[U-Boot] Integity validation (checksum) of a squashfs root file system

[Marek Vasut <marek.vasut@gmail.com>]

> Hi,
> 
> I would like to validate the integrity (checksum) of a squashfs root file
> system before starting Linux.
> 
> Current strategy I am using is:
> - Wrap squashfs rootfs inside a u-boot image
> - TFTP download on the target
> - Download validation using iminfo
> - Save squashfs rootfs in flash without the image header (Linux failed to
> load squashfs rootfs if u-boot image is present)
> 
> Problems:
> - I need to hardcode squashfs rootfs offset in u-boot image in order to be
> able to flash it - U-Boot image header information (size, crc, ...) is
> lost after a reboot. It is not possible to check the integrity of the
> flash content.
> 
> I would like to save some fields of u-boot image header (size, crc, ...) 
> in u-boot environment variables. And then do an integrity check at boot
> time.
> 
> I have not find a way to extract those fields and save them without
> changing u-boot code. I have added some code to ?iminfo? command to set
> environment variables for CRC, size, payload offset, timestamp.
> 
> Is it an acceptable way of doing it?
> Is there a better way of doing it?
> 
> Thanks in advance,
> 
> Pascal

Use sha1sum integrated into uboot and stick it at the end?

M