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

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Date:   Wed, 25 Jan 2017 17:11:42 -0500
From:   Ken Goldman <kgold@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        tpmdd-devel@...ts.sourceforge.net
Subject: [tpmdd-devel] [PATCH v6 2/2] tpm: enhance TPM 2.0 PCR extend
 to,support multiple banks

> 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@...ux.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.