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Thread: Potential errata in Infineon SLB9670 Trusted Platform Module

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    New Member New Member dmgstz is on a distinguished road
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    Apr 2020

    Potential errata in Infineon SLB9670 Trusted Platform Module

    I am using a SLB9670 TPM (Vendor String: 7.40.2098) module to create a duplicate of a key generated in that same TPM, for the sake of clarity:

    - TPM_A: The TPM where I created a key.
    - TPM_A_KEY: The key generated in TPM_A that I want to create a duplicate of.
    - TPM_B: The TPM where I want to import the duplicate.
    - TPM_B_KEY: The ECC P-256 key generated in TPM_B which I want to use to wrap the duplicate create in TPM_A of TPM_A_KEY.

    As part of this process, I need to import the public part of TPM_B_KEY in TPM_A, for which I use the LoadExternal TPM command, which allows me to load the external public part (TPM2B_PUBLIC), the private part is set to the empty buffer, TPM_B_KEY has the attributes DECRYPT and RESTRICTED.

    In the SLB9670 Module I am unable to do this, I receive a 0x101 error (TPM_RC_FAILURE) and the TPM enters into Failure Mode, unable to process any other commands. In the SLM9670 it works OK, same for Microsoft TPM Simulator, I do not receive any other errors. The TPM2B_PUBLIC structure has no errros, it contains the symmetric algo for wrapping, the public components X and Y...

    I am using a HMAC session for the command, but without a session it is also possible to reproduce.

    I have also noticed that I am able to import keys with SIGN as the only attribute, but if I try to load it with a session it enters into Failure Mode.

    I am able to create the duplicate successfully, import it... with the Microsoft TPM Simulator and also with the SLM9670 (Vendor String: 13.11.4555) module, without any changes in the code.

    This all seems quite strange, so I am thinking that perhaps this is an errata or undefined behaviour in the SLB9670 chip, and I was wondering if someone at Infineon would be able to look at this. I can provide TCTI communication traces if required, but I think it should be easy to reproduce, just call LoadExternal with a decrypt/restrict ECC NIST P256 key.

    Many thanks for your help.
    Last edited by dmgstz; Apr 16th, 2020 at 09:03 AM.

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