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fix: BN_swap mishandles flags

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Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6099)
This commit is contained in:
Billy Brumley 2018-04-26 18:08:36 +03:00 committed by Matt Caswell
parent 32c6985349
commit 9e5b50b54d
2 changed files with 80 additions and 4 deletions
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11
crypto/bn/bn_lib.c
View file

@ -300,6 +300,11 @@ BIGNUM *BN_copy(BIGNUM *a, const BIGNUM *b)
return a;
}
#define FLAGS_DATA(flags) ((flags) & (BN_FLG_STATIC_DATA \
| BN_FLG_CONSTTIME \
| BN_FLG_SECURE))
#define FLAGS_STRUCT(flags) ((flags) & (BN_FLG_MALLOCED))
void BN_swap(BIGNUM *a, BIGNUM *b)
{
int flags_old_a, flags_old_b;
@ -327,10 +332,8 @@ void BN_swap(BIGNUM *a, BIGNUM *b)
b->dmax = tmp_dmax;
b->neg = tmp_neg;
a->flags =
(flags_old_a & BN_FLG_MALLOCED) | (flags_old_b & BN_FLG_STATIC_DATA);
b->flags =
(flags_old_b & BN_FLG_MALLOCED) | (flags_old_a & BN_FLG_STATIC_DATA);
a->flags = FLAGS_STRUCT(flags_old_a) | FLAGS_DATA(flags_old_b);
b->flags = FLAGS_STRUCT(flags_old_b) | FLAGS_DATA(flags_old_a);
bn_check_top(a);
bn_check_top(b);
}

73
test/bntest.c
View file

@ -151,6 +151,78 @@ static int rand_neg(void)
}
static int test_swap(void)
{
BIGNUM *a = NULL, *b = NULL, *c = NULL, *d = NULL;
int top, cond, st = 0;
if (!TEST_ptr(a = BN_new())
|| !TEST_ptr(b = BN_new())
|| !TEST_ptr(c = BN_new())
|| !TEST_ptr(d = BN_new()))
goto err;
BN_bntest_rand(a, 1024, 1, 0);
BN_bntest_rand(b, 1024, 1, 0);
BN_copy(c, a);
BN_copy(d, b);
top = BN_num_bits(a)/BN_BITS2;
/* regular swap */
BN_swap(a, b);
if (!equalBN("swap", a, d)
|| !equalBN("swap", b, c))
goto err;
/* conditional swap: true */
cond = 1;
BN_consttime_swap(cond, a, b, top);
if (!equalBN("cswap true", a, c)
|| !equalBN("cswap true", b, d))
goto err;
/* conditional swap: false */
cond = 0;
BN_consttime_swap(cond, a, b, top);
if (!equalBN("cswap false", a, c)
|| !equalBN("cswap false", b, d))
goto err;
/* same tests but checking flag swap */
BN_set_flags(a, BN_FLG_CONSTTIME);
BN_swap(a, b);
if (!equalBN("swap, flags", a, d)
|| !equalBN("swap, flags", b, c)
|| !TEST_true(BN_get_flags(b, BN_FLG_CONSTTIME))
|| !TEST_false(BN_get_flags(a, BN_FLG_CONSTTIME)))
goto err;
cond = 1;
BN_consttime_swap(cond, a, b, top);
if (!equalBN("cswap true, flags", a, c)
|| !equalBN("cswap true, flags", b, d)
|| !TEST_true(BN_get_flags(a, BN_FLG_CONSTTIME))
|| !TEST_false(BN_get_flags(b, BN_FLG_CONSTTIME)))
goto err;
cond = 0;
BN_consttime_swap(cond, a, b, top);
if (!equalBN("cswap false, flags", a, c)
|| !equalBN("cswap false, flags", b, d)
|| !TEST_true(BN_get_flags(a, BN_FLG_CONSTTIME))
|| !TEST_false(BN_get_flags(b, BN_FLG_CONSTTIME)))
goto err;
st = 1;
err:
BN_free(a);
BN_free(b);
BN_free(c);
BN_free(d);
return st;
}
static int test_sub(void)
{
BIGNUM *a = NULL, *b = NULL, *c = NULL;
@ -2118,6 +2190,7 @@ int setup_tests(void)
ADD_TEST(test_badmod);
ADD_TEST(test_expmodzero);
ADD_TEST(test_smallprime);
ADD_TEST(test_swap);
#ifndef OPENSSL_NO_EC2M
ADD_TEST(test_gf2m_add);
ADD_TEST(test_gf2m_mod);