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

Jarkko Sakkinen
2019-02-06T13:54:58Z

On Wed, Feb 06, 2019 at 02:07:04PM +0100, Roberto Sassu wrote:
> 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

Before getting your new version, I applied:

https://patchwork.kernel.org/project/linux-integrity/list/?series=76223

This causes some merge conflicts:

error: Failed to merge in the changes.
Patch failed at 0003 tpm: retrieve digest size of unknown algorithms with PCR read

/Jarkko