570 lines
17 KiB
C
570 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* This is a maximally equidistributed combined Tausworthe generator
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* based on code from GNU Scientific Library 1.5 (30 Jun 2004)
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*
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* lfsr113 version:
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*
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* x_n = (s1_n ^ s2_n ^ s3_n ^ s4_n)
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*
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* s1_{n+1} = (((s1_n & 4294967294) << 18) ^ (((s1_n << 6) ^ s1_n) >> 13))
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* s2_{n+1} = (((s2_n & 4294967288) << 2) ^ (((s2_n << 2) ^ s2_n) >> 27))
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* s3_{n+1} = (((s3_n & 4294967280) << 7) ^ (((s3_n << 13) ^ s3_n) >> 21))
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* s4_{n+1} = (((s4_n & 4294967168) << 13) ^ (((s4_n << 3) ^ s4_n) >> 12))
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*
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* The period of this generator is about 2^113 (see erratum paper).
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*
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* From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
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* Generators", Mathematics of Computation, 65, 213 (1996), 203--213:
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* http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
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* ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
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*
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* There is an erratum in the paper "Tables of Maximally Equidistributed
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* Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999),
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* 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps
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*
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* ... the k_j most significant bits of z_j must be non-zero,
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* for each j. (Note: this restriction also applies to the
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* computer code given in [4], but was mistakenly not mentioned
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* in that paper.)
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*
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* This affects the seeding procedure by imposing the requirement
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* s1 > 1, s2 > 7, s3 > 15, s4 > 127.
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*/
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#include <linux/types.h>
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#include <linux/percpu.h>
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#include <linux/export.h>
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#include <linux/jiffies.h>
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#include <linux/random.h>
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#include <linux/sched.h>
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#include <asm/unaligned.h>
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/**
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* prandom_u32_state - seeded pseudo-random number generator.
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* @state: pointer to state structure holding seeded state.
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*
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* This is used for pseudo-randomness with no outside seeding.
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* For more random results, use prandom_u32().
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*/
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u32 prandom_u32_state(struct rnd_state *state)
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{
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#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b)
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state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U);
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state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U);
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state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U);
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state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U);
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return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4);
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}
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EXPORT_SYMBOL(prandom_u32_state);
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/**
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* prandom_bytes_state - get the requested number of pseudo-random bytes
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*
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* @state: pointer to state structure holding seeded state.
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* @buf: where to copy the pseudo-random bytes to
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* @bytes: the requested number of bytes
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*
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* This is used for pseudo-randomness with no outside seeding.
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* For more random results, use prandom_bytes().
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*/
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void prandom_bytes_state(struct rnd_state *state, void *buf, size_t bytes)
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{
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u8 *ptr = buf;
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while (bytes >= sizeof(u32)) {
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put_unaligned(prandom_u32_state(state), (u32 *) ptr);
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ptr += sizeof(u32);
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bytes -= sizeof(u32);
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}
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if (bytes > 0) {
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u32 rem = prandom_u32_state(state);
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do {
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*ptr++ = (u8) rem;
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bytes--;
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rem >>= BITS_PER_BYTE;
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} while (bytes > 0);
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}
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}
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EXPORT_SYMBOL(prandom_bytes_state);
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static void prandom_warmup(struct rnd_state *state)
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{
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/* Calling RNG ten times to satisfy recurrence condition */
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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prandom_u32_state(state);
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}
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void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state)
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{
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int i;
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for_each_possible_cpu(i) {
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struct rnd_state *state = per_cpu_ptr(pcpu_state, i);
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u32 seeds[4];
