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 /* This is a maximally equidistributed combined Tausworthe generator based on code from GNU Scientific Library 1.5 (30 Jun 2004) lfsr113 version: x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n) s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13)) s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27)) s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21)) s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12)) The period of this generator is about 2^113 (see erratum paper). From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe Generators", Mathematics of Computation, 65, 213 (1996), 203--213: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps There is an erratum in the paper "Tables of Maximally Equidistributed Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999), 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps ... the k_j most significant bits of z_j must be non- zero, for each j. (Note: this restriction also applies to the computer code given in [4], but was mistakenly not mentioned in that paper.) This affects the seeding procedure by imposing the requirement s1 > 1, s2 > 7, s3 > 15, s4 > 127. */ #include #include #include #include #include #include #ifdef CONFIG_RANDOM32_SELFTEST static void __init prandom_state_selftest(void); #endif static DEFINE_PER_CPU(struct rnd_state, net_rand_state); /** * prandom_u32_state - seeded pseudo-random number generator. * @state: pointer to state structure holding seeded state. * * This is used for pseudo-randomness with no outside seeding. * For more random results, use prandom_u32(). */ u32 prandom_u32_state(struct rnd_state *state) { #define TAUSWORTHE(s,a,b,c,d) ((s&c)<>b) state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); } EXPORT_SYMBOL(prandom_u32_state); /** * prandom_u32 - pseudo random number generator * * A 32 bit pseudo-random number is generated using a fast * algorithm suitable for simulation. This algorithm is NOT * considered safe for cryptographic use. */ u32 prandom_u32(void) { unsigned long r; struct rnd_state *state = &get_cpu_var(net_rand_state); r = prandom_u32_state(state); put_cpu_var(state); return r; } EXPORT_SYMBOL(prandom_u32); /* * prandom_bytes_state - get the requested number of pseudo-random bytes * * @state: pointer to state structure holding seeded state. * @buf: where to copy the pseudo-random bytes to * @bytes: the requested number of bytes * * This is used for pseudo-randomness with no outside seeding. * For more random results, use prandom_bytes(). */ void prandom_bytes_state(struct rnd_state *state, void *buf, int bytes) { unsigned char *p = buf; int i; for (i = 0; i < round_down(bytes, sizeof(u32)); i += sizeof(u32)) { u32 random = prandom_u32_state(state); int j; for (j = 0; j < sizeof(u32); j++) { p[i + j] = random; random >>= BITS_PER_BYTE; } } if (i < bytes) { u32 random = prandom_u32_state(state); for (; i < bytes; i++) { p[i] = random; random >>= BITS_PER_BYTE; } } } EXPORT_SYMBOL(prandom_bytes_state); /** * prandom_bytes - get the requested number of pseudo-random bytes * @buf: where to copy the pseudo-random bytes to * @bytes: the requested number of bytes */ void prandom_bytes(void *buf, int bytes) { struct rnd_state *state = &get_cpu_var(net_rand_state); prandom_bytes_state(state, buf, bytes); put_cpu_var(state); } EXPORT_SYMBOL(prandom_bytes); static void prandom_warmup(struct rnd_state *state) { /* Calling RNG ten times to satify recurrence condition */ prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); prandom_u32_state(state); } static void prandom_seed_very_weak(struct rnd_state *state, u32 seed) { /* Note: This sort of seeding is ONLY used in test cases and * during boot at the time from core_initcall until late_initcall * as we don't have a stronger entropy source available yet. * After late_initcall, we reseed entire state, we have to (!), * otherwise an attacker just needs to search 32 bit space to * probe for our internal 128 bit state if he knows a couple * of prandom32 outputs! */ #define LCG(x) ((x) * 69069U) /* super-duper LCG */ state->s1 = __seed(LCG(seed), 2U); state->s2 = __seed(LCG(state->s1), 8U); state->s3 = __seed(LCG(state->s2), 16U); state->s4 = __seed(LCG(state->s3), 128U); } /** * prandom_seed - add entropy to pseudo random number generator * @seed: seed value * * Add some additional seeding to the prandom pool. */ void prandom_seed(u32 entropy) { int i; /* * No locking on the CPUs, but then somewhat random results are, well, * expected. */ for_each_possible_cpu (i) { struct rnd_state *state = &per_cpu(net_rand_state, i); state->s1 = __seed(state->s1 ^ entropy, 2U); prandom_warmup(state); } } EXPORT_SYMBOL(prandom_seed); /* * Generate some initially weak seeding values to allow * to start the prandom_u32() engine. */ static int __init prandom_init(void) { int i; #ifdef CONFIG_RANDOM32_SELFTEST prandom_state_selftest(); #endif for_each_possible_cpu(i) { struct rnd_state *state = &per_cpu(net_rand_state,i); prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy()); prandom_warmup(state); } return 0; } core_initcall(prandom_init); static void __prandom_timer(unsigned long dontcare); static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0); static void __prandom_timer(unsigned long dontcare) { u32 entropy; unsigned long expires; get_random_bytes(&entropy, sizeof(entropy)); prandom_seed(entropy); /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ expires = 40 + (prandom_u32() % 40); seed_timer.expires = jiffies + msecs_to_jiffies(expires * MSEC_PER_SEC); add_timer(&seed_timer); } static void __init __prandom_start_seed_timer(void) { set_timer_slack(&seed_timer, HZ); seed_timer.expires = jiffies + msecs_to_jiffies(40 * MSEC_PER_SEC); add_timer(&seed_timer); } /* * Generate better values after random number generator * is fully initialized. */ static void __prandom_reseed(bool late) { int i; unsigned long flags; static bool latch = false; static DEFINE_SPINLOCK(lock); /* Asking for random bytes might result in bytes getting * moved into the nonblocking pool and thus marking it * as initialized. In this case we would double back into * this function and attempt to do a late reseed. * Ignore the pointless attempt to reseed again if we're * already waiting for bytes when the nonblocking pool * got initialized. */ /* only allow initial seeding (late == false) once */ if (!spin_trylock_irqsave(&lock, flags)) return; if (latch && !late) goto out; latch = true; for_each_possible_cpu(i) { struct rnd_state *state = &per_cpu(net_rand_state,i); u32 seeds[4]; get_random_bytes(&seeds, sizeof(seeds)); state->s1 = __seed(seeds[0], 2U); state->s2 = __seed(seeds[1], 8U); state->s3 = __seed(seeds[2], 16U); state->s4 = __seed(seeds[3], 128U); prandom_warmup(state); } out: spin_unlock_irqrestore(&lock, flags); } void prandom_reseed_late(void) { __prandom_reseed(true); } static int __init prandom_reseed(void) { __prandom_reseed(false); __prandom_start_seed_timer(); return 0; } late_initcall(prandom_reseed); #ifdef CONFIG_RANDOM32_SELFTEST static struct prandom_test1 { u32 seed; u32 result; } test1[] = { { 1U, 3484351685U }, { 2U, 2623130059U }, { 3U, 3125133893U }, { 4U, 984847254U }, }; static struct prandom_test2 { u32 seed; u32 iteration; u32 result; } test2[] = { /* Test cases against taus113 from GSL library. */ { 931557656U, 959U, 2975593782U }, { 1339693295U, 876U, 3887776532U }, { 1545556285U, 961U, 1615538833U }, { 601730776U, 723U, 1776162651U }, { 1027516047U, 687U, 511983079U }, { 416526298U, 700U, 916156552U }, { 1395522032U, 652U, 2222063676U }, { 366221443U, 617U, 2992857763U }, { 1539836965U, 714U, 3783265725U }, { 556206671U, 994U, 799626459U }, { 684907218U, 799U, 367789491U }, { 2121230701U, 931U, 2115467001U }, { 1668516451U, 644U, 3620590685U }, { 