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/types.h> 28 #include <sys/param.h> 29 #include <sys/kernel.h> 30 #include <sys/libkern.h> 31 #include <sys/linker.h> 32 #include <sys/lock.h> 33 #include <sys/malloc.h> 34 #include <sys/msan.h> 35 #include <sys/mutex.h> 36 #include <sys/random.h> 37 #include <sys/smp.h> 38 #include <sys/time.h> 39 40 #include <machine/cpu.h> 41 42 #include <crypto/chacha20/chacha.h> 43 #include <crypto/sha2/sha256.h> 44 #include <dev/random/randomdev.h> 45 #ifdef RANDOM_FENESTRASX 46 #include <dev/random/fenestrasX/fx_pub.h> 47 #endif 48 49 #define CHACHA20_RESEED_BYTES 65536 50 #define CHACHA20_RESEED_SECONDS 300 51 #define CHACHA20_KEYBYTES 32 52 #define CHACHA20_BUFFER_SIZE 64 53 54 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN); 55 56 #ifndef RANDOM_FENESTRASX 57 int arc4rand_iniseed_state = ARC4_ENTR_NONE; 58 #endif 59 60 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures"); 61 62 struct chacha20_s { 63 struct mtx mtx; 64 int numbytes; 65 time_t t_reseed; 66 uint8_t m_buffer[CHACHA20_BUFFER_SIZE]; 67 struct chacha_ctx ctx; 68 #ifdef RANDOM_FENESTRASX 69 uint64_t seed_version; 70 #endif 71 } __aligned(CACHE_LINE_SIZE); 72 73 static struct chacha20_s *chacha20inst = NULL; 74 75 #define CHACHA20_FOREACH(_chacha20) \ 76 for (_chacha20 = &chacha20inst[0]; \ 77 _chacha20 <= &chacha20inst[mp_maxid]; \ 78 _chacha20++) 79 80 /* 81 * Mix up the current context. 82 */ 83 static void 84 chacha20_randomstir(struct chacha20_s *chacha20) 85 { 86 struct timeval tv_now; 87 uint8_t key[CHACHA20_KEYBYTES]; 88 #ifdef RANDOM_FENESTRASX 89 uint64_t seed_version; 90 91 #else 92 if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) { 93 SHA256_CTX ctx; 94 uint64_t cc; 95 uint32_t fver; 96 97 if (!arc4random_bypassed_before_seeding) { 98 arc4random_bypassed_before_seeding = true; 99 if (!random_bypass_disable_warnings) 100 printf("arc4random: WARNING: initial seeding " 101 "bypassed the cryptographic random device " 102 "because it was not yet seeded and the " 103 "knob 'bypass_before_seeding' was " 104 "enabled.\n"); 105 } 106 107 /* 108 * "key" is intentionally left uninitialized here, so with KMSAN 109 * enabled the arc4random() return value may be marked 110 * uninitialized, leading to spurious reports. Lie to KMSAN to 111 * avoid this situation. 112 */ 113 kmsan_mark(key, sizeof(key), KMSAN_STATE_INITED); 114 115 /* Last ditch effort to inject something in a bad condition. */ 116 cc = get_cyclecount(); 117 SHA256_Init(&ctx); 118 SHA256_Update(&ctx, key, sizeof(key)); 119 SHA256_Update(&ctx, &cc, sizeof(cc)); 120 fver = __FreeBSD_version; 121 SHA256_Update(&ctx, &fver, sizeof(fver)); 122 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH, 123 "make sure 256 bits is still 256 bits"); 124 SHA256_Final(key, &ctx); 125 } else { 126 #endif 127 #ifdef RANDOM_FENESTRASX 128 read_random_key(key, CHACHA20_KEYBYTES, &seed_version); 129 #else 130 /* 131 * If the loader(8) did not have an entropy stash from the 132 * previous shutdown to load, then we will block. The answer is 133 * to make sure there is an entropy stash at shutdown time. 134 * 135 * On the other hand, if the random_bypass_before_seeding knob 136 * was set and we landed in this branch, we know this won't 137 * block because we know the random device is seeded. 138 */ 139 read_random(key, CHACHA20_KEYBYTES); 140 } 141 #endif 142 getmicrouptime(&tv_now); 143 mtx_lock(&chacha20->mtx); 144 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8); 145 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec); 146 /* Reset for next reseed cycle. */ 147 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS; 148 chacha20->numbytes = 0; 149 #ifdef RANDOM_FENESTRASX 150 chacha20->seed_version = seed_version; 151 #endif 152 mtx_unlock(&chacha20->mtx); 153 } 154 155 /* 156 * Initialize the contexts. 157 */ 158 static void 159 chacha20_init(void) 160 { 161 struct chacha20_s *chacha20; 162 163 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s), 164 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO); 165 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error")); 166 167 CHACHA20_FOREACH(chacha20) { 168 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF); 169 chacha20->t_reseed = -1; 170 chacha20->numbytes = 0; 171 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE); 172 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx)); 173 } 174 } 175 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL); 176 177 178 static void 179 chacha20_uninit(void) 180 { 181 struct chacha20_s *chacha20; 182 183 CHACHA20_FOREACH(chacha20) 184 mtx_destroy(&chacha20->mtx); 185 free(chacha20inst, M_CHACHA20RANDOM); 186 } 187 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL); 188 189 190 /* 191 * MPSAFE 192 */ 193 void 194 arc4rand(void *ptr, u_int len, int reseed) 195 { 196 struct chacha20_s *chacha20; 197 struct timeval tv; 198 u_int length; 199 uint8_t *p; 200 201 #ifdef RANDOM_FENESTRASX 202 if (__predict_false(reseed)) 203 #else 204 if (__predict_false(reseed || 205 (arc4rand_iniseed_state == ARC4_ENTR_HAVE && 206 atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED)))) 207 #endif 208 CHACHA20_FOREACH(chacha20) 209 chacha20_randomstir(chacha20); 210 211 getmicrouptime(&tv); 212 chacha20 = &chacha20inst[curcpu]; 213 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */ 214 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed)) 215 chacha20_randomstir(chacha20); 216 217 mtx_lock(&chacha20->mtx); 218 #ifdef RANDOM_FENESTRASX 219 if (__predict_false( 220 atomic_load_acq_64(&fxrng_root_generation) != chacha20->seed_version 221 )) { 222 mtx_unlock(&chacha20->mtx); 223 chacha20_randomstir(chacha20); 224 mtx_lock(&chacha20->mtx); 225 } 226 #endif 227 228 p = ptr; 229 while (len) { 230 length = MIN(CHACHA20_BUFFER_SIZE, len); 231 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length); 232 p += length; 233 len -= length; 234 chacha20->numbytes += length; 235 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) { 236 mtx_unlock(&chacha20->mtx); 237 chacha20_randomstir(chacha20); 238 mtx_lock(&chacha20->mtx); 239 } 240 } 241 mtx_unlock(&chacha20->mtx); 242 } 243 244 uint32_t 245 arc4random(void) 246 { 247 uint32_t ret; 248 249 arc4rand(&ret, sizeof(ret), 0); 250 return ret; 251 } 252 253 void 254 arc4random_buf(void *ptr, size_t len) 255 { 256 257 arc4rand(ptr, len, 0); 258 } 259