| 1 | /* $NetBSD: cprng_fast.c,v 1.13 2015/04/13 22:43:41 riastradh Exp $ */ |
| 2 | |
| 3 | /*- |
| 4 | * Copyright (c) 2014 The NetBSD Foundation, Inc. |
| 5 | * All rights reserved. |
| 6 | * |
| 7 | * This code is derived from software contributed to The NetBSD Foundation |
| 8 | * by Taylor R. Campbell. |
| 9 | * |
| 10 | * Redistribution and use in source and binary forms, with or without |
| 11 | * modification, are permitted provided that the following conditions |
| 12 | * are met: |
| 13 | * 1. Redistributions of source code must retain the above copyright |
| 14 | * notice, this list of conditions and the following disclaimer. |
| 15 | * 2. Redistributions in binary form must reproduce the above copyright |
| 16 | * notice, this list of conditions and the following disclaimer in the |
| 17 | * documentation and/or other materials provided with the distribution. |
| 18 | * |
| 19 | * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS |
| 20 | * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
| 21 | * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| 22 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS |
| 23 | * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 24 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 25 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 26 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 27 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 28 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 29 | * POSSIBILITY OF SUCH DAMAGE. |
| 30 | */ |
| 31 | |
| 32 | #include <sys/cdefs.h> |
| 33 | __KERNEL_RCSID(0, "$NetBSD: cprng_fast.c,v 1.13 2015/04/13 22:43:41 riastradh Exp $" ); |
| 34 | |
| 35 | #include <sys/types.h> |
| 36 | #include <sys/param.h> |
| 37 | #include <sys/bitops.h> |
| 38 | #include <sys/cprng.h> |
| 39 | #include <sys/cpu.h> |
| 40 | #include <sys/intr.h> |
| 41 | #include <sys/percpu.h> |
| 42 | #include <sys/rnd.h> /* rnd_initial_entropy */ |
| 43 | |
| 44 | /* ChaCha core */ |
| 45 | |
| 46 | #define crypto_core_OUTPUTWORDS 16 |
| 47 | #define crypto_core_INPUTWORDS 4 |
| 48 | #define crypto_core_KEYWORDS 8 |
| 49 | #define crypto_core_CONSTWORDS 4 |
| 50 | |
| 51 | #define crypto_core_ROUNDS 8 |
| 52 | |
| 53 | static uint32_t |
| 54 | rotate(uint32_t u, unsigned c) |
| 55 | { |
| 56 | |
| 57 | return (u << c) | (u >> (32 - c)); |
| 58 | } |
| 59 | |
| 60 | #define QUARTERROUND(a, b, c, d) do { \ |
| 61 | (a) += (b); (d) ^= (a); (d) = rotate((d), 16); \ |
| 62 | (c) += (d); (b) ^= (c); (b) = rotate((b), 12); \ |
| 63 | (a) += (b); (d) ^= (a); (d) = rotate((d), 8); \ |
| 64 | (c) += (d); (b) ^= (c); (b) = rotate((b), 7); \ |
| 65 | } while (0) |
| 66 | |
| 67 | static void |
| 68 | crypto_core(uint32_t *out, const uint32_t *in, const uint32_t *k, |
| 69 | const uint32_t *c) |
| 70 | { |
