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BN_mod_exp_mont_consttime: check for zero modulus.

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Don't dereference |d| when |top| is zero. Also test that various BIGNUM methods behave correctly on zero/even inputs.

Follow-up to b11980d79a

Reviewed-by: Rich Salz <rsalz@openssl.org>
This commit is contained in:
Emilia Kasper 2015-08-31 15:51:27 +02:00
parent 732a6b5522
commit cf633fa002
2 changed files with 56 additions and 3 deletions
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7
crypto/bn/bn_exp.c
View file

@ -662,12 +662,13 @@ int BN_mod_exp_mont_consttime(BIGNUM *rr, const BIGNUM *a, const BIGNUM *p,
bn_check_top(p);
bn_check_top(m);
top = m->top;
if (!(m->d[0] & 1)) {
if (!BN_is_odd(m)) {
BNerr(BN_F_BN_MOD_EXP_MONT_CONSTTIME, BN_R_CALLED_WITH_EVEN_MODULUS);
return (0);
}
top = m->top;
bits = BN_num_bits(p);
if (bits == 0) {
ret = BN_one(rr);

52
crypto/bn/bntest.c
View file

@ -441,6 +441,14 @@ int test_div(BIO *bp, BN_CTX *ctx)
BN_init(&d);
BN_init(&e);
BN_one(&a);
BN_zero(&b);
if (BN_div(&d, &c, &a, &b, ctx)) {
fprintf(stderr, "Division by zero succeeded!\n");
return 0;
}
for (i = 0; i < num0 + num1; i++) {
if (i < num1) {
BN_bntest_rand(&a, 400, 0, 0);
@ -781,6 +789,18 @@ int test_mont(BIO *bp, BN_CTX *ctx)
if (mont == NULL)
return 0;
BN_zero(&n);
if (BN_MONT_CTX_set(mont, &n, ctx)) {
fprintf(stderr, "BN_MONT_CTX_set succeeded for zero modulus!\n");
return 0;
}
BN_set_word(&n, 16);
if (BN_MONT_CTX_set(mont, &n, ctx)) {
fprintf(stderr, "BN_MONT_CTX_set succeeded for even modulus!\n");
return 0;
}
BN_bntest_rand(&a, 100, 0, 0);
BN_bntest_rand(&b, 100, 0, 0);
for (i = 0; i < num2; i++) {
@ -887,6 +907,14 @@ int test_mod_mul(BIO *bp, BN_CTX *ctx)
d = BN_new();
e = BN_new();
BN_one(a);
BN_one(b);
BN_zero(c);
if (BN_mod_mul(e, a, b, c, ctx)) {
fprintf(stderr, "BN_mod_mul with zero modulus succeeded!\n");
return 0;
}
for (j = 0; j < 3; j++) {
BN_bntest_rand(c, 1024, 0, 0);
for (i = 0; i < num0; i++) {
@ -952,6 +980,14 @@ int test_mod_exp(BIO *bp, BN_CTX *ctx)
d = BN_new();
e = BN_new();
BN_one(a);
BN_one(b);
BN_zero(c);
if (BN_mod_exp(d, a, b, c, ctx)) {
fprintf(stderr, "BN_mod_exp with zero modulus succeeded!\n");
return 0;
}
BN_bntest_rand(c, 30, 0, 1); /* must be odd for montgomery */
for (i = 0; i < num2; i++) {
BN_bntest_rand(a, 20 + i * 5, 0, 0);
@ -999,6 +1035,22 @@ int test_mod_exp_mont_consttime(BIO *bp, BN_CTX *ctx)
d = BN_new();
e = BN_new();
BN_one(a);
BN_one(b);
BN_zero(c);
if (BN_mod_exp_mont_consttime(d, a, b, c, ctx, NULL)) {
fprintf(stderr, "BN_mod_exp_mont_consttime with zero modulus "
"succeeded\n");
return 0;
}
BN_set_word(c, 16);
if (BN_mod_exp_mont_consttime(d, a, b, c, ctx, NULL)) {
fprintf(stderr, "BN_mod_exp_mont_consttime with even modulus "
"succeeded\n");
return 0;
}
BN_bntest_rand(c, 30, 0, 1); /* must be odd for montgomery */
for (i = 0; i < num2; i++) {
BN_bntest_rand(a, 20 + i * 5, 0, 0);