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get_random_bytes(&seeds, sizeof(seeds));
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state->s1 = __seed(seeds[0], 2U);
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state->s2 = __seed(seeds[1], 8U);
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state->s3 = __seed(seeds[2], 16U);
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state->s4 = __seed(seeds[3], 128U);
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prandom_warmup(state);
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}
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}
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EXPORT_SYMBOL(prandom_seed_full_state);
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#ifdef CONFIG_RANDOM32_SELFTEST
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static struct prandom_test1 {
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u32 seed;
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u32 result;
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} test1[] = {
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{ 1U, 3484351685U },
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{ 2U, 2623130059U },
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{ 3U, 3125133893U },
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{ 4U, 984847254U },
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};
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static struct prandom_test2 {
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u32 seed;
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u32 iteration;
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u32 result;
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} test2[] = {
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/* Test cases against taus113 from GSL library. */
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{ 931557656U, 959U, 2975593782U },
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{ 1339693295U, 876U, 3887776532U },
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{ 1545556285U, 961U, 1615538833U },
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{ 601730776U, 723U, 1776162651U },
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{ 1027516047U, 687U, 511983079U },
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{ 416526298U, 700U, 916156552U },
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{ 1395522032U, 652U, 2222063676U },
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{ 366221443U, 617U, 2992857763U },
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{ 1539836965U, 714U, 3783265725U },
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{ 556206671U, 994U, 799626459U },
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{ 684907218U, 799U, 367789491U },
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{ 2121230701U, 931U, 2115467001U },
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{ 1668516451U, 644U, 3620590685U },
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{ 768046066U, 883U, 2034077390U },
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{ 1989159136U, 833U, 1195767305U },
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{ 536585145U, 996U, 3577259204U },
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{ 1008129373U, 642U, 1478080776U },
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{ 1740775604U, 939U, 1264980372U },
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{ 1967883163U, 508U, 10734624U },
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{ 1923019697U, 730U, 3821419629U },
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{ 442079932U, 560U, 3440032343U },
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{ 1961302714U, 845U, 841962572U },
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{ 2030205964U, 962U, 1325144227U },
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{ 1160407529U, 507U, 240940858U },
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{ 635482502U, 779U, 4200489746U },
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{ 1252788931U, 699U, 867195434U },
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{ 1961817131U, 719U, 668237657U },
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{ 1071468216U, 983U, 917876630U },
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{ 1281848367U, 932U, 1003100039U },
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{ 582537119U, 780U, 1127273778U },
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{ 1973672777U, 853U, 1071368872U },
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{ 1896756996U, 762U, 1127851055U },
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{ 847917054U, 500U, 1717499075U },
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{ 1240520510U, 951U, 2849576657U },
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{ 1685071682U, 567U, 1961810396U },
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{ 1516232129U, 557U, 3173877U },
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{ 1208118903U, 612U, 1613145022U },
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{ 1817269927U, 693U, 4279122573U },
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{ 1510091701U, 717U, 638191229U },
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{ 365916850U, 807U, 600424314U },
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{ 399324359U, 702U, 1803598116U },
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{ 1318480274U, 779U, 2074237022U },
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{ 697758115U, 840U, 1483639402U },
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{ 1696507773U, 840U, 577415447U },
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{ 2081979121U, 981U, 3041486449U },
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{ 955646687U, 742U, 3846494357U },
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{ 1250683506U, 749U, 836419859U },
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{ 595003102U, 534U, 366794109U },
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{ 47485338U, 558U, 3521120834U },
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{ 619433479U, 610U, 3991783875U },
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{ 704096520U, 518U, 4139493852U },
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{ 1712224984U, 606U, 2393312003U },
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{ 1318233152U, 922U, 3880361134U },
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{ 855572992U, 761U, 1472974787U },
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{ 64721421U, 703U, 683860550U },
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{ 678931758U, 840U, 380616043U },
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{ 692711973U, 778U, 1382361947U },
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{ 677703619U, 530U, 2826914161U },
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{ 92393223U, 586U, 1522128471U },
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{ 1222592920U, 743U, 3466726667U },
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{ 358288986U, 695U, 1091956998U },
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{ 1935056945U, 958U, 514864477U },
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{ 735675993U, 990U, 1294239989U },
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{ 1560089402U, 897U, 2238551287U },
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{ 70616361U, 829U, 22483098U },
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{ 368234700U, 731U, 2913875084U },
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{ 20221190U, 879U, 1564152970U },
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{ 539444654U, 682U, 1835141259U },
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{ 1314987297U, 840U, 1801114136U },
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{ 2019295544U, 645U, 3286438930U },
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{ 469023838U, 716U, 1637918202U },
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{ 1843754496U, 653U, 2562092152U },
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{ 400672036U, 809U, 4264212785U },
