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 #include <crypto/sha2/sha256.h> 45 #include <dev/random/randomdev.h> 46 #include <machine/cpu.h> 47 48 #define CHACHA20_RESEED_BYTES 65536 49 #define CHACHA20_RESEED_SECONDS 300 50 #define CHACHA20_KEYBYTES 32 51 #define CHACHA20_BUFFER_SIZE 64 52 53 CTASSERT(CHACHA20_KEYBYTES*8 >= CHACHA_MINKEYLEN); 54 55 int arc4rand_iniseed_state = ARC4_ENTR_NONE; 56 57 MALLOC_DEFINE(M_CHACHA20RANDOM, "chacha20random", "chacha20random structures"); 58 59 struct chacha20_s { 60 struct mtx mtx; 61 int numbytes; 62 time_t t_reseed; 63 u_int8_t m_buffer[CHACHA20_BUFFER_SIZE]; 64 struct chacha_ctx ctx; 65 } __aligned(CACHE_LINE_SIZE); 66 67 static struct chacha20_s *chacha20inst = NULL; 68 69 #define CHACHA20_FOREACH(_chacha20) \ 70 for (_chacha20 = &chacha20inst[0]; \ 71 _chacha20 <= &chacha20inst[mp_maxid]; \ 72 _chacha20++) 73 74 /* 75 * Mix up the current context. 76 */ 77 static void 78 chacha20_randomstir(struct chacha20_s *chacha20) 79 { 80 struct timeval tv_now; 81 u_int8_t key[CHACHA20_KEYBYTES]; 82 83 if (__predict_false(random_bypass_before_seeding && !is_random_seeded())) { 84 SHA256_CTX ctx; 85 uint64_t cc; 86 uint32_t fver; 87 88 if (!arc4random_bypassed_before_seeding) { 89 arc4random_bypassed_before_seeding = true; 90 if (!random_bypass_disable_warnings) 91 printf("arc4random: WARNING: initial seeding " 92 "bypassed the cryptographic random device " 93 "because it was not yet seeded and the " 94 "knob 'bypass_before_seeding' was " 95 "enabled.\n"); 96 } 97 98 /* Last ditch effort to inject something in a bad condition. */ 99 cc = get_cyclecount(); 100 SHA256_Init(&ctx); 101 SHA256_Update(&ctx, key, sizeof(key)); 102 SHA256_Update(&ctx, &cc, sizeof(cc)); 103 fver = __FreeBSD_version; 104 SHA256_Update(&ctx, &fver, sizeof(fver)); 105 _Static_assert(sizeof(key) == SHA256_DIGEST_LENGTH, 106 "make sure 256 bits is still 256 bits"); 107 SHA256_Final(key, &ctx); 108 } else { 109 /* 110 * If the loader(8) did not have an entropy stash from the 111 * previous shutdown to load, then we will block. The answer is 112 * to make sure there is an entropy stash at shutdown time. 113 * 114 * On the other hand, if the random_bypass_before_seeding knob 115 * was set and we landed in this branch, we know this won't 116 * block because we know the random device is seeded. 117 */ 118 read_random(key, CHACHA20_KEYBYTES); 119 } 120 getmicrouptime(&tv_now); 121 mtx_lock(&chacha20->mtx); 122 chacha_keysetup(&chacha20->ctx, key, CHACHA20_KEYBYTES*8); 123 chacha_ivsetup(&chacha20->ctx, (u_char *)&tv_now.tv_sec, (u_char *)&tv_now.tv_usec); 124 /* Reset for next reseed cycle. */ 125 chacha20->t_reseed = tv_now.tv_sec + CHACHA20_RESEED_SECONDS; 126 chacha20->numbytes = 0; 127 mtx_unlock(&chacha20->mtx); 128 } 129 130 /* 131 * Initialize the contexts. 132 */ 133 static void 134 chacha20_init(void) 135 { 136 struct chacha20_s *chacha20; 137 138 chacha20inst = malloc((mp_maxid + 1) * sizeof(struct chacha20_s), 139 M_CHACHA20RANDOM, M_NOWAIT | M_ZERO); 140 KASSERT(chacha20inst != NULL, ("chacha20_init: memory allocation error")); 141 142 CHACHA20_FOREACH(chacha20) { 143 mtx_init(&chacha20->mtx, "chacha20_mtx", NULL, MTX_DEF); 144 chacha20->t_reseed = -1; 145 chacha20->numbytes = 0; 146 explicit_bzero(chacha20->m_buffer, CHACHA20_BUFFER_SIZE); 147 explicit_bzero(&chacha20->ctx, sizeof(chacha20->ctx)); 148 } 149 } 150 SYSINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_init, NULL); 151 152 153 static void 154 chacha20_uninit(void) 155 { 156 struct chacha20_s *chacha20; 157 158 CHACHA20_FOREACH(chacha20) 159 mtx_destroy(&chacha20->mtx); 160 free(chacha20inst, M_CHACHA20RANDOM); 161 } 162 SYSUNINIT(chacha20, SI_SUB_LOCK, SI_ORDER_ANY, chacha20_uninit, NULL); 163 164 165 /* 166 * MPSAFE 167 */ 168 void 169 arc4rand(void *ptr, u_int len, int reseed) 170 { 171 struct chacha20_s *chacha20; 172 struct timeval tv; 173 u_int length; 174 u_int8_t *p; 175 176 if (__predict_false(reseed || 177 (arc4rand_iniseed_state == ARC4_ENTR_HAVE && 178 atomic_cmpset_int(&arc4rand_iniseed_state, ARC4_ENTR_HAVE, ARC4_ENTR_SEED)))) 179 CHACHA20_FOREACH(chacha20) 180 chacha20_randomstir(chacha20); 181 182 getmicrouptime(&tv); 183 chacha20 = &chacha20inst[curcpu]; 184 /* We may get unlucky and be migrated off this CPU, but that is expected to be infrequent */ 185 if ((chacha20->numbytes > CHACHA20_RESEED_BYTES) || (tv.tv_sec > chacha20->t_reseed)) 186 chacha20_randomstir(chacha20); 187 188 p = ptr; 189 mtx_lock(&chacha20->mtx); 190 while (len) { 191 length = MIN(CHACHA20_BUFFER_SIZE, len); 192 chacha_encrypt_bytes(&chacha20->ctx, chacha20->m_buffer, p, length); 193 p += length; 194 len -= length; 195 chacha20->numbytes += length; 196 if (chacha20->numbytes > CHACHA20_RESEED_BYTES) { 197 mtx_unlock(&chacha20->mtx); 198 chacha20_randomstir(chacha20); 199 mtx_lock(&chacha20->mtx); 200 } 201 } 202 mtx_unlock(&chacha20->mtx); 203 } 204 205 uint32_t 206 arc4random(void) 207 { 208 uint32_t ret; 209 210 arc4rand(&ret, sizeof(ret), 0); 211 return ret; 212 } 213 214 void 215 arc4random_buf(void *ptr, size_t len) 216 { 217 218 arc4rand(ptr, len, 0); 219 } 220