tpm: enhance TPM 2.0 PCR extend to support multiple banks

naynajain · Jarkko Sakkinen · commit c1f92b4b04ad · 2017-02-03T22:03:14.000+02:00
The current TPM 2.0 device driver extends only the SHA1 PCR bank
but the TCG Specification[1] recommends extending all active PCR
banks, to prevent malicious users from setting unused PCR banks with
fake measurements and quoting them.

The existing in-kernel interface(tpm_pcr_extend()) expects only a
SHA1 digest.  To extend all active PCR banks with differing
digest sizes, the SHA1 digest is padded with trailing 0's as needed.

This patch reuses the defined digest sizes from the crypto subsystem,
adding a dependency on CRYPTO_HASH_INFO module.

[1] TPM 2.0 Specification referred here is "TCG PC Client Specific
Platform Firmware Profile for TPM 2.0"

Signed-off-by: Nayna Jain &lt;nayna@linux.vnet.ibm.com&gt;
Reviewed-by: Jarkko Sakkinen &lt;jarkko.sakkinen@linux.intel.com&gt;
Tested-by: Jarkko Sakkinen &lt;jarkko.sakkinen@linux.intel.com&gt;
Tested-by: Kenneth Goldman &lt;kgold@linux.vnet.ibm.com&gt;
Signed-off-by: Jarkko Sakkinen &lt;jarkko.sakkinen@linux.intel.com&gt;
diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
@@ -6,6 +6,7 @@ menuconfig TCG_TPM
 	tristate "TPM Hardware Support"
 	depends on HAS_IOMEM
 	select SECURITYFS
+	select CRYPTO_HASH_INFO
 	---help---
 	  If you have a TPM security chip in your system, which
 	  implements the Trusted Computing Group's specification,
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
@@ -789,13 +789,25 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
 	struct tpm_cmd_t cmd;
 	int rc;
 	struct tpm_chip *chip;
+	struct tpm2_digest digest_list[ARRAY_SIZE(chip->active_banks)];
+	u32 count = 0;
+	int i;
 
 	chip = tpm_chip_find_get(chip_num);
 	if (chip == NULL)
 		return -ENODEV;
 
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
-		rc = tpm2_pcr_extend(chip, pcr_idx, hash);
+		memset(digest_list, 0, sizeof(digest_list));
+
+		for (i = 0; chip->active_banks[i] != TPM2_ALG_ERROR &&
+		     i < ARRAY_SIZE(chip->active_banks); i++) {
+			digest_list[i].alg_id = chip->active_banks[i];
+			memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
+			count++;
+		}
+
+		rc = tpm2_pcr_extend(chip, pcr_idx, count, digest_list);
 		tpm_put_ops(chip);
 		return rc;
 	}
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
@@ -34,6 +34,7 @@
 #include <linux/acpi.h>
 #include <linux/cdev.h>
 #include <linux/highmem.h>
+#include <crypto/hash_info.h>
 
 #include "tpm_eventlog.h"
 
@@ -380,6 +381,11 @@ struct tpm_cmd_t {
 	tpm_cmd_params	params;
 } __packed;
 
+struct tpm2_digest {
+	u16 alg_id;
+	u8 digest[SHA512_DIGEST_SIZE];
+} __packed;
+
 /* A string buffer type for constructing TPM commands. This is based on the
  * ideas of string buffer code in security/keys/trusted.h but is heap based
  * in order to keep the stack usage minimal.
@@ -529,7 +535,8 @@ static inline inline u32 tpm2_rc_value(u32 rc)
 }
 
 int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
-int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash);
+int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
+		    struct tpm2_digest *digests);
 int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max);
 int tpm2_seal_trusted(struct tpm_chip *chip,
 		      struct trusted_key_payload *payload,
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
@@ -53,22 +53,6 @@ struct tpm2_pcr_read_out {
 	u8	digest[TPM_DIGEST_SIZE];
 } __packed;
 
-struct tpm2_null_auth_area {
-	__be32			handle;
-	__be16			nonce_size;
-	u8			attributes;
-	__be16			auth_size;
-} __packed;
-
-struct tpm2_pcr_extend_in {
-	__be32				pcr_idx;
-	__be32				auth_area_size;
-	struct tpm2_null_auth_area	auth_area;
-	__be32				digest_cnt;
-	__be16				hash_alg;
-	u8				digest[TPM_DIGEST_SIZE];
-} __packed;
-
 struct tpm2_get_tpm_pt_in {
 	__be32	cap_id;
 	__be32	property_id;
@@ -97,7 +81,6 @@ union tpm2_cmd_params {
 	struct	tpm2_self_test_in	selftest_in;
 	struct	tpm2_pcr_read_in	pcrread_in;
 	struct	tpm2_pcr_read_out	pcrread_out;
-	struct	tpm2_pcr_extend_in	pcrextend_in;
 	struct	tpm2_get_tpm_pt_in	get_tpm_pt_in;
 	struct	tpm2_get_tpm_pt_out	get_tpm_pt_out;
 	struct	tpm2_get_random_in	getrandom_in;
@@ -294,49 +277,71 @@ int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
 	return rc;
 }
 
