All exponentiation subroutines but BN_mod_exp_mont_consttime produce
non-negative result for negative input, which is confusing for fuzzer.
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/4676)
- /*
- * If the size of the operands allow it, perform the optimized
- * RSAZ exponentiation. For further information see
- * crypto/bn/rsaz_exp.c and accompanying assembly modules.
- */
- if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024)
- && rsaz_avx2_eligible()) {
- if (NULL == bn_wexpand(rr, 16))
+ if (!a->neg) {
+ /*
+ * If the size of the operands allow it, perform the optimized
+ * RSAZ exponentiation. For further information see
+ * crypto/bn/rsaz_exp.c and accompanying assembly modules.
+ */
+ if ((16 == a->top) && (16 == p->top) && (BN_num_bits(m) == 1024)
+ && rsaz_avx2_eligible()) {
+ if (NULL == bn_wexpand(rr, 16))
+ goto err;
+ RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d,
+ mont->n0[0]);
+ rr->top = 16;
+ rr->neg = 0;
+ bn_correct_top(rr);
+ ret = 1;
- RSAZ_1024_mod_exp_avx2(rr->d, a->d, p->d, m->d, mont->RR.d,
- mont->n0[0]);
- rr->top = 16;
- rr->neg = 0;
- bn_correct_top(rr);
- ret = 1;
- goto err;
- } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) {
- if (NULL == bn_wexpand(rr, 8))
+ } else if ((8 == a->top) && (8 == p->top) && (BN_num_bits(m) == 512)) {
+ if (NULL == bn_wexpand(rr, 8))
+ goto err;
+ RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d);
+ rr->top = 8;
+ rr->neg = 0;
+ bn_correct_top(rr);
+ ret = 1;
- RSAZ_512_mod_exp(rr->d, a->d, p->d, m->d, mont->n0[0], mont->RR.d);
- rr->top = 8;
- rr->neg = 0;
- bn_correct_top(rr);
- ret = 1;
- goto err;
/* prepare a^1 in Montgomery domain */
if (a->neg || BN_ucmp(a, m) >= 0) {
/* prepare a^1 in Montgomery domain */
if (a->neg || BN_ucmp(a, m) >= 0) {
- if (!BN_mod(&am, a, m, ctx))
+ if (!BN_nnmod(&am, a, m, ctx))
goto err;
if (!BN_to_montgomery(&am, &am, mont, ctx))
goto err;
goto err;
if (!BN_to_montgomery(&am, &am, mont, ctx))
goto err;
/* x**0 mod 1 is still zero. */
if (BN_is_one(m)) {
ret = 1;
/* x**0 mod 1 is still zero. */
if (BN_is_one(m)) {
ret = 1;