| 71 | uint32_t x0,x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12,x13,x14,x15; |
| 72 | int i; |
| 73 | |
| 74 | x0 = c[0]; |
| 75 | x1 = c[1]; |
| 76 | x2 = c[2]; |
| 77 | x3 = c[3]; |
| 78 | x4 = k[0]; |
| 79 | x5 = k[1]; |
| 80 | x6 = k[2]; |
| 81 | x7 = k[3]; |
| 82 | x8 = k[4]; |
| 83 | x9 = k[5]; |
| 84 | x10 = k[6]; |
| 85 | x11 = k[7]; |
| 86 | x12 = in[0]; |
| 87 | x13 = in[1]; |
| 88 | x14 = in[2]; |
| 89 | x15 = in[3]; |
| 90 | |
| 91 | for (i = crypto_core_ROUNDS; i > 0; i -= 2) { |
| 92 | QUARTERROUND( x0, x4, x8,x12); |
| 93 | QUARTERROUND( x1, x5, x9,x13); |
| 94 | QUARTERROUND( x2, x6,x10,x14); |
| 95 | QUARTERROUND( x3, x7,x11,x15); |
| 96 | QUARTERROUND( x0, x5,x10,x15); |
| 97 | QUARTERROUND( x1, x6,x11,x12); |
| 98 | QUARTERROUND( x2, x7, x8,x13); |
| 99 | QUARTERROUND( x3, x4, x9,x14); |
| 100 | } |
| 101 | |
| 102 | out[0] = x0 + c[0]; |
| 103 | out[1] = x1 + c[1]; |
| 104 | out[2] = x2 + c[2]; |
| 105 | out[3] = x3 + c[3]; |
| 106 | out[4] = x4 + k[0]; |
| 107 | out[5] = x5 + k[1]; |
| 108 | out[6] = x6 + k[2]; |
| 109 | out[7] = x7 + k[3]; |
| 110 | out[8] = x8 + k[4]; |
| 111 | out[9] = x9 + k[5]; |
| 112 | out[10] = x10 + k[6]; |
| 113 | out[11] = x11 + k[7]; |
| 114 | out[12] = x12 + in[0]; |
| 115 | out[13] = x13 + in[1]; |
| 116 | out[14] = x14 + in[2]; |
| 117 | out[15] = x15 + in[3]; |
| 118 | } |
| 119 | |
| 120 | /* `expand 32-byte k' */ |
| 121 | static const uint32_t crypto_core_constant32[4] = { |
| 122 | 0x61707865U, 0x3320646eU, 0x79622d32U, 0x6b206574U, |
| 123 | }; |
| 124 | |
| 125 | /* |
| 126 | * Test vector for ChaCha20 from |
| 127 | * <http://tools.ietf.org/html/draft-strombergson-chacha-test-vectors-00>, |
| 128 | * test vectors for ChaCha12 and ChaCha8 generated by the same |
| 129 | * crypto_core code with crypto_core_ROUNDS varied. |
| 130 | */ |
| 131 | |
| 132 | #define check(E) do \ |
| 133 | { \ |
| 134 | if (!(E)) \ |
| 135 | panic("crypto self-test failed: %s", #E); \ |
| 136 | } while (0) |
| 137 | |
| 138 | static void |
| 139 | crypto_core_selftest(void) |
| 140 | { |
| 141 | const uint32_t zero32[8] = {0}; |
| 142 | const uint8_t sigma[] = "expand 32-byte k" ; |
| 143 | uint32_t block[16]; |
| 144 | unsigned i; |
| 145 | |
| 146 | #if crypto_core_ROUNDS == 8 |
| 147 | static const uint8_t out[64] = { |
| 148 | 0x3e,0x00,0xef,0x2f,0x89,0x5f,0x40,0xd6, |
| 149 | 0x7f,0x5b,0xb8,0xe8,0x1f,0x09,0xa5,0xa1, |
| 150 | 0x2c,0x84,0x0e,0xc3,0xce,0x9a,0x7f,0x3b, |
| 151 | 0x18,0x1b,0xe1,0x88,0xef,0x71,0x1a,0x1e, |
| 152 | 0x98,0x4c,0xe1,0x72,0xb9,0x21,0x6f,0x41, |
| 153 | 0x9f,0x44,0x53,0x67,0x45,0x6d,0x56,0x19, |
| 154 | 0x31,0x4a,0x42,0xa3,0xda,0x86,0xb0,0x01, |
| 155 | 0x38,0x7b,0xfd,0xb8,0x0e,0x0c,0xfe,0x42, |
| 156 | }; |
| 157 | #elif crypto_core_ROUNDS == 12 |
| 158 | static const uint8_t out[64] = { |
| 159 | 0x9b,0xf4,0x9a,0x6a,0x07,0x55,0xf9,0x53, |
