Re: [edk2-devel] TPM2 NVM WRITE IN EDK2

["Laszlo Ersek" <lersek@redhat.com>]

On 11/9/23 11:39, Hamit Can Karaca wrote:
> Hello,
> I am a young UEFI developer and I am trying to use the functions in
> Tpm2CommandLib to write data to TPM2. I have defined the index that, I
> am going to write data to, using the DefineSpace function. But whenever
> I am trying to use the Tpm2NvWrite function, I keep getting
> EFI_DEVICE_ERROR with a response code 0x1D5. Is there anything to do
> before Tpm2NvWrite that I don't know or do I use the wrong parameters?
> If anyone has used these functions please let me know, thanks!

I think this should be possible to explain from the TPM2 spec, part 2,
"structures".

Response code 0x1D5 is binary 111010101. Bit 7 is set, therefore we have
to look at the format-1 RC structure:

  0001 1 1 010101
  ---- - - ------
     N F P      E

N=1 (1-based parameter that the error refers to)
F=1 (format-1 response)
P=1 (error is associated with a parameter)
E=0x15 (error number)

In Table 16, RC_FMT1 (value 0x80 -- F bit, or bit 7) says "This bit is
SET in all format 1 response codes. The codes in this group may have a
value added to them to indicate the handle, session, or parameter
to which they apply". Indeed, we have P=1 (error is associated with
parameter) and N=1 (1-based parameter number related to the error is 1).

Thus, we have TPM_RC_SIZE (= RC_FMT1 + 0x015, 0x95, to which we add P=1
(0x40) and N=1 (0x100) for getting 0x1D5):

TPM_RC_SIZE: structure is the wrong size

In other words, whatever command you are sending, the TPM seems to reply
with "parameter 1 of your command is incorrectly sized".

Laszlo



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