@@ -296,29 +296,40 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
int total = 0;
int retries = 5;
u8 *dest_ptr = dest;
+ struct tpm2_auth *auth;
if (!num_bytes || max > TPM_MAX_RNG_DATA)
return -EINVAL;
- err = tpm_buf_init(&buf, 0, 0);
+ err = tpm2_start_auth_session(chip, &auth);
if (err)
return err;
+ err = tpm_buf_init(&buf, 0, 0);
+ if (err) {
+ tpm2_end_auth_session(auth);
+ return err;
+ }
+
do {
- tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
+ tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
+ tpm_buf_append_hmac_session_opt(&buf, auth, TPM2_SA_ENCRYPT
+ | TPM2_SA_CONTINUE_SESSION,
+ NULL, 0);
tpm_buf_append_u16(&buf, num_bytes);
+ tpm_buf_fill_hmac_session(&buf, auth);
err = tpm_transmit_cmd(chip, &buf,
offsetof(struct tpm2_get_random_out,
buffer),
"attempting get random");
+ err = tpm_buf_check_hmac_response(&buf, auth, err);
if (err) {
if (err > 0)
err = -EIO;
goto out;
}
- out = (struct tpm2_get_random_out *)
- &buf.data[TPM_HEADER_SIZE];
+ out = (struct tpm2_get_random_out *)tpm_buf_parameters(&buf);
recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
if (tpm_buf_length(&buf) <
TPM_HEADER_SIZE +
@@ -335,6 +346,8 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
} while (retries-- && total < max);
tpm_buf_destroy(&buf);
+ tpm2_end_auth_session(auth);
+
return total ? total : -EIO;
out:
tpm_buf_destroy(&buf);
If some entity is snooping the TPM bus, they can see the random numbers we're extracting from the TPM and do prediction attacks against their consumers. Foil this attack by using response encryption to prevent the attacker from seeing the random sequence. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> --- v3: add error handling to sessions and redo to be outside loop --- drivers/char/tpm/tpm2-cmd.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-)