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Merge pull request #2615 from SparkiDev/mp_exptmod_neg_p

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Handle negative modulus with negative exponent in exptmod
This commit is contained in:
toddouska
2019-11-26 15:20:54 -08:00
committed by GitHub
parent 95c9dc9fe8 50c4347748
commit 0d69950d07
1 changed files with 34 additions and 11 deletions
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45
wolfcrypt/src/tfm.c
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@ -2178,6 +2178,11 @@ int fp_exptmod(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
int x = fp_count_bits (X);
#endif
if (fp_iszero(G)) {
fp_set(G, 0);
return FP_OKAY;
}
/* prevent overflows */
if (P->used > (FP_SIZE/2)) {
return FP_VAL;
@ -2194,26 +2199,31 @@ int fp_exptmod(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
#ifndef POSITIVE_EXP_ONLY /* reduce stack if assume no negatives */
int err;
#ifndef WOLFSSL_SMALL_STACK
fp_int tmp[1];
fp_int tmp[2];
#else
fp_int *tmp;
#endif
#ifdef WOLFSSL_SMALL_STACK
tmp = (fp_int*)XMALLOC(sizeof(fp_int), NULL, DYNAMIC_TYPE_BIGINT);
tmp = (fp_int*)XMALLOC(sizeof(fp_int) * 2, NULL, DYNAMIC_TYPE_BIGINT);
if (tmp == NULL)
return FP_MEM;
#endif
/* yes, copy G and invmod it */
fp_init_copy(tmp, G);
err = fp_invmod(tmp, P, tmp);
fp_init_copy(&tmp[0], G);
fp_init_copy(&tmp[1], P);
tmp[1].sign = FP_ZPOS;
err = fp_invmod(&tmp[0], &tmp[1], &tmp[0]);
if (err == FP_OKAY) {
X->sign = FP_ZPOS;
err = _fp_exptmod(tmp, X, X->used, P, Y);
err = _fp_exptmod(&tmp[0], X, X->used, P, Y);
if (X != Y) {
X->sign = FP_NEG;
}
if (P->sign == FP_NEG) {
fp_add(Y, P, Y);
}
}
#ifdef WOLFSSL_SMALL_STACK
XFREE(tmp, NULL, DYNAMIC_TYPE_TMP_BUFFER);
@ -2240,6 +2250,11 @@ int fp_exptmod_ex(fp_int * G, fp_int * X, int digits, fp_int * P, fp_int * Y)
int x = fp_count_bits (X);
#endif
if (fp_iszero(G)) {
fp_set(G, 0);
return FP_OKAY;
}
/* prevent overflows */
if (P->used > (FP_SIZE/2)) {
return FP_VAL;
@ -2256,26 +2271,31 @@ int fp_exptmod_ex(fp_int * G, fp_int * X, int digits, fp_int * P, fp_int * Y)
#ifndef POSITIVE_EXP_ONLY /* reduce stack if assume no negatives */
int err;
#ifndef WOLFSSL_SMALL_STACK
fp_int tmp[1];
fp_int tmp[2];
#else
fp_int *tmp;
#endif
#ifdef WOLFSSL_SMALL_STACK
tmp = (fp_int*)XMALLOC(sizeof(fp_int), NULL, DYNAMIC_TYPE_TMP_BUFFER);
tmp = (fp_int*)XMALLOC(sizeof(fp_int) * 2, NULL, DYNAMIC_TYPE_TMP_BUFFER);
if (tmp == NULL)
return FP_MEM;
#endif
/* yes, copy G and invmod it */
fp_init_copy(tmp, G);
err = fp_invmod(tmp, P, tmp);
fp_init_copy(&tmp[0], G);
fp_init_copy(&tmp[1], P);
tmp[1].sign = FP_ZPOS;
err = fp_invmod(&tmp[0], &tmp[1], &tmp[0]);
if (err == FP_OKAY) {
X->sign = FP_ZPOS;
err = _fp_exptmod(tmp, X, digits, P, Y);
err = _fp_exptmod(&tmp[0], X, digits, P, Y);
if (X != Y) {
X->sign = FP_NEG;
}
if (P->sign == FP_NEG) {
fp_add(Y, P, Y);
}
}
#ifdef WOLFSSL_SMALL_STACK
XFREE(tmp, NULL, DYNAMIC_TYPE_BIGINT);
@ -4429,6 +4449,9 @@ int fp_gcd(fp_int *a, fp_int *b, fp_int *c)
fp_init_copy(v, a);
}
u->sign = FP_ZPOS;
v->sign = FP_ZPOS;
fp_init(r);
while (fp_iszero(v) == FP_NO) {
fp_mod(u, v, r);
@ -4757,7 +4780,7 @@ int mp_toradix (mp_int *a, char *str, int radix)
if (fp_iszero(a) == FP_YES) {
*str++ = '0';
*str = '\0';
return FP_YES;
return FP_OKAY;
}
#ifdef WOLFSSL_SMALL_STACK