| 160 | 0x81,0x1f,0xce,0x12,0x5f,0x26,0x83,0xd5, |
| 161 | 0x04,0x29,0xc3,0xbb,0x49,0xe0,0x74,0x14, |
| 162 | 0x7e,0x00,0x89,0xa5,0x2e,0xae,0x15,0x5f, |
| 163 | 0x05,0x64,0xf8,0x79,0xd2,0x7a,0xe3,0xc0, |
| 164 | 0x2c,0xe8,0x28,0x34,0xac,0xfa,0x8c,0x79, |
| 165 | 0x3a,0x62,0x9f,0x2c,0xa0,0xde,0x69,0x19, |
| 166 | 0x61,0x0b,0xe8,0x2f,0x41,0x13,0x26,0xbe, |
| 167 | }; |
| 168 | #elif crypto_core_ROUNDS == 20 |
| 169 | static const uint8_t out[64] = { |
| 170 | 0x76,0xb8,0xe0,0xad,0xa0,0xf1,0x3d,0x90, |
| 171 | 0x40,0x5d,0x6a,0xe5,0x53,0x86,0xbd,0x28, |
| 172 | 0xbd,0xd2,0x19,0xb8,0xa0,0x8d,0xed,0x1a, |
| 173 | 0xa8,0x36,0xef,0xcc,0x8b,0x77,0x0d,0xc7, |
| 174 | 0xda,0x41,0x59,0x7c,0x51,0x57,0x48,0x8d, |
| 175 | 0x77,0x24,0xe0,0x3f,0xb8,0xd8,0x4a,0x37, |
| 176 | 0x6a,0x43,0xb8,0xf4,0x15,0x18,0xa1,0x1c, |
| 177 | 0xc3,0x87,0xb6,0x69,0xb2,0xee,0x65,0x86, |
| 178 | }; |
| 179 | #else |
| 180 | #error crypto_core_ROUNDS must be 8, 12, or 20. |
| 181 | #endif |
| 182 | |
| 183 | check(crypto_core_constant32[0] == le32dec(&sigma[0])); |
| 184 | check(crypto_core_constant32[1] == le32dec(&sigma[4])); |
| 185 | check(crypto_core_constant32[2] == le32dec(&sigma[8])); |
| 186 | check(crypto_core_constant32[3] == le32dec(&sigma[12])); |
| 187 | |
| 188 | crypto_core(block, zero32, zero32, crypto_core_constant32); |
| 189 | for (i = 0; i < 16; i++) |
| 190 | check(block[i] == le32dec(&out[i*4])); |
| 191 | } |
| 192 | |
| 193 | #undef check |
| 194 | |
| 195 | #define CPRNG_FAST_SEED_BYTES (crypto_core_KEYWORDS * sizeof(uint32_t)) |
| 196 | |
| 197 | struct cprng_fast { |
| 198 | uint32_t buffer[crypto_core_OUTPUTWORDS]; |
| 199 | uint32_t key[crypto_core_KEYWORDS]; |
| 200 | uint32_t nonce[crypto_core_INPUTWORDS]; |
| 201 | bool have_initial; |
| 202 | }; |
| 203 | |
| 204 | __CTASSERT(sizeof ((struct cprng_fast *)0)->key == CPRNG_FAST_SEED_BYTES); |
| 205 | |
| 206 | static void cprng_fast_init_cpu(void *, void *, struct cpu_info *); |
| 207 | static void cprng_fast_schedule_reseed(struct cprng_fast *); |
| 208 | static void cprng_fast_intr(void *); |
| 209 | |
| 210 | static void cprng_fast_seed(struct cprng_fast *, const void *); |
| 211 | static void cprng_fast_buf(struct cprng_fast *, void *, unsigned); |
| 212 | |
| 213 | static void cprng_fast_buf_short(void *, size_t); |
| 214 | static void cprng_fast_buf_long(void *, size_t); |
| 215 | |
| 216 | static percpu_t *cprng_fast_percpu __read_mostly; |
| 217 | static void *cprng_fast_softint __read_mostly; |
| 218 | |
| 219 | void |
| 220 | cprng_fast_init(void) |
| 221 | { |
| 222 | |
| 223 | crypto_core_selftest(); |
| 224 | cprng_fast_percpu = percpu_alloc(sizeof(struct cprng_fast)); |
| 225 | percpu_foreach(cprng_fast_percpu, &cprng_fast_init_cpu, NULL); |
| 226 | cprng_fast_softint = softint_establish(SOFTINT_SERIAL|SOFTINT_MPSAFE, |
| 227 | &cprng_fast_intr, NULL); |
