On Fri, Nov 11, 2022 at 03:16:26PM -0800, Evan Green wrote: > Add an internal command for resetting a PCR. This will be used by the > encrypted hibernation code to set PCR23 to a known value. The > hibernation code will seal the hibernation key with a policy specifying > PCR23 be set to this known value as a mechanism to ensure that the > hibernation key is genuine. But to do this repeatedly, resetting the PCR > is necessary as well. > > Link: https://lore.kernel.org/lkml/20210220013255.1083202-2-matthewgarrett@xxxxxxxxxx/ > Co-developed-by: Matthew Garrett <mjg59@xxxxxxxxxx> > Signed-off-by: Matthew Garrett <mjg59@xxxxxxxxxx> > Signed-off-by: Evan Green <evgreen@xxxxxxxxxxxx> > > --- > > Changes in v5: > - Change to co-developed by Matthew (Kees) > > Changes in v4: > - Open code tpm2_pcr_reset implementation in tpm-interface.c (Jarkko) > - Rename interface symbol to tpm2_pcr_reset, fix kerneldocs (Jarkko) > > Changes in v3: > - Unify tpm1/2_pcr_reset prototypes (Jarkko) > - Wait no, remove the TPM1 stuff altogether (Jarkko) > - Remove extra From tag and blank in commit msg (Jarkko). > > drivers/char/tpm/tpm-interface.c | 47 ++++++++++++++++++++++++++++++++ > drivers/char/tpm/tpm2-cmd.c | 7 ----- > include/linux/tpm.h | 14 ++++++++++ > 3 files changed, 61 insertions(+), 7 deletions(-) > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c > index 1621ce8187052c..886277b2654e3b 100644 > --- a/drivers/char/tpm/tpm-interface.c > +++ b/drivers/char/tpm/tpm-interface.c > @@ -342,6 +342,53 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, > } > EXPORT_SYMBOL_GPL(tpm_pcr_extend); > > +/** > + * tpm2_pcr_reset - Reset the specified PCR > + * @chip: A &struct tpm_chip instance, %NULL for the default chip > + * @pcr_idx: The PCR to be reset > + * > + * Return: Same as with tpm_transmit_cmd(), or ENOTTY for TPM1 devices. > + */ > +int tpm2_pcr_reset(struct tpm_chip *chip, u32 pcr_idx) > +{ > + struct tpm2_null_auth_area auth_area; > + struct tpm_buf buf; > + int rc; > + > + chip = tpm_find_get_ops(chip); > + if (!chip) > + return -ENODEV; > + > + if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) { > + rc = -ENOTTY; > + goto out; > + } > + > + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_RESET); > + if (rc) > + goto out; > + > + tpm_buf_append_u32(&buf, pcr_idx); > + > + auth_area.handle = cpu_to_be32(TPM2_RS_PW); > + auth_area.nonce_size = 0; > + auth_area.attributes = 0; > + auth_area.auth_size = 0; > + > + tpm_buf_append_u32(&buf, sizeof(struct tpm2_null_auth_area)); > + tpm_buf_append(&buf, (const unsigned char *)&auth_area, > + sizeof(auth_area)); > + > + rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to reset a PCR"); > + > + tpm_buf_destroy(&buf); > + > +out: > + tpm_put_ops(chip); > + return rc; > +} > +EXPORT_SYMBOL_GPL(tpm2_pcr_reset); > + > /** > * tpm_send - send a TPM command > * @chip: a &struct tpm_chip instance, %NULL for the default chip > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c > index 65d03867e114c5..303ce2ea02a4b0 100644 > --- a/drivers/char/tpm/tpm2-cmd.c > +++ b/drivers/char/tpm/tpm2-cmd.c > @@ -216,13 +216,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx, > return rc; > } > > -struct tpm2_null_auth_area { > - __be32 handle; > - __be16 nonce_size; > - u8 attributes; > - __be16 auth_size; > -} __packed; > - > /** > * tpm2_pcr_extend() - extend a PCR value > * > diff --git a/include/linux/tpm.h b/include/linux/tpm.h > index dfeb25a0362dee..70134e6551745f 100644 > --- a/include/linux/tpm.h > +++ b/include/linux/tpm.h > @@ -219,6 +219,7 @@ enum tpm2_command_codes { > TPM2_CC_HIERARCHY_CONTROL = 0x0121, > TPM2_CC_HIERARCHY_CHANGE_AUTH = 0x0129, > TPM2_CC_CREATE_PRIMARY = 0x0131, > + TPM2_CC_PCR_RESET = 0x013D, > TPM2_CC_SEQUENCE_COMPLETE = 0x013E, > TPM2_CC_SELF_TEST = 0x0143, > TPM2_CC_STARTUP = 0x0144, > @@ -293,6 +294,13 @@ struct tpm_header { > }; > } __packed; > > +struct tpm2_null_auth_area { > + __be32 handle; > + __be16 nonce_size; > + u8 attributes; > + __be16 auth_size; > +} __packed; > + > /* A string buffer type for constructing TPM commands. This is based on the > * ideas of string buffer code in security/keys/trusted.h but is heap based > * in order to keep the stack usage minimal. > @@ -423,6 +431,7 @@ extern ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf *buf, > size_t min_rsp_body_length, const char *desc); > extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx, > struct tpm_digest *digest); > +extern int tpm2_pcr_reset(struct tpm_chip *chip, u32 pcr_idx); > extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, > struct tpm_digest *digests); > extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen); > @@ -440,6 +449,11 @@ static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, > return -ENODEV; > } > > +static inline int tpm2_pcr_reset(struct tpm_chip *chip, int pcr_idx) > +{ > + return -ENODEV; > +} > + > static inline int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, > struct tpm_digest *digests) > { > -- > 2.38.1.431.g37b22c650d-goog > Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> BR, Jarkko
