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authorPeter Maydell <peter.maydell@linaro.org>2017-02-28 12:08:14 +0000
committerPeter Maydell <peter.maydell@linaro.org>2017-02-28 12:08:14 +0000
commit373442ea3a96249991cfad3fc0e83fca5f8558d5 (patch)
tree14ef069f018f5274a8c985238d16f98b15e11c93 /hw/misc/bcm2835_rng.c
parent54a5ba13a9ffe7d25fc649b0fa9f8314734c8ccc (diff)
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bcm2835_rng: Use qcrypto_random_bytes() rather than rand()
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 <peter.maydell@linaro.org> Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Diffstat (limited to 'hw/misc/bcm2835_rng.c')
-rw-r--r--hw/misc/bcm2835_rng.c27
1 files changed, 26 insertions, 1 deletions
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: