tpm2_pcr_read() copies the digest stored in a PCR to a buffer provided by
the caller. However, it does not return the digest size, included in the
output from the TPM. Retrieving it would be useful when a TPM algorithm
is not known by the crypto subsystem, which the TPM driver currently
depends upon.
Most of tpm2_pcr_read() code is moved to the static function
tpm2_pcr_read_common(), which writes the output of the PCR read to the
tpm_buf structure passed as input.
tpm2_pcr_read_common() will be called by tpm2_pcr_read(), and by the new
function tpm2_init_active_bank_info(), which will store the identifier
and the digest size of TPM algorithms in the tpm_chip structure.
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
drivers/char/tpm/tpm2-cmd.c | 34 +++++++++++++++++++++-------------
1 file changed, 21 insertions(+), 13 deletions(-)
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index e1a41b7..0cad0f6 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -218,6 +218,26 @@ struct tpm2_pcr_read_out {
u8 digest[];
} __packed;
+static int tpm2_pcr_read_common(struct tpm_chip *chip, int pcr_idx,
+ enum tpm2_algorithms algo, struct tpm_buf *buf,
+ char *msg)
+{
+ u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0};
+
+ if (pcr_idx >= TPM2_PLATFORM_PCR)
+ return -EINVAL;
+
+ pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
+
+ tpm_buf_append_u32(buf, 1);
+ tpm_buf_append_u16(buf, algo);
+ tpm_buf_append_u8(buf, TPM2_PCR_SELECT_MIN);
+ tpm_buf_append(buf, (const unsigned char *)pcr_select,
+ sizeof(pcr_select));
+
+ return tpm_transmit_cmd(chip, NULL, buf->data, PAGE_SIZE, 0, 0, msg);
+}
+
/**
* tpm2_pcr_read() - read a PCR value
* @chip: TPM chip to use.
@@ -231,24 +251,12 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
int rc;
struct tpm_buf buf;
struct tpm2_pcr_read_out *out;
- u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0};
-
- if (pcr_idx >= TPM2_PLATFORM_PCR)
- return -EINVAL;
rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
if (rc)
return rc;
- pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
-
- tpm_buf_append_u32(&buf, 1);
- tpm_buf_append_u16(&buf, TPM2_ALG_SHA1);
- tpm_buf_append_u8(&buf, TPM2_PCR_SELECT_MIN);
- tpm_buf_append(&buf, (const unsigned char *)pcr_select,
- sizeof(pcr_select));
-
- rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
+ rc = tpm2_pcr_read_common(chip, pcr_idx, TPM2_ALG_SHA1, &buf,
res_buf ? "attempting to read a pcr value" : NULL);
if (rc == 0 && res_buf) {
out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
--
2.9.3