| 228 | } |
| 229 | |
| 230 | static void |
| 231 | cprng_fast_init_cpu(void *p, void *arg __unused, struct cpu_info *ci __unused) |
| 232 | { |
| 233 | struct cprng_fast *const cprng = p; |
| 234 | uint8_t seed[CPRNG_FAST_SEED_BYTES]; |
| 235 | |
| 236 | cprng_strong(kern_cprng, seed, sizeof seed, 0); |
| 237 | cprng_fast_seed(cprng, seed); |
| 238 | cprng->have_initial = rnd_initial_entropy; |
| 239 | (void)explicit_memset(seed, 0, sizeof seed); |
| 240 | } |
| 241 | |
| 242 | static inline int |
| 243 | cprng_fast_get(struct cprng_fast **cprngp) |
| 244 | { |
| 245 | struct cprng_fast *cprng; |
| 246 | int s; |
| 247 | |
| 248 | *cprngp = cprng = percpu_getref(cprng_fast_percpu); |
| 249 | s = splvm(); |
| 250 | |
| 251 | if (__predict_false(!cprng->have_initial)) |
| 252 | cprng_fast_schedule_reseed(cprng); |
| 253 | |
| 254 | return s; |
| 255 | } |
| 256 | |
| 257 | static inline void |
| 258 | cprng_fast_put(struct cprng_fast *cprng, int s) |
| 259 | { |
| 260 | |
| 261 | KASSERT((cprng == percpu_getref(cprng_fast_percpu)) && |
| 262 | (percpu_putref(cprng_fast_percpu), true)); |
| 263 | splx(s); |
| 264 | percpu_putref(cprng_fast_percpu); |
| 265 | } |
| 266 | |
| 267 | static void |
| 268 | cprng_fast_schedule_reseed(struct cprng_fast *cprng __unused) |
| 269 | { |
| 270 | |
| 271 | softint_schedule(cprng_fast_softint); |
| 272 | } |
| 273 | |
| 274 | static void |
| 275 | cprng_fast_intr(void *cookie __unused) |
| 276 | { |
| 277 | struct cprng_fast *cprng; |
| 278 | uint8_t seed[CPRNG_FAST_SEED_BYTES]; |
| 279 | int s; |
| 280 | |
| 281 | cprng_strong(kern_cprng, seed, sizeof(seed), 0); |
| 282 | |
| 283 | cprng = percpu_getref(cprng_fast_percpu); |
| 284 | s = splvm(); |
| 285 | cprng_fast_seed(cprng, seed); |
| 286 | cprng->have_initial = rnd_initial_entropy; |
| 287 | splx(s); |
| 288 | percpu_putref(cprng_fast_percpu); |
| 289 | |
| 290 | explicit_memset(seed, 0, sizeof(seed)); |
| 291 | } |
| 292 | |
| 293 | /* CPRNG algorithm */ |
| 294 | |
| 295 | /* |
| 296 | * The state consists of a key, the current nonce, and a 64-byte buffer |
| 297 | * of output. Since we fill the buffer only when we need output, and |
| 298 | * eat a 32-bit word at a time, one 32-bit word of the buffer would be |
| 299 | * wasted. Instead, we repurpose it to count the number of entries in |
| 300 | * the buffer remaining, counting from high to low in order to allow |
| 301 | * comparison to zero to detect when we need to refill it. |
| 302 | */ |
| 303 | #define CPRNG_FAST_BUFIDX (crypto_core_OUTPUTWORDS - 1) |
| 304 | |
| 305 | static void |
| 306 | cprng_fast_seed(struct cprng_fast *cprng, const void *seed) |
| 307 | { |
| 308 | |
| 309 | (void)memset(cprng->buffer, 0, sizeof cprng->buffer); |
| 310 | (void)memcpy(cprng->key, seed, sizeof cprng->key); |
| 311 | (void)memset(cprng->nonce, 0, sizeof cprng->nonce); |
