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
