[PATCH 1/4] tpm: check whether all digests have been provided for TPM 2.0 extend

[Roberto Sassu <roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>]

TCG mandates that all PCR banks must be extended during the same operation.
tpm2_pcr_extend() will check whether all digests have been provided.

The check is necessary because tpm2_pcr_extend() will be called by a new
function, allowing callers to provide a digest for each PCR bank.

Signed-off-by: Roberto Sassu <roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
 drivers/char/tpm/tpm2-cmd.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 881aea9..f4d534c 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -284,6 +284,26 @@ struct tpm2_null_auth_area {
 	__be16  auth_size;
 } __packed;
 
+static bool tpm2_digests_all_banks(struct tpm_chip *chip, u32 count,
+				   struct tpm2_digest *digests)
+{
+	int i, j;
+
+	for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
+	     chip->active_banks[i] != TPM2_ALG_ERROR; i++) {
+		for (j = 0; j < count; j++)
+			if (digests[j].alg_id == chip->active_banks[i])
+				break;
+		if (j == count) {
+			pr_err("missing TPM algorithm 0x%x\n",
+			       chip->active_banks[i]);
+			return false;
+		}
+	}
+
+	return true;
+}
+
 /**
  * tpm2_pcr_extend() - extend a PCR value
  *
@@ -306,6 +326,9 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
 	if (count > ARRAY_SIZE(chip->active_banks))
 		return -EINVAL;
 
+	if (!tpm2_digests_all_banks(chip, count, digests))
+		return -EINVAL;
+
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
 	if (rc)
 		return rc;
-- 
2.9.3


------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot