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tfm: fix length check in add and mul_d

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Check that the overflow digit is going to fit rather than whether we are
at limit after adding digit.
This commit is contained in:
Sean Parkinson 2021-06-17 09:11:01 +10:00
parent 93ae372c55
commit 9023c4d65a
1 changed files with 6 additions and 7 deletions
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13
wolfcrypt/src/tfm.c
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@ -163,13 +163,12 @@ int s_fp_add(fp_int *a, fp_int *b, fp_int *c)
c->dp[x] = (fp_digit)t;
t >>= DIGIT_BIT;
}
if (t != 0 && x < FP_SIZE) {
if (t != 0) {
if (x == FP_SIZE)
return FP_VAL;
c->dp[c->used++] = (fp_digit)t;
++x;
}
if (x == FP_SIZE) {
return FP_VAL;
}
c->used = x;
@ -450,7 +449,9 @@ int fp_mul_d(fp_int *a, fp_digit b, fp_int *c)
c->dp[x] = (fp_digit)w;
w = w >> DIGIT_BIT;
}
if (w != 0 && (a->used != FP_SIZE)) {
if (w != 0) {
if (a->used == FP_SIZE)
return FP_VAL;
c->dp[c->used++] = (fp_digit) w;
++x;
}
@ -460,8 +461,6 @@ int fp_mul_d(fp_int *a, fp_digit b, fp_int *c)
for (; x < oldused && x < FP_SIZE; x++) {
c->dp[x] = 0;
}
if (x == FP_SIZE)
return FP_VAL;
fp_clamp(c);
return FP_OKAY;