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

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Message-ID: <20190928180559.jivt5zlisr43fnva@cantor>
Date:   Sat, 28 Sep 2019 11:05:59 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     linux-integrity@...r.kernel.org, stable@...r.kernel.org,
        David Howells <dhowells@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "open list:ASYMMETRIC KEYS" <keyrings@...r.kernel.org>,
        "open list:CRYPTO API" <linux-crypto@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KEYS: asym_tpm: Switch to get_random_bytes()

On Thu Sep 26 19, Jarkko Sakkinen wrote:
>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
>

Should tpm_unbind and tpm_sign in asym_tpm.c be switched as well then?