linux-kernel - [RESEND 2][PATCH] hwrng: add randomness to system from rng sources

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Message-ID: <20131104002030.GA8444@www.outflux.net>
Date:	Sun, 3 Nov 2013 16:20:30 -0800
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	linux-crypto@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Satoru Takeuchi <satoru.takeuchi@...il.com>
Subject: [RESEND 2][PATCH] hwrng: add randomness to system from rng sources

When bringing a new RNG source online, it seems like it would make sense
to use some of its bytes to make the system entropy pool more random,
as done with all sorts of other devices that contain per-device or
per-boot differences.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
Added linux-crypto list to CC.
---
 drivers/char/hw_random/core.c |    7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
index a0f7724852eb..6e5bb68a708c 100644
--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -41,6 +41,7 @@
 #include <linux/miscdevice.h>
 #include <linux/delay.h>
 #include <linux/slab.h>
+#include <linux/random.h>
 #include <asm/uaccess.h>
 
 
@@ -305,6 +306,8 @@ int hwrng_register(struct hwrng *rng)
 	int must_register_misc;
 	int err = -EINVAL;
 	struct hwrng *old_rng, *tmp;
+	unsigned char bytes[16];
+	int bytes_read;
 
 	if (rng->name == NULL ||
 	    (rng->data_read == NULL && rng->read == NULL))
@@ -348,6 +351,10 @@ int hwrng_register(struct hwrng *rng)
 	}
 	INIT_LIST_HEAD(&rng->list);
 	list_add_tail(&rng->list, &rng_list);
+
+	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
+	if (bytes_read > 0)
+		add_device_randomness(bytes, bytes_read);
 out_unlock:
 	mutex_unlock(&rng_mutex);
 out:
-- 
1.7.9.5


-- 
Kees Cook
Chrome OS Security
--
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