Test of uniformity of BN_rand_range output.

Rework the test so that it fails far less often.

A number of independent tests are executed and 5% are expected to fail.
The number of such failures follows a binomial distribution which permits
a statistical test a 0.01% expected failure rate.

There is a command line option to enable the stochastic range checking.
It is off by default.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/8830)
This commit is contained in:
Pauli 2019-05-29 09:54:29 +10:00
parent d4e2d5db62
commit 5d2f3e4a6c
3 changed files with 123 additions and 24 deletions

View File

@ -1200,6 +1200,11 @@
$ make TESTS='[89]? -90'
To stochastically verify that the algorithm that produces uniformly distributed
random numbers is operating correctly (with a false positive rate of 0.01%):
$ ./util/shlib_wrap.sh test/bntest -stochastic
Note on multi-threading
-----------------------

58
test/bn_rand_range.h Normal file
View File

@ -0,0 +1,58 @@
/*
* WARNING: do not edit!
* Generated by statistics/bn_rand_range.py in the OpenSSL tool repository.
*
* Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
static const struct {
unsigned int range;
unsigned int iterations;
double critical;
} rand_range_cases[] = {
{ 2, 200, 3.841459 },
{ 3, 300, 5.991465 },
{ 4, 400, 7.814728 },
{ 5, 500, 9.487729 },
{ 6, 600, 11.070498 },
{ 7, 700, 12.591587 },
{ 8, 800, 14.067140 },
{ 9, 900, 15.507313 },
{ 10, 1000, 16.918978 },
{ 11, 1100, 18.307038 },
{ 12, 1200, 19.675138 },
{ 13, 1300, 21.026070 },
{ 14, 1400, 22.362032 },
{ 15, 1500, 23.684791 },
{ 16, 1600, 24.995790 },
{ 17, 1700, 26.296228 },
{ 18, 1800, 27.587112 },
{ 19, 1900, 28.869299 },
{ 20, 2000, 30.143527 },
{ 30, 3000, 42.556968 },
{ 40, 4000, 54.572228 },
{ 50, 5000, 66.338649 },
{ 60, 6000, 77.930524 },
{ 70, 7000, 89.391208 },
{ 80, 8000, 100.748619 },
{ 90, 9000, 112.021986 },
{ 100, 10000, 123.225221 },
{ 1000, 10000, 1073.642651 },
{ 2000, 20000, 2104.128222 },
{ 3000, 30000, 3127.515432 },
{ 4000, 40000, 4147.230012 },
{ 5000, 50000, 5164.598069 },
{ 6000, 60000, 6180.299514 },
{ 7000, 70000, 7194.738181 },
{ 8000, 80000, 8208.177159 },
{ 9000, 90000, 9220.799176 },
{ 10000, 100000, 10232.737266 },
};
static const int binomial_critical = 29;

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@ -1956,25 +1956,27 @@ static int test_rand(void)
/*
* Run some statistical tests to provide a degree confidence that the
* BN_rand_range() function works as expected. The critical value
* is computed using the R statistical suite:
* BN_rand_range() function works as expected. The test cases and
* critical values are generated by the bn_rand_range script.
*
* qchisq(alpha, df=iterations - 1)
* Each individual test is a Chi^2 goodness of fit for a specified number
* of samples and range. The samples are assumed to be independent and
* that they are from a discrete uniform distribution.
*
* where alpha is the significance level (0.95 is used here) and iterations
* is the number of samples being drawn.
* Some of these individual tests are expected to fail, the success/failure
* of each is an independent Bernoulli trial. The number of such successes
* will form a binomial distribution. The count of the successes is compared
* against a precomputed critical value to determine the overall outcome.
*/
static const struct {
struct rand_range_case {
unsigned int range;
unsigned int iterations;
double critical;
} rand_range_cases[] = {
{ 2, 100, 123.2252 /* = qchisq(.95, df=99) */ },
{ 12, 1000, 1073.643 /* = qchisq(.95, df=999) */ },
{ 1023, 100000, 100735.7 /* = qchisq(.95, df=99999) */ },
};
static int test_rand_range(int n)
#include "bn_rand_range.h"
static int test_rand_range_single(size_t n)
{
const unsigned int range = rand_range_cases[n].range;
const unsigned int iterations = rand_range_cases[n].iterations;
@ -1998,22 +2000,20 @@ static int test_rand_range(int n)
counts[v]++;
}
TEST_note("range %u iterations %u critical %.4f", range, iterations,
critical);
if (range < 20) {
TEST_note("frequencies (expected %.2f)", expected);
for (i = 0; i < range; i++)
TEST_note(" %2u %6zu", i, counts[i]);
}
for (i = 0; i < range; i++) {
const double delta = counts[i] - expected;
sum += delta * delta;
}
sum /= expected;
TEST_note("test statistic %.4f", sum);
if (TEST_double_lt(sum, critical))
res = 1;
if (sum > critical) {
TEST_info("Chi^2 test negative %.4f > %4.f", sum, critical);
TEST_note("test case %zu range %u iterations %u", n + 1, range,
iterations);
goto err;
}
res = 1;
err:
BN_free(rng);
BN_free(val);
@ -2021,6 +2021,19 @@ err:
return res;
}
static int test_rand_range(void)
{
int n_success = 0;
size_t i;
for (i = 0; i < OSSL_NELEM(rand_range_cases); i++)
n_success += test_rand_range_single(i);
if (TEST_int_ge(n_success, binomial_critical))
return 1;
TEST_note("This test is expeced to fail by chance 0.01%% of the time.");
return 0;
}
static int test_negzero(void)
{
BIGNUM *a = NULL, *b = NULL, *c = NULL, *d = NULL;
@ -2448,11 +2461,18 @@ static int run_file_tests(int i)
return c == 0;
}
typedef enum OPTION_choice {
OPT_ERR = -1,
OPT_EOF = 0,
OPT_STOCHASTIC_TESTS,
OPT_TEST_ENUM
} OPTION_CHOICE;
const OPTIONS *test_get_options(void)
{
enum { OPT_TEST_ENUM };
static const OPTIONS test_options[] = {
OPT_TEST_OPTIONS_WITH_EXTRA_USAGE("[file...]\n"),
{ "stochastic", OPT_STOCHASTIC_TESTS, '-', "Run stochastic tests" },
{ OPT_HELP_STR, 1, '-',
"file\tFile to run tests on. Normal tests are not run\n" },
{ NULL }
@ -2462,7 +2482,22 @@ const OPTIONS *test_get_options(void)
int setup_tests(void)
{
int n = test_get_argument_count();
OPTION_CHOICE o;
int n, stochastic = 0;
while ((o = opt_next()) != OPT_EOF) {
switch (o) {
case OPT_STOCHASTIC_TESTS:
stochastic = 1;
break;
case OPT_TEST_CASES:
break;
default:
case OPT_ERR:
return 0;
}
}
n = test_get_argument_count();
if (!TEST_ptr(ctx = BN_CTX_new()))
return 0;
@ -2499,7 +2534,8 @@ int setup_tests(void)
#endif
ADD_ALL_TESTS(test_is_prime, (int)OSSL_NELEM(primes));
ADD_ALL_TESTS(test_not_prime, (int)OSSL_NELEM(not_primes));
ADD_ALL_TESTS(test_rand_range, OSSL_NELEM(rand_range_cases));
if (stochastic)
ADD_TEST(test_rand_range);
} else {
ADD_ALL_TESTS(run_file_tests, n);
}