• Roberto Sassu's avatar
    tpm: retrieve digest size of unknown algorithms with PCR read · 879b5892
    Roberto Sassu authored
    Currently, the TPM driver retrieves the digest size from a table mapping
    TPM algorithms identifiers to identifiers defined by the crypto subsystem.
    If the algorithm is not defined by the latter, the digest size can be
    retrieved from the output of the PCR read command.
    
    The patch modifies the definition of tpm_pcr_read() and tpm2_pcr_read() to
    pass the desired hash algorithm and obtain the digest size at TPM startup.
    Algorithms and corresponding digest sizes are stored in the new structure
    tpm_bank_info, member of tpm_chip, so that the information can be used by
    other kernel subsystems.
    
    tpm_bank_info contains: the TPM algorithm identifier, necessary to generate
    the event log as defined by Trusted Computing Group (TCG); the digest size,
    to pad/truncate a digest calculated with a different algorithm; the crypto
    subsystem identifier, to calculate the digest of event data.
    
    This patch also protects against data corruption that could happen in the
    bus, by checking that the digest size returned by the TPM during a PCR read
    matches the size of the algorithm passed to tpm2_pcr_read().
    
    For the initial PCR read, when digest sizes are not yet available, this
    patch ensures that the amount of data copied from the output returned by
    the TPM does not exceed the size of the array data are copied to.
    Signed-off-by: default avatarRoberto Sassu <roberto.sassu@huawei.com>
    Reviewed-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Tested-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    Acked-by: default avatarMimi Zohar <zohar@linux.ibm.com>
    Signed-off-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
    879b5892
tpm2-cmd.c 25.2 KB