1 /*- 2 * Copyright (c) 2017 The FreeBSD Foundation 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer 10 * in this position and unchanged. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 */ 27 28 #include <sys/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include <sys/types.h> 32 #include <sys/param.h> 33 #include <sys/kernel.h> 34 #include <sys/libkern.h> 35 #include <sys/linker.h> 36 #include <sys/lock.h> 37 #include <sys/malloc.h> 38 #include <sys/mutex.h> 39 #include <sys/random.h> 40 #include <sys/smp.h> 41 #include <sys/time.h> 42 43 #include <crypto/chacha20/chacha.h> 44 45 #define CHACHA20_RESEED_BYTES 65536 46 #define CHACHA20_RESEED_SECONDS 300 47 #define CHACHA20_KEYBYTES 32 48 #define CHACHA20_BUFFER_SIZE 64 49 50 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN); 51 52 int arc4rand_iniseed_state = ARC4_ENTR_NONE; 53 54 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures"); 55 56 struct chacha20_s { 57 struct mtx mtx; 58 int numbytes; 59 int first_time_done; 60 time_t t_reseed; 61 u_int8_t m_buffer[CHACHA20_BUFFER_SIZE]; 62 struct chacha_ctx ctx; 63 } __aligned(CACHE_LINE_SIZE); 64 65 static struct chacha20_s *chacha20inst = NULL; 66 67 #define CHACHA20_FOREACH(_chacha20) \ 68 for (_chacha20 = &chacha20inst[0]; \ 69 _chacha20 <= &chacha20inst[mp_maxid]; \ 70 _chacha20++) 71 72 /* 73 * Mix up the current context. 74 */ 75 static void 76 chacha20_randomstir(struct chacha20_s* chacha20) 77 { 78 struct timeval tv_now; 79 size_t n, size; 80 u_int8_t key[CHACHA20_KEYBYTES], *data; 81 caddr_t keyfile; 82 83 /* 84 * This is making the best of what may be an insecure 85 * Situation. If the loader(8) did not have an entropy 86 * stash from the previous shutdown to load, then we will 87 * be improperly seeded. The answer is to make sure there 88 * is an entropy stash at shutdown time. 89 */ 90 (void)read_random(key, CHACHA20_KEYBYTES); 91 if (!chacha20->first_time_done) { 92 keyfile = preload_search_by_type(RANDOM_CACHED_BOOT_ENTROPY_MODULE); 93 if (keyfile != NULL) { 94 data = preload_fetch_addr(keyfile); 95 size = MIN(preload_fetch_size(keyfile), CHACHA20_KEYBYTES); 96 for (n = 0; n < size; n++) 97 key[n] ^= data[n]; 98 explicit_bzero(data, size); 99 if (bootverbose) 100 printf("arc4random: read %zu bytes from preloaded cache\n", size); 101 } else 102 printf("arc4random: no preloaded entropy cache\n"); 103 chacha20->first_time_done = 1; 104 } 105 getmicrouptime(&tv_now); 106 mtx_lock(&chacha20->mtx); 107 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8); 108 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec); 109 /* Reset for next reseed cycle. */ 110 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS; 111 chacha20->numbytes = 0; 112 mtx_unlock(&chacha20->mtx); 113 } 114 115 /* 116 * Initialize the contexts. 117 */ 118 static void 119 chacha20_init(void) 120 { 121 struct chacha20_s *chacha20; 122 123 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s), 124 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO); 125 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error")); 126 127 CHACHA20_FOREACH(chacha20) { 128 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF); 129 chacha20->t_reseed = -1; 130 chacha20->numbytes = 0; 131 chacha20->first_time_done = 0; 132 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE); 133 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx)); 134 } 135 } 136 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL); 137 138 139 static void 140 chacha20_uninit(void) 141 { 142 struct chacha20_s *chacha20; 143 144 CHACHA20_FOREACH(chacha20) 145 mtx_destroy(&chacha20->mtx); 146 free(chacha20inst, M_CHACHA20RANDOM); 147 } 148 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL); 149 150 151 /* 152 * MPSAFE 153 */ 154 void 155 arc4rand(void *ptr, u_int len, int reseed) 156 { 157 struct chacha20_s *chacha20; 158 struct timeval tv; 159 u_int length; 160 u_int8_t *p; 161 162 if (reseed || atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED)) 163 CHACHA20_FOREACH(chacha20) 164 chacha20_randomstir(chacha20); 165 166 chacha20 = &chacha20inst[curcpu]; 167 getmicrouptime(&tv); 168 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */ 169 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed)) 170 chacha20_randomstir(chacha20); 171 172 mtx_lock(&chacha20->mtx); 173 p = ptr; 174 while (len) { 175 length = MIN(CHACHA20_BUFFER_SIZE, len); 176 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length); 177 p += length; 178 len -= length; 179 chacha20->numbytes += length; 180 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) { 181 mtx_unlock(&chacha20->mtx); 182 chacha20_randomstir(chacha20); 183 mtx_lock(&chacha20->mtx); 184 } 185 } 186 mtx_unlock(&chacha20->mtx); 187 } 188 189 uint32_t 190 arc4random(void) 191 { 192 uint32_t ret; 193 194 arc4rand(&ret, sizeof(ret), 0); 195 return ret; 196 } 197 198 void 199 arc4random_buf(void *ptr, size_t len) 200 { 201 202 arc4rand(ptr, len, 0); 203 } 204