[U-Boot] [PATCH v2 1/4] Introduce CONFIG_SPL_ABORT_ON_NON_FIT_IMAGE

[Andrew F. Davis <afd@ti.com>]

On 12/06/2016 09:47 PM, Simon Glass wrote:
> Hi Andrew,
> 
> On 5 December 2016 at 17:37, Andrew F. Davis <afd@ti.com> wrote:
>> On 11/14/2016 06:33 PM, Simon Glass wrote:
>>> Hi Andrew,
>>>
>>> On 14 November 2016 at 15:05, Andrew F. Davis <afd@ti.com> wrote:
>>>> On 11/14/2016 02:44 PM, Simon Glass wrote:
>>>>> Hi Andrew,
>>>>>
>>>>> On 14 November 2016 at 12:14, Andrew F. Davis <afd@ti.com> wrote:
>>>>>> Introduce CONFIG_SPL_ABORT_ON_NON_FIT_IMAGE. An SPL which define
>>>>>> this will abort image loading if the image is not a FIT image.
>>>>>>
>>>>>> Signed-off-by: Andrew F. Davis <afd@ti.com>
>>>>>> ---
>>>>>>  Kconfig          | 9 +++++++++
>>>>>>  common/spl/spl.c | 5 +++++
>>>>>>  2 files changed, 14 insertions(+)
>>>>>>
>>>>>> diff --git a/Kconfig b/Kconfig
>>>>>> index 1263d0b..eefebef 100644
>>>>>> --- a/Kconfig
>>>>>> +++ b/Kconfig
>>>>>> @@ -291,6 +291,15 @@ config FIT_IMAGE_POST_PROCESS
>>>>>>           injected into the FIT creation (i.e. the blobs would have been pre-
>>>>>>           processed before being added to the FIT image).
>>>>>>
>>>>>> +config SPL_ABORT_ON_NON_FIT_IMAGE
>>>>>
>>>>> We already have CONFIG_IMAGE_FORMAT_LEGACY so how about
>>>>> CONFIG_SPL_IMAGE_FORMAT_LEGACY instead? It can default to y if secure
>>>>> boot is disabled.
>>>>>
>>>>
>>>> We also already have CONFIG_SPL_ABORT_ON_RAW_IMAGE on which this is
>>>> based. If we only disable legacy image support then RAW images should
>>>> still be allowed, but we will fail early anyway, we will start to need
>>>> an unmaintainable amount of pre-processor logic to to handle the
>>>> different image types and what is allowed/not allowed.
>>>>
>>>> Even worse some boot modes don't seem to support FIT images (net,
>>>> onenand) so these will alway expect legacy to work. Right now we simply
>>>> have to disable these modes.
>>>
>>> IMO CONFIG_SPL_ABORT_ON_RAW_IMAGE should become a positive option, to
>>> fit in with the legacy format. Otherwise we'll get very confused I
>>> think.
>>>
>>
>> I'm not sure what you are suggesting here, would you like
>>
>> CONFIG_SPL_SUPPORT_RAW_IMAGE
>> CONFIG_SPL_SUPPORT_LEGACY_IMAGE
>> CONFIG_SPL_SUPPORT_FIT_IMAGE
>>
>> And then we disable as needed? I'm not sure this will work in our case,
>> as a new image type may be introduced and enabled by default, this will
>> break our board security until we discover this and disabled it. The
>> benefit of a negative option for us is that we can specify we *only*
>> allow FIT, then it will be obvious to someone adding a new image type
>> they will not meet this check and should not put code outside this block.
> 
> I don't think we add new image types often, and they should default to
> n just as we do for U-Boot proper. Although something odd has happened
> with DISABLE_IMAGE_LEGACY.
> 
> his should of thing should be caught in a security review.
> 
> Also you could add something to print a warning if secure boot is
> enabled but insecure boot options are available? Perhaps that should
> be another option, and default to y?
> 
> It's just that it is really hard to deal with multiple negative
> options, so best avoided if we can.
> 

I agree in general, but this time I think this is hard to properly
avoid. All that would be different with a positive option only case
would be a bunch of checks that all other image modes are off, then
block undefining the same code I am here.

Andrew

> Regards,
> Simon
>