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Fix an endless loop in BN_generate_prime_ex

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Happens when trying to generate 4 or 5 bit safe primes.

[extended tests]

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9311)
This commit is contained in:
Bernd Edlinger 2019-07-04 17:56:23 +02:00
parent 2a1e2fe145
commit 291f616ced
2 changed files with 46 additions and 9 deletions
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8
crypto/bn/bn_prime.c
View File

@ -98,8 +98,12 @@ int BN_generate_prime_ex(BIGNUM *ret, int bits, int safe,
/* There are no prime numbers this small. */
BNerr(BN_F_BN_GENERATE_PRIME_EX, BN_R_BITS_TOO_SMALL);
return 0;
} else if (bits == 2 && safe) {
/* The smallest safe prime (7) is three bits. */
} else if (add == NULL && safe && bits < 6 && bits != 3) {
/*
* The smallest safe prime (7) is three bits.
* But the following two safe primes with less than 6 bits (11, 23)
* are unreachable for BN_rand with BN_RAND_TOP_TWO.
*/
BNerr(BN_F_BN_GENERATE_PRIME_EX, BN_R_BITS_TOO_SMALL);
return 0;
}

47
test/bntest.c
View File

@ -2249,18 +2249,50 @@ static int test_expmodone(void)
return ret;
}
static int test_smallprime(void)
static int test_smallprime(int kBits)
{
static const int kBits = 10;
BIGNUM *r;
int st = 0;
if (!TEST_ptr(r = BN_new())
|| !TEST_true(BN_generate_prime_ex(r, (int)kBits, 0,
NULL, NULL, NULL))
|| !TEST_int_eq(BN_num_bits(r), kBits))
if (!TEST_ptr(r = BN_new()))
goto err;
if (kBits <= 1) {
if (!TEST_false(BN_generate_prime_ex(r, kBits, 0,
NULL, NULL, NULL)))
goto err;
} else {
if (!TEST_true(BN_generate_prime_ex(r, kBits, 0,
NULL, NULL, NULL))
|| !TEST_int_eq(BN_num_bits(r), kBits))
goto err;
}
st = 1;
err:
BN_free(r);
return st;
}
static int test_smallsafeprime(int kBits)
{
BIGNUM *r;
int st = 0;
if (!TEST_ptr(r = BN_new()))
goto err;
if (kBits <= 5 && kBits != 3) {
if (!TEST_false(BN_generate_prime_ex(r, kBits, 1,
NULL, NULL, NULL)))
goto err;
} else {
if (!TEST_true(BN_generate_prime_ex(r, kBits, 1,
NULL, NULL, NULL))
|| !TEST_int_eq(BN_num_bits(r), kBits))
goto err;
}
st = 1;
err:
BN_free(r);
@ -2518,7 +2550,8 @@ int setup_tests(void)
ADD_TEST(test_badmod);
ADD_TEST(test_expmodzero);
ADD_TEST(test_expmodone);
ADD_TEST(test_smallprime);
ADD_ALL_TESTS(test_smallprime, 16);
ADD_ALL_TESTS(test_smallsafeprime, 16);
ADD_TEST(test_swap);
ADD_TEST(test_ctx_consttime_flag);
#ifndef OPENSSL_NO_EC2M