linux-kernel - [PATCH] KEYS: asym_tpm: Switch to get_random

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Message-Id: <20190926171601.30404-1-jarkko.sakkinen@linux.intel.com>
Date:   Thu, 26 Sep 2019 20:16:01 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     linux-integrity@...r.kernel.org
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        stable@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        keyrings@...r.kernel.org (open list:ASYMMETRIC KEYS),
        linux-crypto@...r.kernel.org (open list:CRYPTO API),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] KEYS: asym_tpm: Switch to get_random_bytes()

Only the kernel random pool should be used for generating random numbers.
TPM contributes to that pool among the other sources of entropy. In here it
is not, agreed, absolutely critical because TPM is what is trusted anyway
but in order to remove tpm_get_random() we need to first remove all the
call sites.

Cc: stable@...r.kernel.org
Fixes: 0c36264aa1d5 ("KEYS: asym_tpm: Add loadkey2 and flushspecific [ver #2]")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
---
 crypto/asymmetric_keys/asym_tpm.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/crypto/asymmetric_keys/asym_tpm.c b/crypto/asymmetric_keys/asym_tpm.c
index 76d2ce3a1b5b..c14b8d186e93 100644
--- a/crypto/asymmetric_keys/asym_tpm.c
+++ b/crypto/asymmetric_keys/asym_tpm.c
@@ -6,6 +6,7 @@
 #include <linux/kernel.h>
 #include <linux/seq_file.h>
 #include <linux/scatterlist.h>
+#include <linux/random.h>
 #include <linux/tpm.h>
 #include <linux/tpm_command.h>
 #include <crypto/akcipher.h>
@@ -54,11 +55,7 @@ static int tpm_loadkey2(struct tpm_buf *tb,
 	}
 
 	/* generate odd nonce */
-	ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
-	if (ret < 0) {
-		pr_info("tpm_get_random failed (%d)\n", ret);
-		return ret;
-	}
+	get_random_bytes(nonceodd, TPM_NONCE_SIZE);
 
 	/* calculate authorization HMAC value */
 	ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
-- 
2.20.1