On Tue, Jan 03, 2017 at 12:15:50AM +0200, Jarkko Sakkinen wrote: > On Fri, Dec 30, 2016 at 02:02:28PM -0500, Nayna Jain wrote: > > IMA extends its hash measurements in the TPM PCRs, based on policy. > > The existing in-kernel TPM extend function extends only the SHA1 > > PCR bank. TPM 2.0 defines multiple PCR banks, to support different > > hash algorithms. The TCG TPM 2.0 Specification[1] recommends > > extending all active PCR banks to prevent malicious users from > > setting unused PCR banks with fake measurements and quoting them. > > This patch set adds support for extending all active PCR banks, > > as recommended. > > > > The first patch implements the TPM 2.0 capability to retrieve > > the list of active PCR banks. > > > > The second patch modifies the tpm_pcr_extend() and tpm2_pcr_extend() > > interface to support extending multiple PCR banks. The existing > > tpm_pcr_extend() interface expects only a SHA1 digest. Hence, to > > extend all active PCR banks with differing digest sizes for TPM 2.0, > > the SHA1 digest is padded with 0's as needed. > > > > This approach is taken to maintain backwards compatibility for IMA > > in order to continue working with both TPM 1.2 and TPM 2.0 without > > any changes and still comply with TCG TPM 2.0 Specification[1]. > > What is the plan to improve IMA so that it can use better hash > algorithms? For me this zero padding sounds like a hack.
I'm fine with zero padding if there is also at minimum to improve the situation. I do not want to apply these patches if they are ought to become a bottlenek. /Jarkko
