Re: [PATCH v2, RESEND 2/3] tpm: modify tpm_pcr_read() definition to pass TPM hash algorithms

Roberto Sassu <roberto.sassu@xxxxxxxxxx> · Fri, 21 Sep 2018 12:24:15 +0200

On 9/17/2018 11:38 AM, Roberto Sassu wrote:
Currently the TPM driver allows other kernel subsystems to read only the
SHA1 PCR bank. This patch modifies the parameters of tpm_pcr_read() and
tpm2_pcr_read() to pass an array of tpm_digest structures, which contains
the desired hash algorithms. Initially, the array size is limited to 1.

Jarkko, is this patch ok?

Mimi, I wait for your review of the IMA part.

Roberto


Due to the API change, IMA functions have been modified.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
  drivers/char/tpm/tpm-interface.c    | 13 +++++++++----
  drivers/char/tpm/tpm.h              |  3 ++-
  drivers/char/tpm/tpm2-cmd.c         | 17 +++++++++++------
  include/linux/tpm.h                 |  6 ++++--
  security/integrity/ima/ima_crypto.c | 10 +++++-----
  5 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 645c9aa7677a..81872880b5f1 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -976,21 +976,26 @@ EXPORT_SYMBOL_GPL(tpm_is_tpm2);
   * tpm_pcr_read - read a PCR value from SHA1 bank
   * @chip:	a &struct tpm_chip instance, %NULL for the default chip
   * @pcr_idx:	the PCR to be retrieved
- * @res_buf:	the value of the PCR
+ * @count:	number of digests passed
+ * @digests:	list of pcr banks and buffers current PCR values are written to
   *
   * Return: same as with tpm_transmit_cmd()
   */
-int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
+int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
+		 struct tpm_digest *digests)
  {
  	int rc;
  
+	if (count != 1)
+		return -EINVAL;
+
  	chip = tpm_find_get_ops(chip);
  	if (!chip)
  		return -ENODEV;
  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		rc = tpm2_pcr_read(chip, pcr_idx, res_buf);
+		rc = tpm2_pcr_read(chip, pcr_idx, count, digests);
  	else
-		rc = tpm_pcr_read_dev(chip, pcr_idx, res_buf);
+		rc = tpm_pcr_read_dev(chip, pcr_idx, digests[0].digest);
  	tpm_put_ops(chip);
  	return rc;
  }
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index b928ba44d864..9479e1ae1b4c 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -564,7 +564,8 @@ static inline u32 tpm2_rc_value(u32 rc)
  	return (rc & BIT(7)) ? rc & 0xff : rc;
  }
  
-int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
+int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
+		  struct tpm_digest *digests);
  int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
  		    struct tpm_digest *digests);
  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 2d7397b8a0d1..601d67c76c1e 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -179,11 +179,13 @@ struct tpm2_pcr_read_out {
   * tpm2_pcr_read() - read a PCR value
   * @chip:	TPM chip to use.
   * @pcr_idx:	index of the PCR to read.
- * @res_buf:	buffer to store the resulting hash.
+ * @count:	number of digests passed.
+ * @digests:	list of pcr banks and buffers current PCR values are written to.
   *
   * Return: Same as with tpm_transmit_cmd.
   */
-int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
+int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
+		  struct tpm_digest *digests)
  {
  	int rc;
  	struct tpm_buf buf;
@@ -192,6 +194,8 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
  
  	if (pcr_idx >= TPM2_PLATFORM_PCR)
  		return -EINVAL;
+	if (count > 1)
+		return -EINVAL;
  
  	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
  	if (rc)
@@ -200,16 +204,17 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
  	pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
  
  	tpm_buf_append_u32(&buf, 1);
-	tpm_buf_append_u16(&buf, TPM_ALG_SHA1);
+	tpm_buf_append_u16(&buf, count ? digests[0].alg_id : TPM_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,
-			res_buf ? "attempting to read a pcr value" : NULL);
-	if (rc == 0 && res_buf) {
+			      count ? "attempting to read a pcr value" : NULL);
+	if (rc == 0 && count) {
  		out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
-		memcpy(res_buf, out->digest, SHA1_DIGEST_SIZE);
+		memcpy(digests[0].digest, out->digest,
+		       be16_to_cpu(out->digest_size));
  	}
  
  	tpm_buf_destroy(&buf);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 71d7bbf5f690..ac9fc47f4494 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -71,7 +71,8 @@ struct tpm_class_ops {
  #if defined(CONFIG_TCG_TPM) || defined(CONFIG_TCG_TPM_MODULE)
  
  extern int tpm_is_tpm2(struct tpm_chip *chip);
-extern int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
+extern int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
+			struct tpm_digest *digests);
  extern int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash);
  extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen);
  extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t max);
@@ -87,7 +88,8 @@ static inline int tpm_is_tpm2(struct tpm_chip *chip)
  {
  	return -ENODEV;
  }
-static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
+static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, u32 count,
+			       struct tpm_digest *digests)
  {
  	return -ENODEV;
  }
diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index 7e7e7e7c250a..4c94cf810d15 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -629,12 +629,12 @@ int ima_calc_buffer_hash(const void *buf, loff_t len,
  	return calc_buffer_shash(buf, len, hash);
  }
  
-static void __init ima_pcrread(int idx, u8 *pcr)
+static void __init ima_pcrread(int idx, struct tpm_digest *d)
  {
  	if (!ima_tpm_chip)
  		return;
  
-	if (tpm_pcr_read(ima_tpm_chip, idx, pcr) != 0)
+	if (tpm_pcr_read(ima_tpm_chip, idx, 1, d) != 0)
  		pr_err("Error Communicating to TPM chip\n");
  }
  
@@ -644,7 +644,7 @@ static void __init ima_pcrread(int idx, u8 *pcr)
  static int __init ima_calc_boot_aggregate_tfm(char *digest,
  					      struct crypto_shash *tfm)
  {
-	u8 pcr_i[TPM_DIGEST_SIZE];
+	struct tpm_digest d = {.alg_id = TPM_ALG_SHA1};
  	int rc, i;
  	SHASH_DESC_ON_STACK(shash, tfm);
  
@@ -657,9 +657,9 @@ static int __init ima_calc_boot_aggregate_tfm(char *digest,
  
  	/* cumulative sha1 over tpm registers 0-7 */
  	for (i = TPM_PCR0; i < TPM_PCR8; i++) {
-		ima_pcrread(i, pcr_i);
+		ima_pcrread(i, &d);
  		/* now accumulate with current aggregate */
-		rc = crypto_shash_update(shash, pcr_i, TPM_DIGEST_SIZE);
+		rc = crypto_shash_update(shash, d.digest, TPM_DIGEST_SIZE);
  	}
  	if (!rc)
  		crypto_shash_final(shash, digest);







