1 /*- 2 * Copyright (c) 2017 The FreeBSD Foundation 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer 9 * in this position and unchanged. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 */ 26 27 #include <sys/cdefs.h> 28 #include <sys/types.h> 29 #include <sys/param.h> 30 #include <sys/kernel.h> 31 #include <sys/libkern.h> 32 #include <sys/linker.h> 33 #include <sys/lock.h> 34 #include <sys/malloc.h> 35 #include <sys/msan.h> 36 #include <sys/mutex.h> 37 #include <sys/random.h> 38 #include <sys/smp.h> 39 #include <sys/time.h> 40 41 #include <machine/cpu.h> 42 43 #include <crypto/chacha20/chacha.h> 44 #include <crypto/sha2/sha256.h> 45 #include <dev/random/randomdev.h> 46 #ifdef RANDOM_FENESTRASX 47 #include <dev/random/fenestrasX/fx_pub.h> 48 #endif 49 50 #define CHACHA20_RESEED_BYTES 65536 51 #define CHACHA20_RESEED_SECONDS 300 52 #define CHACHA20_KEYBYTES 32 53 #define CHACHA20_BUFFER_SIZE 64 54 55 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN); 56 57 #ifndef RANDOM_FENESTRASX 58 int arc4rand_iniseed_state = ARC4_ENTR_NONE; 59 #endif 60 61 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures"); 62 63 struct chacha20_s { 64 struct mtx mtx; 65 int numbytes; 66 time_t t_reseed; 67 uint8_t m_buffer[CHACHA20_BUFFER_SIZE]; 68 struct chacha_ctx ctx; 69 #ifdef RANDOM_FENESTRASX 70 uint64_t seed_version; 71 #endif 72 } __aligned(CACHE_LINE_SIZE); 73 74 static struct chacha20_s *chacha20inst = NULL; 75 76 #define CHACHA20_FOREACH(_chacha20) \ 77 for (_chacha20 = &chacha20inst[0]; \ 78 _chacha20 <= &chacha20inst[mp_maxid]; \ 79 _chacha20++) 80 81 /* 82 * Mix up the current context. 83 */ 84 static void 85 chacha20_randomstir(struct chacha20_s *chacha20) 86 { 87 struct timeval tv_now; 88 uint8_t key[CHACHA20_KEYBYTES]; 89 #ifdef RANDOM_FENESTRASX 90 uint64_t seed_version; 91 92 #else 93 if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) { 94 SHA256_CTX ctx; 95 uint64_t cc; 96 uint32_t fver; 97 98 if (!arc4random_bypassed_before_seeding) { 99 arc4random_bypassed_before_seeding = true; 100 if (!random_bypass_disable_warnings) 101 printf("arc4random: WARNING: initial seeding " 102 "bypassed the cryptographic random device " 103 "because it was not yet seeded and the " 104 "knob 'bypass_before_seeding' was " 105 "enabled.\n"); 106 } 107 108 /* 109 * "key" is intentionally left uninitialized here, so with KMSAN 110 * enabled the arc4random() return value may be marked 111 * uninitialized, leading to spurious reports. Lie to KMSAN to 112 * avoid this situation. 113 */ 114 kmsan_mark(key, sizeof(key), KMSAN_STATE_INITED); 115 116 /* Last ditch effort to inject something in a bad condition. */ 117 cc = get_cyclecount(); 118 SHA256_Init(&ctx); 119 SHA256_Update(&ctx, key, sizeof(key)); 120 SHA256_Update(&ctx, &cc, sizeof(cc)); 121 fver = __FreeBSD_version; 122 SHA256_Update(&ctx, &fver, sizeof(fver)); 123 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH, 124 "make sure 256 bits is still 256 bits"); 125 SHA256_Final(key, &ctx); 126 } else { 127 #endif 128 #ifdef RANDOM_FENESTRASX 129 read_random_key(key, CHACHA20_KEYBYTES, &seed_version); 130 #else 131 /* 132 * If the loader(8) did not have an entropy stash from the 133 * previous shutdown to load, then we will block. The answer is 134 * to make sure there is an entropy stash at shutdown time. 135 * 136 * On the other hand, if the random_bypass_before_seeding knob 137 * was set and we landed in this branch, we know this won't 138 * block because we know the random device is seeded. 139 */ 140 read_random(key, CHACHA20_KEYBYTES); 141 } 142 #endif 143 getmicrouptime(&tv_now); 144 mtx_lock(&chacha20->mtx); 145 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8); 146 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec); 147 /* Reset for next reseed cycle. */ 148 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS; 149 chacha20->numbytes = 0; 150 #ifdef RANDOM_FENESTRASX 151 chacha20->seed_version = seed_version; 152 #endif 153 mtx_unlock(&chacha20->mtx); 154 } 155 156 /* 157 * Initialize the contexts. 158 */ 159 static void 160 chacha20_init(void) 161 { 162 struct chacha20_s *chacha20; 163 164 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s), 165 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO); 166 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error")); 167 168 CHACHA20_FOREACH(chacha20) { 169 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF); 170 chacha20->t_reseed = -1; 171 chacha20->numbytes = 0; 172 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE); 173 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx)); 174 } 175 } 176 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL); 177 178 179 static void 180 chacha20_uninit(void) 181 { 182 struct chacha20_s *chacha20; 183 184 CHACHA20_FOREACH(chacha20) 185 mtx_destroy(&chacha20->mtx); 186 free(chacha20inst, M_CHACHA20RANDOM); 187 } 188 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL); 189 190 191 /* 192 * MPSAFE 193 */ 194 void 195 arc4rand(void *ptr, u_int len, int reseed) 196 { 197 struct chacha20_s *chacha20; 198 struct timeval tv; 199 u_int length; 200 uint8_t *p; 201 202 #ifdef RANDOM_FENESTRASX 203 if (__predict_false(reseed)) 204 #else 205 if (__predict_false(reseed || 206 (arc4rand_iniseed_state == ARC4_ENTR_HAVE && 207 atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED)))) 208 #endif 209 CHACHA20_FOREACH(chacha20) 210 chacha20_randomstir(chacha20); 211 212 getmicrouptime(&tv); 213 chacha20 = &chacha20inst[curcpu]; 214 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */ 215 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed)) 216 chacha20_randomstir(chacha20); 217 218 mtx_lock(&chacha20->mtx); 219 #ifdef RANDOM_FENESTRASX 220 if (__predict_false( 221 atomic_load_acq_64(&fxrng_root_generation) != chacha20->seed_version 222 )) { 223 mtx_unlock(&chacha20->mtx); 224 chacha20_randomstir(chacha20); 225 mtx_lock(&chacha20->mtx); 226 } 227 #endif 228 229 p = ptr; 230 while (len) { 231 length = MIN(CHACHA20_BUFFER_SIZE, len); 232 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length); 233 p += length; 234 len -= length; 235 chacha20->numbytes += length; 236 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) { 237 mtx_unlock(&chacha20->mtx); 238 chacha20_randomstir(chacha20); 239 mtx_lock(&chacha20->mtx); 240 } 241 } 242 mtx_unlock(&chacha20->mtx); 243 } 244 245 uint32_t 246 arc4random(void) 247 { 248 uint32_t ret; 249 250 arc4rand(&ret, sizeof(ret), 0); 251 return ret; 252 } 253 254 void 255 arc4random_buf(void *ptr, size_t len) 256 { 257 258 arc4rand(ptr, len, 0); 259 } 260