| 312 | } |
| 313 | |
| 314 | static inline uint32_t |
| 315 | cprng_fast_word(struct cprng_fast *cprng) |
| 316 | { |
| 317 | uint32_t v; |
| 318 | |
| 319 | if (__predict_true(0 < cprng->buffer[CPRNG_FAST_BUFIDX])) { |
| 320 | v = cprng->buffer[--cprng->buffer[CPRNG_FAST_BUFIDX]]; |
| 321 | } else { |
| 322 | /* If we don't have enough words, refill the buffer. */ |
| 323 | crypto_core(cprng->buffer, cprng->nonce, cprng->key, |
| 324 | crypto_core_constant32); |
| 325 | if (__predict_false(++cprng->nonce[0] == 0)) { |
| 326 | cprng->nonce[1]++; |
| 327 | cprng_fast_schedule_reseed(cprng); |
| 328 | } |
| 329 | v = cprng->buffer[CPRNG_FAST_BUFIDX]; |
| 330 | cprng->buffer[CPRNG_FAST_BUFIDX] = CPRNG_FAST_BUFIDX; |
| 331 | } |
| 332 | |
| 333 | return v; |
| 334 | } |
| 335 | |
| 336 | static inline void |
| 337 | cprng_fast_buf(struct cprng_fast *cprng, void *buf, unsigned n) |
| 338 | { |
| 339 | uint8_t *p = buf; |
| 340 | uint32_t v; |
| 341 | unsigned w, r; |
| 342 | |
| 343 | w = n / sizeof(uint32_t); |
| 344 | while (w--) { |
| 345 | v = cprng_fast_word(cprng); |
| 346 | (void)memcpy(p, &v, 4); |
| 347 | p += 4; |
| 348 | } |
| 349 | |
| 350 | r = n % sizeof(uint32_t); |
| 351 | if (r) { |
| 352 | v = cprng_fast_word(cprng); |
| 353 | while (r--) { |
| 354 | *p++ = (v & 0xff); |
| 355 | v >>= 8; |
| 356 | } |
| 357 | } |
| 358 | } |
| 359 | |
| 360 | /* |
| 361 | * crypto_onetimestream: Expand a short unpredictable one-time seed |
| 362 | * into a long unpredictable output. |
| 363 | */ |
| 364 | static void |
| 365 | crypto_onetimestream(const uint32_t seed[crypto_core_KEYWORDS], void *buf, |
| 366 | size_t n) |
| 367 | { |
| 368 | uint32_t block[crypto_core_OUTPUTWORDS]; |
| 369 | uint32_t nonce[crypto_core_INPUTWORDS] = {0}; |
| 370 | uint8_t *p8; |
| 371 | uint32_t *p32; |
| 372 | size_t ni, nb, nf; |
| 373 | |
| 374 | /* |
| 375 | * Guarantee we can generate up to n bytes. We have |
| 376 | * 2^(32*INPUTWORDS) possible inputs yielding output of |
| 377 | * 4*OUTPUTWORDS*2^(32*INPUTWORDS) bytes. It suffices to |
| 378 | * require that sizeof n > (1/CHAR_BIT) log_2 n be less than |
| 379 | * (1/CHAR_BIT) log_2 of the total output stream length. We |
| 380 | * have |
| 381 | * |
| 382 | * log_2 (4 o 2^(32 i)) = log_2 (4 o) + log_2 2^(32 i) |
| 383 | * = 2 + log_2 o + 32 i. |
| 384 | */ |
| 385 | __CTASSERT(CHAR_BIT*sizeof n <= |
| 386 | (2 + ilog2(crypto_core_OUTPUTWORDS) + 32*crypto_core_INPUTWORDS)); |
| 387 | |
| 388 | p8 = buf; |
| 389 | p32 = (uint32_t *)roundup2((uintptr_t)p8, sizeof(uint32_t)); |
| 390 | ni = (uint8_t *)p32 - p8; |
| 391 | if (n < ni) |
| 392 | ni = n; |
| 393 | nb = (n - ni) / sizeof block; |
| 394 | nf = (n - ni) % sizeof block; |
| 395 | |
| 396 | KASSERT(((uintptr_t)p32 & 3) == 0); |
| 397 | KASSERT(ni <= n); |
| 398 | KASSERT(nb <= (n / sizeof block)); |
