[tpmdd-devel] [PATCH v6 2/2] tpm: enhance TPM 2.0 PCR extend to,support multiple banks

[tpmdd-devel] [PATCH v6 2/2] tpm: enhance TPM 2.0 PCR extend to,support multiple banks

[Ken Goldman]

> The current TPM 2.0 device driver extends only the SHA1 PCR bank
> but the TCG Specification[1] recommends extending all active PCR
> banks, to prevent malicious users from setting unused PCR banks with
> fake measurements and quoting them.
>
> The existing in-kernel interface(tpm_pcr_extend()) expects only a
> SHA1 digest.  To extend all active PCR banks with differing
> digest sizes, the SHA1 digest is padded with trailing 0's as needed.
>
> This patch reuses the defined digest sizes from the crypto subsystem,
> adding a dependency on CRYPTO_HASH_INFO module.
>
> [1] TPM 2.0 Specification referred here is "TCG PC Client Specific
> Platform Firmware Profile for TPM 2.0"

Tested-by: Kenneth Goldman <kgold@linux.vnet.ibm.com>

I obtained an IMA event log from a Power platform, along with the PCR 10 
value from both the SHA-1 and SHA-256 banks of its Nuvoton TPM 2.0.  I 
independently validated that the event log matches the TPM PCR values.

Re: [tpmdd-devel] [PATCH v6 2/2] tpm: enhance TPM 2.0 PCR extend to, support multiple banks

[Nayna]

On 01/26/2017 03:41 AM, Ken Goldman wrote:
>> The current TPM 2.0 device driver extends only the SHA1 PCR bank
>> but the TCG Specification[1] recommends extending all active PCR
>> banks, to prevent malicious users from setting unused PCR banks with
>> fake measurements and quoting them.
>>
>> The existing in-kernel interface(tpm_pcr_extend()) expects only a
>> SHA1 digest.  To extend all active PCR banks with differing
>> digest sizes, the SHA1 digest is padded with trailing 0's as needed.
>>
>> This patch reuses the defined digest sizes from the crypto subsystem,
>> adding a dependency on CRYPTO_HASH_INFO module.
>>
>> [1] TPM 2.0 Specification referred here is "TCG PC Client Specific
>> Platform Firmware Profile for TPM 2.0"
>
> Tested-by: Kenneth Goldman <kgold@linux.vnet.ibm.com>
>
> I obtained an IMA event log from a Power platform, along with the PCR 10
> value from both the SHA-1 and SHA-256 banks of its Nuvoton TPM 2.0.  I
> independently validated that the event log matches the TPM PCR values.

Thank You Ken !!

Thanks & Regards,
    - Nayna

>
>
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