This patch protects against data corruption that could happen in the bus,
by checking that that the digest size returned by the TPM during a PCR read
matches the size of the algorithm passed as argument to tpm2_pcr_read().
This check is performed after information about the PCR banks has been
retrieved.
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
drivers/char/tpm/tpm2-cmd.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index e2d5b84286a7..3b0b5b032901 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -187,15 +187,28 @@ struct tpm2_pcr_read_out {
int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx,
struct tpm_digest *digest_struct, u16 *digest_size_ptr)
{
+ int i;
int rc;
struct tpm_buf buf;
struct tpm2_pcr_read_out *out;
u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0};
u16 digest_size;
+ u16 expected_digest_size = 0;
if (pcr_idx >= TPM2_PLATFORM_PCR)
return -EINVAL;
+ if (!digest_size_ptr) {
+ for (i = 0; i < chip->nr_active_banks &&
+ chip->active_banks[i].alg_id != digest_struct->alg_id; i++)
+ ;
+
+ if (i == chip->nr_active_banks)
+ return -EINVAL;
+
+ expected_digest_size = chip->active_banks[i].digest_size;
+ }
+
rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
if (rc)
return rc;
@@ -215,7 +228,8 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx,
out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
digest_size = be16_to_cpu(out->digest_size);
- if (digest_size > sizeof(digest_struct->digest)) {
+ if (digest_size > sizeof(digest_struct->digest) ||
+ (!digest_size_ptr && digest_size != expected_digest_size)) {
rc = -EINVAL;
goto out;
}
--
2.17.1
