> --- a/fs/iso9660/iso9660.mk
> +++ b/fs/iso9660/iso9660.mk
> @@ -143,15 +143,31 @@ ROOTFS_ISO9660_PRE_GEN_HOOKS += ROOTFS_ISO9660_DISABLE_EXTERNAL_INITRD
>  endif # ROOTFS_ISO9660_USE_INITRD
>  
>  
> +ifneq ($(BR2_REPRODUCIBLE),y)
> +define ROOTFS_ISO9660_GENISOIMAGE
> +	$(HOST_DIR)/usr/bin/genisoimage -R
> +endef
> +define ROOTFS_ISO9660_ISOHYBRID
> +	$(HOST_DIR)/usr/bin/isohybrid
> +endef
> +else
> +define ROOTFS_ISO9660_GENISOIMAGE
> +	$(HOST_DIR)/usr/bin/genisoimage -creation-date $(SOURCE_DATE_EPOCH)
> +endef
> +define ROOTFS_ISO9660_ISOHYBRID
> +	$(HOST_DIR)/usr/bin/isohybrid -i $(SOURCE_DATE_EPOCH)
> +endef
> +endif
> +
>  define ROOTFS_ISO9660_CMD
> -	$(HOST_DIR)/usr/bin/genisoimage -J -R -b $(ROOTFS_ISO9660_BOOT_IMAGE) \
> +	$(ROOTFS_ISO9660_GENISOIMAGE) -J -b $(ROOTFS_ISO9660_BOOT_IMAGE) \
>  		-no-emul-boot -boot-load-size 4 -boot-info-table \
>  		-o $@ $(ROOTFS_ISO9660_TARGET_DIR)
>  endef
>  
>  ifeq ($(BR2_TARGET_ROOTFS_ISO9660_HYBRID),y)
>  define ROOTFS_ISO9660_GEN_HYBRID
> -	$(HOST_DIR)/usr/bin/isohybrid -t 0x96 $@
> +	$(ROOTFS_ISO9660_ISOHYBRID) -t 0x96 $@
>  endef
>  
>  ROOTFS_ISO9660_POST_GEN_HOOKS += ROOTFS_ISO9660_GEN_HYBRID
> -- 
> 2.8.2
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

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