On Mon, Aug 05, 2019 at 06:44:27PM +0200, Roberto Sassu wrote: > Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a > TPM") allows the trusted module to be loaded even if a TPM is not found, to > avoid module dependency problems. > > However, trusted module initialization can still fail if the TPM is > inactive or deactivated. tpm_get_random() returns an error. > > This patch removes the call to tpm_get_random() and instead extends the PCR > specified by the user with zeros. The security of this alternative is > equivalent to the previous one, as either option prevents with a PCR update > unsealing and misuse of sealed data by a user space process. > > Even if a PCR is extended with zeros, instead of random data, it is still > computationally infeasible to find a value as input for a new PCR extend > operation, to obtain again the PCR value that would allow unsealing. > > Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...") > Signed-off-by: Roberto Sassu <roberto.sa...@huawei.com> > Reviewed-by: Tyler Hicks <tyhi...@canonical.com> > Suggested-by: Mimi Zohar <zo...@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com> /Jarkko