Re: [RFC PATCH v2 1/2] fastboot: introduce 'oem board' subcommand

[Mattijs Korpershoek <mkorpershoek@baylibre.com>]

Hi Alexey,

Thank you for the patch.

On jeu., févr. 01, 2024 at 12:20, Alexey Romanov <avromanov@salutedevices.com> wrote:

> Currently, fastboot protocol in U-Boot has no opportunity
> to execute vendor custom code with verifed boot. This patch
> introduce new fastboot subcommand fastboot oem board:<cmd>,
> which allow to run custom oem_board function.
>
> Default implementation is __weak. Vendor must redefine it in
> board/ folder with his own logic.
>
> For example, some vendors have their custom nand/emmc partition
> flashing or erasing. Here some typical command for such use cases:
>
> - flashing:
>
>   $ fastboot stage bootloader.img
>   $ fastboot oem board:write_bootloader
>
> - erasing:
>
>   $ fastboot oem board:erase_env
>
> Signed-off-by: Alexey Romanov <avromanov@salutedevices.com>

Sorry for the delay. I needed time to give this some thoughts and I
waited for Sean to chime as well on this.

I've heard from Neil that this might be related to:
https://github.com/superna9999/pyamlboot/pull/20

I think this can be useful. Not necessarily for writing custom
partitions, but I see this could be used for other things:

1. Provision SoC-specific fuses (serialno/mac addr) at the factory line
   (for production devices)
   Examples:
   $ fastboot oem board:write_serialno ABCDEF
   $ fastboot oem board:write_macaddr AA:BB:CC:DD:EE

2. Access secure storage (via an Trusted Application)

But both examples could also be in a fastboot flash format:
$ fastboot flash serialno ABCDEF

One concern I have is that U-Boot forks might use this command as
an excuse to not makes things generic.

I hope that others will chime in on this as well.
I'd like to discuss this more because once this command is in we cannot
remove it later.

> ---
>  drivers/fastboot/Kconfig      |  7 +++++++
>  drivers/fastboot/fb_command.c | 15 +++++++++++++++
>  include/fastboot.h            |  1 +
>  3 files changed, 23 insertions(+)
>
> diff --git a/drivers/fastboot/Kconfig b/drivers/fastboot/Kconfig
> index a4313d60a9..4d94391a76 100644
> --- a/drivers/fastboot/Kconfig
> +++ b/drivers/fastboot/Kconfig
> @@ -241,6 +241,13 @@ config FASTBOOT_OEM_RUN
>  	  this feature if you are using verified boot, as it will allow an
>  	  attacker to bypass any restrictions you have in place.
>  
> +config FASTBOOT_OEM_BOARD
> +	bool "Enable the 'oem board' command"
> +	help
> +	  This extends the fastboot protocol with an "oem board" command. This
> +	  command allows running vendor custom code defined in board/ files.
> +	  Otherwise, it will do nothing and send fastboot fail.

If we move forward with this, please also document the new command in:
doc/android/fastboot.rst

> +
>  endif # FASTBOOT
>  
>  endmenu
> diff --git a/drivers/fastboot/fb_command.c b/drivers/fastboot/fb_command.c
> index 5fcadcdf50..2298815770 100644
> --- a/drivers/fastboot/fb_command.c
> +++ b/drivers/fastboot/fb_command.c
> @@ -40,6 +40,7 @@ static void reboot_recovery(char *, char *);
>  static void oem_format(char *, char *);
>  static void oem_partconf(char *, char *);
>  static void oem_bootbus(char *, char *);
> +static void oem_board(char *, char *);
>  static void run_ucmd(char *, char *);
>  static void run_acmd(char *, char *);
>  
> @@ -107,6 +108,10 @@ static const struct {
>  		.command = "oem run",
>  		.dispatch = CONFIG_IS_ENABLED(FASTBOOT_OEM_RUN, (run_ucmd), (NULL))
>  	},
> +	[FASTBOOT_COMMAND_OEM_BOARD] = {
> +		.command = "oem board",
> +		.dispatch = CONFIG_IS_ENABLED(FASTBOOT_OEM_BOARD, (oem_board), (NULL))
> +	},
>  	[FASTBOOT_COMMAND_UCMD] = {
>  		.command = "UCmd",
>  		.dispatch = CONFIG_IS_ENABLED(FASTBOOT_UUU_SUPPORT, (run_ucmd), (NULL))
> @@ -490,3 +495,13 @@ static void __maybe_unused oem_bootbus(char *cmd_parameter, char *response)
>  	else
>  		fastboot_okay(NULL, response);
>  }
> +
> +void __weak fastboot_oem_board(char *cmd_parameter, void *data, u32 size, char *response)
> +{
> +	fastboot_fail("oem board function not defined", response);
> +}
> +
> +static void __maybe_unused oem_board(char *cmd_parameter, char *response)
> +{
> +	fastboot_oem_board(cmd_parameter, fastboot_buf_addr, image_size, response);
> +}
> diff --git a/include/fastboot.h b/include/fastboot.h
> index 296451f89d..06c1f26b6c 100644
> --- a/include/fastboot.h
> +++ b/include/fastboot.h
> @@ -37,6 +37,7 @@ enum {
>  	FASTBOOT_COMMAND_OEM_PARTCONF,
>  	FASTBOOT_COMMAND_OEM_BOOTBUS,
>  	FASTBOOT_COMMAND_OEM_RUN,
> +	FASTBOOT_COMMAND_OEM_BOARD,
>  	FASTBOOT_COMMAND_ACMD,
>  	FASTBOOT_COMMAND_UCMD,
>  	FASTBOOT_COMMAND_COUNT
> -- 
> 2.30.1