[U-Boot] [swupdate] Re: SWUpdate - U-Boot environment library dependency

[Stefano Babic]

Hi Wolfgang,

On 21/11/18 12:45, Wolfgang Denk wrote:
> Dear Stefano,
> 
> In message <9efc8990-118c-d5b9-802d-8190db2326d3 at denx.de> you wrote:
>>
>> True, but this has side effect and limitation. You cannot change a
>> variable in the deafult environment if you need it because you do not
>> know it. If some changes are needed, even if for very small things like
>> activating a gpio before ooting, you need to update the bootloader.
> 
> Just my words.  (Mis) using the default environment for such
> purposes is broken by design.
> 
> Let's get rid of this!
> 
>> Moving to shared library should be done in U-Boot project, then. Some
>> changes are then required, at least how the environment is locked (it is
>> not clean as it is done now - locking should be done by the library and
>> not by the caller).
> 
> Speaking of security...  shared libraries open a number of new
> attack vectors, too...

This is the reason why these libraries are in meta-swupdate built as
static libraries. Up now I had no requests that someone else wants to
use them.

> 
>>> In a secure boot environment, you cannot allow to load the environment
>>> from an untrusted source. We need a default environment in this case.
>>
>> Or you make that changes are trusted.
> 
> Right, when we sign (and check the signatures) of all other images,
> then why not do the very same for some environment image?

The weird thing is with "saveenv" - if we just read the env, it is fine,
but if we want to change it, we need to sign, and this requires a
private key on target.

> 
> That would even be _better_ as currently there is no, absolutely no
> check if the builtin default environment is in any way consistent.

This is not true. If the environment is linked to u-boot, it is signed
together with u-boot and its consistency is automatically verified.

Best regards,
Stefano

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