cprng_fast.c revision 1.17
1 1.17 riastrad /* $NetBSD: cprng_fast.c,v 1.17 2022/06/01 15:44:37 riastradh Exp $ */ 2 1.2 tls 3 1.2 tls /*- 4 1.2 tls * Copyright (c) 2014 The NetBSD Foundation, Inc. 5 1.2 tls * All rights reserved. 6 1.2 tls * 7 1.2 tls * This code is derived from software contributed to The NetBSD Foundation 8 1.2 tls * by Taylor R. Campbell. 9 1.2 tls * 10 1.2 tls * Redistribution and use in source and binary forms, with or without 11 1.2 tls * modification, are permitted provided that the following conditions 12 1.2 tls * are met: 13 1.2 tls * 1. Redistributions of source code must retain the above copyright 14 1.2 tls * notice, this list of conditions and the following disclaimer. 15 1.2 tls * 2. Redistributions in binary form must reproduce the above copyright 16 1.2 tls * notice, this list of conditions and the following disclaimer in the 17 1.2 tls * documentation and/or other materials provided with the distribution. 18 1.2 tls * 19 1.2 tls * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 1.2 tls * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 1.2 tls * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 1.2 tls * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 1.2 tls * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 1.2 tls * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 1.2 tls * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 1.2 tls * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 1.2 tls * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 1.2 tls * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 1.2 tls * POSSIBILITY OF SUCH DAMAGE. 30 1.2 tls */ 31 1.2 tls 32 1.2 tls #include <sys/cdefs.h> 33 1.17 riastrad __KERNEL_RCSID(0, "$NetBSD: cprng_fast.c,v 1.17 2022/06/01 15:44:37 riastradh Exp $"); 34 1.2 tls 35 1.2 tls #include <sys/types.h> 36 1.4 riastrad #include <sys/param.h> 37 1.2 tls #include <sys/bitops.h> 38 1.4 riastrad #include <sys/cprng.h> 39 1.2 tls #include <sys/cpu.h> 40 1.14 riastrad #include <sys/entropy.h> 41 1.15 riastrad #include <sys/evcnt.h> 42 1.15 riastrad #include <sys/kmem.h> 43 1.2 tls #include <sys/percpu.h> 44 1.2 tls 45 1.16 riastrad #include <crypto/chacha/chacha.h> 46 1.2 tls 47 1.16 riastrad #define CPRNG_FAST_SEED_BYTES CHACHA_STREAM_KEYBYTES 49 1.2 tls 50 1.16 riastrad struct cprng_fast { 51 1.16 riastrad /* 128-bit vector unit generates 256 bytes at once */ 52 1.16 riastrad uint8_t buf[256]; 53 1.16 riastrad uint8_t key[CPRNG_FAST_SEED_BYTES]; 54 1.16 riastrad uint8_t nonce[CHACHA_STREAM_NONCEBYTES]; 55 1.15 riastrad unsigned i; 56 1.14 riastrad struct evcnt *reseed_evcnt; 57 1.2 tls unsigned epoch; 58 1.2 tls }; 59 1.8 riastrad 60 1.17 riastrad static void cprng_fast_init_cpu(void *, void *, struct cpu_info *); 61 1.2 tls static void cprng_fast_reseed(struct cprng_fast *); 62 1.6 riastrad 63 1.2 tls static void cprng_fast_seed(struct cprng_fast *, const void *); 64 1.2 tls static void cprng_fast_buf(struct cprng_fast *, void *, unsigned); 65 1.2 tls 66 1.2 tls static void cprng_fast_buf_short(void *, size_t); 67 1.2 tls static void cprng_fast_buf_long(void *, size_t); 68 1.2 tls 69 1.2 tls static percpu_t *cprng_fast_percpu __read_mostly; 70 1.2 tls 71 1.2 tls void 72 1.2 tls cprng_fast_init(void) 73 1.2 tls { 74 1.15 riastrad 75 1.15 riastrad cprng_fast_percpu = percpu_create(sizeof(struct cprng_fast), 76 1.2 tls cprng_fast_init_cpu, NULL, NULL); 77 1.2 tls } 78 1.8 riastrad 79 1.15 riastrad static void 80 1.8 riastrad cprng_fast_init_cpu(void *p, void *arg __unused, struct cpu_info *ci) 81 1.8 riastrad { 82 1.8 riastrad struct cprng_fast *const cprng = p; 83 1.17 riastrad 84 1.15 riastrad cprng->epoch = 0; 85 1.15 riastrad 86 1.15 riastrad cprng->reseed_evcnt = kmem_alloc(sizeof(*cprng->reseed_evcnt), 87 1.15 riastrad KM_SLEEP); 88 1.15 riastrad evcnt_attach_dynamic(cprng->reseed_evcnt, EVCNT_TYPE_MISC, NULL, 89 1.8 riastrad ci->ci_cpuname, "cprng_fast reseed"); 90 1.9 riastrad } 91 1.16 riastrad 92 1.2 tls static int 94 1.9 riastrad cprng_fast_get(struct cprng_fast **cprngp) 95 1.9 riastrad { 96 1.9 riastrad struct cprng_fast *cprng; 97 1.17 riastrad int s; 98 1.17 riastrad 99 1.9 riastrad KASSERT(!cpu_intr_p()); 100 1.17 riastrad 101 1.2 tls *cprngp = cprng = percpu_getref(cprng_fast_percpu); 102 1.17 riastrad s = splsoftserial(); 103 1.17 riastrad 104 1.17 riastrad if (__predict_false(cprng->epoch != entropy_epoch())) { 105 1.17 riastrad splx(s); 106 1.17 riastrad cprng_fast_reseed(cprng); 107 1.9 riastrad s = splsoftserial(); 108 1.9 riastrad } 109 1.2 tls 110 1.2 tls return s; 111 1.16 riastrad } 112 1.2 tls 113 1.2 tls static void 114 1.2 tls cprng_fast_put(struct cprng_fast *cprng, int s) 115 1.2 tls { 116 1.2 tls 117 1.2 tls KASSERT((cprng == percpu_getref(cprng_fast_percpu)) && 118 1.2 tls (percpu_putref(cprng_fast_percpu), true)); 119 1.2 tls splx(s); 120 1.9 riastrad percpu_putref(cprng_fast_percpu); 121 1.11 justin } 122 1.17 riastrad 123 1.2 tls static void 124 1.14 riastrad cprng_fast_reseed(struct cprng_fast *cprng) 125 1.2 tls { 126 1.7 riastrad unsigned epoch = entropy_epoch(); 127 1.2 tls uint8_t seed[CPRNG_FAST_SEED_BYTES]; 128 1.12 riastrad int s; 129 1.2 tls 130 1.17 riastrad cprng_strong(kern_cprng, seed, sizeof(seed), 0); 131 1.2 tls 132 1.14 riastrad s = splsoftserial(); 133 1.15 riastrad cprng_fast_seed(cprng, seed); 134 1.7 riastrad cprng->epoch = epoch; 135 1.2 tls cprng->reseed_evcnt->ev_count++; 136 1.2 tls splx(s); 137 1.2 tls 138 1.2 tls explicit_memset(seed, 0, sizeof(seed)); 139 1.2 tls } 140 1.2 tls 141 1.6 riastrad /* CPRNG algorithm */ 143 1.2 tls 144 1.2 tls static void 145 1.16 riastrad cprng_fast_seed(struct cprng_fast *cprng, const void *seed) 146 1.2 tls { 147 1.2 tls 148 1.16 riastrad (void)memset(cprng->buf, 0, sizeof cprng->buf); 149 1.2 tls (void)memcpy(cprng->key, seed, sizeof cprng->key); 150 1.2 tls (void)memset(cprng->nonce, 0, sizeof cprng->nonce); 151 1.16 riastrad cprng->i = sizeof cprng->buf; 152 1.16 riastrad } 153 1.2 tls 154 1.16 riastrad static void 155 1.16 riastrad cprng_fast_buf(struct cprng_fast *cprng, void *buf, unsigned len) 156 1.16 riastrad { 157 1.16 riastrad uint8_t *p = buf; 158 1.16 riastrad unsigned n = len, n0; 159 1.2 tls 160 1.16 riastrad KASSERT(cprng->i <= sizeof(cprng->buf)); 161 1.16 riastrad KASSERT(len <= sizeof(cprng->buf)); 162 1.16 riastrad 163 1.16 riastrad n0 = MIN(n, sizeof(cprng->buf) - cprng->i); 164 1.16 riastrad memcpy(p, &cprng->buf[cprng->i], n0); 165 1.16 riastrad if ((n -= n0) == 0) { 166 1.2 tls cprng->i += n0; 167 1.16 riastrad KASSERT(cprng->i <= sizeof(cprng->buf)); 168 1.16 riastrad return; 169 1.16 riastrad } 170 1.16 riastrad p += n0; 171 1.16 riastrad le64enc(cprng->nonce, 1 + le64dec(cprng->nonce)); 172 1.16 riastrad chacha_stream(cprng->buf, sizeof(cprng->buf), 0, cprng->nonce, 173 1.2 tls cprng->key, 8); 174 1.16 riastrad memcpy(p, cprng->buf, n); 175 1.16 riastrad cprng->i = n; 176 1.2 tls } 177 1.16 riastrad 178 1.16 riastrad /* Public API */ 180 1.16 riastrad 181 1.16 riastrad static void 182 1.2 tls cprng_fast_buf_short(void *buf, size_t len) 183 1.16 riastrad { 184 1.10 riastrad struct cprng_fast *cprng; 185 1.16 riastrad int s; 186 1.16 riastrad 187 1.16 riastrad KASSERT(len <= sizeof(cprng->buf)); 188 1.2 tls 189 1.16 riastrad s = cprng_fast_get(&cprng); 190 1.2 tls cprng_fast_buf(cprng, buf, len); 191 1.16 riastrad cprng_fast_put(cprng, s); 192 1.2 tls } 193 1.16 riastrad 194 1.16 riastrad static void 195 1.2 tls cprng_fast_buf_long(void *buf, size_t len) 196 1.16 riastrad { 197 1.16 riastrad uint8_t seed[CHACHA_STREAM_KEYBYTES]; 198 1.16 riastrad uint8_t nonce[CHACHA_STREAM_NONCEBYTES] = {0}; 199 1.16 riastrad 200 1.16 riastrad CTASSERT(sizeof(seed) <= sizeof(((struct cprng_fast *)0)->buf)); 201 1.16 riastrad 202 1.2 tls #if SIZE_MAX >= 0x3fffffffff 203 1.16 riastrad /* >=256 GB is not reasonable */ 204 1.16 riastrad KASSERT(len <= 0x3fffffffff); 205 1.2 tls #endif 206 1.16 riastrad 207 1.2 tls cprng_fast_buf_short(seed, sizeof seed); 208 1.2 tls chacha_stream(buf, len, 0, nonce, seed, 8); 209 1.2 tls 210 1.2 tls (void)explicit_memset(seed, 0, sizeof seed); 211 1.2 tls } 212 1.2 tls 213 1.2 tls uint32_t 214 1.16 riastrad cprng_fast32(void) 215 1.2 tls { 216 1.2 tls uint32_t v; 217 1.2 tls 218 1.2 tls cprng_fast_buf_short(&v, sizeof v); 219 1.2 tls 220 1.2 tls return v; 221 1.2 tls } 222 1.16 riastrad 223 1.2 tls uint64_t 224 1.16 riastrad cprng_fast64(void) 225 1.2 tls { 226 1.16 riastrad uint64_t v; 227 1.2 tls 228 1.2 tls cprng_fast_buf_short(&v, sizeof v); 229 1.2 tls 230 1.2 tls return v; 231 1.2 tls } 232 1.2 tls 233 1.2 tls size_t 234 1.2 tls cprng_fast(void *buf, size_t len) 235 1.2 tls { 236 1.16 riastrad 237 1.2 tls /* 238 1.16 riastrad * We don't want to hog the CPU, so we use the short version, 239 1.2 tls * to generate output without preemption, only if we can do it 240 1.2 tls * with at most one ChaCha call. 241 1.2 tls */ 242 1.2 tls if (len <= sizeof(((struct cprng_fast *)0)->buf)) 243 1.16 riastrad cprng_fast_buf_short(buf, len); 244 1.2 tls else 245 cprng_fast_buf_long(buf, len); 246 247 return len; /* hysterical raisins */ 248 } 249
Indexes created Tue Sep 30 20:09:53 GMT 2025