[OpenWrt-Devel] [PATCH] brcm2708: Implement sysupgrade image check

[Matthias Schiffer]

On 04/07/2016 05:57 PM, Christian Lamparter wrote:
> Implement a crude but functioning sysupgrade image check for Raspberry Pi.
> The code only checks if the master boot record boot signature (0x55aa) is
> present in the first 512-bytes at the correct location. This can prevent
> the odd, accidental bricking of a system when flashing the wrong file.
> 
> The platform check supports both gzipped and raw images.
> 
> Signed-off-by: Christian Lamparter <chunkeey at googlemail.com>
> ---
>  .../linux/brcm2708/base-files/lib/upgrade/platform.sh   | 17 ++++++++++++++++-
>  1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/target/linux/brcm2708/base-files/lib/upgrade/platform.sh b/target/linux/brcm2708/base-files/lib/upgrade/platform.sh
> index 1d4b694..88c30cc 100644
> --- a/target/linux/brcm2708/base-files/lib/upgrade/platform.sh
> +++ b/target/linux/brcm2708/base-files/lib/upgrade/platform.sh
> @@ -1,5 +1,20 @@
> +get_magic_at() {
> +	local file=$1
> +	local pos=$2
> +	( gunzip -c $file 2>/dev/null || cat $file 2>/dev/null ) | dd bs=1 count=2 skip=$pos 2>/dev/null | hexdump -v -n 2 -e '1/1 "%02x"'

Instead of calling gunzip yourself, you should just use get_image (defined
in package/base-files/files/lib/upgrade/common.sh ) as it is done on other
targets, it will transparently deal with compressed and even remote files.

Regards,
Matthias


> +}
> +
>  platform_check_image() {
> -	# i know no way to verify the image
> +	local file=$1
> +	local magic
> +
> +	magic=$(get_magic_at $file 510)
> +
> +	[ "$magic" != "55aa" ] && {
> +		echo "Failed to verify MBR boot signature."
> +		return 1
> +	}
> +
>  	return 0;
>  }
>  
> 


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