768046066U, 883U, 2034077390U }, { 1989159136U, 833U, 1195767305U }, { 536585145U, 996U, 3577259204U }, { 1008129373U, 642U, 1478080776U }, { 1740775604U, 939U, 1264980372U }, { 1967883163U, 508U, 10734624U }, { 1923019697U, 730U, 3821419629U }, { 442079932U, 560U, 3440032343U }, { 1961302714U, 845U, 841962572U }, { 2030205964U, 962U, 1325144227U }, { 1160407529U, 507U, 240940858U }, { 635482502U, 779U, 4200489746U }, { 1252788931U, 699U, 867195434U }, { 1961817131U, 719U, 668237657U }, { 1071468216U, 983U, 917876630U }, { 1281848367U, 932U, 1003100039U }, { 582537119U, 780U, 1127273778U }, { 1973672777U, 853U, 1071368872U }, { 1896756996U, 762U, 1127851055U }, { 847917054U, 500U, 1717499075U }, { 1240520510U, 951U, 2849576657U }, { 1685071682U, 567U, 1961810396U }, { 1516232129U, 557U, 3173877U }, { 1208118903U, 612U, 1613145022U }, { 1817269927U, 693U, 4279122573U }, { 1510091701U, 717U, 638191229U }, { 365916850U, 807U, 600424314U }, { 399324359U, 702U, 1803598116U }, { 1318480274U, 779U, 2074237022U }, { 697758115U, 840U, 1483639402U }, { 1696507773U, 840U, 577415447U }, { 2081979121U, 981U, 3041486449U }, { 955646687U, 742U, 3846494357U }, { 1250683506U, 749U, 836419859U }, { 595003102U, 534U, 366794109U }, { 47485338U, 558U, 3521120834U }, { 619433479U, 610U, 3991783875U }, { 704096520U, 518U, 4139493852U }, { 1712224984U, 606U, 2393312003U }, { 1318233152U, 922U, 3880361134U }, { 855572992U, 761U, 1472974787U }, { 64721421U, 703U, 683860550U }, { 678931758U, 840U, 380616043U }, { 692711973U, 778U, 1382361947U }, { 677703619U, 530U, 2826914161U }, { 92393223U, 586U, 1522128471U }, { 1222592920U, 743U, 3466726667U }, { 358288986U, 695U, 1091956998U }, { 1935056945U, 958U, 514864477U }, { 735675993U, 990U, 1294239989U }, { 1560089402U, 897U, 2238551287U }, { 70616361U, 829U, 22483098U }, { 368234700U, 731U, 2913875084U }, { 20221190U, 879U, 1564152970U }, { 539444654U, 682U, 1835141259U }, { 1314987297U, 840U, 1801114136U }, { 2019295544U, 645U, 3286438930U }, { 469023838U, 716U, 1637918202U }, { 1843754496U, 653U, 2562092152U }, { 400672036U, 809U, 4264212785U }, { 404722249U, 965U, 2704116999U }, { 600702209U, 758U, 584979986U }, { 519953954U, 667U, 2574436237U }, { 1658071126U, 694U, 2214569490U }, { 420480037U, 749U, 3430010866U }, { 690103647U, 969U, 3700758083U }, { 1029424799U, 937U, 3787746841U }, { 2012608669U, 506U, 3362628973U }, { 1535432887U, 998U, 42610943U }, { 1330635533U, 857U, 3040806504U }, { 1223800550U, 539U, 3954229517U }, { 1322411537U, 680U, 3223250324U }, { 1877847898U, 945U, 2915147143U }, { 1646356099U, 874U, 965988280U }, { 805687536U, 744U, 4032277920U }, { 1948093210U, 633U, 1346597684U }, { 392609744U, 783U, 1636083295U }, { 690241304U, 770U, 1201031298U }, { 1360302965U, 696U, 1665394461U }, { 1220090946U, 780U, 1316922812U }, { 447092251U, 500U, 3438743375U }, { 1613868791U, 592U, 828546883U }, { 523430951U, 548U, 2552392304U }, { 726692899U, 810U, 1656872867U }, { 1364340021U, 836U, 3710513486U }, { 1986257729U, 931U, 935013962U }, { 407983964U, 921U, 728767059U }, }; static void __init prandom_state_selftest(void) { int i, j, errors = 0, runs = 0; bool error = false; for (i = 0; i < ARRAY_SIZE(test1); i++) { struct rnd_state state; prandom_seed_very_weak(&state, test1[i].seed); prandom_warmup(&state); if (test1[i].result != prandom_u32_state(&state)) error = true; } if (error) pr_warn("prandom: seed boundary self test failed\n"); else pr_info("prandom: seed boundary self test passed\n"); for (i = 0; i < ARRAY_SIZE(test2); i++) { struct rnd_state state; prandom_seed_very_weak(&state, test2[i].seed); prandom_warmup(&state); for (j = 0; j < test2[i].iteration - 1; j++) prandom_u32_state(&state); if (test2[i].result != prandom_u32_state(&state)) errors++; runs++; cond_resched(); } if (errors) pr_warn("prandom: %d/%d self tests failed\n", errors, runs); else pr_info("prandom: %d self tests passed\n", runs); } #endif