diff options
| -rw-r--r-- | include/qemu/guest-random.h | 68 | ||||
| -rw-r--r-- | util/Makefile.objs | 1 | ||||
| -rw-r--r-- | util/guest-random.c | 93 |
3 files changed, 162 insertions, 0 deletions
diff --git a/include/qemu/guest-random.h b/include/qemu/guest-random.h new file mode 100644 index 0000000000..09ff9c2236 --- /dev/null +++ b/include/qemu/guest-random.h @@ -0,0 +1,68 @@ +/* + * QEMU guest-visible random functions + * + * Copyright 2019 Linaro, Ltd. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the Free + * Software Foundation; either version 2 of the License, or (at your option) + * any later version. + */ + +#ifndef QEMU_GUEST_RANDOM_H +#define QEMU_GUEST_RANDOM_H + +/** + * qemu_guest_random_seed_main(const char *optarg, Error **errp) + * @optarg: a non-NULL pointer to a C string + * @errp: an error indicator + * + * The @optarg value is that which accompanies the -seed argument. + * This forces qemu_guest_getrandom into deterministic mode. + * + * Returns 0 on success, < 0 on failure while setting *errp. + */ +int qemu_guest_random_seed_main(const char *optarg, Error **errp); + +/** + * qemu_guest_random_seed_thread_part1(void) + * + * If qemu_getrandom is in deterministic mode, returns an + * independent seed for the new thread. Otherwise returns 0. + */ +uint64_t qemu_guest_random_seed_thread_part1(void); + +/** + * qemu_guest_random_seed_thread_part2(uint64_t seed) + * @seed: a value for the new thread. + * + * If qemu_guest_getrandom is in deterministic mode, this stores an + * independent seed for the new thread. Otherwise a no-op. + */ +void qemu_guest_random_seed_thread_part2(uint64_t seed); + +/** + * qemu_guest_getrandom(void *buf, size_t len, Error **errp) + * @buf: a buffer of bytes to be written + * @len: the number of bytes in @buf + * @errp: an error indicator + * + * Fills len bytes in buf with random data. This should only be used + * for data presented to the guest. Host-side crypto services should + * use qcrypto_random_bytes. + * + * Returns 0 on success, < 0 on failure while setting *errp. + */ +int qemu_guest_getrandom(void *buf, size_t len, Error **errp); + +/** + * qemu_guest_getrandom_nofail(void *buf, size_t len) + * @buf: a buffer of bytes to be written + * @len: the number of bytes in @buf + * + * Like qemu_guest_getrandom, but will assert for failure. + * Use this when there is no reasonable recovery. + */ +void qemu_guest_getrandom_nofail(void *buf, size_t len); + +#endif /* QEMU_GUEST_RANDOM_H */ diff --git a/util/Makefile.objs b/util/Makefile.objs index 9206878dec..c27a923dbe 100644 --- a/util/Makefile.objs +++ b/util/Makefile.objs @@ -54,5 +54,6 @@ util-obj-y += iova-tree.o util-obj-$(CONFIG_INOTIFY1) += filemonitor-inotify.o util-obj-$(CONFIG_LINUX) += vfio-helpers.o util-obj-$(CONFIG_OPENGL) += drm.o +util-obj-y += guest-random.o stub-obj-y += filemonitor-stub.o diff --git a/util/guest-random.c b/util/guest-random.c new file mode 100644 index 0000000000..e8124a3cad --- /dev/null +++ b/util/guest-random.c @@ -0,0 +1,93 @@ +/* + * QEMU guest-visible random functions + * + * Copyright 2019 Linaro, Ltd. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the Free + * Software Foundation; either version 2 of the License, or (at your option) + * any later version. + */ + +#include "qemu/osdep.h" +#include "qemu-common.h" +#include "qemu/cutils.h" +#include "qapi/error.h" +#include "qemu/guest-random.h" +#include "crypto/random.h" + + +static __thread GRand *thread_rand; +static bool deterministic; + + +static int glib_random_bytes(void *buf, size_t len) +{ + GRand *rand = thread_rand; + size_t i; + uint32_t x; + + if (unlikely(rand == NULL)) { + /* Thread not initialized for a cpu, or main w/o -seed. */ + thread_rand = rand = g_rand_new(); + } + + for (i = 0; i + 4 <= len; i += 4) { + x = g_rand_int(rand); + __builtin_memcpy(buf + i, &x, 4); + } + if (i < len) { + x = g_rand_int(rand); + __builtin_memcpy(buf + i, &x, i - len); + } + return 0; +} + +int qemu_guest_getrandom(void *buf, size_t len, Error **errp) +{ + if (unlikely(deterministic)) { + /* Deterministic implementation using Glib's Mersenne Twister. */ + return glib_random_bytes(buf, len); + } else { + /* Non-deterministic implementation using crypto routines. */ + return qcrypto_random_bytes(buf, len, errp); + } +} + +void qemu_guest_getrandom_nofail(void *buf, size_t len) +{ + qemu_guest_getrandom(buf, len, &error_fatal); +} + +uint64_t qemu_guest_random_seed_thread_part1(void) +{ + if (deterministic) { + uint64_t ret; + glib_random_bytes(&ret, sizeof(ret)); + return ret; + } + return 0; +} + +void qemu_guest_random_seed_thread_part2(uint64_t seed) +{ + g_assert(thread_rand == NULL); + if (deterministic) { + thread_rand = + g_rand_new_with_seed_array((const guint32 *)&seed, + sizeof(seed) / sizeof(guint32)); + } +} + +int qemu_guest_random_seed_main(const char *optarg, Error **errp) +{ + unsigned long long seed; + if (parse_uint_full(optarg, &seed, 0)) { + error_setg(errp, "Invalid seed number: %s", optarg); + return -1; + } else { + deterministic = true; + qemu_guest_random_seed_thread_part2(seed); + return 0; + } +} |