1 /* 2 * QEMU guest-visible random functions 3 * 4 * Copyright 2019 Linaro, Ltd. 5 * 6 * This program is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License as published by the Free 8 * Software Foundation; either version 2 of the License, or (at your option) 9 * any later version. 10 */ 11 12 #include "qemu/osdep.h" 13 #include "qemu-common.h" 14 #include "qemu/cutils.h" 15 #include "qapi/error.h" 16 #include "qemu/guest-random.h" 17 #include "crypto/random.h" 18 19 20 static __thread GRand *thread_rand; 21 static bool deterministic; 22 23 24 static int glib_random_bytes(void *buf, size_t len) 25 { 26 GRand *rand = thread_rand; 27 size_t i; 28 uint32_t x; 29 30 if (unlikely(rand == NULL)) { 31 /* Thread not initialized for a cpu, or main w/o -seed. */ 32 thread_rand = rand = g_rand_new(); 33 } 34 35 for (i = 0; i + 4 <= len; i += 4) { 36 x = g_rand_int(rand); 37 __builtin_memcpy(buf + i, &x, 4); 38 } 39 if (i < len) { 40 x = g_rand_int(rand); 41 __builtin_memcpy(buf + i, &x, i - len); 42 } 43 return 0; 44 } 45 46 int qemu_guest_getrandom(void *buf, size_t len, Error **errp) 47 { 48 if (unlikely(deterministic)) { 49 /* Deterministic implementation using Glib's Mersenne Twister. */ 50 return glib_random_bytes(buf, len); 51 } else { 52 /* Non-deterministic implementation using crypto routines. */ 53 return qcrypto_random_bytes(buf, len, errp); 54 } 55 } 56 57 void qemu_guest_getrandom_nofail(void *buf, size_t len) 58 { 59 qemu_guest_getrandom(buf, len, &error_fatal); 60 } 61 62 uint64_t qemu_guest_random_seed_thread_part1(void) 63 { 64 if (deterministic) { 65 uint64_t ret; 66 glib_random_bytes(&ret, sizeof(ret)); 67 return ret; 68 } 69 return 0; 70 } 71 72 void qemu_guest_random_seed_thread_part2(uint64_t seed) 73 { 74 g_assert(thread_rand == NULL); 75 if (deterministic) { 76 thread_rand = 77 g_rand_new_with_seed_array((const guint32 *)&seed, 78 sizeof(seed) / sizeof(guint32)); 79 } 80 } 81 82 int qemu_guest_random_seed_main(const char *optarg, Error **errp) 83 { 84 unsigned long long seed; 85 if (parse_uint_full(optarg, &seed, 0)) { 86 error_setg(errp, "Invalid seed number: %s", optarg); 87 return -1; 88 } else { 89 deterministic = true; 90 qemu_guest_random_seed_thread_part2(seed); 91 return 0; 92 } 93 } 94