1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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/cdefs.h> 29 __FBSDID("$FreeBSD$"); 30 31 #include <sys/param.h> 32 #include <sys/fail.h> 33 #include <sys/limits.h> 34 #include <sys/lock.h> 35 #include <sys/kernel.h> 36 #include <sys/malloc.h> 37 #include <sys/mutex.h> 38 #include <sys/random.h> 39 #include <sys/sdt.h> 40 #include <sys/sysctl.h> 41 #include <sys/systm.h> 42 43 #include <machine/cpu.h> 44 #include <machine/stdarg.h> 45 46 #define CHACHA_EMBED 47 #define KEYSTREAM_ONLY 48 #define CHACHA_NONCE0_CTR128 49 #include <crypto/chacha20/chacha.h> 50 #include <crypto/rijndael/rijndael-api-fst.h> 51 #include <crypto/sha2/sha256.h> 52 53 #include <dev/random/hash.h> 54 #include <dev/random/randomdev.h> 55 #include <dev/random/random_harvestq.h> 56 #include <dev/random/uint128.h> 57 58 #include <dev/random/fenestrasX/fx_hash.h> 59 #include <dev/random/fenestrasX/fx_priv.h> 60 #include <dev/random/fenestrasX/fx_rng.h> 61 62 _Static_assert(FX_CHACHA20_KEYSIZE == RANDOM_KEYSIZE, ""); 63 64 #include <crypto/chacha20/chacha.c> 65 66 static void 67 fxrng_rng_keystream_internal(struct chacha_ctx *prf, void *buf, size_t nbytes) 68 { 69 size_t chunklen; 70 71 while (nbytes > 0) { 72 chunklen = MIN(nbytes, 73 rounddown((size_t)UINT32_MAX, CHACHA_BLOCKLEN)); 74 75 chacha_encrypt_bytes(prf, NULL, buf, chunklen); 76 buf = (uint8_t *)buf + chunklen; 77 nbytes -= chunklen; 78 } 79 } 80 81 /* 82 * This subroutine pulls the counter out of Chacha, which for whatever reason 83 * always encodes and decodes counters in a little endian format, and adds 84 * 'addend' to it, saving the result in Chacha. 85 */ 86 static void 87 fxrng_chacha_nonce_add64(struct chacha_ctx *ctx, uint64_t addend) 88 { 89 uint128_t ctr; /* Native-endian. */ 90 #if BYTE_ORDER == BIG_ENDIAN 91 uint128_t lectr; 92 93 chacha_ctrsave(ctx, (void *)&lectr); 94 ctr = le128dec(&lectr); 95 #else 96 chacha_ctrsave(ctx, (void *)&ctr); 97 #endif 98 99 uint128_add64(&ctr, addend); 100 101 /* chacha_ivsetup() does not modify the key, and we rely on that. */ 102 #if BYTE_ORDER == BIG_ENDIAN 103 le128enc(&lectr, ctr); 104 chacha_ivsetup(ctx, NULL, (const void *)&lectr); 105 explicit_bzero(&lectr, sizeof(lectr)); 106 #else 107 chacha_ivsetup(ctx, NULL, (const void *)&ctr); 108 #endif 109 explicit_bzero(&ctr, sizeof(ctr)); 110 } 111 112 /* 113 * Generate from the unbuffered source PRNG. 114 * 115 * Handles fast key erasure (rekeys the PRF with a generated key under lock). 116 * 117 * RNG lock is required on entry. If return_unlocked is true, RNG lock will 118 * be dropped on return. 119 */ 120 void 121 fxrng_rng_genrandom_internal(struct fxrng_basic_rng *rng, void *buf, 122 size_t nbytes, bool return_unlocked) 123 { 124 struct chacha_ctx ctx_copy, *p_ctx; 125 uint8_t newkey[FX_CHACHA20_KEYSIZE]; 126 size_t blockcount; 127 128 FXRNG_RNG_ASSERT(rng); 129 130 /* Save off the initial output of the generator for rekeying. */ 131 fxrng_rng_keystream_internal(&rng->rng_prf, newkey, sizeof(newkey)); 132 133 if (return_unlocked) { 134 memcpy(&ctx_copy, &rng->rng_prf, sizeof(ctx_copy)); 135 p_ctx = &ctx_copy; 136 137 /* 138 * Forward the Chacha counter state over the blocks we promise 139 * to generate for the caller