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

Roberto Sassu
2019-02-06T13:07:16Z

On 2/6/2019 1:57 PM, Jarkko Sakkinen wrote:
> 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.

I already applied the patch set on top of linux-tpmdd/next
(41ac27d19b07) and your patch.

Also, there are no conflicts with the current master.

Roberto

> /Jarkko
>

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