1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2019 Conrad Meyer <cem@FreeBSD.org> 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 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 AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 28 #include <sys/param.h> 29 #include <sys/fail.h> 30 #include <sys/limits.h> 31 #include <sys/lock.h> 32 #include <sys/kernel.h> 33 #include <sys/malloc.h> 34 #include <sys/mutex.h> 35 #include <sys/random.h> 36 #include <sys/sdt.h> 37 #include <sys/sysctl.h> 38 #include <sys/systm.h> 39 40 #include <machine/cpu.h> 41 #include <machine/stdarg.h> 42 43 #define CHACHA_EMBED 44 #define KEYSTREAM_ONLY 45 #define CHACHA_NONCE0_CTR128 46 #include <crypto/chacha20/chacha.h> 47 #include <crypto/rijndael/rijndael-api-fst.h> 48 #include <crypto/sha2/sha256.h> 49 50 #include <dev/random/hash.h> 51 #include <dev/random/randomdev.h> 52 #include <dev/random/random_harvestq.h> 53 #include <dev/random/uint128.h> 54 55 #include <dev/random/fenestrasX/fx_hash.h> 56 #include <dev/random/fenestrasX/fx_priv.h> 57 #include <dev/random/fenestrasX/fx_rng.h> 58 59 _Static_assert(FX_CHACHA20_KEYSIZE == RANDOM_KEYSIZE, ""); 60 61 #include <crypto/chacha20/chacha.c> 62 63 static void 64 fxrng_rng_keystream_internal(struct chacha_ctx *prf, void *buf, size_t nbytes) 65 { 66 size_t chunklen; 67 68 while (nbytes > 0) { 69 chunklen = MIN(nbytes, 70 rounddown((size_t)UINT32_MAX, CHACHA_BLOCKLEN)); 71 72 chacha_encrypt_bytes(prf, NULL, buf, chunklen); 73 buf = (uint8_t *)buf + chunklen; 74 nbytes -= chunklen; 75 } 76 } 77 78 /* 79 * This subroutine pulls the counter out of Chacha, which for whatever reason 80 * always encodes and decodes counters in a little endian format, and adds 81 * 'addend' to it, saving the result in Chacha. 82 */ 83 static void 84 fxrng_chacha_nonce_add64(struct chacha_ctx *ctx, uint64_t addend) 85 { 86 uint128_t ctr; /* Native-endian. */ 87 #if BYTE_ORDER == BIG_ENDIAN 88 uint128_t lectr; 89 90 chacha_ctrsave(ctx, (void *)&lectr); 91 ctr = le128dec(&lectr); 92 #else 93 chacha_ctrsave(ctx, (void *)&ctr); 94 #endif 95 96 uint128_add64(&ctr, addend); 97 98 /* chacha_ivsetup() does not modify the key, and we rely on that. */ 99 #if BYTE_ORDER == BIG_ENDIAN 100 le128enc(&lectr, ctr); 101 chacha_ivsetup(ctx, NULL, (const void *)&lectr); 102 explicit_bzero(&lectr, sizeof(lectr)); 103 #else 104 chacha_ivsetup(ctx, NULL, (const void *)&ctr); 105 #endif 106 explicit_bzero(&ctr, sizeof(ctr)); 107 } 108 109 /* 110 * Generate from the unbuffered source PRNG. 111 * 112 * Handles fast key erasure (rekeys the PRF with a generated key under lock). 113 * 114 * RNG lock is required on entry. If return_unlocked is true, RNG lock will 115 * be dropped on return. 116 */ 117 void 118 fxrng_rng_genrandom_internal(struct fxrng_basic_rng *rng, void *buf, 119 size_t nbytes, bool return_unlocked) 120 { 121 struct chacha_ctx ctx_copy, *p_ctx; 122 uint8_t newkey[FX_CHACHA20_KEYSIZE]; 123 size_t blockcount; 124 125 FXRNG_RNG_ASSERT(rng); 126 127 /* Save off the initial output of the generator for rekeying. */ 128 fxrng_rng_keystream_internal(&rng->rng_prf, newkey, sizeof(newkey)); 129 130 if (return_unlocked) { 131 memcpy(&ctx_copy, &rng->rng_prf, sizeof(ctx_copy)); 132 p_ctx = &ctx_copy; 133 134 /* 135 * Forward the Chacha counter state over