KEYS: trusted: allow module init if TPM is inactive or deactivated
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 <firstname.lastname@example.org>
Reviewed-by: Tyler Hicks <email@example.com>
Suggested-by: Mimi Zohar <firstname.lastname@example.org>
Reviewed-by: Jarkko Sakkinen <email@example.com>
Signed-off-by: Jarkko Sakkinen <firstname.lastname@example.org>
1 file changed