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random32: add test cases for taus113 implementation
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We generated a battery of 100 test cases from GSL taus113 implemention
and compare the results from a particular seed and a particular
iteration with our implementation in the kernel. We have verified on
32 and 64 bit machines that our taus113 kernel implementation gives
same results as GSL taus113 implementation:

  [    0.147370] prandom: seed boundary self test passed
  [    0.148078] prandom: 100 self tests passed

This is a Kconfig option that is disabled on default, just like the
crc32 init selftests in order to not unnecessary slow down boot process.
We also refactored out prandom_seed_very_weak() as it's now used in
multiple places in order to reduce redundant code.

GSL code we used for generating test cases:

  int i, j;
  srand(time(NULL));
  for (i = 0; i < 100; ++i) {
    int iteration = 500 + (rand() % 500);
    gsl_rng_default_seed = rand() + 1;
    gsl_rng *r = gsl_rng_alloc(gsl_rng_taus113);
    printf("\t{ %lu, ", gsl_rng_default_seed);
    for (j = 0; j < iteration - 1; ++j)
      gsl_rng_get(r);
    printf("%u, %lu },\n", iteration, gsl_rng_get(r));
    gsl_rng_free(r);
  }

Joint work with Hannes Frederic Sowa.

Cc: Florian Weimer <fweimer@redhat.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Daniel Borkmann authored and David S. Miller committed Nov 11, 2013
1 parent a98814c commit a6a9c0f
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Showing 2 changed files with 196 additions and 6 deletions.
7 changes: 7 additions & 0 deletions lib/Kconfig
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Original file line number Diff line number Diff line change
Expand Up @@ -189,6 +189,13 @@ config AUDIT_GENERIC
depends on AUDIT && !AUDIT_ARCH
default y

config RANDOM32_SELFTEST
bool "PRNG perform self test on init"
default n
help
This option enables the 32 bit PRNG library functions to perform a
self test on initialization.

#
# compression support is select'ed if needed
#
Expand Down
195 changes: 189 additions & 6 deletions lib/random32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,11 @@
#include <linux/export.h>
#include <linux/jiffies.h>
#include <linux/random.h>
#include <linux/sched.h>

#ifdef CONFIG_RANDOM32_SELFTEST
static void __init prandom_state_selftest(void);
#endif

static DEFINE_PER_CPU(struct rnd_state, net_rand_state);

Expand Down Expand Up @@ -142,6 +147,23 @@ static void prandom_warmup(struct rnd_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
Expand Down Expand Up @@ -172,15 +194,14 @@ 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);

#define LCG(x) ((x) * 69069U) /* super-duper LCG */
state->s1 = __seed(LCG((i + jiffies) ^ random_get_entropy()), 2U);
state->s2 = __seed(LCG(state->s1), 8U);
state->s3 = __seed(LCG(state->s2), 16U);
state->s4 = __seed(LCG(state->s3), 128U);

prandom_seed_very_weak(state, (i + jiffies) ^ random_get_entropy());
prandom_warmup(state);
}
return 0;
Expand Down Expand Up @@ -253,3 +274,165 @@ static int __init prandom_reseed(void)
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

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