the blocks we promise 136 * to generate for the caller without the lock. 137 */ 138 blockcount = howmany(nbytes, CHACHA_BLOCKLEN); 139 fxrng_chacha_nonce_add64(&rng->rng_prf, blockcount); 140 141 /* Re-key before dropping the lock. */ 142 chacha_keysetup(&rng->rng_prf, newkey, sizeof(newkey) * 8); 143 explicit_bzero(newkey, sizeof(newkey)); 144 145 FXRNG_RNG_UNLOCK(rng); 146 } else { 147 p_ctx = &rng->rng_prf; 148 } 149 150 fxrng_rng_keystream_internal(p_ctx, buf, nbytes); 151 152 if (return_unlocked) { 153 explicit_bzero(&ctx_copy, sizeof(ctx_copy)); 154 FXRNG_RNG_ASSERT_NOT(rng); 155 } else { 156 /* Re-key before exit. */ 157 chacha_keysetup(&rng->rng_prf, newkey, sizeof(newkey) * 8); 158 explicit_bzero(newkey, sizeof(newkey)); 159 FXRNG_RNG_ASSERT(rng); 160 } 161 } 162 163 /* 164 * Helper to reseed the root RNG, incorporating the existing RNG state. 165 * 166 * The root RNG is locked on entry and locked on return. 167 */ 168 static void 169 fxrng_rng_reseed_internal(struct fxrng_basic_rng *rng, bool seeded, 170 const void *src, size_t sz, ...) 171 { 172 union { 173 uint8_t root_state[FX_CHACHA20_KEYSIZE]; 174 uint8_t hash_out[FXRNG_HASH_SZ]; 175 } u; 176 struct fxrng_hash mix; 177 va_list ap; 178 179 _Static_assert(FX_CHACHA20_KEYSIZE <= FXRNG_HASH_SZ, ""); 180 181 FXRNG_RNG_ASSERT(rng); 182 183 fxrng_hash_init(&mix); 184 if (seeded) { 185 fxrng_rng_keystream_internal(&rng->rng_prf, u.root_state, 186 sizeof(u.root_state)); 187 fxrng_hash_update(&mix, u.root_state, sizeof(u.root_state)); 188 } 189 fxrng_hash_update(&mix, src, sz); 190 191 va_start(ap, sz); 192 while (true) { 193 src = va_arg(ap, const void *); 194 if (src == NULL) 195 break; 196 sz = va_arg(ap, size_t); 197 fxrng_hash_update(&mix, src, sz); 198 } 199 va_end(ap); 200 201 fxrng_hash_finish(&mix, u.hash_out, sizeof(u.hash_out)); 202 203 /* 204 * Take the first keysize (32) bytes of our digest (64 bytes). It is 205 * also possible to just have Blake2 emit fewer bytes, but our wrapper 206 * API doesn't provide that functionality and there isn't anything 207 * obviously wrong with emitting more hash bytes. 208 * 209 * keysetup does not reset the embedded counter, and we rely on that 210 * property. 211 */ 212 chacha_keysetup(&rng->rng_prf, u.hash_out, FX_CHACHA20_KEYSIZE * 8); 213 214 /* 'mix' zeroed by fxrng_hash_finish(). */ 215 explicit_bzero(u.hash_out, sizeof(u.hash_out)); 216 217 FXRNG_RNG_ASSERT(rng); 218 } 219 220 /* 221 * Directly reseed the root RNG from a first-time entropy source, 222 * incorporating the existing RNG state, called by fxrng_brng_src_reseed. 223 * 224 * The root RNG is locked on entry and locked on return. 225 */ 226 void 227 fxrng_rng_src_reseed(struct fxrng_basic_rng *rng, 228 const struct harvest_event *event) 229 { 230 fxrng_rng_reseed_internal(rng, true, &event->he_somecounter, 231 sizeof(event->he_somecounter), (const void *)event->he_entropy, 232 (size_t)event->he_size, NULL); 233 } 234 235 /* 236 * Reseed the root RNG from pooled entropy, incorporating the existing RNG 237 * state, called by fxrng_brng_reseed. 238 * 239 * The root RNG is locked on entry and locked on return. 240 */ 241 void 242 fxrng_rng_reseed(struct fxrng_basic_rng *rng, bool seeded, const void *entr, 243 size_t sz) 244 { 245 fxrng_rng_reseed_internal(rng, seeded, entr, sz, NULL); 246 } 247