-#define TPM2_GET_PCREXTEND_IN_SIZE \
-	(sizeof(struct tpm_input_header) + \
-	 sizeof(struct tpm2_pcr_extend_in))
-
-static const struct tpm_input_header tpm2_pcrextend_header = {
-	.tag = cpu_to_be16(TPM2_ST_SESSIONS),
-	.length = cpu_to_be32(TPM2_GET_PCREXTEND_IN_SIZE),
-	.ordinal = cpu_to_be32(TPM2_CC_PCR_EXTEND)
-};
+struct tpm2_null_auth_area {
+	__be32  handle;
+	__be16  nonce_size;
+	u8  attributes;
+	__be16  auth_size;
+} __packed;
 
 /**
  * tpm2_pcr_extend() - extend a PCR value
  *
  * @chip:	TPM chip to use.
  * @pcr_idx:	index of the PCR.
- * @hash:	hash value to use for the extend operation.
+ * @count:	number of digests passed.
+ * @digests:	list of pcr banks and corresponding digest values to extend.
  *
  * Return: Same as with tpm_transmit_cmd.
  */
-int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
+int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
+		    struct tpm2_digest *digests)
 {
-	struct tpm2_cmd cmd;
+	struct tpm_buf buf;
+	struct tpm2_null_auth_area auth_area;
 	int rc;
+	int i;
+	int j;
 
-	cmd.header.in = tpm2_pcrextend_header;
-	cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
-	cmd.params.pcrextend_in.auth_area_size =
-		cpu_to_be32(sizeof(struct tpm2_null_auth_area));
-	cmd.params.pcrextend_in.auth_area.handle =
-		cpu_to_be32(TPM2_RS_PW);
-	cmd.params.pcrextend_in.auth_area.nonce_size = 0;
-	cmd.params.pcrextend_in.auth_area.attributes = 0;
-	cmd.params.pcrextend_in.auth_area.auth_size = 0;
-	cmd.params.pcrextend_in.digest_cnt = cpu_to_be32(1);
-	cmd.params.pcrextend_in.hash_alg = cpu_to_be16(TPM2_ALG_SHA1);
-	memcpy(cmd.params.pcrextend_in.digest, hash, TPM_DIGEST_SIZE);
+	if (count > ARRAY_SIZE(chip->active_banks))
+		return -EINVAL;
 
-	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0, 0,
+	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
+	if (rc)
+		return rc;
+
+	tpm_buf_append_u32(&buf, pcr_idx);
+
+	auth_area.handle = cpu_to_be32(TPM2_RS_PW);
+	auth_area.nonce_size = 0;
+	auth_area.attributes = 0;
+	auth_area.auth_size = 0;
+
+	tpm_buf_append_u32(&buf, sizeof(struct tpm2_null_auth_area));
+	tpm_buf_append(&buf, (const unsigned char *)&auth_area,
+		       sizeof(auth_area));
+	tpm_buf_append_u32(&buf, count);
+
+	for (i = 0; i < count; i++) {
+		for (j = 0; j < ARRAY_SIZE(tpm2_hash_map); j++) {
+			if (digests[i].alg_id != tpm2_hash_map[j].tpm_id)
+				continue;
+			tpm_buf_append_u16(&buf, digests[i].alg_id);
+			tpm_buf_append(&buf, (const unsigned char
+					      *)&digests[i].digest,
+			       hash_digest_size[tpm2_hash_map[j].crypto_id]);
+		}
+	}
+
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0, 0,
 			      "attempting extend a PCR value");
 
+	tpm_buf_destroy(&buf);
+
 	return rc;
 }
 
+
 #define TPM2_GETRANDOM_IN_SIZE \
 	(sizeof(struct tpm_input_header) + \
 	 sizeof(struct tpm2_get_random_in))
@@ -1025,6 +1030,8 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 		}
 	}
 
+	rc = tpm2_get_pcr_allocation(chip);
+
 out:
 	if (rc > 0)
 		rc = -ENODEV;
