[U-Boot] interaction between CONFIG_CMD_SAVEENV and CONFIG_BOOTCOMMAND

[Nicolas le bayon <nlebayon@gmail.com>]

Would that really be enough?  Please keep in mind that "env save" (or
"saveenv") is only responsible for storing the current environment
into persistant storage.  It does not modify the environment at all.
To modify the environment, you can use quite a number of commands,
including "env set", "env import" etc.  You would have to disable all
of these to prevent modifications of the environment settings - and
probably cripple U-Boot to a level where it becomes unusable.

>> Our objective is just to avoid the user to modify the content in the
persistent storage. Indeed, we have to retrieve the original content at
each reboot.
If the user makes something wrong in its current environment, this is its
responsability, but after the reset, we have to gat back the original
content we stored once for all. In that case, saveenv would maybe be
enough, don't you think?

Which exact version of U-Boot are you talking about?
>>  a quite old one, v2015.01 :-( And we do not plan to upgrade this
"primary bootloader" u-boot.

Regards,
Nicolas

2016-09-14 17:00 GMT+02:00 Wolfgang Denk <wd@denx.de>:

> Dear Nicolas,
>
> In message <CAJZhe_gXm8zFhek9zZaXuV6j6CpHHFweS1Fy
> DDGL2B+Gnb+B3Q at mail.gmail.com> you wrote:
> >
> > Of course, the user will be able to modify the content of the script, to
> > fit with their needs. But on our side, provider of this primary
> bootloader,
> > we want to be sure that the environment of this u-boot won't be changed
> by
> > the user, so that we want to disable all access to "saveenv" command.
>
> Would that really be enough?  Please keep in mind that "env save" (or
> "saveenv") is only responsible for storing the current environment
> into persistant storage.  It does not modify the environment at all.
> To modify the environment, you can use quite a number of commands,
> including "env set", "env import" etc.  You would have to disable all
> of these to prevent modifications of the environment settings - and
> probably cripple U-Boot to a level where it becomes unusable.
>
> > That's why we configure: #undef CONFIG_CMD_SAVEENV
> >
> > With this modifications, saveenv command is not available in the u-boot
> > commands, that's nice. But bootcmd is empty. It's like there was an
> > interaction between both settings, maybe the saveenv primitive is
> necessary
> > one time to construct the environment content.
>
> This would be a bug.  Whcih exact version of U-Boot are you talking
> about?
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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> the more certain."                      -- Baron Rothschild, ca. 1800
>