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Merge pull request #4409 from SparkiDev/tfm_submod_ct

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TFM: fp_submod_ct fix check for greater
This commit is contained in:
John Safranek
2021-09-17 08:41:20 -07:00
committed by GitHub
parent bb70fee1ec 9623797064
commit ffa13f314b
1 changed files with 12 additions and 3 deletions
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15
wolfcrypt/src/tfm.c
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@ -1631,7 +1631,7 @@ int fp_submod_ct(fp_int *a, fp_int *b, fp_int *c, fp_int *d)
} }
/* Check whether b is greater than a. mask has all bits set when true. */ /* Check whether b is greater than a. mask has all bits set when true. */
mask = 0 - (fp_cmp_mag_ct(a, b, c->used) == (fp_digit)FP_LT); mask = 0 - (fp_cmp_mag_ct(a, b, c->used + 1) == (fp_digit)FP_LT);
/* Constant time, conditionally, add modulus to a into result. */ /* Constant time, conditionally, add modulus to a into result. */
for (i = 0; i < c->used; i++) { for (i = 0; i < c->used; i++) {
fp_digit mask_a = 0 - (i < a->used); fp_digit mask_a = 0 - (i < a->used);
@ -3371,7 +3371,7 @@ static int fp_montgomery_reduce_mulx(fp_int *a, fp_int *m, fp_digit mp, int ct)
/* bail if too large */ /* bail if too large */
if (m->used > (FP_SIZE/2)) { if (m->used > (FP_SIZE/2)) {
(void)mu; /* shut up compiler */ (void)mu; /* shut up compiler */
return FP_OKAY; return FP_VAL;
} }
#ifdef TFM_SMALL_MONT_SET #ifdef TFM_SMALL_MONT_SET
@ -3393,7 +3393,16 @@ static int fp_montgomery_reduce_mulx(fp_int *a, fp_int *m, fp_digit mp, int ct)
pa = m->used; pa = m->used;
/* copy the input */ /* copy the input */
#ifdef TFM_TIMING_RESISTANT
if (a->used <= m->used) {
oldused = m->used;
}
else {
oldused = m->used * 2;
}
#else
oldused = a->used; oldused = a->used;
#endif
for (x = 0; x < oldused; x++) { for (x = 0; x < oldused; x++) {
c[x] = a->dp[x]; c[x] = a->dp[x];
} }
@ -3439,7 +3448,7 @@ static int fp_montgomery_reduce_mulx(fp_int *a, fp_int *m, fp_digit mp, int ct)
a->used = pa+1; a->used = pa+1;
fp_clamp(a); fp_clamp(a);
#ifdef WOLFSSL_MONT_RED_NCT #ifndef WOLFSSL_MONT_RED_CT
/* if A >= m then A = A - m */ /* if A >= m then A = A - m */
if (fp_cmp_mag (a, m) != FP_LT) { if (fp_cmp_mag (a, m) != FP_LT) {
s_fp_sub (a, m, a); s_fp_sub (a, m, a);