1 /* 2 This is a maximally equidistributed combined Tausworthe generator 3 based on code from GNU Scientific Library 1.5 (30 Jun 2004) 4 5 lfsr113 version: 6 7 x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n) 8 9 s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13)) 10 s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27)) 11 s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21)) 12 s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12)) 13 14 The period of this generator is about 2^113 (see erratum paper). 15 16 From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe 17 Generators", Mathematics of Computation, 65, 213 (1996), 203--213: 18 http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps 19 ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps 20 21 There is an erratum in the paper "Tables of Maximally 22 Equidistributed Combined LFSR Generators", Mathematics of 23 Computation, 68, 225 (1999), 261--269: 24 http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps 25 26 ... the k_j most significant bits of z_j must be non- 27 zero, for each j. (Note: this restriction also applies to the 28 computer code given in [4], but was mistakenly not mentioned in 29 that paper.) 30 31 This affects the seeding procedure by imposing the requirement 32 s1 > 1, s2 > 7, s3 > 15, s4 > 127. 33 34 */ 35 36 #include <linux/types.h> 37 #include <linux/percpu.h> 38 #include <linux/export.h> 39 #include <linux/jiffies.h> 40 #include <linux/random.h> 41 #include <linux/sched.h> 42 43 #ifdef CONFIG_RANDOM32_SELFTEST 44 static void __init prandom_state_selftest(void); 45 #endif 46 47 static DEFINE_PER_CPU(struct rnd_state, net_rand_state); 48 49 /** 50 * prandom_u32_state - seeded pseudo-random number generator. 51 * @state: pointer to state structure holding seeded state. 52 * 53 * This is used for pseudo-randomness with no outside seeding. 54 * For more random results, use prandom_u32(). 55 */ 56 u32 prandom_u32_state(struct rnd_state *state) 57 { 58 #define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b) 59 60 state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); 61 state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); 62 state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); 63 state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); 64 65 return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); 66 } 67 EXPORT_SYMBOL(prandom_u32_state); 68 69 /** 70 * prandom_u32 - pseudo random number generator 71 * 72 * A 32 bit pseudo-random number is generated using a fast 73 * algorithm suitable for simulation. This algorithm is NOT 74 * considered safe for cryptographic use. 75 */ 76 u32 prandom_u32(void) 77 { 78 unsigned long r; 79 struct rnd_state *state = &get_cpu_var(net_rand_state); 80 r = prandom_u32_state(state); 81 put_cpu_var(state); 82 return r; 83 } 84 EXPORT_SYMBOL(prandom_u32); 85 86 /* 87 * prandom_bytes_state - get the requested number of pseudo-random bytes 88 * 89 * @state: pointer to state structure holding seeded state. 90 * @buf: where to copy the pseudo-random bytes to 91 * @bytes: the requested number of bytes 92 * 93 * This is used for pseudo-randomness with no outside seeding. 94 * For more random results, use prandom_bytes(). 