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{ 404722249U, 965U, 2704116999U },
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{ 600702209U, 758U, 584979986U },
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{ 519953954U, 667U, 2574436237U },
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{ 1658071126U, 694U, 2214569490U },
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{ 420480037U, 749U, 3430010866U },
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{ 690103647U, 969U, 3700758083U },
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{ 1029424799U, 937U, 3787746841U },
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{ 2012608669U, 506U, 3362628973U },
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{ 1535432887U, 998U, 42610943U },
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{ 1330635533U, 857U, 3040806504U },
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{ 1223800550U, 539U, 3954229517U },
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{ 1322411537U, 680U, 3223250324U },
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{ 1877847898U, 945U, 2915147143U },
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{ 1646356099U, 874U, 965988280U },
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{ 805687536U, 744U, 4032277920U },
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{ 1948093210U, 633U, 1346597684U },
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{ 392609744U, 783U, 1636083295U },
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{ 690241304U, 770U, 1201031298U },
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{ 1360302965U, 696U, 1665394461U },
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{ 1220090946U, 780U, 1316922812U },
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{ 447092251U, 500U, 3438743375U },
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{ 1613868791U, 592U, 828546883U },
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{ 523430951U, 548U, 2552392304U },
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{ 726692899U, 810U, 1656872867U },
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{ 1364340021U, 836U, 3710513486U },
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{ 1986257729U, 931U, 935013962U },
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{ 407983964U, 921U, 728767059U },
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};
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static u32 __extract_hwseed(void)
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{
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unsigned int val = 0;
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(void)(arch_get_random_seed_int(&val) ||
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arch_get_random_int(&val));
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return val;
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}
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static void prandom_seed_early(struct rnd_state *state, u32 seed,
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bool mix_with_hwseed)
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{
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#define LCG(x) ((x) * 69069U) /* super-duper LCG */
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#define HWSEED() (mix_with_hwseed ? __extract_hwseed() : 0)
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state->s1 = __seed(HWSEED() ^ LCG(seed), 2U);
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state->s2 = __seed(HWSEED() ^ LCG(state->s1), 8U);
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state->s3 = __seed(HWSEED() ^ LCG(state->s2), 16U);
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state->s4 = __seed(HWSEED() ^ LCG(state->s3), 128U);
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}
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static int __init prandom_state_selftest(void)
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{
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int i, j, errors = 0, runs = 0;
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bool error = false;
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for (i = 0; i < ARRAY_SIZE(test1); i++) {
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struct rnd_state state;
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prandom_seed_early(&state, test1[i].seed, false);
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prandom_warmup(&state);
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if (test1[i].result != prandom_u32_state(&state))
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error = true;
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}
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if (error)
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pr_warn("prandom: seed boundary self test failed\n");
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else
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pr_info("prandom: seed boundary self test passed\n");
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for (i = 0; i < ARRAY_SIZE(test2); i++) {
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struct rnd_state state;
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prandom_seed_early(&state, test2[i].seed, false);
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prandom_warmup(&state);
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for (j = 0; j < test2[i].iteration - 1; j++)
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prandom_u32_state(&state);
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if (test2[i].result != prandom_u32_state(&state))
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errors++;
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runs++;
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cond_resched();
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}
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if (errors)
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pr_warn("prandom: %d/%d self tests failed\n", errors, runs);
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else
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pr_info("prandom: %d self tests passed\n", runs);
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return 0;
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}
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core_initcall(prandom_state_selftest);
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#endif
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/*
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* The prandom_u32() implementation is now completely separate from the
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* prandom_state() functions, which are retained (for now) for compatibility.
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*
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* Because of (ab)use in the networking code for choosing random TCP/UDP port
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* numbers, which open DoS possibilities if guessable, we want something
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* stronger than a standard PRNG. But the performance requirements of
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* the network code do not allow robust crypto for this application.
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*
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* So this is a homebrew Junior Spaceman implementation, based on the
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* lowest-latency trustworthy crypto primitive available, SipHash.
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* (The authors of SipHash have not been consulted about this abuse of
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* their work.)
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*
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* Standard SipHash-2-4 uses 2n+4 rounds to hash n words of input to
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* one word of output. This abbreviated version uses 2 rounds per word
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* of output.
