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Diffstat (limited to 'lib/random32.c')
| -rw-r--r-- | lib/random32.c | 574 |
1 files changed, 574 insertions, 0 deletions
diff --git a/lib/random32.c b/lib/random32.c new file mode 100644 index 000000000..339624191 --- /dev/null +++ b/lib/random32.c @@ -0,0 +1,574 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * 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 <linux/types.h> +#include <linux/percpu.h> +#include <linux/export.h> +#include <linux/jiffies.h> +#include <linux/random.h> +#include <linux/sched.h> +#include <linux/bitops.h> +#include <linux/slab.h> +#include <linux/notifier.h> +#include <asm/unaligned.h> + +/** + * 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) << d) ^ (((s << a) ^ s) >> 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_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, size_t bytes) +{ + u8 *ptr = buf; + + while (bytes >= sizeof(u32)) { + put_unaligned(prandom_u32_state(state), (u32 *) ptr); + ptr += sizeof(u32); + bytes -= sizeof(u32); + } + + if (bytes > 0) { + u32 rem = prandom_u32_state(state); + do { + *ptr++ = (u8) rem; + bytes--; + rem >>= BITS_PER_BYTE; + } while (bytes > 0); + } +} +EXPORT_SYMBOL(prandom_bytes_state); + +static void prandom_warmup(struct rnd_state *state) +{ + /* Calling RNG ten times to satisfy 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); +} + +void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state) +{ + int i; + + for_each_possible_cpu(i) { + struct rnd_state *state = per_cpu_ptr(pcpu_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); + } +} +EXPORT_SYMBOL(prandom_seed_full_state); + +#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 u32 __extract_hwseed(void) +{ + unsigned int val = 0; + + (void)(arch_get_random_seed_int(&val) || + arch_get_random_int(&val)); + + return val; +} + +static void prandom_seed_early(struct rnd_state *state, u32 seed, + bool mix_with_hwseed) +{ +#define LCG(x) ((x) * 69069U) /* super-duper LCG */ +#define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0) + state->s1 = __seed(HWSEED() ^ LCG(seed), 2U); + state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U); + state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U); + state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U); +} + +static int __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_early(&state, test1[i].seed, false); + 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_early(&state, test2[i].seed, false); + 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); + return 0; +} +core_initcall(prandom_state_selftest); +#endif + +/* + * The prandom_u32() implementation is now completely separate from the + * prandom_state() functions, which are retained (for now) for compatibility. + * + * Because of (ab)use in the networking code for choosing random TCP/UDP port + * numbers, which open DoS possibilities if guessable, we want something + * stronger than a standard PRNG. But the performance requirements of + * the network code do not allow robust crypto for this application. + * + * So this is a homebrew Junior Spaceman implementation, based on the + * lowest-latency trustworthy crypto primitive available, SipHash. + * (The authors of SipHash have not been consulted about this abuse of + * their work.) + * + * Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to + * one word of output. This abbreviated version uses 2 rounds per word + * of output. + */ + +struct siprand_state { + unsigned long v0; + unsigned long v1; + unsigned long v2; + unsigned long v3; +}; + +static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy; + +/* + * This is the core CPRNG function. As "pseudorandom", this is not used + * for truly valuable things, just intended to be a PITA to guess. + * For maximum speed, we do just two SipHash rounds per word. This is + * the same rate as 4 rounds per 64 bits that SipHash normally uses, + * so hopefully it's reasonably secure. + * + * There are two changes from the official SipHash finalization: + * - We omit some constants XORed with v2 in the SipHash spec as irrelevant; + * they are there only to make the output rounds distinct from the input + * rounds, and this application has no input rounds. + * - Rather than returning v0^v1^v2^v3, return v1+v3. + * If you look at the SipHash round, the last operation on v3 is + * "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time. + * Likewise "v1 ^= v2". (The rotate of v2 makes a difference, but + * it still cancels out half of the bits in v2 for no benefit.) + * Second, since the last combining operation was xor, continue the + * pattern of alternating xor/add for a tiny bit of extra non-linearity. + */ +static inline u32 siprand_u32(struct siprand_state *s) +{ + unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3; + + PRND_SIPROUND(v0, v1, v2, v3); + PRND_SIPROUND(v0, v1, v2, v3); + s->v0 = v0; s->v1 = v1; s->v2 = v2; s->v3 = v3; + return v1 + v3; +} + + +/** + * 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) +{ + struct siprand_state *state = get_cpu_ptr(&net_rand_state); + u32 res = siprand_u32(state); + + put_cpu_ptr(&net_rand_state); + return res; +} +EXPORT_SYMBOL(prandom_u32); + +/** + * 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, size_t bytes) +{ + struct siprand_state *state = get_cpu_ptr(&net_rand_state); + u8 *ptr = buf; + + while (bytes >= sizeof(u32)) { + put_unaligned(siprand_u32(state), (u32 *)ptr); + ptr += sizeof(u32); + bytes -= sizeof(u32); + } + + if (bytes > 0) { + u32 rem = siprand_u32(state); + + do { + *ptr++ = (u8)rem; + rem >>= BITS_PER_BYTE; + } while (--bytes > 0); + } + put_cpu_ptr(&net_rand_state); +} +EXPORT_SYMBOL(prandom_bytes); + +/** + * prandom_seed - add entropy to pseudo random number generator + * @entropy: entropy value + * + * Add some additional seed material to the prandom pool. + * The "entropy" is actually our IP address (the only caller is + * the network code), not for unpredictability, but to ensure that + * different machines are initialized differently. + */ +void prandom_seed(u32 entropy) +{ + int i; + + add_device_randomness(&entropy, sizeof(entropy)); + + for_each_possible_cpu(i) { + struct siprand_state *state = per_cpu_ptr(&net_rand_state, i); + unsigned long v0 = state->v0, v1 = state->v1; + unsigned long v2 = state->v2, v3 = state->v3; + + do { + v3 ^= entropy; + PRND_SIPROUND(v0, v1, v2, v3); + PRND_SIPROUND(v0, v1, v2, v3); + v0 ^= entropy; + } while (unlikely(!v0 || !v1 || !v2 || !v3)); + + WRITE_ONCE(state->v0, v0); + WRITE_ONCE(state->v1, v1); + WRITE_ONCE(state->v2, v2); + WRITE_ONCE(state->v3, v3); + } +} +EXPORT_SYMBOL(prandom_seed); + +/* + * Generate some initially weak seeding values to allow + * the prandom_u32() engine to be started. + */ +static int __init prandom_init_early(void) +{ + int i; + unsigned long v0, v1, v2, v3; + + if (!arch_get_random_long(&v0)) + v0 = jiffies; + if (!arch_get_random_long(&v1)) + v1 = random_get_entropy(); + v2 = v0 ^ PRND_K0; + v3 = v1 ^ PRND_K1; + + for_each_possible_cpu(i) { + struct siprand_state *state; + + v3 ^= i; + PRND_SIPROUND(v0, v1, v2, v3); + PRND_SIPROUND(v0, v1, v2, v3); + v0 ^= i; + + state = per_cpu_ptr(&net_rand_state, i); + state->v0 = v0; state->v1 = v1; + state->v2 = v2; state->v3 = v3; + } + + return 0; +} +core_initcall(prandom_init_early); + + +/* Stronger reseeding when available, and periodically thereafter. */ +static void prandom_reseed(struct timer_list *unused); + +static DEFINE_TIMER(seed_timer, prandom_reseed); + +static void prandom_reseed(struct timer_list *unused) +{ + unsigned long expires; + int i; + + /* + * Reinitialize each CPU's PRNG with 128 bits of key. + * No locking on the CPUs, but then somewhat random results are, + * well, expected. + */ + for_each_possible_cpu(i) { + struct siprand_state *state; + unsigned long v0 = get_random_long(), v2 = v0 ^ PRND_K0; + unsigned long v1 = get_random_long(), v3 = v1 ^ PRND_K1; +#if BITS_PER_LONG == 32 + int j; + + /* + * On 32-bit machines, hash in two extra words to + * approximate 128-bit key length. Not that the hash + * has that much security, but this prevents a trivial + * 64-bit brute force. + */ + for (j = 0; j < 2; j++) { + unsigned long m = get_random_long(); + + v3 ^= m; + PRND_SIPROUND(v0, v1, v2, v3); + PRND_SIPROUND(v0, v1, v2, v3); + v0 ^= m; + } +#endif + /* + * Probably impossible in practice, but there is a + * theoretical risk that a race between this reseeding + * and the target CPU writing its state back could + * create the all-zero SipHash fixed point. + * + * To ensure that never happens, ensure the state + * we write contains no zero words. + */ + state = per_cpu_ptr(&net_rand_state, i); + WRITE_ONCE(state->v0, v0 ? v0 : -1ul); + WRITE_ONCE(state->v1, v1 ? v1 : -1ul); + WRITE_ONCE(state->v2, v2 ? v2 : -1ul); + WRITE_ONCE(state->v3, v3 ? v3 : -1ul); + } + + /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ + expires = round_jiffies(jiffies + 40 * HZ + prandom_u32_max(40 * HZ)); + mod_timer(&seed_timer, expires); +} + +/* + * The random ready callback can be called from almost any interrupt. + * To avoid worrying about whether it's safe to delay that interrupt + * long enough to seed all CPUs, just schedule an immediate timer event. + */ +static int prandom_timer_start(struct notifier_block *nb, + unsigned long action, void *data) +{ + mod_timer(&seed_timer, jiffies); + return 0; +} + +/* + * Start periodic full reseeding as soon as strong + * random numbers are available. + */ +static int __init prandom_init_late(void) +{ + static struct notifier_block random_ready = { + .notifier_call = prandom_timer_start + }; + int ret = register_random_ready_notifier(&random_ready); + + if (ret == -EALREADY) { + prandom_timer_start(&random_ready, 0, NULL); + ret = 0; + } + return ret; +} +late_initcall(prandom_init_late); |