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wolfcrypt/src/ecc.c: smallstack refactor of variable t in wc_ecc_mulmod_ex2()

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This commit is contained in:
Daniel Pouzzner
2025-12-26 13:05:52 -06:00
parent 4170d1ab09
commit 57d2391b6c
1 changed files with 15 additions and 8 deletions
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23
wolfcrypt/src/ecc.c
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@@ -3181,7 +3181,7 @@ int wc_ecc_mulmod_ex2(const mp_int* k, ecc_point *G, ecc_point *R, mp_int* a,
#endif
mp_digit mp;
#ifdef ECC_TIMING_RESISTANT
mp_int t;
WC_DECLARE_VAR(t, mp_int, 1, heap);
#endif
if (k == NULL || G == NULL || R == NULL || modulus == NULL) {
@@ -3207,6 +3207,10 @@ int wc_ecc_mulmod_ex2(const mp_int* k, ecc_point *G, ecc_point *R, mp_int* a,
R->key = key;
#endif /* WOLFSSL_SMALL_STACK_CACHE */
#ifdef ECC_TIMING_RESISTANT
WC_ALLOC_VAR_EX(t, mp_int, 1, heap, DYNAMIC_TYPE_BIGINT, err = MEMORY_E; goto exit );
#endif
/* alloc ram for window temps */
for (i = 0; i < M_POINTS; i++) {
#ifdef WOLFSSL_NO_MALLOC
@@ -3244,9 +3248,8 @@ int wc_ecc_mulmod_ex2(const mp_int* k, ecc_point *G, ecc_point *R, mp_int* a,
goto exit;
}
#ifdef ECC_TIMING_RESISTANT
if ((err = mp_init(&t)) != MP_OKAY)
if ((err = mp_init(t)) != MP_OKAY)
goto exit;
if (err == MP_OKAY)
@@ -3257,22 +3260,22 @@ int wc_ecc_mulmod_ex2(const mp_int* k, ecc_point *G, ecc_point *R, mp_int* a,
* (with constant time implementation)
*/
if (err == MP_OKAY)
err = mp_sub_d(order, 1, &t);
err = mp_sub_d(order, 1, t);
if (err == MP_OKAY) {
int kIsMinusOne = (mp_cmp((mp_int*)k, &t) == MP_EQ);
int kIsMinusOne = (mp_cmp((mp_int*)k, t) == MP_EQ);
err = mp_cond_copy(tG->x, kIsMinusOne, R->x);
if (err == MP_OKAY) {
err = mp_sub(modulus, tG->y, &t);
err = mp_sub(modulus, tG->y, t);
}
if (err == MP_OKAY) {
err = mp_cond_copy(&t, kIsMinusOne, R->y);
err = mp_cond_copy(t, kIsMinusOne, R->y);
}
if (err == MP_OKAY) {
err = mp_cond_copy(tG->z, kIsMinusOne, R->z);
}
}
mp_free(&t);
mp_free(t);
#else
err = ecc_mulmod(k, tG, R, M, a, modulus, mp, rng);
@@ -3295,6 +3298,10 @@ exit:
XFREE(key, heap, DYNAMIC_TYPE_ECC);
#endif /* WOLFSSL_SMALL_STACK_CACHE */
#ifdef ECC_TIMING_RESISTANT
WC_FREE_VAR_EX(t, heap, DYNAMIC_TYPE_BIGINT);
#endif
return err;
}
#else