Re: [PATCH v4 1/2] tpm: implement TPM 2.0 capability to get active PCR banks

From: Nayna
Date: Wed Jan 18 2017 - 08:50:57 EST




On 01/18/2017 07:15 PM, Jarkko Sakkinen wrote:
On Wed, Jan 18, 2017 at 03:44:49AM -0500, Nayna Jain wrote:
This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
retrieve the active PCR banks from the TPM. This is needed
to enable extending all active banks as recommended by TPM 2.0
TCG Specification.

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxxxxxxx>
---
drivers/char/tpm/tpm.h | 4 ++++
drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 61 insertions(+)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 1ae9768..dddd573 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
};

enum tpm2_capabilities {
+ TPM2_CAP_PCRS = 5,
TPM2_CAP_TPM_PROPERTIES = 6,
};

@@ -187,6 +188,8 @@ struct tpm_chip {

const struct attribute_group *groups[3];
unsigned int groups_cnt;
+
+ u16 active_banks[7];
#ifdef CONFIG_ACPI
acpi_handle acpi_dev_handle;
char ppi_version[TPM_PPI_VERSION_LEN + 1];
@@ -545,4 +548,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
int tpm2_probe(struct tpm_chip *chip);
+ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
#endif
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 6eda239..75a7546 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -998,3 +998,60 @@ int tpm2_auto_startup(struct tpm_chip *chip)
rc = -ENODEV;
return rc;
}
+
+struct tpm2_pcr_selection {
+ __be16 hash_alg;
+ u8 size_of_select;
+ u8 pcr_select[3];
+} __packed;
+
+/**
+ * tpm2_get_pcr_allocation() - get TPM active PCR banks.
+ *
+ * @chip: TPM chip to use.
+ *
+ * Return: Same as with tpm_transmit_cmd.
+ */
+ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
+{
+ struct tpm2_pcr_selection pcr_selection;
+ struct tpm_buf buf;
+ void *marker;
+ unsigned int count = 0;

You shouldn't initialize 'count'.

It is initialized for reason below:


+ int rc;
+ int i;
+
+ rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+ if (rc)
+ return rc;
+
+ tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
+ tpm_buf_append_u32(&buf, 0);
+ tpm_buf_append_u32(&buf, 1);
+
+ rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
+ "get tpm pcr allocation");
+ if (rc < 0)
+ goto out;

if tpm_transmit_cmd()fails, it jumps to out:
where count is used in if(..).

Thanks & Regards,
- Nayna

+
+ count = be32_to_cpup(
+ (__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
+
+ if (count > ARRAY_SIZE(chip->active_banks))
+ return -ENODEV;
+
+ marker = &buf.data[TPM_HEADER_SIZE + 9];
+ for (i = 0; i < count; i++) {
+ memcpy(&pcr_selection, marker, sizeof(pcr_selection));
+ chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
+ marker = marker + sizeof(struct tpm2_pcr_selection);
+ }
+
+out:
+ if (count < ARRAY_SIZE(chip->active_banks))
+ chip->active_banks[count] = 0;
+
+ tpm_buf_destroy(&buf);
+
+ return rc;
+}
--
2.5.0

Otherwise,

Reviewed-by: Jarkko Sakkinen <jarkko.sakkien@xxxxxxxxxxxxxxx>

/Jarkko