linux-kernel - [PATCH v5 3/5] KEYS: trusted: allow trust sources to use kernel RNG for key material

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Message-Id: <20220222195819.2313913-4-a.fatoum@pengutronix.de>
Date:   Tue, 22 Feb 2022 20:58:17 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>
Cc:     kernel@...gutronix.de, Sumit Garg <sumit.garg@...aro.org>,
        David Gstir <david@...ma-star.at>,
        Tim Harvey <tharvey@...eworks.com>,
        Ahmad Fatoum <a.fatoum@...gutronix.de>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Horia Geantă <horia.geanta@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Biggers <ebiggers@...nel.org>,
        Jan Luebbe <j.luebbe@...gutronix.de>,
        Richard Weinberger <richard@....at>,
        Franck LENORMAND <franck.lenormand@....com>,
        Matthias Schiffer <matthias.schiffer@...tq-group.com>,
        Pankaj Gupta <pankaj.gupta@....com>, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org
Subject: [PATCH v5 3/5] KEYS: trusted: allow trust sources to use kernel RNG for key material

The two existing trusted key sources don't make use of the kernel RNG,
but instead let the hardware that does the sealing/unsealing also
generate the random key material. While a previous change offers users
the choice to use the kernel RNG instead for both, new trust sources
may want to unconditionally use the kernel RNG for generating key
material, like it's done elsewhere in the kernel.

This is especially prudent for hardware that has proven-in-production
HWRNG drivers implemented, as otherwise code would have to be duplicated
only to arrive at a possibly worse result.

Make this possible by turning struct trusted_key_ops::get_random
into an optional member. If a driver leaves it NULL, kernel RNG
will be used instead.

Acked-by: Sumit Garg <sumit.garg@...aro.org>
Reviewed-by: David Gstir <david@...ma-star.at>
Tested-By: Tim Harvey <tharvey@...eworks.com>
Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
---
To: James Bottomley <jejb@...ux.ibm.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
To: Mimi Zohar <zohar@...ux.ibm.com>
To: David Howells <dhowells@...hat.com>
Cc: James Morris <jmorris@...ei.org>
Cc: "Serge E. Hallyn" <serge@...lyn.com>
Cc: "Horia Geantă" <horia.geanta@....com>
Cc: Aymen Sghaier <aymen.sghaier@....com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Biggers <ebiggers@...nel.org>
Cc: Jan Luebbe <j.luebbe@...gutronix.de>
Cc: David Gstir <david@...ma-star.at>
Cc: Richard Weinberger <richard@....at>
Cc: Franck LENORMAND <franck.lenormand@....com>
Cc: Sumit Garg <sumit.garg@...aro.org>
Cc: Tim Harvey <tharvey@...eworks.com>
Cc: Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc: Pankaj Gupta <pankaj.gupta@....com>
Cc: keyrings@...r.kernel.org
Cc: linux-crypto@...r.kernel.org
Cc: linux-integrity@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-security-module@...r.kernel.org
---
 include/keys/trusted-type.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index d89fa2579ac0..4eb64548a74f 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -64,7 +64,7 @@ struct trusted_key_ops {
 	/* Unseal a key. */
 	int (*unseal)(struct trusted_key_payload *p, char *datablob);
 
-	/* Get a randomized key. */
+	/* Optional: Get a randomized key. */
 	int (*get_random)(unsigned char *key, size_t key_len);
 
 	/* Exit key interface. */
-- 
2.30.2