| 399 | KASSERT(nf <= n); |
| 400 | KASSERT(n == (ni + (nb * sizeof block) + nf)); |
| 401 | KASSERT(ni < sizeof(uint32_t)); |
| 402 | KASSERT(nf < sizeof block); |
| 403 | |
| 404 | if (ni) { |
| 405 | crypto_core(block, nonce, seed, crypto_core_constant32); |
| 406 | nonce[0]++; |
| 407 | (void)memcpy(p8, block, ni); |
| 408 | } |
| 409 | while (nb--) { |
| 410 | crypto_core(p32, nonce, seed, crypto_core_constant32); |
| 411 | if (++nonce[0] == 0) |
| 412 | nonce[1]++; |
| 413 | p32 += crypto_core_OUTPUTWORDS; |
| 414 | } |
| 415 | if (nf) { |
| 416 | crypto_core(block, nonce, seed, crypto_core_constant32); |
| 417 | if (++nonce[0] == 0) |
| 418 | nonce[1]++; |
| 419 | (void)memcpy(p32, block, nf); |
| 420 | } |
| 421 | |
| 422 | if (ni | nf) |
| 423 | (void)explicit_memset(block, 0, sizeof block); |
| 424 | } |
| 425 | |
| 426 | /* Public API */ |
| 427 | |
| 428 | uint32_t |
| 429 | cprng_fast32(void) |
| 430 | { |
| 431 | struct cprng_fast *cprng; |
| 432 | uint32_t v; |
| 433 | int s; |
| 434 | |
| 435 | s = cprng_fast_get(&cprng); |
| 436 | v = cprng_fast_word(cprng); |
| 437 | cprng_fast_put(cprng, s); |
| 438 | |
| 439 | return v; |
| 440 | } |
| 441 | |
| 442 | uint64_t |
| 443 | cprng_fast64(void) |
| 444 | { |
| 445 | struct cprng_fast *cprng; |
| 446 | uint32_t hi, lo; |
| 447 | int s; |
| 448 | |
| 449 | s = cprng_fast_get(&cprng); |
| 450 | hi = cprng_fast_word(cprng); |
| 451 | lo = cprng_fast_word(cprng); |
| 452 | cprng_fast_put(cprng, s); |
| 453 | |
| 454 | return ((uint64_t)hi << 32) | lo; |
| 455 | } |
| 456 | |
| 457 | static void |
| 458 | cprng_fast_buf_short(void *buf, size_t len) |
| 459 | { |
| 460 | struct cprng_fast *cprng; |
| 461 | int s; |
| 462 | |
| 463 | s = cprng_fast_get(&cprng); |
| 464 | cprng_fast_buf(cprng, buf, len); |
| 465 | cprng_fast_put(cprng, s); |
| 466 | } |
| 467 | |
| 468 | static __noinline void |
| 469 | cprng_fast_buf_long(void *buf, size_t len) |
| 470 | { |
| 471 | uint32_t seed[crypto_core_KEYWORDS]; |
| 472 | struct cprng_fast *cprng; |
| 473 | int s; |
| 474 | |
| 475 | s = cprng_fast_get(&cprng); |
| 476 | cprng_fast_buf(cprng, seed, sizeof seed); |
| 477 | cprng_fast_put(cprng, s); |
| 478 | |
| 479 | crypto_onetimestream(seed, buf, len); |
| 480 | |
| 481 | (void)explicit_memset(seed, 0, sizeof seed); |
| 482 | } |
| 483 | |
| 484 | size_t |
| 485 | cprng_fast(void *buf, size_t len) |
| 486 | { |
| 487 | |
| 488 | /* |
| 489 | * We don't want to hog the CPU, so we use the short version, |
| 490 | * to generate output without preemption, only if we can do it |
| 491 | * with at most one crypto_core. |
| 492 | */ |
| 493 | if (len <= (sizeof(uint32_t) * crypto_core_OUTPUTWORDS)) |
| 494 | cprng_fast_buf_short(buf, len); |
| 495 | else |
| 496 | cprng_fast_buf_long(buf, len); |
| 497 | |
| 498 | return len; |
| 499 | } |
| 500 | |