95 */ 96 void prandom_bytes_state(struct rnd_state *state, void *buf, int bytes) 97 { 98 unsigned char *p = buf; 99 int i; 100 101 for (i = 0; i < round_down(bytes, sizeof(u32)); i += sizeof(u32)) { 102 u32 random = prandom_u32_state(state); 103 int j; 104 105 for (j = 0; j < sizeof(u32); j++) { 106 p[i + j] = random; 107 random >>= BITS_PER_BYTE; 108 } 109 } 110 if (i < bytes) { 111 u32 random = prandom_u32_state(state); 112 113 for (; i < bytes; i++) { 114 p[i] = random; 115 random >>= BITS_PER_BYTE; 116 } 117 } 118 } 119 EXPORT_SYMBOL(prandom_bytes_state); 120 121 /** 122 * prandom_bytes - get the requested number of pseudo-random bytes 123 * @buf: where to copy the pseudo-random bytes to 124 * @bytes: the requested number of bytes 125 */ 126 void prandom_bytes(void *buf, int bytes) 127 { 128 struct rnd_state *state = &get_cpu_var(net_rand_state); 129 130 prandom_bytes_state(state, buf, bytes); 131 put_cpu_var(state); 132 } 133 EXPORT_SYMBOL(prandom_bytes); 134 135 static void prandom_warmup(struct rnd_state *state) 136 { 137 /* Calling RNG ten times to satify recurrence condition */ 138 prandom_u32_state(state); 139 prandom_u32_state(state); 140 prandom_u32_state(state); 141 prandom_u32_state(state); 142 prandom_u32_state(state); 143 prandom_u32_state(state); 144 prandom_u32_state(state); 145 prandom_u32_state(state); 146 prandom_u32_state(state); 147 prandom_u32_state(state); 148 } 149 150 static void prandom_seed_very_weak(struct rnd_state *state, u32 seed) 151 { 152 /* Note: This sort of seeding is ONLY used in test cases and 153 * during boot at the time from core_initcall until late_initcall 154 * as we don't have a stronger entropy source available yet. 155 * After late_initcall, we reseed entire state, we have to (!), 156 * otherwise an attacker just needs to search 32 bit space to 157 * probe for our internal 128 bit state if he knows a couple 158 * of prandom32 outputs! 159 */ 160 #define LCG(x) ((x) * 69069U) /* super-duper LCG */ 161 state->s1 = __seed(LCG(seed), 2U); 162 state->s2 = __seed(LCG(state->s1), 8U); 163 state->s3 = __seed(LCG(state->s2), 16U); 164 state->s4 = __seed(LCG(state->s3), 128U); 165 } 166 167 /** 168 * prandom_seed - add entropy to pseudo random number generator 169 * @seed: seed value 170 * 171 * Add some additional seeding to the prandom pool. 172 */ 173 void prandom_seed(u32 entropy) 174 { 175 int i; 176 /* 177 * No locking on the CPUs, but then somewhat random results are, well, 178 * expected. 179 */ 180 for_each_possible_cpu (i) { 181 struct rnd_state *state = &per_cpu(net_rand_state, i); 182 183 state->s1 = __seed(state->s1 ^ entropy, 2U); 184 prandom_warmup(state); 185 } 186 } 187 EXPORT_SYMBOL(prandom_seed); 188 189 /* 190 * Generate some initially weak seeding values to allow 191 * to start the prandom_u32() engine. 192 */ 193 static int __init prandom_init(void) 194 { 195 int i; 196 197 #ifdef CONFIG_RANDOM32_SELFTEST 198 prandom_state_selftest(); 199 #endif 200 201 for_each_possible_cpu(i) { 202 struct rnd_state *state = &per_cpu(net_rand_state,i); 203 204 prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy()); 205 prandom_warmup(state); 206 } 207 return 0; 208 } 209 core_initcall(prandom_init); 210 211 static void __prandom_timer(unsigned long dontcare); 212 static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0); 213 214 static void __prandom_timer(unsigned long dontcare) 215 { 216 u32 entropy; 217 218 get_random_bytes(&entropy, sizeof(entropy)); 219 prandom_seed(entropy); 220 /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ 221 seed_timer.expires = jiffies + (40 * HZ + (prandom_u32() % (40 * HZ))); 222 add_timer(&seed_timer); 223 } 224 225 static void prandom_start_seed_timer(void) 226 { 227 set_timer_slack(&seed_timer, HZ); 228 seed_timer.expires = jiffies + 40 * HZ; 229 add_timer(&seed_timer); 230 } 231 232 /* 233 * Generate better values after random number generator 234 * is fully initialized. 