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Fix for fast math fp_read_unsigned_bin function to check max and correctly set a->used (is handled in fp_mul_2d).

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This commit is contained in:
David Garske
2017-07-12 16:39:26 -07:00
parent 43260f02f4
commit d559eb0f4f
1 changed files with 17 additions and 6 deletions
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23
wolfcrypt/src/tfm.c
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@@ -1868,9 +1868,22 @@ void fp_montgomery_reduce(fp_int *a, fp_int *m, fp_digit mp)
void fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
{
#if defined(ALT_ECC_SIZE) || defined(HAVE_WOLF_BIGINT)
const word32 maxC = (a->size * sizeof(fp_digit));
#else
const word32 maxC = (FP_SIZE * sizeof(fp_digit));
#endif
/* zero the int */
fp_zero (a);
/* if input b excess max, then truncate */
if (c > 0 && (word32)c > maxC) {
int excess = (c - maxC);
c -= excess;
b += excess;
}
/* If we know the endianness of this architecture, and we're using
32-bit fp_digits, we can optimize this */
#if (defined(LITTLE_ENDIAN_ORDER) || defined(BIG_ENDIAN_ORDER)) && \
@@ -1882,11 +1895,6 @@ void fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
{
unsigned char *pd = (unsigned char *)a->dp;
if ((unsigned)c > (FP_SIZE * sizeof(fp_digit))) {
int excess = c - (FP_SIZE * sizeof(fp_digit));
c -= excess;
b += excess;
}
a->used = (c + sizeof(fp_digit) - 1)/sizeof(fp_digit);
/* read the bytes in */
#ifdef BIG_ENDIAN_ORDER
@@ -1913,7 +1921,10 @@ void fp_read_unsigned_bin(fp_int *a, const unsigned char *b, int c)
for (; c > 0; c--) {
fp_mul_2d (a, 8, a);
a->dp[0] |= *b++;
a->used += 1;
if (a->used == 0) {
a->used = 1;
}
}
#endif
fp_clamp (a);