Re: [PATCH] efi_loader: explicitly return EFI_UNSUPPORTED for TCG 1.0 compatibility

[Heinrich Schuchardt]

Am 1. Juni 2023 01:35:01 MESZ schrieb Stuart Yoder <stuart.yoder at arm.com>:
>
>
>On 5/31/23 5:09 PM, Heinrich Schuchardt wrote:
>> 
>> 
>> Am 31. Mai 2023 22:40:23 MESZ schrieb Stuart Yoder <stuart.yoder at arm.com>:
>>> 
>>> 
>>> On 5/31/23 3:10 PM, Heinrich Schuchardt wrote:
>>>> On 5/31/23 21:37, Stuart Yoder wrote:
>>>>> 
>>>>> Unfortunately, the TCG spec is very confusing in section 6.4.4 #2 and
>>>>> #3.  They attempted to clarify in an errata:
>>>>> https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-Errata-v.5.pdf
>>>>> 
>>>>> ...but it is still confusing.
>>>>> 
>>>>> Ilias and I had discussed the ambiguities, and back in March 2022 I
>>>>> requested clarification from the TCG workgroup.  In cases of
>>>>> ambiguity TCG frequently will defer to how EDK2 has implemented
>>>>> a point in the spec.
>>>>> 
>>>>> Here are my notes following the call with TCG about the intent
>>>>> of #2 and #3, which was based on their review of the EDK2
>>>>> implementation:
>>>>> 
>>>>> a. If a client passes in a Size that is the full size including all
>>>>>      fields including ActivePcrBanks, the return code is SUCCESS and
>>>>>      all fields are populated. [This is a 1.1 client scenario]
>>>>> 
>>>>> b. If a client passes in a Size that includes all fields up to
>>>>>      and including the vendor ID, the return code is SUCCESS and all
>>>>>      fields up to including the vendor ID are populated. [This is a
>>>>>      1.0 client scenario, so a populated 1.0 struct is returned]
>>>> 
>>>> This contradicts the TCG EFI Protocol Specifiction which knows of no 1.0
>>>> structure but requires:
>>>> 
>>>> If the input ProtocolCapability.Size <
>>>> sizeof(EFI_TCG2_BOOT_SERVICE_CAPABILITY) the function will initialize
>>>> the fields included in ProtocolCapability.Size. The values of the
>>>> remaining fields will be undefined.
>>>> 
>>>> We should stick with what is specified.
>>>> 
>>>> The above requirement is not yet implemented in U-Boot.
>>>> 
>>>> Could you, please, indicated where the 1.0 structure was ever defined. I
>>>> could not find any a document linked on
>>>> https://trustedcomputinggroup.org/resource/tcg-efi-protocol-specification/
>>> 
>>> I can't find any public spec with the 1.0 struct.
>> 
>> If it does not exist in a specification, why care about it?
>
>In theory there could be old clients from 6+ years ago that were
>built to support the 1.0 struct.  But, this seems unlikely
>given how much time has passed.
>
>This is exactly why Ilias doesn't want to put support for the 1.0
>struct in u-boot.  We don't care about 1.0 clients.
>
>>> 
>>>>> 
>>>>> c. If a client passes in a Size that is less than the size up to
>>>>>      and including the vendor ID, the return code is BUFFER_TOO_SMALL
>>>>>      and the Size field is populated with the full size of the struct
>>>>>      supported by the firmware. [This allows a client to determine
>>>>>      whether it is talking to 1.0 or 1.1 firmware]
>>>> 
>>>> Yes, it is the client's task to check the protocol version and not the
>>>> firmware's task to guess what the client has in mind.
>>>> 
>>>> ARM should fix their tests that don't comply with the TCG EFI Protocol
>>>> Specification and then upstream them to edk-test. U-Boot should not try
>>>> to work around incorrect vendor tests.
>>> 
>>> The spec is not clear.  And the committee that owns the spec provided
>>> the clarifications I outlined. They were supposed to provide an errata
>>> update to publish those clarifications, but it seems somehow that
>>> didn't happen.
>>> 
>>> I specifically defined the SCT test spec based on what the committee
>>> told me:
>>> https://github.com/stuyod01/edk2-test/blob/master/uefi-sct/Doc/UEFI-SCT-Case-Spec/30_Protocols_TCG2_Test.md
>>> 
>>> The Arm created tests match what I've been told is the the _intent_ of
>>> the spec.  What is missing is getting TCG to publish errata documenting
>>> that.
>> 
>> As you wrote above the tests don't relate to a known specification.
>
>I'm going to push TCG to publish the errata clarifying this.  Once that
>is published the tests will match the spec.
>
>Thanks,
>Stuart


https://www.trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev9-150513_Public-Review.pdf

is a draft version using ProtocolVersion = 1.3.  I would assume 1.0 relates to an earlier draft not to a published specification.

Best regards

Heinrich