[PATCH v4 2/6] rsa: add CONFIG_RSA_VERIFY_WITH_PKEY config

[Heinrich Schuchardt]

On 1/17/20 3:24 AM, AKASHI Takahiro wrote:
> On Tue, Jan 14, 2020 at 12:43:40PM +0100, Heinrich Schuchardt wrote:
>> On 1/14/20 8:45 AM, AKASHI Takahiro wrote:
>>> On Wed, Jan 08, 2020 at 01:35:13PM +0100, Heinrich Schuchardt wrote:
>>>> On 11/21/19 1:11 AM, AKASHI Takahiro wrote:
>>>>> In the next couple of commits, under new CONFIG_RSA_VERIFY_WITH_PKEY,
>>>>> rsa_verify() will be extended to be able to perform RSA decryption without
>>>>> additional RSA key properties from FIT image, i.e. rr and n0inv.
>>>>>
>>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
>>>>> Reviewed-by: Simon Glass <sjg at chromium.org>
>>>>
>>>> The patch series does not build for some configurations.
>>>>
>>>>> ---
>>>>>   lib/rsa/Kconfig | 14 ++++++++++++++
>>>>>   1 file changed, 14 insertions(+)
>>>>>
>>>>> diff --git a/lib/rsa/Kconfig b/lib/rsa/Kconfig
>>>>> index 03ffa2969048..71e4c06bf883 100644
>>>>> --- a/lib/rsa/Kconfig
>>>>> +++ b/lib/rsa/Kconfig
>>>>> @@ -30,6 +30,20 @@ config RSA_VERIFY
>>>>>   	help
>>>>>   	  Add RSA signature verification support.
>>>>>
>>>>> +config RSA_VERIFY_WITH_PKEY
>>>>
>>>> For CONFIG_RSA_VERIFY_WITH_PKEY=y and CONFIG_RSA_PUBLIC_KEY_PARSER=n
>>>> I get an error:
>>>
>>> This error is inevitable as both RSA_VERIFY_WITH_PKEY and
>>> RSA_PUBLIC_KEY_PARSER are "select"able configurations with
>>> visible prompts and then
>>
>> No, it is not inevitbable. Just ensure that in the Makefiles all modules
>> are selected that you need for your configuration.
>
> How?
> Can you please show me a simple solution?

ifneq($(CONFIG_RSA_VERIFY_WITH_PKEY)$(CONFIG_RSA_PUBLIC_KEY_PARSER),)
obj-y += foo.o
endif

or

config RSA_VERIFY_WITH_PKEY
	depends on RSA_PUBLIC_KEY_PARSER

or

config RSA_VERIFY_WITH_PKEY
	select RSA_PUBLIC_KEY_PARSER

Best regards

Heinrich

>
> Thanks,
> -Takahiro Akashi
>
>
>>> we should generally avoid potential illegal configurations;
>>
>> Yes, we want to avoid potentially illegal configurations everywhere.
>> This is why we have a randconfig build target.
>>
>> Best regards
>>
>> Heinrich
>>
>>> The one should NOT forcibly select the other as the kernel kconfig
>>> document suggests.
>>>
>>> #  Note:
>>> #        select should be used with care. select will force
>>> #        a symbol to a value without visiting the dependencies.
>>> #        By abusing select you are able to select a symbol FOO even
>>> #        if FOO depends on BAR that is not set.
>>> #        In general use select only for non-visible symbols
>>> #        (no prompts anywhere) and for symbols with no dependencies.
>>> #        That will limit the usefulness but on the other hand avoid
>>> #        the illegal configurations all over.
>>>
>>> -Takahiro Akashi
>>>
>>>
>>>> lib/rsa/rsa-keyprop.c:669: undefined reference to `rsa_parse_pub_key'
>>>>
>>>> RSA_PUBLIC_KEY_PARSER depends on
>>>> ASYMMETRIC_KEY_TYPE [=n] && ASYMMETRIC_PUBLIC_KEY_SUBTYPE [=n]
>>>>
>>>> Please, fix the dependencies.
>>>>
>>>> Best regards
>>>>
>>>> Heinrich
>>>>
>>>>> +	bool "Execute RSA verification without key parameters from FDT"
>>>>> +	depends on RSA
>>>>> +	help
>>>>> +	  The standard RSA-signature verification code (FIT_SIGNATURE) uses
>>>>> +	  pre-calculated key properties, that are stored in fdt blob, in
>>>>> +	  decrypting a signature.
>>>>> +	  This does not suit the use case where there is no way defined to
>>>>> +	  provide such additional key properties in standardized form,
>>>>> +	  particularly UEFI secure boot.
>>>>> +	  This options enables RSA signature verification with a public key
>>>>> +	  directly specified in image_sign_info, where all the necessary
>>>>> +	  key properties will be calculated on the fly in verification code.
>>>>> +
>>>>>   config RSA_SOFTWARE_EXP
>>>>>   	bool "Enable driver for RSA Modular Exponentiation in software"
>>>>>   	depends on DM
>>>>>
>>>
>>
>