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*/
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struct siprand_state {
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unsigned long v0;
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unsigned long v1;
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unsigned long v2;
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unsigned long v3;
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};
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static DEFINE_PER_CPU(struct siprand_state, net_rand_state) __latent_entropy;
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/*
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* This is the core CPRNG function. As "pseudorandom", this is not used
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* for truly valuable things, just intended to be a PITA to guess.
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* For maximum speed, we do just two SipHash rounds per word. This is
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* the same rate as 4 rounds per 64 bits that SipHash normally uses,
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* so hopefully it's reasonably secure.
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*
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* There are two changes from the official SipHash finalization:
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* - We omit some constants XORed with v2 in the SipHash spec as irrelevant;
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* they are there only to make the output rounds distinct from the input
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* rounds, and this application has no input rounds.
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* - Rather than returning v0^v1^v2^v3, return v1+v3.
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* If you look at the SipHash round, the last operation on v3 is
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* "v3 ^= v0", so "v0 ^ v3" just undoes that, a waste of time.
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* Likewise "v1 ^= v2". (The rotate of v2 makes a difference, but
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* it still cancels out half of the bits in v2 for no benefit.)
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* Second, since the last combining operation was xor, continue the
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* pattern of alternating xor/add for a tiny bit of extra non-linearity.
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*/
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static inline u32 siprand_u32(struct siprand_state *s)
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{
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unsigned long v0 = s->v0, v1 = s->v1, v2 = s->v2, v3 = s->v3;
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PRND_SIPROUND(v0, v1, v2, v3);
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PRND_SIPROUND(v0, v1, v2, v3);
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s->v0 = v0; s->v1 = v1; s->v2 = v2; s->v3 = v3;
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return v1 + v3;
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}
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/**
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* prandom_u32 - pseudo random number generator
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*
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* A 32 bit pseudo-random number is generated using a fast
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* algorithm suitable for simulation. This algorithm is NOT
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* considered safe for cryptographic use.
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*/
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u32 prandom_u32(void)
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{
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struct siprand_state *state = get_cpu_ptr(&net_rand_state);
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u32 res = siprand_u32(state);
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put_cpu_ptr(&net_rand_state);
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return res;
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}
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EXPORT_SYMBOL(prandom_u32);
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/**
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* prandom_bytes - get the requested number of pseudo-random bytes
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* @buf: where to copy the pseudo-random bytes to
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* @bytes: the requested number of bytes
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*/
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void prandom_bytes(void *buf, size_t bytes)
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{
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struct siprand_state *state = get_cpu_ptr(&net_rand_state);
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u8 *ptr = buf;
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while (bytes >= sizeof(u32)) {
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put_unaligned(siprand_u32(state), (u32 *)ptr);
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ptr += sizeof(u32);
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bytes -= sizeof(u32);
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}
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if (bytes > 0) {
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u32 rem = siprand_u32(state);
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do {
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*ptr++ = (u8)rem;
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rem >>= BITS_PER_BYTE;
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} while (--bytes > 0);
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}
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put_cpu_ptr(&net_rand_state);
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}
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EXPORT_SYMBOL(prandom_bytes);
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/**
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* prandom_seed - add entropy to pseudo random number generator
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* @entropy: entropy value
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*
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* Add some additional seed material to the prandom pool.
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* The "entropy" is actually our IP address (the only caller is
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* the network code), not for unpredictability, but to ensure that
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* different machines are initialized differently.
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*/
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void prandom_seed(u32 entropy)
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{
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int i;
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add_device_randomness(&entropy, sizeof(entropy));
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for_each_possible_cpu(i) {
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|
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 void prandom_timer_start(struct random_ready_callback *unused)
|
|
{
|
|
mod_timer(&seed_timer, jiffies);
|
|
}
|
|
|
|
/*
|
|
* Start periodic full reseeding as soon as strong
|
|
* random numbers are available.
|
|
*/
|
|
static int __init prandom_init_late(void)
|
|
{
|
|
static struct random_ready_callback random_ready = {
|
|
.func = prandom_timer_start
|
|
};
|
|
int ret = add_random_ready_callback(&random_ready);
|
|
|
|
if (ret == -EALREADY) {
|
|
prandom_timer_start(&random_ready);
|
|
ret = 0;
|
|
}
|
|
return ret;
|
|
}
|
|
late_initcall(prandom_init_late);
|