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// 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 <asm/unaligned.h>
#include <trace/events/random.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;
DEFINE_PER_CPU(unsigned long, net_rand_noise);
EXPORT_PER_CPU_SYMBOL(net_rand_noise);
/*
* 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;
unsigned long n = raw_cpu_read(net_rand_noise);
v3 ^= n;
PRND_SIPROUND(v0, v1, v2, v3);
PRND_SIPROUND(v0, v1, v2, v3);
v0 ^= n;
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);
trace_prandom_u32(res);
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 void prandom_timer_start(struct random_ready_callback *unused)
{
mod_timer(&seed_timer, jiffies);
}
#ifdef CONFIG_RANDOM32_SELFTEST
/* Principle: True 32-bit random numbers will all have 16 differing bits on
* average. For each 32-bit number, there are 601M numbers differing by 16
* bits, and 89% of the numbers differ by at least 12 bits. Note that more
* than 16 differing bits also implies a correlation with inverted bits. Thus
* we take 1024 random numbers and compare each of them to the other ones,
* counting the deviation of correlated bits to 16. Constants report 32,
* counters 32-log2(TEST_SIZE), and pure randoms, around 6 or lower. With the
* u32 total, TEST_SIZE may be as large as 4096 samples.
*/
#define TEST_SIZE 1024
static int __init prandom32_state_selftest(void)
{
unsigned int x, y, bits, samples;
u32 xor, flip;
u32 total;
u32 *data;
data = kmalloc(sizeof(*data) * TEST_SIZE, GFP_KERNEL);
if (!data)
return 0;
for (samples = 0; samples < TEST_SIZE; samples++)
data[samples] = prandom_u32();
flip = total = 0;
for (x = 0; x < samples; x++) {
for (y = 0; y < samples; y++) {
if (x == y)
continue;
xor = data[x] ^ data[y];
flip |= xor;
bits = hweight32(xor);
total += (bits - 16) * (bits - 16);
}
}
/* We'll return the average deviation as 2*sqrt(corr/samples), which
* is also sqrt(4*corr/samples) which provides a better resolution.
*/
bits = int_sqrt(total / (samples * (samples - 1)) * 4);
if (bits > 6)
pr_warn("prandom32: self test failed (at least %u bits"
" correlated, fixed_mask=%#x fixed_value=%#x\n",
bits, ~flip, data[0] & ~flip);
else
pr_info("prandom32: self test passed (less than %u bits"
" correlated)\n",
bits+1);
kfree(data);
return 0;
}
core_initcall(prandom32_state_selftest);
#endif /* CONFIG_RANDOM32_SELFTEST */
/*
* 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);