without the lock. 140 */ 141 blockcount = howmany(nbytes, CHACHA_BLOCKLEN); 142 fxrng_chacha_nonce_add64(&rng->rng_prf, blockcount); 143 144 /* Re-key before dropping the lock. */ 145 chacha_keysetup(&rng->rng_prf, newkey, sizeof(newkey) * 8); 146 explicit_bzero(newkey, sizeof(newkey)); 147 148 FXRNG_RNG_UNLOCK(rng); 149 } else { 150 p_ctx = &rng->rng_prf; 151 } 152 153 fxrng_rng_keystream_internal(p_ctx, buf, nbytes); 154 155 if (return_unlocked) { 156 explicit_bzero(&ctx_copy, sizeof(ctx_copy)); 157 FXRNG_RNG_ASSERT_NOT(rng); 158 } else { 159 /* Re-key before exit. */ 160 chacha_keysetup(&rng->rng_prf, newkey, sizeof(newkey) * 8); 161 explicit_bzero(newkey, sizeof(newkey)); 162 FXRNG_RNG_ASSERT(rng); 163 } 164 } 165 166 /* 167 * Helper to reseed the root RNG, incorporating the existing RNG state. 168 * 169 * The root RNG is locked on entry and locked on return. 170 */ 171 static void 172 fxrng_rng_reseed_internal(struct fxrng_basic_rng *rng, bool seeded, 173 const void *src, size_t sz, ...) 174 { 175 union { 176 uint8_t root_state[FX_CHACHA20_KEYSIZE]; 177 uint8_t hash_out[FXRNG_HASH_SZ]; 178 } u; 179 struct fxrng_hash mix; 180 va_list ap; 181 182 _Static_assert(FX_CHACHA20_KEYSIZE <= FXRNG_HASH_SZ, ""); 183 184 FXRNG_RNG_ASSERT(rng); 185 186 fxrng_hash_init(&mix); 187 if (seeded) { 188 fxrng_rng_keystream_internal(&rng->rng_prf, u.root_state, 189 sizeof(u.root_state)); 190 fxrng_hash_update(&mix, u.root_state, sizeof(u.root_state)); 191 } 192 fxrng_hash_update(&mix, src, sz); 193 194 va_start(ap, sz); 195 while (true) { 196 src = va_arg(ap, const void *); 197 if (src == NULL) 198 break; 199 sz = va_arg(ap, size_t); 200 fxrng_hash_update(&mix, src, sz); 201 } 202 va_end(ap); 203 204 fxrng_hash_finish(&mix, u.hash_out, sizeof(u.hash_out)); 205 206 /* 207 * Take the first keysize (32) bytes of our digest (64 bytes). It is 208 * also possible to just have Blake2 emit fewer bytes, but our wrapper 209 * API doesn't provide that functionality and there isn't anything 210 * obviously wrong with emitting more hash bytes. 211 * 212 * keysetup does not reset the embedded counter, and we rely on that 213 * property. 214 */ 215 chacha_keysetup(&rng->rng_prf, u.hash_out, FX_CHACHA20_KEYSIZE * 8); 216 217 /* 'mix' zeroed by fxrng_hash_finish(). */ 218 explicit_bzero(u.hash_out, sizeof(u.hash_out)); 219 220 FXRNG_RNG_ASSERT(rng); 221 } 222 223 /* 224 * Directly reseed the root RNG from a first-time entropy source, 225 * incorporating the existing RNG state, called by fxrng_brng_src_reseed. 226 * 227 * The root RNG is locked on entry and locked on return. 228 */ 229 void 230 fxrng_rng_src_reseed(struct fxrng_basic_rng *rng, 231 const struct harvest_event *event) 232 { 233 fxrng_rng_reseed_internal(rng, true, &event->he_somecounter, 234 sizeof(event->he_somecounter), (const void *)event->he_entropy, 235 (size_t)event->he_size, NULL); 236 } 237 238 /* 239 * Reseed the root RNG from pooled entropy, incorporating the existing RNG 240 * state, called by fxrng_brng_reseed. 241 * 242 * The root RNG is locked on entry and locked on return. 243 */ 244 void 245 fxrng_rng_reseed(struct fxrng_basic_rng *rng, bool seeded, const void *entr, 246 size_t sz) 247 { 248 fxrng_rng_reseed_internal(rng, seeded, entr, sz, NULL); 249 } 250