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

[Mattijs Korpershoek]

Hi Alexey,

On lun., mars 04, 2024 at 14:11, Alexey Romanov <avromanov at salutedevices.com> wrote:

> Hello,
>
> On Thu, Feb 15, 2024 at 10:14:13AM +0100, Mattijs Korpershoek wrote:
>> Hi Alexey,
>> 
>> Thank you for the patch.
>> 
>> On jeu., f'evr. 01, 2024 at 12:20, Alexey Romanov <avromanov at 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 at 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
>
> Yeah, pyamlboot also uses the same 'bootloader' partition flashing
> scheme as I present in the patch 2. This is custom Amlogic protocol.
>
>> 
>> 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)
>
> Agree, you are completely right.
>
>> 
>> But both examples could also be in a fastboot flash format:
>> $ fastboot flash serialno ABCDEF
>
> But this case requires to 'serialno' partition definition in schema?
> I didn't fully understand you.

I meant more in a "conceptual way". (from a end user perspective)

"fastboot flash" is generic command that's just supposed to write data
somewhere.

The back-end (partitioning etc) depends on the storage the device uses
so that's a "implementation detail".

In any case, I don't have a proper alternative to what you are proposing
so as send in [1], I'm okay picking this up after some minor review
comments are addressed.

[1] https://lore.kernel.org/all/87jzlcfang.fsf@baylibre.com/

>
>> 
>> 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
>
> -- 
> Thank you,
> Alexey