From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52241) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ciPfk-0002Rb-GT for qemu-devel@nongnu.org; Mon, 27 Feb 2017 13:05:23 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ciPfh-0001xI-Ho for qemu-devel@nongnu.org; Mon, 27 Feb 2017 13:05:20 -0500 Received: from orth.archaic.org.uk ([2001:8b0:1d0::2]:48677) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1ciPfh-0001lG-6m for qemu-devel@nongnu.org; Mon, 27 Feb 2017 13:05:17 -0500 Received: from pm215 by orth.archaic.org.uk with local (Exim 4.84_2) (envelope-from ) id 1ciPfR-0002If-DA for qemu-devel@nongnu.org; Mon, 27 Feb 2017 18:05:01 +0000 From: Peter Maydell Date: Mon, 27 Feb 2017 18:04:31 +0000 Message-Id: <1488218699-31035-3-git-send-email-peter.maydell@linaro.org> In-Reply-To: <1488218699-31035-1-git-send-email-peter.maydell@linaro.org> References: <1488218699-31035-1-git-send-email-peter.maydell@linaro.org> Subject: [Qemu-devel] [PULL 02/30] bcm2835_rng: Use qcrypto_random_bytes() rather than rand() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Switch to using qcrypto_random_bytes() rather than rand() as our source of randomness for the BCM2835 RNG. If qcrypto_random_bytes() fails, we don't want to return the guest a non-random value in case they're really using it for cryptographic purposes, so the best we can do is a fatal error. This shouldn't happen unless something's broken, though. In theory we could implement this device's full FIFO and interrupt semantics and then just stop filling the FIFO. That's a lot of work, though, and doesn't really give a very nice diagnostic to the user since the guest will just seem to hang. Signed-off-by: Peter Maydell Reviewed-by: Daniel P. Berrange --- hw/misc/bcm2835_rng.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) diff --git a/hw/misc/bcm2835_rng.c b/hw/misc/bcm2835_rng.c index 2242bc5..4d62143 100644 --- a/hw/misc/bcm2835_rng.c +++ b/hw/misc/bcm2835_rng.c @@ -9,8 +9,33 @@ #include "qemu/osdep.h" #include "qemu/log.h" +#include "qapi/error.h" +#include "crypto/random.h" #include "hw/misc/bcm2835_rng.h" +static uint32_t get_random_bytes(void) +{ + uint32_t res; + Error *err = NULL; + + if (qcrypto_random_bytes((uint8_t *)&res, sizeof(res), &err) < 0) { + /* On failure we don't want to return the guest a non-random + * value in case they're really using it for cryptographic + * purposes, so the best we can do is die here. + * This shouldn't happen unless something's broken. + * In theory we could implement this device's full FIFO + * and interrupt semantics and then just stop filling the + * FIFO. That's a lot of work, though, so we assume any + * errors are systematic problems and trust that if we didn't + * fail as the guest inited then we won't fail later on + * mid-run. + */ + error_report_err(err); + exit(1); + } + return res; +} + static uint64_t bcm2835_rng_read(void *opaque, hwaddr offset, unsigned size) { @@ -27,7 +52,7 @@ static uint64_t bcm2835_rng_read(void *opaque, hwaddr offset, res = s->rng_status | (1 << 24); break; case 0x8: /* rng_data */ - res = rand(); + res = get_random_bytes(); break; default: -- 2.7.4