[U-Boot] Hi Simon, Problems about RSA public exponents for verified boot

[Simon Glass]

(sorry, forgot to cc list)

On 9 December 2014 at 07:17, Simon Glass <sjg at chromium.org> wrote:
> Hi,
>
> On 8 December 2014 at 01:54, Duxiaoqiang <duxiaoqiang at huawei.com> wrote:
>> Hi Michael,
>>
>> Thanks for your information.
>>
>> My working result show that public exponent is not the only problem caused by 64bit alignment, there are also some other problems caused by it, for example: load image after verify step.
>
> If you post your console output then perhaps we might be able to suggest a fix.
>
>>
>> May be we should add a patch to cover all 64 bit platform's alignment.
>>
>> For we need verified boot feature to solve some problems, I also spent some time trying to solve the problem.
>>
>> But I am not very familiar with uboot FDT'S design, it may spend me long time so not very convenient for me to solve this problem.
>>
>> So I want to know do you have time to fix this problem recently, and what's your plan.
>
> I haven't tried this on 64-bit ARM. I may be able to do so later in the month.
>
>>
>> Thanks very much.
>>
>> Sincerely
>> Jason
>>>Hi All,
>>>
>>>Apologies for the delayed response, I’ve been on vacation.
>>
>>>Since this was working for you (Duxiaoqiang) previously it suggests that you are using the default public exponent.  If this is still the case you could, as a temporary workaround, remove the public exponent from your public key data to avoid executing the code causing the abort.
>>>
>>>Simon: Yes, we’ll need an alignment-safe version of fdt64_to_cpu.
>>>
>>>Michael
>>
>>>> On 02 Dec 2014, at 12:31 AM, Simon Glass <sjg at chromium.org> wrote:
>>>>
>>>> +Michael, U-Boot mailing list
>>>>
>>>> Hi,
>>>>
>>>> On 30 November 2014 at 19:26, Duxiaoqiang <duxiaoqiang at huawei.com> wrote:
>>>>>
>>>>> Hi Simon
>>>>>
>>>>>
>>>>>
>>>>> When I test verified boot with new version of U-boot and new version of mkimage, I encountered a alignment problem about RSA public key exponents.
>>>>>
>>>>>
>>>>>
>>>>> I tested verified boot successful few months ago with version of 2014.07-rc4, but failed with the same configuration and operations this time.
>>>>>
>>>>>
>>>>>
>>>>> Problem logs as below:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> I debug this problem and noticed that the problem was caused by pulic_exponent’s address: 0xff78a04c, this address was not aligned to 8 byte, but this address was pointed by a uint64 * type of pointer.
>>>>>
>>>>> Panic happened in function rsa_verify_with_keynode, just as below:
>>>>>
>>>>>
>>>>>
>>>>> By compared the u-boot.dtb file that signed with RSA public key, I noticed that there are differences about PUBLIC_EXPONENT.
>>>>>
>>>>> With the older version of mkimage, there’s no public exponent section. And this problem only happens when I use the new version of mkimage tool.
>>>>>
>>>>>
>>>>>
>>>>> I also checked uboot’s code, it seems that there’s lack of mechanism to guarantee the alignment about public exponent section.
>>>>>
>>>>>
>>>>>
>>>>> Can you give some suggestions about this problem. Appreciate your time.
>>>>
>>> >Copying Michael. Perhaps we need a safer version of fdt64_to_cpu()?
>>>>
>>>> But you might be the first to run this on aarch64. I have not tried it
>>>> yet, but I do now have a platform.
>
> REgards,
> Simon