Re: [PATCH v10 0/6] tpm: retrieve digest size of unknown algorithms from TPM

Jarkko Sakkinen
2019-02-06T12:57:33Z

On Wed, Feb 06, 2019 at 11:57:18AM +0100, Roberto Sassu wrote:
> Update
>
> This version of the patch set includes three additional patches (5-7/7)
> that allow users of the TPM driver to provide a digest for each PCR bank to
> tpm_pcr_extend(). The new patches have been included to facilitate the
> review of all the changes to support TPM 2.0 crypto agility for reading and
> extending PCRs.
>
>
> Original patch set description
>
> The TPM driver currently relies on the crypto subsystem to determine the
> digest size of supported TPM algorithms. In the future, TPM vendors might
> implement new algorithms in their chips, and those algorithms might not
> be supported by the crypto subsystem.
>
> Usually, vendors provide patches for the new hardware, and likely
> the crypto subsystem will be updated before the new algorithm is
> introduced. However, old kernels might be updated later, after patches
> are included in the mainline kernel. This would leave the opportunity
> for attackers to misuse PCRs, as PCR banks with an unknown algorithm
> are not extended.
>
> This patch set provides a long term solution for this issue. If a TPM
> algorithm is not known by the crypto subsystem, the TPM driver retrieves
> the digest size from the TPM with a PCR read. All the PCR banks are
> extended, even if the algorithm is not yet supported by the crypto
> subsystem.
>
> PCR bank information (TPM algorithm ID, digest size, crypto subsystem ID)
> is stored in the tpm_chip structure and available for users of the TPM
> driver.
>
> Changelog
>
> v9:
> - add comment for ima_load_kexec_buffer() in ima_init()
> - move 'digests' and ima_init_digests() to ima_queue.c
> - remove comment for TPM_RETRY
>
> v8:
> - set digest array length in tpm_digest to new constant TPM_MAX_DIGEST_SIZE
> - replace enum tpm_const with #define
> - rename labels in init_trusted()
> - allocate tpm_digest array after retrieving random data in init_digests()
>
> v7:
> - use memchr_inv() in tpm2_get_pcr_allocation()
> - add patch to move tpm_chip to include/linux/tpm.h
> - add patch to set the tpm_chip argument in trusted.c to a pointer from
> tpm_default_chip()
> - remove definition of tpm_extend_digest
> - remove code in tpm2_pcr_extend() to extend unused PCR banks with the
> first digest passed by the caller of tpm_pcr_extend()
> - remove count parameter from tpm_pcr_extend() and tpm2_pcr_extend()
> - remove padding of SHA1 digest in tpm_pcr_extend()
> - pre-allocate and initialize array of tpm_digest structures in
> security/keys/trusted.c and security/integrity/ima/ima_init.c
>
> v6:
> - squash patches 4-6
> - rename tpm_bank_list to tpm_extend_digest, extend_size and extend_data
> members to size and data
> - add comment in tpm2_init_bank_info()
>
> v5:
> - rename digest_struct variable to digest
> - add _head suffix to tcg_efi_specid_event and tcg_pcr_event2
> - rename digest_size member of tpm_bank_list to extend_size
> - change type of alg_id member of tpm_bank_list from u8 to u16
> - add missing semi-colon in pcrlock()
>
> v4:
> - rename active_banks to allocated_banks
> - replace kmalloc_array() with kcalloc()
> - increment nr_allocated_banks if at least one PCR in the bank is selected
> - pass multiple digests to tpm_pcr_extend()
>
> v3:
> - remove end marker change
> - replace active_banks static array with pointer to dynamic array
> - remove TPM2_ACTIVE_PCR_BANKS
>
> v2:
> - change the end marker of the active_banks array
> - check digest size from output of PCR read command
> - remove count parameter from tpm_pcr_read() and tpm2_pcr_read()
>
> v1:
> - modify definition of tpm_pcr_read()
> - move hash algorithms and definition of tpm2_digest to include/linux/tpm.h
>
>
> Roberto Sassu (6):
> tpm: dynamically allocate the allocated_banks array
> tpm: rename and export tpm2_digest and tpm2_algorithms
> tpm: retrieve digest size of unknown algorithms with PCR read
> tpm: move tpm_chip definition to include/linux/tpm.h
> KEYS: trusted: explicitly use tpm_chip structure from
> tpm_default_chip()
> tpm: pass an array of tpm_extend_digest structures to tpm_pcr_extend()
>
> drivers/char/tpm/tpm-chip.c | 1 +
> drivers/char/tpm/tpm-interface.c | 38 ++++----
> drivers/char/tpm/tpm.h | 117 ++---------------------
> drivers/char/tpm/tpm1-cmd.c | 12 +++
> drivers/char/tpm/tpm2-cmd.c | 139 ++++++++++++++++++++--------
> include/linux/tpm.h | 126 ++++++++++++++++++++++++-
> include/linux/tpm_eventlog.h | 9 +-
> security/integrity/ima/ima.h | 1 +
> security/integrity/ima/ima_crypto.c | 10 +-
> security/integrity/ima/ima_init.c | 4 +
> security/integrity/ima/ima_queue.c | 27 +++++-
> security/keys/trusted.c | 73 +++++++++++----
> 12 files changed, 349 insertions(+), 208 deletions(-)
>
> --
> 2.17.1
>

Can you do two things:

1. Check the v3: https://patchwork.kernel.org/patch/10797181/. Needs
to be applied first.
2. Check that this does not cause merge conflicts with the current
imaster? If it does, fix them, and use --subject-prefix="RESEND,PATCH v10".

Thanks.

/Jarkko