235 */ 236 static void __prandom_reseed(bool late) 237 { 238 int i; 239 unsigned long flags; 240 static bool latch = false; 241 static DEFINE_SPINLOCK(lock); 242 243 /* only allow initial seeding (late == false) once */ 244 spin_lock_irqsave(&lock, flags); 245 if (latch && !late) 246 goto out; 247 latch = true; 248 249 for_each_possible_cpu(i) { 250 struct rnd_state *state = &per_cpu(net_rand_state,i); 251 u32 seeds[4]; 252 253 get_random_bytes(&seeds, sizeof(seeds)); 254 state->s1 = __seed(seeds[0], 2U); 255 state->s2 = __seed(seeds[1], 8U); 256 state->s3 = __seed(seeds[2], 16U); 257 state->s4 = __seed(seeds[3], 128U); 258 259 prandom_warmup(state); 260 } 261 out: 262 spin_unlock_irqrestore(&lock, flags); 263 } 264 265 void prandom_reseed_late(void) 266 { 267 __prandom_reseed(true); 268 } 269 270 static int __init prandom_reseed(void) 271 { 272 __prandom_reseed(false); 273 prandom_start_seed_timer(); 274 return 0; 275 } 276 late_initcall(prandom_reseed); 277 278 #ifdef CONFIG_RANDOM32_SELFTEST 279 static struct prandom_test1 { 280 u32 seed; 281 u32 result; 282 } test1[] = { 283 { 1U, 3484351685U }, 284 { 2U, 2623130059U }, 285 { 3U, 3125133893U }, 286 { 4U, 984847254U }, 287 }; 288 289 static struct prandom_test2 { 290 u32 seed; 291 u32 iteration; 292 u32 result; 293 } test2[] = { 294 /* Test cases against taus113 from GSL library. */ 295 { 931557656U, 959U, 2975593782U }, 296 { 1339693295U, 876U, 3887776532U }, 297 { 1545556285U, 961U, 1615538833U }, 298 { 601730776U, 723U, 1776162651U }, 299 { 1027516047U, 687U, 511983079U }, 300 { 416526298U, 700U, 916156552U }, 301 { 1395522032U, 652U, 2222063676U }, 302 { 366221443U, 617U, 2992857763U }, 303 { 1539836965U, 714U, 3783265725U }, 304 { 556206671U, 994U, 799626459U }, 305 { 684907218U, 799U, 367789491U }, 306 { 2121230701U, 931U, 2115467001U }, 307 { 1668516451U, 644U, 3620590685U }, 308 { 768046066U, 883U, 2034077390U }, 309 { 1989159136U, 833U, 1195767305U }, 310 { 536585145U, 996U, 3577259204U }, 311 { 1008129373U, 642U, 1478080776U }, 312 { 1740775604U, 939U, 1264980372U }, 313 { 1967883163U, 508U, 10734624U }, 314 { 1923019697U, 730U, 3821419629U }, 315 { 442079932U, 560U, 3440032343U }, 316 { 1961302714U, 845U, 841962572U }, 317 { 2030205964U, 962U, 1325144227U }, 318 { 1160407529U, 507U, 240940858U }, 319 { 635482502U, 779U, 4200489746U }, 320 { 1252788931U, 699U, 867195434U }, 321 { 1961817131U, 719U, 668237657U }, 322 { 1071468216U, 983U, 917876630U }, 323 { 1281848367U, 932U, 1003100039U }, 324 { 582537119U, 780U, 1127273778U }, 325 { 1973672777U, 853U, 1071368872U }, 326 { 1896756996U, 762U, 1127851055U }, 327 { 847917054U, 500U, 1717499075U }, 328 { 1240520510U, 951U, 2849576657U }, 329 { 1685071682U, 567U, 1961810396U }, 330 { 1516232129U, 557U, 3173877U }, 331 { 1208118903U, 612U, 1613145022U }, 332 { 1817269927U, 693U, 4279122573U }, 333 { 1510091701U, 717U, 638191229U }, 334 { 365916850U, 807U, 600424314U }, 335 { 399324359U, 