tpm: pass an array of tpm_extend_digest structures to tpm_pcr_extend()

Currently, tpm_pcr_extend() accepts as an input only a SHA1 digest.

This patch replaces the hash parameter of tpm_pcr_extend() with an array of
tpm_digest structures, so that the caller can provide a digest for each PCR
bank currently allocated in the TPM.

tpm_pcr_extend() will not extend banks for which no digest was provided,
as it happened before this patch, but instead it requires that callers
provide the full set of digests. Since the number of digests will always be
chip->nr_allocated_banks, the count parameter has been removed.

Due to the API change, ima_pcr_extend() and pcrlock() have been modified.
Since the number of allocated banks is not known in advance, the memory for
the digests must be dynamically allocated. To avoid performance degradation
and to avoid that a PCR extend is not done due to lack of memory, the array
of tpm_digest structures is allocated by the users of the TPM driver at
initialization time.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Mimi Zohar <zohar@linux.ibm.com> (on x86 for TPM 1.2 & PTT TPM 2.0)
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 33 insertions, 8 deletions

diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 5b852263eae1..bcc9c6ead7fd 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -35,6 +35,7 @@
 static const char hmac_alg[] = "hmac(sha1)";
 static const char hash_alg[] = "sha1";
 static struct tpm_chip *chip;
+static struct tpm_digest *digests;
 
 struct sdesc {
 	struct shash_desc shash;
@@ -380,15 +381,10 @@ EXPORT_SYMBOL_GPL(trusted_tpm_send);
  */
 static int pcrlock(const int pcrnum)
 {
-	unsigned char hash[SHA1_DIGEST_SIZE];
-	int ret;
-
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
-	ret = tpm_get_random(chip, hash, SHA1_DIGEST_SIZE);
-	if (ret != SHA1_DIGEST_SIZE)
-		return ret;
-	return tpm_pcr_extend(chip, pcrnum, hash) ? -EINVAL : 0;
+
+	return tpm_pcr_extend(chip, pcrnum, digests) ? -EINVAL : 0;
 }
 
 /*
@@ -1222,6 +1218,29 @@ hashalg_fail:
 	return ret;
 }
 
+static int __init init_digests(void)
+{
+	u8 digest[TPM_MAX_DIGEST_SIZE];
+	int ret;
+	int i;
+
+	ret = tpm_get_random(chip, digest, TPM_MAX_DIGEST_SIZE);
+	if (ret < 0)
+		return ret;
+	if (ret < TPM_MAX_DIGEST_SIZE)
+		return -EFAULT;
+
+	digests = kcalloc(chip->nr_allocated_banks, sizeof(*digests),
+			  GFP_KERNEL);
+	if (!digests)
+		return -ENOMEM;
+
+	for (i = 0; i < chip->nr_allocated_banks; i++)
+		memcpy(digests[i].digest, digest, TPM_MAX_DIGEST_SIZE);
+
+	return 0;
+}
+
 static int __init init_trusted(void)
 {
 	int ret;
@@ -1229,15 +1248,20 @@ static int __init init_trusted(void)
 	chip = tpm_default_chip();
 	if (!chip)
 		return -ENOENT;
-	ret = trusted_shash_alloc();
+	ret = init_digests();
 	if (ret < 0)
 		goto err_put;
+	ret = trusted_shash_alloc();
+	if (ret < 0)
+		goto err_free;
 	ret = register_key_type(&key_type_trusted);
 	if (ret < 0)
 		goto err_release;
 	return 0;
 err_release:
 	trusted_shash_release();
+err_free:
+	kfree(digests);
 err_put:
 	put_device(&chip->dev);
 	return ret;
@@ -1246,6 +1270,7 @@ err_put:
 static void __exit cleanup_trusted(void)
 {
 	put_device(&chip->dev);
+	kfree(digests);
 	trusted_shash_release();
 	unregister_key_type(&key_type_trusted);
 }