Re: [tpmdd-devel] [PATCH v6 1/2] tpm: implement TPM 2.0 capability to get active PCR banks

[Stefan Berger]

On 01/20/2017 12:05 PM, 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 <na...@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
---
  drivers/char/tpm/tpm.h      |  5 ++++
  drivers/char/tpm/tpm2-cmd.c | 59 +++++++++++++++++++++++++++++++++++++++++++++
  2 files changed, 64 insertions(+)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 1ae9768..c291f19 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -97,6 +97,7 @@ enum tpm2_return_codes {
  };

  enum tpm2_algorithms {
+       TPM2_ALG_ERROR          = 0x0000,
        TPM2_ALG_SHA1           = 0x0004,
        TPM2_ALG_KEYEDHASH      = 0x0008,
        TPM2_ALG_SHA256         = 0x000B,
@@ -127,6 +128,7 @@ enum tpm2_permanent_handles {
  };

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

@@ -187,6 +189,8 @@ 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 +549,5 @@ 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..0e000a3 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -998,3 +998,62 @@ 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;
+       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;
+
+       count = be32_to_cpup(
+               (__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
+
+       if (count > ARRAY_SIZE(chip->active_banks)) {
+               rc = -ENODEV;
+               goto out;
+       }
+
+       marker = &buf.data[TPM_HEADER_SIZE + 9];

Now that we are checking access to the returned buffer, we should do an 
additional check here:

end = &buf.data[TPM_HEADER_SIZE + rc];


+       for (i = 0; i < count; i++) {

if (marker + sizeof(pcr_selection) >= end) {
  rc = -EFAULT;
  goto out;
}


+               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))

if (rc < 0 || count < ARRAY_SIZE(...))


I can send a separate patch for this. Let me know.

+               chip->active_banks[count] = TPM2_ALG_ERROR;
+
+       tpm_buf_destroy(&buf);
+
+       return rc;
+}