702U, 1803598116U }, 336 { 1318480274U, 779U, 2074237022U }, 337 { 697758115U, 840U, 1483639402U }, 338 { 1696507773U, 840U, 577415447U }, 339 { 2081979121U, 981U, 3041486449U }, 340 { 955646687U, 742U, 3846494357U }, 341 { 1250683506U, 749U, 836419859U }, 342 { 595003102U, 534U, 366794109U }, 343 { 47485338U, 558U, 3521120834U }, 344 { 619433479U, 610U, 3991783875U }, 345 { 704096520U, 518U, 4139493852U }, 346 { 1712224984U, 606U, 2393312003U }, 347 { 1318233152U, 922U, 3880361134U }, 348 { 855572992U, 761U, 1472974787U }, 349 { 64721421U, 703U, 683860550U }, 350 { 678931758U, 840U, 380616043U }, 351 { 692711973U, 778U, 1382361947U }, 352 { 677703619U, 530U, 2826914161U }, 353 { 92393223U, 586U, 1522128471U }, 354 { 1222592920U, 743U, 3466726667U }, 355 { 358288986U, 695U, 1091956998U }, 356 { 1935056945U, 958U, 514864477U }, 357 { 735675993U, 990U, 1294239989U }, 358 { 1560089402U, 897U, 2238551287U }, 359 { 70616361U, 829U, 22483098U }, 360 { 368234700U, 731U, 2913875084U }, 361 { 20221190U, 879U, 1564152970U }, 362 { 539444654U, 682U, 1835141259U }, 363 { 1314987297U, 840U, 1801114136U }, 364 { 2019295544U, 645U, 3286438930U }, 365 { 469023838U, 716U, 1637918202U }, 366 { 1843754496U, 653U, 2562092152U }, 367 { 400672036U, 809U, 4264212785U }, 368 { 404722249U, 965U, 2704116999U }, 369 { 600702209U, 758U, 584979986U }, 370 { 519953954U, 667U, 2574436237U }, 371 { 1658071126U, 694U, 2214569490U }, 372 { 420480037U, 749U, 3430010866U }, 373 { 690103647U, 969U, 3700758083U }, 374 { 1029424799U, 937U, 3787746841U }, 375 { 2012608669U, 506U, 3362628973U }, 376 { 1535432887U, 998U, 42610943U }, 377 { 1330635533U, 857U, 3040806504U }, 378 { 1223800550U, 539U, 3954229517U }, 379 { 1322411537U, 680U, 3223250324U }, 380 { 1877847898U, 945U, 2915147143U }, 381 { 1646356099U, 874U, 965988280U }, 382 { 805687536U, 744U, 4032277920U }, 383 { 1948093210U, 633U, 1346597684U }, 384 { 392609744U, 783U, 1636083295U }, 385 { 690241304U, 770U, 1201031298U }, 386 { 1360302965U, 696U, 1665394461U }, 387 { 1220090946U, 780U, 1316922812U }, 388 { 447092251U, 500U, 3438743375U }, 389 { 1613868791U, 592U, 828546883U }, 390 { 523430951U, 548U, 2552392304U }, 391 { 726692899U, 810U, 1656872867U }, 392 { 1364340021U, 836U, 3710513486U }, 393 { 1986257729U, 931U, 935013962U }, 394 { 407983964U, 921U, 728767059U }, 395 }; 396 397 static void __init prandom_state_selftest(void) 398 { 399 int i, j, errors = 0, runs = 0; 400 bool error = false; 401 402 for (i = 0; i < ARRAY_SIZE(test1); i++) { 403 struct rnd_state state; 404 405 prandom_seed_very_weak(&state, test1[i].seed); 406 prandom_warmup(&state); 407 408 if (test1[i].result != prandom_u32_state(&state)) 409 error = true; 410 } 411 412 if (error) 413 pr_warn("prandom: seed boundary self test failed\n"); 414 else 415 pr_info("prandom: seed boundary self test passed\n"); 416 417 for (i = 0; i < ARRAY_SIZE(test2); i++) { 418 struct rnd_state state; 419 420 prandom_seed_very_weak(&state, test2[i].seed); 421 prandom_warmup(&state); 422 423 for (j = 0; j < test2[i].iteration - 1; j++) 424 prandom_u32_state(&state); 425 426 if (test2[i].result != prandom_u32_state(&state)) 427 errors++; 428 429 runs++; 430 cond_resched(); 431 } 432 433 if (errors) 434 pr_warn("prandom: %d/%d self tests failed\n", errors, runs); 435 else 436 pr_info("prandom: %d self tests passed\n", runs); 437 } 438 #endif 439