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

[Simon Glass]

Hi Andrew,

On 8 February 2017 at 08:18, Andrew F. Davis <afd at ti.com> wrote:
> On 12/06/2016 09:47 PM, Simon Glass wrote:
>> Hi Andrew,
>>
>> On 5 December 2016 at 17:37, Andrew F. Davis <afd at 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 at 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 at 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 at 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 positivoption only case
> would be a bunch of checks that all other image modes are off, then
> block undefining the same code I am here.

But why is SPL different from U-Boot proper on this point? It seems
like we could use the same scheme in SPL as we do in U-Boot proper?

Positive options are easier to understand and combine. If we end up
adding another image format it wouldn't be hard to default it to n if
we are using secure boot.

Regards,
Simon