diff options
| author | Peter Maydell <peter.maydell@linaro.org> | 2017-02-28 12:08:14 +0000 |
|---|---|---|
| committer | Peter Maydell <peter.maydell@linaro.org> | 2017-02-28 12:08:14 +0000 |
| commit | 373442ea3a96249991cfad3fc0e83fca5f8558d5 (patch) | |
| tree | 14ef069f018f5274a8c985238d16f98b15e11c93 | |
| parent | 54a5ba13a9ffe7d25fc649b0fa9f8314734c8ccc (diff) | |
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>
| -rw-r--r-- | hw/misc/bcm2835_rng.c | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/hw/misc/bcm2835_rng.c b/hw/misc/bcm2835_rng.c index 2242bc5eb5..4d62143b24 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: |